Shock index in the first trimester of pregnancy and its relationship to ruptured ectopic pregnancy.

UNLABELLED: The shock index (SI), the ratio of heart rate to systolic blood pressure, has been reported to be a useful tool in the evaluation of trauma patients presenting to the emergency department (ED).
OBJECTIVES: To determine the range of values for SI seen in first-trimester patients presenting to the ED, and to estimate the ability of the SI to predict ruptured ectopic pregnancy (EP).
METHODS: This was a prospective cohort study enrolling all patients in the first trimester of pregnancy presenting to the ED with abdominal pain and/or vaginal bleeding. Patients had a SI calculated based on their presenting vital signs, and were followed longitudinally to determine a final diagnosis. Ectopic pregnancies were categorized based on surgical pathology. Mean levels for SI were determined for each group, and ruptured EPs were compared with all other pregnancies using a receiver operating characteristic (ROC) curve.
RESULTS: The study enrolled 280 patients, 24 ruptured EPs, 28 unruptured EPs, and 228 non-EPs. The means for SI were 0.67 (95% CI = 0.65 to 0.68) for non-EPs, 0.64 (95% CI = 0.61 to 0.67) for unruptured EPs, and 0.84 (95% CI = 0.77 to 0.9) for ruptured EPs. The ROC curve for SI, heart rate, mean arterial pressure, and systolic blood pressure demonstrated areas under the curve (AUCs) of 0.84 (95% CI = 0.78 to 0.88), 0.74 (95% CI = 0.67 to 0.79), 0.63 (95% CI = 0.67 to 0.79), and 0.70 (95% CI = 0.64 to 0.77), respectively.
CONCLUSIONS: The range of values for SI for patients being evaluated for pain and/or vaginal bleeding within the first trimester of pregnancy, who do not have a ruptured EP, are within the previously reported range of 0.5-0.7 for nonpregnant patients. A SI > 0.85 made the diagnosis of ruptured EP 15.0 (95% CI = 5.6 to 40.4) times more likely. This study suggests that SI could impact directly on the diagnostic and therapeutic course of the patient.