Effects of Spinal Anesthesia during Elective Caesarean Section on Neonatal outcome at the Kenyatta National Hospital

Abstract

Utero-placental circulation and hence fetal well-being depends on maternal blood pressure. Spinal anesthesia for cesarean section causes sudden and severe drops in blood pressure thus threatening fetal and neonatal acid-base balance. Several protocols have been formulated to prevent maternal hypotension but none has been shown to totally eliminate this risk.

This was a prospective non-randomized descriptive study that adopted a consecutive sampling method. All eligible ASA (American Society of Anesthesiologists) I and ASA II mothers slated for elective cesarean section at the Labour Ward of The Kenyatta National Hospital in Nairobi were visited in the ante-natal ward the day or night before surgery and an informed consent obtained for inclusion in the study. Any pre-selected mother who ended up needing emergency surgery or changed her mind about inclusion in the study was excluded. Similarly, any willing mother who did not qualify for spinal anesthesia was excluded from the study. A sample size of 172 cases was taken and this required approximately 15 weeks of data collection. Maternal blood pressures were recorded every minute until delivery. Immediately after delivery, a section of the umbilical cord was clumped with 2 clumps. Umbilical arterial and venous blood samples were collected in heparinized syringes and taken to the laboratory within one hour of collection and analyzed for blood gases and pH as a measure of foetal! neonatal compromise. Apgar scores were also noted at birth and after 5 minutes and later correlated with the cord blood gas analyses and maternal blood pressures. The anesthesia provider was requested to complete a data sheet which was then collected by the principal investigator on the same day the surgery was performed. Data analysis was done using SPSS software version 16.0 and presented in the form of tables, graphs and charts.

A total of 172 patients were successfully recruited into the study and the total number of umbilical cord blood samples analyzed (both arterial and venous) was 316. 28 blood samples clotted and were not available for analysis. 43 babies (27.2%) were born with neonatal acidemia defined as umbilical arterial blood pHS 7.2. There was, however, no significant relationship between neonatal acidemia and low Apgar scores; neither was there a significant relationship between low Apgar scores and maternal hypotension. 104 patients (65.8%) had a wedge inserted under the right hip as recommended for prevention of aorto-caval compression. There was, however, no significant difference in the incidence of maternal hypotension among those with a wedge and those without. Vasopressors were used in 84 patients (53.2%). These included the use of ephedrine alone or epinephrine alone or a combination of the two in the process of treating or preventing maternal hypotension. The use of Va sopressors resulted in significantly fewer incidences of hypotension (p=0.018). The use of preload with crystalloids before induction of spinal anaesthesia was noted to be significantly related to the use of Vasopressors whenever the volume of preload was less than 500mls (p=0.027). Similarly, maximum levels of spinal block above T6 resulted in significant incidences of maternal hypotension (p=O.OO1). Maternal height < 155cm did not have any significant effect on the incidence of maternal hypotension.

Maternal hypotension can lead to poor neonatal outcome due to its effects on placental perfusion and hence foetal oxygenation. This study has shown that vasopressor use during spinal anaesthesia effectively minimizes the incidence of maternal hypotension. Crystalloid preload of over 500mls is effective in preventing or moderating maternal hypotension. A well conducted spinal anaesthetic for caesarean section with meticulous control/management of adverse effects results in healthy neonates and mothers.