COMBINED ADRENERGIC BLOCKADE IN EXPERIMENTAL HEMORRHAGIC HYPOTENSION

Hemorrhagic hypotension at 40 mm of mercury was induced by the reservoir technique in 48 artificially ventilated dogs. Alpha receptor blockade decreased blood loss, prolonged the tolerated period and diminished the metabolic sequels of hypotension, as compared to untreated controls. Beta-receptor blockade did not affect initial blood loss, but shortened the tolerated period and aggravated the metabolic sequels of hypotension. Combined adrenergic blockade produced a smaller decrease of tolerated blood loss than pure alpha blockade, together with maximum inhibition of its metabolic sequels. The tolerated period of hypotension did not differ from that observed with pure alpha blockade. However, in addition to blood loss into the reservoir, untreated animals lost plasma from the circulation, whereas blocked animals showed plasma refill. The difference in circulating blood volume during hypotension was therefore greater than suggested by external blood loss. A 15% difference of circulating blood volume after 5 hours of hypotension equalled base excess values of -7 and -16 mval/l, respectively, or a 100% difference. Further studies of combined adrenergic blockade in shock should be based on the combination of drugs producing the smallest decrease of tolerated blood loss together with maximum inhibition of its metabolic sequels. © 1969 Springer-Verlag.