Incidence of infectious complications in patients treated with mild therapeutic hypothermia according to standardized diagnostic criteria

Purpose: Mild therapeutic hypothermia (MTH) in patients recovered from cardiac arrest (CA) has been associated with an increased frequency of infectious complications. The diagnosis of infection represents a challenge in this setting, mainly due to the early controlled body temperature and systemic inflammatory response syndrome. The aim of this study was to define the rate of infectious complications in a cohort of patients treated with MTH, using a standardized definition of infection.

Methods: Observational retrospective study analyzing all consecutive patients admitted to the acute cardiac care unit of a tertiary university hospital after in-hospital (IHCA) and out-of-hospital cardiac arrest (OHCA) treated with MTH from January 2007 to December 2012. To establish the diagnosis of infectious disease the International Sepsis Forum Consensus Conference criteria were applied. Pneumonia was defined, in presence of clinical suspicion, as confirmed (radiologic infiltrate and recovery of a probable etiologic agent), probable (radiologic infiltrate in absence of a pathogen) or possible (inconclusive radiologic findings with microbiological evidence). Bloodstream infection (BSI), catheter-related infection (CRI) and urinary tract infection (UTI) were diagnosed in patients with compatible clinical findings and positive cultures of non-contaminating agents. Data were collected from the first 7 days of hospitalization.

Results: A total of 194 patients were analyzed, 16 were excluded after documented infection prior to CA or missing data. There was a suspicion of infection in 130 (73%) patients, but there were only 84 confirmed diagnosis in 76 (42.7%) patients: pneumonia confirmed 34.2%, pneumonia probable in 26.3% and pneumonia possible in 30.3%; UTI 11.8%; BSI 5.3% and CRS 2.6%. Neither the target temperature (34°-32°C), nor the duration of MTH (1643±396 vs 1582±457 minutes; infected or not respectively, NS) influenced the prevalence of infections. IHCA and OHCA had comparable rates of infection (31.8% and 44.2%, NS). Fever after rewarming (54.5%) was not associated to increased infection rate. In-hospital mortality did not differ between infected and non-infected patients (50% vs 52%, NS).

Conclusions: When standardized criteria for the diagnosis of infectious disease are applied to the patients recovered of CA, rates seem to be lower than in previous studies and probably similar to other mechanical ventilated patients. Pneumonia is the most frequent infection in these population.