Vasopressors and inotropes: choosing and titrating
Stem
A 74-year-old woman, 68 kg, with hypertension on lisinopril (taken this morning) and an ischemic cardiomyopathy with an ejection fraction of 30%, is having a total hip arthroplasty under general anesthesia with sevoflurane. Fifteen minutes after induction, before incision, her blood pressure is 70/40 and heart rate 56 in sinus rhythm. End-tidal CO2 is 32 mmHg and pulse-pressure variation is 9%.
Question
The pressure is 70/40. What are you going to give, and why?
Ideal answer
HeadlineVasodilation from the anesthetic on top of this morning's ACE inhibitor, with a slow rate: ephedrine 5–10 mg boluses and less sevoflurane.
- I name the failed part first: preload, contractility, afterload, rate and rhythm, or obstruction, because pressure is cardiac output times resistance. Pulse-pressure variation of 9% says she is not preload-responsive.
- Ephedrine, not phenylephrine, because its indirect beta effect helps the rate; phenylephrine would slow her and raise afterload on a weak ventricle.
- Norepinephrine infusion if it persists: it raises MAP while preserving cardiac output. Still low, I add vasopressin, the drug for ACE-inhibitor vasoplegia.
- Echo if the ECG or end-tidal CO2 suggests failure: a failing left ventricle gets epinephrine or dobutamine, norepinephrine holding perfusion pressure; hypovolemia and obstruction get volume and the specific fix.
Watch for: perfusion, not just the number: lactate, urine output and the ECG.
Breaking down the answer
- Phenylephrine versus ephedrine — phenylephrine is pure alpha-1 and slows the heart by baroreflex, which I want in aortic stenosis, HOCM and tachycardia. Ephedrine shows tachyphylaxis because it depletes norepinephrine stores.
- Norepinephrine as the default infusion — alpha with modest beta-1; first-line in septic shock, and starting it peripherally is preferred to delaying for central access.1
- Vasopressin — V1 vasoconstriction independent of catecholamine receptors, so it works in acidosis and catecholamine-resistant states (sepsis, ACE-inhibitor vasoplegia, post-bypass). It does not raise pulmonary vascular resistance much: useful in right heart failure.
- Epinephrine — beta at low doses, alpha at high; first-line for anaphylaxis and arrest, at the cost of tachycardia, arrhythmia and a beta-2 lactate rise.
- Inodilators — dobutamine and milrinone for low output with adequate pressure; milrinone is a PDE-3 inhibitor that works despite beta-blockade and lowers PVR, but drops SVR and is renally cleared.
- Methylene blue and angiotensin II — rescue for refractory vasoplegia. Methylene blue 1–2 mg/kg blocks nitric oxide–guanylate cyclase; boxed warning for serotonin syndrome with serotonergic drugs and opioids.2 Angiotensin II starts at 20 ng/kg/min, at most 80 in first 3 hours.3
- Stress-dose steroids — hydrocortisone 50 mg every 6 hours once norepinephrine has been at least 0.25 mcg/kg/min for 4 hours in septic shock,1 because relative adrenal insufficiency blunts pressor response.
Follow-up question
The norepinephrine restores her pressure. Just after the surgeon cements the femoral component, her MAP falls to 50 on norepinephrine 0.2 mcg/kg/min, the end-tidal CO2 drops to 20 and rescue TEE shows a dilated, hypokinetic right ventricle and a small, underfilled left ventricle.
What do you do?
Follow-up answer
HeadlineAcute right ventricular failure from cement and marrow embolization; more norepinephrine alone will not fix it. I tell the surgeon and call for help.
100% oxygen. Epinephrine for inotropy, adding milrinone only once the pressure allows; inhaled nitric oxide or epoprostenol to unload the right ventricle; vasopressin to keep the MAP up so the right coronary stays perfused. I correct hypoxia, hypercarbia and acidosis, which all raise PVR, and avoid volume because the right ventricle is already distended. I reassess on TEE; if she does not respond or arrests, I start CPR and discuss mechanical support.
Pitfalls that cost points
- Naming a pressor before naming the cause; knowing when a pressor is the wrong answer is the graded judgment.
- Treating the number without perfusion endpoints: lactate, urine output, mental status, SvO2.
- Dopamine as first choice: about twice the arrhythmias of norepinephrine in septic shock.1
Rapid-fire
Q: Why does phenylephrine cause bradycardia? A: The rise in pressure triggers the baroreceptor reflex, increasing vagal tone.
Q: Why add vasopressin rather than escalate norepinephrine? A: The Surviving Sepsis Campaign suggests adding it over escalating;1 a different receptor spares catecholamine dose and arrhythmias, and it replaces a relative vasopressin deficiency in sepsis.
Q: Why does milrinone work in a beta-blocked patient? A: It raises cAMP by blocking its breakdown, downstream of the beta receptor.
Q: The right ventricle fails after cardiopulmonary bypass; what else do you check? A: Coronary air or a graft problem; if inotropes and pulmonary vasodilators fail, I discuss returning to bypass and mechanical support.
Q: What is your MAP target? A: 65 mmHg in most patients, the septic shock target;1 higher in chronic hypertension, raised intracranial pressure or spinal cord perfusion concerns.
Numbers to know
| Item | Value |
|---|---|
| Phenylephrine | 50–100 mcg bolus; 0.2–1 mcg/kg/min |
| Ephedrine | 5–10 mg bolus |
| Norepinephrine | 0.02–0.3 mcg/kg/min (higher in refractory shock) |
| Vasopressin | Septic shock 0.01–0.07, post-cardiotomy 0.03–0.1 units/min;4 1 unit bolus in the OR |
| Epinephrine | 10–20 mcg bolus; 0.02–0.2 mcg/kg/min |
| Milrinone / dobutamine | 0.25–0.75 / 2.5–10 mcg/kg/min |
| Angiotensin II | Start 20 ng/kg/min; ≤ 80 first 3 h, ≤ 40 maintenance3 |
Links
- Intraoperative hypotension: differential and management, Sepsis and septic shock, Heart failure and reduced ejection fraction, Pulmonary hypertension and right ventricular failure, Cardiopulmonary bypass: conduct and separation
- Atlas: Ventricular function and wall motion
- Surviving Sepsis Campaign international guidelines (2021)
Sources
- 1.Surviving sepsis campaign: international guidelines for management of sepsis and septic shock 2021 · SCCM / ESICM, 2021 · pmc.ncbi.nlm.nih.gov
- 2.PROVAYBLUE (methylene blue) injection prescribing information · FDA / DailyMed · dailymed.nlm.nih.govBoxed warning: serotonin syndrome with serotonergic drugs and opioids; labeled dose 1 mg/kg is for methemoglobinemia.
- 3.GIAPREZA (angiotensin II) injection prescribing information · FDA / DailyMed · dailymed.nlm.nih.gov
- 4.VASOSTRICT (vasopressin) injection prescribing information · FDA / DailyMed · dailymed.nlm.nih.gov
Facts on this page were checked against these sources on Oct 14, 2026. Guidelines change; confirm doses against current institutional protocols.