Multivariate determinants of the need for postoperative ventilation in myasthenia gravis

Myasthenia Gravis for Spine Surgery: An Ardous Anaesthetic Journey

Myasthenia gravis (MG) is a neurological disorder involving the post-synaptic neuromuscular junction and is caused by the autoimmune destruction of acetylcholine receptors with ensuing muscular weakness. Rarely is the disease process in MG compounded with other comorbidities and distinctive surgical challenges, such as the prone position in spine surgery, presenting unique challenges in the anesthetic management of such cases. This case series and the ensuing discussion describe the successful perioperative management of two cases of MG undergoing neuro-surgical management for lumbar spine pathologies.

Risk factors of prolonged ventilation after thymectomy in thymoma myasthenia gravis patients

BACKGROUND

To explore the risk factors for prolonged ventilation after thymectomy in patients with thymoma associated with myasthenia gravis (TAMG).

METHODS

We reviewed the records of 112 patients with TAMG after thymectomy between January 2010 and December 2019 in Peking University People's Hospital. Demographic, pathological, preoperative data and the Anesthesia, surgery details were assessed with multivariable logistic regression analysis to predict the risk of prolonged ventilation after thymectomy. A nomogram to predict the probability of post-thymectomy ventilation was constructed with R software. Discrimination and calibration were employed to evaluate the performance of the nomogram.

RESULTS

By multivariate analysis, male, low vital capacity (VC), Osserman classification (IIb, III, IV), total intravenous anesthesia, and long operation time were identified as the risk factors and entered into the nomogram. The nomogram showed a robust discrimination, with an area under the receiver operating characteristic curve (AUC) of 0. 835 (95% confidence interval [CI], 0.757-0.913). The calibration plot indicated that the nomogram-predicted probabilities compared very well with the actual probabilities (Hosmer-Lemeshow test: P = 0.921).

CONCLUSION

The nomogram is a valuable predictive tool for prolonged ventilation after thymectomy in patients with TAMG.

Myasthaenia gravis in pregnancy, delivery and newborn

INTRODUCTION

Myasthaenia gravis (MG) is the most common disease of the neuromuscular junction; clinical presentation of the disease includes a variety of symptoms, the most frequent beign the only ocular muscles involvement, to the generalized myasthenic crisis with diaphragmatic impairment and respiratory insufficiency. It is most common in women between 20 ad 40 years.

EVIDENCE ACQUISITION

We performed a comprehensive search of relevant studies from January1990 to Dicember 2019 to ensure all possible studies were captured. A systematic search of Pubmed databases was conducted.

EVIDENCE SYNTHESIS

Pregnancy has an unpredictable and variable effect on the clinical course of MG; however, a stable disease before is likely not to relapse during pregnancy. exacerbations can still occur more often during the first trimester and the post partum period. The transplacental passage of antibodies results in a neonatal transient disease, whereas the major concern is related to foetal malformations such as fetal arthrogryposis and polyhydramnios. The overall neonatal outcome described in literature is variable, perinatal mortality in women with MG is generally the same as non affected patients, although in one study the risk of premature rupture of the membranes was higher. Treatment of MG in pregnangncy includes pyridostigmine and corticosteroids, although the latter have been associated with higher risk of cleft palate, premature rupture of the membranes and preterm delivery. These drugs appear also to be safe in breastfeeding. In MG patients spontaneous vaginal delivery should be encouraged, for surgery could cause acute worsening of myasthenic symptoms; also an accurate anesthesiological evaluation must be performed prior to both general and local anesthesia due to increased risk of complications.

CONCLUSIONS

Most of the myasthenic women could have uneventful pregnancy with good obstetrical outcomes, both for mother and neonate. However, a careful planning of pregnancy and multidisciplinary team approach, composed by neurologists, obstetricians, neonatologists and anesthesiologists, is required to manage these pregnancies.

Myasthenia gravis and pregnancy: retrospective evaluation of 27 pregnancies in a tertiary center and comparison with previous studies

BACKGROUND AND AIM

To share our experience with the management of pregnancies in women with myasthenia gravis (MG) in a tertiary center.

METHODS

The study retrospectively evaluated 27 pregnancies in 12 patients. The pregnancies were divided into 3 groups on the basis of the clinical course of MG during pregnancy: improvement (n = 7), disease-stable (n = 9), and deterioration (n = 11). The groups were compared with respect to patient characteristics, clinical features, and obstetric outcomes.

RESULTS

There were 4 miscarriages (14.8%), 3 preterm births (11.1%), and 4 cases of preterm premature rupture of the membranes (PPROM) (14.8%). Exacerbation was observed in 25.9% of the cases; the remission rate during the postpartum period and after miscarriage was 37%. The cesarean section (CS) rate was 78.3%. Pregnancies with deterioration of MG were statistically more likely to have higher miscarriage, preterm birth, PPROM, CS, and transient neonatal MG rates, in addition to a lower gestational age at birth, birth weight, and 5-min Apgar score than pregnancies with improved or stable disease (p values < 0.001, 0.04, 0.03, 0.009, 0.02, < 0.001, 0.002, and 0.043, respectively).

CONCLUSION

Physicians who manage pregnant women with MG must be familiar with the clinical features of the condition; a multidisciplinary approach is necessary for a better prognosis.

Is the Degree of Sensitivity to Nondepolarizing Muscle Relaxants Related to Requirements for Postoperative Ventilation in Patients with Myasthenia Gravis?

The purpose of this study was to examine whether the degree of sensitivity to nondepolarizing muscle relaxants is related to the requirement for postoperative ventilatory support in patients with myasthenia gravis.

Thirty-six patients with myasthenia gravis undergoing trans-sternal thymectomy were monitored by electromyography in order to assess the neuromuscular response to vecuronium. After calibration to 100% of baseline electromyographic response values using an EMG monitor, incremental doses of 5, 10 and 20 μg/kg of vecuronium were administrated to produce 95% neuromuscular blockade and to obtain a cumulative dose-response curve for each patient. A univariable logistic regression with odds ratio was used to examine the predictive variables of prolonged postoperative ventilation. Depending on their postoperative ventilatory needs, patients were divided into an early extubation group and a prolonged ventilatory group.

There were no significant differences between the two groups in terms of vecuronium ED95 (prolonged ventilation group: 23.2±18 μg/kg; early extubation group: 23.2±18 μg/kg, P=0.129) and vecuronium requirement to maintain less than 25% neuromuscular blockade (prolonged ventilation group: 2.4±1.7 mg/kg; early extubation group: 3.8±4.5 mg/kg, P=0.249). There were, however, significant differences in the incidence of a history of previous respiratory crises and the presence of bulbar palsy between the early extubation and prolonged ventilation groups. History of previous respiratory crisis (odds ratio (OR), 3.5; 95% confidence interval (CI), 1.0-13; P=0.03) and presence of bulbar palsy (OR, 3.7; 95%CI, 0.9-15; P=0.049) were associated with the need for prolonged postoperative ventilation. However, we failed to demonstrate that the degree of sensitivity to nondepolarizing muscle relaxants was related to an increased requirement for postoperative ventilation in patients with myasthenia gravis.

[Video-assisted thoracoscopic thymectomy in myasthenia gravis. New approach]

AIM

To present possibility and technical aspects of anesthetic management during video-assisted thoracoscopic thymectomy in patients with myasthenia gravis.

MATERIAL AND METHODS

The article describes the proposed modified anesthetic method that is suitable for video-assisted thoracoscopic thymectomy in patients with myasthenia gravis. Nine patients with myasthenia underwent VATS-thymectomy. Anesthesia was performed with artificial airway and auxiliary ventilation without muscle relaxants administration.

Thymectomy in myasthenia gravis: proposal for a predictive score of postoperative myasthenic crisis

OBJECTIVES

Thymectomy plays an important role in patients with myasthenia gravis (MG). This study aimed to explore predictors of postoperative myasthenic crisis (POMC) after thymectomy and to define a predictive score of respiratory failure.

METHODS

The clinical data of 177 patients with MG undergoing thymectomy from January 1995 to December 2011 were retrospectively reviewed. The following factors were analysed in relation to the occurrence of myasthenic crisis: gender, age, body mass index (BMI), anti-acetylcholine receptor-antibody level, bulbar symptoms, comorbidities, duration of symptoms, Osserman-stage, Myasthenia Gravis Foundation of America (MGFA) stage, history of myasthenic crisis, use of immoglobulins or plasmapheresis, kind of therapy, spirometric and blood gas parameters, histology, kind of surgery, non-myasthenic complications and duration of intubation.

RESULTS

Twenty-two patients experienced postoperative respiratory failure after thymectomy. Univariate analysis revealed a correlation with age >60 years (odds ratio (OR) = 1.79, 95% confidence interval (CI) = 1.04-6.78; P = 0.040); Osserman-stage (IIB- OR = 5.16, 95% CI = 1.10-24.18; P = 0.037, III-IV- OR = 8.75, 95% CI = 1.53-50.05; P = 0.015); bulbar symptoms (OR = 7.42, 95% CI = 1.67-32.84; P = 0.008); BMI >28 (OR = 3.99, 95% CI = 1.58-10.03; P = 0.003); preoperative plasmapheresis (OR = 2.97, 95% CI = 1.18-14.04; P = 0.021); duration of symptoms >2 years (OR = 4.00, 95% CI = 1.09-14.762; P = 0.036); extended surgery (OR = 2.52, 95% CI = 1.02-6.22; P = 0.045); lung (OR = 4.05, 95% CI = 1.44-11.42; P = 0.008), pericardial (OR = 3.78, 95% CI = 1.45-9.82; P = 0.006) or pleural resection (OR = 3.23, 95% CI = 1.30-8.03; P = 0.012); Vital Capacity % <80% (OR = 0.20, 95% CI = 0.05-0.82; P = 0.025) and PaCO2 >40 mmHg (OR = 3.76, 95% CI = 1.12-12.68; P = 0.032). Multivariate logistic regression analysis showed that Osserman-stage (IIB- OR = 5.69, 95% CI = 1.09-29.69; P = 0.039 (III-IV- OR = 11.33, 95% CI = 1.67-76.72; P = 0.013), BMI >28 (OR = 3.65, 95% CI = 1.10-12.15; P = 0.035), history of myasthenic crisis (OR = 24.10, 95% CI = 2.34-248.04; P = 0.007), duration of symptoms >2 years (OR = 5.94, 95% CI = 1.12-31.48; P = 0.036) and lung resection (OR = 8.48, 95% CI = 2.18-32.97; P = 0.002) independently predict POMC. Excluding history of preoperative myasthenic crisis (statistically associated with Osserman-stage), we built a scoring system according to the OR of Osserman-stage (I-IIA, IIB, III-IV), BMI (<28, ≥ 28), duration of symptoms (<1, 1-2, >2 years) and association with a pulmonary resection. This model helped in creating four classes with increasing risk of respiratory failure (Group I, 6%; Group II, 10%; Group III, 25%; Group IV, 50%).

CONCLUSIONS

Our model facilitates the stratification of patient risk and prediction of the occurrence of POMC. Moreover, it could help to guide the anaesthesiologist's decision on the duration of intubation. Further studies based on larger series are needed to confirm these preliminary data.

Low-dose spinal anesthesia for urgent laparotomy in severe myasthenia gravis

Myasthenia gravis (MG) is an autoimmune disease with an incidence of 2-10/100,000 cases per year, characterized by muscle weakness secondary to destruction of postsynaptic acetylcholine receptors. In these patients, important perioperative issues remain unresolved, namely, optimal administration of cholinesterase inhibitors, risks of regional anesthesia, and prediction of need of postoperative mechanical ventilation. We describe the use of a low-dose spinal anesthesia in a patient with MG who was submitted for emergence exploratory laparotomy. The utilization of low-dose spinal anesthesia allowed us to perform surgery with no adverse respiratory or cardiovascular events in this patient.

Thymoma removal in a cat with acquired myasthenia gravis: a case report and literature review of anesthetic techniques

HISTORY AND PRESENTATION: A 12 year old, 4.2 kg, domestic long hair, castrated male cat was presented with regurgitation, inability to retract the claws, general weakness, cervical ventroflexion and weight loss. A thymic mass was evident on radiographs. Acetylcholine receptor antibody titer was positive for acquired myasthenia gravis (MG). Thymectomy via midline sternotomy was scheduled. ANESTHETIC MANAGEMENT:  Oxymorphone and atropine were administered subcutaneously as premedication, and anesthesia was induced with etomidate and diazepam given intravenously to effect. The cat's trachea was intubated and anesthesia was maintained with isoflurane in oxygen, and continuous infusions of remifentanil and ketamine. Epidural analgesia with preservative-free morphine was administered prior to surgery. Postoperative analgesia was provided by oxymorphone subcutaneously, interpleural bupivacaine, and fentanyl infusion. Postoperative complications included airway obstruction, hypoxemia and hypercapnia.

FOLLOW-UP

The cat was discharged 3 days after surgery. Discharge medications included pyridostigmine and prednisone. Nine days after surgery, the cat had a significant increase in its activity level, and medications were discontinued. Histopathologically, the mass was consistent with a thymoma. Approximately 6 weeks later the cat became weak again and pyridostigmine and prednisone administration was resumed.

CONCLUSION

The perioperative management of patients with MG for transsternal thymectomy is a complex task. The increased potential for respiratory compromise requires the anesthesiologist to be familiar with the underlying disease state, and the interaction of anesthetic and non-anesthetic drugs with MG. Careful monitoring of ventilation and oxygenation is indicated postoperatively.

Anesthetic management of direct laryngoscopy and dilatation of subglottic stenosis in a patient with severe myasthenia gravis

We describe the anesthetic management of a patient with severe myasthenia gravis and tracheal stenosis; the patient was scheduled for direct laryngoscopy and dilatation. The combination of myasthenia gravis and tracheal obstruction presents several difficulties for anesthetic management. The airway is shared; therefore, any complications are also shared by the anesthesiologist and bronchoscopists. The potential for respiratory compromise in patients undergoing the two procedures requires that anesthesiologists be familiar with the underlying disease state, as well as the interaction of anesthetic and nonanesthetic drugs in a case involving myasthenia gravis. We reviewed the literature and report our experience in this case. There is no strong evidence for choosing one approach to general anesthesia over another for bronchoscopy. Careful preoperative planning and experience in airway management and jet ventilation are crucial to prevent an adverse outcome and obtain favorable results.

A standardized protocol for the perioperative management of myasthenia gravis patients. Experience with 110 patients

BACKGROUND

Video-assisted thoracoscopic extended thymectomy (VATET) is well established in the treatment of myasthenia gravis; however, patient selection remains controversial. Perioperative management protocol is lacking, and concerns regarding post-operative myasthenic crisis still remain. We performed a retrospective observational study evaluating the impact of the introduction of a protocol in the perioperative management of patients with myasthenia gravis who underwent VATET.

METHODS

The perioperative management protocol was developed by a team of neurologists and anesthesiologists who reviewed the literature and their previous experience on myasthenia gravis patients. Respiratory, clinical, and neurological patient features were included in the protocol evaluation. A retrospective review of patients who underwent VATET before and after introduction to the protocol was finally performed.

RESULTS

The medical records of 66 patients (pre-protocol group) and 44 patients (protocol group) were available for the study. In the pre-protocol group, 17 patients (26%) were admitted to intensive care unit (ICU) during the post-operative period, while three patients (6.8%) of the protocol group met the criteria for ICU post-operative admission. This resulted in a reduction of 73.5% of patients admitted to ICU (P = 0.023) and in an 80% (P = 0.002) reduction of the use neuromuscular blocking agents. Two post-operative myasthenic crises preceded by bulbar symptoms (1.8%) were identified in the pre-protocol group patients.

CONCLUSIONS

Although the application of our protocol results in a substantial reduction in the recovery of patients in the ICU and in hospital costs, there was no substantial difference in mortality and morbidity between patients admitted to the surgical ward or to ICU.

Myasthenia gravis: two case reports and review of the literature

BACKGROUND AND OBJECTIVES

Myasthenia gravis (MG) is an autoimmune neurologic disease that affects the postsynaptic portion of the neuromuscular junction. It represents a challenge for anesthesiologists due to the diversity of disease manifestations and possibility of postoperative respiratory complications. The objective of this study was to demonstrate the importance of adequate monitoring of the neuromuscular blockade (NMB) due to the multiple presentations of MG.

CONTENTS

In this paper we report two cases of patients with MG. The first patient presented with the classical sensitivity to the neuromuscular blocker (NMB) and the second had a similar response to that of a normal patient. The literature review will be restricted to disease characteristics, while the description of its pathophysiology will focus on its reactions to NMB.

CONCLUSIONS

We suggest that, due to the multiple presentation and treatment of MG, neuromuscular transmission monitors are fundamental when using NMB.

Anesthesia for patients undergoing transsternal thymectomy for juvenile myasthenia gravis

Background:

Juvenile myasthenia gravis (JMG) is the rare form of myasthenia gravis presenting in childhood and adolescence. When medical management fails, thymectomy is offered for these patients. Complete resection of the thymus is best achieved through transsternal thymectomy. Anesthetic management of patients with JMG is challenging, particularly in regards to the goals of postoperative pain control, respiratory function, and extubation.

Methods:

We retrospectively reviewed the medical records of 13 patients, ranging in age from 6 to 22 years, who underwent transsternal thymectomy for JMG. Information on patient demographics, characteristics of their disease and treatment, anesthetic management, and postoperative course were collected.

Results:

All patients had undergone multiple treatment modalities and presented for surgery because of inadequate symptom control with medical management. As expected for a pediatric population, anesthesia induction was age dependent. 40% of the patients underwent an inhalation induction and 60% underwent an intravenous induction. Anesthesia was maintained with a low-dose inhalation agent in all patients, supplemented in 84% of patients with a remifentanil infusion, and in 69% of patients with an epidural infusion. Muscle relaxants were avoided in all patients. With this regimen, 92% of patients could be extubated successfully in the operating room.

Conclusion:

We found that avoidance of muscle relaxants and use of remifentanil with a low-dose hypnotic agent provided a stable intraoperative course, facilitated rapid emergence, and allowed early extubation in patients with JMG undergoing transsternal thymectomy. Epidural analgesia reduced the need for intra- and postoperative intravenous opioids and did not have an adverse effect on respiratory strength.

Myasthenia gravis and pregnancy: anaesthetic management--a series of cases

BACKGROUND AND OBJECTIVE

Myasthenia gravis is an autoimmune neuromuscular disease, usually affecting women in the second and third decades. The course is unpredictable during pregnancy and puerperium. Myasthenia gravis can cause major interference in labour and partum and exacerbations of the disease frequently occur. The aim of this series of cases is to analyse retrospectively the anaesthetic management of myasthenia gravis patients and complications during the peripartum period.

MATERIALS AND METHODS

Retrospective, single centre study from clinical files of female myasthenia gravis patients who delivered between 1985 and 2007 at Hospital de Santo António, Porto, Portugal.

RESULTS

Seventeen myasthenia gravis patients delivered between 1985 and 2007 in Hospital Santo António. Two women were not included in the study as they had a spontaneous abortion in the first trimester. Four patients presented exacerbations of the disease during pregnancy, no exacerbation occurred in eight patients and three patients presented their first symptoms of myasthenia gravis during pregnancy (without diagnosis at time of delivery). Concerning the eight patients without exacerbations of the disease during pregnancy, pregnancy was brought to term in 87.5% of the cases; five women were submitted to nonurgent caesarean section (62.5%); and epidural block was performed in six patients (75%). No complications related to anaesthesia occurred in the peripartum period. Concerning the four patients with exacerbations of the disease, pregnancy was brought to term in three cases (75%); three women were submitted to nonurgent caesarean section (75%); and epidural block was performed in three patients (75%). One patient underwent an uncomplicated thymectomy under general anaesthesia during pregnancy and, in the postpartum period, there was a myasthenic crisis in another patient. Concerning the three patients without a myasthenia gravis diagnosis at partum, one woman already being followed for presenting muscular weakness had a vaginal delivery under epidural block, without complications; another patient, presenting discrete supine dyspnoea, was submitted to elective caesarean section under spinal block and developed severe dyspnoea that required mechanical ventilation and ICU admission; and in the remaining case, a woman presenting mild blurred vision was submitted to general anaesthesia, which resulted in delayed emergence, muscular weakness and respiratory failure. Pregnancy went full term in all cases (100%). No newborn had a myasthenic crisis.

CONCLUSION

Myasthenia gravis can interfere slightly with pregnancy and partum, although exacerbations of the disease occur frequently. Strict surveillance and therapeutic optimisation are crucial. In women with controlled disease, caesarean section should be carried out only if there are obstetric reasons. Locoregional anaesthesia is preferred, mainly epidural block. A good multidisciplinary cooperation, specific precautions and surveillance can certainly contribute to an improved outcome in myasthenia gravis patients during the peripartum period.

The use of desflurane or propofol in combination with remifentanil in myasthenic patients undergoing a video-assisted thoracoscopic-extended thymectomy

BACKGROUND

Although several studies of the use of desflurane in anesthesia have revealed many desirable qualities, there are no data on the use and effects especially on the neuromuscular function of desflurane on myasthenia gravis (MG) patients. The purpose of this study was to evaluate the use of either desflurane or propofol, both combined with remifentanil, in patients with MG undergoing a video-assisted thoracoscopic-extended thymectomy (VATET).

METHODS

Thirty-six MG patients who underwent VATET were enrolled. Nineteen patients were anesthetized with remifentanil and propofol infused with a target-controlled infusion plasma model, and 17 patients with desflurane and remifentanil. No muscle relaxant was used. The intubating conditions, hemodynamic and respiratory changes, neuromuscular transmission and post-operative complications were evaluated.

RESULTS

Neuromuscular transmission was significantly decreased in the desflurane group (6.7%, from 3% to 9% during anesthesia P=or<0.05). The intubating conditions were good in all 36 patients and 35 patients were successfully extubated in the operating room. The time-to-awakening, post-operatory pH and base excess were significantly different in the two groups, with a decreasing mean arterial pressure in the group administered with desflurane. No patients required reintubation due to myasthenic or cholinergic crisis, or respiratory failure. No other significant differences between the two groups studied were observed.

CONCLUSION

Our experience indicates that anesthesia with desflurane plus remifentanil in patients with MG could determine a reversible muscle relaxation effect, but with no clinical implication, allowing a faster recovery with no difference in extubation time and post-operative complications in the two groups.

Laryngeal Mask Airway insertion with total intravenous anesthesia for transsternal thymectomy in patients with myasthenia gravis: report of 5 cases

Myasthenia gravis is a chronic autoimmune disease characterized by a reduction of postsynaptic nicotinic acetylcholine receptors at the neuromuscular junction. Most myasthenia gravis patients require thymectomy. Intravenous (IV) anesthetics may be superior to inhalation agents in these patients. The Laryngeal Mask Airway (LMA), when compared with the endotracheal tube, causes less airway resistance, which in turn may lead to a decreased bronchoconstrictive reflex, less atelectasis, and fewer pulmonary infections. We report 5 patients with myasthenia gravis, who underwent transsternal thymectomy with total IV anesthesia and LMA.

Propofol or sevoflurane anesthesia without muscle relaxants allow the early extubation of myasthenic patients

PURPOSE

To compare two non-muscle relaxant anesthetic techniques in myasthenic patients undergoing trans-sternal thymectomy, evaluating the intra- and postoperative conditions including the early extubation in the operating room.

METHODS

Sixty-eight consecutive myasthenic patients undergoing trans-sternal thymectomy were prospectively randomized in two groups: propofol and sevoflurane. In both groups anesthesia was induced with propofol (1-2 mg x kg(-1)) and intubation performed after topical anesthesia of the airway with lidocaine. Anesthesia was maintained in the propofol group (36 patients) with a continuous propofol infusion (3-6 mg x kg(-1) x hr(-1)) and nitrous oxide and, in the sevoflurane group (32 patients), with sevoflurane (end-tidal 1-1.5%) in O2:N2O. Intubating conditions, hemodynamic changes, neuromuscular transmission, postoperative intensive care unit and hospital length of stay and complications were evaluated. Data were analyzed with repeated measure two-way analysis of variance (ANOVA), Chi square test and Student's t test.

RESULTS

Intubating conditions were good in all patients. There were no hemodynamic changes. All patients were extubated in the operating room and none had to be re-intubated for postoperative respiratory depression. Neuromuscular transmission showed minimal changes, more important in the sevoflurane group, and at the end of the procedure the recovery was complete in all patients. We did not observe any other significant differences between the two groups studied.

CONCLUSION

Our data show that these two anesthetic techniques allow the early extubation of myasthenic patients in the operating room.

The ProSeal laryngeal mask in myasthenia gravis

This case describes the anaesthesia management of a patient with myasthenia gravis who required mastectomy with axillary lymph node clearance. After withholding medical therapy for the myasthenia preoperatively on the day of surgery, anaesthesia was maintained with halothane, nitrous oxide and a remifentanil infusion. Muscle relaxants were avoided, facilitated by the use of a ProSeal (Intravent, Orthofix, Maidenhead, United Kingdom) laryngeal mask airway for positive pressure ventilation. The ProSeal laryngeal mask airway is a new laryngeal mask device with a modified cuff and a drainage tube which has been shown to have advantages over older designs for use during positive pressure ventilation. The rationale for the management of this patient with myasthenia is discussed.

Decade-long experience with surgical therapy of myasthenia gravis: early complications of 324 transsternal thymectomies

BACKGROUND

We studied the incidences and evaluated the management of early postoperative complications after thymectomy for myasthenia gravis.

METHODS

During the period between 1987 and 1996, 324 thymectomies were performed through median sternotomy access under general anesthesia. Postoperative management was administered according to a standardized protocol of anticholinesterase medication, which was withdrawn for the 48 hours of obligatory postoperative mechanical ventilation. The mean age of patients was 34 years (range, 8 to 71 years).

RESULTS

One hundred forty-nine patients made an uneventful recovery; 104 patients had only minor complications, whereas 71 patients had major complications. The mortality rate was 0.6% (2 patients). The major surgical complications were recorded as sternal bleeding (1 patient) and sternal disruption (1 patient). The major general complications were recorded as tracheal stenosis (1 patient), pneumonia (3 patients), heart failure (1 patient), gastric hemorrhage (1 patient), and respiratory insufficiency (71 patients). Forty-six reintubations were performed on 40 patients and 19 tracheostomies (6%) were performed postoperatively.

CONCLUSIONS

The excessive incidence of respiratory insufficiency and airway-associated morbidity was potentially related, at least partially, to prolonged mechanical ventilation and withdrawal of anticholinesterase medication. Earlier weaning of patients with revision of 48-hour withdrawal of anticholinesterase medication is necessary.

Perioperative medical management and outcome following thymectomy for myasthenia gravis

PURPOSE

To describe the evolution of the perioperative management of myasthenia gravis (MG) patients undergoing thymectomy and to question the need for systematic postoperative ventilation.

CLINICAL FEATURES

We collected data retrospectively from 36 consecutive MG patients who underwent thymectomy over a 21-yr period, via transthoracic, -cervical or -sternal incisions (n=5, n=7, n=24, respectively). From 1980 to 1993, a balanced anesthetic technique (n=24) included various inhalational agents with opiates and myorelaxants (in eight cases); 22 patients were admitted to the intensive care unit (ICU). Since 1994, i.v. propofol was combined with epidural bupivacaine and sufentanil (n=12); all patients were admitted to the postanesthesia care unit. Short-term postoperative ventilation (median time four hours, range from three to 48 hr) was required in eight patients who had longer hospital stay (median stay=12 days, range (8-28) vs five days (4-15) for patients with early extubation, P <0.05) but similar clinical improvement six months after thymectomy. Postoperative ventilatory support was required more frequently when a balanced anesthetic technique was used (odds ratio=4.2 (1.1-9.7), P=0.03) and particularly when myorelaxants were given (odds ratio=13.9 (2.1-89.8), P=0.009). Leventhal's scoring system had low sensitivity (22.2%) and positive predictive values (25%).

CONCLUSIONS

Our data show that the severity of MG failed to predict the need for postoperative ventilation. A combined anesthetic technique was a safe and cost-effective alternative to balanced anesthesia as it provided optimal operating conditions and resulted in fewer admissions in ICU and shorter hospital stays.

Transcervical thymectomy

Transcervical thymectomy is appropriate for managing carefully selected patients with myasthenia gravis due to its noninvasive nature, good cosmetic results, and favorable long-term outcomes. Contraindications to its use include the presence of a thymoma and advanced age. In optimally prepared patients, the operative complication rate is negligible and the average length of hospital stay is 1 to 2 days. The ultimate results of therapy often are not evident for several years postoperatively, indicating that comprehensive preoperative and postoperative treatment by a qualified neurologist is essential in optimizing outcomes. A meta-analysis of long-term results shows that 90% of patients who undergo the operation are improved, 80% become asymptomatic, and 50% achieve a complete remission.

Neuromuscular disorders

Neuromuscular diseases form an heterogeneous group of illnesses. These diseases are rare and studies concerning their anaesthetic management are difficult. Patients with neuromuscular disease represent a challenge for the anaesthesiologist because of the frequent perioperative complications. Cardiac and respiratory functions are often involved, and the severity of the lesions are difficult to estimate. The possible interactions of different drugs necessitates a good knowledge of the drugs' actions and pathophysiological mechanisms.

Thymectomy for myasthenia gravis

The pathophysiological role of the thymus in myasthenia gravis, and the mechanism of therapeutic effect of thymectomy, are incompletely understood. Nevertheless, thymectomy is a valuable treatment modality in selected patients with generalised myasthenia gravis. There are several types of thymectomy operation, but no one operative approach is clearly superior to the others. Total removal of the thymus gland is essential. Additional excision of associated mediastinal and cervical tissue, that may harbor ectopic thymic rests, is a controversial surgical issue. Surgeons that advocate thymectomy through small, cosmetically favourable, incisions usually believe that simple removal of the thymus gland is an adequate operation. Surgeons that emphasise the importance of removing extrathymic tissue, in addition to the thymus gland, usually favour greater operative exposure through a median sternotomy. To minimise operative morbidity, surgery for myasthenia gravis requires a multidisciplinary (neurology, surgery, anaesthesia) approach to peri-operative care.