Abstract 133: Adverse Effects of Carbon Dioxyde Expansion for Brain Protection in a Pig Model
Background: A new technique of brain and general hypothermia has been proposed to produce localized cooling by adiabatic gas expansion in the nasopharynx. The purpose of this study was to test the possible adverse effects of maximal cooling produced by large amount of carbon dioxyde (CO2) expansion in the nasopharynx in a pig model.
Method: The study population consisted of 8 pigs 39.4 ± 3.9 kg studied under anesthesia according to WICCM protocol. Temperatures in °C were measured every minute by thermocouples: close to the injector exit in the nasopharynx, tympanic, jugular vein, esophagus and in the rectum. CO2 was expanded at the exit of the nasal injector for 10, 20 and 30mn. Pressure was delivered at saturation vapor pressure 840 psi (56 bar) n=3 or regulated at 430 psi (40 bar) n=5.
Results: The first 3 pigs became cyanotic and died at the end of the experiment as suspected by data from the ventilator. Autopsy performed on the last pig revealed subcutaneous emphysema leading to excessive lung compression.
Several local adverse side effects were also observed:
-Blister lesion 1.5 x 0.5 mm at the contact with the metallic injector tip where a temperature of -30°C was recorded for 20 mn was observed in one pig studied.
-Nasopharyngeal edema was observed after extubation in one pig studied after 10x5 min of CO2 injections.
-Slight abdominal distension which vanished spontaneously was observed in 7 pigs.
Discussion: Subcutaneous emphysema: was the result of injection of CO2 in the soft tissues after perforation of the mucosa due to the injector being blocked against the posterior wall of the nasopharynx. A non-contact placement of the injector prevented this complication in the following experiments.
Blister: was due to close contact between the frizzing injector tip (-30°C) and the mucosa. A spacer should avoid this problem.
Nasopharyngeal edema: was related to excess of cooling below 0°C during too long a period of time.
Abdominal distension: was the result of CO2 spread toward the upper GI tract.
Conclusion: This study demonstrates that carbon dioxyde which is the most effective gas for brain and body hypothermia may have major side effects. These adverse side effects can be prevented by proper modification of the injector and delivery of a lesser amount of CO2.
- © 2013 by American Heart Association, Inc.