Is it reasonable to determine pre-surgery baseline blood pressures using post-surgical blood pressures?

Using Post-Surgical Blood Pressures to Determine Pre-Surgery Baseline Blood Pressures

It is not reasonable to use post-surgical blood pressures to determine pre-surgery baseline blood pressures, as this approach contradicts evidence-based guidelines and may lead to inappropriate blood pressure management. 1

Why Post-Surgical Blood Pressures Are Not Reliable Baseline Indicators

Physiological Factors Affecting Post-Surgical Blood Pressure

• Pain and sympathetic stimulation
• Hypothermia
• Hypoxia
• Fluid shifts and volume status changes
• Medication effects (anesthetics, analgesics)
• Anxiety and stress response

Evidence Against Using Post-Surgical Values

The Perioperative Quality Initiative consensus statement explicitly recommends that "patient-specific postoperative blood pressure target ranges should be created based on baseline preoperative blood pressure measurements and clinical context" 1. This indicates that preoperative values should guide postoperative targets, not the reverse.

Proper Determination of Baseline Blood Pressure

Optimal Timing for Baseline Measurement

Research shows that blood pressures taken in the operating room are statistically significantly higher than those taken in pre-surgical testing or holding areas (p<0.001) 2. The study concluded that "blood pressure measurements taken prior to entrance in the operating room can be used to determine baseline blood pressure."

Recommended Approach to Establish Baseline

1. Use pre-surgical clinic measurements: Blood pressures taken during pre-surgical evaluation are highly predictive of home blood pressure values 3
2. Consider multiple measurements: The British Hypertension Society recommends using multiple readings to establish baseline 1
3. Avoid operating room measurements: First BP readings in the OR are consistently elevated and should not be used to determine baseline 2

Clinical Implications

Impact on Perioperative Management

Using post-surgical blood pressures as baseline could lead to:

• Setting inappropriately high target ranges
• Failure to detect significant hypotension (if post-surgical values are lower)
• Increased risk of end-organ injury

Risk Management

The Perioperative Quality Initiative recommends maintaining systolic pressure >90 mmHg and <160 mmHg for patients with normal baseline blood pressure, with adjustments for those with abnormal baseline values 1. Using incorrect baseline values derived from post-surgical measurements could lead to inappropriate management targets.

Best Practice Recommendations

1. Establish baseline before surgery: Obtain blood pressure measurements during pre-surgical evaluation or in the holding area before entering the OR 1, 2

2. Document baseline clearly: Ensure baseline values are clearly documented and communicated to all team members

3. Set appropriate targets: Create patient-specific postoperative target ranges based on documented preoperative baseline values 1

4. Monitor for deviations: Use baseline to identify significant deviations requiring intervention (typically <75% or >140% of baseline) 1

Common Pitfalls to Avoid

• Relying on a single blood pressure measurement in any setting
• Using operating room measurements as baseline
• Failing to consider blood pressure variability, which independently correlates with outcomes 4
• Assuming post-surgical values represent the patient's true baseline

Using post-surgical blood pressures to determine pre-surgical baseline is fundamentally flawed and contradicts established guidelines. Proper perioperative blood pressure management requires accurate baseline determination before surgery to optimize patient outcomes.