Questions · Vasopressor Choice for Spinal Hypotension
9 questions, 0 approved. Approve them one at a time — a quiz shows nothing you have not.
Recall — derived from a kept point
State the approximate equipotent dose relationship between norepinephrine and phenylephrine for treating spinal hypotension, and the practical consequence for dosing.
Answer: Norepinephrine 8 micrograms is about equivalent to phenylephrine 100 micrograms, a potency ratio near 13 to 1, so the two drugs cannot be swapped at the same numerical dose.
Roughly 13 to 1 — if you carry a phenylephrine microgram number over to norepinephrine, you are an order of magnitude off.
Source claim: Norepinephrine 8 micrograms is about equivalent to phenylephrine 100 micrograms, a potency ratio near 13 to 1, so the two cannot be swapped at the same numerical dose.
A Random-Allocation Graded Dose-Response Study of Norepinephrine and Phenylephrine for Treating Hypotension During Spinal Anesthesia for Cesarean Delivery, Anesthesiology 2017
recall · CA-1 · phrased by llm
Comparing norepinephrine and phenylephrine given by infusion during spinal anaesthesia, describe how they compare for systolic pressure control and for heart rate, cardiac output, systemic vascular resistance and bradycardia.
Answer: Given by infusion, norepinephrine held systolic pressure as well as phenylephrine, but with a higher heart rate and cardiac output, a lower systemic vascular resistance, and less bradycardia.
Both agents defend the systolic pressure — the difference is what sits behind it, with norepinephrine preserving more heart rate and cardiac output and less bradycardia.
Source claim: Given by infusion, norepinephrine held systolic pressure as well as phenylephrine but with a higher heart rate and cardiac output, lower systemic vascular resistance and less bradycardia.
Randomized Double-Blinded Comparison of Norepinephrine and Phenylephrine for Maintenance of Blood Pressure During Spinal Anesthesia for Cesarean Delivery, Anesthesiology 2015
recall · CA-2 · phrased by llm
You give phenylephrine for hypotension. Describe its effect on blood pressure and cardiac output, and what happens to cerebral blood flow and to cerebral tissue oxygen saturation.
Answer: Phenylephrine raises blood pressure while lowering cardiac output, and although it increases cerebral blood flow it decreases cerebral tissue oxygen saturation.
A better cuff number and even a higher cerebral blood flow can still come with a fall in cerebral tissue oxygen saturation — the pressure is not the tissue.
Source claim: Phenylephrine raises blood pressure while lowering cardiac output, and although it increases cerebral blood flow it decreases cerebral tissue oxygen saturation.
Effects of Phenylephrine on Systemic and Cerebral Circulations in Humans: A Systematic Review With Mechanistic Explanations, Anaesthesia 2024
recall · CA-2 · phrased by llm
A network meta-analysis of 109 trials ranked strategies for preventing post-spinal hypotension. Which agents ranked most effective, what did it find about crystalloid given before induction, and what feature of the included trials limits how directly you can apply the ranking to a patient having a knee replacement?
Answer: Metaraminol, norepinephrine and phenylephrine were the most effective at preventing hypotension, and crystalloid given before induction was no better than control. All 109 trials were of spinal anaesthesia for caesarean section, so the ranking comes from an obstetric population rather than from non-obstetric surgical patients.
The vasopressor ranking is strong, but it is obstetric data — and note that in it, crystalloid before induction did not beat control.
Source claim: Ranked across 109 trials of spinal anaesthesia for caesarean section, metaraminol, norepinephrine and phenylephrine were the most effective at preventing hypotension, while crystalloid given before induction was no better than control.
Prevention of Hypotension After Spinal Anaesthesia for Caesarean Section: A Systematic Review and Network Meta-Analysis of Randomised Controlled Trials, Anaesthesia 2020
recall · CA-3 · phrased by llm
Using equipotent boluses, bradycardia occurred in ___% with norepinephrine 6 micrograms versus 38% with phenylephrine 100 micrograms, and fewer patients needed rescue ephedrine.
Answer: 11
Using equipotent boluses, bradycardia occurred in 11% with norepinephrine 6 micrograms versus 38% with phenylephrine 100 micrograms, and fewer patients needed rescue ephedrine.
Comparison of Intermittent Intravenous Boluses of Phenylephrine and Norepinephrine to Prevent and Treat Spinal-Induced Hypotension in Cesarean Deliveries: Randomized Controlled Trial · PMID 30113395
recall · CA-2 · phrased by derived
The point with one number taken out. No model wrote any of this: the stem is the sentence you reviewed, minus a digit, and the paper it came from is named beneath it.
Open prompts
How does your plan change if the patient is not optimised?
open · CA-2 · phrased by derived
What is the physiology behind what we just did?
open · CA-2 · phrased by derived
Talk me through the trade-off you made there.
open · CA-2 · phrased by derived
What would make you abandon this plan and do something else?
open · CA-2 · phrased by derived
Questions only — nothing here asserts anything, which is why a model is allowed to phrase them. Where no model was reachable these are the level defaults.