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Effects of halothane reexposure in female mice and their offspring.

Female CBi mice subjected to multiple exposures to halothane inhalation anesthesia before mating were investigated for the potential effects of such intervention on a specific antibody response mounted by them and their offspring. An assessment of the toxicologic and reproductive performance of female mice undergoing anesthesia was also performed. Adult female mice received three episodes of halothane anesthesia at weekly intervals. Seventy-two hours after the last dose, mice were subjected to the following procedures: 1) study of the specific humoral immune response to sheep red blood cells (SRBC); 2) hematologic, hepatologic, and histopathologic studies; and 3) mating with syngeneic sires. Halothane-treated females had increased amounts of specific antibody secreting B cells, with liver studies showing evidence of microscopic fatty changes and decreased lipid peroxidation. Anesthesia did not alter reproductive performance but lowered offspring survival. Offspring displayed depressed antibody response after challenge with SRBC at weaning and at 60 d of age. The anti-SRBC antibody response that was found to be enhanced in halothane anesthetized females, seemed to be conversely impaired when studied in the offspring.

Anesthetics, Inhalation↗

Anesthesia of the sighthound.

The sighthounds are an ancient group of dog breeds that have been selectively bred for high-speed pursuit of prey by sight. Probably as a consequence of this selection process, these dogs have a number of idiosyncrasies that can potentially adversely affect their anesthetic management. These include (1) nervous demeanor which can lead to stress-induced clinical complications, such as hyperthermia; (2) lean body conformation with high surface-area-to-volume ratio, which predisposes these dogs to hypothermia during anesthesia; (3) hematological differences such as a higher packed cell volume and lower serum protein compared with other dog breeds which may complicate interpretation of preanesthetic blood work; (4) Impaired biotransformation of drugs by the liver resulting in prolonged recovery from certain intravenous anesthetics, especially thiopental; and increased risks of drug interactions. Safe anesthetic management of sighthounds should include sedative premedication and appropriate use of analgesic drugs to minimize perioperative stress. Thiopental, or any other thiobarbiturate, should not be used in these dogs. Propofol, ketamine/diazepam combination, and methohexital are recommended alternative intravenous anesthetics. Avoid coadministration of agents that inhibit drug biotransformation, such as chloramphenicol. Inhalation anesthesia using isoflurane is the preferred anesthetic maintenance technique. Core body temperature should be monitored closely and techniques to minimize hypothermia should be employed both during anesthesia and into the recovery period.

Anesthesia↗

Occupational exposure to nitrous oxide and desflurane during ear-nose-throat-surgery.

PURPOSE: To determine occupational exposure of the anesthesiologist and surgeon to nitrous oxide and desflurane during general anesthesia for ear-nose-throat (ENT) surgery in children and adults. METHODS: An observational clinical trial was performed in ten children (C) and ten adults (A). Tracheas were intubated, in adults, with cuffed tubes and in children with uncuffed tubes. The operating room was equipped with modern air conditioning and waste anesthetic gas scavengers. Gas samples were obtained during the operative procedure every 90 sec from the breathing zone of subjects. Time-weighted averages (TWA) over the time of exposure were calculated for nitrous oxide and desflurane. RESULTS: Nitrous oxide TWAs for anesthesiologists were 0.41 +/- 0.23 ppm (A) and 1.20 +/- 0.32 ppm (C, P < 0.0001), and 2.24 +/- 1.93 ppm (A) and 5.30 +/- 0.60 ppm (C, P = 0.0001) for the surgeon who worked close to the patient's airway and thus had higher exposure (P < 0.05 [A], P < 0.0001 [C]). With regard to desflurane, the anesthesiologists' TWAs were 0.02 +/- 0.03 ppm for both adults and children. The surgeon was exposed to 0.21 +/- 0.24 ppm desflurane (A) and 0.30 +/- 0.14 ppm (C, P: n.s.). Although the surgeon's exposure was greater (P < 0.05 [A], P < 0.0001 [C]), the threshold limits of 25 ppm for nitrous oxide and 2 ppm for desflurane recommended by the National Institute of Occupational Safety and Health were not exceeded. CONCLUSIONS: Under modern air conditioning, occupational exposure to inhalational anesthetics is low, and inhalational anesthesia is safe from the standpoint of modern workplace laws and health-care regulations.

Adult↗

Anesthesia and pain management for pediatric patients with dystrophic epidermolysis bullosa.

STUDY OBJECTIVE: To review anesthesia and pain management in pediatric patients with recessive dystrophic epidermolysis bullosa (RDEB). STUDY DESIGN: Retrospective study. SETTING: University-affiliated pediatric hospital. PATIENTS: 25 pediatric patients with RDEB had a total of 121 surgical procedures. MEASUREMENTS AND MAIN RESULTS: Pediatric patients with RDEB could have vesicles and bullae formation in the skin in response to trauma, friction, or pressure. The common surgical procedures for patients with RDEB were balloon dilation of esophageal strictures (38%), pseudosyndactyly release with or without skin graft (27%), postsurgical or skin care related dressing changes (21%), percutaneous endoscopic gastrostomy tube placement (8%), and circumcision (2%). Our anesthetic techniques included general inhalational anesthesia using mask (21%), general anesthesia using endotracheal tube (48%), and intravenous sedation (31%). No death or other major perioperative anesthetic complications occurred in these reported cases. CONCLUSIONS: Patients with RDEB can present considerable management issues for the anesthesiologists. Anesthesia and pain management can be carefully delivered with proper preoperative evaluation and preparation for pediatric patients with RDEB.

Adolescent↗

Inguinal herniorrhaphy in young infants: perianesthetic complications and associated preanesthetic risk factors.

STUDY OBJECTIVES: (1) To prospectively observe and tabulate all perianesthetic complications in young infants undergoing herniorrhaphy with general anesthesia and (2) to identify all major postnatal complications and determine which, if any, might be significant risk factors for perianesthetic complications. DESIGN: Prospective case control study. SETTING: Columbus, Ohio, Children's Hospital, a teaching and tertiary referral center. PATIENTS: One hundred two consecutive infants 60 weeks postconceptual age (PCA) or younger undergoing herniorrhaphy with general anesthesia. INTERVENTIONS: None MEASUREMENTS AND MAIN RESULTS: All perianesthetic complications occurring during anesthesia, in the postanesthesia care unit (PACU), during the remaining hospital stay, and within 30 days of anesthesia were recorded, and a detailed postnatal history was compiled. Fifty-five percent of 60 preterm infants [37 weeks gestational age (GA) or younger] and 50% of 42 term infants (older than 37 weeks GA) experienced at least one perianesthetic complication. Following discharge from the PACU, in-house complications were confined to the preterm group. Significant risk factors included a history of apnea, bradycardia, and ventilatory support for at least 24 hours after birth, mainly for respiratory distress syndrome. CONCLUSIONS: In a teaching hospital, prospectively observed perianesthetic complications can occur in more than 50% of infants 60 weeks PCA or younger undergoing herniorrhaphy with inhalation anesthesia. Infants younger than 49 weeks PCA with a significant preanesthetic risk factor should be monitored overnight for apnea and bradycardia.

Anesthesia, General↗

Surgical management of preputial injuries in bulls: 51 cases (1986-1994).

The purpose of this study was to compare success rates for preputial surgery depending on the initial diagnosis, ability to extend the penis, use of sedation and local anesthesia versus general anesthesia for surgery, and surgical technique. Medical records of 51 bulls treated surgically for preputial injury were reviewed. The mean age of the bulls was 2.5 years ranging from 1 to 5 years. Bos taurus breeds (82.3%) were more often affected than Bos indicus breeds (17.7%). The most common breeds represented in this study were Angus (45.1%), Simmental (11.8%), and brangus (9.8%). The seasonal incidence of preputial injuries was higher during the period of May-July (52.9%) and November-February (33.3%). The overall success rate was 70%. Posthioplasty was more successful than circumcision (90% to 43%) (P < 0.05). The success rate for surgeries performed under inhalation anesthesia in the surgery suite was 100% compared with a success rate of 63% for those animals operated on with injectable and local anesthesia in a rotary chute (P < 0.05). The success rate was 88% if the penis could be extended before the surgery and 36% if extension was not achieved (P < 0.05).

Animals↗

Flap flow and cardiac output as functions of pulmonary artery wedge pressure: experimental study in the pig.

Cardiac output (CO) is redistributed during hypovolemia, but it has not been clearly documented how this influences flap perfusion. Simultaneous changes in perfusion of a muscle flap and CO as modulated by reductions in cardiac filling pressure were compared in a pig model. The hypothesis was that flap flow (FF) would remain relatively constant as CO was reduced, according to the Frank-Starling curve. Under general anesthesia, five domestic pigs were utilized. Following right carotid artery cannulation, measurement of systemic blood pressure and blood gas analysis were carried out. An oximetric Swan-Ganz catheter insertion via the right internal jugular vein was used to measure CO, temperature, and pulmonary artery wedge pressure (PAWP). In the lateral decubitus position, a right latissimus dorsi muscle flap was elevated in the animal, using standard technique. The insertion of the muscle was divided, and a 1-cm section of thoracodorsal artery was mobilized to measure flap perfusion with a transonic Doppler flowmeter. After baseline measurements of PAWP, CO, and FF were obtained, blood volume was reduced in 350-cc aliquots at 10-min intervals. After each aliquot was removed, the hemodynamic parameters were again recorded. This procedure was repeated until the CO was less than 1.0 liter/min; at this point the pig was sacrificed. The mean baseline PAWP was 15.6+/-4.0 mmHg, which was reduced to 2.2+/-1.1 mmHg (p<0.05) by the end of the experiment. The mean baseline FF was 5.6+/-1.9 cc/sec, and the mean baseline CO was 4.6+/-1.0 l/min; these were reduced to 0.4+/-0.4 cc/sec (p< 0.05) and 1.1+/-0.1 l/min (p<0.05), respectively, by the end of the experiment. FF and CO were plotted as a function of PAWP and the two regression curves were evaluated by analysis of covariance. The slope of these curves was not different, p=0.4. The hypothesis that FF would be preserved in the face of reductions in CO did not prove to be correct in this experiment. Changes in FF paralleled changes in CO as the PAWP was reduced. Inhalation anesthesia and local sympathectomy may influence flap perfusion during hypovolemia. These results underscore the importance of avoiding hypovolemia during flap surgery, in order to maintain flap perfusion.

Anesthetics, Inhalation↗

Rapid sequence induction: a national survey of practice.

We performed a national postal survey exploring anaesthetists' practice in rapid sequence induction. All respondents used pre-oxygenation, although the technique employed, and its reliability, varied. Thiopental and succinylcholine, given after waiting for signs of loss of consciousness, were the most widely used drugs for rapid sequence induction. Propofol and rocuronium were used by more than a third of respondents, and most respondents (75%) also routinely administered an opioid. Cricoid pressure was used universally but the practice of its application varied widely. The commonest aids used if intubation was difficult were the gum elastic bougie, the long laryngoscope blade and the laryngeal mask. After failed intubation, approximately half of respondents would maintain the supine position. Failure to intubate at rapid sequence intubation had been seen by 45% of respondents but harm was uncommon. In contrast, 28% had seen regurgitation, which frequently led to considerable harm and to three deaths. In spite of this, practice of a failed intubation drill was uncommon (15%) and anaesthetic assistants were rarely known to practice application of cricoid pressure. Consultants were less likely than trainees to use rocuronium as a muscle relaxant, and more likely to choose morphine if administering an opioid. They were less likely to practice a failed intubation drill. Other aspects of practice varied little between grades. This survey suggests that many anaesthetists do not follow best practice when performing a rapid sequence induction.

Anesthesia, General↗

Bilateral cervical plexus block for thyroidectomy and parathyroidectomy in healthy and high risk patients.

We evaluated the benefits of bilateral deep cervical plexus block regional anesthesia in healthy and high risk patients undergoing thyroid and parathyroid surgery and assessed its effects on respiratory function. Twenty-one patients undergoing thyroid and parathyroid operations were studied. Bilateral superficial and deep plexus blocks were performed in all patients except one (who received only superficial plexus block because of a slightly prolonged prothrombin time) with 0.375-0.5% bupivacaine with 1:200,000 epinephrine. Intraoperatively, supplemental intravenous sedatives/narcotics were titrated to achieve patient comfort and cooperation. To allay anxiety, patients were allowed to listen to music via headphones intraoperatively. Forced vital capacity was measured before block, 10 minutes after the block and in the recovery room in half the patients. Eighteen patients tolerated the procedure well with supplemental sedation. Two patients required supplemental inhalation anesthesia via mask and one required tracheal intubation because of coughing prior to surgery. Three high risk patients tolerated the procedure well requiring only intraarterial line monitoring. Postoperatively, 11 patients had minimal incisional pain, 13 patients had mild pain on swallowing and 2 patients complained of nausea. There were no significant differences in the baseline forced vital capacity vs. forced vital capacity measured after the block and in the recovery room. This study indicates that regional anesthesia is an appropriate alternative to general anesthesia in selected patients undergoing thyroid and parathyroid surgery and did not compromise respiratory function.

Adult↗

Use of N2O/O2/enflurane anesthesia for dental treatment of the handicapped.

To develop an anesthesia maintenance method that could be expected to maintain a reasonably stable state during dental treatment of the handicapped, three methods (N2O/O2 [0% enflurane (E), n = 12], N2O/O2/0.6% E [n = 8], N2O/O2/1.5% E [n = 7]) were evaluated in terms of changes in plasma levels of cortisol, epinephrine (EP), and norepinephrine (NE). During a treatment period of 60 minutes, cortisol levels increased in the 0% E group (from 9.5 +/- 1.8 micrograms/dL to 19.4 +/- 2.4 micrograms/dL, P less than .01), did not change in 0.6% E group, and decreased in 1.5% E group (from 9.3 +/- 1.7 micrograms/dL to 5.8 +/- 1.0 micrograms/dL, P less than .01). Epinephrine and NE levels increased in the 0% E group, but were suppressed in the 0.6% E and 1.5% E groups. It is suggested that N2O/O2 inhalation anesthesia supplemented with low-dose enflurane produces a stable state during dental treatment with respect to cortisol, EP, and NE responses.

Adolescent↗

Effect of anesthetic agent on lung tumor induction in hamsters given benzo[a]pyrene-ferric oxide.

The effects of an anesthetic agent on lung tumor induction in noninbred Syrian golden hamsters were investigated after intratracheal instillation of a benzo[a]pyrene-ferric oxide mixture. Inhalation anesthesia with ether or methoxyflurane was accomplished with a closed recirculatory system that allowed a short induction time for anesthesia and a good control over the concentration of anesthetic. This type of anesthetic induction was compared with systemic induction by Brevital. Survival rates during the 10 weekly instillations were least for the Brevital-treated group and greatest for the methoxyflurane-treated group. Body weight gain was lower in both the ether- and Brevital-treated groups as compared to the group anesthetized with methoxyflurane. The animals anesthetized with Brevital had the shortest tumor latency, but the tumor incidence during the weeks of the experiment was similar in the group treated with this agent and the group treated with ether. Exposure to methoxyflurane and the carcinogen produced a slow onset of deaths from tumors and lower tumor incidence. These results are discussed in relation to retention of the dose of carcinogen in the respiratory tract and effect of inhalation anesthia on consequent lung tissue pathology.

Anesthetics↗

Middle ear pressure variation: effect of nitrous oxide.

Previous studies examining middle ear pressure changes due to inhalant anesthesia, including nitrous oxide, have cited equivocal results. An investigation was performed to closely monitor changes in middle ear pressure during middle ear surgery. Baseline tympanometry was performed before anesthesia, and middle ear pressure was then documented in 1-min time intervals. A total of 97 subjects were studied; 51 received nitrous oxide and halothane, and 46 received halothane alone. Results indicate that nitrous oxide causes significantly greater pressure fluctuations than halothane alone. There were no effects for time of surgery, type of fluid, or baseline. Pressure fluctuation was attributed to eustachian tube function. Case studies are presented to demonstrate subject variability, and suggestions for validation study procedures are presented.

Acoustic Impedance Tests↗

Maternal inspired oxygen concentration and fetal oxygenation during caesarean section.

This study was designed to determine whether fetal arterial and venous PO2 could be increased by increasing maternal FIO2 in the period between hysterotomy and birth. Two groups of ten patients were studied. All were anaesthetised with the same technique except for the FIO2 after hysterotomy. One group inspired 50% oxygen and the second group inspired 100% oxygen. Although the maternal arterial PO2 was higher at birth in the 100% O2 group (177.4 +/- 42.3 mmHg vs 281.0 +/- 94.2 mmHg), there were no differences between the arterial umbilical cord PO2 (19.3 +/- 5.7 mmHg vs 18.5 +/- 7.3 mmHg) and the venous umbilical cord PO2 (31.1 +/- 7.6 mmHg vs 33.0 +/- 10.8 mmHg). Awareness was present in one patient in the 50% O2 group and in four patients in the 100% O2 group but this difference was not statistically significant. It is concluded that a higher inspired maternal oxygen concentration between hysterotomy and birth does not result in any increase in fetal PO2.

Anesthesia, Inhalation↗