Maternal BP and cardiac output are not much affected by spinal anesthesia: Study
Oslo, Norway: Maternal cardiac output (CO) and blood pressure (BP) at the time of cesarean delivery is equivalent to the levels before spinal anesthesia, finds a recent study in the journal BMJ Open.
In previous studies, the researchers have previously established a method for measuring the transfer of nutrients between mother, placenta, and fetus in vivo. The method included measurements of fetal and maternal blood flow by Doppler ultrasound prior to spinal anesthesia. Spinal anesthesia affects maternal BP and CO.
Against the above background, Trond Melbye Michelsen, Department of Obstetrics, Oslo University Hospital, Oslo, Norway, and colleagues aimed to determine the effect of spinal anesthesia in mothers undergoing an elective cesarean section on blood pressure, heart rate, and cardiac output, and whether cardiac output levels were comparable before induction of spinal anesthesia and before delivery.
For this purpose, the researchers conducted a prospective cohort study consisting of 76 healthy women with uneventful pregnancies undergoing an elective cesarean section from a tertiary hospital in Norway.
Spinal anesthesia was induced with standard prevention of hypotension including intravenous fluid co-loading and phenylephrine infusion.
The primary outcome measure was maternal cardiac output, and secondary outcome measures were invasive systolic blood pressure and heart rate.
The researchers measured heart rate and blood pressure by continuous invasive monitoring with a cannula in the radial artery. Cardiac output was estimated based on continuous arterial waveform. Then maternal parameters were compared 30 s before induction of spinal anaesthesia to 30 s before delivery.
The median age at delivery was 34.5 years and 17 of 76 women were nulliparous.
Key findings of the study include:
- The most prevalent indications were previous caesarean section and maternal request.
- Among 76 included women, 71 had sufficient data for analysis of endpoints.
- Median cardiac output was 6.51 L/min before spinal anaesthesia and 6.40 L/min before delivery.
- Median invasive systolic blood pressure increased from 128.5 mm Hg to 134.1 mm Hg, and mean heart rate decreased from 86.0 to 75.2.
"Our findings show that blood pressure and CO at delivery is comparable to values before spinal anesthesia when spinal anesthesia is combined with prophylactic low-dose phenylephrine infusion," concluded the authors.
The study titled, "Blood pressure and cardiac output during caesarean delivery under spinal anaesthesia: a prospective cohort study," is published in the journal BMJ Open.