What does a pre‑operative blood pressure assessment and management protocol entail for patients scheduled for surgery?

Pre-operative Blood Pressure Assessment for Surgery

Blood pressure less than 180/110 mmHg should not delay elective surgery, but proper measurement technique and documentation are essential to guide perioperative management. 1

Measurement Technique and Environment

The blood pressure must be measured in a standardized, relaxed environment using properly calibrated equipment. 1, 2

• The patient should be seated with their supported arm outstretched for at least one minute before the initial reading 1, 2
• The setting should be temperate and quiet, avoiding patient conversation during measurement 2
• Patients should avoid caffeine, exercise, and smoking for at least 30 minutes before measurement 2
• The middle of the cuff should be positioned at the level of the right atrium, with the bladder encircling 80% of the arm 2

Pulse rate and rhythm must be recorded before measuring blood pressure. 1, 2

• If the pulse is irregular, use manual auscultation over the brachial artery during cuff deflation rather than automated devices, as automated sphygmomanometers are inaccurate with irregular rhythms 1, 2

Multiple Reading Protocol

If the first measurement is ≥140/90 mmHg, take two additional readings at least one minute apart. 1, 2

• Record the lower of the last two readings as the blood pressure 1
• If the reading is <140/90 mmHg, the patient is normotensive and surgery can proceed 1

For patients scheduled for vascular or renal surgery, measure blood pressure in both arms. 1, 2

• If the systolic difference between arms exceeds 20 mmHg, repeat the measurements 1
• Subsequently use the arm with the higher blood pressure for all measurements 1

Documentation Requirements

Blood pressure readings from the past 12 months should be obtained from primary care before surgical referral. 1

• If no documented readings exist from the past 12 months, the pre-operative assessment clinic must measure blood pressure 1
• Document both systolic and diastolic readings verbally and in writing 2
• Record the time of the most recent antihypertensive medication taken before measurements 2

Surgical Decision Thresholds

Blood pressures <180 mmHg systolic AND <110 mmHg diastolic should not preclude elective surgery. 1, 3

This threshold is based on the lack of evidence that acute pre-operative blood pressure reduction improves outcomes, and the recognition that isolated pre-operative measurements may reflect anxiety rather than true hypertension. 4, 5

For readings between 140/90 mmHg and 179/109 mmHg (Stage 1-2 hypertension):

• Surgery can proceed without delay 1, 3
• The patient should be referred to their general practice for concurrent determination of whether primary care hypertension is present and requires long-term management 1
• Consider ambulatory or home blood pressure monitoring to establish true blood pressure status 1, 2

For readings ≥180/110 mmHg (Stage 3-4 hypertension):

• Elective surgery should be postponed 1, 3
• The patient must return to primary care for immediate assessment and blood pressure optimization before proceeding with non-urgent surgery 1, 3

Antihypertensive Medication Management

Regular antihypertensive medications should be continued preoperatively, as sudden withdrawal can cause adverse events. 1, 3

• Beta-blockers must never be abruptly discontinued, as withdrawal may cause silent myocardial ischemia that requires continuous ECG monitoring and serial troponin measurements to detect 1, 3
• ACE inhibitors and angiotensin receptor blockers may be omitted on the day of surgery, as their continuation is associated with greater perioperative hemodynamic fluctuations 1, 3
• Do not initiate new beta-blocker therapy perioperatively in patients not already taking them, as this increases postoperative mortality from hypotension and stroke 1, 3

Common Pitfalls to Avoid

Do not rely on a single elevated blood pressure reading, as measurements in surgical settings are often elevated due to anxiety ("white coat hypertension"). 2, 3

Do not use an inappropriately sized cuff, as this leads to inaccurate readings. 2

Do not measure blood pressure while the patient is sitting on an examination table without proper back support and feet placement. 2

Do not attempt acute blood pressure reduction immediately before surgery in patients with readings <180/110 mmHg, as there is no evidence this improves perioperative outcomes. 3, 4

Special Considerations

For emergency or urgent surgery, these protocols may not apply, and surgery must proceed with awareness of increased risk. 1

The evidence shows that pre-operative hypertension is associated with intra-operative hemodynamic fluctuations (hypotension, hypertension, arrhythmias), but studies have not conclusively demonstrated that these fluctuations cause clinically significant harm or increased rates of peri-operative cardiovascular events. 1, 5