Warm, Bradycardic, and in Shock: Picking the Right Pressor
A high cervical injury has left this patient's heart too slow and his vessels too wide open, a combination the most reflexively reached-for pressor doesn't actually treat.
H.G., a 52-year-old electrician, was cleaning gutters from a ladder that shifted, and landed in a way that fractured and dislocated his fourth cervical vertebra, leaving him with complete tetraplegia below the level of injury. His vitals tell a story that could be mistaken for hemorrhage at a glance — heart rate 48, blood pressure 78/42 — except for the one exam finding that rules that reading out immediately: his extremities are warm and well-perfused, not cool and clammy, and his trauma workup found no evidence of bleeding. This is neurogenic shock, produced by the sympathectomy his high cervical injury caused, not hypovolemic shock, and the distinction matters directly to which drug fixes it, because the physiology driving his numbers is the opposite of what a reflexive resuscitation instinct usually expects.
Neurogenic shock combines two problems a single pure vasoconstrictor doesn't fully address: profound vasodilation from lost sympathetic tone below the injury, and bradycardia from unopposed vagal (parasympathetic) input once the sympathetic chain that would normally counter it is disrupted. Phenylephrine, a pure alpha-1 agonist, corrects the vasodilation directly, but it does nothing for the bradycardia and can worsen it further through a reflex baroreceptor response to the sudden pressure rise — exactly the wrong direction in a patient whose heart rate is already 48. Norepinephrine and dopamine both combine alpha-mediated vasoconstriction with beta-1 activity that supports heart rate and contractility, addressing both halves of his physiology through a single agent rather than treating the vasodilation while leaving the bradycardia to worsen. His preserved diaphragmatic function, still intact but requiring close monitoring at this injury level, is a separate concern from the pressor decision, but the same instinct toward doing this precisely rather than reflexively applies to watching it just as closely.
Not the shock the resuscitation reflex expects
Phenylephrine is what I reach for in undifferentiated shock, and I'd defend it here with one addition: pair it with glycopyrrolate and you have covered both halves — vasoconstriction for the dilation, vagolysis for the rate. Those are two drugs I can push right now through the line he already has, while norepinephrine means a pump, a dilution, and a conversation about central access on a man we are still logrolling for his spine.
That pairing treats his numbers and not his lesion. The bradycardia isn't a vagal surge you block once — it is the absence of sympathetic outflow below a C4 injury, and it will still be absent in an hour when the glycopyrrolate has worn off and you are pushing another dose. Meanwhile phenylephrine raises afterload against a heart that has lost its own inotropic drive, and the baroreceptor response to that pressure rise pushes his rate down again, so you are chasing your own drug. Norepinephrine's beta-1 activity replaces continuously what the injury removed, which is the actual shape of the problem — and it runs peripherally to start, so the access argument doesn't hold either.
I'd resist treating norepinephrine as the obvious landing point, though. Dopamine is the other mixed-acting agent, and its chronotropic effect at the doses used here is the stronger of the two — in a man whose rate is 48 and whose pressure is largely a consequence of that rate, the chronotropy is the deficit doing the most work. What argues against it is tachyarrhythmia — De Backer's SOAP II trial found significantly more arrhythmic events on dopamine than norepinephrine across a general shock population, which is why practice moved — and that population was not this one, so we would be importing a lesson learned somewhere else. Norepinephrine first, on titratability and on what this team runs every day — but dopamine named now as the agent to move to if his rate rather than his pressure stays the limiting problem, which is a different and better reason to reach for it than waiting for norepinephrine to fail.
Norepinephrine brought his blood pressure to a MAP of 80 within twenty minutes, with his heart rate rising to the low 60s as the beta-1 component took effect. Dopamine was never needed; his response to norepinephrine alone was adequate throughout his ICU course.
The emergency physician's initial reflex toward phenylephrine, caught and corrected before it was ever given, became something the team returned to directly afterward — not as a mistake, since it was set aside before affecting care, but as a genuine teaching point about how a common shock-resuscitation default doesn't map onto every physiology it gets reached for.