Post surgery lactate levels in HIV negative and HIV positive on HAART Orthopaedic patients after tourniquet use, at four hospitals in Lusaka, Zambia

Abstract

Tourniquets are extensively used in Orthopaedic surgery to achieve a bloodless field at the surgical site resulting in elevated lactate levels. Use of antiretroviral drugs is also associated with elevation of lactate levels. Hyperlactatemia is associated with increased morbidity and mortality. Assessment of whether concurrent use of a tourniquet in Orthopaedic surgery in HIV positive patients on antiretroviral drugs has a dual additive effect on serum lactate levels is therefore important. However, the current literature on this subject is limited. The principal objective of the study was to explore the effect of tourniquet use on lactate levels in HIV positive patients on HAART undergoing extremity surgery, and how it compares to those who are not negative. This was a prospective cohort study undertaken from 26 November 2015 to 26 November 2016, with a sample size of 183 participants of patients who presented for orthopaedic surgery at University Teaching Hospital, St. John Paul II Orthopaedic, Beit Cure and Levy Mwanawasa Teaching hospitals, with ages ranging between 18 - 67years. Consecutive series of biographic details of all eligible patients were taken and pre-operative baseline investigations done. Four lactate samples - one pre-tourniquet inflation, and three serial post tourniquet deflation venous blood lactate - were taken from fingertip or toe-tip of contralateral limb at 2min, 5min and 15min intervals and results obtained using a Digital Lactate Plus Analyzer. One hundred and sixty (160) participants were recruited, with 124 being HIV negative (78 percent) and 36 being HIV positive on HAART (22 percent). There were significant statistical differences in the lactate levels of the patients before and after tourniquet use. Paired samples t-tests were conducted at a significant level of 0.05. Baseline lactate levels were higher in HIV positive patients on HAART than HIV negative patients. Post tourniquet deflation lactate levels were also elevated in both groups. HIV positive patients on HAART had consistently higher lactate levels at 2 min, 5 min and 15 min periods than HIV negative participants. The results from an independent samples t - test indicated that at 2 minutes, HIV positive on HAART participants (M = 4.328, SD = 0.8397, N = 36) had much higher post tourniquet deflation lactate levels than HIV negative participants (M = 2.084, SD = 0.8240, N= 124), t (36) = -7.099, p<0.001, two-tailed. At 5 minutes the results from the independent samples t-test revealed that HIV positive on HAART participants (M = 3.423, SD = 0.6548, N = 36) had much higher post tourniquet deflation lactate levels than HIV negative participants (M = 1.655, SD = 0.6468, N =124), t (36) = -7.146, p <0.001, two-tailed. Similarly, the results from an independent samples t-test indicated at 15 minutes revealed that HIV positive on HAART participants (M = 2.594, SD = 0.8750, N = 36) had much higher post tourniquet deflation lactate levels than HIV negative participants (M = 1.294, SD = 0.5401, N =124), t(36) = -4.215, p<0.002, two-tailed. However, these results were only significant at 2 minutes (t=-3.279; df=17; p=0.004) and 5 minutes (t=0.0140; df=16; p=0.052) but not significant at 15 minutes (t=1.5367; df=15; p=0.780), t=1.999[14], p=0.065) 5 min (t=1.116[13], p=0.285), and at 15 min (t=1.137[12], p=0.278). No adverse events were recorded during the study. Baseline lactate levels were higher in HIV positive on HAART. Tourniquet use induced lactate elevation post tourniquet deflation in all – both HIV negative and HIV positive on HAART patients. vi The hyperlactatemia induced is higher in HIV positive patients on HAART as compared to HIV negative patients both pre-operatively and after tourniquet use in surgery. However, there is no increased risk of use of a tourniquet in orthopaedic surgery in HIV positive patients on HAART as the elevation of lactate during surgery is short lived, with lactate values returning to pre-tourniquet inflation levels. Keywords: Tourniquet, esmarch, Inclusion and Exclusion criteria, HAART, Hyperlactateamia, Lactic acidosis, P+S, Ischemic monomelic neuropathy, Arthrodesis, NRTI's, Hypoxia / Ischemia, Lactate Inflation / deflation.