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Defining a reference range for vital signs in healthy term pregnant women undergoing cesarean section
Abstract Number: SA-17
Abstract Type: Original Research
Introduction: Early warning systems(EWS), used to identify deteriorating patients, are based on measurement of vital signs(VS). When patients are pregnant, most EWSs still use non-pregnant reference ranges of VSs to determine trigger thresholds.1 Peripartum complications, including those that occur around the time of caesarean section must be recognised early. A common serious complication at this time is hemorrhage & it is essential that early warning signs of hemorrhage are recognised. From our clinical experience we had observed that many women with serious obstetric hemorrhage often had heart rates(HR) between 100-110 BPM & did not meet the trigger EWS threshold of 120 BPM & we thought that EWS triggers might need to be adjusted for pregnancy. There are no published reference ranges for all VSs in pregnancy. We aimed to define VS reference ranges for term pregnant women on the day of their cesarean birth & to determine appropriateness of current EWS triggers in pregnancy.
Method: After IRB approval we conducted a 1-year retrospective study in a tertiary referral obstetric hospital. The study sample was healthy term women(ASA I) undergoing planned cesarean section. Measurement of VS was performed by peri-operative nurses using standardized, automatic monitoring systems (Spot Vital Signs® WelchAllyn,NY,USA) to measure systolic & diastolic blood pressure(BP), HR, & oxygen saturation(SpO2). Respiratory rate(RR) was measured by counting the RR in a minute. Temperature(temp) was measured using a tympanic thermometer(Genius™ 2 AccuSystem, Covidien, Massachusetts, USA). Data were recorded in the pre-operative record & retrieved by study investigator(LH).
Results: 258 women met inclusion criteria. Mean± SD age, term body mass index,& gestation were 30±10.1 years, 29±3.4 kg.m-2, 39±1.2 weeks respectively. Vital sign data for the study group compared with current Modified Early Obstetric Warning Score(MEOWS) triggers are shown in the Table as well as a proposed healthy reference range based on study mean values ±2SD.
Conclusions: This study has helped define a reference range for vital signs in healthy term pregnant women on the day of cesarean birth. Study findings suggest that currently used criteria for EWS triggers, based on non-pregnant values, are too extreme for timely detection of deteriorating pregnant patients especially for HR. We suggest HR triggers be modified to ≤50 & ≥110 BPM in pregnant women.
Reference: 1.Singh S et al. Anaesthesia 2012;67:12-8.