['Hypothermia occurs in as many as 7% of elective colorectal operations and is an underestimated risk factor for complications and death. Rewarming of hypothermic patients alone is not sufficient to prevent such adverse events. We investigated the outcomes of patients who became hypothermic (<35°C) after elective operations and compared them with closely matched, nonhypothermic operative patients to better define the impact of hypothermia on surgical outcomes, as well as to identify independent risk factors for hypothermia.', 'We queried the University HealthSystem Consortium (UHC) database for elective operative patients who became unintentionally hypothermic from October 2008 to March 2012, and identified 707 patients. Exclusion criteria were deliberate hypothermia, age <18 years, or death on day of admission. Separately, to validate the accuracy of hypothermia coding, we reviewed the hospital charts of all University of Louisville Hospital patients with hypothermia whose data were submitted to UHC.', 'All patients from UHC with a code for hypothermia were indeed unintentionally hypothermic. Hypothermic patients undergoing elective operations experienced a 4-fold increase in mortality (17.0% vs 4.0%; P < .001) and a doubled complication rate (26.3% vs 13.9%; P < .001), in which sepsis and stroke increased the most. Several independent risk factors for hypothermia were amenable to preoperative improvement: anemia, chronic renal impairment, and unintended weight loss. Severity of illness on admission, age >65 years, male sex, and neurologic disorders also were risk factors.'] Is unintentional perioperative hypothermia associated with severe complications and high mortality in elective operations?