Current challenges to neuromuscular block management

There is variability in the duration of action of non-depolarising neuromuscular blocking agents4

Illustration of current NMB dynamics

Residual neuromuscular blockade can be detected in up to 40% of patients for up to two hours after the administration of the neuromuscular blocking agent, according to AAGBI Guidelines4


Incomplete reversal leads to complications

TOF ratio
  • In a case-control study of patients who received a general anaesthetic, 90.5% of patients with serious respiratory problems in the PACU had residual block (P<0.0001)*1
  • In a prospective study nearly half (36 of 76; 47%) of unplanned ICU admissions from the OR were a direct result of respiratory problems**2
  • In an observational study of 246 patients arriving in the PACU after receiving NMB, residual block caused a 33% increase in PACU length of stay (P=0.026)***3

Study Designs

*Case-control study designed to determine the incidence of critical respiratory events (CREs) in the PACU after general anaesthesia and to examine the association between CREs and residual block. All cases during the 1-year study period were identified and then matched with selected control patients for comparison during the same period. PACU nurses identified patients with evidence of a predefined CRE during the first 15 minutes of PACU admission. TOF ratios were immediately quantified in these patients using acceleromyography. TOF data were also collected in the control group, which consisted of patients also undergoing general anaesthesia during the same period who were matched with the cases by age, sex, and surgical procedure. A total of 7,459 patients received a general anaesthetic during the study period, of which 61 experienced a CRE; only 42 of the cases were matched with controls and included in the analysis.1

**Prospective study of ICU admissions from the OR conducted at a teaching hospital during a 6-month period to evaluate the types of problems associated with these admissions. To identify risk factors for ICU admission, patients were categorised into 2 groups: planned or unplanned ICU admission. A total of 204 postoperative admissions were studied: 128 planned and 76 unplanned. In the unplanned group, the reason for ICU admission was divided into 3 major categories: neurological, cardiac, or respiratory.2

***Observational study of 246 patients arriving in the PACU after receiving vecuronium or cisatracurium as part of a surgical procedure. The primary objective was to determine if residual NMB is associated with longer PACU length of stay. Neuromuscular transmission was assessed, at admission to the PACU, by acceleromyography (stimulation current: 30 mA). The potential consequences of PORC-induced increases in PACU length of stay on PACU throughput were estimated by application of a validated queuing model taking into account the rate of PACU admissions and mean length of stay in the joint system of the PACU plus patients recovering in operation theatre waiting for PACU beds.3
Residual neuromuscular block was defined as a TOF ratio of <0.93



  1. Murphy GS, Szokol JW, Marymont JH, et al. Residual neuromuscular bloackade and critical respiratory event in the postanesthesia care unit. Anesth Analg. 2008; 107(1):130-137
  2. Bhat SA, Shinde VS, Chaudhari LS. Audit of intensive care unit admissions from the operating room. Indian J Anaesth. 2006; 50(3):193-200
  3. Butterly A, Bittner EA, George E, et al. Postoperative residual curarization from intermediate-acting neuromuscular blocking agents delays recovery room discharge. Br J Anaesth. 2010; 105 (3): 304-309.
  4. Association of Anaesthetists of Great Britain and Ireland. Recommendations for standards of monitoring during anaesthesia and recovery 2015. Anaesthesia 2016; 71: 85-93.
  5. Brull, S & Kopman, A. Current Status of Neuromuscular Reversal and Monitoring: Challenges and Opportunities. Anesthesiology 2017; 126:173–90
  6. Murphy GS, Szokol JW, Franklin M, et al. Postanesthesia care unit recovery times and neuromuscular blocking drugs: a prospective study of orthopedic surgical patients randomized to receive pancuronium or rocuronium. Anesth Analg. 2004; 98:193-200
  7. Murphy GS, Szokol JW, Marymont JH, et al. Intraoperative acceleromyographic monitoring reduces the risk of residual neuromuscular blockade and adverse respiratory events in the postanesthesia care unit. Anesthesiology. 2008; 109(3): 389-398
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  10. Eikermann M, Vogt FM, Herbstreit, et al. The predisposition to inspiratory upper airway collapse during partial neuromuscular blockade. Am J Respir Crit Care Med. 2007; 175(1): 9-15
  11. Murphy GS, Brull SJ. Residual neuromuscular block: lessons unlearned. Part 1: definitions, incidence and adverse physiologic effects of residual neuromuscular block. Anesth Analg. 2010; 111(1):120-128
  12. Kopman AF, Yee PS, Neuman GG. Relationship of the train-of-four fade ratio to clinical signs and symptoms of residual paralysis in awake volunteers. Anesthesiology. 1997; 86(4):765-771
  13. Berg H, Viby-Mogenson JS, Roed J, et al. Residual neuromuscular block is a risk factor for postoperative pulmonary complications: a prospective, randomised, and blinded study of postoperative pulmonary complications after atracurium, vecuronium and pancuronium. Acta Anaesthesiol Scand. 1997; 41(9):1095-1103
  14. Eriksson LI, Sato M, Severinghaus JW. Effect of a vecuronium-induced partial neuromuscular block on hypoxic ventilatory response. Anesthesiology. 1993; 78(4):693-699
  15. Eriksson LI. Reduced hypoxic chemosensitivity in partially paralysed man. A new property of muscle relaxants? Acta Anaesthesiol Scand. 1996; 40(5):520-523