Lipolysis in burned patients is stimulated by the beta 2-receptor for catecholamines
D. N. Herndon, T. T. Nguyen, R. R. Wolfe, S. P. Maggi, G. Biolo, M. Muller and R. E. Barrow
Department of Surgery, University of Texas Medical Branch, Galveston.
OBJECTIVE: To determine if the cardiovascular effects of excessive
catecholamines could be selectively blocked in severely burned patients
without adversely affecting protein or fat kinetics. DESIGN: Prospective
cohort study. SETTING: A large tertiary care referral center in Galveston,
Tex. PATIENTS: Sixteen patients with greater than 40% body surface area
burns. INTERVENTIONS: Patients were randomly selected to receive
propranolol hydrochloride, a nonselective beta 1- and beta 2-blocker, or
metoprolol tartrate, a selective beta 1-blocker. MAIN OUTCOME MEASURES:
Heart rate; rate-pressure product; rate of appearance of urea, 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 rate, from a mean (+/- SD) of 143
+/- 15 to 115 +/- 11 and from 147 +/- 17 to 120 +/- 9 beats per minute,
respectively, during the 5-day study period. Neither 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 appearance of glycerol, from a mean
(+/- SD) of 5.54 +/- 0.62 to 3.07 +/- 0.7 mumol/kg per minute. The rate of
appearance of leucine, used as an index of total body protein catabolism,
was not significantly altered by either beta-blocker. CONCLUSIONS:
Selective beta 1-adrenergic blockade did not reduce lipolysis; however, a
beta 1- and beta 2-adrenergic blockade significantly reduced lipolysis.
Thus, the increased lipolysis, characteristic of severely burned patients,
is caused by stimulation of the beta 2-adrenergic receptors for
catecholamines.
