NMB 101: 13 Lucky Reminders
for use of NeuroMuscular Blocking Agents

Rob Morrison MD February 2012


1) Laryngeal mask anesthesia has changed expectations in the OR and PACU. Endotracheal anesthetics can't be rushed. LMA anesthetics require no paralysis and permit fast "extubations" => PACU transfers => hand-offs. Endotracheal anesthetics need time for pre and post extubation assessments.


2) EXTUBATION IS A PROCEDURE. It deserves a checklist with "hard stops" and a procedure note on the anesthesia record. What's more, not all patients can or should be extubated before the PACU phase.

 

3) We often intubate with larger doses of Vecuronium, Rocuronium and Cisatracurium than are necessary. Learn the ED95s (Effective Dose for 95% depression of T1 twitch height). For short, elective cases lower NMBD doses plus propofol plus inhalation agent results in excellent Intubating conditions in 4-5 minutes.

 

NMBD ED95 ( 15% less with inhalational agents) Intubating Dose Top-Up Dose
Vecuronium 0.05 mg/kg (50 mcg/k)
Example: 80kg = 4.0 mg
0.1-0.2 mcg/kg Up to 0.02 mg/kg
Rocuronium 0.30 mg/kg 0.6-1.0 mg/kg 0.10 mg/kg
Cisatracurium 0.05mg/kg 0.15-0.2 mg/kg 0.02 mg/kg

From table 29-6, Miller's "Anesthesia" (2010)


4) We often "top-up" with more NMBD than is necessary. It's safest to maintain ~2 twitches and use small top up doses (see table above). Avoid top-ups in the last ~45 min before giving Neostigmine. Instead of top-up NMBDs use incremental propofol, opiates, IV lidocaine, and, when necessary, tell the surgeon that you can't safely give any more paralyzing agents.


5) Neostigmine is an ANTAGONIST not a "reversal." The only true reversal out there is Suggamadex and the FDA won't let us have it. (At ~$80 a pop it's even too costly for the Europeans.)


6) "Blind Paralysis" is common. Traditional methods of assessing NMB recovery (vigorous bucking, full tidal volumes, head lift, hand grip, NIF, visually observed TOF, 5 sec 50hz tetanus, etc) result in unrecognized residual paralysis. Since the introduction of quantitative nerve stims, multiple studies have documented very high rates of residual paralysis in the PACU. Rates as high as 40% if neostigmine was given, and 60% if neostigmine was omitted.

 

7) Residual paralysis results in unwanted critical respiratory events including reintubations in PACU. This is fact, not speculation. (Murphy et al, Anesth Analg 2008;107:130-137) Patients at highest risk: Renal dz, Hepatic dz, obesity, diabetes, circulatory deficiency, age>70, pulmonary disease, hypothermia.


8) Neostigmine & glycopyrrolate does NOT increase the risk of nausea and vomiting. (Cheng, Sessler, Apfel, Anesth Analg.(2005); 101: 1349-1355. Joshi et al, Anesth Analg (1999); 89:628-31, Hovorka et al, Anesth Analg (1997); 85:1359-61) Even if it did, safety demands minimizing the risk of residual paralysis.


9) Neostigmine is an effective antagonist only when given with TOFs of 3 or 4. If given to reverse vecuronium with a TOF of 1-2 there will be ~22-30 minutes of continued weakness. This is the same as if you waited 10-15 min for a 3rd twitch to appear before giving neostigmine. (see page 889, Miller)

TOF count "Full" recovery Effective Neostigmine dose
4 ~10 minutes 30 mcg/kg
3 ~15 minutes 50 mcg/kg
2 ~22 minutes 70 mcg/kg
1 ~30 minutes 70 mcg/kg

BTW, the duration of neostigmine action is only ~30 minutes following a 70mcg/kg dose. Another reason not to use it too early.

 

10) Using the facial nerve as a monitoring site is often necessary but recovery at this site occurs earlier (~17 min if vecuronium is used) than at the ulnar nerve. Also remember to confirm recovery at the ulnar nerve because the pharyngeal muscles needed for airway support and swallowing recover in synchrony with the thumb muscles not the facial muscles.


11) NEVER mix "steroidal" and "quinolinium" NMBDs. You will be unable to predict NMB effect or recovery.


12) ALWAYS give neostigmine even if the TOF count has been 4 for >50 min. As Ronald Miller wrote in a July, 2010 editorial (Anesth Analg; 111:3-5): "If a decision is made not to give neostigmine, then specific reasons must be recorded." For us this means ALWAYS give neostigmine and glycopyrrolate. If and when you ever use a quantitative neuromuscular tester and you can document a TOFR >0.9, then you can omit neostigmine.


13) Lastly, there still is no true substitute for succinylcholine. Use it when risks (full stomach, difficult airway) justify it. And if vecuronium is used after sux, remember to use the ED95 dose (0.05 mg/kg) NOT the intubating dose.