|Year : 2012 | Volume
| Issue : 1 | Page : 34-37
Caesarean section in a patient with Myasthenia Gravis: A bigger challenge for the anesthesiologist than the obstetrician
Manoj K Sanwal, Neha Baduni, Aruna Jain
Department of Anaesthesia and Intensive Care, Lady Hardinge Medical College, New Delhi, India
|Date of Web Publication||4-Aug-2012|
GH-12/183, Paschim Vihar, New Delhi-110087
Source of Support: None, Conflict of Interest: None
Myasthenia Gravis (MG) is an acquired, autoimmune disorder affecting neuromuscular junction presenting with easy fatigability, progressive weakness, diplopia, difficulty in speaking and swallowing and even ventilatory failure in severe cases. During pregnancy the disease may go into remission or may exacerbate at any time during first, second and third trimesters or postpartum period. We are reporting the case of a 28 year old primigravida, known case of MG, who underwent caesarean section and developed muscular weakness on third postoperative day. Her neonate also had tachypnoea and hypotonia, Both, the mother and the baby were managed aggressively and responded well to therapy.
Keywords: Myasthenia gravis, pregnancy, thymectomy, plasmapharesis, pyridostigmine
|How to cite this article:|
Sanwal MK, Baduni N, Jain A. Caesarean section in a patient with Myasthenia Gravis: A bigger challenge for the anesthesiologist than the obstetrician. J Obstet Anaesth Crit Care 2012;2:34-7
|How to cite this URL:|
Sanwal MK, Baduni N, Jain A. Caesarean section in a patient with Myasthenia Gravis: A bigger challenge for the anesthesiologist than the obstetrician. J Obstet Anaesth Crit Care [serial online] 2012 [cited 2021 May 16];2:34-7. Available from: https://www.joacc.com/text.asp?2012/2/1/34/99317
| Introduction|| |
Myasthenia gravis (MG) is an acquired, autoimmune disorder affecting the neuromuscular junction presenting with easy fatigability, progressive weakness, diplopia, difficulty in speaking and swallowing and even ventilatory failure in severe cases. During pregnancy, the disease may go into remission or may exacerbate at any time during first, second, and third trimesters or postpartum period. Although plenty of literature is available regarding the anesthetic management of such patients undergoing thymectomy, clear cut guidelines for those undergoing labor and caesarean delivery are still lacking.
| Case Report|| |
A 28-year-old primigravida, a diagnosed case of MG for 7 years, reported to the antenatal clinic of our hospital. The diagnosis was established after detection of antibodies directed against acetylcholine (Ach) receptor in patient's serum using radioimmunoassay. Single fiber electromyography and edrophonium test were also positive for the disease. She was started on oral pyridostigmine and prednisolone.
Three years after diagnosis, she had an aggravation of her disease with ventilatory failure requiring mechanical ventilation. Thymectomy under general anesthesia was done at that time. The perioperative course was uneventful. She was on the same drug treatment till the time she conceived and presented to our hospital for antenatal care at 28 weeks of gestation.
MG ran a stable course during the antenatal period. She was well controlled on oral pyridostigmine 60 mg three times daily and prednisolone 10 mg per day. She developed pregnancy-induced hypertension (PIH) at 30 weeks and methyldopa 2000 mg per day in four divided doses was started. Clinical examination and laboratory parameters including thyroid function tests and ECG were within normal limits. In view of PIH induction of labor was done labor at 40 weeks of gestation. However, in view of the meconium staining of liquor, an emergency caesarean section (CS) was scheduled.
After steroid supplementation with hydrocortisone 100 mg i.v. and preloading with 1000 mL of lactated Ringer's solution, a subarachnoid block was instituted with 2.0 mL of 0.5% hyperbaric bupivacaine and 25 μg fentanyl in L3-L4 interspace using 25G Quinke type spinal needle. Her hemodynamic and respiratory parameters remained stable throughout the surgery. A 2.75 kg healthy female baby was delivered who cried immediately after birth, Apgar score being 8, 9, 9 at 0, 1, 5 min. After giving a bolus of 5U of oxytocin, an infusion was started. The newborn was shifted to neonatal ICU for observation. The mother was monitored in the post-operative period for respiration, swallowing and speech to detect any evidence of skeletal muscle weakness. Neostigmine 0.75 mg was given intramuscularly 4 h after the surgery with a shift to oral pyridostigmine and prednisolone after reappearance of bowel sounds. Postoperative analgesia was achieved with intramuscular diclofenac. On third post operative day, she complained of generalized weakness of neck and limbs, difficulty in getting up from bed, ptosis, diplopia, dysarthria, and dyspnea. On examination, pupils were found to be constricted. Arterial blood gas analysis showed P a O 2 and P a CO 2 of 98 mm Hg and 48 mmHg respectively with mild hypokalemia (K = 3.2 meq/L). Oxygen and potassium supplementations were done and the dose of pyridostigmine was increased to 120 mg three times a day. She responded well to the treatment with her weakness improving over a few hours and was shifted out of ICU after 5 days.
In the neonatal ICU, the baby developed tachypnea and hypotonia with poor sucking and swallowing on second day of her life. ABG showed a P a O 2 of 65 mmHg and P a CO 2 of 38 mmHg on room air. Regular oral suctioning and oxygen supplementation were sufficient to stabilize the condition and she recovered completely over next 10 days.
| Discussion|| |
MG is most common disorder affecting the neuro-muscular junction.  It can present at any age but has bimodal peak of incidence. The first peak is seen in females in third decade of life while second peak occurs in sixth decade mainly in males. The etiopathogenesis is characterized by the presence of anti-Ach receptor antibodies in the serum of 85% patients of generalized MG and 50-60% patients of ocular MG. Seronegative patients have anti-muscle-specific kinase (MUSK) antibodies in 10-20% cases. There is antibody-mediated destruction of Ach receptors present on the post-synaptic membrane with loss of folds and widening of a synaptic cleft. 
Abnormality of thymus is seen in 75% cases of MG of which 85% have germinal hyperplasia and 15% have tumor of the gland. Thymectomy is indicated for thymoma and is recommended in all young myasthenics who have a deteriorating response to anticholinesterase drug. , Thymectomy is more beneficial if done prior to pregnancy as was the case with our patient. , Case reports are present when thymectomy was beneficial even when done during pregnancy. 
MG runs a variable and unpredictable course during pregnancy with one-third patients improving, one-third deteriorating, and one-third remaining the same during the period of pregnancy.  The worsening of symptoms has been reported to occur in first trimester by some, , in second trimester by a few,  while others have reported it in third trimester. , Our patient had disease exacerbation in the early postpartum period resembling the observations of Plauche  and Mier et al.  It is recommended that anticholinesterase therapy be continued orally throughout the period of pregnancy. However, erratic gastric absorption during labor may necessitate a shift to equivalent intramuscular dosages. Steroids, though safe during pregnancy, should be reduced to minimum effective dose. Other modalities like plasmapheresis and azthioprine can be used in case of an acute exacerbation.  Magnesium sulfate therapy, if needed due to development of PIH, is contraindicated in myasthenics as magnesium may itself produce neuro-muscular block by inhibiting release of Ach from the pre-junctional membrane. Although the incidence of obstetric complications and surgical delivery are higher in myasthenic patients, it is not an indication for caesarean section and vaginal delivery is preferred.  In our case, vaginal delivery was planned by the obstetrician, as the disease was well controlled, but had to be taken up for surgical delivery due to fetal indication.
The neonate born to this myasthenic mother experienced a transient myasthenic syndrome presenting as weak cry, difficulty in sucking and swallowing, and respiratory weakness. Papazian  reported 21% incidence of this syndrome, out of which 67% developed it within few hours of birth. Response to oral anticholinesterase is good and complete recovery occurs in less than 2 months. The atypical form may present as arthrogryposis multiplex congenita. In our case, the baby developed weakness on second day of life but neither mechanical ventilation nor anticholinesterase therapy was needed with the baby responding only to regular oral suctioning and oxygen supplementation.
It is important for the anesthesiologist to assess the extent of respiratory or bulbar involvement and determine frequency and severity of myasthenic attacks. The type and dosage of anticholinesterase drug and other medications should be noted and readjusted to obtain optimal symptomatic relief before labor. In severe disease, pulmonary function tests and ECG should be considered. Thyroid function tests may be undertaken as high incidence of autoimmune thyroid disorders are associated with this condition.
Use of labor analgesia is highly desirable to prevent fatigue and exhaustion associated with expulsive efforts during second stage of labor. Opioids are a poor choice for this due to risk of excessive depression especially if bulbar or respiratory involvement is present. Central neuraxial blockade has been used and recommended by many clinicians for vaginal delivery. ,, In our case, labor analgesia was not used as it is not a routine practice in our hospital due to shortage of staff. We were informed about the patient only after she was decided to be taken up for CS due to fetal indication.
Both regional and general anesthetics have been described by various workers for caesarean delivery in myasthenics. Regional anesthesia is the better choice in ocular and well-controlled generalized disease.  Central neuraxial blockade in the form of spinal is preferable over epidural as systemic absorption of the greater quantity of local anesthetic needed in epidural block can itself result in muscle weakness, at least theoretically.  Use of amide local anesthetics (LA) which do not require pseudocholinesterase for metabolism appears to be the logical choice. Irrespective of the route, it is essential to limit the upper level of block by using lower doses of local anesthetic along with opioids in spinal and graded doses of LA in epidural anesthesia. Use of the combined spinal and epidural technique is also not without limitations. The advantage of smaller dose of LA into subarachnoid space can be offset by the failure of epidural block as the catheter remains untested in CSE.  Therefore, we employed subarachnoid block in our patient using 2.0 mL of 0.5% bupivacaine along with 25 μg fentanyl without any problem. Moreover, spinal block takes considerably lesser time than CSE and was thus better suited to the indication of fetal distress.
In severe disease with bulbar involvement, general anesthesia with endotracheal intubation is mandatory due to the risk of aspiration. Schnider et al. recommended rapid sequence induction with immediate endotracheal intubation. In severely compromised patients, thiopentone alone may be used as sole anesthetic agent. Depolarizing neuromuscular blockers are better avoided as resistance to their action is present. MG patients are exquisitely sensitively to the action of non-depolarizing agents. One-tenth to one-fifth, the calculated dose is sufficient to cause complete muscle paralysis. This sensitivity is seen in both seropositive and seronegative patients,  is more in generalized than ocular disease  and remains even in patients of cured MG (i.e., thymectomised patients who are symptom-free without any medication).  Use of inhalational agents should be cut down to minimum as they aggravate muscle weakness. Only low doses of short acting opioids are recommended to provide analgesia after delivery of baby. After the end of surgery, reversal should be achieved using incremental doses of neostigmine (0.5 mg) intravenously with the response monitored with a nerve stimulator. Overenthusiastic efforts at reversal may precipitate a cholinergic crisis. In severe disease, postoperative ventilation might have to be considered.
In the post-operative period, anticholinesterase therapy should be restarted via intramuscular route or intravenous route. Shift to oral route is made once bowel sounds return. These patients can develop complications in the form of myasthenic crisis or cholinergic crisis at any time during pregnancy, labor or post partum period.  Post partum exacerbation of myasthenic weakness is especially common.  Hence, the patient should be nursed in ICU/HDU with constant watch for any clinical evidence suggesting muscular weakness. As shown in [Table 1], pupillary size is the only clinical criterion by which one can differentiate between the two conditions. The treatment for both the conditions is ventilatory support along with atropine in case of cholinergic crisis and neostigmine in myasthenic crisis.
To conclude, anesthesiologist has an important role not only in the anesthetic management of a pregnant myasthenic undergoing cesarean section but also in management of myasthenic crisis which may be precipitated at any time, especially during the immediate postpartum period. The anesthetic technique of choice is central neuraxial block in well-controlled disease and general anesthesia in severe disease. The significance of postoperative monitoring of skeletal muscle power cannot be overemphasized.
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