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Print version ISSN 0034-7094
Rev. Bras. Anestesiol. vol.56 no.4 Campinas Set./Aug. 2006
Outpatient Anesthesia for Radiotherapy in a Patient with Myasthenia Gravis. Case report*
Anestesia ambulatorial para radioterapia en paciente portador de miastenia gravis. Relato de caso
Raquel Marcondes BussolottiI; Maria Jacqueline BoscariolI; Eduardo Henrique Joaquim GiroudII
do Hospital do Câncer
IIDiretor do Departamento de Anestesiologia do Hospital do Câncer; Professor da Disciplina de Anestesiologia, Dor e Terapia Intensiva da Universidade Federal de São Paulo EPM/UNIFESP
OBJECTIVES: Myasthenia Gravis (MG) is a rare autoimmune disease, characterized
by the reduction in the number of nicotinic receptors in the neuromuscular junction,
with an incidence of 14/100,000. The objective of this report is to describe
the case of a patient with myasthenia gravis who underwent balanced general
anesthesia for radiotherapy of a spinocellular carcinoma of the parotid gland
as an outpatient.
CASE REPORT: Male patient, 87 years old, 87 kg, physical status ASA III, with a prior history of myasthenia gravis; stroke; pacemaker for a third-degree AV block; and hypertension. He was scheduled for seven 20-minutes radiotherapy sessions under general anesthesia. In the radiotherapy room he was monitored with a cardioscope, noninvasive blood pressure, pulse oxymeter, and underwent general anesthesia with propofol and sevoflurane. After the induction, he maintained spontaneous ventilation with a Guedel canula and nasopharyngeal catheter with O2 /sevoflurane for proper fitting of the immobilizing mask. He did not present any complications in the post-anesthetic recovery room.
CONCLUSIONS: The choice of anesthetics and strict clinical follow-up allowed an elderly patient, with prior stroke and cardiopathy, to be submitted to balanced general anesthesia for radiotherapy, as an outpatient, with good response.
Key Words: ANESTHESIA, Ambulatorial; DISEASES: miastenia gravis; THERAPEUTIC: radiotherapy.
Y OBJETIVOS: La Miastenia Gravis (MG) es una enfermedad auto inmune rara,
caracterizada por la reducción de receptores nicotínicos en la
junción neuromuscular, con incidencia de 14/100.000. El objetivo de este
relato fue el de describir el caso del paciente portador de miastenia gravis
sometido a la anestesia general balanceada, para tratamiento radioterápico
de carcinoma espinocelular de parótida en régimen ambulatorial.
RELATO DEL CASO: Paciente del sexo masculino, 87 años, 87 kg, estado físico ASA III, con historial de miastenia gravis; accidente vascular encefálico previo (AVE); marcapaso por bloqueo atrio-ventricular total; hipertensión arterial sistémica (HAS). Fueron programadas siete sesiones de radioterapia de 20 minutos para tratamiento del tumor de parótida bajo anestesia general. En la sala de radioterapia fue monitorizado con cardioscopio, monitor de presión arterial no invasiva, oxímetro de pulso y sometido a anestesia general con propofol y sevoflurano. Después de la inducción, se mantuvo en ventilación espontánea con cánula de Guedel y catéter nasofaríngeo con O2 /sevoflurano, para acomodación de la máscara de inmovilización. En la sala de recuperación postanestésica, no presentó complicaciones.
CONCLUSIONES: La elección de los anestésicos y el acompañamiento clínico de criterio permitieron la buena evolución del paciente, con AVE previo, cardiopata y anciano, sometido a la anestesia general balanceada para procedimiento de aplicación de radioterapia, en régimen ambulatorial.
Myasthenia Gravis (MG) is an autoimmune disease, characterized by episodic muscle weakness. Anesthesia in these patients must be done very carefully to avoid worsening of the symptoms, especially those concerning the respiratory system.
It is even more challenging when the patient has to be immobilized to undergo radiotherapy, using short-acting anesthetics, with fast recuperation, and in an environment in which the anesthesiologist cannot be by the patient.
The objective of this study is to report the case of a patient with myasthenia gravis, who underwent balanced general anesthesia for radiotherapy for spinocellular carcinoma of the parotid gland as an outpatient.
A male patient, 87 years old, weighing 87 kg, physical status ASA III, with a history of myasthenia gravis, a stroke 6 months before with an expressive aphasia, hypertension, pacemaker for a third-degree AV block, and a tumor in the parotid gland, was referred to the Anesthesiology Department for evaluation and to be submitted to general anesthesia, since the patient was noncooperative with the required immobilization for radiotherapy. His medication included acetylsalicylic acid (250 mg), hydrochlorothiazide (50 mg), prednisone (7.5 mg.d-1), pyridostigmine bromide every 8 hours, and pantoprazole.
The patient was awake, calm, normotrophic, eupneic, hydrated, mucous membranes pink, difficulty to speak and to walk without support, BP 120 x 80 mmHg, heart rate 72 bpm, and Malampatti score II.
Laboratory exams showed hemoglobin 12 g.dl-1; BUN 35 mg.dl-1; creatinine 1.1 mg.dl-1; glucose 100 mg.dl-1; coagulation was normal. Chest X-ray showed and enlarged aorta and a pacemaker on the left side; ECG showed pacemaker rhythm (HR = 72 bpm); echocardiogram revealed an ejection fraction of 0.64, abnormal relaxation of the left ventricle, and senile changes of the mitral, aortic, and tricuspid valves.
At the end of the evaluation, the anesthetic-surgical risk was determined, and the risks of the procedure were explained to the patient's family members.
After discussion with the members of the Radiotherapy Department, we decided to admit the patient and to reserve an ICU bed in case there were any complications. Seven sessions, once a week, lasting 20 minutes each, were scheduled.
In the first session, the patient was taken to the radiotherapy room, where he was monitored with a cardioscope, pulse oxymeter and noninvasive blood pressure, and venipuncture was done with a 22G catheter. Ringer's lactate was administered and induction with propofol (80 mg) and 4% sevoflurane was initiated. After establishment of an adequate anesthetic plane, a thermoplastic mask was secured in place; an oropharyngeal catheter was introduced through the Guedel canula, allowing the patient to breath spontaneously with the administration of O2 and sevoflurane. During the radiotherapy, the patient was monitored with a pulse oxymeter, placed outside the radiotherapy equipment and, with the aid of a camera, the cardioscope was monitored and the patient observed for any signs of movement. After the procedure (that lasted 20 minutes), the patient was transferred to the post-anesthetic recovery room. He evolved to a calm awakening, without any complications, being transferred to a regular room, where the patient ate and walked, being discharged from the hospital six hours after the beginning of the procedure.
The same monitoring and anesthetic technique were used in the following sessions, and the patient was also discharged home six hours after the procedure.
After the fourth session, there was worsening of the neurological status, with a subtle reduction in cough effectiveness and difficulty in maintaining the postural tonus, but without interfering with the anesthetic evolution and post-anesthetic recovery. The patient was evaluated by a neurologist, who considered that the worsening neurological status did not warrant stopping the treatment or changing his medication.
In the last session, there was a reduction of the SpO2 (85%) during the radiotherapy, requiring interruption of the procedure. After removal of the thermoplastic mask, the ventilatory pattern was restored immediately, and the patient was discharged home six hours after the procedure.
Myasthenia gravis is an autoimmune disease, characterized by the reduction in the number and in the function of the nicotinic receptors in the neuromuscular junction. Its incidence is 14/100,000, and women are affected twice as often as men.
Around 70% to 90% of myasthenic patients have anti-acetylcholine receptor antibodies. The antibodies damage the post-synaptic membrane through a complement-mediated reaction, increasing the degradation and decreasing the formation of acetylcholine receptors. It is accepted that the immunological breakup originates in the thymus, since 90% of the patients present histological abnormalities in the gland, such as thymona and hyperplasia. Despite the evidence of the role of antibodies, their titers do not correlate with the severity of the disease. Other autoimmune diseases, such as systemic lupus erythematosus, rheumatoid arthritis, pernicious anemia, and thyroid diseases, may be associated with myasthenia gravis1,2.
The clinical characteristic of the disease is the episodic muscle weakness exacerbated, during the day, by their repetitive use. The patients alternate periods of exacerbation and remission. Any skeletal muscle can be affected, although there is a predilection for muscles innervated by the cranial nerves, leading to diplopia, ptosis, dysphagia, and dysarthria. The initial symptoms include diplopia, dysarthria, regurgitation, and weakness of the skeletal and respiratory muscles. Respiratory failure is rare.
According to Osserman2, myasthenia gravis is classified based on the muscle groups affected:
- Type I (10% of the cases) only ocular signs and symptoms;
- Type II A (40% of the cases) mild generalized muscle weakness;
- Type II B moderate generalized muscle weakness, or bulbar dysfunction, or both;
- Type III acute fulminating, or respiratory dysfunction, or both; and
- Type IV severe cases with generalized myasthenia (Types II B, III, and IV represent 50% of the cases).
Several conditions can trigger or exacerbate the symptoms of myasthenia gravis, such as viral infection, pregnancy, stress, surgeries, anesthetics, neuromuscular blockers, benzodiazepines, long-acting opioids, antiarrythmic agents, and antibiotics.
The diagnosis is based on the history and neurological exam, test with edrophonium, electromyography, and detection of anti-acetylcholine receptor antibodies. None of these tests is diagnostic in itself. For example, the administration of edrophonium can increase muscular strength in patients with myasthenia and in those with other neuromuscular diseases1,2.
Treatment can be divided in symptomatic, with the administration of anticholinesterase; anti-pathogenic, with corticosteroids; and immunomodulator, with thymectomy, plasma- pheresis, immunosuppressors, and immunoglobulins.
Myasthenic crises, defined as exacerbation of the symptoms involving the respiratory muscles, usually triggered by upper airway infections and pneumonia, leading to respiratory failure and the need for intubation and respiratory assistance, occurs in 15% to 20% of the patients during the course of the disease. Cholinergic crises is a consequence of the excess of anticholinesterase agent, consisting of worsening of the myasthenia gravis, along with vomiting, diarrhea, increased salivation, and bradycardia1,2.
Surgery is the primary treatment for a parotid gland tumor. When patients refuse surgery or do not have the clinical conditions to be submitted to surgery, have inoperable lesions, or distant metastasis, they are referred to radiotherapy, as a palliative or, occasionally, curative treatment3.
The administration of fractionated radiotherapy requires the precision of reproducing, daily, the positioning of the patient. Inadequate immobilization may result in the wrong localization of the radiation entry fields, hindering its application. Missing the target may result in a 10% or greater dose reduction and, at the same time, an increase in the dose delivered to important organs localized around the target, increasing the possibility of complications. For some patients, this may represent the difference between cure, relapse, or treatment failure. Therefore, the importance of the daily reproduction of the treatment prescribed, planned, and executed, limiting patient movement during the treatment session, is clear4. After securing the thermoplastic mask and positioning the patient correctly, the team should leave the room, and observe the patient and follow the cardiac monitoring through a camera. The pulse oxymeter should be outside the room, connected to an extension.
Since the first thymectomy was performed in 1911 for the treatment of myasthenia gravis, research has been aimed at discovering the ideal anesthetic agent. The possibility of respiratory failure limits the use of sedatives, opioids, hypnotics, and neuromuscular blockers5.
Opioids should be administered very carefully, in reduced doses or continuous infusion of short acting drugs6.
The improper use of neuromuscular blockers may cause the need for mechanical ventilation in the postoperative period. When these drugs are indicated, one should prefer intermediate or short acting agents. Atracurium, rocuronium, and mivacurium may be safely used. The response to acetylcholine is unpredictable; there may be resistance, prolonged effect, or unusual response6,7.
The majority of the works show a preference for general anesthesia with one agent or in association with propofol and sevoflurane. When propofol was used for induction and maintenance of anesthesia for thymectomy, patients were extubated in the OR and did not require mechanical ventilation in the postoperative period8. Sevoflurane's low gas/blood coefficient of solubility, fast elimination, good muscular relaxation, and accurate and fast adjustment of the anesthetic plane, make it safe to be used as the only agent for induction and maintenance of anesthesia5,9,10.
The use of propofol or sevoflurane for induction and maintenance of anesthesia, without neuromuscular blockade, provides good conditions in the peri and postoperative, with minimal change in the neuromuscular function5,8-10.
The preoperative discontinuation of anticholinesterase agents is controversial due to the side effects, bradycardia, and increased salivation. For some patients, the use of a parenteral preparation with pyridostigmine bromide is proposed; for others, the anticholinesterase agent is discontinued six hours before the surgery, being restarted carefully in the postoperative period11.
The patient presented here was instructed to maintain the use of the anticholinesterase agent, since he had a pacemaker with fixed frequency and did not present increased salivation and/or altered swallowing due to neurological deficit.
The challenge in this case was to schedule a short acting anesthesia, without intubation, for seven weeks (once a week) for a patient with myasthenia gravis. We decided to use a balanced anesthesia with sevoflurane and propofol, to guarantee the patient would not move during the procedure and, at the same time, allow for a good ventilatory pattern while the anesthesiologist was outside the radiotherapy room.
As a rule, anesthesia for patients with the diagnosis of MG should not be done as an outpatient basis, since they need post-anesthetic follow-up, especially regarding the respiratory function.
We decided to start the radiotherapy sessions after the patient was admitted to the hospital and reserved a bed in ICU for the post-anesthetic period.
Figure 1 shows the positioning of a patient, anesthetized and monitored, for radiotherapy of the head.
On the first day the patient presented good recovery, walked within 6 hours of the procedure, and his respiratory function was not compromised. We decided, then, to discharge the patient six hours after the anesthesia, with the appropriate information and recommendations to return to the hospital in case anything happened.
The desaturation during the last session was attributed to the difficulty in obtaining an adequate neck extension when the thermoplastic mask was secured in place. It was obvious that the patient's comorbidities contributed for it. When the desaturation was observed, the session was interrupted and the thermoplastic mask was removed, with normalization of the ventilatory pattern.
The patient did well during the treatment, did not have to seek medical attention in the period between sessions, even after the report of a slight worsening of cough efficacy and in maintaining postural tonus.
We observed that the choice of the anesthetic agent was responsible for the maintenance of the patient's respiratory pattern, who remained separated from the anesthesiologist during the radiotherapy. The close clinical follow-up and the good recuperation after the anesthesia allowed the procedure to be done as an outpatient basis.
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Dra. Raquel Marcondes Bussolotti
Deptº de Anestesiologia Hospital do Câncer
Rua Prof. Antonio Prudente, 211
01509-900 São Paulo, SP
Submitted for publication
8 de setembro de 2005
Accepted for publication em 3 de abril de 2006
* Received from Departamento de Anestesiologia do Hospital do Câncer, São Paulo, SP.