• W D Ngan Kee, Y H Tam, K S Khaw, F F Ng, L A Critchley, and M K Karmakar.
• Department of Anaesthesia and Intensive Care, The Chinese Unviersity of Hong Kong, Prince of Wales Hospital, HShatin, Hong Kong, China. warwick@cuhk.edu.hk
• Anaesthesia. 2007 Dec 1;62(12):1251-6.

AbstractWe describe the novel use of a closed-loop feedback computer-controlled infusion of phenylephrine for maintaining blood pressure in 53 patients having spinal anaesthesia for elective caesarean section. A simple on-off algorithm was used that activated an intravenous phenylephrine infusion at 100 microg.min(-1) when systolic blood pressure was less than or equal to baseline and stopped the infusion when systolic blood pressure exceeded baseline. Up to uterine incision, 94.6% of all systolic blood pressure measurements were within the range (baseline +/- 20%). Seven patients (13.2%) had one or more episodes of hypotension (systolic blood pressure < 80% of baseline) and 23 patients (37.7%) had one or more episodes of hypertension (systolic blood pressure > 120% of baseline). No patient had nausea or vomiting and in no case was umbilical arterial blood pH < 7.2. Calculated system performance parameters were comparable with those of previously published closed-loop systems and provide a reference for the potential development and comparison of more advanced algorithms.

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