Changes in cardiac index during labour analgesia: A double-blind randomised controlled trial of epidural versus combined spinal epidural analgesia - A preliminary study

Abstract

Background and aims: Combined spinal-epidural (CSE) analgesia for labour and delivery is occasionally associated with foetal bradycardia. Decreases in cardiac index (CI) and/or uterine hypertonia are implicated as possible aetiological factors. No study has evaluated CI changes following combined spinal analgesia for labour and delivery. This prospective, double-blind, randomised controlled trial evaluates haemodynamic trends during CSE and epidural analgesia for labour.

Methods: Twenty-six parturients at term requesting labour analgesia were randomised to receive either epidural (E) or CSE analgesia. The Electrical Cardiometry Monitor ICON^® was used to continuously determine maternal CI non-invasively, heart rate (HR) and stroke volume at baseline and up to 60 min after initiation of either intrathecal or epidural analgesia. In addition, maternal systolic blood pressure (SBP) and diastolic blood pressure (DBP) were recorded.

Results: Both SBP and DBP had a similar, significant decrease following initiation of either epidural or CSE analgesia. However, parturients in the CSE group (n = 10) demonstrated a significant decrease in HR and CI compared to the baseline measurements. On the other hand, the parturients in the E (n = 13) group showed no decreases in either maternal HR or CI. Foetal heart changes were observed in four patients following CSE and one patient following an epidural.

Conclusion: Labour analgesia with CSE is associated with a significant decrease in HR and CI when compared to labour analgesia with epidural analgesia. Further studies are necessary to determine whether a decrease in CI diminishes placental blood flow.

Keywords: Cardiac output; combined spinal epidural; epidural labour analgesia.

Figure 1

Consort flow diagram of number of parturients recruited, number completed in each group, ephedrine use in each group and foetal heart rate changes observed

Figure 2

Cardiac index versus time. Solid lines = E group, n = 13. Dotted lines = Combined spinal epidural group, n = 10. Cardiac index continuous data expressed from time zero, regional analgesia bolus completion, up to 60 min

Figure 3

A cardiac index (cardiac output/body surface area) measured at 1 min intervals up to 60 min following initiation of epidural or combined spinal-epidural analgesia. Solid line represents the average values of the combined spinal epidural group (n = 10). Dotted line represents the average values of the E group (n = 13). No difference between the two groups at baseline. Statistical significance starts at 15 min (P = 0.006) after initiation of bolus. The difference between the two groups continues until 45 min (P = 0.0003). No difference noted from 45 min to 60 min. *P < 0.05, significant change from baseline within the same group, **P < 0.05, significant difference at specific time point between the two groups

Figure 4

Heart rate trends measure at baseline, 15 min, 30 min, 45 min and 60 min following initiation of E or combined spinal-epidural analgesia. Solid line represents the average values of the combined spinal epidural group (n = 10). Dotted line represents the average values of the E group (n = 13). *P < 0.05, a significant change from baseline within the same group. There is no difference between combined spinal epidural and E group throughout all time points. However, heart rate drops significantly within the combined spinal epidural group

Figure 5

(a) Systolic blood pressure measured at baseline, 15 min, 30 min, 45 min, and 60 min in following the initiation of combined spinal epidural or E analgesia. Solid line represents the average values of the combined spinal epidural group (n = 10). Dotted line represents the average values of the E group (n = 13), (b) diastolic blood pressure measured at baseline, 15 min, 30 min, 45 min and 60 min following initiation of combined spinal epidural or E analgesia. Solid line represents the average values of the combined spinal epidural group (n = 10). Dotted line represents the average values of the E group (n = 13). *P < 0.05, significant change from baseline within the same group. No difference between the two groups throughout