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Pulse pressure and carotid artery Doppler velocimetry as indicators of maternal volume status: a prospective cohort study
Abstract Number: F-38
Abstract Type: Original Research
Narrow pulse pressure (PP) has been demonstrated to indicate low central volume status. Volume status can also be estimated using Doppler velocimetry to assess hemodynamic changes in the carotid artery in response to autotransfusion with passive leg raise (PLR). Neither parameter has been prospectively evaluated in an obstetric population. The objective of this study was to assess PP and carotid artery Doppler as indicators of volume status in hemodynamically stable intrapartum women.
Healthy women with singleton gestations ≥35 weeks were recruited to this prospective cohort study. After informed consent, maternal carotid artery Doppler assessment was performed in all patients before and after PLR using a standard technique where carotid blood flow = π x (carotid artery diameter/2)² x (velocity time integral) x heart rate . The velocity time integral was calculated from the Doppler wave form with angle adjustment. Participants were grouped by PP prior to PLR as 45 mmHg (narrow) or 50 mmHg (normal). We evaluated changes in carotid artery Doppler parameters after PLR within and between study groups.
33 women participated including 18 in the narrow and 15 in the normal PP groups (mean and standard deviation initial PP 57.3 ± 4.1 vs. 38.3 ± 4.4 mmHg). Initial vital signs, hemoglobin, BMI and obstetric characteristics were otherwise similar between groups. Carotid artery diameter and flow increased after PLR in both groups. The narrow PP group had a significantly greater increase in carotid artery diameter (0.08 vs. 0.02 cm, p<0.0001), carotid blood flow (79.4 vs. 16.0 mL/min, p<0.0001) and percent change in carotid blood flow (47.5 vs. 8.7%, p<0.0001) compared with the normal group. Initial PP was strongly correlated with the change in carotid flow after PLR (r²=0.60, p<0.0001).
The hemodynamic response of the carotid artery to autotransfusion after PLR is significantly greater in women with narrow PP. This study provides physiologic evidence suggesting a strong correlation between PP and central volume status in hemodynamically stable obstetric patients. If corroborated, these methods of indirect volume assessment may guide the individualization of intrapartum fluid management.
1. Marik PE et al. The use of bioreactance and carotid Doppler to determine volume responsiveness and blood flow redistribution following passive leg raising in hemodynamically unstable patients. Chest. 2013;143:364-70.