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Anesth Analg 2004;98:68-69
© 2004 International Anesthesia Research Society

PEDIATRIC ANESTHESIA

Pyloromyotomy in a Patient with Paramyotonia Congenita

Binnaz Ay, MD*, Arzu Gerçek, MD*, Varlik I. Dogan, MD*, Gürsu Kiyan, MD{dagger}, and Yilmaz F. Gögüs, MD*

Departments of *Anesthesiology and Reanimation and {dagger}Pediatric Surgery, Marmara University Medical School, Istanbul, Turkey

Address correspondence and reprint requests to Dr. Arzu Gerçek, Yaliboyu c. Emanet s. Emek ap. No: 2/28 Bostanci 81110 Istanbul, Turkey. Address e-mail to agercek{at}hotmail.com


   Abstract
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 Abstract
Introduction
 Case Report
 Discussion
 References
 
A 2-mo-old infant with paramyotonia congenita was scheduled for pyloromyotomy and repair of inguinal hernia. Diagnosis of paramyotonia congenita was done with positive family history, myotonia at eyelids, provocation by cold, and electromyogram analysis. Anesthesia was induced via face mask with sevoflurane at 4 minimum alveolar anesthetic concentration in oxygen. Tracheal intubation was attempted without a neuromuscular relaxant. Anesthesia was maintained with sevoflurane at 0.5 minimum alveolar anesthetic concentration in oxygen and remifentanil infusion at a rate of 0.2 µg · kg-1 · min-1. After discontinuation of sevoflurane and remifentanil, the patient was awake and had full recovery of muscle activity.

IMPLICATIONS: The literature concerning general anesthesia in paramyotonic patients is limited. We report a case of paramyotonia congenita in a 2-mo-old male infant undergoing surgery for pyloric stenosis and inguinal hernia after an uneventful anesthesia.


   Introduction
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 Abstract
 Introduction
Case Report
 Discussion
 References
 
Skeletal muscle channelopathies are disorders of muscle fiber membrane excitability and present clinically with varying combinations of periodic paralysis, myotonia, and paramyotonia. Mutations in the skeletal muscle, voltage-gated sodium channel gene are associated with three clinically distinct disorders: paramyotonia, hyperkalemic periodic paralysis, and potassium-aggravated myotonia (1,2). Paramyotonia congenita is characterized by myotonia followed by paresis, usually induced by exposure to cold. The exact place of this disease in the classification of myotonias is not clear but it is probably a subgroup of myotonia congenita or hyperkalemic periodic paralysis. We report a case of paramyotonia congenita in a 2-mo-old male infant undergoing surgery for pyloric stenosis and inguinal hernia.


   Case Report
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 Abstract
 Introduction
 Case Report
Discussion
 References
 
A 2-mo-old male infant with pyloric stenosis was scheduled for pyloromyotomy and repair of inguinal hernia. His parents informed us that their infant suffered from myotonia at the eyelids and hands on exposure to cold lasting 50 min similar to other affected members of the family (Fig. 1). His aunt had had genetic counseling and received a diagnosis of paramyotonia congenita. Electromyelogram (EMG) findings were positive for the other members of the family, but the parents refused EMG analysis for their infant. Diagnosis of paramyotonia congenita was done according to European Federation of Neurological Society guidelines for diagnosis of neurologic disorders with positive family history, myotonia at eyelids, provocation by cold, and EMG analysis (3). The infant’s preoperative laboratory values were normal. Anesthesia was induced via face mask with sevoflurane at 4 minimum alveolar anesthetic concentration (MAC) in oxygen. After establishing and maintaining the end-tidal concentration at 1.3 MAC for 10 min, tracheal intubation was attempted without a neuromuscular relaxant. Anesthesia was maintained with sevoflurane at 0.5 MAC in oxygen and remifentanil infusion at a rate of 0.2 µg · kg-1 · min-1. Lactated Ringer’s solution was infused at a rate of 15 mL · kg-1 · h-1. Heart rate, blood pressure, SpO2, ETCO2, and body temperature were recorded. After discontinuation of sevoflurane and remifentanil, the patient was awake and had full recovery of muscle activity with no signs of paresis and weakness. After an uneventful surgery, he was transferred to the pediatric surgery intensive care unit. On postoperative Day 3, he was discharged home.



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  		Figure 1. Pedigree of the patient’s family.

 

   Discussion
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 Abstract
 Introduction
 Case Report
 Discussion
References
 
Pyloric stenosis together with paramyotonia is challenging. Pyloric stenosis is a medical, not a surgical, emergency because electrolytes and patient’s metabolic status must be corrected before surgical repair. Metabolic alkalosis together with hypochloremia, hyponatremia, and hypokalemia is usually present secondary to vomiting. Genetic analyses of patients with hyperkalemic periodic paralysis, hypokalemic periodic paralysis, and paramyotonia congenita have shown that mutations of a gene at chromosome 17q, encoding the {alpha}-subunit of human skeletal muscle sodium channel (SCN4A), were responsible for the symptoms (2). The original description of paramyotonia congenita was in 1886 by Eulenburg. Paramyotonia congenita is inherited as an autosomal dominant, with large penetrance in males. Symptoms of paramyotonia are present at birth and do not change significantly over a patient’s lifetime. Cold exposure may exacerbate the paramyotonia. The weakness is most severe after exercise and cold exposure. Most patients have myotonia predominantly in the face, neck, and hands (4). In our case, the patient’s preoperative and peroperative plasma electrolytes were within normal limits with a slight metabolic alkalosis. Ringer’s lactate solution without potassium supplements was infused throughout the surgery.

There are few reports of anesthetic care in these patients (5–7). Myotonic patients react unfavorably to many anesthetic drugs and sedatives. The anesthesiologist should be especially vigilant for malignant hyperthermia because it occurs more often in patients with ion-channel disorders (4). Depolarizing muscle relaxants, anticholinesterases, and hypothermia may aggravate the myotonia (6–10). Because the effects of nondepolarizing muscle relaxants in these patients are not known (9), we avoided the use of any muscle relaxants. Epinephrine can induce hypokalemia via ß-2 stimulation, so one should be aware of the potential of epinephrine to induce paralysis and cardiac instability in these patients.

The use of propofol as an induction and maintenance anesthetic in myotonic dystrophy is controversial. Several studies reported the uneventful use of propofol as an induction and maintenance drug in myotonic patients (11,12). But more recent studies indicate that propofol blocks sodium influx current through sodium channels at clinical concentrations, delaying recovery (13,14). When we questioned the parents, they had not experienced malignant hyperthermia during their operations. So we proceeded with anesthesia using a subhypnotic dose of sevoflurane together with maintenance of normothermia.

Regional anesthesia might be considered as an alternative technique for certain operations. Regional anesthesia has been shown to be safe in myotonia (9). Local anesthetic infiltration is not sufficient for pyloric stenosis and a large volume of local anesthetics should be given for caudal anesthesia. Therefore, we preferred to use the ultra-short-acting opioid, remifentanil, as an analgesic.

Body temperature has considerable impact on neurophysiological results. Abnormal findings even in healthy subjects can be caused only by cold extremities. Low surface temperature, for example, may lead to longer distal latencies and slower motor and sensory nerve conduction velocities. Spontaneous activity becomes rare and myotonic discharges become more obvious at low temperature (15).

Because of the marked sensitivity of myotonic patients to sedatives and anesthetics and the increased risk of precipitating generalized myotonia by cold, shivering, and drugs, the safest anesthetic has yet to be established. This case report highlights the need for the avoidance of hypothermia and depolarizing muscle relaxants and a conservative approach to the management of plasma potassium concentration in paramyotonia congenita.


   References
Top
 Abstract
 Introduction
 Case Report
 Discussion
 References
 

  1. Davies NP, Eunson LH, Gregory RP, et al. Clinical, electrophysiologic, and genetic studies in a new family with paramyotonia congenita. J Neurol Neurosurg Psychiatry 2000; 68: 504–7.[Abstract/Free Full Text]
  2. Kim J, Hahn Y, Sohn EH, et al. Phenotypic variation of a Thr704Met mutation in skeletal sodium channel gene in a family with paralysis periodica paramyotonica. J Neurol Neurosurg Psychiatry 2000; 70: 618–21.
  3. Gasser T. EFNS task force on molecular diagnosis of neurologic disorders. EFNS guideline_files FNS guideline.htm.
  4. Gutmann L. Metabolic myopathies. Neurol Clin 2000; 1: 195–202.
  5. Howell PR, Douglas MJ. Lupus anticoagulant, paramyotonia congenita and pregnancy. Can J Anaesth 1992; 39: 992–6.[Web of Science][Medline]
  6. Ashwood EM, Russell WJ, Burrow DD. Hyperkalaemic periodic paralysis and anesthesia. Anaesthesia 1992; 47: 579–84.[Web of Science][Medline]
  7. Streib EW. Hypokalemic paralysis in two patients with paramyotonia congenita and known hyperkalemic/exercise-induced weakness. Muscle Nerve 1989; 12: 936–7.[Web of Science][Medline]
  8. Rosenbaum HK, Miller JD. Malignant hyperthermia and myotonic disorders. Anesthesiol Clin North America 2002; 20: 385–426.
  9. Grace RF, Roach VJ. Caesarean section in a patient with paramyotonia congenita. Anaesth Intensive Care 1999; 27: 534–7.[Web of Science][Medline]
  10. Haeseler G, Stormer M, Mohammadi B, et al. The anesthetic propofol modulates gating in paramyotonia congenita mutant muscle sodium channels. Muscle Nerve 2001; 24: 736–43.[Web of Science][Medline]
  11. Milligan KA. Propofol and dystrophia myotonica. Anaesthesia 1998; 43: 513–4.
  12. White DA, Smyth DG. Continuous infusion of propofol in dystrophia myotonica. Can J Anaesth 1989; 36: 200–3.[Web of Science][Medline]
  13. Rehberg B, Duch DS. Suppression of central nervous system sodium channels by propofol. Anesthesiology 1999; 91: 512–20.[Web of Science][Medline]
  14. Saint DA, Tong Y. Propofol block of cardiac sodium currents in rat isolated myocardial cells is increased at depolarized resting potentials. Clin Exp Pharmacol Physiol 1998; 25: 336–40.[Web of Science][Medline]
  15. Kerling FP, Sokolovska K, Claus D. Effect of temperature on clinical electrophysiology. Fortschr Neurol Psychiatr 1994; 62: 451–7.[Web of Science][Medline]
Accepted for publication August 13, 2003.




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Lippincott, Williams & Wilkins Anesthesia & Analgesia® is published for the International Anesthesia Research Society® by Lippincott Williams & Wilkins and Stanford University Libraries' HighWire Press®. Copyright 2004 by the International Anesthesia Research Society. Online ISSN: 1526-7598   Print ISSN: 0003-2999 HighWire Press