Blood pressure and cardiac output during caesarean delivery under spinal anaesthesia: a prospective cohort study

Abstract

Objectives: We have previously established a method to measure transfer of nutrients between mother, placenta and fetus in vivo. The method includes measurements of maternal and fetal blood flow by Doppler ultrasound prior to spinal anaesthesia. Spinal anaesthesia affects maternal blood pressure and cardiac output. We aimed to determine the effect of spinal anaesthesia in mothers undergoing an elective caesarean section on blood pressure, heart rate and cardiac output, and whether cardiac output levels were comparable before induction of spinal anaesthesia and before delivery.

Design: Prospective cohort study.

Setting: Tertiary hospital in Norway.

Participants: 76 healthy women with uneventful pregnancies undergoing an elective caesarean section.

Interventions: We induced spinal anaesthesia with a standard prevention of hypotension including intravenous fluid coloading and phenylephrine infusion.

Primary and secondary outcome measures: Primary outcome measure was maternal cardiac output, and secondary outcome measures were invasive systolic blood pressure and heart rate. We 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. We compared maternal parameters 30 s before induction of spinal anaesthesia to 30 s before delivery.

Results: Median age at delivery was 34.5 (range 21-43) years and 17 of 76 women were nulliparous. 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 (IQR (5.56-7.54) L/min before spinal anaesthesia and 6.40 (5.83-7.56) L/min before delivery (p=0.40)). Median invasive systolic blood pressure increased from 128.5 (120.1-142.7) mm Hg to 134.1 (124.0-146.6) mm Hg (p=0.014), and mean heart rate decreased from 86.0 (SD 13.9) to 75.2 (14.2) (p<0.001).

Conclusions: Maternal cardiac output at the time of caesarean delivery is comparable to levels before induction of spinal anaesthesia.

Trial registration number: NCT00977769.

Keywords: anaesthesia in obstetrics; maternal medicine; obstetrics.

Conflict of interest statement

Competing interests: None declared.

© Author(s) (or their employer(s)) 2021. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.

Figures

Figure 1

Flowchart showing inclusion of participants. In the original study, 185 participants were approached for inclusion, and 76 participated (13). In this study, 5 more participants were excluded due to technical measurement issues, thus leaving 71 participants for graphical presentations and 70 for statistical analysis.

Figure 2

Systolic AP, HR and CO at the time of spinal anaesthesia and at delivery (N=71). Level of systolic AP, HR and CO around the time that spinal anaesthesia was given (A, C and E), and for the last minutes until delivery (B, D and F). The thick solid line marks the mean over all participants, and the grey area represents ±SD. AP, arterial pressure; CO, cardiac output; HR, heart rate.

Figure 3

Alterations in CO before and after induction of spinal anaesthesia and until delivery in every participant (N=71). (A)Time relative to induction of spinal anaesthesia with participants on the vertical axis and CO levels described by colours as described in the scale to the right. Participants are ranked from highest to lowest based on CO levels at −3 min. (B) Time relative to delivery with participants on the vertical axis and CO levels described by colours as described in the scale to the right. Participants are ranked from highest to lowest based on CO levels at −3 min in (A). Darker colour indicates lower CO and lighter colour indicates higher CO. CO, cardiac output.

Figure 4

Changes in maternal SAP, CO and HR from before induction of spinal anaesthesia compared with before delivery. changes in median of (A) SAP, (B) CO and (C) HR from just before induction of spinal anaesthesia to just before delivery, presented in boxplots according to the Tukey method (N=70). CO, cardiac output; HR, heart rate; SAP, systolic arterial pressure.

Figure 5

Individual systolic arterial blood pressure data for all 71 included participants from induction of spinal anaesthesia to delivery. Individual systolic arterial pressure data in mm Hg for each participant from 3 min before induction of spinal anaesthesia until delivery. The vertical, red-dashed line indicates the time of spinal administration. Yellow fields indicate periods with low technical quality. These periods were not part of the calculations. All recordings are filtered using a median filter with a window of 60 beats. Time on the horizontal axis in minutes.

Figure 6

Individual heart rate data for all 71 included participants from induction of spinal anaesthesia to delivery. Individual heart rate data in mm Hg for each participant from 3 min before induction of spinal anaesthesia until delivery. The vertical, red-dashed line indicates the time of spinal administration. Yellow fields indicate periods with low technical quality. These periods were not part of the calculations. All recordings are filtered using a median filter with a window of 60 beats. Time on the horizontal axis in minutes.

Figure 7

Individual CO data for all 71 included participants from induction of spinal anaesthesia to delivery. Individual cardiac output data in mm Hg for each participant from 3 min before induction of spinal anaesthesia until delivery. The vertical, red-dashed line indicates the time of spinal administration. Yellow fields indicate periods with low technical quality. These periods were not part of the calculations. All recordings are filtered using a median filter with a window of 60 beats. Time on the horizontal axis in minutes.