What does Miller's Anesthesia textbook 9th edition recommend for determining baseline blood pressure in patients undergoing spine surgery?

Determining Baseline Blood Pressure for Spine Surgery According to Miller's Anesthesia 9th Edition

Baseline blood pressure for patients undergoing spine surgery should be assessed on a case-by-case basis using measurements taken prior to entering the operating room, as operating room measurements are typically elevated and do not reflect true baseline values. 1, 2, 3

Proper Method for Determining Baseline Blood Pressure

Pre-operative Assessment

• Use multiple blood pressure readings taken during pre-surgical evaluation or in the holding area before entering the operating room 2
• Do NOT use the first operating room blood pressure measurement as baseline, as these are statistically significantly higher than measurements taken in pre-surgical testing or holding areas 3
• Blood pressure measurements taken prior to arrival in the operating room correlate better with the patient's true baseline and home blood pressure values 3

Specific Considerations for Spine Surgery

• For patients undergoing spine surgery, accurate baseline determination is particularly important due to:
  • Risk of perioperative visual loss associated with blood pressure fluctuations 1
  • Hemodynamic changes that occur when patients are positioned prone 4
  • Potential need for deliberate hypotension during certain spine procedures 1

Blood Pressure Management During Spine Surgery

Target Ranges

• Maintain systolic pressure >90 mmHg and <160 mmHg for patients with normal baseline blood pressure 1
• For patients with abnormal baseline values:
  • Adjust targets based on preoperative measurements
  • Intraoperative systolic pressures should be maintained at >70% of preoperative baseline 1
  • For spine surgery specifically, a MAP range of 70-94 mmHg has been associated with better motor recovery in patients with traumatic spinal cord injury 5

Special Considerations for Hypertensive Patients

• Check for:
  • Presence of pre-operative hypertension
  • Degree of blood pressure control
  • Pre-operative use of anti-hypertensive drugs
  • Patient's risk of end-organ damage 1
• Maintain arterial pressure at higher levels in hypertensive patients to prevent risks to end organs 1

Monitoring Recommendations

During Surgery

• Continually monitor systemic blood pressure in high-risk patients 1
• High-risk patients include those undergoing prolonged procedures (>4 hours) or with substantial blood loss (>800 mL) 1
• Consider more frequent monitoring for patients with decreasing or increasing blood pressure trends 1

Intervention Triggers

• Assess when systolic pressure falls below 100 mmHg (or <75% of baseline, whichever is higher) 1
• Assess when systolic pressure rises above 160 mmHg (or >140% of baseline, whichever is lower) 1
• Treat prolonged significant decreases in blood pressure promptly 1

Common Pitfalls to Avoid

• Using operating room measurements as baseline: First BP measurements in the OR are significantly higher than pre-surgical or holding area measurements 3
• Relying on a single measurement: Multiple readings provide more accurate baseline determination 2
• Using deliberate hypotension without proper assessment: Only use deliberate hypotension when the anesthesiologist and surgeon agree it's essential 1
• Ignoring baseline when setting targets: Patient-specific targets should be based on documented preoperative baseline values 2
• Overlooking position-related changes: Prone positioning during spine surgery can cause significant decreases in stroke volume and cardiac index, leading to decreased blood pressure 4

By following these evidence-based recommendations for determining baseline blood pressure in spine surgery patients, anesthesiologists can better manage intraoperative hemodynamics and potentially reduce the risk of complications such as perioperative visual loss.