title: Acid-base state of cerebrospinal fluid during pregnancy and its effect on spread of spinal anaesthesia.
abstract: To assess the possible relationship between changes in acid-base state of cerebrospinal fluid (CSF) and enhanced spread of spinal anaesthesia during pregnancy, we have measured CSF pH, carbon dioxide tension (PCO2) and HCO3- values in 73 women undergoing spinal anaesthesia with hyperbaric amethocaine 8 mg. Patients were allocated to one of four groups according to gestational period: non-pregnant group (n = 13), first trimester group (8-13 weeks, n = 19), second trimester group (14-26 weeks, n = 11) and third trimester group (27-39 weeks, n = 30). The pH of the CSF was greater in the second and third trimester groups than in the non-pregnant group. CSF PCO2 decreased by 0.53-0.8 kPa throughout pregnancy. CSF HCO3- was decreased throughout pregnancy. Overall, no clinically significant correlation was found between maximum cephalad spread of analgesia and CSF pH, PCO2 or HCO3-. We conclude that pregnancy-induced changes in acid-base state of CSF have little effect on the spread of spinal anaesthesia, although there is a clinically different spread of spinal anaesthesia between non-pregnant and pregnant states.
authors.affiliation: Department of Anaesthesiology, Jichi Medical School, Tochigi, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Hirabayashi
authors.forename: R
authors.initials: R
authors.lastname: Shimizu
authors.forename: K
authors.initials: K
authors.lastname: Saitoh
authors.forename: H
authors.initials: H
authors.lastname: Fukuda
authors.forename: T
authors.initials: T
authors.lastname: Igarashi
mesh_terms: D000136:Acid-Base Equilibrium / Q000502:physiology*; D000328:Adult; D000773:Anesthesia, Obstetrical; D000775:Anesthesia, Spinal; D000779:Anesthetics, Local / Q000493:pharmacokinetics*; D001639:Bicarbonates / Q000134:cerebrospinal fluid; D002245:Carbon Dioxide / Q000134:cerebrospinal fluid; D005260:Female; D005865:Gestational Age; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008875:Middle Aged; D010313:Partial Pressure; D011247:Pregnancy / Q000134:cerebrospinal fluid*; D013748:Tetracaine / Q000493:pharmacokinetics
chemical_list: D000779:Anesthetics, Local; D001639:Bicarbonates; D013748:Tetracaine; D002245:Carbon Dioxide