Showing papers in "Survey of Anesthesiology in 1995"

Effects of Smoking Intervention and the Use of an Inhaled Anticholinergic Bronchodilator on the Rate of Decline of FEV1. The Lung Health Study

Abstract: OBJECTIVE To determine whether a program incorporating smoking intervention and use of an inhaled bronchodilator can slow the rate of decline in forced expiratory volume in 1 second (FEV1) in smokers aged 35 to 60 years who have mild obstructive pulmonary disease. DESIGN Randomized clinical trial. Participants randomized with equal probability to one of the following groups: (1) smoking intervention plus bronchodilator, (2) smoking intervention plus placebo, or (3) no intervention. SETTING Ten clinical centers in the United States and Canada. PARTICIPANTS A total of 5887 male and female smokers, aged 35 to 60 years, with spirometric signs of early chronic obstructive pulmonary disease. INTERVENTIONS Smoking intervention: intensive 12-session smoking cessation program combining behavior modification and use of nicotine gum, with continuing 5-year maintenance program to minimize relapse. Bronchodilator: ipratropium bromide prescribed three times daily (two puffs per time) from a metered-dose inhaler. MAIN OUTCOME MEASURES Rate of change and cumulative change in FEV1 over a 5-year period. RESULTS Participants in the two smoking intervention groups showed significantly smaller declines in FEV1 than did those in the control group. Most of this difference occurred during the first year following entry into the study and was attributable to smoking cessation, with those who achieved sustained smoking cessation experiencing the largest benefit. The small noncumulative benefit associated with use of the active bronchodilator vanished after the bronchodilator was discontinued at the end of the study. CONCLUSIONS An aggressive smoking intervention program significantly reduces the age-related decline in FEV1 in middle-aged smokers with mild airways obstruction. Use of an inhaled anticholinergic bronchodilator results in a relatively small improvement in FEV1 that appears to be reversed after the drug is discontinued. Use of the bronchodilator did not influence the long-term decline of FEV1.

Does More Intensive Treatment of Acute Myocardial Infarction in the Elderly Reduce Mortality? Analysis Using Instrumental Variables

Abstract: Comment: Increasingly, outcome analysis will be used to determine benefit or lack of benefit of cosdy treatment protocols, especially when minimal return as measured in prolongation of life is achieved only with use of limited resources. This approach has been hampered in the past by investigators'

Postoperative Respiratory Compromise in Children with Obstructive Sleep Apnea Syndrome: Can It Be Anticipated?

Abstract: OBJECTIVE The aim of this research was to describe the postoperative respiratory complications after tonsillectomy and/or adenoidectomy (T and/or A) in children with obstructive sleep apnea syndrome (OSAS), to define which children are at risk for these complications, and to determine whether continuous positive airway pressure (CPAP) is an effective strategy for dealing with these complications. METHODS The data for this study were gathered through a retrospective chart review of all children 15 years of age or younger with polysomnographically (PSG) proven OSAS who had a T and/or A at Hennepin County Medical Center between January 1985 and September 1992. Particular attention was paid to factors that contributed to the OSAS, postoperative respiratory complications, and intervention strategies for dealing with these complications. RESULTS The charts of 37 children with OSAS documented by preoperative PSG who later had a T and/or A were reviewed retrospectively. Ten of these children had significant postoperative respiratory compromise secondary to OSAS that prolonged their hospital stay from 1 to 30 days and caused symptoms ranging from O2 desaturation < 80% to respiratory failure. These children were younger and had significant associated medical problems that contributed to or resulted from their OSAS in addition to large tonsils and adenoids. The associated medical problems included craniofacial anomalies, hypotonia, morbid obesity, previous upper airway trauma, cor pulmonale, and failure to thrive. The children with postoperative respiratory complications also had more severe apnea on their preoperative PSG. One child had a uvulopalatopharyngoplasty (UPPP) in addition to the T & A. Taken together, the history, physical and neurological examination, and the PSG were able to identify successfully the children who subsequently developed respiratory compromise secondary to OSAS after a T and/or A. Nasal continuous positive airway pressure (CPAP) and bilevel CPAP was used successfully to manage the preoperative and/or postoperative upper airway obstruction in five of these children. CONCLUSIONS Based on these findings, overnight observation is recommended with an apnea monitor and oximeter for patients undergoing a T and/or A who have OSAS and meet any of the following high-risk clinical criteria: (1) < 2 years of age, (2) craniofacial anomalies affecting the pharyngeal airway particularly midfacial hypoplasia or micro/retrognathia, (3) failure to thrive, (4) hypotonia, (5) cor pulmonale, (6) morbid obesity, and (7) previous upper airway trauma; or high-risk PSG criteria: (1) respiratory distress index (RDI) > 40 and (2) SaO2 nadir < 70%; or undergoing a UPPP in addition to the T and/or A. Nasal CPAP/bilevel CPAP can be used to manage the preoperative and/or postoperative upper airway obstruction in patients with OSAS undergoing a T and/or A.

Relation Between Myocardial Blood Flow and the Severity of Coronary-Artery Stenosis

Abstract: Comment: At rest (the condition during this study) metabolic demands of the myocardium will be the major determinant of blood flow. Thus the finding that, up to the limits of the coronary artery disease in the patients studied, basal flow was independent of degree of coronary artery stenosis is not surprising. To anesthetists, the study indicates how, in a situation in which myocardial oxygen demand is raised–tachycardia for example, a degree of stenosis that was sufficient for basal oxygen supply needs may be unable to provide flow requirements under the new conditions of oxygen supply and demand, hence the need for careful evaluation of the limited clinical evidence that most of us have of myocardial function during management of our cases. Clearly, few of us have the sophisticated tools used in this study. Only in some parts of the world is intraoperative echocardiography available. Many of us must rely on the relatively insensitive electrocardiogram or else try to avoid situations in patients with known coronary artery disease that we know increase myocardial oxygen demands. Finally, note that this study had to be limited to patients with single-vessel coronary artery disease only. Where there is multiple vessel disease, the situation is likely to be even more critical. On the other side of the coin is the reassurance that a major degree of vessel stenosis is needed before all coronary vasodilator capacity is lost.

Glucose Infusion Instead of Preoperative Fasting Reduces Postoperative Insulin Resistance

Abstract: Comment: It is not apparent from the presentation of data what amounts of glucose were given during the study. A 70-kg patient having a preoperative infusion for a 12-hr period would have received a total of 252 g of glucose. This was given as a 20% solution with 40 mmol of potassium chloride/L. In

Cerebral Metabolism During Pr??pofol Anesthesia in Humans Studied with Positron Emission Tomography

Abstract: Background Although the effects of propofol on cerebral metabolism have been studied in animals, these effects have yet to be directly examined in humans. Consequently, we used positron emission tomography (PET) to demonstrate in vivo the regional cerebral metabolic changes that occur in humans during propofol anesthesia. Methods Six volunteers each underwent two PET scans; one scan assessed awake‐baseline metabolism, and the other assessed metabolism during anesthesia with a propofol infusion titrated to the point of unresponsiveness (mean rate + SD 7.8 + 1.5 mg *symbol* kg1 *symbol* h1). Scans were obtained using the18 fluorodeoxyglucose technique. Results Awake whole‐brain glucose metabolic rates (GMR) averaged 29 + 8 micro moles *symbol* 100 g1 *symbol* min1 (mean plus/minus SD). Anesthetized whole‐brain GMR averaged 13 + 4 micro moles *symbol* 100 g1 *symbol* min1 (paired t test, P < 0.007). GMR decreased in all measured areas during anesthesia. However, the decrease in GMR was not uniform. Cortical metabolism was depressed 58%, whereas subcortical metabolism was depressed 48% (P < 0.001). Marked differences within cortical regions also occurred. In the medial and subcortical regions, the largest percent decreases occurred in the left anterior cingulate and the inferior colliculus. Conclusion Propofol produced a global metabolic depression on the human central nervous system. The metabolic pattern evident during anesthesia was reproducible and differed from that seen in the awake condition. These findings are consistent with those from previous animal studies and suggest PET may be useful for investigating the mechanisms of anesthesia in humans.

Midazolam Should Be Avoided in Patients Receiving the Systemic Antimycotics Ketoconazole or Itraconazole

Abstract: Interaction between ketoconazole, itraconazole, and midazolam was investigated in a double-blind, randomized crossover study of three phases at intervals of 4 weeks. Nine volunteers were given either 400 mg ketoconazole, 200 mg itraconazole, or matched placebo orally once daily for 4 days. On day 4, the subjects ingested 7.5 mg midazolam. Plasma samples were collected and psychomotor performance was measured. Both ketoconazole and itraconazole increased the area under the midazolam concentration-time curve from 10 to 15 times (p < 0.001) and mean peak concentrations three to four times (p < 0.001) compared with the placebo phase. In psychomotor tests (e.g., the Digit Symbol Substitution Test), the interaction was statistically significant (p < 0.05) until at least 6 hours after drug administration. Inhibition of the cytochrome P450IIIA by ketoconazole and itraconazole may explain the observed pharmacokinetic interaction. Prescription of midazolam for patients receiving ketoconazole and itraconazole should be avoided.

Rapid Increase in Desflurane Concentration Is Associated with Greater Transient Cardiovascular Stimulation than with Rapid Increase in Isoflurane Concentration in Humans

Abstract: Background:Increases in desflurane and isoflurane concentrations can transiently Increase arterial blood pressure or heart rate or both during induction of anesthesia. The current study tested the hypothesis that a rapid increase of desflurane concentration in humans increases sympathetic activity and hormonal variables and heart rate and arterial blood pressure more than does an equivalent Increase in isoflurane concentration. Methods:Twelve healthy male volunteers were assigned randomly to receive desflurane and on a separate occasion isoflurane. After induction of anesthesia with propofol 2 mg/kg, anesthesia was maintained at 0.55 MAC (desflurane, 4.0%; isoflurane 0.71% end-tidal) for 32 min. Mechanical ventilation maintained normocapnia throughout anesthesia. Mean arterial blood pressure and heart rate were recorded continuously, and arterial blood was sampled for plasma catecholamine and vasopressin (AVP) concentrations, and plasma renin activity. Anesthetic concentration was increased rapidly to 1.66 MAC (desflurane, 12.0%; isoflurane 2.12% end-tidal), and maintained at this concentration for 32 min, and then rapidly decreased to and maintained at 0.55 MAC for an additional 32 min. Results:Neither anesthetic produced sympathetic or cardiovascular stimulation during their initial rapid wash-in to 0.55 MAC. The rapid increase to 1.66 MAC increased mean arterial blood pressure, heart rate, and plasma epinephrine and nor-epinephrine concentrations, and plasma renin activity with both desflurane and isoflurane, the former usually producing a response of greater magnitude than the latter. Plasma AVP concentration increased with desflurane only. Increased mean arterial blood pressure returned to control in 4 min. Heart rate decreased 50% of the difference between its peak and the value at 32 min at 1.66 MAC in 2 min with desflurane and in 4 min with isoflurane but did not return to the value at 0.55 MAC with either anesthetic. With desflurane, plasma epinephrine and AVP concentrations decreased quickly from their peak values, remaining elevated for 8 min. Decrease of concentrations of desflurane and isoflurane from 1.66 MAC to 0.55 MAC rapidly decreased heart rate and increased mean arterial blood pressure with both anesthetics. Thirty-two minutes after return to 0.55 MAC, with both anesthetics, only heart rate remained Increased relative to the values at 32 min of the Initial period of 0.55 MAC anesthesia. Conclusions:In healthy male volunteers, rapid increases of desflurane or isoflurane from 0.55 to 1.66 MAC increase sympathetic and renin-angiotensin system activity, and cause transient increases in arterial blood pressure and heart rate. Desflurane causes significantly greater increases than isoflurane, and also causes a transient increase in plasma AVP concentration. The temporal relationships suggest that the increased sympathetic activity increases mean arterial blood pressure and heart rate, with mean arterial blood pressure also increased by increased plasma AVP concentration, whereas the delayed, increased plasma renin activity is likely a response to the ensuing hypotension, or earlier inhibition by AVP, or both.

Promotion of Women Physicians in Academic Medicine: Glass Ceiling or Sticky Floor?

Abstract: Objective. —To assess possible explanations for the finding that the percentage of women medical school faculty members holding associate or full professor rank remains well below the percentage of men. Design. —Cross-sectional survey of physician faculty of US medical schools using the Association of American Medical Colleges (AAMC) database. Subjects. —Surveyed were 153 women and 263 men first appointed between 1979 and 1981, matched for institutions of original faculty appointment. Main Outcome Measures. —Academic rank achieved, career preparation, academic resources at first appointment, familial responsibilities, and academic productivity. Results. —After a mean of 11 years on a medical school faculty, 59% of women compared with 83% of men had achieved associate or full professor rank, and 5% of women compared with 23% of men had achieved full professor rank. Women and men reported similar preparation for an academic career, but women began their careers with fewer academic resources. The number of children was not associated with rank achieved. Women worked about 10% fewer hours per week and had authored fewer publications. After adjustment for productivity factors, women remained less likely to be associate or full professors (adjusted odds ratio [OR]=0.37; 95% confidence interval [CI], 0.21 to 0.66) or to achieve full professor rank (adjusted OR=0.27; 95% CI, 0.12 to 0.63). Based on the AAMC database, 50% of both women and men originally appointed as faculty members between 1979 and 1981 had left academic medicine by 1991. Conclusion. —Women physician medical school faculty are promoted more slowly than men. Gender differences in rank achieved are not explained by productivity or by differential attrition from academic medicine. (JAMA. 1995;273:1022-1025)

The Decline in Coronary Artery Bypass Graft Surgery Mortality in New York State: The Role of Surgeon Volume

Abstract: Objective. —To examine the longitudinal relationship between surgeon volume and in-hospital mortality for coronary artery bypass graft (CABG) surgery in New York State and to explain changes in mortality that occurred over time. Design. —Observation of clinically risk-adjusted operative mortality over time. Setting. —All 30 New York State hospitals in which CABG surgery was performed for 1989 through 1992. Patients. —All 57187 patients undergoing isolated CABG surgery in New York State in 1989 through 1992 in the 30 hospitals. Main Outcome Measures. —Actual, expected, and risk-adjusted mortality. Results. —Risk-adjusted in-hospital mortality decreased for all categories of surgeons. Low-volume surgeons (≤50 operations per year) experienced a 60% reduction in risk-adjusted mortality in the 4-year period, whereas the highest-volume surgeons (>150 operations per year) experienced a 34% reduction. The percentage of patients undergoing CABG surgery by low-volume surgeons decreased from 7.6% in 1989 to 5.7% in 1992, a 25% decrease. Conclusions. —The overall decline in risk-adjusted mortality could not be explained by shifts in patients away from low-volume surgeons to high-volume surgeons. The proportionately larger decrease in risk-adjusted mortality for low-volume surgeons could not be explained by changes in patient case mix or by improvements in the performance of surgeons with persistently low volumes. Part of the decrease was a result of the exodus of low-volume surgeons with high risk-adjusted mortality (in all years studied), the markedly better performance of surgeons who were new to the system (especially in 1991 and 1992), and the performance of surgeons who were not consistently low-volume surgeons (especially in 1992). (JAMA. 1995;273:209-213)

The Catecholamine, Cortisol, and Hemodynamic Responses to Mild Perioperative Hypothermia: A Randomized Clinical Trial

Abstract: Background Unintended hypothermia occurs frequently during surgery and may have adverse effects on the cardiovascular system. Although the mechanisms responsible for the cardiovascular manifestations of hypothermia are unclear, it is possible that they are sympathetically mediated. In this prospective study, relationships between body temperature, the neuroendocrine response, and hemodynamic changes in the perioperative period were examined. Methods Seventy‐four elderly patients, undergoing abdominal, thoracic, or lower extremity vascular surgical procedures, were randomly assigned to either “routine care” (n = 37) or “forced‐air warming” (n = 37) groups. Throughout the intraoperative and early postoperative periods, the routine care group received standard thermal care, and the forced‐air warming group received forced‐air skin‐surface warming. Core temperature, forearm minus fingertip skin‐surface temperature gradient, and plasma concentrations of epinephrine, norepinephrine, and cortisol were measured throughout the perioperative period, and the two groups were compared. In addition, heart rate and arterial blood pressure were compared between groups. Results The routine care and forced‐air warming groups did not differ with regard to age, sex, type of surgical procedures, anesthetic techniques, or postoperative analgesia. Mean core temperature was lower in the routine care group on admission to the postanesthetic care unit (routine care, 35.3 plus/minus 0.1 degree Celsius; forced‐air warming, 36.7 plus/minus 0.1 degree Celsius; P = 0.0001) and remained lower during the early postoperative period. Forearm minus fingertip skin‐surface temperature gradient (an index of peripheral vasoconstriction) was greater in the routine care group in the early postoperative period. The mean norepinephrine concentration (pcg/ml) was greater in the routine care group immediately after surgery (480 plus/minus 70 vs. 330 plus/minus 30, P = 0.02) and at 60 min (530 plus/minus 50 vs. 340 plus/minus 30, P = 0.002) and 180 min (500 plus/minus 80 vs. 320 plus/minus 30, P = 0.004) postoperatively. Mean epinephrine concentrations were not significantly different between groups. Mean cortisol concentrations were increased in both groups during the early postoperative period (P < 0.01), but the differences between groups were not significant. Systolic, mean, and diastolic arterial blood pressures were significantly higher in the routine care group. Conclusions Compared with patients in the forced‐air warming group, patients receiving routine thermal care had lower core temperatures, a greater degree of peripheral vasoconstriction, higher norepinephrine concentrations, and higher arterial blood pressures in the early postoperative period. These findings suggest a possible mechanism for hypothermia‐related cardiovascular morbidity in the perioperative period.

Improved Survival of Patients with Acute Respiratory Distress Syndrome (ARDS): 1983???1993

Abstract: Objective. —To analyze temporal trends in acute respiratory distress syndrome (ARDS) fatality rates since 1983 at one institution. Design. —Cohort. Setting. —Intensive care units of a large county hospital. Patients. —Consecutive adult patients (≥18 years of age) meeting ARDS criteria were identified through daily surveillance of intensive care units (N=918 from 1983 through 1993). The major causes were sepsis syndrome in 37% and major trauma in 25%; 37% had other risks. Sixty-five percent were male. The median age was 45 years (range, 18 to 92 years); 70% were younger than 60 years. Main Outcome Measure. —Hospital mortality. Results. —Overall fatality rates showed no trend from 1983 to 1987, declined slightly in 1988 and 1989, and decreased to a low of 36% in 1993 (95% confidence interval, 25% to 46%). The crude rates were largely unchanged after adjustment for age, ARDS risk, and gender distribution. While patients both younger than 60 years and 60 years or older experienced declines in fatality rate, the larger decrease occurred in the younger cohort. In sepsis patients, ARDS fatality rates declined steadily, from 67% in 1990 to 40% in 1993 (95% confidence interval, 23% to 57%). The decline in sepsis-related ARDS fatality was confined largely to patients less than 60 years of age. Trauma patients and all other patients also experienced declines in fatality rates after 1987, although these trends were not as strong and consistent as in the sepsis population. Conclusions. —In this large series, we observed a significant decrease in fatality rates occurring largely in patients younger than 60 years and in those with sepsis syndrome as their risk for ARDS. We are unable to determine the extent to which experimental therapies or other changes in treatment have contributed to the observed decline in the ARDS fatality rate. Institution-specific rates and temporal trends in ARDS fatality rates should be considered in clinical trials designed to prevent ARDS and the high mortality associated with this syndrome. ( JAMA . 1995;273:306-309)

ASA Physical Status and Age Predict Morbidity after Three Surgical Procedures

Abstract: OBJECTIVE: American Society of Anesthesiologists-Physical Status scores (ASA-PS) and age were used to adjust for case-mix differences when evaluating surgical morbidity and resource use after total hip replacement (THR), transurethral prostatectomy (TURP), or cholecystectomy. SUMMARY BACKGROUND DATA: Variations in complication rates or resource use among patients treated for a particular primary condition should be adjusted for coexistent disease. Age and ASA-PS scores are readily available and can be useful to stratify surgical patients for risk. METHODS: One thousand ninety patients at five academic medical centers in California and Massachusetts who underwent THR, TURP, or cholecystectomy between 1985 and 1987 were studied. Data were obtained from medical records and a self-administered questionnaire to measure length of stay (LOS), postoperative complication rates, and follow-up physician visits. Data were analyzed with one- and two-way analysis of variance with the Bonferroni correction. RESULTS: Increasing age and ASA-PS scores were associated significantly with increased LOS, complication rates, and frequency of post-discharge physician office visits. No interaction effect between age and ASA-PS scores was observed. CONCLUSIONS: Age and ASA-PS scores can predict postoperative morbidity, specific for each operation studied. Assessment of co-morbidity in surgical patients can be accomplished easily and with minimal expense. While remaining budget neutral, the distribution of reimbursements should be based on those preoperative risk factors that predict longer LOS and higher complication rates.

Diuretic Therapy for Hypertension and the Risk of Primary Cardiac Arrest

Abstract: Background The results of trials of the primary prevention of coronary heart disease have suggested that treating hypertension with high doses of thiazide diuretic drugs might increase the risk of sudden death from cardiac causes. In contrast, treatment with low doses of thiazide reduces the risk of coronary heart disease. Methods To examine the association between thiazide treatment for hypertension and the occurrence of primary cardiac arrest, we conducted a population-based case-control study among enrollees of a health maintenance organization. The case patients were 114 persons with hypertension who had a primary cardiac arrest from 1977 through 1990. The control patients were a stratified random sample of 535 persons with hypertension. The patients' treatment was assessed with the use of a computerized pharmacy data base. Records of their ambulatory care were reviewed to determine other clinical characteristics. Results The risk of primary cardiac arrest among patients receiving combined thiazide an...

Influence of Thoracic Epidural Analgesia on Outcome after Resection for Esophageal Cancer

Abstract: Background Many series have reported a lessening of the incidence of anastomotic dehiscence after thoracoabdominal resection of esophageal carcinomata. This has resulted in fatal respiratory complications assuming a relatively greater role as a cause of death after such procedures. This study was conducted to investigate the impact of the routine use of thoracic epidural analgesia on respiratory complications after resection for esophageal carcinoma. Methods The incidence of respiratory complications and the effect on outcome were studied in two groups of patients undergoing thoracoabdominal esophagogastrectomy for esophageal cancer during a 15-year period. The first group comprised 81 patients who underwent operation from 1975 through 1985 in whom thoracic epidural analgesia was not used; the second group comprised 75 patients who underwent operation from 1985 through 1990 in whom thoracic epidural analgesia was used routinely. Results In the latter group, the incidence of respiratory complications was 13%, and no fatal respiratory complications occurred, compared with corresponding figures of 30% and 5% in the nonepidural group. The 30-day/hospital mortality during the first period was 9.8% and 6.6% in the 75 patients in whom thoracic epidural analgesia was used routinely. Conclusions The results of this study suggest that the routine use of thoracic epidural analgesia during thoracoabdominal esophagogastrectomy for esophageal cancer reduces the incidence of fatal and nonfatal respiratory complications and should be incorporated into routine surgical management of operable esophageal cancer.

Determinants in Canadian Health Care Workers of the Decision to Withdraw Life Support from the Critically Ill

Abstract: OBJECTIVE To examine the attitudes of health care workers regarding the withdrawal of life support. DESIGN Cross-sectional survey. PARTICIPANTS Attending staff, house staff, and intensive care unit (ICU) nurses in 37 Canadian university-affiliated hospitals. MAIN OUTCOME MEASURES Health care workers' ratings of the importance of 17 factors considered in the decision to withdraw life support, and their ratings of five levels of care ranging from comfort measures to intensive care in two of 12 different clinical scenarios. RESULTS We surveyed 1361 respondents (149 of 167 potentially eligible ICU attending staff, 142 of 173 ICU house staff, and 1070 of 1455 ICU nurses, with response rates of 89%, 82% and 74%, respectively). The most important factors were likelihood of surviving the current episode, likelihood of long-term survival, premorbid cognitive function, and age of the patient. In choosing the level of care for the patient scenarios, the same option was chosen by more than 50% of respondents in only one of 12 scenarios; opposite extremes of care were chosen by more than 10% of the respondents in eight of 12 scenarios. Respondent characteristics affecting choices included the number of years since graduation, the city and province in which they worked, the number of beds in their ICU, and their assessment of the likelihood that they would withdraw life support in comparison with their colleagues (P < .001 for all comparisons). CONCLUSIONS While ICU health care workers consistently identify a number of patient factors as important in decisions to withdraw care, there is extreme variability, which may be explained in part by the values of individual health care providers.

Local Anesthetics Inhibit Substance P Binding and Evoked Increases in Intracellular Ca2

Abstract: BACKGROUND During spinal and epidural anesthesia, local anesthetics reach concentrations in cerebrospinal fluid and spinal cord tissues at which their actions may extend beyond the classic blockade of sodium channels. This study examines the effects of several clinical and experimental local anesthetics on the binding and actions of a peptide neurotransmitter, substance P, known to be important in nociceptive transmission in the dorsal horn. METHODS The binding of radiolabeled (Bolton-Hunter modified) substance P was studied in chick brain membranes in the presence of local anesthetics. The increase in intracellular calcium [Ca2+]in evoked by substance P was measured by the fluorescent indicator fura-2 loaded in a murine cell line expressing substance P (NK1) receptors. Cells were preincubated with bupivacaine before and during the transient addition of substance P. RESULTS Both substance P binding and Ca2+ increase were inhibited half-maximally by approximately 1 mM bupivacaine at pH 7.5, whereas tetracaine, lidocaine, and benzocaine were slightly less potent at inhibiting binding. Concentration-dependent substance P-binding studies showed that bupivacaine's inhibition was not competitive. Inhibition of substance P binding by bupivacaine increased with increasing pH, but the protonated species appears to have some inhibitory activity, and quaternary lidocaine also inhibited binding. There was no stereoselectively to the binding inhibition. CONCLUSIONS Because millimolar concentrations of local anesthetics are within the range measured in spinal cord during intrathecal and epidural procedures, these results are consistent with a direct action of local anesthetics on tachykinin-mediated neurotransmission during regional anesthesia.

Impact of Quality-of-care Factors on Pediatric Intensive Care Unit Mortality

Abstract: OBJECTIVE To determine the importance of the following care factors previously associated with hospital quality on survival from pediatric intensive care: size of the intensive care unit (ICU), medical school teaching status of the hospital housing the ICU, specialist status (pediatric intensivist), and unit coordination. DESIGN After a national survey, consecutive case series were collected at 16 sites randomly selected to represent unique combinations of quality-of-care factors. SETTING Pediatric ICUs. PATIENTS Consecutive admissions to each site. MAIN OUTCOME MEASURE Patient mortality adjusted for physiologic status, diagnosis, and other mortality risk factors. RESULTS There were 5415 pediatric ICU admissions and 248 ICU deaths. The ICUs differed significantly with respect to descriptive variables, including mortality (range, 2.2% to 16.4%). Analysis of risk-adjusted mortality indicated that the hospital teaching status and the presence of a pediatric intensivist were significantly associated with a patient's chance of survival. The probability of patient survival after hospitalization in an ICU located in a teaching hospital was decreased (relative odds of dying, 1.79; 95% confidence interval [CI], 1.23 to 2.61; P = .002). In contrast, the probability of patient survival after hospitalization in an ICU with a pediatric intensivist was improved (relative odds of dying, 0.65; 95% CI, 0.44 to 0.95; P = .027). Post hoc analysis indicated that the higher severity-adjusted mortality in teaching hospitals may be explained by the presence of residents caring for ICU patients. CONCLUSION Characteristics indicative of the best overall hospital quality may not be associated, or may be negatively associated, with quality of care in specialized care areas, including the pediatric ICU.

Analgesic and Neurotoxic Effects of Intrathecal Corticosteroids in Rats

Abstract: BACKGROUND Despite the widespread use of epidurally administered corticosteroids in the treatment of sciatica and the failure of animal studies to demonstrate neurotoxicity from epidermally administered corticosteroids, controversy remains regarding the mechanism of action as well as the safety of this treatment. The goal of this study was to determine whether spinally administered corticosteroids have any analgesic effects, and whether repeated intrathecal administration causes any neuronal damage to the spinal cord. METHODS Chronic lumbar intrathecal catheters were implanted in rats. Formalin testing was carried out 1 h after the intrathecal administration of 400 micrograms methylprednisolone sodium succinate, 48 h after intrathecal administration of triamcinolone diacetate 250 micrograms, or 24 h after the last of a series of four injections of triamcinolone diacetate 250 micrograms given at 5-day intervals. Histologic sections of multiple levels of spinal cord from the animals receiving repeat intrathecal steroid injections were compared to those from animals that received intrathecal saline at the same intervals. RESULTS The animals receiving repeated intrathecal triamcinolone diacetate demonstrated mild, statistically significant reduction of pain behavior (hindlimb flinching) during the second but not the first phase of the formalin test when compared to controls. No analgesic effects were demonstrated after methylprednisolone sodium succinate or a single injection of triamicinolone diacetate. Animals that received methylprednisolone sodium succinate demonstrated transient segmental allodynia. No behavioral or neurologic abnormalities were seen in any other group. Some histologic evidence neuronal damage (the presence of argyrophilic neurons was seen in the chronically implanted animals in areas of the cord adjacent to the spinal catheters, but there was no difference in incidence of these changes between the steroid and control groups. CONCLUSIONS Intrathecal steroid injections have no analgesic effect and do not suppress spinal sensitization when administered acutely. After chronic administration, there is a mild effect on nociceptor-driven spinal sensitization (phase 2 of the formalin test), but no analgesic effect on an acute noxious stimulus (phase 1 of the formalin test). Repeated intrathecal administration of triamcinolone diacetate (0.8 mg/kg) is not associated with spinal neurotoxic effects during the time period studied.

Cerebral Oxygenation During Pediatric Cardiac Surgery Using Deep Hypothermia Circulatory Arrest

Abstract: Background Deep hypothermic circulatory arrest is a widely used technique in pediatric cardiac surgery that carries a risk of neurologic injury. Previous work in neonates identified distinct changes in cerebral oxygenation during surgery. This study sought to determine whether the intraoperative changes in cerebral oxygenation vary between neonates, infants, and children and whether the oxygenation changes are associated with postoperative cerebral dysfunction. Methods The study included eight neonates, ten infants, and eight children without preexisting neurologic disease. Cerebrovascular hemoglobin oxygen saturation (ScO2), an index of brain oxygenation, was monitored intraoperatively by near‐infrared spectroscopy. Body temperature was reduced to 15 degrees Celsius during cardiopulmonary bypass (CPB) before commencing circulatory arrest. Postoperative neurologic status was judged as normal or abnormal (seizures, stroke, coma). Results Relative to preoperative levels, the age groups experienced similar changes in ScO2 during surgery: Sco sub 2 increased 30 plus/minus 4% during deep hypothermic CPB, it decreased 62 plus/minus 5% by the end of arrest, and it increased 20 plus/minus 5% during CPB recirculation (all P < 0.001); after rewarming and removal of CPB, ScO2 returned to preoperative levels. During arrest, the half‐life of ScO2 was 9 plus/minus 1 min in neonates, 6 plus/minus 1 min in infants, and 4 plus/minus 1 min in children (P < 0.001). Postoperative neurologic status was abnormal in three (12%) patients. The ScO2 increase during deep hypothermic CPB was less in these patients than in the remaining study population (3 plus/minus 2% versus 33 plus/minus 4%, P < 0.00l). There were no other significant ScO2 differences between outcome groups. Conclusions Brain oxygenation changed at distinct points during surgery in all ages, reflecting fundamental cerebral responses to hypothermic CPB, ischemia, and reperfusion. However, the changes in Sc sub O2 half‐life with age reflect developmental differences in the rate of cerebral oxygen utilization during arrest, consistent with experimental work in animals. Certain intraoperative cerebral oxygenation patterns may be associated with postoperative cerebral dysfunction and require further study.

Intrathecal Administration of Oxytocin Induces Analgesia in Low Back Pain Involving the Endogenous Opiate Peptide System

Abstract: Study Design.The effect of oxytocin on low back pain in patients and its mechanism in rats were investigated.Methods.Intrathecal injection, radioimmunoassay, and potassium lontophoresis tail-flick test were used to investigate the effect of oxytocin.Results.In humans, acute and chronic low back pain

Intrathecal Magnesium Sulfate Protects the Spinal Cord from Ischemic Injury During Thoracic Aortic Cross Clamping

Abstract: BACKGROUND: Paraplegia is a known complication after surgery on the descending thoracic aorta. Thoracic aortic cross-clamping causes an increase in proximal aortic and cerebrospinal fluid pressures. Sodium nitroprusside, though effectively decreasing proximal aortic pressure, has been implicated in worsening the incidence of paraplegia by further increasing cerebrospinal fluid pressure and decreasing distal blood pressure, thereby reducing spinal cord perfusion pressure. Intravenous administration of magnesium sulfate has been shown to offer some spinal cord protection when used with mild hypothermia. This study investigated the effect of intrathecal magnesium on the prevention of paraplegia when sodium nitroprusside is used to control proximal hypertension during thoracic aortic cross-clamping in a dog model of spinal cord ischemia. METHODS: Two groups of eight dogs underwent thoracic aortic cross-clamping via a small thoracotomy incision for 45 min. Proximal, distal, and central venous pressures and cerebrospinal fluid pressures were monitored. Temperature was maintained at 36 degrees C. Sodium nitroprusside was used to control proximal hypertension. The control group received no magnesium sulfate, and a second group received 3 mg/kg intrathecal magnesium sulfate before thoracic aortic cross-clamping. The dogs were neurologically evaluated 24 h later by an observer blinded to the dogs' group. Spinal cord segments were obtained for histologic examination. RESULTS: Proximal mean arterial pressure, cerebrospinal fluid pressure, spinal cord perfusion pressure, and central venous pressure were not statistically different between the two groups. Neurologic outcome, however, was statistically different between the groups. None of the eight dogs in the magnesium group had any measurable neurologic injury, in contrast to the control group, in which seven of the eight dogs had severe neurologic injury (P < 0.005). Post mortem histologic data supported these findings. CONCLUSIONS: Intrathecal magnesium can prevent spinal cord injury despite markedly negative spinal cord perfusion pressure during thoracic aortic cross-clamping in a canine model of spinal cord ischemia.

The Addition of 7.5% Glucose Does Not Alter the Neurotoxicity of 5% Lidocaine Administered Intrathecally in the Rat

Abstract: BACKGROUND: Recent reports of major and minor neurologic sequelae after spinal anesthesia have generated concern regarding the safety of some currently used intrathecal agents. The role of glucose, if any, in neurotoxic injury associated with spinal anesthesia is not known. The current experiments sought to determine whether the presence of 7.5% glucose alters the neurotoxicity of intrathecally administered 5% lidocaine. METHODS: Two experiments were performed. First, 48 rats were implanted with an intrathecal catheter and randomly divided into eight equal groups. Each animal received a single intrathecal infusion of 5% lidocaine (groups P1-P4) or 5% lidocaine with 7.5% glucose (G1-G4) for 0.5, 1, 2, or 4 h at a rate of 1 microliter/min. Sensory function was assessed using the tail-flick test; a deficit was defined as a complete lack of response to the heat stimulus at the proximal, mid or distal portion of the tail persisting 4 days after the infusion. In the second experiment, 60 rats were randomly divided into two groups to receive a 1-h intrathecal infusion of 5% lidocaine or 5% lidocaine with 7.5% glucose. Animals were evaluated for increase in the latency of the tail-flick reflex 4 days after infusion. RESULTS: In the first experiment, the two lidocaine solutions produced similar dose-dependent loss of sensory function. In the second experiment, the two solutions induced similar alterations in tail-flick latency. CONCLUSIONS: The presence of 7.5% glucose does not affect the potential of intrathecally administered 5% lidocaine to induce sensory impairment. These findings provide further support for the hypothesis that recent injuries after spinal anesthesia resulted from a direct neurotoxic effect of the local anesthetic.

The Influence of Anesthetic Technique on Perioperative Complications after Carotid Endarterectomy

Abstract: PURPOSE This study evaluated the influence of anesthetic techniques on perioperative complications after carotid endarterectomy. METHODS Perioperative complications, the use of a carotid artery shunt, the duration of the operative procedure and postoperative hospital course were retrospectively compared in 584 consecutive patients undergoing 679 carotid endarterectomies with use of either general anesthesia (n = 361) or cervical block regional anesthesia (n = 318). There was no significant difference in the preoperative medical characteristics between the two anesthetic groups. Symptomatic carotid artery disease was the indication for surgery in 247 (68.4%) patients receiving general anesthetics, whereas 180 (56.6%) patients treated with a cervical block anesthetic had a symptomatic carotid artery stenosis (p = 0.02). RESULTS The perioperative stroke rate and stroke-death rate for the entire series was 2.4% and 3.2%, respectively, and was not significantly different between the anesthetic groups or between patients with symptomatic or asymptomatic disease. A carotid artery shunt was used in 61 (19.2%) patients receiving a cervical block anesthetic and 152 (42.1%) patients treated with a general anesthetic (p < 0.0001). Use of cervical block anesthesia was associated with a significantly shorter operative time, fewer perioperative cardiopulmonary complications, and a shorter postoperative hospitalization when compared with general anesthesia. Multivariate risk factor analysis indicated that age greater than 75 years, operative time greater than 3 hours, and the use of a carotid artery shunt were all independent risk factors for perioperative cardiopulmonary complications. When a carotid artery shunt was not analyzed as a multivariate risk factor, then general anesthesia became a significant risk factor for perioperative cardiopulmonary complications (risk ratio 2.08; p = 0.04). CONCLUSIONS We conclude that cervical block anesthesia is safer and results in a more efficient use of hospital resources than general anesthesia in the treatment of patients undergoing carotid endarterectomy.

Delayed Gastric Emptying of Both the Liquid and Solid Components of a Meal in Chronic Liver Disease

Abstract: OBJECTIVES To evaluate gastric emptying in patients with chronic liver disease and portal hypertension. METHODS We measured gastric emptying of both the liquid and solid components of a meal in 10 consecutive patients with chronic liver disease and portal hypertension, but free of ascites, and 14 age- and sex-matched healthy controls. In the patients with liver disease, relationships between emptying and liver function were examined. To measure gastric emptying, subjects consumed a test meal that consisted of scrambled eggs labeled with 99mTc-sulfur colloid and 4 oz of water labeled with 111In-diethylene triamine pentacetic acid (DTPA). RESULTS Patients with liver disease and portal hypertension demonstrated delayed emptying of both the liquid (t1/2, min, mean +/- SE, patients vs. CONTROLS 69.4 +/- 19.4 vs. 31.4 +/- 1.8, p < 0.01) and solid (post-lag phase solid emptying: 141 +/- 32.9 vs. 69.8 +/- 4.6, p < 0.006) components of the meal. We could not identify any correlation between gastric emptying and tests of liver function. CONCLUSIONS Gastric emptying is delayed in patients with liver disease and portal hypertension; this abnormal gastric motor function may contribute to the pathophysiology of foregut complaints in this patient population.

A Longitudinal Study of Cardiac Output in Normal Human Pregnancy

Abstract: OBJECTIVE: Our purpose was to investigate the maternal hemodynamic and cardiac structural changes that occur during pregnancy. STUDY DESIGN: Eighteen women underwent serial echocardiography beginning at 8 to 11 weeks' gestation, then at monthly intervals throughout pregnancy and at 6 and 12 weeks post partum. Cardiac output was measured by pulsed-and continuous-wave Doppler at the aortic valve. Left ventricular chamber size, wall thickness, and mass were determined by M-mode echocardiography. Ventricular diastolic function was assessed by Doppler recording of mitral inflow. RESULTS: Cardiac output by pulsed Doppler increased from 6.7 ± 0.9 L/min at 8 to 11 weeks' gestation to 8.7 ± 1.4 L/min at 36 to 39 weeks' gestation before falling to 5.7 ± 0.7 L/min 12 weeks post partum. Heart rate increased 29%, and stroke volume increased 18%. Left ventricular mass increased because of an increase in wall thickness. Peak mitral A wave velocity increased in late pregnancy. Cardiac output by pulsed and continuous-wave Doppler was similar. CONCLUSION: Cardiac output continues to increase even in late pregnancy. Left ventricular mass increases because of increased wall thickness. The mitral flow velocity findings suggest decreased ventricular compliance or increased preload. (AM J OBSTET GYNECOL 1994;170:849-56.)

Prediction of Difficult Tracheal Intubation

Abstract: Three hundred and fifty consecutive patients (322 non-obstetric, 28 obstetric; 185 female) were assessed before operation using the modified Mallampati test and by measuring thyromental and sternomental distances, forward protrusion of the mandible and interincisor gap with the mouth fully open. Tracheal intubation was difficult in 17(4.9%) patients, of whom four (1.14%) had a grade III or IV view on laryngoscopy. A sternomental distance of 12.5 cm or less with the head fully extended on the neck and the mouth closed predicted 14 of the 17 patients in whom tracheal intubation was difficult. As a screening test, sternomental distance appeared to be more sensitive (82.4%) and more specific (88.6%) than thyromental distance (64.7% and 81.4%, respectively), the modified Mallampati test (64.7% and 66.1%, respectively) and forward protrusion of the mandible (29.4% and 85.0%, respectively). The interincisor gap ranged from 2.0 to 5.0 cm in all patients except one. There was no correlation between the interincisor gap and the view on laryngoscopy ( P > 0.05, one-way ANOVA). There was also no difference in mean interincisor gap between those patients who presented no difficulty with tracheal intubation and those who did ( P = 0.7–0.8, two sample t test). Sternomental distance may be a useful bedside screening test for preoperative prediction of difficult tracheal intubation.