1 00:00:00,040 --> 00:00:03,960 Welcome back to the Deep Dive. Today we're scrapping the usual 2 00:00:03,960 --> 00:00:06,840 format. No broad overviews, no, you 3 00:00:06,840 --> 00:00:09,560 know, casual skimming. We are simulating a pressure. 4 00:00:09,560 --> 00:00:11,880 Cooker we certainly are. We are going right into the 5 00:00:11,880 --> 00:00:16,200 operating theater or or maybe more to the point, the 6 00:00:16,200 --> 00:00:18,120 examination hall. That's exactly right. 7 00:00:18,280 --> 00:00:20,000 And look, I'm not just the expert today. 8 00:00:20,000 --> 00:00:22,560 I want you to think of me as your external examiner. 9 00:00:22,880 --> 00:00:25,000 I'm the senior faculty member from a neighboring Medical 10 00:00:25,000 --> 00:00:26,920 College. I'm sitting across the table 11 00:00:26,920 --> 00:00:29,440 from you, and frankly, I've heard every wrong answer in the 12 00:00:29,440 --> 00:00:32,200 book. I have 0 patience for fluff. 13 00:00:32,520 --> 00:00:36,400 My job today is to grill you, yes, but ultimately it's to get 14 00:00:36,400 --> 00:00:38,240 you to pass. Because this topic we're 15 00:00:38,240 --> 00:00:40,480 covering, it isn't just for marks. 16 00:00:40,880 --> 00:00:43,600 It's the difference between a patient going home and a patient 17 00:00:43,600 --> 00:00:44,760 not. I'm ready. 18 00:00:45,320 --> 00:00:48,240 I'm no longer the host. I'm the, let's say, the 19 00:00:48,240 --> 00:00:51,120 terrified postgraduate student preparing for the Gujarat 20 00:00:51,120 --> 00:00:54,920 University anesthesiology exams. I've got my Miller, my Gaiden, 21 00:00:54,920 --> 00:00:56,880 and my Stolting stacked right here. 22 00:00:57,160 --> 00:01:00,400 Good. The topic is reflexes relevant 23 00:01:00,480 --> 00:01:03,640 to anesthesia practice and specifically we're talking about 24 00:01:03,640 --> 00:01:07,080 the ones that kill the Bazol. Jairus reflex is the main event, 25 00:01:07,200 --> 00:01:09,360 but we'll hit the ocular cardiac, the Cushing, all of 26 00:01:09,360 --> 00:01:11,560 them. This is high stakes Physiology, 27 00:01:11,880 --> 00:01:15,640 so Doctors setup's great. Let's begin part 8, introduction 28 00:01:15,640 --> 00:01:17,120 and exam framing. Understood. 29 00:01:17,120 --> 00:01:17,920 Let's do it all. Right. 30 00:01:18,240 --> 00:01:19,520 Don't give me a dictionary definition. 31 00:01:19,840 --> 00:01:22,640 In the context of our practice anesthesia, what is a 32 00:01:22,640 --> 00:01:25,560 physiological reflex? OK, so a physiological reflex 33 00:01:25,560 --> 00:01:29,080 is, well, it's basically an autonomic stimulus response 34 00:01:29,080 --> 00:01:30,720 loop. It's the body's hardwired 35 00:01:30,720 --> 00:01:33,160 attempt to maintain homeostasis. A loop. 36 00:01:33,200 --> 00:01:35,400 OK, yeah. And for the exam, I know I need 37 00:01:35,400 --> 00:01:37,560 to be able to identify the four key components. 38 00:01:38,040 --> 00:01:41,520 A sensor or receptor that detects a change, then an effort 39 00:01:41,520 --> 00:01:45,440 pathway that carries the to the CNSA central integrator, which 40 00:01:45,440 --> 00:01:48,400 is usually the brain stem or medulla, and then finally the 41 00:01:48,440 --> 00:01:50,680 efferent pathway that triggers an effective organ. 42 00:01:50,840 --> 00:01:53,080 Fine, that's first year Physiology. 43 00:01:53,120 --> 00:01:55,680 Yeah. Now tell me why I, as a senior 44 00:01:55,680 --> 00:01:57,440 anesthetist, actually care about this? 45 00:01:57,600 --> 00:02:00,320 Why is this a question that comes up again and again in the 46 00:02:00,320 --> 00:02:03,440 MD exams? Because, well, because 47 00:02:03,440 --> 00:02:06,120 anesthesia is really the art of manipulating these reflexes. 48 00:02:06,320 --> 00:02:09,199 We're either blunting them with our drugs or sometimes we 49 00:02:09,199 --> 00:02:12,320 accidentally trigger them. And when we do, it's a disaster. 50 00:02:12,800 --> 00:02:14,920 These reflexes aren't just textbook trivia. 51 00:02:15,240 --> 00:02:17,080 They are. I mean, they're the primary 52 00:02:17,080 --> 00:02:21,640 cause of that sudden unexplained intraoperative hemodynamic 53 00:02:21,640 --> 00:02:23,840 collapse. Exactly the Oh my God, what's 54 00:02:23,840 --> 00:02:26,640 happening moment, Yes. You can be cruising along in a 55 00:02:26,640 --> 00:02:29,240 totally stable case, everything's perfect, and then 56 00:02:29,240 --> 00:02:32,320 boom, assist alloy on the table. Exactly. 57 00:02:32,640 --> 00:02:36,560 Now in the Gudrat University exams and others, you're going 58 00:02:36,560 --> 00:02:40,120 to see this in three places. First, the theory paper, write a 59 00:02:40,120 --> 00:02:42,360 short note on the Bizzle Geris reflex. 60 00:02:42,360 --> 00:02:45,040 That's a classic 5 or 10 mark question, right? 61 00:02:45,040 --> 00:02:47,000 Standard. Second, the OSCE station, you 62 00:02:47,000 --> 00:02:49,360 might get a clinical scenario, you know, patient crashing 63 00:02:49,360 --> 00:02:51,880 during eye surgery or maybe a shoulder Arthroscopy. 64 00:02:52,080 --> 00:02:56,040 But the third place, that's the most dangerous, the Viva Viva, 65 00:02:56,240 --> 00:02:59,080 the oral interrogation, right? I'll be sitting there and I'll 66 00:02:59,080 --> 00:03:01,400 ask you, doctor, why did the heart rate drop? 67 00:03:01,960 --> 00:03:04,680 And if you just say hypotension, you fail. 68 00:03:04,760 --> 00:03:07,160 It's an instant fail. Because it's not specific 69 00:03:07,160 --> 00:03:08,320 enough. Not even close. 70 00:03:08,320 --> 00:03:10,160 I'm looking for specific keywords. 71 00:03:10,160 --> 00:03:14,720 I want to hear about the fibers, the nuclei, the the paradox. 72 00:03:15,480 --> 00:03:19,800 So with that in mind, let's dive into the big one, Part B, the 73 00:03:19,800 --> 00:03:24,040 bezel Gerish reflex. The BJR, the exam core, as you'd 74 00:03:24,080 --> 00:03:25,200 say. Absolutely. 75 00:03:25,320 --> 00:03:27,440 So define it for me. I'm the examiner, I'm looking at 76 00:03:27,440 --> 00:03:28,080 my watch. Go. 77 00:03:28,440 --> 00:03:32,600 The Bezel Gerish reflex is a a cardio inhibitory reflex. 78 00:03:33,200 --> 00:03:35,680 The gold standard definition, the one from Miller's 79 00:03:35,680 --> 00:03:38,480 anesthesia, is a triad. You see three things happen at 80 00:03:38,480 --> 00:03:40,160 once. Name them hypotension, 81 00:03:40,160 --> 00:03:43,080 bradycardia and and coronary artery dilatation. 82 00:03:43,080 --> 00:03:44,560 Stop right there. You said coronary artery 83 00:03:44,560 --> 00:03:46,040 dilatation. Why'd you include that? 84 00:03:46,080 --> 00:03:48,000 Right. Most students, they forget that 85 00:03:48,000 --> 00:03:49,600 last one. They just say hypotension and 86 00:03:49,600 --> 00:03:52,200 bradycardia. Because that part, that's the 87 00:03:52,200 --> 00:03:54,120 key to the whole cardioprotective theory. 88 00:03:54,120 --> 00:03:57,080 It's what distinguishes the BJR from just a simple, you know, 89 00:03:57,080 --> 00:04:00,520 vasovagal collapse. The dilation suggests the body 90 00:04:00,520 --> 00:04:04,320 is actively trying to perfuse the myocardium even while it's 91 00:04:04,320 --> 00:04:06,720 slowing everything else down. Good, you've read the big books, 92 00:04:06,720 --> 00:04:08,160 I can tell. Now give me the historical 93 00:04:08,160 --> 00:04:09,240 context. Just briefly. 94 00:04:09,360 --> 00:04:11,440 Examiners love it when you can drop a name or two. 95 00:04:11,880 --> 00:04:16,040 OK, it was first described, I think, by von Bazold and Hurt 96 00:04:16,120 --> 00:04:19,800 back in the 1860s, and then later clarified by Jerish. 97 00:04:20,240 --> 00:04:23,600 But really, the key concept for the exam isn't the history, it's 98 00:04:23,600 --> 00:04:25,520 it's paradoxical nature. Explain that. 99 00:04:25,520 --> 00:04:27,480 Why is it paradoxical? This is the aha man. 100 00:04:27,640 --> 00:04:30,080 This is the whole point. It's paradoxical because it 101 00:04:30,080 --> 00:04:32,800 completely contradicts the baroreceptor reflex. 102 00:04:32,880 --> 00:04:35,400 I mean, normally if your blood pressure drops, the 103 00:04:35,400 --> 00:04:39,480 baroreceptors in the carotid sinus and the aorta, they scream 104 00:04:39,480 --> 00:04:43,560 low pressure and the heart rate shoots up, you get tachycardia 105 00:04:43,560 --> 00:04:45,320 to try and restore cardiac output. 106 00:04:45,320 --> 00:04:47,160 That's the normal logical defense, right? 107 00:04:47,280 --> 00:04:49,120 Your body hits the gas pedal. Exactly. 108 00:04:49,200 --> 00:04:52,680 But with the BJR, the patient is hypotensive, but instead of 109 00:04:52,680 --> 00:04:55,320 speeding up, the heart slams on the brakes. 110 00:04:55,640 --> 00:04:58,160 The rate plummets. You get a profound bradycardia 111 00:04:58,160 --> 00:05:00,040 right in the face of hypotension. 112 00:05:00,280 --> 00:05:03,600 It fundamentally works against the body's immediate attempt to 113 00:05:03,600 --> 00:05:05,600 maintain its own perfusion pressure. 114 00:05:05,640 --> 00:05:08,760 Precisely. It's a reflex that seems on the 115 00:05:08,760 --> 00:05:11,560 surface to be sabotaging this systemic circulation. 116 00:05:11,560 --> 00:05:14,000 Yeah, it makes no sense, which is why you need to understand 117 00:05:14,000 --> 00:05:17,000 the mechanism. So let's get granular Section 3 118 00:05:17,560 --> 00:05:20,120 receptors and pathway. Where are the sensors? 119 00:05:20,480 --> 00:05:21,800 And don't just say the heart. OK. 120 00:05:21,920 --> 00:05:25,320 Specifically, they are mechanoreceptors and 121 00:05:25,320 --> 00:05:28,760 chemoreceptors located within the left ventricular wall. 122 00:05:28,960 --> 00:05:31,120 Be more specific, which part of the wall? 123 00:05:31,360 --> 00:05:34,400 Primarily the infer posterior wall of the left ventricle. 124 00:05:34,400 --> 00:05:36,960 Correct. Now how does the signal get from 125 00:05:36,960 --> 00:05:39,160 that spot in the ventricle up to the brain? 126 00:05:39,200 --> 00:05:41,080 This is the specific phrase I have on my checklist. 127 00:05:41,080 --> 00:05:43,600 I'm waiting for it. The signal travels via the vagus 128 00:05:43,600 --> 00:05:47,760 nerve, but specifically it's carried along unmyelinated vagal 129 00:05:47,760 --> 00:05:52,640 A front type C fibers. Boom, there it is, unmyelinated 130 00:05:52,640 --> 00:05:54,680 C fibers. If you say those 3 words in the 131 00:05:54,680 --> 00:05:57,240 Viva, I can take a box. I know you understand the 132 00:05:57,240 --> 00:05:58,640 Physiology. Why does it matter that they're 133 00:05:58,640 --> 00:06:01,480 unmyelinated? Well, unmyelinated fibers 134 00:06:01,480 --> 00:06:04,160 usually imply a slower, more visceral type of transmission. 135 00:06:04,160 --> 00:06:06,000 It's not like sharp pain or somatic sensation. 136 00:06:06,000 --> 00:06:08,120 This is it's a deep distress signal. 137 00:06:08,400 --> 00:06:11,040 Correct. So this distress signal travels 138 00:06:11,080 --> 00:06:15,040 up the C fibers to the nucleus tractus solitarius, the NTS in 139 00:06:15,040 --> 00:06:17,360 the medulla. And then what happens? 140 00:06:17,360 --> 00:06:21,800 The NTS gets that signal and it it triggers a massive autonomic 141 00:06:21,800 --> 00:06:24,320 shift, it cranks up the parasympathetic tone. 142 00:06:24,320 --> 00:06:27,960 So the vagus nerve just hammers the SA node, which causes the 143 00:06:27,960 --> 00:06:30,880 bradycardia, right? And at the exact same time it 144 00:06:30,880 --> 00:06:34,000 causes a complete withdrawal of sympathetic tone from the blood 145 00:06:34,000 --> 00:06:35,120 vessels. It causes. 146 00:06:35,120 --> 00:06:39,560 Massive peripheral vasodilation. The vessels all go floppy, blood 147 00:06:39,560 --> 00:06:42,720 pools in the periphery, so you end up with this slow heart 148 00:06:42,720 --> 00:06:46,320 trying to pump into a completely dilated, boggy system. 149 00:06:46,560 --> 00:06:48,760 That's why the pressure crashes so profoundly. 150 00:06:48,800 --> 00:06:50,560 And the coronary dilation you mentioned earlier? 151 00:06:50,560 --> 00:06:53,560 That's part of the same process, a mix of sympathetic withdrawal 152 00:06:53,560 --> 00:06:56,400 and some direct vagal effects right on the coronary bed 153 00:06:56,400 --> 00:06:58,240 itself. OK, you've nailed the mechanism, 154 00:06:58,560 --> 00:07:02,640 but the bigger question is why evolution usually doesn't design 155 00:07:02,640 --> 00:07:05,600 suicide switches. Miller talks about a theory for 156 00:07:05,600 --> 00:07:09,040 the purpose of this reflex Why would the body want to shut the 157 00:07:09,040 --> 00:07:11,640 heart down when the pressure is already dangerously low? 158 00:07:11,760 --> 00:07:14,320 It's that hemorrhagic hibernation idea, or the 159 00:07:14,320 --> 00:07:18,280 cardioprotective theory. The logic is that if the heart 160 00:07:18,280 --> 00:07:22,000 is either ischemic or running on empty, beating faster is 161 00:07:22,000 --> 00:07:23,720 actually the most dangerous thing it can do. 162 00:07:23,720 --> 00:07:26,120 Go on. Tachycardia just consumes a 163 00:07:26,120 --> 00:07:29,520 massive amount of oxygen. If you're running on fumes, 164 00:07:29,520 --> 00:07:32,040 sprinting is what's going to kill the engine for good. 165 00:07:32,080 --> 00:07:35,640 Exactly so the BJR. The BJR acts like a circuit 166 00:07:35,640 --> 00:07:38,480 breaker. It senses that extreme stress, 167 00:07:38,480 --> 00:07:41,640 the ischemia or the violent squeezing of an empty chamber, 168 00:07:42,000 --> 00:07:44,000 and it forces the heart to slow down. 169 00:07:44,000 --> 00:07:47,800 It's basically screaming stop conserving of energy, dilate the 170 00:07:47,800 --> 00:07:50,120 coronaries, and just try to survive this insult. 171 00:07:50,360 --> 00:07:52,640 So it sacrifices the system to save the organ. 172 00:07:52,640 --> 00:07:55,680 Precisely, it sacrifices the systemic blood pressure to save 173 00:07:55,680 --> 00:07:58,800 the heart muscle itself. A desperate last ditch effort. 174 00:07:58,800 --> 00:08:01,680 Brilliant description. It sacrifices the Organism to 175 00:08:01,680 --> 00:08:04,880 save the organ. You might also see apnea 176 00:08:04,880 --> 00:08:07,160 mentioned in some textbooks, usually in animal models. 177 00:08:07,160 --> 00:08:10,240 But let's be clear, in clinical practice, it's the hemodynamic 178 00:08:10,240 --> 00:08:11,840 collapse that kills the patient. Right. 179 00:08:11,840 --> 00:08:13,560 Our focus is always on the circulation. 180 00:08:13,680 --> 00:08:16,640 Now let's move to the most important part for us, Section 181 00:08:16,640 --> 00:08:19,800 5, triggers and clinical scenarios. 182 00:08:20,240 --> 00:08:22,920 This is where you earn your MDI. Don't care about rats in the 183 00:08:22,920 --> 00:08:24,360 lab? I care about the patient on my 184 00:08:24,360 --> 00:08:27,800 operating table. When do we actually see this 185 00:08:27,800 --> 00:08:30,440 reflex? The Interscalen Block, Miller 186 00:08:30,440 --> 00:08:32,720 and Morgan are just full of warnings about this one, 187 00:08:33,320 --> 00:08:37,240 specifically when the surgery is done in the beach chair or 188 00:08:37,240 --> 00:08:40,039 sitting position. Walk me through it step by step. 189 00:08:40,760 --> 00:08:44,039 Why does a numb shoulder lead to a cardiac arrest? 190 00:08:44,159 --> 00:08:46,960 It's the perfect storm. First you put the patient in a 191 00:08:46,960 --> 00:08:49,960 sitting position. Gravity immediately pulls blood 192 00:08:49,960 --> 00:08:52,880 down into the legs. You get venous pooling, so 193 00:08:53,000 --> 00:08:56,040 venous return to the heart starts to drop, so the left 194 00:08:56,040 --> 00:08:59,320 ventricle becomes underfilled. At the same time, the patient is 195 00:08:59,320 --> 00:09:01,680 usually awake or just lightly sedated. 196 00:09:02,160 --> 00:09:04,400 They might be anxious so they have a high background 197 00:09:04,400 --> 00:09:07,160 sympathetic tone. Adrenaline is flowing. 198 00:09:07,160 --> 00:09:09,560 The heart is being told to beat hard and fast. 199 00:09:09,760 --> 00:09:11,800 But the chamber is empty. Exactly. 200 00:09:11,800 --> 00:09:14,360 It's hypercontractility against an empty chamber. 201 00:09:14,840 --> 00:09:17,440 The ventricular walls are literally squeezing and rubbing 202 00:09:17,440 --> 00:09:20,280 against each other. The mechanoreceptors embedded in 203 00:09:20,280 --> 00:09:22,120 the wall get crushed and squeezed. 204 00:09:22,120 --> 00:09:23,640 And they misinterpret that signal. 205 00:09:23,640 --> 00:09:25,640 Completely. They sense this violent 206 00:09:25,640 --> 00:09:28,560 squeezing and they think, wow, the pressure in here must be 207 00:09:28,560 --> 00:09:31,600 astronomical, even though the volume is critically low. 208 00:09:31,600 --> 00:09:34,640 So they fire the C fibers. They fire the afferent loop. 209 00:09:34,840 --> 00:09:37,560 The brain gets a false signal that the blood pressure is 210 00:09:37,560 --> 00:09:39,680 dangerously high. So what does it do? 211 00:09:39,960 --> 00:09:42,480 It triggers the BJR to lower the pressure. 212 00:09:42,480 --> 00:09:45,200 And the result. Massive vagal outflow. 213 00:09:45,320 --> 00:09:50,280 The heart rate drops to 30, then 20, then a systole lights out. 214 00:09:50,680 --> 00:09:53,400 And that right there is the empty heart theory. 215 00:09:53,960 --> 00:09:56,960 The Mccanna receptors are tricked by the empty squeeze. 216 00:09:57,440 --> 00:10:00,240 Now this brings us to the absolute favorite topic of the 217 00:10:00,240 --> 00:10:03,040 Gujarat University examiners. It's a guaranteed question. 218 00:10:04,000 --> 00:10:06,400 BJR in spinal anesthesia? Yes. 219 00:10:06,800 --> 00:10:08,840 This is the big trap. I know this one. 220 00:10:08,960 --> 00:10:11,280 It's a trap because it looks exactly like something else. 221 00:10:11,720 --> 00:10:14,280 So I'll give you the scenario. You're the resident on call. 222 00:10:14,400 --> 00:10:15,760 You give a spinal for a hip fracture. 223 00:10:15,760 --> 00:10:17,840 The level comes up to T6. It's a perfect block. 224 00:10:18,040 --> 00:10:20,160 Hemodynamics are rock solid. You relax. 225 00:10:20,400 --> 00:10:23,040 You start filling out the chart 20 minutes later. 226 00:10:23,440 --> 00:10:24,920 Not immediately, but 20 minutes later. 227 00:10:24,920 --> 00:10:28,520 The monitor alarms Heart rate 40, blood pressure 60 / 30. 228 00:10:28,520 --> 00:10:30,360 What happened? The knee jerk answer. 229 00:10:30,360 --> 00:10:33,040 The wrong answer is high spinal. And why is that the wrong 230 00:10:33,040 --> 00:10:35,880 answer? Because a true high spinal where 231 00:10:35,880 --> 00:10:38,640 you've actually blocked the cardio accelerator fibers at T1 232 00:10:38,640 --> 00:10:41,880 to T4, that usually happens early as the block is setting up 233 00:10:42,640 --> 00:10:45,360 and the mechanism there is just a passive loss of synthetic 234 00:10:45,360 --> 00:10:46,960 push. The heart slows down because 235 00:10:46,960 --> 00:10:50,840 it's gas pedal has been cut off. Correct, but in our scenario it 236 00:10:50,840 --> 00:10:53,800 happened 20 minutes later. The key is the delay. 237 00:10:53,880 --> 00:10:57,440 That's the signature of the BJR. The spinal anesthetic caused 238 00:10:57,440 --> 00:11:00,280 profound vasodilation in the legs in the abdomen. 239 00:11:00,840 --> 00:11:03,760 Over those 20 minutes, blood just slowly pooled. 240 00:11:04,520 --> 00:11:06,680 The central blood volume dropped and dropped. 241 00:11:06,680 --> 00:11:09,640 The ventricle got emptier and emptier until eventually it 242 00:11:09,640 --> 00:11:11,600 crossed a critical threshold. The empty heart. 243 00:11:11,600 --> 00:11:13,960 Threshold. Yes, the McCann receptors fired 244 00:11:13,960 --> 00:11:15,960 and the vagus nerve attacked the heart. 245 00:11:16,120 --> 00:11:18,720 The vagus nerve attacked. I like that phrasing. 246 00:11:18,880 --> 00:11:20,960 It implies an active aggressive process. 247 00:11:21,480 --> 00:11:24,000 In a high spinal, the sympathetic system is simply 248 00:11:24,000 --> 00:11:26,960 asleep. In the BJR, the parasympathetic 249 00:11:26,960 --> 00:11:28,640 system is wide awake and aggressive. 250 00:11:29,160 --> 00:11:31,520 That is the core distinction you must make to pass the Viva. 251 00:11:31,640 --> 00:11:35,560 So if the examiner asks, is the bradycardia in spinal anesthesia 252 00:11:35,560 --> 00:11:39,160 only due to a sympathetic block, the answer is a hard no. 253 00:11:39,160 --> 00:11:42,320 It's a combination, and in a delayed arrest it is almost 254 00:11:42,320 --> 00:11:44,280 certainly the BJR. Exactly. 255 00:11:44,440 --> 00:11:46,920 Now you've diagnosed it. Section 7 management. 256 00:11:47,320 --> 00:11:48,720 You're the anesthetist in the room. 257 00:11:48,840 --> 00:11:51,080 The patient is crashing. What do you do? 258 00:11:51,280 --> 00:11:52,920 Don't give me a long list. Give me protocol. 259 00:11:52,920 --> 00:11:56,080 OK, identify and act first. I know this isn't just simple 260 00:11:56,080 --> 00:12:00,760 hypotension, this is a collapse. So step one, restore preload 261 00:12:00,960 --> 00:12:02,400 immediately. Get their legs up. 262 00:12:02,440 --> 00:12:05,240 If they're in a beach chair, you dump the bed flat as fast as you 263 00:12:05,240 --> 00:12:07,160 can. I have to fill that empty heart 264 00:12:07,160 --> 00:12:08,920 to stop the mechanoreceptors from firing. 265 00:12:08,920 --> 00:12:10,320 That's the root cause. Good. 266 00:12:10,400 --> 00:12:11,920 What's next? Step 2. 267 00:12:13,440 --> 00:12:16,640 Fluids open the IV wide. You have to treat the volume 268 00:12:16,640 --> 00:12:18,560 deficit that started this whole cascade. 269 00:12:18,560 --> 00:12:19,520 OK. And drugs. 270 00:12:19,520 --> 00:12:22,200 Drugs, yes, atropine or glycopyrlate. 271 00:12:22,480 --> 00:12:25,240 I need to block that efrain vagal limb that's going to deal 272 00:12:25,240 --> 00:12:28,400 with the bradycardia. But the heart rate is 30, the BP 273 00:12:28,400 --> 00:12:30,720 is 50. Systolic atropine isn't working 274 00:12:30,720 --> 00:12:33,200 fast enough. What is the drug of choice 275 00:12:33,200 --> 00:12:35,800 according to Stolting in a severe collapse? 276 00:12:35,800 --> 00:12:38,680 In a severe collapse, it's epinephrine adrenaline. 277 00:12:38,840 --> 00:12:41,040 Why not ephedrine? We use ephedrine for spinal 278 00:12:41,040 --> 00:12:44,080 hypotension all the time. Because ephedrine is an indirect 279 00:12:44,080 --> 00:12:47,560 act agent, it works by making your own nerve endings release 280 00:12:47,560 --> 00:12:51,520 norepanifrin. But in a severe BJR or a high 281 00:12:51,520 --> 00:12:55,440 spinal, the sympathetic system is already completely shut down 282 00:12:55,440 --> 00:12:58,560 or exhausted. There's no norepinephrine left 283 00:12:58,560 --> 00:13:00,240 to squeeze out. So it's useless. 284 00:13:00,400 --> 00:13:02,480 Right, you need a direct agonist. 285 00:13:03,000 --> 00:13:06,160 Epinephrine hits the alpha and beta receptors directly. 286 00:13:06,160 --> 00:13:09,080 It completely bypasses the dysfunctional nerve ending, 287 00:13:09,080 --> 00:13:11,280 correct? Do not tickle the patient with 288 00:13:11,280 --> 00:13:15,520 ephedrine if they are dying. You give small repeated boluses 289 00:13:15,520 --> 00:13:18,600 of epinephrine, it restores the vascular tone and it directly 290 00:13:18,600 --> 00:13:20,920 kicks the heart rate up. And what about prevention? 291 00:13:21,160 --> 00:13:24,400 Prevention is everything so Co loading you have to be 292 00:13:24,400 --> 00:13:27,080 aggressive with hydration before or during the block. 293 00:13:27,400 --> 00:13:30,040 The key is to never let the heart get empty in the 1st place 294 00:13:30,280 --> 00:13:33,800 and be incredibly careful with sitting positions, especially in 295 00:13:33,800 --> 00:13:35,320 patients who might be dehydrated. 296 00:13:35,520 --> 00:13:37,680 Very good. You pass the BJR station. 297 00:13:37,920 --> 00:13:40,360 You know, the triad, the C fibers, the paradox, and the 298 00:13:40,360 --> 00:13:42,920 management. But the exam isn't over. 299 00:13:42,920 --> 00:13:45,520 Let's move to part C. Other important reflexes. 300 00:13:45,520 --> 00:13:48,640 We can't ignore them. Let's start with the I the 301 00:13:48,760 --> 00:13:53,840 ocular cardiac reflex OCR. Ah, the five and dime reflex. 302 00:13:53,840 --> 00:13:56,200 And what do we call it that? It's just a mnemonic for the 303 00:13:56,200 --> 00:13:57,560 cranial nerves that are involved. 304 00:13:57,560 --> 00:13:59,840 The afferent limb is the trigeminal nerve. 305 00:13:59,840 --> 00:14:05,000 That's cranial nerve 5 V and the effort limb is the vagus nerve, 306 00:14:05,000 --> 00:14:07,680 cranial nerve 10X5 and. Diamond. 307 00:14:07,680 --> 00:14:10,160 It's acute mnemonic, but I'm an examiner who likes details. 308 00:14:10,280 --> 00:14:13,320 Trace the path for me. OK, the stimulus is traction on 309 00:14:13,320 --> 00:14:15,920 the extra ocular muscles. The books say the medial rectus 310 00:14:15,920 --> 00:14:20,040 is the most potent trigger or direct pressure on the globe, 311 00:14:20,040 --> 00:14:22,560 like during a retrobulbar block or from trauma. 312 00:14:22,560 --> 00:14:25,040 And the signal goes where. The signal travels down the 313 00:14:25,040 --> 00:14:27,320 optomic division of the trigeminal nerve to the 314 00:14:27,320 --> 00:14:29,160 Gasserian ganglion. Keep going. 315 00:14:29,280 --> 00:14:30,840 Where does it connect in the brain stem? 316 00:14:31,080 --> 00:14:33,760 From there it goes to the main sensory nucleus of the 317 00:14:33,760 --> 00:14:36,560 trigeminal nerve, which is in the floor of the 4th ventricle. 318 00:14:36,920 --> 00:14:39,560 Yao and Artuzio is very specific about that point. 319 00:14:39,880 --> 00:14:43,680 Then it jumps across through interneurons to the vagomotor 320 00:14:43,680 --> 00:14:45,080 nucleus. And the result of all that 321 00:14:45,080 --> 00:14:48,160 wiring? Immediate profound bradycardia 322 00:14:48,480 --> 00:14:50,400 or worse. You can see AV block, 323 00:14:50,560 --> 00:14:53,320 ventricular ectopye, or it can go straight to a systole. 324 00:14:53,320 --> 00:14:56,240 It's like a light switch. If the surgeon pulls the muscle, 325 00:14:56,240 --> 00:14:59,280 the heart stops. They let go, it starts again. 326 00:14:59,320 --> 00:15:01,880 Which brings us to management. What is the very first thing you 327 00:15:01,880 --> 00:15:04,520 say in that situation? Stop, I tell the surgeon. 328 00:15:04,720 --> 00:15:07,200 Stop traction. Let go of the muscle. 329 00:15:07,560 --> 00:15:10,360 That is the single most effective treatment. 9 times out 330 00:15:10,360 --> 00:15:12,280 of 10, the rhythm returns immediately. 331 00:15:12,360 --> 00:15:14,280 And if it keeps happening every time they pull? 332 00:15:14,400 --> 00:15:16,320 Then I need to reassess my anesthetic. 333 00:15:16,480 --> 00:15:20,120 First I check my depth light anesthesia makes this reflex 334 00:15:20,120 --> 00:15:22,520 much worse. Then I check for hypoxia and 335 00:15:22,520 --> 00:15:24,920 hypercarbia. Both of those things will 336 00:15:24,920 --> 00:15:27,320 sensitize the heart to this vagal reflex. 337 00:15:27,800 --> 00:15:30,200 And if everything is perfect, deep and aesthetic, good 338 00:15:30,200 --> 00:15:33,360 ventilation and it's still happening, then I'll give a dose 339 00:15:33,360 --> 00:15:37,240 of atropine prophylactically. Good, now why do we see this so 340 00:15:37,240 --> 00:15:40,440 much more in kids? Strabisma surgery is a classic 341 00:15:40,440 --> 00:15:42,960 pediatric case. Because kids are vegatonic. 342 00:15:43,000 --> 00:15:45,440 They're resting. Parasympathetic tone is just 343 00:15:45,440 --> 00:15:48,840 much higher than in adults, and they really rely on their heart 344 00:15:48,840 --> 00:15:52,400 rate for their cardiac output, so for them a sudden drop in 345 00:15:52,400 --> 00:15:54,640 rate is hemodynamically devastating. 346 00:15:54,680 --> 00:15:56,800 Very true. Now, briefly, what about the 347 00:15:56,800 --> 00:16:00,120 variance mentioned in section 9? Ocular Pulmonary. 348 00:16:00,360 --> 00:16:02,600 Ocular gas. Right, it's the same trigger 349 00:16:02,600 --> 00:16:06,000 traction on the eye muscles, but the vagal output instead of just 350 00:16:06,120 --> 00:16:08,560 going to the heart, also goes to the lungs, causing 351 00:16:08,560 --> 00:16:12,080 bronchoconstriction, or to the stomach causing hypermotility 352 00:16:12,080 --> 00:16:13,920 and nausea. And the clinical relevance of 353 00:16:13,920 --> 00:16:15,680 that. It helps explain why these kids 354 00:16:15,680 --> 00:16:18,200 often wake up vomiting after strabisma surgery. 355 00:16:18,200 --> 00:16:20,840 It's not just the opioids or the anesthetic, it's the reflex 356 00:16:20,840 --> 00:16:23,280 itself kicking the stomach and making them feel sick. 357 00:16:23,280 --> 00:16:25,320 Excellent point. That's a distinction level 358 00:16:25,320 --> 00:16:27,640 insight. Now let's move down the anatomy, 359 00:16:27,720 --> 00:16:30,320 the airway, the laryngo cardiac reflex. 360 00:16:30,320 --> 00:16:32,880 This is our bread and butter. This is laryngoscopy and 361 00:16:32,880 --> 00:16:34,320 intubation. What's the pathway? 362 00:16:34,520 --> 00:16:38,160 The afferent is the Vegas or the glossopharyngeal nerve from 363 00:16:38,160 --> 00:16:40,440 direct irritation of the larynx or the trachea. 364 00:16:40,680 --> 00:16:43,040 The efferent again is the Vegas and the result? 365 00:16:43,120 --> 00:16:47,000 Bradycardia and hypotension. Again, Miller really emphasizes 366 00:16:47,000 --> 00:16:50,480 this is a pediatric issue. In adults, we usually see the 367 00:16:50,480 --> 00:16:53,040 opposite, right? We see a huge sympathetic surge 368 00:16:53,040 --> 00:16:56,880 from the pain of intubation. We get tachycardia and 369 00:16:56,880 --> 00:16:58,640 hypertension. But in a baby? 370 00:16:58,680 --> 00:17:02,120 But in a neonate, if you're too aggressive with the laryngoscope 371 00:17:02,120 --> 00:17:04,720 blade, they will Brady down on you in a second. 372 00:17:04,920 --> 00:17:07,599 Which is why we used to premedicate all children with 373 00:17:07,599 --> 00:17:10,560 atropine before induction. We don't do it routinely 374 00:17:10,560 --> 00:17:13,359 anymore, but that knowledge is always in the back of our minds. 375 00:17:13,760 --> 00:17:17,839 What is the absolute number one rule for pediatric bradycardia? 376 00:17:17,920 --> 00:17:20,480 Hypoxia until proven otherwise. See you again. 377 00:17:20,720 --> 00:17:23,240 If a child has bradycardia, it is hypoxia. 378 00:17:23,240 --> 00:17:25,400 Period. It's not the reflex, it's not 379 00:17:25,400 --> 00:17:28,800 the drug, it's lack of oxygen. Check the tube position, check 380 00:17:28,800 --> 00:17:32,160 the circuit, check their color. Only after you have definitively 381 00:17:32,160 --> 00:17:34,880 ruled out hypoxia can you start blaming a reflex. 382 00:17:34,880 --> 00:17:38,960 Yeah, never, ever forget that. Now let's move to the neck, the 383 00:17:38,960 --> 00:17:41,840 carotid sinus reflex. OK, this is a pure bear receptor 384 00:17:41,840 --> 00:17:43,600 reflex. Where are the sensors? 385 00:17:43,800 --> 00:17:46,680 They're in the carotid sinus, which is a little bulge right at 386 00:17:46,680 --> 00:17:49,080 the bifurcation of the internal carotid artery. 387 00:17:49,280 --> 00:17:51,400 They're stretch receptors. In the avrin nerve. 388 00:17:51,560 --> 00:17:54,680 It's Herring's nerve, which is a branch of the glossopharyngeal 389 00:17:54,680 --> 00:17:55,720 cranial nerve. IX. 390 00:17:56,240 --> 00:17:59,520 Good name. Drop Herring's nerve and the 391 00:17:59,520 --> 00:18:02,160 response it generates. Well, its job is to regulate 392 00:18:02,160 --> 00:18:05,520 blood pressure second by second. If the systemic pressure is 393 00:18:05,520 --> 00:18:08,840 high, the sinus stretches, herrings, nerve fires. 394 00:18:09,400 --> 00:18:12,400 The brain then inhibits the vasoconstrictor center and 395 00:18:12,400 --> 00:18:16,080 excites the vagal center. The result is vasodilation and 396 00:18:16,080 --> 00:18:18,080 bradycardia to bring the pressure back down. 397 00:18:18,240 --> 00:18:19,600 And the clinical relevance for us? 398 00:18:19,600 --> 00:18:22,560 Neck surgery, especially carotid indoorterectomy. 399 00:18:22,840 --> 00:18:25,600 If the surgeon is dissecting around that carotid bifurcation, 400 00:18:25,600 --> 00:18:28,000 they can put pressure on the sinus and trick it into thinking 401 00:18:28,000 --> 00:18:31,520 the pressure is 2100 and boom, boom, sudden profound 402 00:18:31,520 --> 00:18:35,280 hypotension and bradycardia. Also, Miller makes a point that 403 00:18:35,280 --> 00:18:38,960 our volatile anesthetics like isoflurine actually depress this 404 00:18:38,960 --> 00:18:41,560 reflex. So under general anesthesia, 405 00:18:41,560 --> 00:18:44,360 patients can't compensate for blood pressure swings as well as 406 00:18:44,360 --> 00:18:46,120 they can when they're awake. Correct. 407 00:18:46,960 --> 00:18:48,680 OK, now let's go inside the skull. 408 00:18:49,080 --> 00:18:52,360 The Cushing reflex. This one is the Grim Reaper of 409 00:18:52,360 --> 00:18:54,480 reflexes. Yeah, this is a sign of 410 00:18:54,480 --> 00:18:57,240 impending doom. It's the body's last ditch 411 00:18:57,240 --> 00:19:00,840 physiological response to dangerously high intracranial 412 00:19:00,840 --> 00:19:02,800 pressure. Give me the triad, the Cushing 413 00:19:02,800 --> 00:19:05,640 triad. Hypertension, bradycardia, and 414 00:19:05,640 --> 00:19:08,000 irregular respiration. Walk me through the mechanism. 415 00:19:08,240 --> 00:19:10,560 Why on earth does the blood pressure skyrocket? 416 00:19:10,600 --> 00:19:14,080 OK, so you have a bleed or a tumor or swelling inside the 417 00:19:14,080 --> 00:19:16,880 skull. The ICP starts to rise of 418 00:19:16,960 --> 00:19:19,200 essentially the pressure inside the skull gets higher than the 419 00:19:19,200 --> 00:19:23,000 mean arterial pressure. The blood vessels inside the 420 00:19:23,000 --> 00:19:25,760 brain get squashed flat. So blood can't get in. 421 00:19:26,000 --> 00:19:28,160 Exactly. The brain starts to suffocate. 422 00:19:28,160 --> 00:19:31,400 Cerebral ischemia. The brain stem is starving for 423 00:19:31,400 --> 00:19:32,800 oxygen. And the brain panics. 424 00:19:32,800 --> 00:19:35,560 It absolutely panics. It activates what Guyton calls 425 00:19:35,560 --> 00:19:38,640 the CNS ischemic response. It initiates a massive, 426 00:19:38,640 --> 00:19:41,560 overwhelming sympathetic outflow to the entire body. 427 00:19:42,080 --> 00:19:44,720 It clamps down on every peripheral blood vessel it can 428 00:19:44,720 --> 00:19:46,880 find. It's trying to force the system 429 00:19:47,120 --> 00:19:49,880 blood pressure up to make it higher than the intracranial 430 00:19:49,880 --> 00:19:52,720 pressure. It's a brute force attempt to 431 00:19:52,720 --> 00:19:55,560 restore its own blood flow. That's what causes the severe 432 00:19:55,560 --> 00:19:57,360 hypertension. OK, that explains the 433 00:19:57,360 --> 00:20:00,040 hypertension, but why the bradycardia? 434 00:20:00,440 --> 00:20:03,080 Because the bear receptors in the aorta and the carotid are 435 00:20:03,080 --> 00:20:06,080 still sitting there doing their job, they see the systemic blood 436 00:20:06,080 --> 00:20:10,600 pressure hit 2/21/20 and they scream way too high and they try 437 00:20:10,600 --> 00:20:13,520 to lower it by slowing the heart down via the vagus nerve. 438 00:20:13,680 --> 00:20:15,320 So you get this physiological war. 439 00:20:15,400 --> 00:20:18,000 Exactly. The brain Brain is desperately 440 00:20:18,000 --> 00:20:20,800 trying to drive the pressure up to save itself, and the body's 441 00:20:20,800 --> 00:20:23,920 baroreceptors are desperately trying to bring it down to save 442 00:20:23,920 --> 00:20:26,720 the system. The bradycardia is the result of 443 00:20:26,720 --> 00:20:29,000 that conflict. A terrible, futile war. 444 00:20:29,680 --> 00:20:33,280 If you see this triad in a head trauma patient in the ER, what 445 00:20:33,280 --> 00:20:35,520 does it mean? It means herniation is imminent, 446 00:20:35,520 --> 00:20:38,880 the brain stem is being crushed. You need to hyperventilate them, 447 00:20:38,880 --> 00:20:41,720 give them manitol, call the neurosurgeon and get them to 448 00:20:41,720 --> 00:20:44,480 drill a hole immediately. It is a true neurosurgical 449 00:20:44,480 --> 00:20:46,280 emergency. OK, one last quick one. 450 00:20:46,520 --> 00:20:48,840 The vagavogal reflex. This one's simple. 451 00:20:48,840 --> 00:20:52,080 Vegas in, Vegas out. Usually peritoneal stretching. 452 00:20:52,080 --> 00:20:54,920 The classic example is the insufflation of gas during 453 00:20:54,920 --> 00:20:57,040 laparoscopy. The surgeon inflates the 454 00:20:57,040 --> 00:20:59,160 abdomen, the peritonium gets stretched. 455 00:20:59,360 --> 00:21:02,520 That sends a signal up the Vegas and the heart slows down. 456 00:21:02,520 --> 00:21:04,960 Simple enough. Now, Doctor, we're moving into 457 00:21:04,960 --> 00:21:06,960 Part D comparison and integration. 458 00:21:07,280 --> 00:21:10,360 This is where I separate the past students from the gold 459 00:21:10,360 --> 00:21:12,840 medalists. I want you to visualize a table 460 00:21:12,840 --> 00:21:14,400 in your mind. OK, I'm visualizing it. 461 00:21:14,640 --> 00:21:17,880 Column one is the stimulus, column two is the response. 462 00:21:18,120 --> 00:21:23,120 I want you to compare 3 reflexes for me, BJR, the Bear receptor 463 00:21:23,120 --> 00:21:25,360 reflex and the Bainbridge reflex. 464 00:21:25,720 --> 00:21:27,760 The Bainbridge reflex. OK, that's the tricky. 465 00:21:27,760 --> 00:21:29,880 One it is to find it first. We haven't touched on it yet. 466 00:21:30,080 --> 00:21:33,040 The Bainbridge reflex is essentially the reverse of the 467 00:21:33,040 --> 00:21:35,280 BJR. It's triggered not by low 468 00:21:35,280 --> 00:21:38,840 volume, but by high volume. It's the stretch receptors in 469 00:21:38,840 --> 00:21:41,840 the Atria that sense that the heart is being overfilled. 470 00:21:41,840 --> 00:21:43,240 What's the response to that overfilling? 471 00:21:43,960 --> 00:21:46,320 Tachycardia. The heart speeds up to try and 472 00:21:46,320 --> 00:21:49,240 pump that extra fluid forward. It's a mechanism to prevent 473 00:21:49,240 --> 00:21:51,600 blood from damming up in the venous system. 474 00:21:51,600 --> 00:21:53,520 Good, so let's build that table biz. 475 00:21:53,520 --> 00:21:57,680 Old gerish reflex stimulus is low volume. 476 00:21:57,880 --> 00:22:01,960 The empty heart response is bradycardia now. 477 00:22:02,280 --> 00:22:05,800 Bainbridge reflex stimulus. High volume and overfilled 478 00:22:05,800 --> 00:22:07,320 heart. Response. 479 00:22:07,360 --> 00:22:08,640 Tachycardia. Good. 480 00:22:08,760 --> 00:22:10,800 Now boroceptor reflex stimulus is what? 481 00:22:10,880 --> 00:22:13,440 Stimulus is a change in pressure, not volume, so let's 482 00:22:13,440 --> 00:22:15,520 say low pressure. And the response to low 483 00:22:15,520 --> 00:22:16,640 pressure. Tachycardia. 484 00:22:16,640 --> 00:22:18,360 Excellent. Now synthesize that for me. 485 00:22:18,360 --> 00:22:19,520 This is where it gets really interesting. 486 00:22:19,600 --> 00:22:22,680 Let's say I start to hemorrhage. I have a low volume and low 487 00:22:22,680 --> 00:22:25,400 pressure. Which reflex wins? 488 00:22:25,480 --> 00:22:28,840 This is the cool part initially as you bleed the bearer 489 00:22:28,840 --> 00:22:30,160 receptor. Reflex wins. 490 00:22:30,600 --> 00:22:33,600 The drop in pressure causes a compensatory tachycardia. 491 00:22:33,880 --> 00:22:36,560 That's what we see first. But if the hemorrhage is severe 492 00:22:36,560 --> 00:22:39,480 enough, if the volume loss becomes so critical that the 493 00:22:39,480 --> 00:22:42,920 ventricle starts to run empty and the BJR takes over, it 494 00:22:42,920 --> 00:22:45,360 overrides the baroreceptor reflex and the heart rate 495 00:22:45,360 --> 00:22:47,600 suddenly crashes. That's the terminal event. 496 00:22:47,760 --> 00:22:50,520 Brilliant synthesis. They're opposing forces and the 497 00:22:50,520 --> 00:22:52,840 BJR is the last desperate one to fire. 498 00:22:54,040 --> 00:22:56,240 Now a final Viva question for this section. 499 00:22:56,280 --> 00:22:59,360 A structured answer please. Doctor, you're in the OR. 500 00:22:59,360 --> 00:23:02,720 Your patient's heart rate is 40. List the differential diagnosis. 501 00:23:02,720 --> 00:23:04,520 Don't just ramble. Give me categories, OK? 502 00:23:04,800 --> 00:23:07,120 I would use the examiner safe structure. 503 00:23:07,200 --> 00:23:09,800 My category. My categories would be good 11 504 00:23:09,920 --> 00:23:12,800 Reflex mediated. Is the surgeon pulling on the 505 00:23:13,080 --> 00:23:16,200 eye OCR? Is the abdomen being insufflated 506 00:23:16,200 --> 00:23:20,120 vagovigal or is the heart empty from bleeding or venous bowling 507 00:23:20,240 --> 00:23:23,440 BJR? Good category 2. 2 drug induced 508 00:23:23,440 --> 00:23:26,600 did I just give a big bolus of fentanyl or Remi fentanyl? 509 00:23:26,840 --> 00:23:29,080 Did I give a high dose of exmitotomidine? 510 00:23:29,240 --> 00:23:31,240 Did I repeat a dose of succinylcholine? 511 00:23:31,240 --> 00:23:34,080 Especially in a child. Excellent category 3. 3 512 00:23:34,080 --> 00:23:37,240 Physiological and at the top of this list always is hypoxia, 513 00:23:37,240 --> 00:23:41,160 especially in a child, then a high spinal blocking T1T4. 514 00:23:41,200 --> 00:23:44,240 And the last one. 4 Surgical Is the surgeon physically 515 00:23:44,240 --> 00:23:46,640 manipulating or compressing the vagus nerve in the neck or 516 00:23:46,640 --> 00:23:48,240 chest? Direct stimulation. 517 00:23:48,440 --> 00:23:51,880 That is a rock solid, safe and comprehensive answer. 518 00:23:52,400 --> 00:23:53,880 It covers the common and the deadly. 519 00:23:54,560 --> 00:23:56,800 Now Part E final exam integration. 520 00:23:56,800 --> 00:23:58,840 Let's quickly review the common Viva traps. 521 00:23:58,960 --> 00:24:03,400 Trap number one, I ask you, why did the patient arrest after the 522 00:24:03,400 --> 00:24:05,600 spinal was working perfectly for 20 minutes? 523 00:24:06,040 --> 00:24:09,440 The answer is it's the BJR triggered by progressive venous 524 00:24:09,440 --> 00:24:11,200 pooling leading to the empty heart state. 525 00:24:11,520 --> 00:24:14,600 The delay is the clue. Perfect trap #2 is the 526 00:24:14,600 --> 00:24:17,760 bradycardia seen in spinal anesthesia only due to the 527 00:24:17,760 --> 00:24:20,120 sympathetic blockade. Answer No. 528 00:24:20,440 --> 00:24:24,200 It is a combination of the direct sympathetic block at T1T4 529 00:24:24,200 --> 00:24:28,120 if the spinal is high and D the active reflex vagal activity 530 00:24:28,120 --> 00:24:30,440 from the BJR if venous return is poor. 531 00:24:30,560 --> 00:24:32,000 Exactly. Trap number 3A. 532 00:24:32,000 --> 00:24:34,720 More subtle one. How does the Valsalva maneuver 533 00:24:34,720 --> 00:24:36,600 relate to all this? Miller mentions this. 534 00:24:37,080 --> 00:24:40,320 A sustained Valsalva maneuver increases intrathoracic pressure 535 00:24:40,320 --> 00:24:43,280 which dramatically decreases venous return, so it can mimic 536 00:24:43,280 --> 00:24:46,520 the empty heart Physiology and trigger similar baroreceptor and 537 00:24:46,520 --> 00:24:48,440 BJR like changes. Very good. 538 00:24:48,440 --> 00:24:49,880 You're anticipating the curveballs now. 539 00:24:49,880 --> 00:24:52,560 Section 17 diagrams. You have 10 minutes left in your 540 00:24:52,560 --> 00:24:54,360 theory paper. You need to draw the BJR 541 00:24:54,360 --> 00:24:55,720 pathway. What do you put on the paper? 542 00:24:55,960 --> 00:24:58,160 OK, simple as best. I draw a heart. 543 00:24:58,600 --> 00:25:02,080 I labeled the left ventricle and right mechanoreceptor schema 544 00:25:02,080 --> 00:25:04,520 receptors on the infer posterior wall. 545 00:25:05,120 --> 00:25:07,880 From there I draw a line going up to the brain stem. 546 00:25:08,080 --> 00:25:11,840 I label that line unmyelinated C fibers afferent. 547 00:25:11,880 --> 00:25:14,360 Keywords. Good in the brain stem I draw a 548 00:25:14,360 --> 00:25:18,600 box and label it NTS in medulla. Then I draw 2 lines coming out. 549 00:25:18,600 --> 00:25:21,560 One goes back to the hearts essay node and I label it vagus 550 00:25:21,560 --> 00:25:23,960 nerve vadycardia. The other line goes to the 551 00:25:23,960 --> 00:25:26,920 peripheral blood vessels, and I label it sympathetic withdrawal, 552 00:25:27,120 --> 00:25:29,840 vasodilation, hypotension. And at the bottom. 553 00:25:30,040 --> 00:25:33,320 At the bottom I write the triad in big bold letters. 554 00:25:33,560 --> 00:25:36,440 Hypotension, Bradycardia, Coronary dilation. 555 00:25:36,880 --> 00:25:38,920 Perfect. A clear, simple diagram like 556 00:25:38,920 --> 00:25:41,200 that is worth 1000 words of messy handwriting. 557 00:25:41,520 --> 00:25:43,960 So let's summarize this entire deep dive give you the final 558 00:25:43,960 --> 00:25:46,560 take home exam points. This is the CHEAT SHEET you read 559 00:25:46,560 --> 00:25:48,120 right before you walk into the exam hall. 560 00:25:48,120 --> 00:25:51,640 OK, the high yield recap. BJR definition is the triad 561 00:25:52,040 --> 00:25:54,840 hypotension plus bradycardia plus coronary dilation. 562 00:25:55,080 --> 00:25:57,520 Receptors are in the left ventricle, specifically the 563 00:25:57,520 --> 00:26:00,600 inferior wall. Afrin pathway is unmyelinated. 564 00:26:00,600 --> 00:26:04,640 C fibers say it over and over. Key triggers inferior wall MI, 565 00:26:04,640 --> 00:26:07,600 the interscaling block in the sitting position, and spinal 566 00:26:07,600 --> 00:26:09,520 anesthesia causing an empty heart. 567 00:26:09,560 --> 00:26:11,720 Good. Keep going. 5 The spinal 568 00:26:11,720 --> 00:26:14,640 mechanism is not just a sympathetic block, it's an 569 00:26:14,640 --> 00:26:17,520 active vagal reflex due to an empty ventricle. 570 00:26:17,600 --> 00:26:22,320 Treatment fluids first, preload is king, then epinephrine as the 571 00:26:22,320 --> 00:26:25,240 drug of choice for collapse. Atropine for the vagal 572 00:26:25,240 --> 00:26:28,040 component. OCR triggered by traction on the 573 00:26:28,040 --> 00:26:31,040 medial rectus cranial nerve 5 inches 10 out. 574 00:26:31,720 --> 00:26:33,680 First action is to tell the surgeon to stop. 575 00:26:33,760 --> 00:26:37,400 Cushing's triad. High ICP leads to high BP and 576 00:26:37,400 --> 00:26:39,480 low heart rate. It's a sign of impending 577 00:26:39,480 --> 00:26:41,600 herniation. Bainbridge is the opposite of 578 00:26:41,600 --> 00:26:43,440 BJR. High volume leads to 579 00:26:43,440 --> 00:26:44,880 tachycardia. You're ready. 580 00:26:45,000 --> 00:26:46,720 That is a distinction level performance. 581 00:26:46,720 --> 00:26:49,240 You didn't just memorize the names of the reflexes, you 582 00:26:49,240 --> 00:26:51,520 understood the logic of the sensors in the pathways. 583 00:26:51,520 --> 00:26:53,640 Thank you professor. Honestly, it feels less like 584 00:26:53,640 --> 00:26:56,800 some terrifying magic now and more more like plumbing and 585 00:26:56,800 --> 00:26:58,520 wiring. That is precisely what 586 00:26:58,520 --> 00:27:01,240 anaesthesia is. It's applied Physiology in real 587 00:27:01,240 --> 00:27:03,760 time. These reflexes, you see, they 588 00:27:03,760 --> 00:27:06,440 aren't actually trying to kill the patient, they're trying to 589 00:27:06,440 --> 00:27:08,640 save them, just in a very primitive way. 590 00:27:08,640 --> 00:27:11,720 The BJR tries to save the heart muscle from ischemia. 591 00:27:12,040 --> 00:27:15,040 The Cushing reflex tries to save the brain from starvation. 592 00:27:15,160 --> 00:27:18,080 But in the highly artificial environment of the operating 593 00:27:18,080 --> 00:27:21,000 room, those primitive survival attempts can be lethal. 594 00:27:21,120 --> 00:27:22,600 Correct. Which brings us to our 595 00:27:22,600 --> 00:27:23,960 philosophical outro. Right. 596 00:27:24,440 --> 00:27:27,680 We spend our entire careers fighting these reflexes. 597 00:27:28,280 --> 00:27:31,320 The BJR is nature's way of saying the heart is tired and 598 00:27:31,320 --> 00:27:33,840 ischemic, let it rest. And we come in and say 599 00:27:33,840 --> 00:27:36,960 absolutely not, you're going to pump harder and here's a syringe 600 00:27:36,960 --> 00:27:38,360 full of adrenaline to make you do it. 601 00:27:38,560 --> 00:27:40,840 It is a fundamental paradox of our specialty. 602 00:27:40,840 --> 00:27:43,280 So the provocative question for you, the listener, to think 603 00:27:43,280 --> 00:27:46,760 about is this. If the Bezel Jarish Reflex is an 604 00:27:46,760 --> 00:27:49,800 evolutionary masterpiece perfected over millions of years 605 00:27:49,800 --> 00:27:53,200 to protect a dying heart, are we arrogant to so aggressively 606 00:27:53,200 --> 00:27:55,320 abolish it? Or is the operating room a 607 00:27:55,320 --> 00:27:57,920 unique place in the universe where the laws of nature and 608 00:27:57,920 --> 00:28:00,280 evolution are suspended by the tip of a needle? 609 00:28:00,360 --> 00:28:03,520 That is a fine question for the coffee room after the case, but 610 00:28:03,520 --> 00:28:07,000 for the exam, treat the hypertension, save the patient 611 00:28:07,000 --> 00:28:08,160 on the table. Deal. 612 00:28:08,520 --> 00:28:11,320 Treat the patient first, pass the exam and then debate the 613 00:28:11,320 --> 00:28:13,600 philosophy later. Good luck to everyone sitting 614 00:28:13,600 --> 00:28:17,280 for the Gujarat University MD exams and any other anesthesia 615 00:28:17,280 --> 00:28:19,920 exam. Keep your heads cool and your 616 00:28:19,920 --> 00:28:22,800 atropine and epinephrine ready. Thanks for listening to this 617 00:28:22,800 --> 00:28:24,280 deep dive. We'll see you next time.