Effects of membrane stabilization on the safety of hypothermic arrest after aortic cross-clamping.

Twenty dogs underwent 1 hour of topical hypothermic arrest; five were untreated, five received methyl prednisolone (30 mg/kg), five received 0.2% procaine, and five received both drugs. Arrest was almost immediate (less than 2 min) with procaine, but was delayed 14 +/- 3 minutes in the other groups. Steroid-treated dogs had the highest post-ischemic left ventricular (LV) blood flows (110 +/- 22 cc/100 g/min) (P less than 0.05). Membrane-stabilizing drugs did not prevent myocardial edema; LV water rose 2% (P less than 0.01) in all groups. Post-ischemic LV compliance was depressed most (55%) in the untreated group, and less after procaine (30%) (P less than 0.05). Postischemic LV performance was depressed 44% (P less than 0.01) in the untreated dogs, and returned to near normal levels with steroid (89% recovery), procaine (97% recovery), and both drugs (95% recovery). We conclude that steroids and/or procaine protect against postischemic myocardial depression but do not prevent myocardial edema. Combining steroids and procaine provide no apparent added benefit, but procaine has the technical advantage of almost immediate cardioplegia.