Introduction: Hyperlactatemia and lactic acidosis are commonly encountered during and afterrncardiac surgery. Perioperative lactate production increases in the myocardium, skeletal muscle,rnlungs and in the splanchnic circulation during cardiopulmonary bypass. Hyperlactatemia isrnhighly suggestive of tissue ischemia and is associated with a prolonged intensive care unit stay, arnprolonged requirement for respiratory and cardiovascular support and increased postoperativernmortality.rnObjective: The objective of the study was to assess effect of lactate on patient outcomes andrnassociated factors among patients who underwent cardiopulmonary bypass surgery at CardiacrnCenter Ethiopia, Addis Ababa, Ethiopia from December 2020 to February 2021.rnMethod: An institution-based retrospective cross-sectional study was done among all patientsrnwho underwent cardiopulmonary bypass surgery from December to January. Data was collectedrnfrom patient chart review. The collected data was entered into Epidata version 4.2 and export tornSPSS 23 for analysis. Descriptive statistics for categorical and continuous variables was done. Arnchi-square test was done to show the presence of an association between the outcome variablernand independent variables. A variables fitted on bivariate analysis was entered into multivariablernanalysis to show the strength of association and statically significant variable.rnResult: The prevalence of hyperlactatemia in this study among patients who underwent cardiacrnsurgery procedures at Cardiac Center Ethiopia was 37.5 %. Rise in lactate level prolongs ICUrnstay, Prolongs intubation duration and increase need of Inotropes support. Lactate level wasrnmeasured on immediate postoperative day within 10 hours after the surgery and was defined asrnlactate level > 3â€‰mmol/L in the first hour after surgery. Age > 50 years [AOR: 6.8 (95% CI 1.725),rnrnP=