respiratory changes during spinal anaesthesia for gynaecological laparoscopic surgery

Background: It is currently presumed that spinal anaesthesia can compromise respiratory muscle function during carbon dioxide (CO2) pneumoperitoneum. This observational study was designed to delineate the respiratory effects of CO2 pneumoperitoneum under spinal anaesthesia. Patients & Methods: Forty one patients undergoing elective gynecological laparoscopy were administered spinal anaesthesia with 15 mg heavy bupivacaine and 50 mcg of fentanyl. Heart rare, blood pressure, tidal volume, respiratory rate and end tidal CO2 were serially recorded before, during and after the pneumoperitoneum. Arterial blood gas analysis was done before and 20 min after initiation of pneumoperitoneum. Results: The mean heart rate and blood pressure decreased by less than 20% of the preoperative value. The mean tidal volume decreased from 353 ± 81(Standard Deviation) to 299±95 ml, p = 0.032, over the first 9 min after the pneumoperitoneum with a complete recovery towards the base line, 340 ± 72 ml, within 30 min during the surgery. The maximal inspiratory capacity declined from 1308±324 ml to 1067±296 ml at 20 min and recovered to 1187±267 ml, 5min after decompression. There was no observed change in the respiratory rate. Similarly, increase in the end tidal CO2 from 31.68±4.13 to 37.62±4.21 mmHg, p = 0.000, reached a plateau around 15 min and declined after decompression. Arterial carbon dioxide showed a corresponding increase at 20 min without change in arterial to end tidal CO2 difference. All observed changes were within the physiological limits. Conclusion: In a conscious patient undergoing laparoscopy with pneumoperitoneum, under spinal anaesthesia, the preserved inspiratory diaphragmatic activity maintains ventilation and, the gas exchange within physiological limits. Hence it is a safe alternative to general anaesthesia.