Anaesthesia for Stiff-Person Syndrome.

Abstract

Stiff–Person Syndrome (formally Stiff Man Syndrome) is a rare neurological condition characterised by muscle rigidity and spasm. It is thought to be immunological in origin [1] and is associated with the production of antibodies against glutamic acid decarboxylase, the rate-limiting enzyme for the synthesis of gamma-aminobutyric acid (GABA). Loss of inhibition from higher centres causes over-activity of the gamma motor neurone system and subsequent progressive muscle rigidity. We describe anaesthesia in a man with Stiff–Person Syndrome who presented with respiratory failure secondary to left lung collapse. A 60-year-old man presented to the Accident and Emergency department with respiratory deterioration following treatment for a chest infection. He had a 4-year history of stiffness and spasms and a diagnosis of Stiff–Person Syndrome had previously been made. His efforts at ventilation were severely impaired by rigidity of his thoracic and abdominal muscles. In the Accident and Emergency department, his oxygen saturation on room air was recorded as 86%. His arterial blood gases on high flow oxygen with a reservoir bag indicated a respiratory acidosis (pH 7.29, Po2 7.2, Pco2 8.1, HCO3 28.7, BE 1.0). A chest X-ray showed a `white out' of his left hemithorax and mediastinal shift. A diagnosis of respiratory failure secondary to left lung␣collapse as a consequence of aspiration or secretion retention was made and he was admitted to the Intensive Care Unit. Initial attempts at management with non-invasive ventilation (CPAP of 6 cmH2O) were unsuccessful and his arterial blood gases worsened (Po2 7.0, Pco2 10.2). A decision was made to start invasive ventilation. At this point, no information was available regarding which drugs were safe in this condition. Anaesthesia was induced with midazolam 1 mg and propofol 30 mg. Atracurium 50 mg produced good intubating conditions (Cormack and Lehane grade 2 laryngoscopy) and relaxation of axial and limb stiffness. Following induction he was cardiovascularly unstable requiring ephedrine 30 mg, metaraminol 5 mg and a subsequent norepinephrine infusion to maintain an adequate blood pressure. Anaesthesia was maintained with fentanyl (100 μg.h−1) and midazolam (3 mg.h−1). He was ventilated using BIPAP (P1: 20, P2: 5 ratio 1 : 1, rate 12 breaths.min−1) and his arterial blood gases improved markedly (Fio2 of 0.45: pH 7.38, Po2 17.3, Pco2 6.1, HCO3 26.7, BE 1.4, Spo2 98%). Fibreoptic bronchoscopy was performed and copious amounts of purulent sputum aspirated. Co-amoxiclav 1.2 g q.d.s and fluconazole 200 mg b.d. were commenced following growth of yeasts and coliforms from lavage fluid. The patient's respiratory function gradually improved and he was extubated and discharged to a high dependency unit 72 h after intubation. A second deterioration, 4 days after his initial presentation, prompted a second period of ventilation. This time anaesthesia was induced using alfentanil and propofol. Atracurium provided muscle relaxation and intubation was uneventful. He was subsequently weaned from the ventilator once again and eventually discharged to the ward. Case reports in the neurology literature mention that patients with Stiff–Person Syndrome have received anaesthesia for surgical procedures [2] and periods of ventilation for respiratory failure [3, 4] but no details of anaesthetic management are reported. Johnson and Millar [5] report a case of hypotonia requiring overnight ventilation after anaesthesia for repair of an intrathecal baclofen pump in 46-year-old woman with Stiff–Person Syndrome. Anaesthesia in this case was induced with intravenous sufentanil 10 μg, thiopental 375 mg and vecuronium 8 mg. The mechanism of the resulting hypotonia was unclear, although a subsequent return to theatre for revision of the baclofen pump was reported as uneventful. They recommended avoidance or␣judicious␣use of non-depolarizing muscle relaxants. In our case, the patient remained sedated to facilitate ventilation and stiffness returned once the initial dose of muscle relaxant had worn off. Despite poor pre-induction posture␣due to extreme rigidity, we obtained good intubating conditions on two occasions using atracurium for paralysis. We found no complication with the use of a non-depolarizing muscle relaxant in this case.