Transcript
Speaker: Welcome to Critical Matters, a sound podcast covering a broad range of topics related to the practice of intensive care medicine.
Speaker: Sound provides comprehensive critical care programs to hospitals across the country.
Speaker: To learn more about our programs and career opportunities, visit www.soundphysicians.com.
Speaker: And now your host, Dr. Sergio Zanotti.
Speaker: In a previous episode of Critical Matters, we discussed the concept of brain death, death by neurologic criteria, through the lens of the World Brain Death Project.
Speaker: In today's episode, we will return to this topic and focus our discussion on the recently published American Academy of Neurology, American Academy of Pediatrics, Child Neurology Society, and Society of Critical Care Medicine clinical guidelines for the evaluation of brain death and death by neurologic criteria.
Speaker: Our guest is Dr. David Greer.
Speaker: Dr. Greer is a neurologist with additional vascular neurology and neurocritical care training.
Speaker: He is the chair of the Department of Neurology at the Boston University School of Medicine.
Speaker: Dr. Greer is a renowned clinician, educator, and researcher.
Speaker: His research interests include predicting recovery from coma after cardiac arrest, brain death, and multiple stroke-related topics.
Speaker: Dr. Greer is a leader in the Neurocritical Care Society, Society of Critical Care Medicine, and the American Stroke Association.
Speaker: He has an extensive list of publications and awards.
Speaker: He is the first author of the Pediatric and Adult Brain Death, Death by Neurologic Criteria Consensus Guideline we will discuss today.
Speaker: Dave, welcome back to Critical Matters.
Speaker: Thank you, Sergio.
Speaker: It's great to be here.
Speaker: So as you were discussing before we started recording, there's a new combined adult and pediatric clinical guideline that just got published by multiple societies.
Speaker: You're the first author of that.
Speaker: A very important topic, the topic of brain death and death neurologic criteria.
Speaker: Today we're going to focus on the adult patient just because that is our main focus on the podcast.
Speaker: But I guess where appropriate if you want to just highlight some of the importances or differences, since this is a combined document, that would be great.
Speaker: But I wanted to start as a way of introduction with just some terminology.
Speaker: And if you could really just give us your thoughts and how the guideline group thought of brain death, death analogy criteria, the word irreversible and the word permanence.
Speaker: Sure.
Speaker: So it's a great question.
Speaker: I'll take the first part first.
Speaker: So brain death, quote unquote, is what has been used colloquially for decades now.
Speaker: And I think it's the term that most people are familiar with and certainly the lay public is familiar with.
Speaker: But death by neurologic criteria is a more accurate term.
Speaker: term to be used.
Speaker: It means that we are determining that someone is dead based on criteria that are brain-based and not cardiopulmonary-based as the prior definitions of death were.
Speaker: So rather than trying to choose one versus the other and upset one group versus another, we decided to include both
Speaker: and call it BD slash DNC, grain death slash determination death by neurological criteria.
Speaker: That kind of captures both feelings.
Speaker: In terms of the use of the word permanent instead of irreversible, the panel chose to use the term permanent to mean that function was lost and, number one, would not resume spontaneously, and, number two, medical interventions would not be used to attempt to restore function so that you could have a patient who has, for example, a very severe cerebral edema
Speaker: due to a massive ischemic stroke, you wouldn't do a hemicraniectomy on that patient if you felt that the prognosis was futile.
Speaker: And so that takes away the possibility that a surgical or medical intervention would reverse the condition.
Speaker: So that's why we use the term permanent to establish that difference.
Speaker: Perfect.
Speaker: And in terms of these new guidelines, one of the things I immediately noticed is that it's a combined adult and pediatric.
Speaker: But could you just comment on general terms, some of your impressions of the guidelines and why they're so important for intensivists to be aware of?
Speaker: Sure.
Speaker: So just to remind the listeners that we had two separate sets of guidelines for adult and pediatrics previously.
Speaker: The AAN, or American Academy of Neurology, guidelines for adults came out in 2010, and the AAP, or American Association of Pediatrics, along with SCCM,
Speaker: and the Child Neurology Society had their guidelines in 2011 and for the most part they were quite similar but there were some notable differences for mostly subtle things like having two minimum temperatures.
Speaker: Pediatrics had 35 degrees and adults had 36.
Speaker: The exam techniques were a little bit different, the waiting periods were different, the use of ancillary testing was different and
Speaker: There were a number of lawsuits that came out, particularly in the pediatric age groups for teenagers where there was concern regarding the diagnosis or the permanency of the state based on those legal cases, not based on the guidelines.
Speaker: But we decided that it would be prudent to combine the guidelines where we could for adult and pediatrics because most things are really quite similar.
Speaker: including, for example, the neurological exam and confounders.
Speaker: So we did that to provide unified guidance, but also to give carve-outs for pediatrics because
Speaker: their cranial physiology is different below the age of two, that they have open sutures and fontanelles that may allow for more intracranial expansion.
Speaker: They have different blood pressures based on their ages and so forth.
Speaker: And so that's why we combined them where we could, and then we called out where they were different and necessarily different.
Speaker: We continue to try to move towards a very stringent and
Speaker: conservative approach, not that we weren't stringent and meticulous before, but with every iteration, it becomes, I would say, really a bigger point of emphasis and erring on the side of not determining that somebody's brain dead without absolute certainty.
Speaker: That's a theme that you can see throughout this time.
Speaker: document that we really want to make sure that people are absolutely certain.
Speaker: And then the last thing I'll say is there were areas where there was a need for new guidance that hadn't been touched in prior guidelines such as what about patients who do undergo an intracranial procedure?
Speaker: How do you proceed there?
Speaker: What do you do about patients who have a primary infratentorial injury such as a brainstem or cerebellar stroke?
Speaker: How can you be sure that they have concomitant supratentorial injury?
Speaker: What do you do about patients who are on ECMO or have been hypothermic, either iatrogenically or environmentally?
Speaker: What about pregnant persons?
Speaker: How about the need for consent?
Speaker: And then we also specified regarding the neuroendocrine function, how that can be variably preserved and still be a brain dead patient.
Speaker: So those are some of the things that we, in general, added that we thought would be useful for practitioners.
Speaker: Absolutely.
Speaker: And one of the things that struck me reading the guidelines is exactly what you mentioned, almost like a philosophical approach that reminded me of our justice premise that everybody is innocent to proven otherwise.
Speaker: And it feels like our approach should be people are not brain death unless we can absolutely prove otherwise.
Speaker: Correct?
Speaker: Absolutely.
Speaker: That's 100% correct.
Speaker: So we are looking to disprove that they are alive.
Speaker: So we're going into this looking for signs of life to disprove that they have brain death.
Speaker: And so it's only after you've done everything meticulously and you've ruled out any signs of life that you can say definitively if someone is brain dead.
Speaker: Perfect.
Speaker: So let's start into go ing in a little more detail into some of the areas of the guidelines.
Speaker: The guidelines are organized in different categories.
Speaker: And then there's really an enormous number of recommendations with rationales and supporting evidence.
Speaker: But in terms of general principles for evaluation of BD slash DNC, like we mentioned, when should we consider this evaluation?
Speaker: When should we start thinking about maybe I should evaluate this patient for BD slash DNC?
Speaker: Yeah, I would say any patient with a neurological catastrophe who has minimal to no brain function initially, they have to be a little careful in patients with cardiac arrest, and I'll get to that in a minute.
Speaker: But the other areas are making sure that there's no confounding.
Speaker: And then from the new in the guidelines,
Speaker: making sure that you have neuroimaging consistent with what I call cerebral circulatory arrest, or you can colloquially call it a no-brainer scan, that it looks so disastrous that you can make the argument that there's no way that there could be blood getting into that cranium based on the degree of swelling that is present.
Speaker: And so we really put an emphasis on having neuroimaging that's consistent with that cerebral circulatory arrest.
Speaker: The times that you can be
Speaker: Potentially Fooled is early on after a cardiac arrest where a patient can look brain dead and this has been known for decades but they can regain neurological function so you always have to wait at least 24 hours in a cardiac arrest patient and if you cooled them you have to wait for longer you have to wait 24 hours after they've been completely rewarmed and I always try to get a second CT scan or even MRI at that time point to make sure that I've got neuroimaging that's entirely consistent with brain death.
Speaker: Dave, is there in the new guidelines any indication of who in terms of expertise should be doing these BD DNC evaluations?
Speaker: Yeah, so that was an area where we really had a lot of discussion.
Speaker: And we came down by saying that as attending clinicians performing exams must be appropriately credentialed members of the hospital's medical staff and adequately trained and competent in the evaluation of brain-dead patients in adults or children as applicable.
Speaker: And this could include intensivists, neurologists, or neurosurgeons, but others as well.
Speaker: And in accordance with local laws and institutional standards, there were some
Speaker: places where advanced practice practitioners perform this and perform them independently.
Speaker: And we said that that's in accordance with local laws and institutional standards.
Speaker: They also have to be appropriately trained and credentialed and competent in the evaluation in children.
Speaker: However, trainees or acute care critical care APPs in settings where they're not permitted to do independent evaluations must be directly supervised by an attending physician who themselves meets the criteria for adequate training and credentialing.
Speaker: And in terms of what that specific education includes, it can be a completion of a supervised evaluation in a clinical environment or supplementary education in online courses, such as what's put on by the Neurocritical Care Society, which I strongly recommend.
Speaker: But the best is really training with a mannequin, and there are
Speaker: new courses that will be coming out that can be very helpful for working through challenging scenarios, especially working on exam technique with a mannequin, which I strongly recommend.
Speaker: Perfect.
Speaker: And in terms of you mentioned a little bit about some of the prerequisites before we start evaluating patients and determine where they have BD slash DNC, you talked about identifying an etiology for a devastating, catastrophic neurological injury.
Speaker: We talked about having neuroimaging that supports that.
Speaker: There's also in the literature mention of reversible mimics or potential diseases that could fool us.
Speaker: You did talk about the early phases of
Speaker: cardiac arrest.
Speaker: Could you mention other reversible mimics that we should be aware of in our differential?
Speaker: Yeah, so there's new guidance now that's provided in the guidelines regarding the different drugs and their potential metabolism based on age and obesity, metabolic dysfunction in the patient, etc.
Speaker: But there's also guidance regarding the different metabolic derangements that patients can have.
Speaker: And this was
Speaker: clamored for by people for years that they wanted some guidance regarding practical thresholds for things like sodium, BUN, ammonia, etc.
Speaker: So we provided that.
Speaker: And I just want to give the caveat that this is consensus-based and people need to use their judgment in individual cases.
Speaker: But there is new guidance regarding those things which hopefully will satisfy people in that regard.
Speaker: And any comments also on hypothermia, hypotension?
Speaker: Right, yeah, so hypothermia is a big one to watch out for, either atrogenic or environmental.
Speaker: And so now we say that the person has to be at least 36 degrees for at least 24 hours.
Speaker: So if they were less than 35.5, you have to re-warn them and you have to wait for 24 hours.
Speaker: And why, you may ask, and we'll say, well, we had to draw the line somewhere.
Speaker: And again, it's a conservative approach, making sure that there's no
Speaker: false positive determination because when you look at the case reports that have come up with false positive determinations hypothermia is a big one.
Speaker: And then hypotension also we not only have a systolic blood pressure minimum requirement of 100 but also a mean arterial blood pressure of at least 75 because both are important obviously and now that guidance is there and that's both for patients on or off ECMO
Speaker: Obviously, if they're on VA, ECMO, and a non-pulsatile heart, then at least the MAP of 75 is required.
Speaker: In children, it's greater than the fifth percentile for age, so that's relatively straightforward.
Speaker: One caveat to think about is patients who are chronically hypertensive, that if you think they might be living at a higher blood pressure, then that should be the blood pressure that you aim for.
Speaker: But we didn't put specific parameters to that, but it's a consideration, again, if you're going to have a conservative approach, which we recommend, then consider if the patient might be chronically hypertensive and require a higher blood pressure during testing.
Speaker: Perfect.
Speaker: So once we've determined that any potential reversible mimics has been addressed with, we've taken care of making sure the patient has a catastrophic injury that would support the diagnosis of BD slash DNC, we start with a neurologic examination.
Speaker: What is required in terms of this evaluation?
Speaker: What are the components of the whole evaluation?
Speaker: And then the other thing I wanted to ask you about is for the exam itself, how many exams and what's the timing for all this?
Speaker: Yes, so the clinical evaluation remains the same, and that is that you have to have a patient who's in coma, has no brain stem reflexes, and has apnea in the face of a hypercarbic and acidotic challenge.
Speaker: So coma means an absence of all unresponsiveness to auditory, visual, and tactile stimulation.
Speaker: Loss of brainstem reflexes includes all of the reflexes that we've previously tested, including pupils, corneals, oculocephalic, oculovestibular, gag and cough reflexes.
Speaker: And then the apnea test, I'm sure we can get into as well, but again, that's allowing the patient's PCO2 to rise and their pH to drop below certain thresholds.
Speaker: And then showing that their medulla does not kick in and trigger for the patient to take a breath.
Speaker: In terms of the number of examinations, it remains two examinations and two apnea tests in children
Speaker: And in adults, we say one examination is the minimum criteria and definitely only one apnea test.
Speaker: However, we do say that performance of a second examination in adults may decrease the risk of a false positive determination due to diagnostic errors.
Speaker: So we fall short of saying that two examinations are required in adults, but you can read that as it's strongly encouraged.
Speaker: And certainly in our guidelines at my center,
Speaker: we are keeping it at two examinations, and we do think that that provides a more meticulous and stringent approach.
Speaker: And in respect to those two exams, obviously it would be different individuals, and would it have to be at a set time difference?
Speaker: Yeah, in adults there is no difference in time.
Speaker: In children, it's six hours that
Speaker: has been mandated that's a bit arbitrary.
Speaker: The most important waiting time between examinations, or let me rephrase that, the most important waiting time is before any evaluations because if you're unsure about the permanence of the situation, you shouldn't be doing any brain death testing in an individual.
Speaker: An intervening waiting period is arbitrary and likely unnecessary.
Speaker: Pediatrics wanted to keep a waiting period, and that's fine.
Speaker: So that's present in children, but there's no specified waiting period in adults.
Speaker: Perfect.
Speaker: Now, you did mention the components of the neurologic examination, and we'll also link our previous conversation that talks about this as well, and that has not changed.
Speaker: I do have a couple of questions, Dave, on this topic, though.
Speaker: And maybe I misunderstood the guidelines, but it almost felt that in terms of the oculocephalic reflex and the oculovestibular reflex,
Speaker: It wasn't an and, but it was you do the oculosephalic, and if you couldn't do that, you can do the oculovestibular.
Speaker: Did I get that wrong?
Speaker: Yeah, I think you did, and I'm sorry if we didn't phrase that as eloquently as we could have.
Speaker: As a general rule, you want to test everything you can in every patient.
Speaker: And so if you can test the oculosephalic and the oculovestibular response, then you do.
Speaker: The only time that you wouldn't do the oculosephalic reflex would be in a patient with cervical spine instability or concern about a skull base issue.
Speaker: And so that's the only part of the test that you can skip, and still do a clinical determination.
Speaker: However, the ocular vestibular
Speaker: you cannot skip and it is felt to be the more potent of the two evaluations to test the middle of the brain stem and only in the in the situation where you're concerned about ototoxicity that it wouldn't be a valid test and you'd have to get an ancillary test but you don't skip these that test at any time unless you have a non-intact tympanic membrane and you're worried about
Speaker: instilling into it and causing an infection because it won't be a clean space.
Speaker: If that's the case and you cannot do ocular vestibular testing, then you're really mandated to get ancillary testing in addition to the complete exam, including the apnea test or tests if it's a pediatric patient.
Speaker: The oculosephalic reflex or the doll's head maneuver, as it is colloquially called, is the only thing that if you cannot test it, you can still do a clinical determination of brain death.
Speaker: And when we say you cannot test it, it's not that it's not coming out as you expect it.
Speaker: You have a cervical injury and you can't manipulate the head, right?
Speaker: Exactly.
Speaker: You're precluded from testing it because of the potential for injuring the patient.
Speaker: Perfect.
Speaker: So the clarification then is all the elements of the clinical exam, assessment of arm responsiveness, assessment of the pupillary light reflex, octrocephalic reflex, ocular vestibular reflex, corneal reflex, gag and cough frequencies must be done.
Speaker: When we have a cervical injury and cannot safely do the oculosephalic reflex, the ocular vestibular reflex by itself will suffice.
Speaker: Okay, perfect.
Speaker: So that is, I think, what I wanted to clarify.
Speaker: Now, you did mention, Dave, the apnea test, and that seems to be obviously a source of...
Speaker: straightforward it looks like on paper but then when people start doing it all all sorts of things pop up right so let's talk about the apnea test and in terms of it if you could just outline in general terms the procedure for performing the apnea test and then we can go into some more details
Speaker: Sure.
Speaker: So the first thing is going to be establishing that the patient is stable enough from a pulmonary standpoint to undergo apnea testing.
Speaker: And so they should be on relatively low settings and something that you could safely take off of the ventilator.
Speaker: If you reduce the patient to 5 and they start to desaturate, that may be a patient that's not able to get through the test safely.
Speaker: Everybody gets pre-oxygenated.
Speaker: We like to get the PaO2 greater than 200.
Speaker: and you want to establish a normal capnea unless they're a CO2 retainer, which I'll get into.
Speaker: You want to establish a normal pH.
Speaker: You want to make sure that they are euvolemic, and this is so important.
Speaker: because many of these patients do develop diabetes insipidus and they may have a negative fluid balance and be very much at risk for getting hypotensive because of their hypovolemia and the acidosis that you're going to cause.
Speaker: So you want to make sure they're euvolemic.
Speaker: And then you make sure that they're normothermic also, and again, they have to have a minimum temperature of at least 36 degrees Celsius.
Speaker: I do recommend disconnecting the patient from the ventilator if you can, because then there's no question of whether a breath came from auto cycling of the ventilator or from the patient.
Speaker: You can do it on CPAP with 100%.
Speaker: O2 going through or with a flow inflating resuscitation bag with a functioning peep valve as well.
Speaker: Those are other ways of doing this in a patient who might be worried about having pulmonary decompensation during the test.
Speaker: Perfect.
Speaker: And you did mention the CO2.
Speaker: So can we talk about the CO2, the baseline required, and the post-apnea test requirements as well?
Speaker: Great.
Speaker: So if they have no history of chronic hypercarbia, then you're going to be aiming for a normal PCO2.
Speaker: However, if they're known to be chronically hypercarbic and you know their baseline level, then the level that you start with should be at the patient's chronic baseline.
Speaker: If they're suspected to have chronic hypercarbia but you don't know their baseline PCO2 level, then it should be at the estimated chronic baseline, but you also have to get ancillary testing in addition in that setting.
Speaker: If they do not have chronic CO2 retention, you're going for the PCO2 level of 60 or greater and 20 above the patient's pre-apnea test baseline.
Speaker: And
Speaker: If they're known to have CO2 retention and you know their baseline PCO2, then you must conclude that the adocyanate test is positive if they have no respirations and the pH goes less than 7.3 and the PCO2 is greater than 60 and 20 above the patient's known elevated premorbid baseline,
Speaker: and again if they are suspected to have chronic CO2 retention but you don't know their baseline level, you're again going for the pH of less than 7.3, the pCO2 of greater than or equal to 60 and 20 above their baseline at the pretest level, and you have to get ancillary testing in addition to that.
Speaker: And this is all spelled out, I think, very clearly in the new guidelines.
Speaker: Absolutely.
Speaker: And the one thing I just wanted to mention also is that if you usually go for 10 minutes, but if at 10 minutes the patient is not having any hemodynamic instability, there is no severe hypoxemia, and you're still not at the threshold that you mentioned for CO2, you can continue and recheck as you go along, correct?
Speaker: Correct.
Speaker: That's absolutely correct.
Speaker: And I like to send ABGs along the way, and hopefully the lab can report them very quickly.
Speaker: But it's also helpful to send it at 5, 8 minutes, etc., because the patient may decompensate later, and if they reach their PCO2 and pH goals, but they didn't breathe, then your test is done.
Speaker: But I've heard of people going for longer, even up to 30 minutes.
Speaker: I've never gone that far.
Speaker: But some patients don't generate a lot of CO2,
Speaker: and so you often can go for longer.
Speaker: But if you're going to repeat the test and go for longer, you again have to reestablish normal capnea, a normal pH, and pre-oxygen activation.
Speaker: I can't emphasize that enough.
Speaker: Perfect.
Speaker: So in terms of recapping, what is required for an apnea test to be consistent with brain death, death by neurologic criteria?
Speaker: Yeah, so I mentioned it a little bit earlier, but regarding...
Speaker: a patient who does not have chronic hypercarbia, you're going for both a pH goal and a PCO2 goal.
Speaker: And the PCO2 goal is at least 60 and 20 above.
Speaker: So previous adult guidelines said or, and we changed that to an and.
Speaker: It always should have been and, in my opinion.
Speaker: And we're making sure that the patient's getting acidotic because it's not just the hypercarbia, but really the acidosis that's triggering the medullary chemoreceptors to trigger a breath.
Speaker: And so those things are now in place.
Speaker: Again, if somebody is a chronic hypercarbic and you know their baseline values, then again they have to go above 60 and 20 above their known baseline level and they don't require an apnea test.
Speaker: If they're suspected to be a CO2 retainer and you don't know their baseline BCO2, then you have to go above 60 and 20 above the baseline value and get an ancillary test in addition in that situation.
Speaker: Perfect.
Speaker: So ultimately, really, what we're looking for is no spontaneously triggered breath under the right conditions, which is not a time-based situation, but a situation based on having a pH below 7.3, a PCO2 above 60, and a PCO2 that's 20 above their baseline when we know the baseline.
Speaker: Yep, that's correct.
Speaker: Perfect.
Speaker: Now, when do you abort or when should you abort a apnea test, which is not the same as a negative or a positive, right?
Speaker: A positive apnea test is consistent with brain death, a negative apnea test, there's spontaneous breathing, and an aborted apnea test is done for safety.
Speaker: When should we do that?
Speaker: Yeah, so there are three conditions where you have to consider aborting the APTAN test.
Speaker: No, number one is going to be regarding their blood pressure.
Speaker: So if the systolic goes less than 100 or the mean arterial pressure goes less than 75 in adults or the SPP and the mean arterial pressure go less than the fifth percentile for age in children, despite the titration of vasopressors, inotropes, or intravenous fluids during the procedure, which you're perfectly allowed to do,
Speaker: Number two would be a progressive decrease in oxygen saturation below 85%.
Speaker: In the old adult guidelines, we said below 85% for 30 seconds.
Speaker: We took out the 30 seconds and we said if they start going to less than 85%, you abort the test then.
Speaker: And the third condition is if you have a cardiac arrhythmia with hemodynamic instability.
Speaker: So patients may have AFib or
Speaker: a flutter and that's okay but if they start to drop their pressure then that's going to be a situation where you have to abort the test.
Speaker: And in these situations, you basically first should always pre-plan to mitigate these, right?
Speaker: So have appropriate fluid loading, have appropriate drugs for blood pressure, that's a concern, have appropriate pre-oxygenation like you mentioned.
Speaker: But if we have to abort, my understanding is that either you try to redo the apnea test when it's safer, if possible,
Speaker: But if not, obviously you now are going to fall in the category of requiring ancillary testing to confirm the diagnosis.
Speaker: Yeah, that's absolutely right.
Speaker: So maybe you can stabilize the patient, but if you're concerned and you can't do it, then you're required to get an ancillary test in that situation.
Speaker: Okay.
Speaker: So before we go to ancillary testing, could you talk a little bit about the apnea test in patients with ECMO?
Speaker: That is an area of interest for obviously our audience, but also I think it's a very unique addition to the guidelines in this iteration.
Speaker: Yeah, it's a great question, and we're so happy that we could provide guidance on ECMO specifically in this, and hopefully we'll provide even more guidance in the years to come.
Speaker: The first principle is pre-oxygenate the patient again.
Speaker: If you don't pre-oxygenate the patient and they get hypoxic, they're almost certainly going to crash during the test.
Speaker: So you want to use 100% FiO2 on the ventilator and through the membrane lung as well.
Speaker: To achieve the adequate increase in the PCO2 level, you titrate exogenous CO2 into the ECMO circuit or adjust the sweep gas flow rate to 0.2 to 1 liter per minute.
Speaker: You sample ABG measurements from both the patient's distal arterial line and the ECMO circuit post-oxygenator for patients on VA ECMO.
Speaker: And the PCO2 and pH levels from both locations
Speaker: are required to meet the criteria for the apnea test to be positive.
Speaker: And this ensures that independent of the mixing point, the PCO2 and the pH levels and the cerebral circulation meet the criteria.
Speaker: For patients on VV ECMO, sample ABG measurements can be only from the patient's distal arterial line, as this will be an appropriate approximation.
Speaker: To avoid hypotension during the test on ECMO, you increase the flow rates, intravenous fluids,
Speaker: or provide vasopressor inotropic support.
Speaker: Perfect.
Speaker: And then the next topic I wanted to ask you about was ancillary testing as part of the BD-DNC evaluation.
Speaker: We did mention several situations, but just to reemphasize, when do we need an ancillary test?
Speaker: So number one would be when you have injuries like fractures to the cervical spine, the skull base, or the orbits, or severe facial injuries or swelling or other abnormalities that could preclude an accurate assessment of any components of the neurological exam, with the exception, as I mentioned earlier, to the oculocephalic reflex.
Speaker: or if you have injuries to the cervical spinal cord that limit the adequate assessment of extremity movement or spontaneous respiration, such as if they have a C-spine fracture and you're concerned that they might have a phrenic nerve palsy or inability to move based on a severe spinal cord injury or even a severe peripheral neuropathy, then the ancillary test would be required then.
Speaker: Number two would be if you're unable to perform or complete the apnea test safely because of the patient's risk of cardiopulmonary decompensation or inability to interpret the PCO2 levels in a patient with chronic hypercarbia without a known baseline PCO2 level.
Speaker: Number three would be when you have neurological findings on exam that are difficult to interpret, such as limb movements that may or may not be spinally mediated.
Speaker: If you're unsure and your experts are unsure, then you should get an ancillary test.
Speaker: And number four would be metabolic derangements that are unable to be adequately corrected and you think could be potentially confounding the exam.
Speaker: That would be another situation where you'd be mandated to get an ancillary test.
Speaker: I would like to start first with some problematic ancillary tests, and then we can go into what's currently recommended by the guidelines.
Speaker: But...
Speaker: EEGs and even SEPs, but especially EEGs, are commonly ordered or requested in the evaluation of these patients, yet as an ancillary test, they're kind of problematic.
Speaker: Could you talk about that a little bit, Dave?
Speaker: Yeah, so EEGs were used for many decades and almost certainly should not be used in isolation because
Speaker: There are two problems.
Speaker: One, you can get false positives because the patient, you're not getting any reading of electrical activity in the brainstem.
Speaker: A cortical EEG or a scalp EEG is only going to read the cortical activity.
Speaker: And so remember, the brainstem is the last thing to go in brain death.
Speaker: So
Speaker: in isolation EEG would not be helpful.
Speaker: You could also get false negatives because there's a lot of electromagnetic interference in the ICU setting and actually could show blips on the EEG which are not coming from the patient.
Speaker: FCPs may be helpful for assessing brainstem integrity but remember they only assess the somatosensory pathways and so that's not really telling you about all of the brainstem integrity.
Speaker: So
Speaker: Electrical tests such as EEG and SACP have really fallen out of favor and now have been removed from the guidelines in the most recent iteration as an acceptable test.
Speaker: What are tests that are accepted in the guidelines right now and what should we be considering for ancillary tests when they're indicated?
Speaker: Yeah, so there are really three and they're all flow-based.
Speaker: So the first one is the gold standard, which is a catheter angiogram where you inject under pressure into the carotid and the vertebral circulation.
Speaker: And you're looking for any
Speaker: flow as the vessels pierce the dura to show that it's getting any effective forward intracerebral flow.
Speaker: Transcranial Doppler is a useful test as well.
Speaker: It's the only one that's really portable and that can be very helpful for patients who are too unstable to go for a different ancillary test.
Speaker: It's technically challenging.
Speaker: We don't accept the absence of flow signal.
Speaker: You really actually have to see
Speaker: reverberating flow where the flow goes to zero or negative numbers in diastole, which tells you that the ICP is higher than the mean arterial pressure.
Speaker: The test has to be done twice.
Speaker: It has to be done both anteriorly and posteriorly, and it has to be separated by at least 30 minutes between the tests, and it can be technically challenging.
Speaker: The third is going to be a spec study or nuclear medicine radionuclide study.
Speaker: This is using a tracer to look for cerebral perfusion.
Speaker: We prefer lipophilic agents because a lipophilic agent will not just show you tracer within the vasculature, but also in metabolically active tissue, so it's felt to be a more sensitive test to look for cerebral viability.
Speaker: This again requires transport, but it's probably the most commonly used test and should be considered highly reliable.
Speaker: Any comments on CTA, MRA technology, which I think some people have also proposed?
Speaker: Yeah, so people would love to use CTA and MRA, and I'm in that camp.
Speaker: I'd love to use that as well.
Speaker: The problem is they haven't been validated, and remember that the difference between a catheter angiogram and a CT angiogram is that the CT angiogram is a venous injection, and we don't know what the proper timing is to know when a patient has had
Speaker: adequate observation of their cerebral vasculature to say that there is no forward flow.
Speaker: Whereas if you're doing a dynamic angiogram under pressure, you can tell that there's no flow going angiocranially.
Speaker: So that's considered a much more viable test.
Speaker: We would love to validate CTA against a more standard or gold standard
Speaker: circulatory tests and that's ongoing work that we're doing now.
Speaker: But for now, I mean, we stick with the ones that you mentioned.
Speaker: And the last question I have on ancillary testing is if you have met all the criteria for prerequisites, you have imaging that supports a catastrophic injury and etiology, all the elements of the test are inequivocally consistent with brain death, you do the apnea test, do you need an ancillary test?
Speaker: Now, if you can test everything that is testable, with the exception, again, of the oculosephalic, and there's no confounders, you do not need to get an ancillary test.
Speaker: It's only when you cannot fully perform all the clinical testing or safely perform all the clinical testing or eliminate confounding.
Speaker: Those are your circumstances.
Speaker: Perfect.
Speaker: So it's not a requirement when we can meet all the other criteria, which in some places I think people always feel that they have to have that.
Speaker: And like you mentioned, I mean, it has a place, which is important.
Speaker: But if you can meet all the criteria, you can definitely determine death by another criteria with those.
Speaker: Perfect.
Speaker: Yeah, I actually worry more about places where they go straight to ancillary testing, and I've seen that happen where they'll get a spec just to see if the patient is brain dead, and I think that's a really dangerous practice.
Speaker: I think the clinical testing should always be
Speaker: paramount in the way that people determine unless they absolutely have to get an ancillary test.
Speaker: So that's a strong emphasis for us.
Speaker: Perfect.
Speaker: Now let's talk about some special considerations.
Speaker: You did mention at the beginning of our conversation, Dave, the concept of consent.
Speaker: Do we need to consent families, because we can't consent the patient, obviously, for undergoing this evaluation?
Speaker: How does that work, and what's the thought of the guidelines?
Speaker: Yeah, so, I mean, there's been a bit of back and forth pro-con debate about getting consent for brain death testing.
Speaker: And we stay consistent in the guidelines by saying consent is not required.
Speaker: This is not a procedure that carries a risk to the patient.
Speaker: If you think that the patient is not potentially brain dead, you should not be testing the patient for brain death.
Speaker: The pre-test probability should be very, very high when you're doing this.
Speaker: There has not been
Speaker: a good argument made to require consent for this.
Speaker: It's a medical diagnosis like any other.
Speaker: We would not require consent to declare somebody dead by cardiopulmonary means and thus this is no different and we remain consistent with prior guidelines in that regard.
Speaker: When we complete this process evaluation for brain death and death-pagnudial criteria, and we determine that the patient, the exam is consistent with this, and we need to pronounce the patient, what's the time of death?
Speaker: So the time of death, if you determine them clinically without an ancillary test, is going to be the time that the ABG is reported by the lab,
Speaker: and that those values have reached the criteria.
Speaker: If it's an ancillary test, it's the time that the attending physician signs the report.
Speaker: Those are the time of death for both adult and pediatrics.
Speaker: And once we have that time of death, what is the current thought process or recommendation of the guidelines in terms of how do we proceed from there?
Speaker: I think that there's obviously an area where, okay, the patient's brain dead, but it's not as soon as we have all that without conversing with families, we just take the patient off life support.
Speaker: How do you deal with that?
Speaker: Yeah, so, well, first of all, that shouldn't be your first conversation you're having with the family is to tell them that their loved one is dead by brain criteria.
Speaker: I think that can be very confusing for them.
Speaker: So it's important to have a conversation with them and say that the patient has had a neurological catastrophe.
Speaker: You're very concerned that they may have brain death or may progress to brain death.
Speaker: And here's what that means, and here's the type of testing that we'll be doing.
Speaker: I also like for families to be able to be there when I do the testing, both the clinical exam and the apnea test, because that can be very helpful for them to really see and see for themselves that their loved one isn't breathing for 10 minutes off a ventilator.
Speaker: That's very, very powerful for them.
Speaker: When you have the conversation, I do say that your loved one has died, and their time of death was
Speaker: You know, 10.53 a.m.
Speaker: or p.m.
Speaker: I think that's helpful for people to have that finality.
Speaker: I do know that organ donation is a potential for our patients, but I also know that we need to decouple that conversation.
Speaker: So I've been having conversations with my OPO along the way to see if the patient is a potential candidate and then try to have a way to introduce them to the family once the family has come to terms.
Speaker: with the diagnosis and typically it's in the same conversation and families are very willing to listen, but we give them the opportunity to hear about the potential for Ergon donation and see what next steps would follow after that.
Speaker: I wanted also to ask you as we wrap up the conversation on some of these special patient populations, and you did mention pregnancy.
Speaker: Pregnancy in the ICU is always a very difficult topic because obviously there's more than one life at danger.
Speaker: But could you talk about the evaluation, determination of BD, DNC, and pregnant patients and some of the aspects that the guidelines have discussed?
Speaker: Sure.
Speaker: So remember the pregnancy in and of itself is not a contraindication to brain death evaluation.
Speaker: And just like any other patient, clinicians should diagnose pregnant persons with a catastrophic permanent brain injury for brain death or death by neurological criteria.
Speaker: In that process, however, you want to make sure you're getting
Speaker: other clinicians involved, including maternal fetal medicine, child neurology, neonatology, to educate and discuss with surrogate decision makers regarding the risks and benefits of the fetus to continuing maternal organ support in that situation.
Speaker: That can be challenging, but certainly has been done.
Speaker: It depends on a lot of factors, including the stability of the
Speaker: the mother, but also how far along the pregnancy is.
Speaker: We didn't get into that kind of detail.
Speaker: It's really a matter of getting your experts involved to see what is the likelihood in an individual patient given the physiology of the mother and the viability of the fetus.
Speaker: So that's some new guidance that we provided in this guideline.
Speaker: And obviously there's been some reported cases of brain dead or pregnant patients in whom support was continued a little bit longer to try to get the fetus to term.
Speaker: And again, like you said, that is a granular, very specific case that should be discussed at the level with the maternal fetal experts and the whole team.
Speaker: That's correct.
Speaker: That's the way to approach it at this point.
Speaker: Could you talk about the primary posterior fossa injury patients and why this is important, especially for our non-neurology crowd?
Speaker: Sure.
Speaker: So...
Speaker: When you have a patient who's had a brainstem catastrophe, let's say a massive bleed in their brainstem, they could look comatose.
Speaker: They could have brainstem areflexia.
Speaker: They could even be apneic during PCO2 and acidotic challenge.
Speaker: However, they may still have circulation to their cerebral cortex up above.
Speaker: And so it's important to make sure that you've got
Speaker: at least in the U.S., evidence of catastrophic injury to the supratentorial structures also.
Speaker: That is typically in the setting of a patient who develops hydrocephalus from their posterior fossa injury and is not treated because the neurosurgeons appropriately say that there's no indication for the
Speaker: the ventriculostomy because of the patient's overall prognosis it would be deemed futile.
Speaker: So if a patient then develops massive hydrocephalus and their ICP is presumably extremely high, they're going to get secondary ischemic injury and catastrophic supratentorial injury as well.
Speaker: So we're really emphasizing the quote whole brain formulation of brain death and you really need to have
Speaker: conventional neuroimaging, meaning a CT or an MRI that shows supratentorial injury in addition to infratentorial before initiating a brain death evaluation.
Speaker: Are there any other topics that we should cover as we wrap up regarding to the guidelines?
Speaker: No, I think you've covered it.
Speaker: Again, it's a very lengthy document, and I apologize for that, but we wanted it to be very thorough.
Speaker: We think the tables are very helpful.
Speaker: We want you to have meticulous attention to technique, which we really spell out in the tables also, so please use that.
Speaker: And then we are updating the Neurocritical Care Society.
Speaker: toolkit with a lot of new resources and providing great guidance through that mechanism as well.
Speaker: So you have a lot of tools to do this correctly.
Speaker: This is really one of those diagnoses in medicine where we have to get it right 100% of the time.
Speaker: And so please educate yourselves adequately so you feel comfortable in the clinical setting.
Speaker: Well, thanks, Dave, for sharing all that and for all the work you've done in this area that is not only extremely important, but I think really is quite fascinating, right?
Speaker: The whole concept of at what point does life really stop is something that for many years has kept me in awe at the bedside because definitely we have to make some arbitrary decisions.
Speaker: But it's just, I mean, it's something that's full of wonder and unanswered questions.
Speaker: But I would like to close the podcast with asking you some questions that are unrelated to the clinical topic.
Speaker: You've been on the podcast before, so you know how it works.
Speaker: Would that be okay?
Speaker: Of course.
Speaker: Any books that you have recently read that have influenced you significantly or that you have gifted to others?
Speaker: Well, the book I love to gift and re-gift is called Boys in the Boat, which is a story of the University of Washington rowing team from the 1930s.
Speaker: It's a it's a terrifically written book and very inspirational.
Speaker: I love team of rivals by Doris Kearns good good one on Abraham Lincoln and his cabinet and I really love
Speaker: anything by J.D.
Speaker: Salinger.
Speaker: I'm very old school, and so he put anything by J.D.
Speaker: Salinger in front of me, and I'll read it for sure.
Speaker: Perfect.
Speaker: So all of these, I mean, obviously great, great reads, and we'll link them in the show notes.
Speaker: The second question relates to beliefs.
Speaker: What do you believe to be true in medicine or life that many other people or most people don't believe or don't act like they believe?
Speaker: Well, I don't know if other people don't believe this, but one thing I've come to realize in the age of wellness and
Speaker: work-life balance is that I think the key to wellness in medicine is finding joy in your daily work.
Speaker: That what we get to do on a daily basis, whether it's clinical research or education, it's really beautiful.
Speaker: And many people in their careers don't get this kind of joy.
Speaker: And so rather than focusing on the negatives, I like to focus on the positives.
Speaker: And I think that I'm a big student of stoic philosophy and a big believer in focusing on what I do control, not to dismiss the external pressures and problems that healthcare has created that impact our wellness, but I do believe that finding joy is an internal choice and one that a lot of us have accessible, and we should definitely, I mean, work on it because I do agree it does a...
Speaker: help your well-being significantly.
Speaker: What would you want every intensivist listening to us, every APP listening to know?
Speaker: Could be a quote, a fact, or just a thought to close.
Speaker: Yeah, so in the neuro ICU, we deal with a lot of death and destruction all the time.
Speaker: And what I'd emphasize is that you're able to really help every patient and family regardless of the outcome.
Speaker: Given that many of our patients die in intensive care,
Speaker: we shouldn't only celebrate the saves, but also the good deaths or patients who die with dignity and peace.
Speaker: So you can't save everyone.
Speaker: And sometimes it's just people's time.
Speaker: And I think that allowing a patient to pass on with peace and dignity can be a beautiful thing and very helpful for families.
Speaker: I think this is as
Speaker: important a skill and an intensivist as any other.
Speaker: And I think this is a perfect place to stop.
Speaker: Dave, once again, thank you for all the work you've done in this area of neurocritical care, brain death, and DNC.
Speaker: Very happy to have you share your expertise with our audience and hope to have you back to talk about this and other topics.
Speaker: It was my pleasure.
Speaker: Thank you, Sergio.
Speaker: Thank you for listening to Critical Matters, a sound podcast.
Speaker: Make sure to subscribe to Critical Matters on Apple or Google Podcasts and share with your network.
Speaker: Sound's transforming the way critical care is provided in hospitals across the country.
Speaker: To learn more, visit www.soundphysicians.com.
