SPLENIC EFFECTS ON HEMODYNAMICS INDUCED BY HYPOTHERMIA AND REWARMING IN MINIATURE SWINE

Central arterial hemodynamic changes were assessed during cooling, hyp othermia, and rewarming in splenectomized (SPX, n = 4) and unsplenecto mized (SP, n = 4) 8-10 month old male Yucatan miniature swine (34.0 +/ - 1.4 kg). Under isoflurane anesthesia, and using circulating-water bl ankets, pigs were cooled to and then maintained for 2 h at a rectal te mperature (Tro) of 27 +/- 1 degrees C; hypothermia was followed by rew arming to normothermia (37 +/- 1 degrees C). There were significantly (p less than or equal to 0.05) greater changes in central arterial hem atocrit and hemoglobin (Delta HCT and Delta HGB) from respective preco oling baseline levels in the SP group during hypothermia and early rew arming (SP: Delta HCTmax = 9-10%RBC, and Delta HGBmax = 3.0-3.5 g/dl v s. SPX: Delta HCTmax = 3-4%RBC, and Delta HGBmax = 1.5-1.8 g/dl). By t he end of rewarming, splenic resequestration and extravascular fluid s hifts resulted in these values returning to baseline. In addition, car diovascular instability was seen in the spy group compared to the SP a nimals as evidenced by significant tachycardia and hypotension during rewarming. We have concluded from these studies that hypothermia cause s significant hemoconcentration, and that splenic contraction is the m ajor cause of this hemoconcentration during hypothermia and initial re warming in miniature swine. A splenectomized design should be consider ed for swine studies that purport to pattern human pathophysiology, es pecially for modelling rewarming shock.