What is a reasonable baseline blood pressure to use preoperatively in a patient with hypertension?

Reasonable Baseline Blood Pressure for Preoperative Use

When the only available preoperative blood pressure appears high, use <180/110 mmHg as the acceptable threshold to proceed with elective surgery, and consider this elevated reading as the baseline for intraoperative blood pressure management. 1

Primary Approach: The 180/110 mmHg Rule

The Association of Anaesthetists of Great Britain and Ireland and British Hypertension Society provide clear guidance for this exact scenario:

• Patients presenting to preoperative assessment without documented primary care blood pressures should proceed to elective surgery if clinic blood pressures are below 180 mmHg systolic and 110 mmHg diastolic. 1

• This threshold accounts for "white coat hypertension" and the inherently stressful nature of secondary care environments, which typically produce higher readings than primary care settings. 1

• The disparity between primary care thresholds (160/100 mmHg) and secondary care thresholds (180/110 mmHg) exists because blood pressure measurements are more accurate in primary care due to less stressful environments and more practiced technique. 1

Using the Elevated Reading as Your Baseline

For intraoperative management, maintain blood pressure within 20-30% of the preoperative reading you obtained, even if that reading appears elevated. 2, 3

Specific Parameters:

• Keep systolic blood pressure between 70-140% of the baseline value (or within 90-160 mmHg for patients with normal baseline). 4

• Maintain mean arterial pressure (MAP) ≥60-65 mmHg to reduce cardiovascular, cerebrovascular, and renal complications. 4

• Avoid drops >30% below baseline, as this threshold is associated with end-organ injury regardless of the absolute starting value. 4

Critical Pitfalls to Avoid

Do not delay surgery to "optimize" blood pressure below 180/110 mmHg. There is no evidence that perioperative blood pressure reduction affects rates of cardiovascular events beyond what would be expected over months in primary care. 1

Do not ignore the patient's baseline hypertensive state when setting intraoperative targets. Patients with preoperative hypertension have higher thresholds for harm than the standard 90 mmHg cutoff. 4, 5

Do not assume a single elevated reading represents the patient's true baseline. The preoperative reading is often a poor reflection of the patient's normal blood pressure profile due to anxiety and environmental factors. 2, 3

When to Reconsider Surgery

Only defer elective surgery if blood pressure is ≥180/110 mmHg, and in these cases, refer the patient back to primary care for proper diagnosis and management of hypertension. 1

Additional Red Flags:

• Evidence of acute target organ damage (acute coronary syndrome, stroke, acute kidney injury, hypertensive encephalopathy). 1

• Systolic BP ≥180 mmHg or diastolic BP ≥120 mmHg defines hypertensive crisis and warrants evaluation for end-organ damage before proceeding. 6

Practical Algorithm

1. Measure blood pressure properly: Seated patient, supported arm, at least 1 minute rest, take 3 readings 1 minute apart, use the lower of the last two readings. 1

2. If <180/110 mmHg: Proceed with surgery, use this value as baseline for intraoperative management. 1

3. If ≥180/110 mmHg: Refer to primary care for concurrent hypertension assessment, but surgery can still proceed if clinically urgent. 1

4. Intraoperatively: Maintain BP within 20-30% of baseline, avoid MAP <60-65 mmHg, and prevent systolic BP drops >30% from baseline. 4, 2, 3