The Takeaway

There were no significant differences in postoperative complications between moderate and high mean arterial pressure management. To reduce cardiac, renal, and neurological complications, targeting MAP >65 mmHg is a reasonable threshold for most patients. However, individualized BP management is crucial, especially for high-risk patients. The risk for complications increases with both severity (SBP <90 mmHg and MAP <65 mmHg) and duration of hypotension.

Study Design

• Searched PubMed, the Cochrane Database, and Embase from August 2014 to August 2024
• Studies evaluated low treatment threshold of hypotension (< 60 mmHg; N = 101; 2 studies), moderate treatment threshold of hypotension (60–75 mmHg; N = 4547; 8 studies), and high treatment threshold of hypotension (> 75 mmHg; N = 4460; 7 studies)
• All studies included in the analysis were designed as randomized, controlled, or double-blind trials.
• Characteristics included: randomized controlled study; involved non-cardiac, non-obstetric surgery; included different blood pressure management strategies; evaluated major postoperative complications; and included acute kidney injury, myocardial injury, altered consciousness, or infection.

Physiology Refresh

Why Does Hypotension Matter?

Blood pressure is critical for organ perfusion. When MAP drops below the autoregulatory threshold, organs receive less oxygen and nutrients, leading to ischemia and dysfunction. Different organs have different perfusion thresholds:

Heart: Coronary Perfusion & Myocardial Injury

• The heart is perfused during diastole, meaning diastolic blood pressure (DBP) is crucial for myocardial oxygen delivery.
• Coronary autoregulation functions within a MAP range of 60–140 mmHg.
• Below this range, coronary blood flow becomes pressure-dependent, increasing the risk of myocardial ischemia, infarction, and arrhythmias.
• IOH is particularly dangerous in patients with coronary artery disease, where perfusion is already compromised due to plaque buildup.

Kidneys: Renal Perfusion & Acute Kidney Injury (AKI)

• The kidneys autoregulate blood flow through afferent arteriole constriction and dilation to maintain glomerular filtration.
• Renal autoregulation typically occurs within a MAP range of 80–180 mmHg.
• When MAP drops below 80 mmHg, glomerular filtration rate (GFR) decreases, leading to AKI, electrolyte imbalances, and fluid retention.
• Patients with chronic hypertension have a rightward shift in this autoregulatory curve, making them more susceptible to AKI at even higher MAPs.

Brain: Cerebral Perfusion & Stroke Risk

• The brain maintains constant perfusion through cerebral autoregulation, which operates within a MAP range of 50–150 mmHg in healthy individuals.
• Below 50 mmHg, cerebral blood flow becomes pressure-dependent, increasing the risk of ischemia, confusion, and stroke.
• In patients with chronic hypertension, autoregulation shifts to higher pressures, meaning they may experience cerebral hypoperfusion at MAPs <70–80 mmHg.
• Severe IOH can also contribute to postoperative delirium and cognitive dysfunction, particularly in elderly patients.

How Much Hypotension is Too Much?

• MAP <65 mmHg for even short periods increases postoperative complications.
• MAP <55 mmHg is strongly linked to myocardial injury and AKI, even if transient.
• Longer durations of IOH (>10-20 min) lead to higher risks, with MAP <60 mmHg for >30 min being particularly dangerous.

Excerpts

A systematic review and meta-analysis reported that 10 min of MAP < 80 mmHg, shorter durations of MAP < 70 mmHg, and any exposure to MAP < 55 mmHg are associated with end-organ injury in non-cardiac surgery.

absence of a significant difference in postoperative complications between moderate and high treatment thresholds of hypotension.

In the study conducted by Lamontagne et al., the risk of cardiac arrhythmias in lower and higher MAP arms was 20% and 36%, respectively

recent meta-analysis reported that a lower treatment threshold of hypotension is associated with a reduction in hospital stay compared with a higher treatment threshold

A higher treatment threshold during non-cardiac surgery does not significantly improve short-term prognosis compared with a moderate threshold.

A moderate treatment threshold of hypotension appeared to reduce the length of hospital stay. However, the low treatment threshold of hypotension cannot be adequately explained by the available data and may pose potential risks.

Citation

Qin G, Du MC, Yi KX, Gong Y. Intraoperative hypotension and postoperative risks in non-cardiac surgery: a meta-analysis. BMC Anesthesiol. 2025 Feb 26;25(1):103. doi: 10.1186/s12871-025-02976-5. PMID: 40011811; PMCID: PMC11863555.

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