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Researchers report anesthetic effects
Researchers report anesthetic effects Halothane, the most commonly used inhalation anesthetic agent, depresses clearance of the mucus from the aitways, according to results of experiments by A R Forbes, MD, of the University of California Medical Center, San Francisco. Dr Forbes said it is possible that depression of this mechanism during anesthesia could lay the foundation for the development of postoperative pneumonia by preventing or slowing the removal of sputum and bacteria. The lung is cleared of inhaled particles by sweeping mucus upwards continuously toward the larynx by hairlike cilia on the surface beating in waves of 1,000 times a minute. Dust and bacteria, landing on the surface of the mucus, are swept up with it to the vocal cords to be swallowed or coughed up as sputum. Animals were anesthetized with pentothal, a rapid-acting intravenous barbiturate and a tube inserted into the trachea through the mouth. Basic measurements of cilia activity were made by means of a fine radioactive droplet placed on the mucous layer. Movement of the droplet and the mucus was detected by radioactivity counters placed on the neck. Then each animal was given a standard dose of the inhalation agent, halothane. In each case, the rate of mucous flow up the trachea dropped off. When halothane was increased up to two times the standard dose, the rate fell further. As the dose of halothane was reduced, the rate returned to earlier values. “If the depression from halothane slows removal of mucus from the small airways, it
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could conceivably result in blockage of the airway with collapsed lung tissue behind it,” said Dr Forbes. “Further studies in patients under anesthesia, however, would be necessary to substantiate this.” Anesthetics of the narcotic type may have a rebound effect and depress breathing a second time after normality has apparently been achieved, according to researchers at the University of California Medical Center, San Francisco. The conclusion was based on studies with Innovar, a combination containing one part of the narcotic analgesic, fentanyl, and 50 parts of the tranquilizer, droperidol. The combined effect produces a quiet state and diminished response to painful stimuli. It is used to allay fears when a tube must be inserted into the stomach and as a prernedication or supplement to general anesthesia. Fentanyl alone or in combination with droperidol also can cause severe breathing depression in many patients. Fentanyl is many times more powerful than morphine. Studying 29 patients, the California investigators concluded that the respiratory depression associated with fentanyl alone or in the lnnovar combination may last five hours and usually follows a biphasic course. The initial depression of breathing is longer with fentanyl alone than with Innovar. The second depression of breathing occurs about 2 1/2 hours after the last dose of the narcotic. That fentanyl and lnnovar depress breathing is not surprising. “However, the recurrence of respiratory depression in the
AORN Journal, November 1975, Vol22, No 5
recovery room after normality had apparently been achieved was unexpected and may be of considerable clinical concern,” Lawrence D Becker, MD, reported. Another surprise was that the tranquilizer, droperidol, did not enhance the respiratory depression but actually helps relieve it. “The recurrence of depression probably is not unique to fentanyl or lnnovar but may occur following any narcotic,” said Dr Becker. His co-workers in the study were Bradford A Paulson, MD, Ronald D Miller, MD, and John W Severinghaus, MD.
rn In contrast to previous reports in the medical literature, investigators from the University of Florida College of Medicine, Gainesville, have found that ketamine does not elevate pressure within the eye. Ketamine is a drug often used by ophthalmalogists for anesthetizing children in conducting an examination or when an eye is wounded and injured. When an eye is injured, it is likely that the pressure within the eye will be elevated. Physicians are concerned that ketamine will increase this pressure further, and they are testing various anesthetics to determine which has the least effect on intraocular pressure. “In contrast to the results of others, our findings show that ketamine anesthesia produces a significant decrease in intraocular pressure,” said Baiba Ausinsch, MD, Edwin S Munson, MD, and Robert L Rayburn, MD, who presented the study. “We conclude that it can be used with safety in healthy, sedated pediatric patients.” They studied 12 healthy children ranging in age from 1 to 10 years. Before administering anesthesia, they measured the pressure within the eye with a tonometer. Ketamine was administered in an amount proportional to the patient’s weight. To evaluate the effects of other anesthetic drugs and techniques, half the patients also received tubocurarine, a skeletal muscle relaxant, and nitrous oxide inhalation. This procedure necessitated placing a breathing tube in the trachea. There was a slight but significant decrease in pressure five minutes after the first ketamine injection and a further decrease after the second dose. Administration of
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tubocurarine did not produce any further change. However, the tube in the trachea caused a rise in pressure with a return toward normal values after nitrous oxide was administered to patients who were not fully relaxed during the intubation procedure.
m An antibiotic, clindamycin, can prolong the effect of drugs given to relax muscles in anesthesiology and cause a postoperative insufficiency in breathing. Lawrence D Becker, MD, and Ronald D Miller, MD, of the Department of Anestheisa, University of California Medical Center, San Francisco, said clindamycin acts on muscle membrane and adjacent sites to interfere with muscles required in breathing. Neostygmine, a drug used to increase muscle tone, may partially offset this depression of muscle function, the physicians said. These reports were presented at the annual meeting of the American Society of Anesthesiologists in Chicago in October.
AORN Journal, November 1975, Vol22, No 5
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could conceivably result in blockage of the airway with collapsed lung tissue behind it,” said Dr Forbes. “Further studies in patients under anesthesia, however, would be necessary to substantiate this.” Anesthetics of the narcotic type may have a rebound effect and depress breathing a second time after normality has apparently been achieved, according to researchers at the University of California Medical Center, San Francisco. The conclusion was based on studies with Innovar, a combination containing one part of the narcotic analgesic, fentanyl, and 50 parts of the tranquilizer, droperidol. The combined effect produces a quiet state and diminished response to painful stimuli. It is used to allay fears when a tube must be inserted into the stomach and as a prernedication or supplement to general anesthesia. Fentanyl alone or in combination with droperidol also can cause severe breathing depression in many patients. Fentanyl is many times more powerful than morphine. Studying 29 patients, the California investigators concluded that the respiratory depression associated with fentanyl alone or in the lnnovar combination may last five hours and usually follows a biphasic course. The initial depression of breathing is longer with fentanyl alone than with Innovar. The second depression of breathing occurs about 2 1/2 hours after the last dose of the narcotic. That fentanyl and lnnovar depress breathing is not surprising. “However, the recurrence of respiratory depression in the
AORN Journal, November 1975, Vol22, No 5
recovery room after normality had apparently been achieved was unexpected and may be of considerable clinical concern,” Lawrence D Becker, MD, reported. Another surprise was that the tranquilizer, droperidol, did not enhance the respiratory depression but actually helps relieve it. “The recurrence of depression probably is not unique to fentanyl or lnnovar but may occur following any narcotic,” said Dr Becker. His co-workers in the study were Bradford A Paulson, MD, Ronald D Miller, MD, and John W Severinghaus, MD.
rn In contrast to previous reports in the medical literature, investigators from the University of Florida College of Medicine, Gainesville, have found that ketamine does not elevate pressure within the eye. Ketamine is a drug often used by ophthalmalogists for anesthetizing children in conducting an examination or when an eye is wounded and injured. When an eye is injured, it is likely that the pressure within the eye will be elevated. Physicians are concerned that ketamine will increase this pressure further, and they are testing various anesthetics to determine which has the least effect on intraocular pressure. “In contrast to the results of others, our findings show that ketamine anesthesia produces a significant decrease in intraocular pressure,” said Baiba Ausinsch, MD, Edwin S Munson, MD, and Robert L Rayburn, MD, who presented the study. “We conclude that it can be used with safety in healthy, sedated pediatric patients.” They studied 12 healthy children ranging in age from 1 to 10 years. Before administering anesthesia, they measured the pressure within the eye with a tonometer. Ketamine was administered in an amount proportional to the patient’s weight. To evaluate the effects of other anesthetic drugs and techniques, half the patients also received tubocurarine, a skeletal muscle relaxant, and nitrous oxide inhalation. This procedure necessitated placing a breathing tube in the trachea. There was a slight but significant decrease in pressure five minutes after the first ketamine injection and a further decrease after the second dose. Administration of
790
tubocurarine did not produce any further change. However, the tube in the trachea caused a rise in pressure with a return toward normal values after nitrous oxide was administered to patients who were not fully relaxed during the intubation procedure.
m An antibiotic, clindamycin, can prolong the effect of drugs given to relax muscles in anesthesiology and cause a postoperative insufficiency in breathing. Lawrence D Becker, MD, and Ronald D Miller, MD, of the Department of Anestheisa, University of California Medical Center, San Francisco, said clindamycin acts on muscle membrane and adjacent sites to interfere with muscles required in breathing. Neostygmine, a drug used to increase muscle tone, may partially offset this depression of muscle function, the physicians said. These reports were presented at the annual meeting of the American Society of Anesthesiologists in Chicago in October.
AORN Journal, November 1975, Vol22, No 5