In their letter, Drs. Lu and Yu posed two questions. The first one concerns the number of attempts at tracheal intubation in our patients. 1The second question relates to the need for high doses of succinylcholine when teaching residents. All patients in our study 1were successfully intubated on the first attempt. This study demonstrated that, for routine tracheal intubation, there is no need to administer more than 0.6 mg/kg succinylcholine. I believe that, in certain circumstances, as addressed in our article, there might be a need to administer greater than 0.6 mg/kg succinylcholine. Provided that the patient’s airway anatomy is normal and it is possible to ventilate the lungs easily (and to maintain anesthesia), there should be no problem with higher doses of succinylcholine in the scenario described by Drs. Lu and Yu. However, when unanticipated difficult tracheal intubation is encountered and accompanied with an inability to ventilate the patient’s lungs, the duration of apnea associated with high doses of succinylcholine could be disastrous. Inadequate ventilation and unanticipated difficult tracheal intubation represented, respectively, 38% and 17% of the 1,541 claims in the American Society of Anesthesiologists Closed Claims database. 2 

I disagree with Dr. Tabboush’s contention that patients with abnormal airway anatomy should be given higher doses of succinylcholine. Similarly, morbid obesity is frequently associated with factors that could impose difficulties for mask ventilation, rigid laryngoscopy, and/or intubation (for review, see Adams and Murphy 3). It was never suggested or implied in our article that succinylcholine (even in small doses) should be used in patients with anticipated difficult airways. If a difficult airway is anticipated, I believe that the most appropriate and safe course of action is to proceed with an awake fiberoptic intubation. Therefore, it seems that Drs. Messent and Lim must have also misinterpreted our study. I also cannot agree with their comments about the study being either “theoretical” or “dangerous.” Similarly, it has never been suggested that parturients undergoing cesarean delivery should be given less than 1.0 mg/kg succinylcholine. It is clearly stated in our article, “The dose of succinylcholine must be individualized depending on the clinical situation,” and “in a patient with increased intracranial pressure or in a patient with a full stomach, decreasing the dose of succinylcholine to less than 1.0 mg/kg might increase morbidity.” Parturients undergoing cesarean delivery are included in the latter category.

Increasing the dose of succinylcholine to greater than 1.0 mg/kg, as suggested by Drs. Messent and Lim, will never guarantee “the best intubation conditions” in all of their patients. The effect of increasing succinylcholine doses and the factors contributing to intubating conditions are discussed in detail in our article.

I thank Dr. Kron for his kind comments. However, I believe that slow administration of succinylcholine has never been shown to be effective in preventing fasciculations or myalgia.

Naguib M, Samarkandi A, Riad W, Alharby SW: Optimal dose of succinylcholine revisited. Anesthesiology 2003; 99:1045–9
Caplan RA, Posner KL, Ward RJ, Cheney FW: Adverse respiratory events in anesthesia: A closed claims analysis. Anesthesiology 1990; 72:828–33
Adams JP, Murphy PG: Obesity in anaesthesia and intensive care. Br J Anaesth 2000; 85:91–108