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OBSTETRIC ANESTHESIA

Ventilatory Support Using Bilevel Positive Airway Pressure During Neuraxial Blockade in a Patient with Severe Respiratory Compromise

Department of Anesthesiology and Pain Management, University of Texas Southwestern Medical Center, Dallas, Texas

Address correspondence and reprint requests to Shiv Sharma, MD, FRCA, Department of Anesthesiology and Pain Management, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390-9068. Address e-mail to shiv.sharma{at}utsouthwestern.edu.

	Abstract

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In pregnant patients with myasthenia gravis and respiratory compromise, neuraxial anesthesia for lower abdominal surgery can risk further respiratory depression. We report the use of epidural anesthesia for dilation and curettage and tubal ligation in a 26-yr-old woman with a 12-wk intrauterine pregnancy with severe myasthenia gravis and respiratory insufficiency in whom ventilatory support during anesthesia was provided successfully using bilevel positive airway pressure ventilation. This report demonstrates how the use of bilevel positive airway pressure for ventilatory support may improve the safety of regional anesthesia in patients with severe respiratory compromise.

	Introduction

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General anesthesia with tracheal intubation for lower abdominal surgery in patients with myasthenia gravis (MG) with severe respiratory insufficiency may result in prolonged postoperative ventilation and associated complications (1,2). Although neuraxial blockade is often desirable and considered advantageous for surgical procedures in pregnant women, neuraxial blockade in myasthenic patients with respiratory insufficiency may cause more weakness of intercostal muscles with subsequent respiratory depression. Ventilatory adjuncts such as bilevel positive airway pressure ventilation (BiPAP) have successfully been used to manage acute respiratory failure in myasthenic crisis without tracheal intubation (3). We report a case of a pregnant MG patient with severe respiratory compromise who received epidural anesthesia for dilation and curettage and bilateral tubal ligation in whom BiPAP was used for noninvasive ventilatory support during the procedure.

	Case Report

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A 26-yr-old, G3 P1 woman with a 12-wk intrauterine pregnancy and a 2-yr history of severe antibody negative MG was scheduled for dilation and curettage and bilateral tubal ligation. She was 155 cm tall and weighed 77 kg.

She had significant respiratory involvement to include bilateral phrenic nerve and diaphragmatic paralysis, central sleep apnea; chronic respiratory acidosis (arterial blood gases: pH 7.30; Po ₂ 66 mm Hg; Pco₂ 68 mm Hg; Bicarb 36 mEq/L; base excess -8.4 mEq/L on room air); and a restrictive pattern of ventilation (forced expiratory volume in 1 s – 1.42 L, 48% of predicted; forced vital capacity – 1.56 L, 46% of predicted). The patient suffered from significant orthopnea with no cardiac dysfunction and could sleep at night only by sitting up in a chair using BiPAP (Respironic Inc., BiPAP S/T-D 30 Ventilatory Support System, Whisper, CA). Her typical BiPAP settings were as follows: inspiratory positive airway pressure 10–20 cm H₂O, expiratory positive airway pressure 5–10 cm H₂O, respiratory rate spontaneous 16–22 breaths/min. The patient otherwise had a Mallampati grade I airway. There was no bulbar involvement. Neurologic examination was significant for mild weakness in her right quadriceps muscle. A history of thymus hyperplasia or surgery was negative. The patient had stage III to IV disease based on the Osserman and Genkins (4) classification of the severity of MG (I—ocular signs only; II—generalized mild muscle weakness or bulbar dysfunction; III—respiratory dysfunction; IV—late severe generalized MG). Medical management of her MG included pyridostigmine 900 mg per day in divided doses and prednisone 80 mg per day.

We considered the use of epidural anesthesia as safe in this patient because it would avoid prolonged postoperative ventilation associated with general anesthesia, while intraoperative BiPAP ventilatory support would help offset any respiratory depression associated with epidural anesthesia. After placement of standard ASA monitors and establishment of peripheral venous access, aspiration prophylaxis was provided with Bicitra 30 mL per os and metoclopramide 10 mg IV. A multiport epidural catheter was threaded 4 cm into the epidural space at L3–4 using a 17-gauge Tuohy needle and loss of resistance to saline. After negative aspiration of cerebrospinal fluid and blood and a negative response to a test dose with 3 mL of 2% lidocaine with epinephrine 15 µg, the epidural was incrementally dosed over 20 min with 20 mL of 2% lidocaine and 100 µg of fentanyl to a bilateral T4 ice level. The patient was first placed in a lithotomy position with a pillow under the upper back for the dilation and curettage and then supine for the mini-laparotomy tubal ligation, which was performed through a 3-cm superapubical incision. Her typical BiPAP settings were used for ventilatory support during the procedure.

The patient maintained her hemoglobin oxygen saturation between 96% and 99% on room air with BiPAP. Her respiratory rate was 20/min with no evidence of dyspnea, and was hemodynamically stable. The procedure lasted 60 min, 1500 mL of lactated Ringer's solution was given, urine output was 200 mL, and blood loss was 150 mL. The immediate postoperative course was uneventful with the patient's oxygen saturation between 97% and 99% on room air with BiPAP. After 2 h the patient was discharged from the postanesthesia care unit with vital signs within normal range, and 3 days later she was discharged home.

	Discussion

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In our patient, despite severe respiratory insufficiency, we safely provided epidural anesthesia by titrating the epidural block slowly, using BiPAP for ventilatory support during the procedure and closely monitoring the patient's respiratory status. Using this technique, we avoided respiratory depression during regional anesthesia as well as the risk for prolonged postoperative ventilation with general anesthesia. It was easier to use the BiPAP ventilator in this patient, as she was familiar with the device. However, patients naïve to a BiPAP ventilator may need some training with the device before its use during regional anesthesia. Patient cooperation is vital to the successful application of BiPAP. BiPAP is not recommended for patients with altered mental status, an abnormal gag reflex, or inability to clear respiratory secretions. Other adverse effects of BiPAP include skin breakdown over the bridge of the nose resulting from pressure from the mask.

BiPAP is a noninvasive positive pressure ventilatory support device that uses either a nasal mask or a facemask to obviate the need for endotracheal intubation (5). BiPAP devices allow the delivery of adjustable amounts of continuous positive pressure during inspiration and expiration. Inspiratory positive airway pressure helps overcome upper airway resistance, whereas expiratory positive airway pressure keeps the upper airway open and prevents alveolar collapse (3). Rabinstein and Wijdicks (3) effectively used BiPAP ventilation in the intensive care unit to manage acute respiratory failure in patients with chronic neuromuscular disease such as myasthenia gravis. Tobias et al. (5) demonstrated the advantages of BiPAP in managing impending respiratory failure in the postanesthesia care unit. Iwama (6) successfully used BiPAP for ventilatory support during combined epidural and propofol anesthesia for lower abdominal surgery in a patient with severe respiratory compromise.

There is no ideal anesthetic technique in MG patients with severe respiratory compromise. General anesthesia carries the risk of prolonged postoperative ventilation, whereas neuraxial blockade risks respiratory depression. This case report shows how neuraxial anesthesia may be used in patients with severe respiratory insufficiency by using BiPAP ventilation to protect against respiratory depression.

	Footnotes

 
Accepted for publication November 1, 2005.

	References

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1. Baraka A. Anaesthesia and myasthenia gravis. Can J Anaesth 1992;39:476–86.[Web of Science][Medline]
2. Bader AM. Neurologic and Neuromuscular disease: Myasthenia Gravis. In: Chestnut, DH. Obstetric anesthesia: principles and practice, 3^rd ed. Philadelphia, PA: Elsevier Mosby; 2004:872–91.
3. Rabinstein A, Wijdicks EFM. BiPAP in acute respiratory failure due to myasthenic crisis may prevent intubation. Neurology 2002;59:1647–9.[Abstract/Free Full Text]
4. Osserman KE, Genkins G. Studies on myasthenia gravis. Review of a twenty-year experience in over 1200 patients. Mount Sinai J Med 1971;38:497–537.[Medline]
5. Tobias JD. Noninvasive ventilation using bilevel positive airway pressure to treat impending respiratory failure in the postanesthesia care unit. J Clin Anesth 2000;12:409–12.[Web of Science][Medline]
6. Iwama H. Application of nasal bi-level positive airway pressure to respiratory support during combined epidural-propofol anesthesia. J Clin Anesth 2002;14:24–33.[Web of Science][Medline]

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a colleague Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (5) Citing Articles via Google Scholar Google Scholar Articles by Warren, J. Articles by Sharma, S. K. Search for Related Content PubMed PubMed Citation Articles by Warren, J. Articles by Sharma, S. K. Related Collections Critical Care Obstetrics Regional Anesthesia