Effect of Therapeutic Hypothermia on Gas Exchange and Respiratory Mechanics: A Retrospective Cohort Study

Abstract

Targeted temperature management (TTM) may improve respiratory mechanics and lung inflammation in acute respiratory distress syndrome (ARDS) based on animal and limited human studies. We aimed to assess the pulmonary effects of TTM in patients with respiratory failure following cardiac arrest. Retrospective review of consecutive cardiac arrest cases occurring out of hospital or within 24 hours of hospital admission (2002-2012). Those receiving TTM (n=44) were compared with those who did not (n=42), but required mechanical ventilation (MV) for at least 4 days following the arrest. There were no between-group differences in age, gender, body mass index, APACHE II, or fluid balance during the study period. The TTM group had lower ejection fraction, Glasgow Coma Score, and more frequent use of paralytics. Matched data analyses (change at day 4 compared with baseline of the individual subject) showed favorable, but not statistically significant trends in respiratory mechanics endpoints (airway pressure, compliance, tidal volume, and PaO2/FiO2) in the TTM group. The PaCO2 decreased significantly more in the TTM group, as compared with controls (-12 vs. -5 mmHg, p=0.02). For clinical outcomes, the TTM group consistently, although not significantly, did better in survival (59% vs. 43%) and hospital length of stay (12 vs. 15 days). The MV duration and Cerebral Performance Category score on discharge were significantly lower in the TTM group (7.3 vs. 10.7 days, p=0.04 and 3.2 vs. 4, p=0.01). This small retrospective cohort suggests that the effect of TTM ranges from equivalent to favorable, compared with controls, for the specific respiratory and clinical outcomes in patients with respiratory failure following cardiac arrest.

Molecular and biophysical mechanisms behind the enhancement of lung surfactant function during controlled therapeutic hypothermia

“…Therapeutic hypothermia (TH) is used as an effective method to limit brain injury after certain types of cardiac arrest and perinatal asphyxia, by reducing patient body temperature from 37 to 33.5 °C 1 , 2 . Early studies also suggest some possible benefits in cooled patients suffering of acute respiratory distress syndrome (ARDS) 3 – 6 . ARDS accounts for 10% of all cases in intensive care units worldwide.…”

Pediatric Cardiac Arrest

“…Current data suggest that it is appropriate to target normocapnia or a PaCO2 specific for the patient's condition while minimizing hypercapnia and hypocapnia [24,105]. While providing strategies to optimize oxygenation and ventilation, we must be mindful that therapeutic hypothermia can alter the arterial oxygen saturation and affect carbon dioxide production which will be reflected in the minute ventilation [106].…”

Haemodynamic and ventilator management in patients following cardiac arrest

“…This may be very important in patients treated with TTM, which affects not only respiratory mechanics but also gas exchange (i.e. decreased CO 2 and increased O 2 during cooling procedures at unchanged minute ventilation) [30,31]. …”