I have been running out of good topics to write about late. Finally it occurred to me that I have never talked about the necessity of waiting for Sux to wear off. Again, this is another dogma that I feel it is time to discuss and address. Do we really have to wait for the twitches to come back after giving succinylcholine before you can give NMB? The textbook answer would be yes. However, with a good understand of pharmacology, you would know why it would be OK to give longer acting muscle relaxant before the return of twitches. The practice of waiting for the return of twitch after succinylcholine is unwarranted. The reason to wait for the twitches to come back is that it may potentially make it worse by giving NDMR to a pseudochlinesterase deficient patient.
However, is this concern valid? Let’s take a closer look. First of all, nondepolarizing muscle relaxants, unlike succinylcholine, undergo metabolism by the liver/kidney. Hence, the duration of action is terminated by redistribution away from the neuromuscular junction. Thus, in a patient with pseudocholinesterase deficiency, succinylcholine will outlast any moderate dose of nondepolarizing relaxant. Therefore, there is really no need to wait for the return of twitches after giving succinycholine. You can give moderate dose of NDMR right after the succinylcholine if needed for cases that requires muscle relaxant. So you don’t have to worry about patient coughing or moving after intubation while you are busy doing other things such as putting on upper body bear hugger and positioning patient.
The typical dose 3-4 mg vecuronium or 30-40mg rocuronium for a laparoscopic procedure such as cholecystectomy or appendectomy. The dosage depends the procedure and surgeon so you know before the end of the procedure, the vec/roc would wear off and twitches will be back. Thus, you can easily rule out the rare patient with pseudochonlineterase deficiency as in the pseudocholinerase deficient patient, the succinylcholine will last much longer than the moderate dose of vecuronium or rocuronium. However, if no twitches are back after you give moderate dose of roc/vec, Sugammadax can be given to see if return of twitches will be back. If after reversal is given and no twitches are back, a pseudocholinesterase deficiency should be entertained. In this case, the patient will require ventilation in the PACU until the succinylcholine wears off.
Please send me your comments and let me know what you think?