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Background: An unanticipated difficult airway during induction of anesthesia can be a vexing problem. In the setting of can't intubate, can't ventilate (CICV), rapid recovery of spontaneous ventilation is a reasonable goal. The urgency of restoring ventilation is a function of how quickly a patient's hemoglobin oxygen saturation decreases versus how much time is required for the effects of induction drugs to dissipate, namely the duration of unresponsiveness, ventilatory depression, and neuromuscular blockade. It has been suggested that prompt reversal of rocuronium-induced neuromuscular blockade with sugammadex will allow respiratory activity to recover before significant arterial desaturation. Using pharmacologic simulation, we compared the duration of unresponsiveness, ventilatory depression, and neuromuscular blockade in normal, obese, and morbidly obese body sizes in this life-threatening CICV scenario. We hypothesized that although neuromuscular function could be rapidly restored with sugammadex, significant arterial desaturation will occur before the recovery from unresponsiveness and/or central ventilatory depression in obese and morbidly obese body sizes., Methods: We used published models to simulate the duration of unresponsiveness and ventilatory depression using a common induction technique with predicted rates of oxygen desaturation in various size patients and explored to what degree rapid reversal of rocuronium-induced neuromuscular blockade with sugammadex might improve the return of spontaneous ventilation in CICV situations., Results: Our simulations showed that the duration of neuromuscular blockade was longer with 1.0 mg/kg succinylcholine than with 1.2 mg/kg rocuronium followed 3 minutes later by 16 mg/kg sugammadex (10.0 vs 4.5 minutes). Once rocuronium neuromuscular blockade was completely reversed with sugammadex, the duration of hemoglobin oxygen saturation >90%, loss of responsiveness, and intolerable ventilatory depression (a respiratory rate of ≤4 breaths/min) were dependent on the body habitus and duration of oxygen administration. There is a high probability of intolerable ventilatory depression that extends well beyond the time when oxygen saturation decreases <90%, especially in obese and morbidly obese patients. If ventilatory rescue is inadequate, oxygen desaturation will persist in the latter groups, despite full reversal of neuromuscular blockade. Depending on body habitus, the duration of intolerable ventilatory depression after sugammadex reversal may be as long as 15 minutes in 5% of individuals., Conclusions: The clinical management of CICV should focus primarily on restoration of airway patency, oxygenation, and ventilation consistent with the American Society of Anesthesiologist's practice guidelines for management of the difficult airway. Pharmacologic intervention cannot be relied upon to rescue patients in a CICV crisis.

Background: Rocuronium in intubation doses provides similar intubation conditions as succinylcholine, but has a longer duration of action. This study compared time to sugammadex reversal of profound rocuronium-induced neuromuscular block with time to spontaneous recovery from succinylcholine., Methods: One hundred and fifteen adult American Society of Anesthesiologists Class I-II surgical patients were randomized to this multicenter, safety-assessor-blinded, parallel group, active-controlled, Phase IIIa trial. Anesthesia was induced and maintained with propofol and an opioid. Neuromuscular transmission was blocked and tracheal intubation facilitated with 1.2 mg/kg rocuronium or 1 mg/kg succinylcholine. Sugammadex (16 mg/kg) was administered 3 min after rocuronium administration. Neuromuscular function was monitored by acceleromyography. The primary efficacy endpoint was the time from the start of relaxant administration to recovery of the first train-of-four twitch (T(1)) to 10%., Results: One hundred and ten patients received study treatment. Mean times to recovery of (T(1)) to 10% and (T(1)) to 90% were significantly faster in the rocuronium-sugammadex group (4.4 and 6.2 min, respectively), as compared with the succinylcholine group (7.1 and 10.9 min, respectively; all P < 0.001). Timed from sugammadex administration, the mean time to recovery of (T(1)) to 10%, (T(1)) to 90%, and the train-of-four (T(4)/T(1)) ratio to 0.9 was 1.2, 2.9, and 2.2 min, respectively. Reoccurrence of the block was not observed. There were no serious adverse events related to study treatments., Conclusion: Reversal of profound high-dose rocuronium-induced neuromuscular block (1.2 mg/kg) with 16 mg/kg sugammadex was significantly faster than spontaneous recovery from 1 mg/kg succinylcholine.

In this prospective, randomized, double-blind, placebo-controlled study, we attempted to define the dose of succinylcholine that provides excellent intubation conditions in patients within 60 s during simulated rapid-sequence induction of anesthesia. Anesthesia was induced in 180 patients with 2 microg/kg fentanyl and 2 mg/kg propofol. After loss of consciousness, patients were randomly allocated to receive 0.3, 0.5, 1.0, 1.5, or 2.0 mg/kg succinylcholine or saline solution (control group). Tracheal intubation was performed 60 s later. A blinded investigator performed all laryngoscopies and graded intubating conditions. Intubating conditions were excellent in 0.0%, 43.3%, 60.0%, 63.3%, 80.0%, and 86.7% of patients after 0.0, 0.3, 0.5, 1.0, 1.5, and 2.0 mg/kg succinylcholine, respectively. The incidence of excellent intubating conditions was significantly more frequent (P < 0.001) in patients receiving succinylcholine than in the controls and in patients who received 2.0 mg/kg succinylcholine (P < 0.05) than in those who received 0.3 mg/kg succinylcholine. The calculated doses of succinylcholine (and their 95% confidence intervals) that are required to achieve excellent intubating conditions in 50% and 80% of patients at 60 s are 0.39 (0.29-0.51) mg/kg and 1.6 (1.2-2.0) mg/kg, respectively. It appears that there are no advantages to using doses of succinylcholine larger than 1.5 mg/kg.

Background: The authors examined the notion that a reduction in succinylcholine dose from 1 mg/kg to approximately 0.6 mg/kg would allow a faster recovery of spontaneous ventilation and reduction in the incidence of hemoglobin desaturation during the period of apnea in simulated complete upper airway obstruction situations., Methods: This prospective, randomized, double-blind study involved 60 patients. After preoxygenation to an end-tidal oxygen concentration >90%, patients were anesthetized with 2 microg/kg fentanyl and 2 mg/kg propofol. After loss of consciousness, patients were randomly allocated to receive 0.56 or 1.0 mg/kg succinylcholine or saline (control group). Oxygen saturation was monitored continuously at the index finger. When the patient became apneic, the face mask was removed and the patient's airway was left unsupported. If the oxygen saturation decreased to 90%, the face mask was reapplied, and ventilation was assisted until the patient was awake. Time from injection of the study drug to the first visible spontaneous diaphragmatic movements was noted., Results: Oxygen saturation decreased <90% in 45%, 65%, and 85% of patients in the control, 0.56 mg/kg, and 1.0 mg/kg succinylcholine groups, respectively (P = 0.03). Corresponding times (mean +/- SD) to spontaneous of diaphragmatic movements were 2.7 +/- 1.2, 4.8 +/- 2.5, and 4.7 +/- 1.3 min, respectively. These times were longer (P < 0.001) after either dose of succinylcholine compared with controls., Conclusions: Reduction in succinylcholine dose from 1.0 mg/kg to 0.56 mg/kg decreased the incidence of hemoglobin saturation <90% from 85% to 65% but did not shorten the time to spontaneous diaphragmatic movements. A significant fraction of patients would be at risk if there were failure to intubate and ventilate whether succinylcholine is administered or not and regardless of the dose of succinylcholine administered.

Unlabelled: We designed this study to confirm anecdotal observations that neuromuscular block after a single administration of succinylcholine is characterized by fade to train-of-four (TOF) or tetanic stimulation, as well as posttetanic potentiation. This prospective, randomized, 2-center observational study involved 100 patients. Patients were allocated to 1 of 5 groups and received 0.1, 0.3, 0.5, 0.75, or 1.0 mg/kg succinylcholine during propofol/fentanyl/nitrous oxide anesthesia. Neuromuscular function was monitored by TOF using mechanomyography. At 10%-20% spontaneous recovery of the first twitch of TOF, the mode of stimulation was changed from TOF to 1-Hz single-twitch stimulation followed by a tetanic stimulus (50 Hz) for 5 s. Three seconds later, the single twitch (1 Hz) was applied again for approximately 30 s followed by TOF stimulation until full recovery of the TOF response. Succinylcholine-induced neuromuscular block had the following characteristics: 1) twitch augmentation before twitch depression, which was seen more frequently in patients given smaller doses (0.1 and 0.3 mg/kg) than in those given larger doses (0.5-1.0 mg/kg); 2) TOF fade during onset and recovery of the block; 3) tetanic fade; and 4) and posttetanic potentiation. Posttetanic potentiation was related to the pretetanic twitch height but was not related to the dose of succinylcholine administered. Some characteristics of Phase II block were detectable during onset and recovery from doses of succinylcholine as small as 0.30 mg/kg. Posttetanic potentiation and fade in response to train-of-four and tetanic stimuli are characteristics of neuromuscular block after bolus administration of different doses of succinylcholine., Implications: Posttetanic potentiation and fade in response to train-of-four and tetanic stimuli are characteristics of neuromuscular block after bolus administration of different doses of succinylcholine. We also conclude that some characteristics of a Phase II block are evident from an initial dose (i.e., as small as 0.3 mg/kg) of succinylcholine.

Background: The authors reappraised the conventional wisdom that the intubating dose of succinylcholine must be 1.0 mg/kg and attempted to define the lower range of succinylcholine doses that provide acceptable intubation conditions in 95% of patients within 60 s., Methods: This prospective, randomized, double-blind study involved 200 patients. Anesthesia was induced with 2 mug/kg fentanyl and 2 mg/kg propofol. After loss of consciousness, patients were randomly allocated to receive 0.3, 0.5, or 1.0 mg/kg succinylcholine or saline (control group). Tracheal intubation was performed 60 s later. A blinded investigator performed all laryngoscopies and also graded intubating conditions., Results: Intubating conditions were acceptable (excellent plus good grade combined) in 30%, 92%, 94%, and 98% of patients after 0.0, 0.3, 0.5, and 1.0 mg/kg succinylcholine, respectively. The incidence of acceptable intubating conditions was significantly greater (P < 0.05) in patients receiving succinylcholine compared with those in the control group but was not different among the different succinylcholine dose groups. The calculated doses of succinylcholine (and their 95% confidence intervals) that were required to achieve acceptable intubating conditions in 90% and 95% of patients at 60 s were 0.24 (0.19-0.31) mg/kg and 0.56 (0.43-0.73) mg/kg, respectively., Conclusions: The use of 1.0 mg/kg of succinylcholine may be excessive if the goal is to achieve acceptable intubating conditions within 60 s. Comparable intubating conditions were achieved after 0.3, 0.5, or 1.0 mg/kg succinylcholine. In a rapid-sequence induction, 95% of patients with normal airway anatomy anesthetized with 2 mug/kg fentanyl and 2 mg/kg propofol should have acceptable intubating conditions at 60 s after 0.56 mg/kg succinylcholine. Reducing the dose of succinylcholine should allow a more rapid return of spontaneous respiration and airway reflexes.

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