Diagnostic accuracy of admission lactate for injury severity and as a predictor of early outcome among trauma patients in Mulago Hospital
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Background: Trauma is the leading cause of death in the developed world. In Mulago hospital, it is the single most common indication for admission in the surgical wards. The Kampala Trauma Score II , recommended for use in resource poor setting is a modification of the Injury Severity Score and the Revised Trauma Score and it compares well with the New Injury Severity Score. Objective of this study was to determine the diagnostic accuracy of admission venous lactate levels for injury severity and predict early outcome. Methods: This was a mixed design study with both a cross-sectional design to determine injury severity and prospective cohort design to predict early outcome. A total of 502 trauma patients were conveniently and consecutively recruited daily over a period of 2 months from the A and E department of Mulago Hospital. Pre-resuscitation venous lactate levels were determined on arrival to the emergency department and the patient concurrently given a KTS II score .Admitted patients were followed up for 72 hours to assess early outcome while those treated and sent home were noted as outcome occurred. Results:A total of 108(21.51%) patients had severe injury and 394(78.48%) had non-severe injuries, 183 were admitted and 319 were not admitted. There was a significant difference between median(IQR) lactate level in the severe trauma patients which was 4.29(2.61,6.64) and in the non-severe trauma patients 2.40(1.62,3.45), P<0.001. After 72 hour follow-up of the admitted patients: 102(55.74%) were discharged, 61(33.33%) remained on ward, 3(1.64%) remained in ICU, 17(3.39%) died. The area under the ROC curve of lactate was 0.752 showing a good diagnostic performance for injury severity. At univariate analysis, lactate ≥ 2.0mmol/l had incidence risk ratio(IRR) of 1.10 (P<0.001) for emergency department disposition, 4.33 (P=0.06) for 72 hour non-discharge, 1.19 (P<0.001) for 72 hour mortality. Conclusions: Admission lactate ≥2.0mmol/l was useful in discriminating severe from non-severe injuries with a sensitivity of 88% but a low specificity of 37.8%. This level of lactate also appeared to predict emergency department disposition and 72 hour mortality but not 72 hour non-discharge. Recommendations: Admission venous lactate should be used to screen trauma patients for injury severity with a lactate level of 2.0mmol/l being the cut off between severe and non-severe injuries. Trauma patients with hyperlactatemia should be promptly managed in order to improve on early outcome and reduce on morbidity and mortality.