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Halothane, nitrous oxide, and oxygen were given for
45 min using a Jackson-Rees circuit. Total excision of the tumor and repair of the tongue was carried out successfully. Histologic findings showed the tumor to be a congenital embryonal rhabdomyosarcoma. Direct laryngoscopy is still a very worthwhile maneuver in these situations where a difficult airway is anticipated, because it may certainly be possible to bring the larynx into view. Orotracheal intubation after pulling the tongue out and applying gentle external laryngeal pressure may be tried first during intubation attempts whenever there is a large mass arising from the tongue. Facilities for fiberoptic laryngoscopy, retrograde wire insertion, blind techniques, tracheostomy, or cricothyroidotomy should be immediately available as an alternative method of establishing an airway.
K. Krishna Mohan,
MD MD, DA Department of Anaesthesiology
Institute of Medical Sciences Banaras Hindu University Varanasi-221005 India
Digital Nerve Blocks and Pulse Oximeter Signal Detection To the Editor: A digital nerve block is of value not only in restoring pulse oximeter readings, as reported by Bourke and Grayson (l), but also in differentiating between cyanosis from hypoxemia and that due to peripheral vasoconstriction (2). It is also useful, as I have reported (3), for improving the indirect measurement of blood pressure with a photo-sphygmometer or a digital cuff. I found that the vigorous rubbing of a fingertip milks out desaturated blood and, perhaps with local histamine release, temporarily restores capillary flow. It is a useful emergency measure to assist in assessing the cause of peripheral cyanosis while a digital block is being performed or an arterial blood sample is being obtained. Comroe and Botelho (4) reported that visual observation for cyanosis (without a digital block) is not reliable. However, the color difference between the blocked and unblocked digit mentioned by Bourke and Grayson can be useful. Douglas W. Eastwood, MD Department of Anesthesiology University Hospitals of Cleveland 2078 Abington Road Cleveland, OH 441 08
References 1. Bourke DL, Grayson RF. Digital nerve blocks can restore pulse oximeter
signal detection. Anesth Analg 1991;73:815-7. 2. Eastwood DW. Finger block for local vasodilation. Anesthesiology 1959; 20:704. 3. Eastwood DW. Use of a photo-sphygmometer in indirect blood pressure measurements. Anesthesiology 1959;20:704-7. 4. Cornroe JH Jr, Botelho 5. The unreliability of cyanosis in the recognition of arterial anoxemia. Am J Med Sci 1947;214:1-6.
LETTERS TO THE EDITOR
Another Use for Precordial Stethoscopes To the Editor: The determination of sensory block level during epidural and spinal anesthesia is commonly performed by swabbing the skin repeatedly with a tiny alcohol pad. In many cases, so little alcohol is deposited on the skin that only minimal evaporative cooling takes place, and patients find it difficult to distinguish between light touch and temperature sensation. Alcohol-soaked sponges avoid this problem but can be messy and are not always readily available. I have found that a precordial stethoscope (a simple device, present in all operating rooms) can be used to provide a more reliable assessment of temperature sensation during regional anesthesia. As operating rooms are typically kept cool, and the specific heat of steel used to fabricate these devices is high, contact with the skin results in an unambiguous sensation of cold. Furthermore, the sensation of cold lasts only as long as the metal is actually in contact with skin (in contrast to the prolonged cooling when alcohol slowly evaporates). The back of the stethoscope can be advanced over the skin surface from thigh upward while asking the patient to indicate the onset of a cold sensation. Typically, a very distinct block level is reproducibly determined. As the metal will not warm immediately, bilateral block levels can be checked quickly and easily. Care must be taken to avoid handling the metal for too long, and of course an unusually warm operating room will void this technique entirely. However, in most situations the precordial stethoscope, like many other objects that we place on the patients’ skin, will elicit a very definite cold sensation. James M. Hynson,
Department of Anesthesia Mount Zion Medical Center of UC San Francisco 1600 Divisidero Street San Francisco, CA 94120-7921
Sedation for Children Undergoing Magnetic Resonance Imaging and Computed Tomography To the Editor: Anesthesia for children undergoing neurodiagnostic procedures outside the operating room suite continues to be a challenge for the anesthesiologist. Numerous anesthetic approaches to these increasingly popular diagnostic procedures have been reported (1-3). General endotracheal anesthesia and intravenous, rectal, and oral routes of drug administration each have their advocates. In 1987, after two cases of respiratory depression in infants undergoing magnetic resonance imaging had occurred, we were asked to design a protocol for administering the sedation and monitoring children during neurodiagnostic testing at Schneider Children’s Hospital, Long Island Jewish Medical Center. Before this time there was no standard criteria for
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LETTERS TO THE EDITOR
giving sedation. A variety of physicians including anesthesiologists, pediatricians, and neurologists as well as nurses were administering sedation and monitoring the children. In an attempt to provide a safe method of sedating these patients, chloral hydrate was selected. Chloral hydrate has a long history of safety in the pediatric population and is easily administered. From November 1987 through January 1990, we sedated a total of 518 children ranging in age from 6 wk to 18 yr (mean 3.6 yr) for neurodiagnostic procedures at our institution. Chloral hydrate was used in each case as the primary sedative. The protocol called for an initial dose of chloral hydrate of 75-100 mg/kg. To minimize the incidence of gastric irritation, half the dose was given orally and half rectally. If after 30 min the level of sedation was unsatisfactory, additional 25-mglkg doses of chloral hydrate were administered rectally to a maximum dose of 150 mg/kg (mean total dose 109.4 mg/kg). If the child was still restless, hydroxyzine 1.O mg/kg was administered intramuscularly. Hydroxyzine was used in 4% of the cases. Children who were teething and/or appeared to have excessive oral secretions were given glycopyrrolate 0.04 mg/kg orally to a maximum dose of 1.0 mg with the chloral hydrate. Half the children underwent computed tomography scanning and half underwent magnetic resonance imaging. Approximately 10% had a second test performed following the scan, usually an electroencephalogram. Only one patient, a 3.5-yr-old child undergoing magnetic resonance imaging, was cancelled for mild airway obstruction requiring head extension, which made the procedure impossible to perform. This child received a dose of 100 mg/kg of chloral hydrate. The largest total dose used was 6 g in a 10-yr-old 38-kg child (155 mg/kg). The time to discharge after the diagnostic procedure was less than 30 min in 78% of the patients. By 60 min, 92% of the patients had been discharged. Chloral hydrate is one of the oldest and safest of the hypnotic drugs. It is rapidly absorbed through all mucous membranes and causes minimal alterations in respiration, pulse, and blood pressure. Although the manufacturer recommends a dose of 50 mg/kg to a maximum of 1000 mg, there is little research to support this dose schedule. Judisch et al. (4) reported using orally administered doses of 100-150 mg/kg in more than 300 children undergoing ocular examination. They reported a 1%-2% failure rate and a 15% incidence of transient vomiting. One of their patients developed mild upper airway obstruction requiring several minutes of head extension. Our results are comparable except for the incidence of vomiting, which in our series was 5%. Our patients experienced less gastric irritation as half the chloral hydrate dose was administered rectally. Reports of chloral hydrate toxicity are rare. We have found it to be an extremely safe and effective medication. Using this protocol we have been able to provide a safe and effective method of sedating children for neurodiagnostic procedures.
Department of Anesthesiology Saint Raphael’s Hospital 1450 Chapel Street New Hazwn, CT 0651 1
References 1. Patterson SK, Chesney JT. Anesthetic management for magnetic resonance imaging problems and solutions. Anesth Analg 1992;74:121-8. 2. Burk NS. Anesthesia for magnetic resonance imaging. Anesthesiol Clin North Am 1989;7(3):707-21. 3. Thompson JR, Schneider S, Ashwal S, Holden BS, Hinshaw DB, Hasso AN. The choice of sedation for computed tomography in children: a prospective evaluation. Neuroradiology 1982;143:475Y. 4. Judisch GF, Anderson S, Bell WE. Chloral hydrate sedation as a substitute for examination under anesthesia in pediatric ophthalmology. Am J Ophthalmol 1980;89:560-3.
Stoma1 Leaks and Gas Bubbles To the Editor: For various reasons, anesthetists may be asked to intubate the trachea of a patient with a tracheostomy via the oral route. The volume of air inserted into the endotracheal cuff should seal the trachea without causing pressure damage to the tracheal mucosa. The correct volume needed to seal the trachea is often established by listening with a stethoscope for leakage of air from the tracheostomy site after the cuff of the newly placed oral endotracheal tube has been inflated. We propose a simple test that is useful in establishing that the trachea has been sealed by the endotracheal tube cuff. We place a clear plastic adhesive tape, such as Tegaderm 1624 Transparent IV Dressing (3M Medical-Surgical Division, St. Paul, Minn.) over the tracheostomy stoma once the cuff of the oral endotracheal tube has been inflated. If there is insufficient air in the cuff, gas bubbles will form beneath the adhesive tape. If no bubbles form, air is withdrawn from the cuff until a small gas bubble forms under the adhesive dressing. Then, an additional small volume of air is injected through the pilot balloon to seal the trachea (see Figures 1
George G.Neuman, MD Lawrence G. Kushins, MD Department of Anesthesiology Sainf Vincent’s Hospital and Medical Center of New York 153 West 11th Street New York, N Y 10011
Figure 1. Tracheostomy stoma covered by Tegaderm 1624 when a leak is present around the endotracheal tube c u f f .