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Influence of position and mode of uterine displacement on the hemodynamic status of third trimester pregnant women
Abstract Number: S-40
Abstract Type: Original Research
Introduction: Current guidelines for resuscitation of the pregnant woman suggest manual uterine displacement as the ideal method of alleviation of the aortocaval compression. If this proves to be unsuccessful, providers are encouraged to pursue the left lateral tilt position at 27-30 degrees (1). Such recommendation is based on manikin studies that have shown that chest compressions in the left-lateral tilt position are feasible, although they may be less effective than in the supine position (2). No study to date has looked at the full array of positions and aortocaval alleviation methods using a continuous assessment of hemodynamics.
Methods: This was a prospective observational study. With REB approval and written informed consent we recruited non-laboring women ≥ 34 weeks gestational age. We excluded ASA 3/4, BMI >35, multiple gestation, cardiac disease, hypertension or preeclampsia, renal disease, anemia Hb < 10 g/dl, IUGR and abnormal placentation. Participants were monitored with a bio-reactance based non-invasive cardiac output monitor (NICOM). The system was allowed to equilibrate with women in the left lateral position (LL) for 2 minutes, after which the hemodynamic data collection was initiated. Participants were moved into the following positions: left lateral (LL); 30 degree left tilt (LT); supine (S); supine with left manual displacement (LMUD); 30 degree right tilt (RT); right lateral (RL). Participants remained in each of the positions for 5 minutes and data for analysis was collected during the last 3 minutes. The hemodynamic variables were: systolic (SBP), diastolic (DBP), mean arterial pressure (MAP), heart rate (HR), stroke volume (SV) and stroke volume index (SVi), cardiac output (CO) and cardiac index (CI), total peripheral resistance (TPR) and total peripheral resistant index (TPRi). The primary outcome was the CI in different study positions
Results: We approached 32 women, recruited 31 and analyzed data from 30. There were significant changes in SBP; DBP; MAP; TPR; and TPRi (p<0.01). The mean values increased as the patients moved from LL thru the different positions until they were placed in RL. There were no significant changes in CO, CI, HR, SV and SVi across all positions. One patient (not included in the analysis) presented severe symptoms of aortocaval compression while supine accompanied by abrupt decreases in SV, CO and CI, and increases in HR and TPR, and only improved with LL position.
Discussion: In the absence of anesthesia, most pregnant women tolerate various positions with minor hemodynamic consequences, primarily by increasing peripheral resistance; in these women LMUD does not change the hemodynamic profile. Some women, however, will exhibit severe symptoms and hemodynamic changes associate with aortocaval compression; in these women, LMUD or LT may not be sufficient to attenuate/correct these changes.
References: 1) Circulation 2012; 12:833-838; 2) Anesthesia 2013; 68:694-699