title: Optimal protective hypothermia in arrested mammalian hearts.
abstract: Many therapeutic hypothermia recommendations have been reported, but the information supporting them is sparse, and reveals a need for the data of target therapeutic hypothermia (TTH) from well-controlled experiments. The core temperature ≤35°C is considered as hypothermia, and 29°C is a cooling injury threshold in pig heart in vivo. Thus, an optimal protective hypothermia (OPH) should be in the range 29-35°C. This study was conducted with a pig cardiopulmonary bypass preparation to decrease the core temperature to 29-35°C range at 20 minutes before and 60 minutes during heart arrest. The left ventricular (LV) developed pressure, maximum of the first derivative of LV (dP/dtmax), cardiac power, heart rate, cardiac output, and myocardial velocity (Vmax) were recorded continuously via an LV pressure catheter and an aortic flow probe. At 20 minutes of off-pump during reperfusion after 60 minutes arrest, 17 hypothermic hearts showed that the recovery of Vmax and dP/dtmax established sigmoid curves that consisted of two plateaus: a good recovery plateau at 29-30.5°C, the function recovered to baseline level (BL) (Vmax=118.4%±3.9% of BL, LV dP/dtmax=120.7%±3.1% of BL, n=6); another poor recovery plateau at 34-35°C (Vmax=60.2%±2.8% of BL, LV dP/dtmax=28.0%±5.9% of BL, p<0.05, n=6; ), which are similar to the four normothermia arrest (37°C) hearts (Vmax=55.9%±4.8% of BL, LV dP/dtmax=24.5%±2.1% of BL, n=4). The 32-32.5°C arrest hearts showed moderate recovery (n=5). A point of inflection (around 30.5-31°C) existed at the edge of a good recovery plateau followed by a steep slope. The point presented an OPH that should be the TTH. The results are concordant with data in the mammalian hearts, suggesting that the TTH should be initiated to cool core temperature at 31°C.
authors.affiliation: 1 Division of Cardiology, Department of Pediatrics, University of Washington , Seattle, Washington.
authors.forename: Xue-Han
authors.initials: XH
authors.lastname: Ning
authors.forename: Outi M
authors.initials: OM
authors.lastname: Villet
authors.forename: Ming
authors.initials: M
authors.lastname: Ge
authors.forename: Laigam N
authors.initials: LN
authors.lastname: Sekhar
authors.forename: Marshall A
authors.initials: MA
authors.lastname: Corson
authors.forename: Tracy S
authors.initials: TS
authors.lastname: Tylee
authors.forename: Lu-Ping
authors.initials: LP
authors.lastname: Fan
authors.forename: Lin
authors.initials: L
authors.lastname: Yao
authors.forename: Chun
authors.initials: C
authors.lastname: Zhu
authors.forename: Aaron K
authors.initials: AK
authors.lastname: Olson
authors.forename: Norman E
authors.initials: NE
authors.lastname: Buroker
authors.forename: Cheng-Su
authors.initials: CS
authors.lastname: Xu
authors.forename: David L
authors.initials: DL
authors.lastname: Anderson
authors.forename: Yong-Kian
authors.initials: YK
authors.lastname: Soh
authors.forename: Elise
authors.initials: E
authors.lastname: Wang
authors.forename: Shi-Han
authors.initials: SH
authors.lastname: Chen
authors.forename: Michael A
authors.initials: MA
authors.lastname: Portman
mesh_terms: D000818:Animals; D002314:Cardioplegic Solutions / Q000494:pharmacology; D001026:Coronary Artery Bypass / Q000379:methods; D004195:Disease Models, Animal; D006323:Heart Arrest / Q000628:therapy*; D006324:Heart Arrest, Induced / Q000379:methods; D006439:Hemodynamics / Q000502:physiology; D007036:Hypothermia, Induced / Q000379:methods*; D008297:Male; D010865:Pilot Projects; D020127:Recovery of Function / Q000502:physiology; D034421:Sus scrofa; D013552:Swine
chemical_list: D002314:Cardioplegic Solutions