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Critical Care In Pregnancy (Part 2) V1
23 Plays6 years ago
Caring for critically ill pregnant patients poses a series of unique challenges for the intensivist. In part two of this two-episode series, we discuss critical care in pregnancy with Dr. Stephen Lapinsky. Dr. Lapinsky is a practicing intensivist and professor of medicine at the University of Toronto. He is a member of the editorial board of the journal, Obstetric Medicine, and sits on the steering committee of the North American Society of Obstetric Medicine. Dr. Lapinsky is also the executive of the Women’s Health Network of the ACCP. Today (Part 2) we will cover general conditions that may lead to critical illness in pregnant women.
Additional Resources:
Practice bulletin on Critical Care in Pregnancy from the American College of Obstetrics and Gynecology (ACOG): https://bit.ly/2OtJARU
A comprehensive review on acute respiratory failure in pregnancy: https://bit.ly/2DKzwjl
AHA scientific statement on cardiac arrest in pregnancy: https://bit.ly/2QpGWtK
Recommended
Transcript
Introduction to Critical Matters Podcast
00:00:09
Speaker
Welcome to Critical Matters, a sound critical care podcast covering a broad range of topics related to the practice of intensive care medicine.
00:00:17
Speaker
And now, your host, Dr. Sergio Zanotti.
00:00:23
Speaker
Caring for critically ill pregnant patients poses a unique set of challenges for the intensivist.
00:00:28
Speaker
There is the added stress of more than one life at risk and constant concerns for preventing iatrogenic fetal damage.
00:00:34
Speaker
Pregnant patients have unique physiological changes with important implications for critical care.
00:00:39
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Finally, there are a number of conditions unique to pregnancy that the intensivist might not care for on a regular basis.
00:00:45
Speaker
This is the second part of our two-part podcast on pregnancy and critical care.
Unique Challenges in Pregnant Patients
00:00:51
Speaker
Today, in part two, we will discuss some general conditions not specific to pregnancy that may result in pregnant patients coming to the ICE or developing critically ill.
00:01:02
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Our guest, once again, is Dr. Stephen Lipinski.
00:01:05
Speaker
Dr. Stephen Lipinski is Director of the Intensive Care Unit at Mount Sinai Hospital in Toronto and Professor of Medicine at the University of Toronto.
00:01:13
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He is a practicing intensivist and pulmonologist.
00:01:16
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Dr. Lipinski has a clinical and research interest in critical illness and respiratory disease in the pregnant patient.
Thromboembolic Disease in Pregnancy
00:01:23
Speaker
He is a member of the editorial board of the Journal of Obstetric Medicine, and he sits on the steering committee of the North American Society of Obstetric Medicine and the executive of the Women's Health Network of the American College of Chest Physicians.
00:01:36
Speaker
Other clinical and research interests include mechanical ventilation, continuous renal replacement therapy, and mobile computing in medicine.
00:01:43
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He has authored over 100 peer-reviewed articles and more than 40 book chapters on these topics.
00:01:49
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Stephen, welcome back to Critical Matters.
00:01:52
Speaker
Thanks very much.
00:01:53
Speaker
Thanks for having me.
00:01:55
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So in our first episode, we talked about some of the general considerations on physiological changes and some of the pregnancy-specific or unique diseases that can lead to ICU admission in pregnant patients.
00:02:07
Speaker
Today, I want to cover broader topics or broader, more common diseases that do affect pregnant patients and can lead to critical illness.
00:02:17
Speaker
And I would like to start with thrombin-bolic disease in pregnancy.
00:02:20
Speaker
And specifically, is thrombin-bolic disease something that we see commonly or more commonly in pregnant women and why?
00:02:29
Speaker
Yeah, so definitely a concern in the pregnant patient.
00:02:32
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There's several studies that have tried to look at the actual incidents, but it's very difficult because it depends on how detailed you go into the actual investigative process.
00:02:43
Speaker
But clearly an increased risk in pregnancy, and this is related to changes in coagulation factors, increased coagulation factors, but also local venous stasis because of the obstruction of veins by the uterus and local trauma.
00:02:58
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risk increased in women who are obviously at bed rest and also post-cesarean section.
00:03:03
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And a very common period would be in the postpartum period, more so than during pregnancy, although third trimester would be more common than second trimester, but definitely a concern in the pregnant patient.
00:03:17
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And in terms of a diagnosis, how would you tackle these diagnoses?
00:03:21
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Obviously, some of the
00:03:24
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symptoms of a deep venous thrombosis are common in pregnancy, like swelling and maybe some pain.
00:03:30
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But how would you tackle this diagnostic approach in a pregnant patient?
00:03:37
Speaker
Yes, and definitely common to have some edema in pregnancy, so that's not that useful.
00:03:43
Speaker
So first step should be similar to the non-pregnant patient, and ultrasound of the legs can pick up the presence of a DVT, and if you identify the DVT, the patient is going to need anticoagulation, so avoiding any looking at the chest.
Imaging and Treatment Approaches
00:03:59
Speaker
Problem with the ultrasound is what you need to look at is compression or lack of compression because of a DVT in the vein.
00:04:07
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Using Doppler and changes related to respiration is less helpful because there may be obstruction to the vein purely by the uterus and not due to clot.
00:04:18
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So compression ultrasound is the most value.
00:04:21
Speaker
And then in terms of chest-related investigations looking for pulmonary embolus, there's VQ scanning, ventilation perfusion scanning, and CT angiogram.
00:04:34
Speaker
Both are considered safe in pregnancy.
00:04:37
Speaker
Both have relatively low radiation risk and not a big concern for the fetus.
00:04:42
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But the current guidelines suggest ventilation perfusion scanning as a first line.
00:04:48
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This is because pregnant women are usually healthy otherwise and would have a normal chest x-ray.
00:04:54
Speaker
You know, VQ scan is often not useful in the older person with significant chronic disease.
00:05:01
Speaker
But in the young normal patient, it's useful.
00:05:05
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If the perfusion scan is normal, there's no reason to go on to a ventilation scan so you can reduce the radiation risk.
00:05:14
Speaker
CT angiogram is also quite acceptable.
00:05:17
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There can be issues related to the fact that the high cardiac output may make timing and dye dose a little bit difficult.
00:05:25
Speaker
And there is recently a concern about radiation to the mother's breast.
00:05:31
Speaker
So the biggest radiation concern now is rather than to the fetus,
00:05:35
Speaker
The mother's breasts, which are actively dividing at the time, are at increased risk of later cancer.
00:05:42
Speaker
So this would be the major reason for going for a ventilation perfusion scan as a first line rather than a CT scan, but both are certainly acceptable studies to perform.
00:05:54
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And I think that this is important for our audience because it would probably be something that's different than what we usually do.
00:06:00
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CTA has become kind of the go-to test for most patients
00:06:04
Speaker
who were suspecting pulmonary embolism.
00:06:07
Speaker
But clearly, like you said, in this population otherwise healthy, it can be very effective in giving us answers, but also can minimize the radiation exposure by going in a two-step approach.
00:06:20
Speaker
And if the perfusion is normal, you're done basically from that perspective.
00:06:24
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And I think that's very important for them to remember.
00:06:28
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What about treatment?
00:06:30
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What would be the ideal treatment?
00:06:31
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Obviously, there's always concerns for the fetus.
00:06:34
Speaker
I mean, warfarin being teratogenic is an issue initially.
00:06:38
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But what's the best way to treat patients who have a documented thrombobolic phenomenon with pregnancy?
00:06:46
Speaker
Yeah, so right now the treatment would be a low molecular weight heparin.
00:06:52
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So there's actually now good data on safety of low molecular weight heparin and probably considered as safe, if not safer, than unfractionated heparin infusion.
00:07:03
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So the first step would be low molecular weight heparin.
00:07:07
Speaker
A question may arise about the use of thrombolytic therapy, and this has been used in pregnancy.
00:07:15
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There are several case reports of thrombolytic therapy during pregnancy and immediately postpartum.
00:07:22
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There does not seem to be a concern with drugs causing the placenta or causing fetal effects.
00:07:28
Speaker
The biggest concern would obviously be in the postpartum period and the risk of bleeding.
00:07:34
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And really, I think the issue there is a question for the obstetrician.
00:07:38
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If the uterus is contracting down normally and well, the risk of bleeding from thrombolysis would be very low.
00:07:46
Speaker
On the other hand, if you have an atonic uterus that's not contracting down, there would be significant risk of bleeding.
00:07:53
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So if it does come to a concern for thrombolytic therapy, there's a question to be asked of the obstetrician.
00:08:02
Speaker
But data there is obviously limited to case reports, but there are case reports with very successful outcome.
00:08:09
Speaker
So you were treated
00:08:11
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as you would treat a non-pregnant patient in terms of decision-making and then really in consultation with the obstetrician and peripartum or postpartum PE, evaluate the risk of bleeding and make that decision.
00:08:23
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I think that's very important.
00:08:24
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But like you mentioned, there's not a lot of good data, but we don't have a lot of good data to dictate thrombolytics in non-pregnant patients.
00:08:31
Speaker
So I think it's always something that we're struggling with.
00:08:35
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Yeah, definitely.
00:08:36
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But if it's a life-threatening situation, there certainly may be a role.
00:08:40
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Can we go back a little bit to the initial treatment with low molecular weight heparin?
00:08:45
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And is there any, how do you do it?
00:08:48
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I've read that some people recommend making sure it's weight-based.
00:08:53
Speaker
Other people say, well, you should actually measure anti-10A activity.
00:08:58
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What is your experience, Stephen, with these patients?
00:09:01
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Yeah, it's always a problem, and there are different recommendations.
00:09:07
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We would always get our thrombosis experts involved.
00:09:11
Speaker
The weight-based is certainly an issue, although sometimes if you have a very large woman with a very big weight related to pregnancy, you don't want to go above the sort of maximum doses.
00:09:22
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And in those situations, measuring anti-10A definitely has a role.
00:09:29
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As I say, fortunately, I work in a tertiary care center where I have access to thrombosis experts, and I would leave it to them to make those decisions.
00:09:39
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So going back to the thrombolytic discussion, at least here in the United States, I think there's a growing tendency to use catheter-directed thrombolysis, and we could argue about thrombolysis.
00:09:54
Speaker
right indication or the evidence behind that, but have you seen an increase or any data or case reports on using catheter-directed thrombolysis for pregnant patients with the idea of decreasing the amount of exposure to thrombolytics?
Respiratory Challenges in Pregnancy
00:10:09
Speaker
Yeah, and I'm not aware of any data in pregnancy.
00:10:12
Speaker
I mean, I think that you've got to weigh up.
00:10:14
Speaker
On the one hand, there's a
00:10:17
Speaker
obviously a radiation exposure related to that.
00:10:20
Speaker
And on the other hand, the question arises, are you actually reducing the dose of thrombolytic given?
00:10:28
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So I think there's risks and benefits, but I'm not aware of any data in pregnancy related to that.
00:10:34
Speaker
So still something, obviously, to be studied or to be answered.
00:10:37
Speaker
What about the use of IVC filters?
00:10:39
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Any comments?
00:10:40
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Are there specific indications for pregnancy?
00:10:43
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Would you treat it the same way as a non-pregnant patient?
00:10:45
Speaker
What are your thoughts on that?
00:10:46
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I guess the radiation becomes an issue as well.
00:10:49
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Yeah, so again, not much data.
00:10:52
Speaker
There are some concerns that obviously the radiation is going to be directly in the region of the abdomen, but it has been done.
00:11:01
Speaker
One of the concerns is that there may be dilation of the IVC, so it may be difficult to actually get the filter to apply in the IVC, and there's an increased risk of dislodgement related to labor or changes in IVC size.
00:11:17
Speaker
but it certainly has been reported to be successfully used.
00:11:21
Speaker
But I must say we're using fewer and fewer IVC filters in all patients nowadays.
00:11:27
Speaker
Excellent.
00:11:27
Speaker
So I think that the next topic that I wanted to talk about was acute respiratory failure in pregnancy analysis as an area.
00:11:35
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that you're very passionate about, have a lot of expertise on.
00:11:38
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But why don't we review for the audience, what are some of the relevant physiological changes in the pregnant patient that are important when we're treating with acute respiratory failure?
00:11:51
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Yeah, so I think one major change to keep in mind is just the change to the normal blood gas in pregnancy, which may be confusing in interpretation.
00:12:01
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So the pregnant woman has a compensated respiratory alkalosis with a CO2 level usually in the range of about 28 to 32 millimeters of mercury.
00:12:12
Speaker
And there's also a compensatory decrease in bicarbonate to about 20 millimoles per liter to give a normal pH.
00:12:21
Speaker
So if you were to see a CO2 in the range of 40, which would be normal in the non-pregnant patient, this may be abnormal in pregnancy and would be accompanied by a change in pH.
00:12:32
Speaker
So a CO2 of 40 with a pH of, say, 7.3 would be hypercapnic respiratory failure.
00:12:42
Speaker
In terms of oxygenation, the pregnant woman would normally maintain normal oxygenation and there's no reason for hypoxia during pregnancy.
00:12:51
Speaker
One thing slightly related to bear in mind is that the majority of pregnant women complain of shortness of breath by the third trimester.
00:12:58
Speaker
So about 75% would subjectively feel short of breath and this is something to keep in mind
00:13:05
Speaker
whether this is actually a useful symptom, and also not all shortness of breath is pathological in pregnancy.
00:13:14
Speaker
And one of the things that you had mentioned in the previous episode also was in relation to the decreased functional residual capacity.
00:13:22
Speaker
And you mentioned right now that patients are able to maintain a normal oxygen saturation, but their response or their reserve is
00:13:33
Speaker
to apnea or other drugs might be very limited and they're very prone to developing hypoxia.
00:13:39
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How do you integrate that into your management?
00:13:44
Speaker
Yeah, so definitely there's a risk, as you mentioned, because the functional residual capacity is reduced, there's less reservoir of oxygen in the lungs and the pregnant woman is using oxygen much more rapidly, so up to 30 percent higher oxygen consumption.
00:14:00
Speaker
So if you make the pregnant woman apneic for intubation, for example, paralyzing her, she's going to desaturate much more rapidly than the non-pregnant patient.
00:14:10
Speaker
This would be in the normal situation.
00:14:12
Speaker
But if they've got ARDS, they're going to desaturate even more quickly.
00:14:16
Speaker
So that's going to put a lot of pressure on the intubation.
00:14:20
Speaker
I generally, when I intubate, all patients pregnant or otherwise, I like to keep them breathing.
00:14:25
Speaker
I'm not in favor of inducing apnea.
00:14:28
Speaker
I find if they're breathing, I've got a lot more time.
00:14:30
Speaker
There's a lot less pressure and things go much more smoothly, but particularly in the pregnant patient.
00:14:37
Speaker
And we did talk about this compensated respiratory alkalosis or alkalosis in terms of pH changes.
00:14:46
Speaker
And I guess when we talk about mechanization, we can dive into this a little bit more.
00:14:48
Speaker
But if you were to...
00:14:51
Speaker
hyperventilate and make a pregnant woman even more alkalotic or alkalemic, what's the effect it has on the fetus or on the uterus?
00:15:01
Speaker
Yeah, so the alkalosis is bad for the fetus.
00:15:04
Speaker
Alkalosis is going to constrict uterine blood vessels and reduce blood flow to the uterus and the placenta.
00:15:12
Speaker
And the net effect is to cause fetal hypoxia, so the fetus is going to get less oxygen.
00:15:18
Speaker
So, for example, in the intubation phase, you're not going to want to hyperventilate the pregnant woman to try and oxygenate her adequately.
00:15:26
Speaker
You want to pre-oxygenate her with a high FO2, but not get her to over-breathe because that's potentially harmful to the fetus.
00:15:34
Speaker
Similarly to the reason why in labor, women are taught not to over-breathe, but to control their breathing, because that alkalosis is potentially harmful to the fetus.
00:15:46
Speaker
So what are some of the major causes of respiratory failure in pregnancy that you think are relevant for the intensivist to keep in mind?
00:15:54
Speaker
So we mentioned in the last episode pregnancy-specific conditions such as preeclampsia with pulmonary edema, and that's probably one of the most common causes for admission to the ICU through respiratory failure.
00:16:08
Speaker
Other pregnancy-specific conditions such as amniotic fluid embolism are much less common.
00:16:14
Speaker
Depending on the time of the year and the actual influenza season, flu influenza with a pneumonitis is not uncommon cause.
00:16:26
Speaker
In 2008, 2009, we had a lot of pregnant women with influenza pneumonitis and ARDS.
00:16:34
Speaker
Other conditions would be just conventional pneumonia.
00:16:38
Speaker
And also asthma.
00:16:39
Speaker
Asthma is obviously a very common condition affecting 5 to 10 percent of the population.
00:16:44
Speaker
About a third of women with asthma are going to have a deterioration.
00:16:48
Speaker
And although respiratory failure from asthma is not uncommon, it is something that you definitely can see in pregnancy.
Managing Asthma and Pulmonary Edema
00:16:56
Speaker
And in terms of patients who are asthmatic and become pregnant,
00:17:02
Speaker
I guess, I mean, there's a percentage that can get worse, a percentage that have no difference.
00:17:07
Speaker
But when you treat a patient with a status as medical who's pregnant, is there anything that we would do differently?
00:17:16
Speaker
No.
00:17:17
Speaker
So really the most important thing is to give all the drugs you would normally give.
00:17:21
Speaker
So definitely don't avoid the steroids that you would give to the non-pregnant patient.
00:17:26
Speaker
Give all the inhalers you would give and manage them really identically.
00:17:31
Speaker
Can we talk a little bit about pulmonary edema?
00:17:33
Speaker
You did mention some of the causes that are pregnancy-specific, but I think in the pregnant patient, other than preeclampsia, there's other very interesting reasons why they might develop pulmonary edema.
00:17:46
Speaker
So in terms of pregnancy-related conditions, so we mentioned the amniotic fluid embolism.
00:17:54
Speaker
The other complications like HELP syndrome and acute fatty liver of pregnancy can sometimes be associated with
00:18:00
Speaker
development of ARDS.
00:18:03
Speaker
Placental abruption can cause ARDS and massive hemorrhage with massive transfusion puts the woman at risk of transfusion related acute lung injury.
00:18:16
Speaker
Outside of the pregnancy related conditions, aspiration.
00:18:21
Speaker
So acid aspiration or Mendelsohn syndrome is not really a pregnancy specific condition but much more common in pregnancy because the stomach
00:18:31
Speaker
empties incompletely and there's a high pressure in the abdomen.
00:18:35
Speaker
So it puts the pregnant woman at significant risk of aspiration and development of pulmonary edema.
00:18:42
Speaker
It does seem as if pregnant women are predisposed to develop ARDS.
00:18:46
Speaker
They develop ARDS more easily than the non-pregnant population.
00:18:50
Speaker
And this may be because pregnancy or delivery produces some kind of inflammatory environment in the lung acting as a first hit and the sort of second hit of the aspiration or the pneumonia stimulates ARDS much more easily than in the non-pregnant patient.
00:19:08
Speaker
So I think that this would be a good lead-in, Stephen, to talk a little bit about supportive care in terms of respiratory support.
00:19:14
Speaker
And we would start with intubation.
00:19:17
Speaker
You made some points on intubation.
00:19:19
Speaker
But also, I think an important aspect that I would like to hear your comments on are it's not uncommon to patients who are pregnant to have edema in their airways.
00:19:30
Speaker
And you did mention the risk of aspiration.
00:19:32
Speaker
What are some of the precautions that you would take as you're getting ready to intubate a patient?
00:19:38
Speaker
Yeah, so we've mentioned the edema, the anatomical changes, and remembering that preeclampsia can actually aggravate the edema.
00:19:48
Speaker
Just the state of labor and delivery can actually worsen the airway.
00:19:53
Speaker
So there are studies that have looked at Malampati's score before and after labor and actually shown a change that there's significant edema and change during actual labor and delivery.
00:20:07
Speaker
Also with some women, if there's enlarged breast related to pregnancy, it can be difficult to get the laryngoscope into the mouth and there you'd need to have access to a stubby handle.
00:20:18
Speaker
So I think the most important precaution to take is to have the most expert person available during the intubation.
00:20:27
Speaker
In my sort of tertiary care setting, we have obstetric anesthetists, and if possible, we would want them involved because this is what they do every day.
00:20:36
Speaker
They're used to the difficult airway.
00:20:38
Speaker
They're used to the rapid oxygen desaturation, and this is their life.
00:20:42
Speaker
But in the absence of that, as good pre-oxygenation as you can, have all your equipment available.
00:20:49
Speaker
And as I said, I prefer to do a non-apneic intubation, keep the patient breathing.
00:20:56
Speaker
It takes a lot of time pressure off you.
00:21:00
Speaker
Also, avoid
Ventilation Strategies for Pregnant Patients
00:21:01
Speaker
the nose.
00:21:01
Speaker
So any tubes going in the nose, endotracheal intubation by the nose or a
00:21:06
Speaker
nasogastric tube very commonly will cause an epistaxis just because of the mucosal edema and friability.
00:21:14
Speaker
Do you normally downsize your ET tube in a pregnant patient?
00:21:19
Speaker
Yeah, so definitely have a smaller size tube available and go half a size or a size smaller than you would normally use for that size patient.
00:21:27
Speaker
So I think these are all important, I mean, tips and precautions as we make that decision to intubate.
00:21:32
Speaker
But what about the use of non-invasive ventilation?
00:21:35
Speaker
Obviously, you did talk about the increased risk of aspiration.
00:21:39
Speaker
That would be a concern, I guess, in somebody who has a tight mask.
00:21:42
Speaker
But what is the role?
00:21:44
Speaker
And I'm sure it's not been studied, but how do you see non-invasive ventilation in pregnant patients' respiratory failure?
00:21:50
Speaker
Yeah, so the initial sort of thought would be a concern that these are patients with a full stomach.
00:21:55
Speaker
Are they going to vomit and aspirate?
00:21:58
Speaker
Also, if you're thinking about using nasal-type masks, as you would in the chronic patient, they often got a blocked nose.
00:22:05
Speaker
On the other hand, many of the causes of respiratory failure in pregnancy are pretty transient.
00:22:10
Speaker
Pulmonary edema related to preeclampsia may go away with a dose of Lasix and a little bit of support.
00:22:17
Speaker
A patient with pulmonary edema relates to cardiac disease similarly.
00:22:22
Speaker
So there is a benefit of a short-term support with non-invasive and also avoiding the whole intubation procedure.
00:22:32
Speaker
So there actually is very little data.
00:22:34
Speaker
There's a case series by colleague of mine, Josh A. Rojas Suarez, recently in the literature.
00:22:41
Speaker
And we've done it quite a lot, particularly in patients with chronic lung disease, so neuromuscular disease or kyphoscoliosis.
00:22:50
Speaker
And it works very well.
00:22:51
Speaker
You just need a patient who's awake and alert and protecting the airway, so you're not going to do it in someone whose level of consciousness is down.
00:22:59
Speaker
And it provides very good support in the short term to get someone over pulmonary edema or through, for example, laban delivery, someone with limited respiratory reserve from neuromuscular disease or kyphoscoliosis, that extra support can get them through the laban delivery without the need for intubation.
00:23:20
Speaker
So I think there definitely is a role if you have experience with non-invasive and you're choosing patients who are awake and alert and
00:23:28
Speaker
able to protect the airway.
00:23:31
Speaker
So I think those are important points.
00:23:33
Speaker
And in terms of recapping, make sure that the patients are wide awake and able to protect their airway.
00:23:38
Speaker
But especially, it seems that in instances where you think that you can reverse the respiratory failure in a short period of time, it might be an option that prevents intubation and other potential complications.
00:23:52
Speaker
So something to keep in mind.
00:23:54
Speaker
What about a
00:23:55
Speaker
conventional mechanical ventilation, especially, I mean, when we think about it in terms of ARDS, what are the particular aspects that you think are unique to pregnancy or things that we should pay attention to?
00:24:09
Speaker
Yeah, so this is a very understudied area as well.
00:24:13
Speaker
And I think as a general rule, you should be doing what you would do in your non-pregnant patient.
00:24:19
Speaker
But a number of issues do arise.
00:24:22
Speaker
Firstly, tidal volume.
00:24:24
Speaker
Do we aim for 6 mL per kilogram?
00:24:27
Speaker
We do know that in pregnancy, the pregnant patient takes tidal volumes that are 40% bigger than the non-pregnant patient.
00:24:34
Speaker
to achieve that low CO2.
00:24:37
Speaker
So should we be emulating that?
00:24:40
Speaker
I don't think there's any data to support a higher tidal volume, so I would still go with the 6 mL per kilogram.
00:24:47
Speaker
But the question of whether to aim for 30 mmHg.
00:24:52
Speaker
Anyone who's managed a patient with ARDS knows that it's difficult to keep a normal CO2, and we often let the CO2 rise.
00:25:00
Speaker
And I think that's quite reasonable in pregnancy.
00:25:03
Speaker
A low CO2 is obviously to be avoided.
00:25:05
Speaker
As you mentioned earlier, it's going to reduce uterine and placental blood flow.
00:25:11
Speaker
There are very limited data on hypercapnia in pregnancy, but some small studies where they've allowed the CO2 to rise to the 40s or 50s,
00:25:22
Speaker
with no significant problems for the fetus.
00:25:25
Speaker
There's a case series from New York State somewhere, a bunch of women with severe asthma where the CO2s got into the hundreds with good fetal outcome.
00:25:39
Speaker
So my feeling, but not really supported by much data, is that the pregnant woman probably tolerates very mild hypercapnia, and I would tend to allow that to happen.
00:25:51
Speaker
In terms of modes of ventilation, there's no really good literature to suggest one mode over another.
00:25:59
Speaker
And we would just do what we would normally do with adequate PEEP and ensuring that we're not allowing basal atelectasis with the enlarged uterus.
00:26:11
Speaker
I have read some comments that the chest pressures or the chest compliance obviously changes with pregnancy and some thoughts about should the plateau pressures be targeted at 30 and the peeps at maybe 5 at the beginning or should because of these changes are pregnant women perhaps benefited by higher plateau pressures or higher peeps?
00:26:35
Speaker
Any comments on this?
00:26:38
Speaker
Yeah, so the enlarged uterus and the diaphragms that are elevated are going to affect your whole respiratory system compliance.
00:26:46
Speaker
So the respiratory system compliance is going to be reduced.
00:26:50
Speaker
So for the same tidal volume, you're going to have slightly higher
00:26:54
Speaker
plateau pressures.
00:26:56
Speaker
So in theory, it does make sense to allow the plateau pressures to rise a little.
00:27:01
Speaker
I'm just not sure how much and if you're letting it rise a little, maybe you'll let it rise a lot.
Advanced Support and Emergency Management
00:27:08
Speaker
Ideally, you'd want, for example, an esophageal balloon monitoring may be helpful, but I'm really not aware of any data doing that in pregnancy and whether there are complications related to that.
00:27:21
Speaker
Just some of these series of severe ARDS, one series I recall from
00:27:28
Speaker
Winnipeg in Canada during the 2008 H1N1 flu epidemic.
00:27:35
Speaker
They had a significant incidence of pneumothorax in their patients, and it makes me wonder whether they were a little bit relaxed in allowing the plateau pressures to rise, resulting in pneumothorax.
00:27:46
Speaker
But slightly higher plateau pressures are likely going to happen.
00:27:50
Speaker
I just wouldn't let it go too high.
00:27:54
Speaker
And I think that that's an important concept.
00:27:56
Speaker
And like you mentioned, we don't have a lot of specific studies, so it's very hard sometimes to apply what we do in other patients to pregnant patients.
00:28:05
Speaker
But
00:28:06
Speaker
I guess an underwriting objective should always be to do what we would do for somebody who's not pregnant and provide the best care possible for the mother.
00:28:15
Speaker
What about any comments, and I know that data is not going to be abundant here, on non-conventional support.
00:28:21
Speaker
So let's say we do small tidal volumes, we provide good support with a ventilator, but we're still having issues.
00:28:28
Speaker
What about as we escalate that ladder of neuromuscular blockade, prone positioning,
00:28:34
Speaker
other modes of ventilation, and even ECMO.
00:28:37
Speaker
Any comments on what the experience is with pregnant patients?
00:28:41
Speaker
Yeah, so I think neuromuscular blockade, in the short term there is some data, and the neuromuscular blockers do cross the placenta, but at a relatively low rate.
00:28:52
Speaker
So the fetal exposure would be about 15 to 20 percent for most of the drugs.
00:29:01
Speaker
And the biggest concern there is if the fetus were to deliver while the mother's paralyzed, the neonatologist needs to be aware of that because the fetus may well need intubation until the paralytic wears off.
00:29:14
Speaker
There's very little data on prolonged paralysis and there is a concern whether this is harmful to the fetus or if the fetus is not moving for a period of time.
00:29:24
Speaker
Prone positioning is obviously the next sort of well evidenced but it's supported intervention.
00:29:30
Speaker
I personally have not proned a pregnant patient but have spoken to people who've done it and they're
00:29:36
Speaker
are reports.
00:29:37
Speaker
And there's, in fact, one report that looked at blood flow, fetal blood flow and placental blood flow with the pregnant woman in the prone position.
00:29:46
Speaker
And if anything, the prone position is beneficial in terms of uterine, placental and fetal blood flow.
00:29:53
Speaker
So no harm to the fetus.
00:29:55
Speaker
I think just
00:29:56
Speaker
The only harm would be to your relationship with ICU nurses when you ask them to turn over the pregnant patient.
00:30:02
Speaker
It would take a lot of chocolates to fix that problem.
00:30:05
Speaker
No, absolutely.
00:30:09
Speaker
Other non-conventional, so nitric oxide, our case reports using it, particularly in women with pulmonary hypertension, and the effect of the nitric oxide is very short and shouldn't have any effect on the fetus.
00:30:23
Speaker
High frequency oscillation is pretty much out of vogue at the moment, although we still use it in our ICU and we have used it on pregnant women quite successfully.
00:30:32
Speaker
And during the 2008-2009 H1N1 epidemic, there were several case series from the United States and from Australia using ECMO in pregnancy with actually very good outcome for mother and fetus.
Cardiovascular Changes and Arrest Management
00:30:47
Speaker
So that's definitely an option as well.
00:30:50
Speaker
Excellent.
00:30:50
Speaker
So I think that in terms of our next topic, talk a little bit about cardiovascular support now and shock and pregnancy and dive a little bit into also cardiac arrest.
00:31:01
Speaker
But again, I think that it would be a good starting point, Stephen, if we could just refresh the audience on what are the significant cardiovascular physiological changes in pregnancy that might have an implication where we're dealing with shock or cardiac arrest?
00:31:14
Speaker
So the main effect is the increased cardiac output associated with peripheral vasodilatation.
00:31:21
Speaker
So there's an increased cardiac output, not much change in blood pressure, and also an increase in blood volume.
00:31:33
Speaker
shock in pregnancy, the major concern is perfusion of the fetus.
00:31:38
Speaker
And the sort of physiology of the mother is such that it does not protect the fetus.
00:31:43
Speaker
So when the mother drops her blood pressure, her normal physiology is to protect her brain and protect her heart, and the fetus is not protected.
00:31:53
Speaker
the mother producing endogenous catecholamines or our exogenous vasopressor infusions are all going to reduce uterine blood flow and be potentially harmful to the fetus.
00:32:07
Speaker
So that's something to be borne in mind, but just remember that a live mother is obviously better for the fetus than a dead mother, so whatever you need to do for the mother is going to be beneficial to the fetus.
00:32:21
Speaker
What are the immediate interventions that you should take as soon as you see a woman who's pregnant who's either dropping her blood pressure or going into shock?
00:32:33
Speaker
So, important thing to keep in mind is the supine hypotension syndrome.
00:32:38
Speaker
So, the effect of the enlarged uterus on the inferior vena cava, reducing venous return.
00:32:46
Speaker
So, either tilting the mother into a left lateral position to get the uterus off the IVC or manually displacing the uterus off the IVC.
00:32:56
Speaker
So, that can be helpful.
00:32:57
Speaker
And then fluid resuscitation before starting vasopressor therapy.
00:33:04
Speaker
Now, in terms of differential diagnosis, when you see a pregnant patient whose shock, I presume it's similar to what you see in non-pregnant patients, but can you comment on some of the more frequent causes of shock and maybe even cardiac arrest in pregnancy?
00:33:19
Speaker
Yeah.
00:33:21
Speaker
Yeah, so obviously very similar, but in pregnancy you need to worry about hemorrhage much more than in your non-pregnant patient because hemorrhage can happen out of the blue and without being easily noticed.
00:33:35
Speaker
You need to worry about some of the pregnancy-specific conditions, particularly amniotic fluid embolism, preeclampsia, and also think about pulmonary embolism.
00:33:45
Speaker
Then pregnant women are at risk of sepsis.
00:33:49
Speaker
And that's obviously an important cause.
00:33:52
Speaker
And then cardiogenic causes, so the woman with pre-existing cardiac disease or the development of peripartum cardiomyopathy, which could cause shock.
00:34:03
Speaker
So a number of causes to keep in mind, but a sort of general approach should identify most of them.
00:34:11
Speaker
And once a patient has a cardiac arrest, what?
00:34:15
Speaker
You talked about the supine hypotension syndrome, but once they have a cardiac arrest, things all of a sudden change.
00:34:21
Speaker
So why don't we talk about managing cardiac arrest in pregnant patients?
00:34:25
Speaker
And as you mentioned in the previous episode, that becomes a very chaotic situation.
00:34:29
Speaker
So I would
00:34:31
Speaker
emphasize, like you mentioned before, that the first thing is to make sure that somebody is in charge and assigning tasks and clearly vocalizing what needs to be done.
00:34:40
Speaker
But talk about what are the specific things that you would worry about in terms of cardiac arrest with the basic life support first.
00:34:48
Speaker
Yeah, so as you mentioned earlier, the pregnant woman is at risk of oxygen desaturation quite rapidly because of the lack of a
00:34:56
Speaker
an oxygen reserve and the rapid consumption of oxygen.
00:35:00
Speaker
So although most of our cardiac arrest protocols highlight the compressions first and then worry about the airway, if it's a woman who's in hospital with a cardiac arrest and any concern about oxygenation, for example, with pneumonia or aspiration or even a
00:35:18
Speaker
narcotic excess or a high spinal block, you really need to think about the oxygenation.
00:35:24
Speaker
It really doesn't help to be circulating deoxygenated blood with your CPR.
00:35:29
Speaker
So think about oxygenation and because they desaturate rapidly, you may want to deal with the airway and the oxygenation early on.
00:35:37
Speaker
In terms of the compressions, this should be no different to the non-pregnant patient.
00:35:43
Speaker
Earlier guidelines have suggested tilting the patient into the left lateral position, but there's data that compressions are really ineffective if the woman is left laterally tilted.
00:35:55
Speaker
So you would keep her supine and have an additional person pulling the uterus to the left to get it off the IVC while you're doing compressions in the supine position.
00:36:07
Speaker
In terms of defibrillation, really no change.
00:36:10
Speaker
There's no risk to the fetus and defibrillate and no change to drug therapy.
00:36:15
Speaker
The only proviso is try not to give drugs via femoral access or a foot access because these may be obstructed by the uterus.
00:36:26
Speaker
So giving them above the diaphragm a central line or an arm IV access to make sure that they're getting in.
00:36:35
Speaker
In terms of, can you expand a little bit more on that left uterine displacement technique?
00:36:40
Speaker
Because I think that's something that a lot of people have not probably experienced.
00:36:44
Speaker
And it's important since you talked about maximal effectiveness of the compressions are in the supine position, and we have to keep them in that position.
00:36:54
Speaker
So supine position and someone basically pulling or pushing the uterus,
00:36:59
Speaker
to the left side to get it off the IVC.
00:37:03
Speaker
And important not to be pushing it downwards but preferably trying to lift the uterus up and to the left to reduce the pressure on the inferior vena cava.
00:37:11
Speaker
So I think that that's an important task that the intensivist as leader will have to assign a specific person to do in terms of at all times they are displacing that uterus like you said to make sure that we're improving circulation.
00:37:28
Speaker
Yeah, definitely.
00:37:28
Speaker
And as you said, there are usually a lot of people in the room all doing something.
00:37:33
Speaker
So that's definitely a role to give to someone.
00:37:37
Speaker
So in terms of defibrillation, no different.
00:37:40
Speaker
In terms of drugs, no different.
00:37:42
Speaker
We would use epinephrine probably.
00:37:45
Speaker
We would use, in the cases of ventricular fibrillation or ventricular tachycardia, we would use amiodarone at the same doses once.
00:37:53
Speaker
We've shocked them, no difference there.
00:37:56
Speaker
What about this whole concept of the perimortem cesarean delivery?
00:38:00
Speaker
And I think this is an important aspect of pregnancy and something that obviously we wouldn't be doing, but we have to be thinking.
00:38:08
Speaker
And I would like to start by describing what it is, why we should be doing or thinking about it, and then talk about the timing, the place, and the person.
00:38:19
Speaker
Yeah, so essentially this is just very urgent delivery, which done by a trained obstetrician can be done within about one minute.
00:38:30
Speaker
And the benefit is not only for the fetus, so you're not doing a caesarean section to save the dying fetus, but you're also benefiting the mother, and some would term it a resuscitative hysterotomy, that by...
00:38:42
Speaker
opening the uterus and taking this big weight out of the uterus on the IVC, and also allowing the uterus to contract down, which is returning blood to the central circulation, there can be a significant benefit to the mother.
00:38:57
Speaker
And there's increasing data to support this.
00:39:01
Speaker
Now, the usual timing described is the four-minute rule.
00:39:07
Speaker
that if you've got no return of circulation within four minutes, the perimortem caesarean section should be initiated with the idea of delivering at five minutes.
00:39:19
Speaker
But there is a study from 2016 that actually, a systematic review that looked at a large number of cases and case series of perimortem caesarean section and showed that there was essentially a linear
00:39:36
Speaker
loss of outcome related to time, so outcome for mother and baby.
00:39:42
Speaker
So at four minutes, you're really getting the optimal outcome.
00:39:45
Speaker
But if it's 10 minutes or if it's 15 minutes after the arrest onset, it's still not hopeless, and it's still worthwhile doing the caesarean section because you may still improve the mother and the baby's outcome.
00:39:58
Speaker
So timing is, you know, variable.
00:40:01
Speaker
If you don't know the time, if it's an unwitnessed arrest or no one's been keeping time, then it's appropriate to go ahead and do it right away.
00:40:09
Speaker
And I think the other extreme would be in somebody who, as intensive as we believe, there's no chance of survival for the mother, doing it earlier to try to save the fetus would also make sense at that point, right?
00:40:22
Speaker
Yeah, so if it's an obviously non-survival mother, and the example they would give is a road traffic accident with a major head injury, you know, doing the C-section immediately.
00:40:31
Speaker
Another principle that's been sort of described is that the mother shouldn't be moved for the C-section.
00:40:37
Speaker
So if it's in hospital, don't move her to the operating room.
00:40:41
Speaker
do it where you are.
00:40:42
Speaker
But taking that to an extreme in some European countries, I know the Netherlands, the United Kingdom, they're actually teaching paramedics in simulation scenarios to do the caesarean section, you know, at the roadside or wherever that happens.
00:40:58
Speaker
There's a systematic review by Sharon Ainer from Jerusalem who looked at a whole bunch of cases over 30 years.
00:41:07
Speaker
and identified that about a third of the women actually benefit from the perimortem caesarean section, and they could not identify actual harm done in any caesarean section.
00:41:18
Speaker
So there's no caesarean section where there was a feeling that there was harm done to the mother.
00:41:23
Speaker
So it's always something to keep in mind and to do.
00:41:28
Speaker
And if the patient survives and has return to circulation, obviously, like in other cardiac arrests, there's a set of things that we do for post-cardiac arrest care.
00:41:36
Speaker
I think an important distinction here would be that there are some patients who will remain pregnant while post-arrest.
00:41:44
Speaker
And that's another story in terms of fetal monitoring and what we do.
00:41:47
Speaker
But in terms of specific items for the post-arrest care, hypothermia, for example, any comments, Stephen, on what is different or what we should be thinking in the pregnant patients?
00:41:58
Speaker
Yeah, that's an easy comment.
00:41:59
Speaker
We have no idea.
00:42:02
Speaker
So really no data, but a few theoretical issues.
00:42:05
Speaker
So often these women would be bleeding and generally would avoid hypothermia in a patient at risk of bleeding, but we really have no data on post-arrest care.
00:42:17
Speaker
We really don't know what to do.
00:42:18
Speaker
So I think we would do what we normally do, although avoid the hypothermia if there's a significant postpartum hemorrhage.
00:42:27
Speaker
And then just provide the best care as possible.
00:42:29
Speaker
And one of the things that I've seen in guidelines that will be attached to the show notes is that during acute situations with cardiac arrest, fetal monitoring probably is not something a priority.
00:42:41
Speaker
But once we have returns with antirculation, if the patient is still pregnant, obviously fetal monitoring and involving the rest of the team in that aspect is going to become important.
00:42:54
Speaker
Yeah, definitely.
00:42:55
Speaker
In terms of outcome of women post-cardiac arrest, there are two studies that have looked at this.
00:43:01
Speaker
One was a systematic review and the other was a United Kingdom prospective cohort and both came out with very similar numbers of about 58% survival.
00:43:14
Speaker
So, very good survival compared to the non-pregnant patient.
00:43:18
Speaker
So that's something to keep in mind that the expectation is that the mother is going to survive the cardiac arrest.
Career Insights and Conclusion
00:43:24
Speaker
Excellent.
00:43:25
Speaker
Any other comments, I mean, on any of these topics that we discussed as we close this episode, Stephen?
00:43:34
Speaker
No, I think just similar to what we said last time, if you in doubt manage the patient as you would the non-pregnant patient, you're likely going to provide optimal care in that way.
00:43:44
Speaker
Excellent.
00:43:45
Speaker
So we'd like to close our podcast with just some general questions.
00:43:49
Speaker
I mean, trying to tap into the wisdom of our guests and talk about things that are not necessarily related to critical care in pregnancy, but might be related to the practice in general of critical care.
00:44:01
Speaker
Would that be okay?
00:44:04
Speaker
Sure.
00:44:04
Speaker
Yeah.
00:44:05
Speaker
What do you believe to be true in medicine or in life that most other people don't believe?
00:44:12
Speaker
Yeah, so that's a good question.
00:44:14
Speaker
I don't know about most people don't believe, but something that I believe because I'm really, really old and I've been around a long time is that things change and everything is like a pendulum.
00:44:25
Speaker
What we believe today is going to be different in five years' time and then we'll be back to it in 10 years' time.
00:44:33
Speaker
So don't get too excited or hung up by facts.
00:44:37
Speaker
Things change over time.
00:44:39
Speaker
And I think it's great advice when I see physicians arguing among each other, different specialties.
00:44:46
Speaker
People tend to become very dogmatic sometimes in those situations.
00:44:49
Speaker
And I think that ultimately the lesson really is that whatever you believe to be true today might not be tomorrow.
00:44:55
Speaker
So keep an open mind and embrace change.
00:44:58
Speaker
That's great advice.
00:45:01
Speaker
The second question, Stephen, last question would be, what would you want every intensivist who listened to our podcast to know?
00:45:10
Speaker
Could be a quote, a fact, or just a message for them.
00:45:16
Speaker
I think the biggest message and something I try and train our ICU fellows is just the concept of situational awareness and being aware of the bigger picture of what's going on
00:45:28
Speaker
and avoid tunnel vision.
00:45:30
Speaker
So we spoke about cardiac arrest.
00:45:32
Speaker
When I go to a cardiac arrest in my hospital, I often get asked afterwards, why didn't I help out?
00:45:37
Speaker
I was just standing in the back of the room.
00:45:40
Speaker
And just standing in the back of the room and watching can be very helpful.
00:45:43
Speaker
And sometimes the team leader needs to step back and look what's happening.
00:45:48
Speaker
And examples of things that I've helped out at arrests, I remember once there was a young nurse standing near me holding a big paper bag and eventually I asked her, what's that?
00:45:58
Speaker
And she said, oh, that's the blood they ordered.
00:46:00
Speaker
But she was too junior and shy to shout out, I've got the blood.
00:46:04
Speaker
So I shouted out, the blood's here and everyone jumped there waiting for the blood.
00:46:09
Speaker
So that's useful.
00:46:10
Speaker
I remember another cardiac arrest where just because I was standing back, I could see that the recently inserted triple lumen line had one port not used and not kept, and it was dripping on the floor.
00:46:23
Speaker
And some of the staff at the side of the arrest were actually trying to step around the puddle of blood, but no one had actually done anything about it.
00:46:31
Speaker
So, big picture of just keeping an awareness of what's going on.
00:46:35
Speaker
Don't get too tunnel vision or focused on one aspect of management in all acute management and resuscitation situations.
00:46:44
Speaker
I think that's great advice.
00:46:45
Speaker
And I think with a tunnel vision also, what happens a lot of times is we stop going over basic steps, right?
00:46:52
Speaker
We become very focused on whatever we're trying to do that we're not aware of other things that are going on around or other possibilities of things that we could be doing that could be life-saving.
00:47:02
Speaker
And I think that's something that we need to work around.
00:47:04
Speaker
But
00:47:05
Speaker
Like you mentioned, we need to step up and become leaders in these arrests and be able to help the team with specific tasks, I think, is a big, big, big role for us.
00:47:14
Speaker
Yeah, and another area is the whole intubation scenario.
00:47:19
Speaker
And most intubation catastrophes are related to that tunnel vision issue.
00:47:25
Speaker
Absolutely.
00:47:26
Speaker
Well, it's been a great pleasure to talk with you about these pregnancy-related topics.
00:47:31
Speaker
I know that the wealth of knowledge you have in this area from an intensive standpoint is phenomenal.
00:47:38
Speaker
I really appreciate your willingness to share that wealth of knowledge with our audience and be so generous with your time.
00:47:44
Speaker
Hopefully, we'll have you back on the show in the future.
00:47:48
Speaker
And again, Stephen, many, many thanks for being a guest on Critical Matters.
00:47:54
Speaker
Okay, well, thanks very much for asking me to do this.
00:48:00
Speaker
Thanks again for listening to Critical Matters.
00:48:02
Speaker
Make sure to subscribe to this podcast on iTunes or Google Play.