Comparison of phenylephrine infusion regimens for maintaining maternal blood pressure during spinal anaesthesia for Caesarean section |
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Authors: | Ngan Kee W D Khaw K S Ng F F |
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Affiliation: | Department of Anaesthesia and Intensive Care, The Chinese University of Hong Kong,Prince of Wales Hospital, Shatin, Hong Kong, China |
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Abstract: | Background. During spinal anaesthesia for Caesarean section,the optimal phenylephrine regimen and the optimal blood pressure(BP) to which it should be titrated are undetermined. The idealregimen would balance efficacy for maintaining uteroplacentalperfusion pressure against potential for uteroplacental vasoconstriction,both of which may affect fetal acidbase status. We comparedphenylephrine infusion regimens based on three different BPthresholds. Methods. After intrathecal injection, we infused phenylephrine100 µg min1 for 2 min. Then, until delivery,we infused phenylephrine whenever systolic BP (SBP), measuredevery 1 min, was below a randomly assigned percentage of baseline:100% (Group 100, n=25), 90% (Group 90, n=25) or 80% (Group 80,n=24). We compared umbilical blood gases, Apgar scores and maternalhaemodynamics and symptoms. Results. Patients in Group 100 had fewer episodes [median 0(range 08)] of hypotension (SBP <80% baseline) comparedwith Group 80 [5 (018)] and Group 90 [2 (07)](P<0.001 in each instance). Total dose of phenylephrine wasgreater in Group 100 [median 1520 µg (interquartile range12502130 µg)] compared with Group 90 [1070 (8901360)µg] and Group 80 [790 (590950) µg]. Umbilicalarterial pH was greater in Group 100 [mean 7.32 (95% confidenceinterval 7.317.34)] than in Group 80 [7.30 (7.287.31)](P=0.034). No patient had umbilical arterial pH <7.2. InGroup 100, 1/24 (4%) patients had nausea or vomiting comparedwith 4/25 (16%) in Group 90 and 10/25 (40%) in Group 80 (P=0.006). Conclusions. For optimal management, phenylephrine should betitrated to maintain maternal BP at near-baseline values. Br J Anaesth 2004; 92: 46974 |
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Keywords: | anaesthetic techniques, subarachnoid complications, hypotension surgery, Caesarean section sympathetic nervous system, phenylephrine |
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