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Intraoperative hypotension: differential, management, and MAP targets

A hemodynamics page — what mean arterial pressure to defend and why, the causes phase by phase, the first- and second-line drugs, and the point at which a routine pressor becomes a rescue problem.

Reviewed and updated September 2026 · Written by Anastasia Jackson, DNAP, CRNA

Every clinical claim on this page is cited to its source below. How we source clinical content.

The short answer

Defend a MAP of at least 60–65 mmHg for most adults; below that, the risk of acute kidney injury, myocardial injury, and death rises with both the depth and the duration of the dip.1,2 Randomized trials of higher or individualized targets have not improved outcomes, so 65 mmHg remains the working floor.1,3 Treat by mechanism, not reflex: fix the cause (depth, hypovolemia, positioning, bleeding), give a bolus vasopressor while you do, and escalate to an infusion — then to a second agent — when boluses are needed repeatedly.

Intraoperative hypotension is one of the few perioperative harms that is both common and modifiable. It affects roughly 30–80% of surgical patients depending on definition,4 and about one-third of it is produced by the anesthetic itself, between induction and incision.2,5 The evidence for a harm threshold is observational but remarkably consistent, and it converges on a MAP of about 65 mmHg.

Key takeaways

  • Defend MAP ≥ 60–65 mmHg. A systematic review of 42 studies found that MAP < 65 mmHg sustained ≥ 10 minutes raised the relative risk of AKI by ~60%, of myocardial injury by ~30%, and of death by ~4%.3
  • Depth and duration both matter. Once MAP falls to ~55 mmHg, only a few minutes are associated with increased mortality.2
  • Higher and individualized targets have not helped. IMPROVE-multi and POISE-3 (> 8,600 patients combined) showed no benefit from targeting MAP above a conventional 60–65 mmHg floor.3,4
  • Treat the endotype. Hypotension is vasodilation, hypovolemia, myocardial depression, or bradycardia — often in combination. A uniform pressure number does not tell you which.6,7
  • Baseline risk outweighs the intraoperative dip. Myocardial injury is largely restricted to patients with pre-existing cardiovascular risk, but unlike their comorbidities, blood pressure is controllable.2
  • High pressures carry risk too. In noncardiac surgery, intraoperative arterial pressures above ~160 mmHg are associated with myocardial injury and infarction, and during cardiac surgery systolic pressure > 140 mmHg is associated with increased 30-day mortality; POQI found insufficient evidence to recommend a general upper limit.8

What MAP to defend, and why

There is no single trial-proven target, but the observational signal is coherent. The 2019 Perioperative Quality Initiative (POQI) consensus concluded that MAP below 60–70 mmHg is associated with myocardial injury, acute kidney injury, and death, as a function of severity and duration, and that there is increasing evidence that even brief exposure to systolic pressure < 100 mmHg is harmful during noncardiac surgery.8 The American Heart Association's scientific statement on myocardial injury after noncardiac surgery reached the same conclusion, adding that an absolute MAP ≤ 65 mmHg and a relative fall of ~30% from baseline were each associated with myocardial injury.2

Severity and duration both determine the risk. A systematic review of 42 studies graded the reported risk of organ injury as moderate (odds, risk, or hazard ratios of 1.4–2.0) with MAP < 65–60 mmHg for ≥ 5 minutes or any exposure below 55–50 mmHg, and as high (ratios > 2.0) with MAP < 65 mmHg for ≥ 20 minutes, < 50 mmHg for ≥ 5 minutes, or any exposure below 40 mmHg.9 Once MAP falls to 55 mmHg, a duration of just a few minutes is associated with increased mortality.2

Why not just aim higher? Because the trials say it does not help. In IMPROVE-multi (2025), targeting each patient's preoperative mean nighttime MAP — a target that was ≥ 80 mmHg in two-thirds of patients — did not reduce a composite of AKI, myocardial injury, cardiac arrest, or death versus a routine target of ≥ 65 mmHg.3 POISE-3 (7,490 patients) found no benefit from a hypotension-avoidance strategy targeting MAP ≥ 80 mmHg over one targeting ≥ 60 mmHg, and a 458-patient trial found no benefit of a ≥ 75 mmHg target over ≥ 60 mmHg.1,3,4 A meta-analysis of higher-MAP versus normotension targets found no reduction in AKI in surgical patients; a lower risk of renal replacement therapy was seen only in shock patients with premorbid hypertension.10 Higher targets have not been shown superior; guidelines recommend defending MAP ≥ 60–65 mmHg for most noncardiac surgical patients.1,4

When to individualize upward anyway

The negative individualized-target trials do not abolish clinical judgment. Baseline blood pressure varies widely, and about half of patients presenting for major noncardiac surgery have chronic hypertension;3 in a meta-analysis of 30 observational studies, a preoperative diagnosis of hypertension was associated with a 35% increase in cardiovascular complications.1 The often-quoted autoregulatory range — constant cerebral blood flow between a MAP of 60 and 150 mmHg — applies to healthy normotensive patients without cerebrovascular disease.7 The same AHA/ASA statement suggests considering a MAP above 70 mmHg, especially in patients at moderate or high risk for perioperative stroke, while noting that the evidence linking intraoperative hypotension to stroke is not very strong and that a systematic review did not identify significant associations between MAP thresholds and stroke.7 This is a suggestion for that group, not a universal target; the MAP ≥ 60–65 mmHg floor remains the default.1 Defending a higher MAP for chronic hypertension, known renal artery or carotid stenosis, elevated baseline pressures, or cerebral and spinal cord procedures where perfusion pressure is the operative concern is expert judgment rather than a guideline recommendation, and the outcome evidence is indirect.

Causes by phase of the case

The differential shifts as the case progresses. Naming the phase narrows the cause, and the cause determines the drug.

PhaseDominant mechanismTypical culprits
Induction / pre-incisionVasodilation + myocardial depression + loss of sympathetic tonePropofol (↓SVR and ↓contractility), opioids such as remifentanil/sufentanil (↓SVR, ↓HR), volatile agents (↓SVR). Roughly one-third of all intraoperative hypotension occurs here, before surgery begins.2,5
Neuraxial onsetSympathectomy → ↓SVR ± ↓venous returnSpinal/epidural blockade. After spinal anesthesia for cesarean delivery, the incidence is up to ~74%.11
Positioning↓Venous returnPositioning changes (reverse Trendelenburg, beach chair, prone caval compression) reduce venous return.
Pneumoperitoneum / insufflation↑Intra-abdominal pressure → IVC compression; vagal surgeRapid peritoneal stretch increases vagal tone (hypotension + bradycardia, occasionally asystole); CO can fall ~28% at pressures > 15 mmHg.12
Maintenance / surgicalHypovolemia, hemorrhage, deep anesthesiaOngoing blood/fluid loss,12,13 third-spacing, excessive anesthetic depth, caval/cardiac compression by surgeon, gas embolism.12
Any phase — do not missDistributive / obstructive / anaphylacticAnaphylaxis (NMBAs, antibiotics, latex, chlorhexidine), pulmonary or amniotic fluid embolism,13 gas embolism,12 tension pneumothorax, tamponade,14 anaphylactic transfusion reaction, neuraxial-induced vasodilation,13 adrenal insufficiency.15

Sudden, refractory hypotension is anaphylaxis until proven otherwise. Perioperative anaphylaxis frequently presents as isolated cardiovascular collapse without a rash, because the patient is draped and unconscious. Profound capillary leak and relative hypovolemia leave these patients severely volume-depleted.16 Epinephrine is the treatment — titrated IV boluses (in the Australian and New Zealand perioperative guideline, 20 mcg for moderate reactions, 100–200 mcg every 1–2 minutes for life-threatening reactions with the dose increased if unresponsive, and 1 mg at grade 4), an infusion when repeated boluses are needed,16 aggressive crystalloid, and removal of the likely trigger.13,17 Antihistamines and steroids are adjuncts, not first-line.17

Patient factors that prime the pump

Independent predictors of intraoperative hypotension include ASA III–IV status (OR 1.71), lower baseline MAP (OR 1.19 per 10-mmHg decrease), high- and intermediate-risk surgery, emergency surgery (OR 1.65), longer duration, and — importantly and modifiably — continuation of ACE inhibitors or ARBs on the day of surgery (OR 1.33).6 Older age is associated with larger blood-pressure swings after propofol induction (a MAP fall or rise of 30% or more).18

First- and second-line drugs

Every hypotensive episode gets the same opening move: lighten the anesthetic if depth allows, confirm the rhythm and rate, give volume if the tank is empty, and buy time with a bolus vasopressor while the cause is identified. The agent then follows the mechanism.

1Bolus agents (the reflex reach)

In a head-to-head trial for transient intraoperative hypotension, both restored MAP comparably. Both also raised cerebral blood-flow velocity, more so after ephedrine in the between-group comparison of changes (5.3 vs 3.4 cm/s, p = 0.016), though not in the mixed-model time-by-group analysis (p = 0.173). Ephedrine raised cardiac output while phenylephrine lowered it; ephedrine produced a small (~1 percentage point) rise in cerebral oxygen saturation that was not significant after mixed-model adjustment, and phenylephrine left it unchanged — a mechanistic reason to match the agent to the heart rate.19

2Infusions (when boluses repeat)

3Inotropes (the low-output endotype)

When hypotension is driven by pump failure rather than vasodilation — a dilated, poorly contracting ventricle on TEE, a low cardiac index — a pressor alone will raise afterload against a failing heart. This is the niche for dobutamine and milrinone, detailed in the drug entries below.23,24,25

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When to escalate

Escalation is a response to a pattern, not a single reading. Move up a step when any of the following is true:

The ACE-inhibitor / ARB scenario. Continuation of an ACE inhibitor or ARB on the day of surgery is an independent predictor of intraoperative hypotension,6 and the hypotension can resist catecholamines because the compensatory angiotensin axis is blocked. Vasopressin is the rational rescue, exploiting a pathway the drug does not touch.22 Omitting the renin-angiotensin blocker 24 hours before elevated-risk surgery reduces intraoperative hypotension and may be beneficial in select patients with controlled hypertension (Class 2b); this has not translated into improved clinical outcomes (no reduction in MINS or major adverse cardiovascular events) in randomized trials, so it remains an individualized decision.1

Cardiovascular drug entries

Two of these agents (dobutamine, milrinone) treat the low-output form of hypotension. The remaining four (diltiazem, clevidipine, nitroprusside, amlodipine) lower blood pressure — they belong on this page as the flip side of the hemodynamic ledger: agents whose overshoot, or whose presence as a home or infused medication, produces the hypotension you are managing.

Dobutamine — β1 inotrope for depressed contractility

Mechanism: a direct-acting inotrope acting mainly on cardiac β-receptors, increasing contractility and stroke volume with comparatively mild chronotropic, arrhythmogenic and vasodilatory effect; it generally lowers systemic vascular resistance.23 Onset 1–2 minutes, plasma half-life ~2 minutes.23

Dose: start 0.5–1 mcg/kg/min, titrate; usual effective range 2–20 mcg/kg/min, occasionally up to 40 mcg/kg/min.23

Correct hypovolemia before starting dobutamine. Most patients show a 10–20 mmHg rise in systolic pressure, but blood pressure can fall, occasionally precipitously. Continuous ECG and blood-pressure monitoring are required; watch for tachyarrhythmia. No improvement may be observed in the presence of a fixed obstruction such as severe aortic stenosis.23

Milrinone — inodilator (PDE-3 inhibitor)

Mechanism: a selective phosphodiesterase-3 inhibitor that raises cardiac cAMP, producing both positive inotropy and arterial + venous vasodilation, with improved diastolic relaxation and little chronotropy.25,29 Because it bypasses the β-receptor, it retains efficacy during β-blockade.25,30

Dose: the label directs a 50 mcg/kg loading dose over 10 minutes, then 0.375–0.75 mcg/kg/min; terminal half-life ~2.3 hours, prolonged in renal impairment.25 Many clinicians omit or slow the bolus in the OR.

Milrinone lowers blood pressure. In heart-failure studies, the highest loading-plus-infusion regimen (75 mcg/kg + 0.75 mcg/kg/min) lowered MAP by ~17%, versus up to ~5% at the lower regimens; the label does not single out the loading dose.25 Milrinone is more likely than dobutamine to provoke hypotension, particularly during bolus administration, and — because of its long half-life — the resulting hypotension is not readily reversed by stopping the drug; vasopressor support may be required.24,30 Its long half-life and renal clearance mean effects (and hypotension) persist and accumulate in renal impairment, requiring dose reduction.24,25 It may be the preferred inotrope when β-blockade or markedly elevated pulmonary artery pressure complicates a low-output state.14,24,30

Diltiazem — non-dihydropyridine calcium-channel blocker (IV)

Mechanism / use: slows AV-nodal conduction (prolonging AH conduction and nodal refractoriness) for rate control of atrial fibrillation/flutter and conversion of PSVT, while lowering SVR and blood pressure through vascular smooth-muscle relaxation. Maximal hemodynamic effect within 2–5 minutes.31

Dose: 0.25 mg/kg (~20 mg) IV over 2 min; if needed, 0.35 mg/kg (~25 mg) after 15 min; infusion 5–15 mg/h, with continuous ECG and frequent blood-pressure monitoring.31

Diltiazem is both negatively chronotropic and a vasodilator, so it can cause or deepen intraoperative hypotension, especially when stacked with volatile agents or β-blockers. Do not initiate in acute decompensated heart failure or cardiogenic shock; rare worsening of heart failure has been reported with impaired ventricular function.31

Clevidipine — ultra-short-acting dihydropyridine (IV)

Mechanism / use: an L-type calcium-channel blocker that lowers MAP purely by reducing arterial SVR, without affecting cardiac filling pressures; indicated for reducing blood pressure when oral therapy is not feasible or not desirable. Onset 2–4 minutes; offset (full BP recovery) 5–15 minutes after stopping.32

Dose: start 1–2 mg/h, double every ~90 s toward target, then increase by less than doubling every 5–10 min; usual 4–6 mg/h, up to 21 mg/h averaged per 24 h (lipid-load limit).32

Contraindicated in soy/egg allergy and in defective lipid metabolism (e.g., pathologic hyperlipidemia, acute pancreatitis), as it is a lipid emulsion, and in severe aortic stenosis.32 Dihydropyridine calcium-channel blockers can produce negative inotropic effects and exacerbate heart failure, and clevidipine may produce systemic hypotension and reflex tachycardia; rebound hypertension can follow discontinuation of a prolonged infusion without transition to another agent.32

Sodium nitroprusside — arterial + venous nitrovasodilator (IV)

Mechanism / use: a nitric-oxide donor that rapidly lowers blood pressure by relaxing arterial and venous smooth muscle; used for hypertensive crises and deliberate controlled hypotension. Effect resolves within 1–10 minutes of stopping.33

Dose: start 0.3 mcg/kg/min, titrate to a maximum of 10 mcg/kg/min; in eGFR < 30 mL/min/1.73 m², cap the mean rate at < 3 mcg/kg/min, and in anuric patients at 1 mcg/kg/min.33

Boxed warning — excessive hypotension and cyanide toxicity. Use only with continuous blood-pressure monitoring. Rates > 2 mcg/kg/min generate cyanide faster than the body can clear it, and the buffering capacity is exhausted in under an hour at the maximum rate; keep maximal-rate infusions as brief as possible. An early sign of cyanide toxicity is a rising dose requirement; look for venous hyperoxemia, metabolic (lactic) acidosis, and altered mental status. Treat by stopping the infusion and giving the labeled antidote — sodium nitrite followed by sodium thiosulfate. Thiocyanate accumulates in renal impairment; methemoglobinemia and raised intracranial pressure are additional cautions.33 Current AHA poisoning guidelines instead favor hydroxocobalamin as first-line for cyanide toxicity because it does not cause hypotension, with sodium nitrite plus sodium thiosulfate as the alternative when hydroxocobalamin is unavailable.34,35 Hydroxocobalamin (Cyanokit), also labeled for known or suspected cyanide poisoning, is chemically incompatible with sodium nitrite and sodium thiosulfate and must not share an IV line with them.36

Amlodipine — long-acting oral dihydropyridine

Mechanism / use: a peripheral arterial vasodilator that lowers SVR and blood pressure with essentially no reflex tachycardia or catecholamine change at chronic oral doses; used for hypertension and angina, not for acute intraoperative titration.37

Perioperative relevance: amlodipine has a terminal elimination half-life of about 30–50 hours, and because of the gradual onset of action, acute hypotension is unlikely. It is dosed 5 mg once daily (max 10 mg; 2.5 mg in small or elderly patients).37

Frequently asked questions

What MAP should be maintained during surgery?

At least 60–65 mmHg for most adults. A 42-study systematic review found that MAP < 65 mmHg for ≥ 10 minutes increased the relative risk of acute kidney injury by ~60%, myocardial injury by ~30%, and death by ~4%, and the POQI consensus and AHA statements identify MAP < 60–70 mmHg as harmful in proportion to depth and duration.2,3,8

Does targeting a higher MAP improve outcomes?

No, not in randomized trials. IMPROVE-multi (individualized targets, often ≥ 80 mmHg), POISE-3 (≥ 80 vs ≥ 60 mmHg), and a 458-patient trial (≥ 75 vs ≥ 60 mmHg) all failed to show benefit over a conventional floor, and a meta-analysis found no reduction in AKI in surgical patients, with a lower risk of renal replacement therapy only in shock patients with premorbid hypertension.1,3,4,10 Higher targets have not been shown superior; guidelines recommend defending MAP ≥ 60–65 mmHg for most noncardiac surgical patients,1,4 with upward individualization for specific grounds such as chronic hypertension or a perfusion-dependent procedure left to clinical judgment.

How long does hypotension have to last to cause harm?

Not long. A systematic review of 42 studies found moderately raised risks of organ injury (odds, risk, or hazard ratios of 1.4–2.0) with MAP < 65–60 mmHg for ≥ 5 minutes or any exposure below 55–50 mmHg,9 and once MAP falls to roughly 55 mmHg, a duration of just a few minutes is associated with increased mortality.2 Both the depth of the dip and its duration count, which is why continuous blood-pressure monitoring — an arterial line in higher-risk cases — is worthwhile: it shortens the time the pressure spends below target.2,27

Should phenylephrine or ephedrine be used first for intraoperative hypotension?

Match the agent to the heart rate. Phenylephrine, a pure α-agonist, is the default for vasodilation with a normal or high heart rate; it raises systemic vascular resistance but causes a reflex fall in heart rate and modestly lowers cardiac output.19 Ephedrine, with mixed α/β activity, is preferred when hypotension is accompanied by relative bradycardia, because it raises heart rate and cardiac output. In a head-to-head trial both restored MAP comparably, but ephedrine raised cardiac output while phenylephrine lowered it; ephedrine produced a small (~1 percentage point) rise in cerebral oxygen saturation that was not significant after mixed-model adjustment, and phenylephrine left it unchanged.19

What should be done when hypotension does not respond to a vasopressor?

Stop titrating and reconsider the cause. Catecholamine-refractory hypotension should prompt a search for an obstructive or anaphylactic process (tension pneumothorax, tamponade, embolism, anaphylaxis) and for unaddressed bleeding or excessive anesthetic depth.13,17 When true vasoplegia persists despite catecholamines, add vasopressin (labeled starting dose 0.03 U/min in post-cardiotomy shock), then consider methylene blue, and — with escalating catecholamine requirement — angiotensin II or hydroxocobalamin.22,28

Why do patients on ACE inhibitors or ARBs become so hypotensive under anesthesia?

Because the renin-angiotensin axis that normally compensates for anesthetic-induced vasodilation is blocked, leaving the response heavily dependent on the sympathetic and vasopressin systems. Continuing an ACE inhibitor or ARB on the day of surgery is an independent predictor of intraoperative hypotension,6 and the resulting hypotension can resist catecholamines. Vasopressin is the rational rescue because it acts through a pathway the drug does not touch.22 Omitting the agent 24 hours before elevated-risk surgery reduces intraoperative hypotension and may be beneficial in select patients with controlled hypertension, but it has not improved clinical outcomes in randomized trials, so the decision is individualized.1

When is an inotrope, rather than a vasopressor, the right choice?

When the problem is the pump, not the pipes. A dilated, poorly contracting ventricle on transesophageal echocardiography or a documented low cardiac index calls for dobutamine or milrinone, because a pure vasoconstrictor raises afterload against a failing heart.23,24,25 Milrinone, which bypasses the β-receptor, may be preferred when the low-output state is complicated by β-blockade or markedly elevated pulmonary artery pressure,14,24,30 but it lowers blood pressure — by ~17% at the highest loading-plus-infusion regimen in the label's heart-failure studies — and its effects persist in renal impairment.25

References

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Disclaimer. Reference information for licensed clinicians and students. Not a medical device, and not a substitute for clinical judgment. MAP targets are derived largely from observational data and negative randomized trials of higher targets; individual targets, drug selection and dosing must be tailored to the specific patient, procedure and institutional resources, and verified against current package inserts.

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