When a person with Duchenne has general anesthesia, a number of serious problems may arise.
The issue of treating dental cases using local anesthetic and nitrous oxide was recently brought up. I asked several experts in pulmonary medicine (Dr. Jonathan Finder, Dr. Hemant Sawnani, and Dr. Richard Shell), dentistry (Dr. Elizabeth Vroom), and anesthesia (Dr. Norbert Weidner) and compiled their responses below.
The following do not present a risk for patients with Duchenne, with or without pulmonary dysfunction (abnormal breathing):
The use of inhaled anesthetics (i.e., halothane, isofluorane, and seroflurane) can result rhabdomyolysis (massive breakdown of skeletal muscle tissue) and hyperkalemia (the release of too much potassium into the bloodstream), which can result in cardiac arrest (heart attack). Nitrous oxide is safe, and causes none of these problems.
Nitrous oxide, used during office dental procedures by an observant dentist, is an accepted and safe practice. It is, in fact, a commonly used inhalation anesthetic in dentistry, emergency, and ambulatory centers.
Its advantages are:
Following nitrous oxide, patients are generally given oxygen for 1-2 minutes in order to “wash the nitrous out” of the respiratory system. The oxygen is administered in an “open system” (mixed with room air), so the oxygen concentration is not 100%. The use of an “oxygen washout” is also a safe and appropriate practice.
Many parents are concerned when the use of oxygen is mentioned. The use of oxygen in an ambulatory patient with normal lung function poses minimal threat to the patient. The use of oxygen by itself is a concern when its use is intended to treat hypoventilation in a non-ambulatory patient with decreased pulmonary function.
Non-ambulatory patients with Duchenne have weaker respiratory muscles. Therefore, as the disease progresses, it becomes difficult to cough and to take deep breaths. Up to a point, shallow breathing can provide the body with adequate oxygen supply and adequate removal of carbon dioxide. That delicate balance of oxygen and carbon dioxide allows breathing to continue. When extra or supplemental oxygen is given, this delicate balance is disturbed. The respiratory center may get the false impression that the body has enough oxygen, and the drive to breathe diminishes. Without effective breathing, carbon dioxide can build to dangerous levels (called hypercapnia).
Oxygen should never be given without constantly monitoring the level of carbon dioxide CO2 in the expired breath (the “end-tidal CO2”) or the CO2 level in blood. A normal end tidal CO2 is between 30-45 mmHg. A CO2 level (greater than 45 mmHg) indicates that CO2 is not being expelled from the body. Non-invasive ventilation (Bi-PAP via mouthpiece or nasal cannula) will assist with the mechanical process of breathing, delivery of oxygen and removal of CO2.
1. Becker DE, Rosenberg M, “Nitrous Oxide and the Inhalations Anesthetics,” Anesth Prog, 2008, winter, 55(4): 124-131.
2. “Respiratory Care of the Patient with Duchenne Muscular Dystrophy,” American Thoracic Society Document, Am J Respir Crit Care Med, 2004, 170: 456-465.
3. Birnkrant D, Panitch HB, Benditt JO, Boitano LJ, Carter ER, Cwik VA, Finder JD, Iannaccone ST, Jacobson LE, Kohn GL, Motoyama EK, Moxley RT, Schroth MK, Sharma GD and Sussman MD, “American College of Chest Physicians Consensus Statement on the Respiratory and Related Management of Patients wit Duchenne Muscular Dystrophy Undergoing Anesthesia or Sedation,” Chest, 2007, 132:1977-1986.