Effect of Acute βAdrenergic Blockade on Lactate-lnduced Panic-Reply

In Reply.—  We appreciate the work of Rainey et al in bringing to our attention the previously untranslated French manuscript of Scebat et al. While interesting, however, the findings of the French group hardly indicate that lactate works to increase heart rate or cardiac index (cardiac output divided by surface area) via a βadrenergic mechanism.First, Jose and Taylor¹ specifically found that 0.2 mg/kg of intravenous propranolol hydrochloride is needed to saturate βreceptors in dogs, not the 0.1 mg/kg given by Scebat et al. If isoproterenol causes an increase in the cardiac index after propranolol hydrochloride administration within ten to 20 minutes, by definition full βblockade was not achieved.Furthermore, there are a variety of ways to increase cardiac rate and output other than by stimulation of βreceptors. These include parasympathetic inhibition and peripheral vasodilation. The study by Scebat et al cannot answer the question of the interaction between lactate and