ARE WE USING AN EXCESSIVE DOSE OF NEUROMUSCULAR BLOCKING
DRUGS: FOOD FOR THOUGHT? Profiles in Anaesthetic practice: Overdosing with neuromuscular blocking drugs: A universal Foible - Jennifer MHunter. In Clinical Anaesthesiology 4th ed, 2006; Editors- Morgan Jr GE, Mikhail MS, Murray MJ.

The art of using neuromuscular blocking drugs (NMBD) for anaesthesia entails giving just a sufficient amount of the drug and its antagonist at an appropriate time. The practice of ‘bucket anaesthesia’, ie rapidly and carelessly using an excessive amount of drug without any consideration of the duration of its clinical effect could be disastrous for the patient. Using larger doses of nondepolarizing muscle relaxants (for eg rocuronium 1.2mg/kg and atracurium 0.6-0.9mg/kg) no doubt increases the onset of the block by a few seconds, but do we not need to heed the fact that it is also associated with a significantly longer clinical duration of action, which is often unnecessary? The situation is further made worse by a tendency to give generous increments every 30 minutes.
It has also been demonstrated that anaesthesiologists use an inappropriately large dose of scoline. Clinical recovery is seen to be faster (6.6 min) with scoline 0.4 mg/kg as compared to that with 1 mg/kg (9.3 min). More important is the fact, that if a failed intubation occurs, a smaller dose of scoline would lead to a faster recovery of respiration before hypoxic damage ensues!
It is advisable to give neostigmine 2.5mg when T1/ T0 ratio is 0.5, as then it takes only 1.2 mins for T1/ T0 and 2.1 mins for the TOF (train of four) ratio to reach 0.7. If neostigmine is administered when the first twitch of the TOF response has recovered to only 10%, it takes 9.2 min for the TOF ratio to reach 0.7 and it is indeed debatable as to how many anaesthesiologists actually wait for 10 mins after giving reversal and before extubating their patients!
Age of the patient, sex (clearance is lower in women), alcoholism and smoking (faster metabolism) should all be taken into consideration when deciding the dose of NMBDS. Using the correct dosage of drugs which are independent of organ function, along with neuromuscular monitoring and administration of the anticholineesterase only when the 2nd twitch of the TOF response is detected, will ensure that residual block does not occur. The art of providing ideal anaesthesia is to tailor the dose of the drug to an individual patient.
Compiled by:
Dr. Vandana Talwar
E mail: vandtal@yahoo.com