John Collins Warren and his act of conscience: a brief narrative of the trial and triumph of a great surgeon. (1/916)

On examination of the correspondence among the principals involved, as well as the original patent application being prepared by Morton, it has become possible to reconstruct some of the remarkable details attending the first use of ether anesthesia at the Massachusetts General Hos pital in the autumn of 1846. At the time that Warren invited Morton to demonstrate the use of his "ethereal vapor" for anesthesia in a minor operation on Oct. 16, 1846, the exact chemical composition of the agent used was being held secret by Morton; Warren was clearly disturbed by this unethical use of a secret "nostrum." When the time arrived 3 weeks later for its possible use for a serious "capital" operation, Warren employed a simple stratagem of public confrontation to discover from Morton the true nature of the substance to be used. On being informed that it was pure unadulterated sulfuric ether, not some mysterious new discovery labeled "Letheon," Warren gave approval for its first use in a "capital" operation (low thigh amputation) on Nov. 7, 1846. Despite this revelation to the immediate participants, a veil of secrecy continued to surround the substance for many months, an anomalous situation evidently traceable to Morton's desire for personal reward from the discovery. It was this matter of secrecy, rather than priority for its discovery, that surrounded the early use of ether anesthesia with controversy and recrimination both in this country and abroad.  (+info)

Inadvertent inhalation anaesthesia during surgery under retrobulbar eye block. (2/916)

I describe a case of inadvertent inhalation anaesthesia during surgery under retrobulbar anaesthesia and its management. Some of the hazards of supplementary oxygen delivery during monitored anaesthetic care and the actions taken to prevent this mishap recurring are discussed.  (+info)

Individualized feedback of volatile agent use reduces fresh gas flow rate, but fails to favorably affect agent choice. (3/916)

BACKGROUND: Cost reduction has become an important fiscal aim of many hospitals and anesthetic departments, despite its inherent limitations. Volatile anesthetic agents are some of the few drugs that are amenable to such treatment because fresh gas flow rate (FGFR) can be independent of patient volatile anesthetic agent requirement. METHODS: FGFR and drug use were recorded at the temporal midpoint of 2,031 general anesthetics during a 2-month preintervention period. Staff and residents were provided with their preintervention individual mean FGFR, their peer group mean, and educational material regarding volatile agent costs and low-flow anesthesia. FGFR and drug use were remeasured over a 2-month period (postintervention) immediately after this information (N = 2,242) and again 5 months later (delayed follow-up), for a further 2-month period (N = 2,056). RESULTS: For all cases, FGFR decreased from 2.4+/-1.1 to 1.8+/-1.0 l/min (26% reduction) after the intervention and increased to 1.9+/-1.1 l/min (5% increase of preintervention FGFR) at the time of delayed follow-up. Use of more expensive volatile agents (desflurane and sevoflurane) increased during the study period (P < 0.01). In a subgroup of 44 staff members with more than five cases in all study periods, 42 members decreased their mean FGFR after intervention. At delayed follow-up, 30 members had increased their FGFR above postintervention FGFR but below their initial FGFR. After accounting for other predictors of FGFR, the effectiveness of the intervention was significantly reduced at follow-up (28% reduction), but retained a significant effect compared to preintervention FGFR (19% reduction). CONCLUSIONS: Although individual feedback and education regarding volatile agent use was effective at reducing FGFR, effectiveness was reduced without continued feedback. Use of more expensive volatile agents was not reduced by education regarding drug cost, and actually increased.  (+info)

Effect of sevoflurane concentration on inhalation induction of anaesthesia in the elderly. (4/916)

We have conducted a randomized, double-blind comparison of 4% and 8% sevoflurane for induction of anaesthesia in unpremedicated patients aged more than 60 yr. Sevoflurane was inhaled in 50% nitrous oxide using a vital capacity breath technique, and mean, systolic and diastolic arterial pressures and heart rate were monitored continuously using a Finapres cuff. In the 8% sevoflurane group, time to successful laryngeal mask insertion was significantly shorter (mean 168 (SD 34) s vs 226 (62) s; P < 0.01) and achieved more often at the first attempt than in the 4% sevoflurane group. Arterial pressures were lower in the 8% group, but this was not significant. No patient had apnoea lasting longer than 1 min. A total of 69% of patients described induction as pleasant and 85% would choose to have it again. We conclude that compared with 8% sevoflurane, the use of 4% sevoflurane in the elderly resulted in greater cardiovascular stability but at the cost of prolonged and occasionally unsuccessful induction.  (+info)

The effect of pyrogen administration on sweating and vasoconstriction thresholds during desflurane anesthesia. (5/916)

BACKGROUND: General anesthetics increase the sweating-to-vasoconstriction interthreshold range (temperatures not triggering thermoregulatory defenses), whereas fever is believed to only increase the setpoint (target core temperature). However, no data characterize thresholds (temperatures triggering thermoregulatory defenses) during combined anesthesia and fever. Most likely, the combination produces an expanded interthreshold range around an elevated setpoint. The authors therefore tested the hypothesis that thermoregulatory response thresholds during the combination of fever and anesthesia are simply the linear combination of the thresholds resulting from each intervention alone. METHODS: The authors studied eight healthy male volunteers. Fever was induced on the appropriate days by intravenous injection of 30 IU/g human recombinant interleukin 2 (IL-2), followed 2 h later by an additional 70 IU/g. General anesthesia consisted of desflurane 0.6 minimum alveolar concentration (MAC). The volunteers were randomly assigned to the following groups: (1) control (no desflurane, no IL-2); (2) IL-2 alone; (3) desflurane alone; and (4) desflurane plus IL-2. During the fever plateau, volunteers were warmed until sweating was observed and then cooled to vasoconstriction. Sweating was evaluated from a ventilated capsule and vasoconstriction was quantified by volume plethysmography. The tympanic membrane temperatures triggering significant sweating and vasoconstriction identified the respective response thresholds. Data are presented as the mean +/- SD; P < 0.05 was considered significant. RESULTS: The interthreshold range was near 0.40 degrees C on both the control day and during IL-2 administration alone. On the IL-2 alone day, however, the interthreshold range was shifted to higher temperatures. The interthreshold range increased significantly during desflurane anesthesia to 1.9+/-0.6 degrees C. The interthreshold range during the combination of desflurane and IL-2 was 1.2+/-0.6 degrees C, which was significantly greater than on the control and IL-2 alone days. However, it was also significantly less than during desflurane alone. CONCLUSION: The combination of desflurane and IL-2 caused less thermoregulatory inhibition than would be expected based on the effects of either treatment alone. Fever-induced activation of the sympathetic nervous system may contribute by compensating for a fraction of the anesthetic-induced thermoregulatory impairment.  (+info)

Relative contribution of skin and core temperatures to vasoconstriction and shivering thresholds during isoflurane anesthesia. (6/916)

BACKGROUND: Thermoregulatory control is based on both skin and core temperatures. Skin temperature contributes approximately 20% to control of vasoconstriction and shivering in unanesthetized humans. However, this value has been used to arithmetically compensate for the cutaneous contribution to thermoregulatory control during anesthesia--although there was little basis for assuming that the relation was unchanged by anesthesia. It even remains unknown whether the relation between skin and core temperatures remains linear during anesthesia. We therefore tested the hypothesis that mean skin temperature contributes approximately 20% to control of vasoconstriction and shivering, and that the contribution is linear during general anesthesia. METHODS: Eight healthy male volunteers each participated on 3 separate days. On each day, they were anesthetized with 0.6 minimum alveolar concentrations of isoflurane. They then were assigned in random order to a mean skin temperature of 29, 31.5, or 34 degrees C. Their cores were subsequently cooled by central-venous administration of fluid at approximately 3 degrees C until vasoconstriction and shivering were detected. The relation between skin and core temperatures at the threshold for each response in each volunteer was determined by linear regression. The proportionality constant was then determined from the slope of this regression. These values were compared with those reported previously in similar but unanesthetized subjects. RESULTS: There was a linear relation between mean skin and core temperatures at the vasoconstriction and shivering thresholds in each volunteer: r2 = 0.98+/-0.02 for vasoconstriction, and 0.96+/-0.04 for shivering. The cutaneous contribution to thermoregulatory control, however, differed among the volunteers and was not necessarily the same for vasoconstriction and shivering in individual subjects. Overall, skin temperature contributed 21+/-8% to vasoconstriction, and 18+/-10% to shivering. These values did not differ significantly from those identified previously in unanesthetized volunteers: 20+/-6% and 19+/-8%, respectively. CONCLUSIONS: The results in anesthetized volunteers were virtually identical to those reported previously in unanesthetized subjects. In both cases, the cutaneous contribution to control of vasoconstriction and shivering was linear and near 20%. These data indicate that a proportionality constant of approximately 20% can be used to compensate for experimentally induced skin-temperature manipulations in anesthetized as well as unanesthetized subjects.  (+info)

Nasal sensory receptors responding to capsaicin, water and tactile stimuli in sevoflurane-anesthetized dogs. (7/916)

Responses of nasal receptors to capsaicin and water were studied from afferent recordings of the posterior nasal nerve (PNN) in 12 anesthetized dogs. Out of 12 non-respiration-modulated nasal receptors, 7 responded only to capsaicin, 3 responded to both water and capsaicin, and 2 to neither of them. All the fibers showed a rapid adaptation to mechanical probing of the nasal mucosa. These results indicate that the presence of sensory receptors responding to capsaicin and water are involved in PNN afferents of the dog.  (+info)

I.v. clonidine: does it work as a hypotensive agent with inhalation anaesthesia? (8/916)

In a double-blind, randomized, placebo-controlled study, 41 patients received clonidine 3 micrograms kg-1 or placebo at induction of isoflurane and nitrous oxide in oxygen anaesthesia. Metoprolol was also given to achieve a systolic arterial pressure of 80 mm Hg. Requirements for metoprolol were significantly less in the clonidine group (P < 0.00035), with no significant difference in mean arterial pressures over time. It would appear that clonidine is an i.v. hypotensive agent worthy of consideration, but data during the recovery period are required to comment further on the safety of this technique.  (+info)