The Changing Pattern of Neuromuscular Blockade Caused by Succinylcholine in Man

The parameters involved in the change of neuromuscular block caused by succinylcholine were studied in man. In 28 patients during operation, stimulation of the ulnar nerve and recording from the adductor pollicis was accomplished, with muscle contractions recorded via a force displacement transducer. Phase II block developed in 20 patients. Time and dose relationships were studied. Post-rest facilitation and change in mode of onset of the block were newly described symptoms indicative of phase II. Edrophonium reversed phase II blockade. Time of reversal of the block to the first twitch remained unchanged from phase I to phase II, but time to full recovery of twitch and tetanus was prolonged in phase II. Tachyphylaxis occurred independently of phase of the block. Correlation with clinical muscle paralysis was poor during the administration of succinylcholine but good at the time of reversal of the block.