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Effect of Supine-to-tilt and Lateral-to-tilt Positioning on Maternal and Fetal Outcomes in Parturients Undergoing Cesarean Delivery with Spinal Anesthesia
Abstract Number: S-9
Abstract Type: Original Research
Introduction: Sympathectomy induced by spinal anesthesia(SAB) further exaggerates aortocaval compression(ACC) in parturients undergoing cesarean delivery(C/S). Therefore, parturients are placed at 10-15°left tilt after SAB for C/S. However, several studies have suggested that ACC may not be effectively relieved by even a 34° tilt, if assumed from an initial supine position. The uterus is relatively immobile and may remain over the major vessels when the patient is tilted from a supine position. More favorable doppler velocimetry indices in uterine and umbilical arteries were demonstrated when parturients were placed lateral first then to a tilt position(LTT)as compared to supine first then to tilt(STT). Still other studies show a significant improvement in mean arterial pressure and a lower heart-rate with LTT over STT positioning. The difference in effectiveness of relieving ACC and maternal/fetal outcomes (maternal hypotension, N/V, vasopressor use) between LTT and STT positioning in parturients receiving SAB for C/S has not been studied and is the goal of this study.
Hypothesis:LTT positioning is more effective than STT positioning in relieving ACC in parturients undergoing C/S under SAB if vasopressor need, maternal hypotension, and/or maternal N/V are decreased.
Method:50(25/gp) parturients scheduled for elective C/S under SAB will be consented to be enrolled and randomized to either STT or LTT group in order to detect a 40% difference in emetic symptoms with α=0.05 and Power=0.80. SAB was administered in a sitting position. Immediately after SAB, patients were placed left lateral or supine for 5 seconds in the LTT or STT gp, respectively, both followed by tilting to 12° left as measured by an inclinometer. Vitals signs and emetic symptoms were assessed every minute till fetus delivered. Phenylephrine IV infusion at 100mcg/min was initiated at SAB injection and continued till fetus delivered if anytime patient's systolic BP ≤ her average baseline.
Results:So far 33(16 LTT,13 STT,4 excluded)patients were enrolled. Preliminary analysis showed no demographic differences between gps. Incidence of nausea in the LTT gp was significantly lower at 19% compared to the STT gp at 62%, p < 0.02. Average phenylephrine required was less in the LTT gp at 0.52+/-0.30 mcg/kg/min, versus STT gp at 0.70+/-0.30 mcg/kg/min, p < 0.07. The incidence of bradycardia(HR<60/min) was less in the LTT gp at 31% versus the STT gp at 69%, p < 0.07. Incidence of hypertension(>120% baseline)or hypotension(<80% baseline), vomiting, and Apgars were similar between gps.
Discussion:It appears the LTT positioning will have a decreased incidence of nausea, a lower vasopressor need and a lower incidence of bradycardia than the STT positioning. A simple LTT maneuver after SAB for C/S may provide an easy, practical way to make a positive difference in patient outcomes and experience over STT. Final completed data will be presented at SOAP.
Ref:Bamber et al. A&A 2003;97:256-8.