The definition of “deep” neuromuscular blockade is somewhat variable; some define it as zero twitch in train of four monitoring, while others use it to designate 1-2 twitches. It is often discussed in comparison to “moderate” neuromuscular blockade, which is even more inconsistently defined; some characterize it simply as the administration of neuromuscular blockers without consistent monitoring goals, re-administering as needed when the patient shows signs of spontaneous breathing or the surgeon requests deeper paralysis.
Regardless of the exact definition, the relative difference in paralysis achieved by the two approaches has been shown in the literature to improve surgical conditions (usually as reported by blinded surgeons), particularly in procedures where surgical workspace is limited such as laparoscopic procedures. There is of course the caveat that the effect is not observed across all types of surgery, and not unanimously reflected in all studies.
A group of anesthesiologists from the Netherlands recently presented a novel perspective on the subject at Anesthesiology 2017, and subsequently published the results in their paper. Boon et al conducted a retrospective study of retroperitoneal laparoscopic urology procedures in which the primary outcome was rates of unplanned readmission in the first 30 days after surgery. Patients either received high dose rocuronium (1mg/kg followed by a continuous infusion targeting 1-2 twitches on train of four monitoring) or low dose rocuronium (0.4mg/kg at induction, no continuous infusion, no consistent train of four monitoring). The high dose group received sugammadex for reversal, the low dose group received either sugammadex or neostigmine. The high dose group was found to have significantly lower rates of readmission postoperatively and lower overall costs.
The mechanism for this benefit of deep neuromuscular blockade is not fully elucidated. The readmissions did not involve the respiratory system, making it less likely that superior reversal by sugammadex or closer train of four monitoring in the high dose rocuronium group was responsible. Rather, the readmissions were largely due to postoperative surgical complications, including infections or anastomotic leak. The authors theorized that deep neuromuscular blockade provided improved surgical conditions, which in turn lead to superior technical performance by the surgeons and fewer subsequent surgical complications resulting in readmission.
There was no difference noted between the two groups in terms of duration of anesthesia or surgical procedure, use of vasoactive medications, patient vital signs, or bispectral index.
To suggest that intraoperative depth of neuromuscular blockade may extend to postoperative benefits is an intriguing new development in this topic, and warrants further study to elucidate the mechanism of effect.