Anesthetic Management of a Patient With Restless Legs Syndrome: A Case Report

Abstract

Restless legs syndrome (RLS) is a neurological sensory disorder associated with sensory and motor symptoms that most commonly occur at night and during periods of rest. It is characterized by altered or abnormal sensations primarily in the legs and the urge to move the associated limbs. Perioperative procedures, including general anesthesia, can cause exacerbations of RLS. This is a case report of a suspected RLS exacerbation in a 22-year-old woman who had no formal diagnosis of RLS despite reporting symptoms that met all essential diagnostic criteria by the International RLS Study Group. Despite her previous diagnoses of dehydration induced-muscle pain or nocturnal cramps, we suspected her to have RLS. The patient underwent general anesthesia for a bilateral sagittal split ramus osteotomy using a combined inhalational and intravenous anesthetic technique with sevoflurane, propofol, remifentanil, and dexmedetomidine. After successful completion of the surgery and returning to the ward, she began moving her lower extremities and complaining of unpleasant sensations in both ankles. Bed rest exacerbated the suspected RLS symptoms despite a continuous infusion of dexmedetomidine. The RLS symptoms continued to worsen and spread to her upper extremities. After increasing the dexmedetomidine infusion from 0.2 to 0.4 μg/kg/h, almost all symptoms improved, and she slept for 3 hours. Upon awakening, the unpleasant sensations were completely relieved by walking and stretching. The patient was formally diagnosed with RLS by a neurologist after discharge. In this case, an infusion of dexmedetomidine was helpful in successfully managing a suspected exacerbation of RLS.

Restless legs syndrome (RLS) is a neurological sensory disorder characterized by sensory and motor symptoms that tend to arise at night or during periods of inactivity.^1–3 RLS causes uncomfortable or unpleasant sensations in the legs and an urge to move them. Reported sensations vary widely and can include hot or cold sensations, tingling, creeping, pulling, and pain.^1–3 Patients often report partial or temporary relief of these sensations by movement, such as walking or stretching.³ Postoperatively, patients may experience exacerbations of their RLS symptoms due to immobility and/or pain.² We report a case of a suspected RLS exacerbation following bilateral sagittal split ramus osteotomy under general anesthesia. The patient consented to the publication of her information for this case report.

CASE PRESENTATION

A 22-year-old woman (height 156 cm; weight 53 kg; body mass index 21.2 kg/m²) with suspected RLS was scheduled for bilateral sagittal split ramus osteotomy under general anesthesia secondary to a preoperative diagnosis of skeletal class II malocclusion. The patient was otherwise healthy with an unremarkable family history. However, she reported having a continuous urge to move her legs at rest before sleeping since the third grade in school. Although her symptoms met all of the essential diagnostic criteria established by the International Restless Legs Syndrome Study Group, she had not been formally diagnosed with RLS at the time of her preoperative consultation.³ She reportedly thought these sensations were a normal state everyone experiences and that she could adequately cope with these sensations. Although the patient denied notifying her primary care doctor about this issue, she did consult with a general internist in our hospital who proceeded with a home sleep apnea test demonstrating a respiratory event index of 5.4 events/h and resulting in a diagnosis of mild sleep apnea. Her nocturnal sensory and motor symptoms that we felt were suggestive of RLS were diagnosed as dehydration-induced muscle pain or nocturnal cramps. However, after receiving her assessment from the initial general internist in our hospital, we proceeded with the planned surgery under the suspected diagnosis of RLS.

On the day of the surgery, the patient's vital signs were otherwise normal (blood pressure 115/75 mm Hg; heart rate 80 beats per minute in a normal sinus rhythm; and SpO₂ 99% in room air). General anesthesia was induced with a target-controlled infusion (TCI) of propofol (5 μg/mL) by Terufusion TCI Pump (TE-371), a continuous infusion of remifentanil (0.3 μg/kg/min), and a rocuronium bolus (30 mg) followed by nasal intubation. General anesthesia was maintained using sevoflurane (0.5%) with air and oxygen (3:1 L/min), infusions of propofol (TCI rate 2.0–2.4 μg/mL), remifentanil (0.2–0.3 μg/kg/min), and dexmedetomidine (0.2 μg/kg/h), which was used for postoperative sedation and analgesia. Local anesthesia was administered intraoperatively via 1% lidocaine (190 mg) with 1:100,000 epinephrine (0.19 mg). The patient's intraoperative vital signs were generally stable (blood pressure 85–130/40–85 mm Hg; heart rate 52–80 beats per minute; SpO₂ 99–100% at FiO₂ of 0.4). Dexamethasone (3.3 mg) was administered intraoperatively for postoperative edema per the oral surgeon's instructions. The patient was extubated awake uneventfully after discontinuing the propofol and remifentanil but continuing the dexmedetomidine (0.2 μg/kg/h). Total anesthesia time was 3 hours and 19 minutes, surgical time was 2 hours and 22 minutes, total intraoperative fluid volume was 1250 mL, total urine output was 300 mL, and there was minimal bleeding.

Postoperatively, the dexmedetomidine infusion was continued for analgesia at the same rate. However, she began to move her lower limbs and complain of RLS-like sensations (ie, ants creeping on both ankles) shortly after returning to the ward. Although movement may be induced by acute postoperative pain, it was felt that her urge to move her legs was more likely due to the suspected RLS. Despite massaging her ankles, the urge to move her legs increased, and her mother requested transfer to a different hospital. These uncomfortable and unpleasant sensations gradually grew in severity (10/10), but she denied any pain in her legs at this time. She also reported spread of the unpleasant sensations into the upper extremities. We attempted to improve her sensations using a foot pump for intermittent pneumatic compression as a previous report indicated that the use of graduated compression stockings and calf compressors may be beneficial.⁸ However, she wanted both legs massaged simultaneously, and the effect was not sufficient.

It was felt that bed rest was important for her postoperatively, so the dexmedetomidine infusion was increased (from 0.2 to 0.4 μg/kg/h) for added analgesia and sedation. She was monitored for resolution of her RLS-like symptoms in addition to any perioperative side effects, respiratory depression, and cardiovascular depression. By 1 hour later, the dexmedetomidine had improved almost all her symptoms and she soon fell asleep, at which point we stopped the infusion. When she woke up 3 hours later, she could walk and stretch, which further helped to resolve the symptoms of her RLS exacerbation.

The suspected RLS symptoms never returned throughout the remainder of her hospital stay. She was referred to the department of neurosurgery in another hospital for evaluation of the suspected RLS prior to being discharged. The consulting physician subsequently diagnosed her with RLS and prescribed pramipexole (a dopamine agonist) after magnetic resonance imaging of her brain confirming no structural abnormalities.

DISCUSSION

RLS is a chronic neurological sensory disorder, first described in 1685, that interferes with rest and sleep.^1–3 The prevalence of RLS is typically low in Asian countries and approximately 1 to 4% in Japan. It has a higher prevalence in women versus men. Early-onset RLS has a peak incidence at 20 to 40 years of age, and a prevalence of 1.9% among children aged 8 to 11 years.¹ The onset of suspected RLS symptoms in our patient was in the third grade/elementary school. Exacerbations of RLS symptoms have been associated with iron deficiency, renal failure, pregnancy, Parkinson's disease, neuropathies, and several medications, which should be avoided, most notably dopamine antagonists (Table 1).^1,2

Table 1. .

Drugs and Substances Likely To Trigger Exacerbations of Restless Legs Syndrome

Dopamine antagonists Neuroleptics: haloperidol and droperidol Selective serotonin reuptake inhibitor Tricyclic antidepressants Antihistamines Opioid antagonist Caffeine Alcohol Nicotine

A diagnosis of RLS is based on clinical symptoms as it lacks any definitive diagnostic test. Serum iron levels and polysomnography can be useful as iron deficiency and sleep disorders can exacerbate symptoms. Additionally, several other factors (ie, RLS mimics) can cause symptoms easily confused with RLS (Table 2).^3,5 In this case, it was presumed that the polysomnography test would have helped establish a diagnosis of RLS, as RLS can be associated with sleep disorders and limb movements during sleep.⁶ However, the respiratory event index results were felt to be insufficient to support such a diagnosis, leading instead to the RLS mimics (Table 2).^3,5 Patients with RLS are significantly less likely to report worsening hypersomnolence or sleepiness following surgery under general anesthesia.⁶ The patient notedly had no central disorders of hypersomnolence or moderate-to-severe obstructive sleep apnea.

Table 2. .

Restless Legs Syndrome (RLS) Mimics That Produce Symptoms Similar to RLS

Positional discomfort Sleep starts Nocturnal leg cramps Pain Neuroleptic-induced akathisia Vascular intermittent claudication Peripheral neuropathy Myelopathy Painful leg and moving toe syndrome

Normalizing serum iron levels (ferritin concentration) is an important preoperative consideration for people with RLS.^1,2 Metabolism of iron and dopamine in the central nervous system are thought to have similar circadian rhythm modulations with high levels during daytime and low, likely deficient levels at night.¹ Regarding the pathophysiology of RLS, dopamine receptor downregulation coupled with low dopamine activity at night may enhance glutamatergic responses in the dorsal horn of the spinal cord. As a result, RLS symptoms are likely induced by dysfunction in spinal processing following glutamate release at the postsynaptic membrane.⁷ Therefore, patients who develop symptoms of RLS at night are commonly prescribed iron supplements and dopamine agonists.^1,2 Treatment of iron deficiency in a patient with RLS should aim for a ferritin concentration above 45 μg/L.⁸ Dopamine agonists like pramipexole are effective for managing RLS. These drugs should be continued during the perioperative period and are recommended for initial management of any RLS exacerbations postoperatively.²

In this case, the patient had no formal diagnosis and a reportedly low frequency of RLS occurrences that did not require management. RLS is mainly treated with dopamine agonists,^1,2 but in this case, it was relieved by increasing the dexmedetomidine infusion without the use of benzodiazepines or opioids. A patient with excessive postoperative movements should be carefully assessed as it could be due to acute postoperative surgical pain. This patient was able to confirm effective analgesia with the dexmedetomidine infusion, and we were able to rule out a cerebrovascular or neuro-muscular disorder, leading to the working diagnosis of an RLS exacerbation.

Dexmedetomidine is an α2 adrenoceptor agonist that acts in the brain to produce sedation, anxiolysis, and inhibition of sympathetic nervous system activity, and within the spinal cord to cause analgesia.^10,11 Anesthetic management with total intravenous anesthesia combined with dexmedetomidine infusions (0.3 μg/kg/h) is effective for laparoscopic cholecystectomies and reduces the total consumption of propofol and remifentanil by 16% and 23%, respectively.¹⁰ In our experience, total intravenous anesthesia combined with dexmedetomidine (0.2 μg/kg/h) produces satisfactory analgesia without the use of fentanyl in osteotomy procedures and prevents postoperative respiratory depression. In this case, dexamethasone was used as a supplement for postoperative edema, but ideally non-steroidal anti-inflammatory drugs could have also been administered for additional management of postoperative swelling and pain. Dexmedetomidine is associated with spinal nociceptive processing and, unlike fentanyl, enhances the descending inhibition and decreases the descending facilitation to modulate pain and nociception.¹³ As an α2-agonist, dexmedetomidine produces potent antinociceptive effects and reduces release of the spinal neurotransmitter glutamate at the postsynaptic membrane.^14,15 Dexmedetomidine, as well as dopamine-2 receptor agonists, could help normalize sensory processing by inhibiting glutamate release in the dorsal horn.^14,15 In this case, dexmedetomidine relieved the RLS symptom exacerbation potentially by counteracting the increased spinal excitability that occurs in patients with RLS.⁷

When developing an anesthetic plan for patients with RLS, inhalational/volatile and intravenous anesthetic agents are generally considered safe, and opioid agonists, benzodiazepines, and ketamine are effective agents for preventing an RLS exacerbation.^2,16 The major concern includes drugs that have dopamine antagonistic activity, such as metoclopramide and droperidol, which can exacerbate RLS and are contraindicated (Table 1).^1,2 In this case, we used a combined intravenous-volatile anesthesia method that effectively decreases the incidence of postoperative nausea and vomiting, reducing the need for antiemetics.¹⁷ Combined intravenous-volatile anesthesia is an acceptable method for preventing anesthetic awareness. Relatively low concentrations of volatile inhaled anesthetics (0.25 minimum alveolar concentration [MAC]) can cause loss of consciousness and amnesia.¹⁸ Although 1 report indicates that 0.7 to 1.3 MAC would be effective,¹⁹ in this case we simultaneously used 0.5% sevoflurane (0.25 MAC) considering the synergistic effects of propofol, remifentanil, and dexmedetomidine.

CONCLUSION

A 22-year-old female patient with no formal diagnosis of RLS experienced a suspected RLS exacerbation following general anesthesia for a bilateral sagittal split osteotomy. The patient's suspected RLS symptoms were effectively managed by a continuous infusion of dexmedetomidine. Additional anesthetic considerations include the avoidance of any drugs likely to trigger RLS exacerbations in at-risk patients such as dopamine antagonists.