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Comparison of Upper Arm and Wrist Non-invasive Blood Pressure Measurements in Elective Cesarean Delivery under Spinal Anesthesia. Prospective Observational Study.
Abstract Number: T-20
Abstract Type: Original Research
Shivering during cesarean delivery (CD) can interfere with upper arm non-invasive blood pressure (NIBP) measurements (1). An audit revealed failure of NIBP measurement to be 38% after epidural top-up and 9% after spinal anesthesia during deliveries in the operating room (2). NIBP measured at the wrist may suffer less shivering interference. We hypothesized that wrist systolic blood pressure (sBP) would accurately trend with upper arm sBP measurements in parturients undergoing elective CD under spinal block.
After obtaining ethics board approval and signed informed consent, 49 patients were approved on the eligibility criteria and completed the study. After neuraxial anesthesia, sBP measurements were obtained simultaneously from both upper arm and wrist on opposite limbs, using 2 monitors from the same model (Carescape V100, GE Healthcare, Finland). Interval between measurements was 1-2 minutes and data was collected for 20 minutes or until delivery.
Bland-Altman Plots indicating the level of agreement between the methods were drawn for baseline measurements, over multiple measurements and over multiple measurements on percentage change from baseline (20% change in sBP was considered to be clinically significant, as this change normally triggers treatment by the anesthesiologist).
Overall, the wrist NIBP tended to overestimate the upper arm NIBP both for baseline data (sBP bias = 13.4 mmHg; 95% CI = 10.4 – 16.4 mmHg) and for data obtained over multiple measurements (sBP bias = 12.8 mmHg ;95% CI = -11.4 and 36.9 mmHg).
Nevertheless, when we analyzed percentage change, up and down, from baseline over multiple measurements, the mean difference between the wrist and arm sBP was 0.26%, with the limits of agreement between -9.3 and 9.8%.
When data was analyzed for agreement of baseline measurements and over multiple measurements, the wrist measurement overestimated the reading on average relative to the upper arm measurement. This was expected, as demonstrated by previous studies (3).
However, when the time-series for each subject is examined for percentage change from baseline, it is clear that the two methods track each other quite well.
This suggests that tracking percentage change of wrist NIBP from baseline may be an adequate substitute for tracking percentage change from upper arm NIBP.
1) Reg Anesth Pain Med 2007, 33, 241-5.
2) SOAP Annual Meeting 2013, S1.
3) Blood Press Monit, 9, 77-81