Are post-surgical inpatient blood pressures (BPs) similar to pre-surgery blood pressure values?

Post-Surgical Blood Pressure Patterns Compared to Pre-Surgery Values

Post-surgical inpatient blood pressures are typically not similar to pre-surgery values, as patients commonly experience more labile hemodynamic profiles in the postoperative period, especially those with pre-existing hypertension. 1

Hemodynamic Changes After Surgery

Common Blood Pressure Patterns

• Patients with hypertension (controlled or uncontrolled) demonstrate a more labile hemodynamic profile than their non-hypertensive counterparts 1
• Postoperative hypertension typically:
  • Begins within 30 minutes after surgery
  • Lasts approximately 2 hours in most cases
  • Can persist for 3+ hours in about 20% of patients (associated with higher complication rates) 2
• Hypotension is also common, with 20% of patients experiencing clinically significant hypotension (systolic <90 mmHg requiring intervention) in the perioperative period 1

Mechanisms of Blood Pressure Variability

• During emergence/early postoperative period:

  • Sympathetic activation from pain and emergence from anesthesia 1
  • Exaggerated hemodynamic responses to pain and emergence are more common in hypertensive patients 1
  • Contributing factors: pain (35%), hypercarbia (15%), emergence excitement (16%) 2

• Intraoperative to early postoperative period:

  • Reduction in systemic vascular resistance after anesthesia induction
  • Loss of baroreceptor reflex control
  • Direct effects of anesthetic agents
  • Central neuraxial blockade effects 1

Clinical Implications and Management

Risk Assessment

• Significant BP fluctuations (increases or decreases of ≥20 mmHg in MAP) lasting 60+ minutes are associated with 19% risk of postoperative cardiac complications 3
• Risk of harm from hypotension increases with duration, particularly when systolic BP <90 mmHg 1
• For hypertensive patients, the threshold at which harm occurs may be higher than systolic 90 mmHg 1

Monitoring Recommendations

• The Perioperative Quality Initiative recommends creating patient-specific postoperative BP target ranges based on baseline preoperative measurements 4
• Significant deviations requiring intervention are typically <75% or >140% of baseline 4
• More intensive monitoring is warranted for patients with:
  • Previous myocardial infarction
  • Cardiomegaly
  • Pre-existing hypertension 3

Management Approach

• Establish accurate baseline BP using multiple readings prior to surgery 4
• For patients with normal baseline BP, maintain systolic >90 mmHg and <160 mmHg 4
• Treat reversible causes of hypertension first: pain, anxiety, hypothermia, and hypoxemia 5
• Consider that patients with unchanged baroreceptor sensitivity after surgery show more pronounced BP instability 6

Important Caveats

• Pitfall #1: Relying on post-surgical BPs to determine pre-surgical baseline is fundamentally flawed and contradicts established guidelines 4
• Pitfall #2: Assuming all patients should have the same BP targets regardless of their baseline values can lead to inappropriate management 4
• Pitfall #3: Failing to recognize that BP variability itself (not just absolute values) may be associated with adverse outcomes 6
• Pitfall #4: Inadequate monitoring frequency on surgical wards can miss extended periods of hypotension, particularly on POD 1-4 when risk of complications from hypotension is nearly three times higher 1

While evidence suggests associations between postoperative BP alterations and adverse outcomes, robust evidence for causal relationships is still lacking, and more research is needed to determine if preventing or treating these alterations reduces complications 7.