Although medical management is the mainstay of treatment of multiple sclerosis (MS), people with MS undergo operations and procedures on a daily basis. Things we now consider common procedures were impossible hundreds of years ago—until humans developed the ability to induce a state of anesthesia. The study of Anesthesiology has been around for centuries, but only recently in the early 1800s was it first described in Western medicine.¹ There are still a myriad of questions surrounding the pharmacokinetics and pharmacodynamics of anesthetics that patients ask commonly in clinical practice: Is it safe? What about in pregnancy? How does it affect MS and how does MS affect the type of anesthetic I receive?

In general, patients receive either general anesthesia, in which they are rendered unconscious, or a nerve block, either neuraxial or peripheral. No single type of anesthetic can be applied to all patients because each patient is complex and each procedure has its own surgical requirements. A pregnant mother may wish to receive a neuraxial anesthetic so that she can witness the birth of her newborn during her nonelective cesarean delivery, while realizing that there is an elevated risk of exacerbating
symptoms. In the same respect, a patient with debilitating MS may receive a muscle relaxant to achieve surgical conditions in order for the surgeon to effectively and safely operate. To plan an anesthetic, knowledge of the patient’s past medical and surgical history, the pathophysiology of MS and its treatments, and the surgical requirements are all necessary.

Owing to the relapsing and remitting nature of MS and the ability of the perioperative period to provoke an MS flare, it is important to have an understanding and documentation of a patient’s baseline function and deficits if present. The additional goals of anesthesia in patients with MS should encompass prevention of relapse, prevention of further neurological damage, and avoidance of drug interactions.

In patients with MS, neurological involvement can exist throughout the central nervous system, leading to various presentations and pathologies to be aware of before providing anesthetic. A thorough understanding of the preoperative neurological deficits is important. For example, cranial nerve involvement may increase the risk of aspiration due to deficits in laryngeal and pharyngeal function. Cervical spinal cord lesions may lead to respiratory abnormalities. Patients should be queried on their ability to clear secretions and strength of cough. If there is respiratory compromise, the severity, treatment, and episodes of mechanical ventilation should be noted and discussed.²,³ Pulmonary function tests may show unchanged lung volumes and capacities, but diffusion capacity may be reduced.² An arterial blood gas may help establish baseline ventilatory physiology. Sleep disorders have been described in patients with MS. The combination of obesity and obstructive sleep apnea may increase postoperative respiratory failure. Because of the lifelong degenerative nature of the disease, optimization for surgery is relative to a patient’s baseline function. Optimization with sleep studies and noninvasive continuous positive pressure may offer benefit in the perioperative period, as well as encouraging smoking cessation when applicable.² If a patient has any new neurological symptoms, it is prudent to delay elective surgery to consult with the patient’s neurologist. Patients with cranial nerve or respiratory involvement should be counseled on the possibility of remaining intubated postoperatively, and the appropriate arrangements should be made with an institution’s intensive care unit (ICU).

Involvement of the thoracic spinal cord may lead to autonomic dysfunction. Should autonomic dysfunction be present in this population it may manifest as episodes of syncope or arrhythmias. The severity of this should be noted as intraoperative fluctuations in blood pressure that may occur, and invasive monitoring may be considered. Invasive monitoring
may include an arterial line, which would measure beat to beat blood pressure variations. In addition, a central venous catheter can be considered for central venous pressure measurements, which may assist with volume resuscitation.

Current treatment regimens should be explored and documented. Chronic use of steroids in patients with MS may require intraoperative administration of steroids, also known as stress dosing, or its osteoporotic sequelae may place the patient at risk for nerve injury. Additionally, certain anticonvulsants, which the patient may be taking, may increase resistance to muscle relaxant administration within the operating room. A list of medications should be provided to the anesthesiologist for consideration in the anesthetic plan.⁴

Numerous factors have been known to contribute to MS relapses including infection, emotional stress, physical trauma, and the perioperative and peripartum periods. Unfortunately for anesthesiologists, at least one of these conditions is met for a majority of the patients they care for on a routine basis. Also, because of the nature of the disease, it can often be impossible to distinguish if a relapse is secondary to anesthetic or is merely coincidental. Because we cannot completely alleviate any single one of these factors and the complicated clinical scenario, it is important to approach patients with MS with care and to involve them as much as possible in their anesthetic care plan, which should be documented in detail.

The anesthetic care of any patient involves three phases of care: induction, maintenance, and extubation.

At induction, an anesthetic is generally given via an inhalational route or an intravenous route. Although cases have been reported of worsening of symptoms with general anesthesia, both routes of anesthetic administration have been safely used in this population and one route is not superior to the other. Another drug given during this phase is a muscle relaxant to obtain optimal intubating conditions, assuming an endotracheal tube is to be placed. Succinylcholine is a depolarizing muscular blocker that causes a well-known increase of extracellular potassium. Patients who are otherwise healthy have a mild increase in potassium, which is usually clinically insignificant, but patients with neuromuscular disease can have an upregulation of extrajunctional acetylcholine receptors, which can cause a life-threatening efflux of potassium from the cell. In patients with severe disease or in an active exacerbation, there have been reports of succinylcholine-induced hyperkalemic cardiac
arrest.²,³,⁵ Thus, this drug should be used with caution in patients with MS and usage should depend on the patient’s current clinical status. In an emergency setting, if there is an alternative available, it would be prudent to avoid succinylcholine for intubation, particularly in patients with obvious neuromuscular involvement (contractures, muscle wasting, wheelchair usage). Alternatively, nondepolarizing muscular blockers, such as rocuronium or vecuronium, can be used. Patients with MS are particularly sensitive to these muscle relaxants. A nerve stimulator should be used to judiciously administer a muscle relaxant, and the anesthesiologist should monitor for return of muscle tone. Quantitative monitors may be more beneficial at centers with a high volume of MS patient population, as they may provide more reliable indicators of return of muscle function.⁶

The maintenance phase is the ongoing delivery of an anesthetic. No one particular anesthetic appears safer than another. In this phase, succinylcholine typically is not given. Nondepolarizing muscle relaxants are generally given during this phase, and as described earlier, a nondepolarizing muscle relaxant should be closely monitored, quantitatively or qualitatively, by an anesthesiologist. During any surgical procedure, the patient’s temperature should be closely monitored as well. Hyperthermia is a well-described trigger of MS, and aggressive temperature control is important.⁷ Special care should be taken when using warmers in the operative room. However, hypothermia is not advisable either and the goal should be to maintain normothermia. Care should also be taken with patient positioning, as further in the disease process, patients may have contractures and positioning may be difficult.