Background: Lactate and lactate dehydrogenase (LDH) have been found to be elevated in cardiopulmonary failure, sepsis, shock, and hepatic injury. Severe dengue hemorrhagic fever (DHF) patients also develop shock and experience a certain
degree of hepatic injury, implicating that serum lactate and LDH may be elevated in Dengue shock syndrome (DSS).
Objective: To determine serum lactate and LDH levels in dengue patients to see whether they can be used as predictors of severe dengue cases.
Material and Method: A cross sectional study was conducted on suspected dengue patients admitted to the dengue ward,
Queen Sirikit National Institute of Child Health (QSNICH), between May 2011and February 2012. Laboratory tests were
used to confirm dengue cases in the enrolled patients. Blood for serum lactate was drawn in patients every day after enrollment. Blood for LDH and liver function test (LFT) were drawn 3 times: enrollment day, day of leakage, and discharge day. Lactate and LDH levels are compared among dengue and non-dengue patients. Dengue fever (DF), DHF and DSS patients were classified according to the WHO 1997 dengue classification.
Results: 253 patients were enrolled, comprising of 120 DF, 75 DH, 30 DSS, and 28 non-dengue patients. The majority of
dengue patients had liver impairment, demonstrated by elevated aspartate aminotransferase (AST) (94.9%) and alanine
aminotransferase (ALT) levels (68.6%) while non-dengue patients have minimal elevation. Serum lactate levels were not
elevated in the early stages in dengue patients, but were elevated in non-dengue patients. The mean serum lactate levels in DSS patients increased towards the end of febrile phase and reached maximum values on Day 0 (2.2 U/L). On the other hand, serum lactate levels were found to be decreasing in the non-dengue group. The mean serum lactate levels on Day 0 was found to be different in DSS patients (2.26 U/L) compared to DF 1.63 U/L), DHF (1.79 U/L) and non-dengue patients (1.68 U/L)
(p<0.05). Mean serum LDH levels were elevated in the early stages of the disease in all groups of patients, but with different
levels. Mean serum LDH levels was 709.2 in DF, 1,873 in DHF, 654.5 in DSS, and 434 IU in non-dengue patients. The mean
LDH levels in dengue patients were >500 IU, while it was <500 IU in non-dengue patients. The increasing mean levels of LDH towards the end of febrile phase were only seen in DHF and DSS patients, but not in DF and non-dengue patients. The mean levels of LDH on Day 0 in DHF, DSS, DF and non-dengue patients are 1,060.7, 1,180.7, 787.2, and 423.8 IU, respectively.
Conclusion: Serum lactate and LDH was found to be elevated in DHF and/or DSS patients. Lactate may be used as a predictor of DSS if the level is >2 U/L on Day 0. LDH can be used to differentiate patients with or without dengue in the early febrile phase, if the level is >500 IU. If the level of LDH is increased to approximately 1,000 IU on Day 0, it may be a predictor of severe dengue infection or DHF and DSS with plasma leakage.

Keywords: Lactate, Lactate dehydrogenase, Dengue, DF, DHF, DSS, Predictors