Recent advances in inhalation anesthesia.

Both desflurane and sevoflurane offer theoretical and practical advantages over other inhalation anesthetics for horses. The lower solubility of both agents provides improved control of delivery and helps to counteract the confounding influence of the voluminous patient breathing circuit commonly used for anesthetizing horses. The lower solubility should account for faster rates of recovery compared with the older agents; whether or not the quality of recovery differs remains to be objectively evaluated in a broad range of circumstances. The pharmacodynamic effects are, in large part, similar to those of isoflurane (e.g., low arrhythmogenicity) but with some differences. For example, desflurane may be overall more sparing to cardiovascular function (especially during controlled ventilation) compared with isoflurane and sevoflurane, which are roughly similar. Respiratory depression with both new agents is equal to or more depressing than isoflurane, suggesting the use of mechanical ventilation, especially in circumstances of prolonged management (i.e., hours of anesthesia). Both new anesthetics, not surprisingly, are expensive. From this point there are some agent-unique considerations. The anesthetic potency of both agents is less than that of isoflurane, which influences the cost of anesthesia, but also places an upper limit on inspired oxygen concentration (of particular concern with desflurane). Both agents require new vaporizers, but because of the high boiling point and steep vapor-pressure curve of desflurane, new technology was required. This translates into more costly equipment, adding to the cost of desflurane use. In addition, electricity is necessary for the new desflurane vaporizer to function, which limits its portability and adds additional practical considerations in its clinical use. On the other hand, desflurane strongly resists degradation both in vitro and in vivo, but in vitro degradation of sevoflurane by CO2 absorbents may produce renal injury. This may be true especially in association with low fresh-gas inflow rates (used to reduce the cost of using the new agent), and university based practices, where prolonged anesthesia is common.     

Techniques of inhalation anesthesia in ruminants and swine

This article reviews the implementation of inhalation anesthesia in large and small ruminants and swine. A brief discussion of the general considerations for inhalation anesthesia of large animals is followed by a review of the pharmacology of inhalation agents, induction procedures commonly used when anesthetizing ruminants and swine, methods of assessing depth of anesthesia and maintenance of anesthesia, and anesthetic machines and delivery systems appropriate for use in large and small ruminants and swine.     

循环式吸入麻醉装置的制作及其对大鼠麻醉效果

设计并制作1台用于大鼠的循环式吸入麻醉装置,并对大鼠的麻醉效果进行手术验证。利用CDR绘图软件设计麻醉装置样图,然后收集所需材料根据设计样图组装吸入麻醉装置。随机选取10只SD大鼠,使用本装置将其麻醉进行常规手术(开腹探查和胃切开术),术中记录麻醉各个阶段的时间,并用生理监测仪连续动态监测大鼠呼吸(RR)、心率(HR)、血氧(SpO_2)、收缩压(SBP)、平均动脉压(MAP)和体温(t),同时观察大鼠镇静、镇痛和肌松效果,以评价麻醉装置的安全性和可用性。根据设计样图完成了吸入麻醉装置的连接和组装。用该装置对大鼠麻醉诱导的时间为(2.20±0.45) min,达到外科麻醉所需时间为(2.12±0.36) min,麻醉维持和苏醒时间分别为(45.18±0.12),(2.40±0.55) min,麻醉总时间为(51.40±0.24) min。术中大鼠镇静、镇痛、肌松弛效果良好,在手术后10,20,30,45 min时HR、SpO_2、RR、T、SBP、MAP均保持平稳,各项生理指标在每个时间点都无显著性差异(P0.05)。该吸入麻醉装置对大鼠麻醉效果确实、安全可控,麻醉诱导和苏醒时间较快,可完全满足手术对麻醉的要求。     

The use of combined inhalation anesthesia in laboratory animal surgery

General anesthesia was induced successfully in 250 laboratory rats by use of a gas machine, human infant-type mask, and combinations of oxygen, nitrous oxide, helium, carbon dioxide, and ether. Ease and speed of induction and recovery and a relatively wide margin of safety were offered by use of the gas machine.     

Bilateral arytenoid cartilage paralysis after inhalation anesthesia in a horse

An 8-year-old Quarter Horse gelding was anesthetized for surgical exploration and debridement of a chronic draining wound in the intermandibular space. Anesthesia was without complication other than persistently low PaO2. Severe airway obstruction was evident immediately after extubation, requiring tracheostomy. Endoscopic diagnosis was bilateral arytenoid paralysis, which gradually resolved over the next 7 days. Compression, trauma, or tension of the recurrent laryngeal nerves are the postulated causes of idiopathic laryngeal hemiplegia in horses. The extremely extended position of the head and neck during anesthesia, perhaps compounded by low arterial oxygen content, may have resulted in a hypoxemic insult to the recurrent laryngeal nerves and caused bilateral arytenoid paralysis in this horse.     

Clinical comparison of recovery from total intravenous anesthesia with propofol and inhalation anesthesia with isoflurane in dogs

The characteristics of recovery from total intravenous anesthesia (TIVA) with propofol and inhalation anesthesia with isoflurane was clinically compared in 149 client-owned dogs that anesthetized for surgical or diagnostic procedures. In all dogs, anesthesia was induced with an intravenous injection of propofol following premedication with acepromazine or diazepam. As a result, 58 dogs anesthetized with propofol-TIVA showed slower but smoother recovery than 91 dogs anesthetized with isoflurane anesthesia. The dogs stood at 34.5 +/- 19.3 and 27.7 +/- 17.2 min after propofol-TIVA and isoflurane anesthesia, respectively. Adverse effects, including hypersalivation, neurologic excitement (paddling, muscle tremor/twitching, opisthotonos) and vomiting/retching, were observed in similar infrequent incidences during the recovery from both anesthetic protocols. Propofol-TIVA is suggested to be an alternative anesthetic protocol for canine practice.     

Infusion of guaifenesin,ketamine, and medetomidine in combination with inhalation of sevoflurane versus inhalation of sevoflurane alone for anesthesia of horses

OBJECTIVE: To evaluate effects of infusion of guaifenesin, ketamine, and medetomidine in combination with inhalation of sevoflurane versus inhalation of sevoflurane alone for anesthesia of horses. DESIGN: Randomized clinical trial. ANIMALS: 40 horses. PROCEDURE: Horses were premedicated with xylazine and anesthetized with diazepam and ketamine. Anesthesia was maintained by infusion of guaifenesin, ketamine, and medetomidine and inhalation of sevoflurane (20 horses) or by inhalation of sevoflurane (20 horses). A surgical plane of anesthesia was maintained by controlling the inhaled concentration of sevoflurane. Sodium pentothal was administered as necessary to prevent movement in response to surgical stimulation. Hypotension was treated with dobutamine; hypoxemia and hypercarbia were treated with intermittent positive-pressure ventilation. The quality of anesthetic induction, maintenance, and recovery and the quality of the transition to inhalation anesthesia were scored. RESULTS: The delivered concentration of sevoflurane (ie, the vaporizer dial setting) was significantly lower and the quality of transition to inhalation anesthesia and of anesthetic maintenance were significantly better in horses that received the guaifenesin-ketamine-medetomidine infusion than in horses that did not. Five horses, all of which received sevoflurane alone, required administration of pentothal. Recovery time and quality of recovery were not significantly different between groups, but horses that received the guaifenesin-ketamine-medetomidine infusion required fewer attempts to stand. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that in horses, the combination of a guaifenesin-ketamine-medetomidine infusion and inhalation of sevoflurane resulted in better transition and maintenance phases while improving cardiovascular function and reducing the number of attempts needed to stand after the completion of anesthesia, compared with inhalation of sevoflurane.     

异丙酚诱导下犬异氟醚吸入麻醉的临床效果观察

异氟醚(Iso)是一种含卤素的新型吸人麻醉药,由Terrell于1965年合成,1978年后开始大量应用于临床.异氟醚的物理性状和药理作用与安氟醚相同,但在药代学方面,体内蓄积较少,毒性更低.本文拟探讨以异丙酚(Prop)为诱导麻醉剂,辅助吸人笑气(N2O)对犬进行复合吸入麻醉,并观察其临床效果以及对犬肝、肾功能的影响.     

Effect of isoflurane inhalation anesthesia on postoperative pain due to castration of piglets

Since April 2006 piglets in Germany can only be castrated without anesthesia in the first 7 days of life. However, a castration is a painful experience even for an animal of this young age. Whether the castration under isoflurane-anesthesia is a reasonable alternative to castration without anesthesia was tested in the following investigation at 206 4 to 6 day old piglets.The serum-cortisol-concentration was chosen as the parameter for the pain caused by castration. A part of the animals was castrated without anesthesia (group II, n = 42) or with anesthesia (group IV, n = 41). Additionally Meloxicam, a non-steroidal anti-inflammatory drug, was applicated to piglets castrated with anesthesia (group V, n = 41). For control another part of the animals were only handled without (group I, n = 41) or with anesthesia (group III, n = 41), but they were not castrated. Cortisol-concentration prior to castration was compared to the concentration 0.5, 1,4 and 24 hours after castration. In addition cortisol was compared between groups at all points of time. Cortisol did rise significantly in castrated animals with animals with or without anesthesia than in animals of the non-castrated control groups. Cortisol after castration was significantly lower in piglets with an application of Meloxicam prior to castration. The pain caused by castration is an explanation for the differences in cortisol-concentration between castrated and not-castrated animals. Regarding those results, we assume that castration with isoflurane-anesthesia does not fulfil the demand for reducing pain after castration compared to castrating piglets without anesthesia.     

Evaluation of Elevent, a ventilator manufactured in Czechoslovakia for controlled ventilation during inhalation anesthesia in dogs]

Controlled breathing during halothane inhalation anesthesia was tested experimentally in fifty clinically healthy test dogs. In the first group the breathing regime was evaluated when a new Czechoslovak electronic ventilator Elvent was used in the course of 120-minute anaesthesia in 10 dogs. In the second group controlled ventilation was used in 40 dogs in the course of 180-minute anaesthesia with an administration of pipecurium as muscle relaxant. In the course of these experiments a total of 28 parameters was investigated to evaluate the effects of the given breathing regimes on the dog organism. An evaluation of the dynamics of changes in the target parameters indicated that the following model of ventilation programme with these parameters was the best: breathing rate 15-20 breaths per min., per-minute breathing capacity 1.5-3.5 l per min., breathing capacity from 0.15 to 0.25 l, inspiration length 0.8 to 1.2 s and twofold expiration length.     

Anesthetic and cardiovascular effects of balanced anesthesia using constant rate infusion of midazolam-ketamine-medetomidine with inhalation of oxygen-sevoflurane (MKM-OS anesthesia) in horses

The anesthetic sparring and cardiovascular effects produced by midazolam 0.8 mg/ml-ketamine 40 mg/ml-medetomidine 0.05 mg/ml (0.025 ml/kg/hr) drug infusion during sevoflurane in oxygen (MKM-OS) anesthesia was determined in healthy horses. The anesthetic sparring effects of MKM-OS were assessed in 6 healthy thoroughbred horses in which the right carotid artery was surgically relocated to a subcutaneous position. All horses were intubated and ventilated with oxygen using intermittent positive pressure ventilation (IPPV). The end-tidal concentration of sevoflurane (ET(SEV)) required to maintain surgical anesthesia was approximately 1.7%. Heart rate and mean arterial blood pressure averaged 23-41 beats/min and 70-112 mmHg, respectively. All horses stood between 23-44 min after the cessation of all anesthetic drugs. The cardiovascular effects of MKM-OS anesthesia were evaluated in 5 healthy thoroughbred horses ventilated using IPPV. Anesthesia was maintained for 4 hr at an ET(SEV) of 1.7%. Each horse was studied during left lateral (LR) and dorsal recumbency (DR) with a minimum interval between evaluations of 1 month. Cardiac output and cardiac index were maintained between 70-80% of baseline values during LR and 65-70% of baseline values during DR. Stroke volume was maintained between 75-85% of baseline values during LR and 60-70% of baseline values during DR. Systemic vascular resistance was not different from baseline values regardless of position. MKM-OS anesthesia may be useful for prolonged equine surgery because of its minimal cardiovascular depression in both of lateral and dorsal recumbency.