What is the best muscle relaxant for surgical procedures?

Best Muscle Relaxant for Surgical Procedures

For rapid sequence intubation and most surgical procedures requiring tracheal intubation, succinylcholine (1-2 mg/kg) remains the gold standard due to its fastest onset time, though rocuronium (0.9-1.2 mg/kg) is an acceptable alternative, particularly when sugammadex reversal is available. 1

Rapid Sequence Intubation (RSI)

Succinylcholine is the preferred agent for rapid sequence intubation because it provides the shortest onset time (~1 minute) and shortest duration of action of all available muscle relaxants. 1

• A Cochrane meta-analysis of 4,151 patients demonstrated that succinylcholine 1.0 mg/kg provides excellent intubation conditions more frequently than rocuronium (RR = 0.86; 95% CI: 0.81-0.92). 1
• European Society of Anaesthesiology and Intensive Care guidelines make a strong recommendation for fast-acting muscle relaxants: succinylcholine 1-2 mg/kg OR rocuronium 0.9-1.2 mg/kg for RSI. 1

Rocuronium as Alternative

Rocuronium at high doses (≥0.9 mg/kg) is the best non-depolarizing alternative when succinylcholine is contraindicated or when reversal capability with sugammadex is desired. 1

• When comparing succinylcholine 1.0 mg/kg with rocuronium doses >0.9 mg/kg, no superiority of succinylcholine was found in subgroup analysis. 1
• An RCT of 400 critically ill patients found no difference in intubating conditions or desaturation between rocuronium and succinylcholine. 1
• Critical caveat: Lower doses of rocuronium (0.6-0.7 mg/kg) produce less frequent excellent intubating conditions and should be avoided for RSI. 1

Elective Intubation

For elective procedures, rocuronium 0.6 mg/kg (2 x ED95) is recommended as it provides excellent-to-good intubating conditions within 2 minutes while offering intermediate duration. 1, 2

• This dose provides clinical relaxation for a median of 33 minutes (range 14-85 minutes) under opioid/nitrous oxide/oxygen anesthesia. 2
• Muscle relaxant use reduces pharyngeal/laryngeal injury from 22.6% to 9.7% compared to muscle relaxant-free protocols (GRADE 1+ recommendation). 1

Abdominal Surgery

Muscle relaxants are strongly recommended (GRADE 1+) for abdominal laparotomy or laparoscopic surgery to facilitate surgical conditions. 1, 3

• Atracurium is specifically recommended by the American College of Cardiology for laparotomy or laparoscopic abdominal surgery (Grade 1+). 3
• For patients with renal or hepatic insufficiency, atracurium is preferred due to its organ-independent elimination via Hofmann elimination and ester hydrolysis. 3, 4

Special Populations

Obese Patients

Dose rocuronium based on actual body weight, not ideal body weight. 2

• Dosing by ideal body weight results in longer time to maximum block, shorter clinical duration (25 vs 33 minutes), and inferior intubating conditions. 2

Geriatric Patients

Rocuronium 0.6 mg/kg provides excellent-to-good intubating conditions in median 2.3 minutes (range 1-8 minutes) without prolonged recovery times compared to younger adults. 2

Obstetric/Cesarean Section

Rocuronium is NOT recommended for rapid sequence induction in Cesarean section patients. 2

• When rocuronium 0.6 mg/kg was used with thiopental 3-4 mg/kg, intubating conditions were poor or inadequate in 5 of 13 women at 60 seconds. 2

Important Caveats

Avoid rapacuronium for RSI despite its rapid onset, as it causes dose-dependent bronchospasm, tachycardia, and hypotension, particularly at doses >1.5 mg/kg. 5, 6, 7

Atracurium requires caution in patients with cardiovascular disease due to histamine release at higher doses; use lower initial doses (0.3-0.4 mg/kg) administered slowly in these patients. 4

Supraglottic devices generally do NOT require routine muscle relaxant use (GRADE 2 recommendation), though they may be useful when low doses of hypnotics/opioids are used or when airway obstruction occurs. 1