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Effect on outcome of prolonged exposure of patients to nitrous oxide
also classified into three categories with respect to their relation to the inferior alveolar nerve canal. Of the 48 cases, 44 showed bone change radiographically, 27 showed invasive defects and 17 showed erosive defects. The histologic specimens were examined with attention given to bone involvement and the extent of tumor spread. A comparison between the histologic findings and the radiographic appearance was then made. The analysis &owed two patterns of bone involvement based on the alignment of the invading tumor. The patterns were designated as either “infiltrative” or “expansive.” The tumor invaded the mandible through the alveolar crest in all cases. The authors also noted that in advanced lesions the tumor invaded the inferior alveolar nerve or spread along the perineural space. Of the 42 cases reviewed, 22 showed expansive patterns and 20 showed infiltrative patterns. The results, when comparing the radiographic appearance to the histologic pattern, showed that of the 24 cases with invasive bone defects, 17 showed an infiltra%iue pattern and 7 an expansive pattern. Of the 14 cases with erosive bone defects, 12 showed the expansive pattern and 2 showed the infiltrative pattern. The authors showed found that there were two basic patterns of bone involvement in squamous cell carcinoma of the lower ridge. The infiltrative pattern showed the tumor invading the mandible through defects in cortical bone or periodontal space, or by destroying the bone, and then spreading progressively through the canceilous space. In the expansive pattern the tumor invaded the mandible by eroding the bone ahead of the tumor. The authors concluded that marginal resection does not appear to be an appropriate technique for lesions showing the infiltrative pattern. The authors noted a correlation between the sizes of nests of tumor cells and the pattern of bone invasion; the infiltrative pattern tended to form smaller islands as compared with the expansive pattern. A comparison between radiologic and histologic features led to the conclusion that the radiogenetically detected bone defects are not necessarily correlated with the patterns of bone involvement. Finally, the authors feel that it is netessary to develop a more reliable technique for assessing the pattern of bone involvement.-6.R. REGENYE
fecas were
Reprintrequests to Dr Totsuka: First Department of Oral Surgery, School of Dentistry, Hokkaido University, Kita 13, Nisbi 7, Kitaku, Sapporo 060, Japan.
FlttmazeniH Reverses Sedation After Midazolam-Induced General Anesthesia in Ambulatory Surgery Patients. Philip BK, Simpson TH, Hauch MA, et al. Anesth Analg 71:371, 1990 Flumazenil is a specific competitive benzodiazepine antagonist that antagonizes the amnestic, anxiolytic, and anesthetic effects of the therapeutic benzodiazepines. This study was designed to investigate the use of flumazenil to reverse postoperative sedation in ambulatory patients who have had midazolam-induced general anesthesia. Thirty-one ASA physical status I or II nonpregnant women scheduled for elective gynecologic ambulatory surgery lasting less than 90 minutes were included in this double-b&d study. Testing protocol included three psychodiagnostic tests to evaluate the level of sedation: 1) visual analog scale (VAS) for sedation/alertness, 2) Trieger dot test (TB), 3) digit symbol substitution test @SST). Induction of general anesthesia was accomphsbed with 0.2 m&g midazolam. Additional midazolam
(0.05 mg/kg) or fentanyl (1 p,g/kg) was given if clinical signs of light anesthesia occurred. Patients were then randomly assigned to receive an unidentif?ed solution containing either flumazenil(O.1 mg/mL) or placebo; the placebo solution was inactive flumazenil vehicle. Every 60 seconds, 2 mL of the placebo or flumazenl solution was administered intravenously until the patient was awake and calm or until 10 mL was given. Complete reversal of sedation, Eo a fully awake and alert state, was not intended. Administration of additional flumazenil or placebo was based on the Observer’s Assessment of Alertness and Sedation, a multicategory assessment scale. Additional drug was given if the patient exhibited any of the following: response only after their name was called loudly or repeatedly, marked facial relaxation, glazed eyes with marked ptosis, or slurred or prominently slowed speech. The flumazenil and placebo grotips were not different with respect to age, weight, Reight, duration of surgery, time from induction dose of midazolgm to study drug administration, or amounts of fentanyl and midazolam given, There were no statistical differences between the groups on any test when comparing preoperative control or postoperative baseline values. The flumazenil group scored significantly better than the placebo group on all three psychodiagnostic tests at 5 to 60 minutes afxer study drug administraGon, At 120 aBd 180 minutes, the results of the two groups were not different. For all tests, postoperative scores were significantly lower than preoperative at time 0 (postoperative baseline) through 120 minutes after administration of placebo QP flumazenil. In this study, flumazenil was effective for reversal of the postoperative sedative effects after midazolam-induced general anesthesia. Patients given Wumazenl had higher VAS, TD, and DSST scores than did patients who received placebo. The reversal of sedation occurred within 5 minutes of receiving fiumazenil and lasted less than 420 minutes. Flumazenil did reverse postoperative sedation in ambulatory patients who had undergone midazolam-induced general anesthesia for gynecologic surgery. The degree of reversal could be hmieed, and by titrating the flumazenil dose a state of “awake and calm” could be achieved. The reversal effect was, however, no longer evident by 128 minutes after Wumazenil administration. Caution, therefore, is needed to avoid premature discharge of ambulatory patients after midazolaminduced general anesthesia during the time that flumazenil is effective.-P.H. ARTENBEK Reprint requests to Dr Philip: Department of Anesthesiz, Brigham and Woman’s Hospitd, 75 Francis Street, Boston, MA 02115. Effect on Outcome of Prolonged
Exposure of Patients to Nitrous Oxide. Lampe GH, Wauk LZ, Donegan JH, et al. Anesth Analg 71586, 1990 Prolonged exposure to nitrous oxide (N,O) has been associated with morbidity (aplastic anemia, neuropathy) and mortality, although this has only been described in exposures of several days or repeated exposures. The authors examined the clinical effects of a single, lengthy exposure to N,O and its effects on outcome and patient satisfaction. Twenty-six patients undergoing resection of an acoustic neuroma (typically a IO-hour surgery) received isoflurane with either 150% oxygen or a 50-50 mixture of N&/oxygen. Standard physiologic monitors were used, and oxygen saturation was meastared regaarIy for
1136
CURRENT
24 hours, and once each day thereafter. Other postoperative vital signs were recorded on a routine basis. Blood samples were taken at specific intervals postoperatively to assess hepatic function. Subjective data from the patient were recorded regarding pain and memory of the anesthetic, and neurologic status was tested using the Glasgow Coma Score. All data collection was performed by blinded investigators. There were no significant differences between groups in any area, and there was no increase in nausea and vomiting with N,O as had been reported in other studies. Despite a reluctance by some to use N,O routinely for elective surgery, the authors conclude that these concerns are unwarranted and N,O may be administered for up to 10 hours without toxic effects.-J. DEMBO Reprint requests to Dr Eger: Department of Anesthesia, University of California, San Francisco,
CA 94143-0464.
Ultrasound Assessment of the Position of the Tongue During Induction of Anesthesia. Abernethy LJ, Allan PL, Drummond GB. Br J Anaesth 65:744, 1990 It is commonly accepted that airway obstruction in the unconscious patient occurs primarily due to the tongue falling posteriorly in the pharynx, but several studies have suggested that there may be other causes, including the soft tissues of the pharynx or the epiglottis. Real-time ultrasound scanning was used in this study to assess changes in tongue position in the anesthetized patient. Fifteen healthy women undergoing gynecologic surgery had ultrasound scanning transducers placed below the chin then secured to the bed. Ultrasound imaging began before anesthetic induction and continued until 1 minute after loss of consciousness. Representative video images were photographed, and a blinded observer examined and outlined tongue position in each photograph. The radius of t5e arc described by the dorsum of the tongue was used to compare position before and after anesthetic induction. No consistent tongue movement was noted among patients, even in those patients with clinically evident airway obstruction. No inore than 6-mm movement was seeq in the posterior tongue, in contrast to 1.5 to 20 mm seen in other studies during swallowing. The authors conclude that the small, inconsistent changes of tongue PO-
LHTERATURE
sition seen after induction of anesthesia were unln&ely to be significant contributors to airway obstruction.-J. DEMBO Reprint requests to Dr Abemethy: Royal Infirmary burgh, Lam&on Place, Edinburgh EM3 9YW.
of Edin-
A Clinical Trial of Long-Acting Local Anesthetics for Be& odontal Surgery. Grout RJ, Koraido G, Moore PA. Awesth Prog 37:193, 1990 Previous clinical studies have shown that two amide local anesthetics, bupivacaine and etidocaine, can be used safely and effectively for oral surgical procedut-es. The purpose of this study was to evaluate the efficacy of these anesthetics for periodontal surgery. Healthy adtilts requiring periodontal surgery were studied in one of two ways. Patients needing surgery bilaterally with both sides being equal in difficulty were randomly given either 2% lidocaine 1: 100,000 epinephrine (LID) or 1.5% etidocaine 1:200,000 (ETI). This was done in double-blind, crossover fashion with the other anesthetic given at the second appointment. Patients without matching quadr+nts were randomly assigned to receive either 1.5% etidocaine 1:200,000 epinephrine or 0.5% bupivacaine 1:2OO,QOO epinephrine (BUP). Patient questionnaires were givqn to assess duration of anesthesia, onset and severity dIpsstoperative pain, and analgesics required. Surgeons were asked to rate estimated surgical trauma, time for hsr~setof anesthesia, estimate of intraoperative bleeding, and profundity of anesthesia. No significant differences were seen with onset or quality of anesthesia. A trend towards less severe postoperative pain was seen with ETI compared with LID, but no such trend was seen with ET1 compared with BUP. Significantly more bleeding occurred with ET1 than with LID, a finding reported in other studies. The authors conclude that long-actipg local anesthetics appear to be effective for p&in control Mowing periodontal surgery, but ET1 may not be the best sole anesthetic agent due to decreased hemiostasis and poorer visibility of the surgical field.--J. DEMBO Reprint requests to Dr Moore: Department of Pharmacology/ Physiology, University of Pittsburgh School of Dental Idedicine, Pittsburgh, PA 15261.
fecas were
Reprintrequests to Dr Totsuka: First Department of Oral Surgery, School of Dentistry, Hokkaido University, Kita 13, Nisbi 7, Kitaku, Sapporo 060, Japan.
FlttmazeniH Reverses Sedation After Midazolam-Induced General Anesthesia in Ambulatory Surgery Patients. Philip BK, Simpson TH, Hauch MA, et al. Anesth Analg 71:371, 1990 Flumazenil is a specific competitive benzodiazepine antagonist that antagonizes the amnestic, anxiolytic, and anesthetic effects of the therapeutic benzodiazepines. This study was designed to investigate the use of flumazenil to reverse postoperative sedation in ambulatory patients who have had midazolam-induced general anesthesia. Thirty-one ASA physical status I or II nonpregnant women scheduled for elective gynecologic ambulatory surgery lasting less than 90 minutes were included in this double-b&d study. Testing protocol included three psychodiagnostic tests to evaluate the level of sedation: 1) visual analog scale (VAS) for sedation/alertness, 2) Trieger dot test (TB), 3) digit symbol substitution test @SST). Induction of general anesthesia was accomphsbed with 0.2 m&g midazolam. Additional midazolam
(0.05 mg/kg) or fentanyl (1 p,g/kg) was given if clinical signs of light anesthesia occurred. Patients were then randomly assigned to receive an unidentif?ed solution containing either flumazenil(O.1 mg/mL) or placebo; the placebo solution was inactive flumazenil vehicle. Every 60 seconds, 2 mL of the placebo or flumazenl solution was administered intravenously until the patient was awake and calm or until 10 mL was given. Complete reversal of sedation, Eo a fully awake and alert state, was not intended. Administration of additional flumazenil or placebo was based on the Observer’s Assessment of Alertness and Sedation, a multicategory assessment scale. Additional drug was given if the patient exhibited any of the following: response only after their name was called loudly or repeatedly, marked facial relaxation, glazed eyes with marked ptosis, or slurred or prominently slowed speech. The flumazenil and placebo grotips were not different with respect to age, weight, Reight, duration of surgery, time from induction dose of midazolgm to study drug administration, or amounts of fentanyl and midazolam given, There were no statistical differences between the groups on any test when comparing preoperative control or postoperative baseline values. The flumazenil group scored significantly better than the placebo group on all three psychodiagnostic tests at 5 to 60 minutes afxer study drug administraGon, At 120 aBd 180 minutes, the results of the two groups were not different. For all tests, postoperative scores were significantly lower than preoperative at time 0 (postoperative baseline) through 120 minutes after administration of placebo QP flumazenil. In this study, flumazenil was effective for reversal of the postoperative sedative effects after midazolam-induced general anesthesia. Patients given Wumazenl had higher VAS, TD, and DSST scores than did patients who received placebo. The reversal of sedation occurred within 5 minutes of receiving fiumazenil and lasted less than 420 minutes. Flumazenil did reverse postoperative sedation in ambulatory patients who had undergone midazolam-induced general anesthesia for gynecologic surgery. The degree of reversal could be hmieed, and by titrating the flumazenil dose a state of “awake and calm” could be achieved. The reversal effect was, however, no longer evident by 128 minutes after Wumazenil administration. Caution, therefore, is needed to avoid premature discharge of ambulatory patients after midazolaminduced general anesthesia during the time that flumazenil is effective.-P.H. ARTENBEK Reprint requests to Dr Philip: Department of Anesthesiz, Brigham and Woman’s Hospitd, 75 Francis Street, Boston, MA 02115. Effect on Outcome of Prolonged
Exposure of Patients to Nitrous Oxide. Lampe GH, Wauk LZ, Donegan JH, et al. Anesth Analg 71586, 1990 Prolonged exposure to nitrous oxide (N,O) has been associated with morbidity (aplastic anemia, neuropathy) and mortality, although this has only been described in exposures of several days or repeated exposures. The authors examined the clinical effects of a single, lengthy exposure to N,O and its effects on outcome and patient satisfaction. Twenty-six patients undergoing resection of an acoustic neuroma (typically a IO-hour surgery) received isoflurane with either 150% oxygen or a 50-50 mixture of N&/oxygen. Standard physiologic monitors were used, and oxygen saturation was meastared regaarIy for
1136
CURRENT
24 hours, and once each day thereafter. Other postoperative vital signs were recorded on a routine basis. Blood samples were taken at specific intervals postoperatively to assess hepatic function. Subjective data from the patient were recorded regarding pain and memory of the anesthetic, and neurologic status was tested using the Glasgow Coma Score. All data collection was performed by blinded investigators. There were no significant differences between groups in any area, and there was no increase in nausea and vomiting with N,O as had been reported in other studies. Despite a reluctance by some to use N,O routinely for elective surgery, the authors conclude that these concerns are unwarranted and N,O may be administered for up to 10 hours without toxic effects.-J. DEMBO Reprint requests to Dr Eger: Department of Anesthesia, University of California, San Francisco,
CA 94143-0464.
Ultrasound Assessment of the Position of the Tongue During Induction of Anesthesia. Abernethy LJ, Allan PL, Drummond GB. Br J Anaesth 65:744, 1990 It is commonly accepted that airway obstruction in the unconscious patient occurs primarily due to the tongue falling posteriorly in the pharynx, but several studies have suggested that there may be other causes, including the soft tissues of the pharynx or the epiglottis. Real-time ultrasound scanning was used in this study to assess changes in tongue position in the anesthetized patient. Fifteen healthy women undergoing gynecologic surgery had ultrasound scanning transducers placed below the chin then secured to the bed. Ultrasound imaging began before anesthetic induction and continued until 1 minute after loss of consciousness. Representative video images were photographed, and a blinded observer examined and outlined tongue position in each photograph. The radius of t5e arc described by the dorsum of the tongue was used to compare position before and after anesthetic induction. No consistent tongue movement was noted among patients, even in those patients with clinically evident airway obstruction. No inore than 6-mm movement was seeq in the posterior tongue, in contrast to 1.5 to 20 mm seen in other studies during swallowing. The authors conclude that the small, inconsistent changes of tongue PO-
LHTERATURE
sition seen after induction of anesthesia were unln&ely to be significant contributors to airway obstruction.-J. DEMBO Reprint requests to Dr Abemethy: Royal Infirmary burgh, Lam&on Place, Edinburgh EM3 9YW.
of Edin-
A Clinical Trial of Long-Acting Local Anesthetics for Be& odontal Surgery. Grout RJ, Koraido G, Moore PA. Awesth Prog 37:193, 1990 Previous clinical studies have shown that two amide local anesthetics, bupivacaine and etidocaine, can be used safely and effectively for oral surgical procedut-es. The purpose of this study was to evaluate the efficacy of these anesthetics for periodontal surgery. Healthy adtilts requiring periodontal surgery were studied in one of two ways. Patients needing surgery bilaterally with both sides being equal in difficulty were randomly given either 2% lidocaine 1: 100,000 epinephrine (LID) or 1.5% etidocaine 1:200,000 (ETI). This was done in double-blind, crossover fashion with the other anesthetic given at the second appointment. Patients without matching quadr+nts were randomly assigned to receive either 1.5% etidocaine 1:200,000 epinephrine or 0.5% bupivacaine 1:2OO,QOO epinephrine (BUP). Patient questionnaires were givqn to assess duration of anesthesia, onset and severity dIpsstoperative pain, and analgesics required. Surgeons were asked to rate estimated surgical trauma, time for hsr~setof anesthesia, estimate of intraoperative bleeding, and profundity of anesthesia. No significant differences were seen with onset or quality of anesthesia. A trend towards less severe postoperative pain was seen with ETI compared with LID, but no such trend was seen with ET1 compared with BUP. Significantly more bleeding occurred with ET1 than with LID, a finding reported in other studies. The authors conclude that long-actipg local anesthetics appear to be effective for p&in control Mowing periodontal surgery, but ET1 may not be the best sole anesthetic agent due to decreased hemiostasis and poorer visibility of the surgical field.--J. DEMBO Reprint requests to Dr Moore: Department of Pharmacology/ Physiology, University of Pittsburgh School of Dental Idedicine, Pittsburgh, PA 15261.