By MHAUS President Henry Rosenberg MD
The most common reason for producing such paralysis is to intubate (place a breathing tube) in a patient's trachea in order to control ventilation of the lungs. In many cases intubation is done for non-emergent reasons, for example routine surgery, but at other times the drug is administered to gain control of ventilation in an emergency. An example of such an emergency is a patient who is in acute distress from shock or from trauma in order to ensure that the patient is receiving an adequate concentration of Oxygen and carbon dioxide is being effectively eliminated from the body. This scenario may occur in an emergency room, or a critical care unit. In another scenario, a patient receiving sedative medication as part of a procedure such as a colonoscopy suddenly stops breathing and begins to show signs of hypoxia (low Oxygen). The anesthesiologist or nurse anesthetist must then immediately gain control of the airway most often by intubating the trachea. Although there are other drugs that produce paralysis rapidly, succinylcholine is usually favored because its action is rapid and predictable, and the effect wears off spontaneously in three to four minutes.* The alternative paralyzing drugs generally last for 20 minutes or more, although there are ways to hasten the reversal of the paralysis to a limited extent.
Sounds like succinylcholine is a great drug and in many ways it is. However there are a variety of mild to severe side effects associated with succinylcholine. For example, some people experience annoying muscle pain lasting several days, heart rhythm changes that may be transient or in certain circumstances life threatening. As many of you who are interested in MH know already, succinylcholine is also a trigger of MH in the susceptible patient. Succinylcholine, because it produces paralysis, is rarely given by itself. Most often it is preceded by an intravenous anesthetic agent such as propofol or thiopental to render the patient unconscious and is then followed by administration of one of the anesthetic gases for maintenance of anesthesia. For children the usual procedure is to anesthetize the child with a gas anesthetic, thereby avoiding placement of an intravenous line while the child is awake followed by other agents to facilitate placing the endotracheal tube. After MH was described in the 1960s it was soon noted that succinylcholine seemed to accelerate the onset and severity of MH. Cases of MH were reported regularly with gas anesthetics with and without succinylcholine. In the animal model for MH, namely certain breeds of swine, succinylcholine alone in the presence of sedatives was clearly demonstrated to precipitate MH. However, there are only a few cases of MH apparently precipitated by succinylcholine in the absence of the gas anesthetic agents reported in the medical literature even though probably one in 3,000 patients carry the genetic mutation that is associated with MH susceptibility. Perhaps that is because everyone in anesthesia already knows that succinylcholine is a trigger for MH.
There is another complication of succinylcholine also. In a small but significant number of patients succinylcholine will produce jaw muscle rigidity rather than relaxation, making mouth opening to insert the endotracheal tube almost impossible. The rigidity lasts several minutes and when followed by one of the MH trigger agents will often result in either outright MH and /or muscle breakdown manifest as brown or cola colored urine and the chance of renal damage.
All of this is background to the controversy I wish to describe. Because our MH experts believe that there is enough evidence that succinylcholine is an MH trigger, then dantrolene must be immediately available wherever succinylcholine may be used. In many outpatient settings and offices where superficial procedures such as endoscopy or oral surgery are performed gas anesthetics that trigger MH are not used, but (and this is a big one) succinylcholine is available for emergency management of a compromised airway. Because there are only a few cases of MH precipitated by succinylcholine that have been reported in the literature and because a full supply of dantrolene costs approximately $2500 with a three year shelf life, some have questioned the requirement that dantrolene be present in those settings where succinylcholine is reserved for emergencies only. I have been told that some anesthesia providers, in order to avoid the requirement that dantrolene be present if succinylcholine may be used, have chosen not to stock succinylcholine. Without succinylcholine there are concerns that patients may be harmed because it may not be possible to control the airway and low Oxygen levels may lead to brain and heart damage. In fact loss of control of the airway is one of the more common reasons for patient injury.
So, the issue comes down to a rare event (MH) that is fatal 80% of the time without dantrolene versus the cost of the drug (about $850/year) that may never be used. Although it is true that succinylcholine is an excellent medication to control the airway and is the preferred drug by anesthesia providers and critical care physicians, there are alternative medications and devices to secure the airway. Because we are dealing with events that are either very uncommon, but with well known complications, they are not reported in the medical literature, so it is hard to do a cost effectiveness analysis. With the advent of electronic medical records and with more aggressive tracking of quality data including adverse events, it might be possible to accumulate sufficient data to make a determination as to how often dantrolene is used to rescue a patient who develops MH when triggered by succinylcholine in the absence of gas anesthetics. But for now, the MH experts associated with MHAUS feel that because MH is almost uniformly fatal without dantrolene, a full supply of dantrolene should be immediately available when MH trigger agents including succinylcholine are used or when there is even a possibility that succinylcholine will be used. There is definitely a need for a large multicenter study on the issue of the cost effectiveness of dantrolene in outpatient surgery centers. Up to this point the accrediting agencies agree with the MH experts.
* However, in about one in 2500 patients succinylcholine will produce paralysis for an hour or more. This is because some patients lack or have an aberrant enzyme the degrades succinylcholine.