Anesthesiology APPLIED Exam › Cardiovascular and cardiac anesthesia

Intraoperative hypotension: differential and management

Cardiovascular and cardiac anesthesia·~5 min read· Physician-reviewed✓ Sourced · 3

Stem

A 72-year-old woman, 70 kg, with hypertension treated with losartan, which she took this morning, is having a laparoscopic right hemicolectomy under general anesthesia with sevoflurane. Her baseline pressure is 150/85. Fifteen minutes after insufflation and head-down positioning, the cuff reads 76/40 with a heart rate of 58 in sinus rhythm. She has two peripheral cannulas and no arterial line.

Question

How do you approach her hypotension?

Ideal answer

HeadlineConfirm the number, then treat and think at once: ephedrine now for her slow rate; insufflation and this morning's ARB lead my list.

Confirm: cuff size and position, feel a pulse; with an arterial line I would flush and level the transducer.
Reduce excessive anesthetic depth, ephedrine for the slow rate, restoring perfusion pressure; I ask the surgeon what is happening in the field.
Work the physiology: preload, afterload, contractility, rate and rhythm, which maps onto hypovolemic, distributive, cardiogenic and obstructive shock;¹ for her, a lower insufflation pressure and vasopressin ready.
Look for the time-critical causes: tension pneumothorax, tamponade, embolism and anaphylaxis.
MAP at least 60–65 mmHg,² within 20% of baseline (or systolic at least 90 mmHg), because she is chronically hypertensive; sustained lower values are linked to kidney and myocardial injury.

Watch for: persistence: then an arterial line.

Breaking down the answer

Confirm before treating — a damped line or a cuff on the wrong arm creates hypotension that does not exist; checking takes five seconds. The examiner tests whether I think in a structure or reach for phenylephrine by reflex.
Inside each mechanism — preload: bleeding, venous pooling, caval compression, pneumoperitoneum, positive pressure or auto-PEEP; afterload: anesthetic vasodilation, neuraxial block, anaphylaxis, sepsis; contractility: ischemia, drugs, a failing heart. The surgeon controls the commonest: bleeding, caval retraction, insufflation pressure, vagal traction.
Phenylephrine or ephedrine — phenylephrine 50–100 mcg for vasodilation with a normal or fast rate; ephedrine 5–10 mg adds chronotropy when slow. Persistent need moves me to a norepinephrine infusion, which I run peripherally at low dose.
Fluid only when responsive — a 250–500 mL bolus when pulse-pressure variation exceeds about 13% in a ventilated patient in sinus rhythm, or with clear loss; unguided fluid drowns a failing ventricle and swells the bowel.
ACE inhibitor or ARB vasoplegia — vasopressin 1–2 units IV, because with the renin-angiotensin system blocked catecholamines work poorly; methylene blue 1–2 mg/kg next if refractory. Prevention: hold these drugs 24 hours before surgery with controlled hypertension.²
Epinephrine early for anaphylaxis — hypotension with bronchospasm, rash or a rising peak pressure after an antibiotic or relaxant: epinephrine 10–100 mcg IV boluses escalating, because phenylephrine does not stabilize mast cells.
Echo when the answer is unclear — TEE or transthoracic echo shows in a minute whether the ventricle is empty, failing, compressed or obstructed, rather than escalating blindly. That is the adaptability attribute: the first treatment usually fails in the stem.

Follow-up question

She needs repeated pressor boluses, so a colleague places a right subclavian central line. Ten minutes later the pressure is 60/30 despite phenylephrine, the peak airway pressure has climbed from 22 to 40 cmH2O, and the SpO2 is falling.

What is your diagnosis and management?

Follow-up answer

HeadlineTension pneumothorax: hypotension, rising airway pressure, hypoxemia after a line near the pleura. I call for help and decompress without waiting for a radiograph.³

Positive pressure makes tension more likely, and central line placement is a classic iatrogenic cause.³ Pneumoperitoneum released, 100% oxygen, breath sounds and lung sliding checked if ultrasound is at hand, then a 14- or 16-gauge catheter in the second intercostal space at the midclavicular line, then a chest tube immediately.³ Adult trauma teaching now prefers the fourth or fifth space just anterior to the midaxillary line, where the wall is thinner. I reassess pressure and compliance. High pressure with equal breath sounds suggests bronchospasm or anaphylaxis; I check the tube, then epinephrine.

Pitfalls that cost points

Repeating phenylephrine five times without changing strategy.
Missing the patterns that cannot wait: tension pneumothorax, tamponade, anaphylaxis, embolism and local anesthetic toxicity; the first two are obstructive shock that no vasopressor fixes.¹

Rapid-fire

Q: Why is phenylephrine a poor choice in severe aortic stenosis with bradycardia? A: The reflex slowing lowers cardiac output in a fixed-output lesion; I want norepinephrine, which supports pressure with less reflex bradycardia.

Q: Why does pulse-pressure variation fail in a laparoscopy? A: High abdominal pressure, low tidal volumes, arrhythmias or an open chest change the heart-lung interaction, so the threshold no longer predicts fluid response.

Q: Why does hypotension follow intubation? A: Induction agents remove sympathetic tone and positive pressure lowers venous return, worst in a patient who is volume depleted or chronically on renin-angiotensin blockade.

Q: Why is a MAP of 65 a target? A: Large cohort data link time below about 65 mmHg with acute kidney injury and myocardial injury; it is an association, so I individualize to baseline.

Numbers to know

Item	Value
MAP floor	≥60–65 mmHg (SBP ≥90),² or within 20% of baseline
Phenylephrine bolus	50–100 mcg IV
Ephedrine bolus	5–10 mg IV
Norepinephrine infusion	0.02–0.2 mcg/kg/min
Vasopressin bolus	1–2 units IV
Pulse-pressure variation	>13% predicts fluid response

Sources

1.Shock · Merck Manual Professional Edition · merckmanuals.com
2.2024 ACC/AHA guideline on perioperative cardiovascular management before noncardiac surgery: What's new? · Cleveland Clinic Journal of Medicine, 2025 · ccjm.orgCohn SL, CCJM 92(4), April 2025. Reports the 2024 AHA/ACC intraoperative target of MAP at least 60-65 mmHg or SBP at least 90 mmHg.
3.Pneumothorax · Merck Manual Professional Edition · merckmanuals.com

Facts on this page were checked against these sources on Oct 14, 2026. Guidelines change; confirm doses against current institutional protocols.