Efficacy of Selective Brain Cooling Using a Nasopharyngeal Method in Piglets.
BACKGROUND
Mild hypothermia is an effective neuroprotective strategy for a variety of acute brain injuries. Cooling the nasopharynx may offer the capability to cool the brain selectively due to anatomic proximity of the internal carotid artery to the cavernous sinus. This study investigated the feasibility and efficiency of nasopharyngeal brain cooling by continuously blowing room temperature or cold air at different flow rates into the nostrils of normal newborn piglets.


METHODS
Experiments were conducted on thirty piglets (n = 30, weight = 2.7 ± 1.5 kg). Piglets were anesthetized with 1–2% isoflurane and were randomized to receive one of four different nasopharyngeal cooling treatments: I. Room temperature at a flow rate of 3–4 L min(−1) (n = 6); II. −1 ± 2 °C at a flow rate of 3–4 L min(−1) (n = 6); III. Room temperature at a flow rate of 14–15 L min(−1) (n = 6); IV. −8 ± 2 °C at a flow rate of 14–15 L min(−1) (n = 6). To control for the normal thermal regulatory response of piglets without nasopharyngeal cooling, a control group of piglets (n = 6) had their brain temperature monitored without nasopharyngeal cooling. The duration of treatment was 60 min, with additional 30 min of observation.


RESULTS
In group I, median cooling rate was 1.7 ± 0.9 °C/h by setting the flow rate of room temperature air to 3–4 L min(−1). Results of comparing different temperatures and flow rates in the nasopharyngeal cooling approach reveal that the brain temperature could be reduced rapidly at a rate of 5.5 ± 1.1 °C/h by blowing −8 ± 2 °C air at a flow rate of 14–15 L min(−1).


CONCLUSIONS
Nasopharyngeal cooling via cooled insufflated air can lower the brain temperature, with higher flows and lower temperatures of insufflated air being more effective.
Mohammad Fazel
MF
Bakhsheshi
Errol E
EE
Stewart
Joo Ho
JH
Tai
Laura
L
Morrison
Lynn
L
Keenliside
Ting-Yim
TY
Lee
D000818:Animals; D000831:Animals, Newborn; D001831:Body Temperature / Q000502:physiology*; D001921:Brain; D003080:Cold Temperature; D005240:Feasibility Studies; D005260:Female; D007036:Hypothermia, Induced / Q000379:methods*; D008297:Male; D009305:Nasopharynx; D011897:Random Allocation; D013552:Swine