Critically ill patients will often “crump” following intubation. Why? There are various reasons, but probably the most common is that they are under-resuscitated to begin with. This is almost always in patients requiring emergent intubations. These patients are likely hemodynamically fragile and volume depleted. Intubation causes major hemodynamic changes, and it’s not all just because of the drugs we give. Normally, we breathe via negative pressure; the diaphragm moves down and decreases the intrathoracic pressure, sucking air into the lungs.
When we intubated a patient, we switch that over to a positive pressure process; the ventilator pushes air into the lungs. This increases the intrathoracic pressure, which, in a hypovolemic patient, can result in hemodynamic collapse. Add to that that we’ve paralyzed them and taken away their ability to respond to this sudden change (not to mention the potentially hypotensive effects of sedatives) and you can see why these people fall apart. But, it’s rarely sudden and usually totally predictable.
When time allows (and it almost always allows), resuscitate these patients before intubating them. But, don’t blindly flood people with fluid. A quick bedside echo can determine if they’re hypovolemic (and also evaluate their RV status, which is important before we intubate someone). In this great Instagram post, Obiajulu Anozie mentions using the Shock Index to evaluate patients as well. If you’re not familiar with the Shock Index, you just divide the heart rate by the SBP. A value ≥ 0.9 is indicative of need for further resuscitation. This is helpful if you find yourself without access to an ultrasound for some reason.
critical care notes 