Abstract 10035: Oesophageal Heat Exchangers With a Diameter of 11mm or 14,7mm are Equally Effective for Conduction of Mild Therapeutic Hypothermia

Abstract

Introduction: Induction of mild therapeutic hypothermia (MTH) is recommended for adult patients after out-of-hospital-cardiac-arrest (OHCA) [1]. Conventional surface cooling methods are simple to apply, but reveal inaccuracy during maintenance of MTH and are accompanied by more adverse events [2]. Internal cooling with an endovascular cooling device (ECD) is effective and reliable during maintenance of MTH, but is difficult to apply. Since the esophagus is located adjacent to the heart, aorta and inferior cava vein fast temperature conduction from and to the blood-stream could be achieved by use of a semi-invasive esophageal heat exchanger (EHE) that can be inserted easily and safely. Hypothesis: MTH can be conducted accurately, effectively, safely and without esophageal tissue damage with a newly developed EHE in pigs. Methods: Sixteen pigs (28.8±0.6kg) were randomly assigned to an EHE of 11mm (n=8) or 14.7mm (n=8) diameter. After induction of anesthesia, EHE were blindly inserted and connected to a chiller (HICO Variotherm 555, Hirtz & Co.KG, Cologne, Germany). Via the EHE, pigs were cooled to a target temperature of 33°C, maintained at 33°C for 1 hour, then covered with a silver-blanket and rewarmed with a rate of 0,25°C/h. After 10h of rewarming esophagi including larynx and cardia were resected in their entire lengths and analyzed by means of histopathology. Pulmonary artery temperature was recorded continuously. Results: Mean cooling rates were 2.8±0.1°C/h (11mm) and 2.9±0.1°C/h (14.7mm) (p=0.41). Average deviations from target temperature during maintenance were 0.1±0°C in both groups (p=0.44). Rewarming rates were 0.17±0.03°C/h (11mm) and 0.19±0.02°C/h (14.7mm) (p=0.65). Occasional mild diffuse mononuclear acute inflammatory transepithelial infiltrates were found in the laryngeal region, but not in the esophagus. Conclusions: Use of the EHE for MTH in pigs seemed to be efficient, safe and reliable.