A Prospective Observational Comparison Between Arm and Wrist Blood Pressure During Scheduled Cesarean Delivery.

BACKGROUND

Shivering is common during cesarean delivery (CD) under neuraxial anesthesia and may disrupt the measurement of noninvasive blood pressure (BP). BP measured at the wrist may be less affected by shivering. There have been no studies comparing trends in BP measured on the upper arm and wrist. We hypothesized that wrist systolic blood pressure (sBP) would accurately trend with upper arm sBP measurements (agree within a limit of ±10%) in parturients undergoing elective CD under spinal anesthesia or combined spinal-epidural anesthesia.

METHODS

After initiation of spinal anesthesia, BP measurements were obtained simultaneously from the upper arm and wrist on opposite arms. The interval between measurements was 1 to 2 minutes, and data were collected for 20 minutes or until delivery. The primary outcome was agreement in dynamic changes in sBP measurements between the upper arm and the wrist. Bland-Altman plots indicating the levels of agreement between the methods were drawn for baseline measurements, over multiple measurements, and over multiple measurements on percentage change from baseline.

RESULTS

Forty-nine patients were recruited and completed the study. The wrist sBP tended to overestimate the upper sBP for both baseline data (sBP bias = 13.4 mm Hg; 95% confidence interval = +10.4 to +16.4 mm Hg) and data obtained over multiple measurements (sBP bias = 12.8 mm Hg; 95% confidence interval = +9.3 to +16.3 mm Hg). For change in sBP from baseline over multiple measurements, the mean difference between the wrist and the arm sBP was -0.2 percentage points (99% limits of agreement -25 to +25 percentage points).

CONCLUSIONS

The wrist measurement overestimated the reading relative to the upper arm measurement for multiple measurements over time. However, when the time series for each subject was examined for percentage change from baseline, the 2 methods mirrored each other in most cases. Nevertheless, our hypothesis was rejected as the limits of agreement were higher than ±10%. This finding suggests that wrist BP may not be an accurate method of detecting hypotension or hypertension during spinal or combined spinal-epidural anesthesia for CD.