LIPOLYSIS IN BURNED PATIENTS IS STIMULATED BY THE BETA(2)-RECEPTOR FOR CATECHOLAMINES

Objective: To determine if the cardiovascular effects of excessive cat echolamines could be selectively blocked in severely burned patients w ithout adversely affecting protein or fat kinetics. Design: Prospectiv e cohort study. Setting: A large tertiary care referral center in Galv eston, Tex. Patients: Sixteen patients with greater than 40% body surf ace area burns. Interventions: Patients were randomly selected to rece ive propranolol hydrochloride, a nonselective beta(1)- and beta(2)-blo cker, or metoprolol tartrate, a selective beta(1)-blocker. Main Outcom e Measures: Heart rate; rate-pressure product; rate of appearance of u rea, glucose, and leucine; and leucine oxidation were measured before and after selective or nonselective beta-adrenergic blockade. Results: Propranolol and metoprolol caused a significant decrease in heart rat e, from a mean (+/-SD) of 143+/-15 to 115+/-11 and from 147+/-17 to 12 0+/-9 beats per minute, respectively, during the 5-day study period. N either the rate of appearance of urea nor the rate of urea production were significantly altered by propranolol or metoprolol therapy. Only propranolol produced a significant decrease (P<.05) in the rate of app earance of glycerol, from a mean (+/-SD) of 5.54+/-0.62 to 3.07+/-0.7 mu mol/kg per minute. The rate of appearance of leucine, used as an in dex of total body protein catabolism, was not significantly altered by either beta-blocker. Conclusions: Selective beta(1)-adrenergic blocka de did not reduce lipolysis; however, a beta(1)- and beta(2)-adrenergi c blockade significantly reduced lipolysis. Thus, the increased lipoly sis, characteristic of severely burned patients, is caused by stimulat ion of the beta(2)-adrenergic receptors for catecholamines.