COMPARISON OF ISOFLURANE GAS VERSUS A GUAIFENESIN, KETAMINE, AND MEDETOMIDINE CONSTANT-RATE INFUSION FOR MAINTENANCE ANESTHESIA IN AMERICAN BLACK BEARS (URSUS AMERICANUS).

Published anesthetic protocols for captive and free-ranging bears are limited to injectable inductions with maintenance via inhalants or additional injectable boluses. Though common in other species, intravenous (IV) continuous-rate infusions (CRI) using guaifenesin combinations have not been evaluated in ursids. This study evaluated the use of a CRI compared to an inhalant for maintenance anesthesia. Seven healthy American black bears (Ursus americanus) were anesthetized in a crossover design with two different anesthetic maintenance protocols. Bears were immobilized with ketamine (2.02 ± 0.14 mg/kg) and medetomidine (0.04 ± 0.003 mg/kg) for both protocols. The anesthetic maintenance control protocol consisted of isoflurane gas (ISO) started at 2% delivered by endotracheal tube; the experimental protocol consisted of guaifenesin, medetomidine, ketamine (GMK) IV CRI started at 50 mg/kg/hr guaifenesin, 0.01 mg/kg/hr medetomidine, and 1 mg/kg/hr ketamine. Induction and recovery parameters including time to first effect, recumbency, and hands on; duration of maintenance protocol; and time from reversals administered to head up, standing on all four feet, no ataxia, and to fully recovered were recorded and compared between protocols. Heart rate, respiratory rate, rectal temperature, blood pressure, end tidal carbon dioxide, and hemoglobin oxygen saturation were recorded at 5-min intervals and compared between protocols. Venous blood gases were obtained at the start, middle, and end of the maintenance anesthesia and compared between protocols. All bears exhibited hypertension with mild respiratory acidosis throughout procedures. Measured physiologic parameters did not differ significantly between the isoflurane and the GMK CRI maintenance protocols, with the exception of higher endpoint (ISO) pCO2 measurements. No adverse events were recorded with either protocol, and adequate depth of anesthesia was maintained with both protocols. GMK CRI provides a safe, effective, and more portable alternative to inhalant anesthetics for maintenance anesthesia in bears in captivity or in the field.

Guaiphenesin-ketamine-xylazine infusion to maintain anesthesia in mules undergoing field castration.

BACKGROUND: In order to determine whether a combination of guaiphenesin, ketamine and xylazine can induce safe and satisfactory anaesthesia in mules undergoing field castration, eight healthy adult intact male mules were employed. They were premedicated with intravenous (IV) xylazine (1.3 mg/kg); an additional dose of xylazine (0.3 mg/kg IV) was administered in case of inadequate depth of sedation. Anaesthesia was induced with IV thiopental (6 mg/kg). The quality of sedation and induction was recorded. Anaesthesia was maintained with an infusion of guaiphenesin (50 mg/mL), ketamine (2 mg/mL) and xylazine (1 mg/mL) (GKX). The spermatic cord of each testis was infiltrated with 5 mL of 2% lidocaine. During anaesthesia heart rate (HR), respiratory rate (RR), rectal temperature (RT) and haemoglobin oxygen saturation (SpO2) were measured every 5 min. The data were analysed with simple one-way analysis of variance (ANOVA). A P value < 0.05 was considered statistically significant. Time of anesthesia, time of surgery and time of recovery were recorded. RESULTS: Only one mule required an additional dose of xylazine to achieve a satisfactory depth of sedation. Thiopental at the dose of 6 mg/kg IV resulted in smooth induction and lateral recumbency in all animals. GKX provided adequate anaesthesia to perform castration in all mules. Muscle relaxation was deemed adequate and physiological variables remained stable and within references values during the anaesthesia and did not change in response to surgical stimulation. Time (mean ± standard deviation) from the end of the infusion to sternal recumbency and time from sternal recumbency to standing were 27.7 ± 4.6 and 30.1 ± 7.7 min, respectively. CONCLUSIONS: The combination of xylazine, thiopental and GKX provides satisfactory short-term anaesthesia in mules undergoing field castration.

Evaluation of intranasal oxygen supplementation in mules anesthetized with the combination of ketamine, butorphanol, and guaifenesin / Avaliação da suplementação intranasal de oxigênio em muares anestesiados com a associação de cetamina, butorfanol e éter gliceril guaiacólico

Hypoxemia is a major complication of field anesthesia and no studies regarding this occurrence in mules has been done. Thus, the aim of this study was to evaluate intranasal oxygen supplementation (IOS) in mules (Equus caballus x Equus asinus) anesthetized with ketamine/butorphanol/guaifenesin combination. For this, we used six male, adult mules (322±29kg) which underwent premedication (MPA) with 0.2mg/kg of midazolam intramuscularly after 15 minutes, 0.02mg/kg detomidine IV 5 minutes after, induction IV with combination of ketamine (2mg/mL), butorphanol (22.5mg/mL), and guaifenesin (50mg/mL) (K/B/G) until lateral decumbency. Maintenance was done with the same anesthetic combination. The animals were submitted twice to the protocol described above, 20 days apart, forming two groups. CG: MPA, induction (0.92±0.24mL/kg (mean±SD)), and maintenance (2.2±0.2mL/kg/h) without SIO; TG: MPA, induction (0.98±0.17mL/kg), and maintenance (2.3±0.4mL/kg/h) with IOS flow 40mL/kg/h. During anesthesia arterial blood was collected every 20 minutes (T0, T20, T40, and T60) for blood gas analysis. Data analyzed by ANOVA followed by the Bonferroni test. P<0.05 was considered significant. Hypoxemia of the animals in the CG in periods (59±5; 55±5; 53±7; 49±8) with lower averages than the TG (160±4, 115±34, 92±25, 81±19) was observed, demonstrating that IOS increases PaO2 avoiding the occurrence of hypoxemia.(AU)

A hipoxemia é uma das principais complicações da anestesia a campo, e em muares não existem estudos a respeito dessa ocorrência. Assim, objetivou-se avaliar a suplementação intranasal de oxigênio (SIO) em muares (Equus caballus x Equus asinus) anestesiados com cetamina/butorfanol/guaifenesina associados. Para isso, foram utilizados seis muares, macho e adultos (322±29kg), submetidos à medicação pré-anestésica (MPA) com 0,2mg/kg de midazolam por via intramuscular, após 15 minutos, 0,02mg/kg de detomidina por via intravenosa, após cinco minutos, indução com administração intravenosa da associação de cetamina (2mg/mL), butorfanol (22,5 µg/mL) e guaifenesina (50mg/mL) em solução de glicose a 5% (C/B/G) até o animal assumir o decúbito lateral. A manutenção foi realizada com a mesma associação anestésica. Os animais foram submetidos duas vezes ao protocolo descrito anteriormente, com intervalo de 20 dias, formando dois grupos experimentais. GC -MPA, indução (0,92±0,24mL/kg (média±DP)) e manutenção (2,2±0,2mL/kg/h) sem SIO; GT - MPA, indução (0,98±0,17mL/kg) e manutenção (2,3±0,4mL/kg/h) com SIO, fluxo de 40mL/kg/h. Durante a anestesia, foi colhido sangue arterial a cada 20 minutos (T0, T20, T40 e T60) para hemogasometria. Os dados foram analisados pela ANOVA, seguidos pelo teste de Bonferroni. Valores de P<0,05 foram considerados significativos. Foi observada hipoxemia (PaO2<60mmHg) dos animais no GC nos tempos avaliados (T0= 59±5; T20= 55±5; T40= 53±7; T60= 49±8), com médias menores que as do GT, (160±4; 115±34; 92±25; 81±19, respectivamente), o que demonstrou que a suplementação intranasal de oxigênio aumenta a PaO2, evitando a ocorrência de hipoxemia.

Effects of adding butorphanol to a balanced anaesthesia protocol during arthroscopic surgery in horses.

Three groups of horses scheduled for arthroscopic surgery were premedicated with 0.025 mg/kg acepromazine, 88 microg/kg romifidine and 25 mg/kg guaifenesin, and anaesthesia was induced with 2.2 mg/kg ketamine. In group 1 (14 horses), anaesthesia was maintained by halothane vaporised in oxygen, with supplementary doses of 20 microg/kg romifidine and 0.5 mg/kg ketamine every 20 minutes. The 17 horses in group 2 were maintained as for group 1; however, an additional dose of 0.05 mg/kg butorphanol was administered before the first incision. The 14 horses in group 3 were maintained as for group 2, except that the dose of romifidine was halved to 10 microg/kg. The mean (sd) dose of vaporised halothane (6.5 [1.1], 4.8 [1.3] and 4.8 [1.3] microl/kg/minute, for groups 1, 2 and 3, respectively), vaporiser dial setting (2.3 [0.2],1.6 [0.4] and 1.3 [0.1] per cent) and dose of dobutamine administered to correct episodes of hypotension (0.16 [0.08], 0.07 [0.09] and 0.0 [0.0] microg/kg/minute) were all significantly lower in groups 2 and 3 than in group 1. Mean arterial blood pressure was significantly higher in groups 2 and 3 than in group 1 (71 [3], 74 [5] and 80 [5] mmHg, for groups 1, 2 and 3, respectively).

Effect of mode of administration on guaifenesin pharmacokinetics and expectorant action in the rat model.

AIM: Guaifenesin is a very commonly used and prescribed oral expectorant drug. However, its mechanism of action is not completely elucidated and the available information is limited. The purpose was to evaluate whether guaifenesin action on respiratory tract secretion is mediated through a reflex stimulation of the gastric mucosa or by the systemic exposure due to the absorption of the drug to the blood circulation. METHODS: Guaifenesin was administered to rats by various routes: intravenous bolus, oral gavage, and gastric, jejunal or cecal infusions (through surgically implanted catheters). Phenol red respiratory tract secretion (after intraperitoneal or intravenous injection) was used as a marker for degree of expectorant action. Administration of saline by gavage was used as control. RESULTS: Respiratory secretion following oral bolus was approximately 2-fold higher (p<0.05) than that of control. Following IV administration the increase of respiratory secretion did not occur despite the fact that systemic exposure to guaifenesin was 1.5-fold higher than following oral administration. The abdominal surgery was found to eliminate the effect of guaifenesin although it did not change systemic absorption. Guaifenesin was equally absorbed from all parts of the gastrointestinal tract. CONCLUSIONS: It was demonstrated that expectorant action of guaifenesin is mediated by stimulation of the gastrointestinal tract and not by the systemic exposure to the drug.

Cardiopulmonary effects of administration of a combination solution of xylazine, guaifenesin, and ketamine or inhaled isoflurane in mechanically ventilated calves.

OBJECTIVE: To compare the cardiopulmonary effects of administration of a solution of xylazine, guaifenesin, and ketamine (XGK) or inhaled isoflurane in mechanically ventilated calves undergoing surgery. ANIMALS: 13 male calves 2 to 26 days of age. Procedures-In calves in the XGK group, anesthesia was induced (0.5 mL/kg) and maintained (2.5 mL/kg/h) with a combination solution of xylazine (0.1 mg/mL), guaifenesin (50 mg/mL), and ketamine (1.0 mg/mL). For calves in the isoflurane group, anesthesia was induced and maintained with isoflurane in oxygen. The rates of XGK infusion and isoflurane administration were adjusted to achieve suitable anesthetic depth. All calves received 100% oxygen and were mechanically ventilated to maintain end-tidal carbon dioxide concentrations from 35 to 40 mm Hg and underwent laparoscopic bladder surgery through an abdominal approach. Cardiopulmonary variables were measured before induction and at intervals up to 90 minutes after anesthetic induction. RESULTS: The quality of induction was excellent in all calves. The XGK requirements were 0.57 +/- 0.18 mL/kg and 2.70 +/- 0.40 mL/kg/h to induce and maintain anesthesia, respectively. Heart rate was significantly lower than baseline throughout the anesthetic period in the XGK group. Systolic arterial blood pressure was significantly higher in the XGK group, compared with the isoflurane group, from 5 to 90 minutes. Cardiac index was lower than baseline in both groups. Differences between groups in cardiac index and arterial blood gas values were not significant. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of XGK resulted in excellent anesthetic induction and maintenance with cardiopulmonary alterations similar to those associated with isoflurane in mechanically ventilated calves.

Bilateral guaifenesin ureteral calculi.

We report on a patient with bilateral ureteral calculi composed of guaifenesin metabolite as determined by infrared spectroscopy. These stones may be associated with excessive guaifenesin intake related to the current popularity of ephedrine preparations.

Comparison of thiopentone/guaifenesin, ketamine/guaifenesin and ketamine/midazolam for the induction of horses to be anaesthetised with isoflurane.

Forty-eight horses subjected to elective surgery were randomly assigned to three groups of 16 horses. After premedication with 0.1 mg/kg acepromazine intramuscularly and 0.6 mg/kg xylazine intravenously, anaesthesia was induced either with 2 g thiopentone in 500 ml of a 10 per cent guaifenesin solution, given intravenously at a dose of 1 ml/kg (group TG), or with 100 mg/kg guaifenesin and 2.2 mg/kg ketamine given intravenously (group KG), or with 0.06 mg/kg midazolam, and 2.2 mg/kg ketamine given intravenously (group KM). Anaesthesia was maintained with isoflurane. The mean (sd) end tidal isoflurane concentration (per cent) needed to maintain a light surgical anaesthesia (stage III, plane 2) was significantly lower in group KM (0.91 [0.03]) than in groups TG (1.11 [0.03]) and KG (1.14 [0.03]). The mean (sd) arterial pressure (mmHg) was significantly lower in group KG (67.4 [2.07]) than in groups TC (75.6 [2.23]) and KM (81.0 [2.16]). There were no significant differences in the logarithm of the heart rate, recovery time or quality of recovery between the three induction groups. However, pronounced ataxia was observed in the horses of group KM, especially after periods of anaesthesia lasting less than 75 minutes.

Comparison of four drug combinations for total intravenous anesthesia of horses undergoing surgical removal of an abdominal testis.

OBJECTIVE: To evaluate anesthetic effects of 4 drug combinations used for total intravenous anesthesia of horses undergoing surgical removal of an abdominal testis. DESIGN: Clinical trial. ANIMALS: 32 healthy cryptorchid horses. PROCEDURE: Horses were sedated with xylazine and butorphanol and were randomly assigned to 1 of 4 groups: induction of anesthesia with ketamine and diazepam and maintenance with bolus administration of ketamine and xylazine (KD/KX); induction and maintenance of anesthesia with bolus administration of tiletamine-zolazepam, ketamine, and detomidine (TKD); induction and maintenance of anesthesia with continuous infusion of xylazine, guaifenesin, and ketamine; and induction and maintenance of anesthesia with continuous infusion of guaifenesin and thiopental. Horses that moved 3 consecutive times in response to surgical stimulation or for which surgery time was > 60 minutes were administered an inhalant anesthetic, and data from these horses were excluded from analysis. RESULTS: Quality of induction was not significantly different among groups. Muscle relaxation and analgesia scores were lowest for horses given KD/KX, but significant differences among groups were not detected. Horses anesthetized with TKD had a significantly greater number of attempts to stand, compared with the other groups, and mean quality of recovery from anesthesia for horses in the TKD group was significantly worse than for the other groups. Anesthesia, surgery, and recovery times were not significantly different among groups. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that all 4 drug combinations can be used to induce short-term anesthesia for abdominal cryptorchidectomy in horses. However, horses receiving TKD had a poorer recovery from anesthesia, often requiring assistance to stand.

Combination of continuous intravenous infusion using a mixture of guaifenesin-ketamine-medetomidine and sevoflurane anesthesia in horses.

The anesthetic and cardiovascular effects of a combination of continuous intravenous infusion using a mixture of 100 g/L guaifenesin-4 g/L ketamine-5 mg/L medetomidine (0.25 ml/kg/hr) and oxygen-sevoflurane (OS) anesthesia (GKM-OS anesthesia) in horses were evaluated. The right carotid artery of each of 12 horses was raised surgically into a subcutaneous position under GKM-OS anesthesia (n=6) or OS anesthesia (n=6). The end-tidal concentration of sevoflurane (EtSEV) required to maintain surgical anesthesia was around 1.5% in GKM-OS and 3.0% in OS anesthesia. Mean arterial blood pressure (MABP) was maintained at around 80 mmHg under GKM-OS anesthesia, while infusion of dobutamine (0.39+/-0.10 microg/kg/min) was necessary to maintain MABP at 60 mmHg under OS anesthesia. The horses were able to stand at 36+/-26 min after cessation of GKM-OS anesthesia and at 48+/-19 minutes after OS anesthesia. The cardiovascular effects were evaluated in 12 horses anesthetized with GKM-OS anesthesia using 1.5% of EtSEV (n=6) or OS anesthesia using 3.0% of EtSEV (n=6). During GKM-OS anesthesia, cardiac output and peripheral vascular resistance was maintained at about 70% of the baseline value before anesthesia, and MABP was maintained over 70 mmHg. During OS anesthesia, infusion of dobutamine (0.59+/-0.24 microg/kg/min) was necessary to maintain MABP at 70 mmHg. Infusion of dobutamine enabled to maintaine cardiac output at about 80% of the baseline value; however, it induced the development of severe tachycardia in a horse anesthetized with sevoflurane. GKM-OS anesthesia may be useful for prolonged equine surgery because of its minimal cardiovascular effect and good recovery.

Cardiovascular effects of surgical castration during anaesthesia maintained with halothane or infusion of detomidine, ketamine and guaifenesin in ponies.

Sixteen colts were premedicated with acepromazine and anaesthesia was induced with detomidine and ketamine. Ponies were randomly allocated to receive halothane (HAL) or infusion of detomidine, ketamine and guaiphenesin (DKG) to maintain anaesthesia. Heart and respiratory rate, ECG, mean arterial blood pressure (MABP), cardiac index (CI), blood gases and plasma cortisol, ketamine and guaiphenesin were measured. Surgical castration took place between 45 and 75 min and anaesthesia lasted 90 min. MABP with DKG was significantly higher than with HAL, and, with HAL, MABP increased from pre-surgery (64 +/- 6 mmHg) to mid-surgery (80 +/- 5 mmHg) but did not change with DKG. At 30 min, CI was similar in both groups (57 +/- 7 ml/kg bwt/min); it decreased during surgery with HAL and remained low, but it increased slightly with DKG, and was higher than with HAL at 60 and 90 min. Plasma cortisol decreased in both groups until 40 min then increased with HAL only during surgery. Ketamine concentration reached a plateau (1.3-1.8 microg/ml) between 20 and 90 min and guaiphenesin concentration between 60 and 90 min (99-101 microg/ml). Recovery was generally smooth in both groups. This study demonstrated that during HAL the increase in blood pressure associated with surgical stimulus is accompanied by decreased CI; this did not occur during DKG which is likely to lead to better tissue perfusion than HAL. The adrenocortical activity seen during HAL was absent during DKG which may result from pituitary depression, analgesic effects of total intravenous anaesthesia (TIVA) or better perfusion.

Management of sinusitis in adult cystic fibrosis.

Until recently, cystic fibrosis was frequently fatal during childhood. However, with current medical management, many patients are living into adulthood. This has created a new population of patients with chronic sinusitis and severe medical problems. In this report, experience with 22 patients, eight of whom have undergone sinus surgery, is presented, and recommendations for management are proposed. Presenting symptoms are typical of sinusitis, but in a few patients, severe debilitating headaches predominate. Oral antibiotics are often of little use due to the numerous courses of high dose intravenous antibiotics used for resistant pulmonary infections. Topical nasal steroids and mucolytics have been of some benefit. Fourteen operative procedures were performed on eight patients. These procedures included 12 endoscopic sphenoethmoidectomies, four Caldwell-Luc procedures, two frontal sinus obliterations, and one transseptal sphenoidotomy (many of these were in combination.) Results from this experience indicate 1) Failure of endoscopic surgery to control frontal and maxillary sinus disease; 2) Delayed healing of the ethmoid cavity with persistent crusting; and 3) Significant, albeit short term, symptomatic relief following surgical intervention. Based on this limited series, we conclude that surgery should be delayed until absolutely necessary and that an aggressive approach should be adopted when surgery is performed. In our hands this included initial endoscopic sphenoethmoidectomy with open surgical techniques used for removal of trapped inspissated secretions. We recommend long term intravenous antibiotics postoperatively and frequent cleaning of the ethmoid cavity after surgery, continuing indefinitely, to optimize the benefit of surgery.

Anestesia em cães utilizando éter glicerol guaiacol, quetamina e fentanil em infusão contínua intravenosa / Anaesthesia in dogs using continuous intravenous infusion of guaiphenesin, ketamine and fentanyl

Onze cães, sem raça definida, receberam como medicação pré-anestésica a anestesia induzida e mantida por infusão contínua intravenosa de quetamina e fentanil em solução de éter gliceril guaiacol a 5% em glicose a 5%, através de bomba de infusão. Em seis animais foram mensuradas frequência cardíaca e respiratória, ventilometria (volume corrente e volume minuto), pressão arterial (sistólica, média e diastólica), temperatura retal, hemogasometria arterial, saturação de 02 na hemogoblina, anion residual, osmolalidade sérica, concentração sérica total de 02, hematócrito, hemoglobina, glicose e eletrólitos. Avaliou-se também a analgesia através de pinçamento da pele da região glabra. Em outro grupo de cinco animais, onde foram realizadas três ovários-salpingo-histerectomias e duas osteossínteses, foram mensuradas a frequência cardíaca e respiratória e a resposta ao estímulo cirúrgico. Em ambos os grupos observou-se, principalmente, depressão respiratória dose-dependente, agravada com o uso de velocidade de infusão elevada, no caso de manobras cirúrgicas muito cruentas, como manipulação de periósteo.

Eleven mongrel dogs were premedicated with methotrimeprazine. Anaesthesia was induced and main-tained by continuous intravenous infusion of a 5% glucose solution containing guaiphenesin, ketamine and fentanyl. Heart and respiratory rates, tidal and minute volume, systolic, mean and diastolic blood pressure, temperature, arterial blood gases, hemoglobin oxygen saturation, anion gap, serum osmolality, serum oxygen concentration, packed cell volume, hemoglobin, glucose and electrolytes were measured in six dogs. Analgesia was investigated usind a forceps in the skin. In the other five dogs heart and respiratory rates and response to surgical stimulus were investigated. Respiratory acidosis, hypoximia and hypoventilation were observed. Respiratory depression was proportional to the infusion rate, particulary when high infusion rates were used for bone repair.

Staging of chronic hyperplastic rhinosinusitis: treatment strategies.

In 1990 we reported an initial prospective study of 100 patients using a four-stage system for classification of chronic rhinosinusitis. Between January 1988 and July 1992, we used this system in staging an additional 1814 patients, on whom 2980 intranasal sphenoethmoidectomies were performed. In this staging system a protocol trial of medication was given for 2 weeks, followed by axial and coronal computed tomography. Medication consisted of a second-generation cephalosporin antibiotic, usually cefuroxime; a 4-day burst of intraoral steroids, usually prednisone; and an antihistamine decongestant if not contraindicated. The stages of chronic hyperplastic rhinosinusitis included the stages described in the 1990 report (i.e., stage I, single-focus disease; stage II, discontiguous disease throughout the ethmoid labyrinth; stage III, diffuse disease responsive to medication; and stage IV, diffuse disease unresponsive to or poorly responsive to medication). The results of this study have shown that the computed tomography staging system based on computed tomography extent of disease after medical therapy is a simple, easily remembered, and very effective modality for the classification of chronic sinusitis. This system provides a rationale for discussing and planning surgery with patients and physicians and is a convenient reference for the reporting of end results. More importantly, a linear relationship between disease stage and outcomes is demonstrated. This statistically highly significant feature of the staging system provides a firm basis for the production of outcomes after various treatment strategies, particularly ethmoidectomy and the treatment of sinusitis.

Evaluation of pulse oximetry in horses surgically treated for colic.

All 43 horses anaesthetised for colic surgery were premedicated with xylazine or diazepam. Anaesthesia was induced with guaifenesin and ketamine, horses were placed in dorsal recumbency and anaesthesia was maintained with isoflurane in oxygen and mechanical ventilation. Haemoglobin saturation readings (SpO2) were taken with a pulse oximeter and compared with computed haemoglobin saturation (SaO2) from arterial blood samples. Readings were taken over a range of SaO2 of 78-100%, mean arterial blood pressure ranged from 24 to 108 mmHg and PaO2 ranged from 53 to 490 mmHg. Analysis of 107 readings showed that SpO2 values predicted SaO2 but time, blood pressure and individual horse did not. Correlation coefficients between SpO2 and SaO2 were 0.85 for all values and 0.88 for values at 30 min. Values for bias and precision were calculated for all SpO2 values and for readings separated into 3 saturation groups: normal, low normal, and abnormal. The pulse oximeter tended to underestimate SaO2 at all times, and was less precise as the saturation decreased.

Clinical evaluation of an infusion of xylazine, guaifenesin and ketamine for maintenance of anaesthesia in horses.

General anaesthesia was maintained in 40 horses by the continuous intravenous infusion of a mixture of 500 ml 10% guaifenesin solution, 1 g ketamine and 500 mg xylazine. The median duration of infusion was 65 mins (interquartile range 51-95 mins). Anaesthesia was characterised by active palpebral reflexes, variable degrees of nystagmus and occasional swallowing. Swallowing was considered to be undesirable in horses undergoing laryngeal surgery, but the infusion produced satisfactory conditions for all other surgical procedures performed. Arterial blood pressure was well maintained in all cases (median mean arterial blood pressure = 85 mmHg after 30 mins anaesthesia). Heart rate and PaCO2 were significantly lower, whilst PaO2 was significantly higher in the infusion group than in a group of paired control horses which were anaesthetised with halothane. Recovery from anaesthesia was good (Grades 1-2) in 33 horses. Median times to sternal recumbency and to standing were 24 and 38 mins respectively. The infusion caused a significant fall in packed cell volume, haemoglobin concentration and red blood cell count (P < 0.01) and a significant rise in plasma glucose concentration (P < 0.01). These variables returned to pre-infusion values within 24 h.

Effects of 5% and 10% guaifenesin infusion on equine vascular endothelium.

Twelve horses of various breeds and either sex were anesthetized with xylazine and ketamine injected into a median or lateral thoracic vein. During anesthesia, with the horse in sternal recumbency, a 14-gauge, 8.9 cm catheter was inserted into each jugular vein by using aseptic technique. Guaifenesin in water (100 mg/kg or a maximum dose of 50 grams) was infused into one jugular vein and an equal volume of 0.9% saline solution was infused into the other jugular vein. Seven horses received 10% guaifenesin, and five horses received 5% guaifenesin. The catheters were removed before the horses recovered from anesthesia. The horses were euthanatized approximately 48 hours later, and the jugular veins were removed for histologic examination. Adherent thrombus material was observed in all veins exposed to 10% guaifenesin and in one vein exposed to 5% guaifenesin. No evidence of thrombus was observed in four veins infused with 5% guaifenesin or in those infused with saline solution. These findings are of particular significance with horses at increased risk for thrombosis or thrombophlebitis.

[Continuous intravenous anesthesia in dogs using a combination of xylazine, ketamine and guaifenesin]. / Kontinuální intravenózní antestézie psa smesí xylazinu, ketaminu a guaifenezinu.

The tested anaesthesia through a permanent infusion of a xylazine, ketamine and guaifenezine (XKG) mixture was used in ten experimental dogs without clinical signs of a disease and in fifty two patients during different surgical interventions. After joint i.m. atropine (0.05 mg/kg) and xylazine (2 mg/kg) premedication, anaesthesia in dogs was induced by an i.v. administration of 1% ketamine at a dose of 2 mg/kg, and the XKG was infused instantly after the previous treatment. The mixture contained 2.0 ml of 5% ketamine and 1.25 ml of 2% xylazine added to 100 ml of 5% guaifenezine. The infusion was applied at a rate of 3.3 ml/kg for the first five minutes and then it was maintained at constant values of 2.2 ml/kg during the whole surgical intervention (Tab. I). The induction and course of anaesthesia, and waking up and recovery from anaesthesia were evaluated in all dogs, and the trias values were also followed. These additional parameters were followed in the test group: breathing volumes, ECG values and acid-base balance parameters were determined from the collected blood samples. The observation of measurable parameters (Figs. 1 to 5) and ECG analysis did not demonstrate any large departures from the starting values, and the changes in the acid-base balance (Tab. II) suggest the partly compensated respiratory acidosis. On the basis of our results, we can recommend this tested method for general anaesthesia particularly of dogs of larger breeds and for longer-lasting operations. This method is suitable to be used first of all in the veterinary establishments where inhalation anaesthesia is not practicable.

A retrospective survey of anaesthesia in horses with colic.

The purpose of this survey was to identify complications occurring in horses with colic during anaesthesia and recovery from anaesthesia; and to determine any relationships between these complications and drugs used for induction or maintenance of anaesthesia. Two hundred and thirty nine horses were anaesthetised on a total of 250 occasions for colic surgery between January 1985 and May 1987. Of these, 189 recovered from 200 anaesthetic episodes. Most horses received xylazine and guaifenesin with either thiobarbiturate (68 per cent) or ketamine (24 per cent) and anaesthesia was maintained with either halothane (51 per cent), isoflurane (43 per cent), or first halothane then isoflurane (6 per cent). Sixty nine per cent also received an opioid. Hypotension or tachycardia were recorded in 15 and 13 per cent of anaesthesias, respectively. Arterial PO2 was less than 13.3 kPa in 17 per cent of 175 anaesthesias. None of these complications was associated with a specific anaesthetic agent. Hypertension was recorded in 11.5 per cent of anaesthesias and occurred more frequently during isoflurane anaesthesia (P < 0.05). The mean duration of anaesthesia was 126 mins (range, 50-270 mins), and was not different for horses receiving thiobarbiturate or ketamine, halothane or isoflurane. The time taken to stand after anaesthesia recorded on 149 occasions and was 63 +/- 24 mins (range, 15-135 mins). This was not different for the different anaesthetic agents. Horses that were excited or had difficulty standing up during recovery had a significantly longer duration of anaesthesia (165 +/- 51 mins) (P < 0.05) but no specific anaesthetic agent was involved. Of the 189 horses, 148 (75 per cent) survived and were discharged from the hospital. Horses that did not survive had a significantly increased prevalence of anaesthetic complications, and longer durations of anaesthesia.