Should succinylcholine continue to be the first line muscle relaxant for urgent out of the OR intubation?
Succinylcholine and rapid sequence intubation – Two different chapters written by different authors in Miller’s Anesthesia state that succinylcholine remains the muscle relaxant of choice for rapid sequence intubation (1,2). However, they provide a huge list of clinical situations in which succinylcholine should not be used. Stene and Grande challenge the conventional wisdom and with respect to trauma patients note that “many trauma patients present for anesthesia without a complete medical/anesthetic history … [so that] the side effects of succinylcholine must be taken seriously and balanced against the benefits of the drug (3).
Hyperkalemia and cardiac arrest after succinylcholine – There are many contraindications to the use of succinylcholine because of disease states that increase the risk of succinylcholine related hyperkalemia and cardiac arrest. Many patients who require urgent out of the OR intubation may have one or more of the following:
• Severe metabolic acidosis with hypovolemia
• Severe abdominal infection – sepsis
• Critical illness polyneuropathy
• Prolonged immobilization (typically associated with prolonged neuromuscular blocking drug use)
• Severe traumatic injury
• Crush injury
• Spinal cord injury
• Stroke with hemiplegia or paraplegia
• Closed head injury without peripheral paralysis
• Muscular dystrophies
• Guillian-Barre syndrome
• Motor neuron diseases such as Amyotrophic lateral sclerosis
• Severe burns
Difficulty in obtaining pertinent clinical information in acute situations – One of the key issues that might make succinylcholine an unacceptable risk in many of the out of the OR situations is the difficulty in obtaining the needed medical information. The following are common:
- The history provided and knowledge of the patient’s medical problems is often incomplete – regular nurse off floor, cover resident, etc
- Those caring for the patient may not know the importance of certain clinical issues with respect to anesthesia care and safety and thus fail to provide key information.
- The information provided may be wrong
- The urgency of the clinical situation may preclude more than a cursory, if at all, chart review
- The chart has no problem list
- The chart is large, bulky and key information buried within it
- The chart may have missing pages
- There may be no standardized documentation of prior intubations
- There may be no standardized chart location for airway or intubation information.
Risks of succinylcholine include myalgia, rhadomyolysis, prolonged paralysis, renal failure, and hyperkalemic cardiac arrest – One has to decide if the benefits of succinylcholine (rapid onset, usually rapid offset) outweigh the disadvantages in a given clinical situation. With the ready availability of Laryngeal Mask Airways, the advantages of succinylcholine’s rapid offset in situations of “can’t ventilate” or difficult mask ventilation may be less important now than in the past.
Choice of muscle relaxant for urgent intubations in already hospitalized patients – Both vecuronium and rocuronium in high enough doses can provide reasonable intubating conditions in 60 seconds. Neither drug produces hemodynamic changes at these high doses. Both drugs are free of the risk of hyperkalemic cardiac arrest. Rocuronium may have a slightly faster onset and offset then vecuronium. Some assert that intubating conditions after high dose rocuronium are more uniform than after vecuronium. The main disadvantage of either drug is that prolonged muscle relaxation creates the inability to do an immediate neurologic exam on the patient. I would not think this is a critical issue in most situations. However, if a non depolarizer is used provision must be made, after intubation, for anxiolysis, sedation, or amnesia as is appropriate for the particular patient; three or four hours of awake paralysis is not acceptable.
Dose of non depolarizing muscle relaxant for rapid sequence induction --
– Dose 1 – 1.2 mg/kg
– Onset 60 s
– Intubation conditions are good to excellent – 93%
– Duration 50 min +
– Dose 0.3 mg/kg
– Onset 60 s
– Intubation conditions are good to excellent – 96%
– Duration 83 min +
Ease of use in urgent clinical situations – In a 100 kg patient (probably more typical than the traditional 70 kg norm), the 30 mg of vecuronium for a rapid sequence induction dose requires three 10 mg vials to be opened, diluent added, the container shaken and the dissolved drug then drawn up into three 10 ml syringes or one 50 ml syringe. In contrast the 100 mg of rocuronium required is contained, already dissolved, in a single 10 ml vial. From the point of view of ease of use, rocuronium is much better than vecuronium.
Conclusions and action plan – Because of the potential presence of many conditions that might lead to hyperkalemic cardiac arrest in the patient who requires urgent out of the OR intubation many feel that succinylcholine should no longer be the drug of first choice in this specific clinical situation.
When confronting the patient for a potential urgent out of the OR intubation ask yourself the following questions –
1) Does the patient need intubation?
2) Is direct laryngoscopy appropriate?
3) Does the patient need an induction dose of a hypnotic drug?
4) Does the patient need a neuromuscular blocking drug?
5) Is a non depolarizing muscle relaxant suitable?
6) If 5) is yes then decide on high dose vs. standard intubating dose
7) Is there enough clinical information to determine the suitability of succinylcholine?
1) Naguib M, Lien CA: Pharmacology of muscle relaxants and their antagonists in Miller RD (ed): Miller’s Anesthesia, Philadelphia, Elsevier, 2005, page 504.
2) Dutton RP, McCunn: Anesthesia for trauma in Longnecker DL et al (eds): Anesthesiology, New York, McGraw Hill Medical, 2008, page 2457.
3) Stene JK, Grande CM: Anesthesia for trauma patients in Longnecker DL et al (eds): Anesthesiology, New York, McGraw Hill Medical, 2008, page 1667.
4) For a very nice discussion of succinylcholine in ICU patients as it relates to cardiac arrest secondary to immobilization see Naguib M (ref 1) page 532.
David S. Smith, M.D., Ph.D.