A greater decrease in blood pressure after spinal anaesthesia in patients with low entropy of the RR interval.

Area of Science:

• Anesthesiology
• Cardiovascular Physiology
• Medical Technology

Background:

• Spinal anesthesia (SA) can cause hypotension, a common complication.
• Predicting hypotension risk pre-operatively is crucial for patient management.
• Heart rate variability (HRV) is a potential indicator of autonomic nervous system function.

Purpose of the Study:

• To evaluate if pre-operative heart rate variability (HRV), measured by the MemCalc method, predicts hypotension following spinal anesthesia (SA).
• To assess the utility of ultra short-term entropy (UsEn) as a non-linear HRV index for predicting post-SA hypotension.

Main Methods:

• Fifty-two patients (ASA I-II, 38-84 years) undergoing elective transurethral surgery were studied.
• Ultra short-term entropy (UsEn) was measured pre- and post-SA using the MemCalc method.
• Patients were grouped based on pre-operative UsEn (LO vs. HI) and hemodynamic changes post-SA were compared.

Main Results:

• Spinal anesthesia significantly decreased the LF/HF ratio but did not alter UsEn.
• A greater percentage decrease in systolic blood pressure (SBP) was observed in the low UsEn group (17.5%) compared to the high UsEn group (11.4%).
• The incidence of hypotension was significantly higher in patients with low pre-operative UsEn.

Conclusions:

• Pre-operative ultra short-term entropy (UsEn) measured by the MemCalc method is a significant predictor of hypotension after spinal anesthesia.
• Patients with lower pre-operative UsEn levels are at increased risk for developing hypotension post-SA.
• The MemCalc method provides a valuable tool for assessing pre-anesthetic risk of hypotension.