Feasibility of intra-arrest hypothermia induction: A novel nasopharyngeal approach achieves preferential brain cooling

Abstract

Aim: In patients with cardiopulmonary arrest, brain cooling may improve neurological outcome, especially if applied prior to or during early reperfusion. Thus it is important to develop feasible cooling methods for pre-hospital use. This study examines cerebral and compartmental thermokinetic properties of nasopharyngeal cooling during various blood flow states.

Methods: Ten swine (40+/-4kg) were anesthetized, intubated and monitored. Temperature was determined in the frontal lobe of the brain, in the aorta, and in the rectum. After the preparatory phase the cooling device (RhinoChill system), which produces evaporative cooling in the nasopharyngeal area, was activated for 60min. The thermokinetic response was evaluated during stable anaesthesia (NF, n=3); during untreated cardiopulmonary arrest (ZF, n=3); during CPR (LF, n=4).

Results: Effective brain cooling was achieved in all groups with a median cerebral temperature decrease of -4.7 degrees C for NF, -4.3 degrees C for ZF and -3.4 degrees C for LF after 60min. The initial brain cooling rate however was fastest in NF, followed by LF, and was slowest in ZF; the median brain temperature decrease from baseline after 15min of cooling was -2.48 degrees C for NF, -0.12 degrees C for ZF, and -0.93 degrees C for LF, respectively. A median aortic temperature change of -2.76 degrees C for NF, -0.97 for LF and +1.1 degrees C for ZF after 60min indicated preferential brain cooling in all groups.

Conclusion: While nasopharyngeal cooling in swine is effective at producing preferential cerebral hypothermia in various blood flow states, initial brain cooling is most efficient with normal circulation.

Fig. 1

Photograph of the tubing used for nasopharyngeal cooling. The perfluorochemical (PFC)-oxygen mixture is delivered from the oxygen tank and the PFC reservoir in a single tube (1) that then bifurcates into a left and right nasopharyngeal cannula (2). The perfluorochemical-oxygen spray (3) exits in dorsal and lateral direction from the distal end of the cannulas.

Fig. 2

Change in brain temperatures from baseline (mean ± SD) during untreated cardiopulmonary arrest (ZF; n = 3), CPR (LF; n = 4) and anaesthesia (NF; n = 3) over the course of 60 min of nasopharyngeal cooling. *indicates first significant decrease from baseline (α<0.01).

Fig. 3

Changes in mean cerebral, aortic and rectal temperatures during untreated cardiac arrest (a), anaesthesia only (b) and CPR (c) over the course of 60 min of nasopharyngeal cooling.