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The middle-latency auditory-evoked potential (MLAEP) has been investigated as means of monitoring anesthesia in dogs. The goals of this study were to develop a technique to record MLAEPs in awake dogs and to determine the effects of sedation. The MLAEP was recorded in 12 dogs with and without sedation with acepromazine. Three needle electrodes were inserted SC. Click stimuli were delivered biaurally. Signal acquisition, averaging, and analysis were performed by software developed in-house. Signals were recorded for 128 milliseconds, and the responses to 1,024 stimuli were averaged. The waveforms from 10 recordings were averaged, and the amplitudes and latencies of peaks that could be consistently identified were measured. Data measured were compared by means of a paired 2-sided Student's t-test. Interpretable MLAEPs were recorded in 10 of the 12 dogs. Three peaks were consistently identified (Pa, Nb, and Pb). The latencies of these peaks were significantly (P = .032, .035, and .028, respectively) shorter in awake (mean +/- SD milliseconds) (Pa = 18.85 +/- 1.36, Nb = 30.50 +/- 3.55, and Pb = 47.70 +/- 5.53) than in sedated (Pa = 22.40 +/- 3.88, Nb = 35.75 +/- 6.77, and Pb = 55.30 +/- 10.55) dogs. The Pb amplitude was not significantly different (2.51 +/- 1.30 microV awake and 2.19 +/- 1.10 microV sedated). This study demonstrates that acepromazine sedation causes changes in MLAEP.

To standardise the method of eliciting somatosensory-evoked potentials (SEPs), SEPs were generated by electrical stimulation of different stimulus sites and recorded bilaterally from the primary somatosensory cortex (S1) and from midline in awake, freely moving rats. Increasing stimulus intensity enhanced amplitudes of all SEPs. At supramaximal stimulation, SEPs following vibrissae and tail stimulation (V-SEP and Ta-SEP, respectively) but not following trunk stimulation (Tr-SEP), fulfilled our criterion of signal-to-noise ratio >or=4. The first V-SEP component coincided with a stimulus artefact, disqualifying these recordings for a standard stimulation protocol. The Ta-SEP generated stable and reproducible recordings and was considered to be the preferred technique. Early components of the contralateral S1 recorded V-SEP and Tr-SEP occurred at latencies different from the other recordings. Increasing stimulus repetition rate (SRR) decreased amplitudes of all SEPs. At the highest obtainable SRR, the amplitude between the V-SEP second positive and second negative components in all recordings was 70-80% of the amplitude at 0.1 Hz, whereas peak amplitudes of subsequent components and those of the Tr-SEP and Ta-SEP were 20-50%. These results indicate that the different SEP components might be generated by different ascending neural pathways.

Physiological parameters, metabolic parameters and stress-related hormones are evaluated in horses anaesthetized with isoflurane in oxygen combined with lidocaine intravenously. Two groups of horses anaesthetized with isoflurane (six horses in each group) were studied: a lidocaine group (IL), which received intravenous lidocaine and a control group (C), which received intravenous saline. Horses in both groups were premedicated with detomidine (i.v.), and anaesthesia was induced with midazolam-ketamine (i.v.). The lidocaine group received intravenous lidocaine as a loading dose of 2.5 mg kg(-1) at 15 min after induction of anaesthesia directly followed by a maintenance dosage of 50 microg kg(-1) min(-1), while the control group received saline (i.v.) following the same regime. End-tidal isoflurane and standard physiological parameters were measured. Blood was sampled for measurement of lidocaine, stress hormones and metabolic parameters. The end-tidal isoflurane concentration in the lidocaine group was 0.96 +/- 0.06% versus 1.28 +/- 0.06% (mean +/- SD) in the control group, a significant (P < 0.05) reduction of 25%. No significant differences were found regarding stress-related hormones, metabolic and physiological parameters. This study suggests that the use of lidocaine to decrease the concentration of isoflurane to obtain a sufficient surgical anaesthesia has no subsequent effects on physiological and metabolic parameters or stress-related hormones.

To develop an alternative anaesthetic regimen for cats with cardiomyopathy, the cardiopulmonary effects of three different premedication-induction protocols, followed by one hour maintenance with isoflurane in oxygen: air were evaluated in six cats. Group I: acepromazine (10 microg/kg) + buprenorphine (10 microg/kg) IM, etomidate (1-2 mg/kg) IV induction. Group II: midazolam (1 mg/kg) + ketamine (10 mg/kg) IM induction. Group III: medetomidine (1.5 mg/m2 body surface) IM, propofol (1-2 mg/kg) IV induction. Heart rate, arterial blood pressure, arterial blood gases, respiration rate, and temperature were recorded for the duration of the experiment. In group I the sedative effect after premedication was limited. In the other groups the level of sedation was sufficient. In all groups premedication resulted in a reduced blood pressure which decreased further immediately following induction. The reduction in mean arterial pressure (MAP) reached statistical significance in group I (142+/-22 to 81+/-14 mmHg) and group II (153+/-28 to 98+/-20 mmHg) but not in group III (165+/-24 to 134+/-29 mmHg). Despite the decrease in blood pressure, MAP was judged to have remained within an acceptable range in all groups. During maintenance of anaesthesia, heart rate decreased significantly in group III (from 165+/-24 to 125+/-10 b.p.m. at t=80 min). During anaesthesia the PCO2 and PO2 values increased significantly in all groups. On the basis of the results, the combination acepromazine-buprenorphine is preferred because heart rate, MAP, and respiration are acceptable, it has a limited sedative effect but recovery is smooth.

We investigated whether components from the rat Vx-MLAEP could be used to assess depth of anaesthesia induced by propofol. Propofol decreased MLAEP amplitudes and increased latencies. We propose that the P(16)-N(22) wave in the rat MLAEP is similar to the human P1, and that recovery of this wave during propofol anaesthesia correlates with behavioural measures of the regaining of consciousness.

Medetomidine, a highly specific alpha-2 adrenergic agonist, has been demonstrated to lower intraocular pressure (IOP) in rabbits and cats when applied topically. The purpose of this study was to assess the influence of intravenously injected medetomidine on the pupil size (PS) and the IOP of non glaucomatous dogs. IOP was measured by applanation tonometry and PS was measured using Jameson calipers at t=0 (or time of IV injection of medetomidine (Domitor; Orion) at the dose of 1500 microg/m2 body surface area) and again after 5 minutes (t=5). The IV administration of medetomidine caused miosis in all 14 dogs. The mean PS decreased from 9.0 to 4.0 mm (p<0.001). The IOP was lowered in 10 dogs and in 4 dogs there was a rise in IOP. The mean IOP (mmHg) decreased from 22 to 21 (p>0.2). The data presented above confirm that medetomidine at a dose of 1500 microg/m2 body surface area produces miosis in non glaucomatous dogs, without influencing the IOP.

The effect of unilateral or bilateral transection of the superior laryngeal nerve on the electromyographic activity in the hyopharyngeal, thyropharyngeal, and cricopharyngeal muscles was studied in 10 dogs during eating and during unilateral electrical stimulation of the solitary nucleus. In all groups of dogs, after unilateral or bilateral transection, there were some swallowing actions in which the sequence of activity in the pharyngeal muscles was disturbed during eating and during stimulation of the solitary nucleus. In the dogs in which the transection was unilateral, this fraction was 18% in the ipsilateral muscles during eating and 7% in the contralateral muscles. After bilateral transection it was 8% in the left muscles and 16% in the right muscles. The fractions were not significantly different when swallowing was evoked by stimulation of the solitary nucleus. Swallowing actions having a normal sequence of activity in these dogs were compared with those in a group of eight dogs in which the superior laryngeal nerves were intact. Contraction timing was not significantly different during eating, but during stimulation of the solitary nucleus the timing was significantly shorter than in the dogs with intact nerves. It was concluded that superior laryngeal nerve transection modulates the central pattern generator for pharyngeal swallowing in dogs.

Electroencephalography (EEG) was applied to evaluate the validity of the paw pinch reflex as an indicator of anaesthetic depth in rats which are anaesthetized with a single intraperitoneal dose of pentobarbital. After induction of the anaesthesia, characterized by the rapid loss of the animals' ability to maintain upright posture, the EEG of 10 out of 11 rats was dominated by paroxysmal (burst suppression) activity, associated with unconsciousness. In seven out of 11 rats, the paw pinch reflex was lost after onset of paroxysmal electroencephalographic activity. However, the paw pinch reflex remained present in four out of 11 animals, demonstrating that the response is independent of cortical activity. In five out of seven rats, the EEG still showed paroxysmal activity when the paw pinch reflex was regained. However, in two other rats the EEG returned to a pattern similar to that shown by awake animals, 4 and 21 min respectively, before the reflex was regained. These data indicate that in the pentobarbital-anaesthetized rat, presence of the paw pinch reflex is not related to the level of depression of electrical activity in the cerebral cortex, and consequently is probably not related to the level of consciousness. Based upon these findings it is concluded that the paw pinch reflex is unreliable as a sole indicator of anaesthetic depth.

Methods for the humane killing of animals are watched critically by both the public and the veterinary community. Evaluation of such methods requires assessment of efficacy as well as emotional and ethical aspects. Rapidity of loss of consciousness is a crucial factor in such evaluations. In the present study, four methods for piglet euthanasia were compared with regard to presence of indicators of discomfort (pain, anxiety, stress) and rapidity of onset of death, defined as the absence of breathing, heart beats and reflexes, combined with isoelectricity of the electro-encephalogram (EEG). The study was performed on piglets, which had to be destroyed on account of preventive measures against swine fever. The following methods were applied: CO2 98%, CO2/O2 65/35%, T61 and pentobarbital (Euthesate) injected intracardially. Intracardial injections of T61 and pentobarbital provide fast unconsciousness and death with minimal discomfort to the animal.

This article reviews the present state of the art of resuscitation of dogs and cats. The purpose of resuscitation is to revive animals so that the vital functions resume together with a normal brain function. Resuscitation must be started as soon as the cardiopulmonary arrest has been confirmed. Adequate ventilation and effective circulation to the most vital body organs, the heart and the brain, have the highest priority. They can be achieved by endotracheal intubation, artificial ventilation with 100% oxygen and rhythmic compression of the closed chest or direct cardiac massage following thoracotomy. Medical therapy is an important part of resuscitation. In the absence of a central venous route, deep endotracheal administration is the preferred method of administration. Most medications can be administered through the endotracheal tube in this fashion.

Combinations of medetomidine with either propofol or ketamine were compared for the sedation and induction of anaesthesia in dogs undergoing a variety of surgical (60 per cent) and non-surgical (40 per cent) procedures. Eighty-four dogs were used at four sites. Medetomidine was administered intramuscularly at a dose of 1000 micrograms/m2 body surface area 10 to 15 minutes before the induction of anaesthesia by the administration of propofol (n = 44) or ketamine (n = 40) dosed to effect. The dogs became sedated by medetomidine after a mean (sd) time of 6.7 (5.4) minutes, and their heart rates and respiration rates decreased. Sixteen of the dogs suffered an adverse effect, 13 of them vomited. Anaesthesia was induced by the intravenous administration of propofol (2.1 [0.7] mg/kg) or ketamine (3.7 [1.9] mg/kg), and further doses of the anaesthetic were given, depending on the length of the operation, once in 17 per cent, twice in 11 per cent and three or more times in 24 per cent of the cases. The heart rate of the dogs anaesthetised with ketamine was significantly higher than that of the dogs anaesthetised with propofol, but there were no other significant physiological differences. There were 11 adverse side-effects in the ketamine group compared with five in the propofol group and they were generally more severe. The quality of the recovery from anaesthesia was considered to be smooth in 89 per cent of the propofol group but in only 63 per cent of the ketamine group.

In this article a review will be given of the groups of anaesthetics used for animal capture, their developmental history, mode of action and indication for use. A table with dosages of locally--in the Netherlands--available drugs will be presented for a number of animal species.

The effect of stimulating peripheral and central neural pathways on the electromyographic activity in the hyopharyngeal, thyropharyngeal, and cricopharyngeal muscles was studied in eight dogs during 1) eating, 2) unilateral electrical stimulation of the superior laryngeal nerve, and 3) unilateral electrical stimulation of the solitary nucleus. The duration of pharyngeal swallowing was significantly shorter during eating than during stimulation of the solitary nucleus in the anesthetized dog (mean difference 127 ms, SEM 9, n = 15). The duration of pharyngeal swallowing was significantly shorter during eating than during stimulation of the superior laryngeal nerve in the awake dog (mean difference 84 ms, SEM 13, n = 9). The duration of pharyngeal swallowing during stimulation of the superior laryngeal nerve under anesthesia was significantly shorter than during stimulation of the solitary nucleus under anesthesia (mean difference 58 ms, SEM 18, n = 9). The difference in duration of pharyngeal swallowing during stimulation of the superior laryngeal nerve between the awake state and during anesthesia was not significant (mean 19 ms, SEM 14, n = 9). It was concluded that stimulation of peripheral and central neural pathways resulted in different pharyngeal muscle contraction timing during swallowing in dogs.

During the last decades, an increase is apparent in the use of analgesics for laboratory animals in situations where this was previously considered unnecessary. Mice with advanced tumours often show clear signs of discomfort which may be a result of chronic pain or a result of general ill-being. The syngeneic murine tumour model most frequently used in our experiments was used to investigate whether this discomfort can be reduced with an analgesic. Twenty DBA/2 mice bearing SL2 lymphoma were given 0.5 mg/kg buprenorphine (Temgesic) in food gel twice daily, 20 tumour-bearing mice were given control food gel at the same times. Indicators of well-being were monitored daily. These included behavioural parameters such as exploration, grooming, and posture; food and water consumption and fur quality. All mice showed a clear increase of discomfort with time: explorative behaviours and grooming decreased, while sitting in hunched posture increased. Food and water consumption and fur quality also decreased. Major significant differences between the buprenorphine treated group and the control group were not apparent. In conclusion, we could not document a positive effect or buprenorphine on discomfort in mice as evaluated by our scoring system. It remains possible that pain itself was not the primary cause of the discomfort in mice bearing these tumours, or that the analgesic effect of buprenorphine was insufficient under these circumstances.

For the determination of the logarithmic partition coefficients between n-octanol and water (log P(o/w)) of local anesthetics, the pH of the aqueous phase needs to be adjusted to high values to ensure that the local anesthetics are in the unionized form. Using the shake-flask or the stir-flask method, this high pH may catalyze hydrolysis, leading to increasing amounts of impurities in time. These impurities exclude non-selective quantification methods like UV spectrometry and require repetitive quantitative analysis of both liquid phases resulting in a tedious and time-consuming method. A rapid reversed-phase HPLC method was developed to measure log P(o/w) of the local anesthetics N-butyl-p-aminobenzoate, methyl-p-aminobenzoate, benzocaine, procaine, mepivacaine, prilocaine, lidocaine, bupivacaine, etidocaine, tetracaine and oxubuprocaine.

In a series of three review articles different aspects of wild animal immobilization under Dutch conditions will be discussed. The first article deals with the available equipment for remote anaesthesia, their indications for use and some basic darting principles. Part two discusses the various anaesthetics used in wild animal immobilization and their clinical pharmacological properties. A table with effective anaesthetic combinations for ten different species is presented. The third article discusses safety measures and complications which can occur when dealing with wild animal anaesthesia.

The use of a combination of medetomidine and ketamine as anaesthetic for dental surgery was investigated in 60 dogs. The nature of the interventions varied from inspection of the teeth with cleaning of the teeth or simple tooth extraction to extraction of one or more dental elements or endodontic treatment. The operations lasted between 20 and 70 minutes, with an average of 34 +/- 15 minutes. Medetomidine, 1000 micrograms/m2 body surface administered intramuscularly, was used as premedication. Anaesthesia was induced with intravenously administered ketamine at a dose of 2-3 mg/kg body weight. The effect of premedication was 'good' in 79.5% of patients, 'moderate' in 12%, and 'poor' in 8.5%. Seven patients were given additional 50% medetomidine, which caused the proportion of animals with 'good' premedication to increase to 91.5%. Twelve of the 60 patients showed convulsion-like symptoms of varying severity directly after the administration of ketamine. In 4 patients the tonic cramps were considered severe enough to warrant once-only administration of midazolam. The quality of anaesthesia in the maintenance phase was considered 'good' in 88% of the patients and 'moderate' in 12%. Recovery was 'good' in 74% of the patients, 'moderate' in 11%, and 'poor' in 15%. Heart rate after premedication with medetomidine was 53 +/- 3 beats per minute and increased to 86 +/- 4 beats per minute (P < 0.05) after administration of ketamine. It thereafter decreased, over a period of 20 minutes, to 60 +/- 3 beats per minute. The respiration rate was 15 +/- 1 per minute and remained unchanged throughout the operation. After completion of surgery, medetomidine was antagonized with atipamezole (2500 micrograms/m2) given intramuscularly. In 13% of the animals the recovery period was characterized by tremors and restlessness. It can be concluded that the combination medetomidine and ketamine provides adequate analgesia, hypnosis, and muscle relaxation for various dental surgical interventions to be performed.

This study evaluated the quality of anaesthesia and the cardiorespiratory effects induced by the combination of medetomidine with either ketamine, propofol or fentanyl. Medetomidine premedication (1000 or 1500 micrograms/m2 body surface area) was followed by intravenous induction of anaesthesia with ketamine (3.0 mg/kg), propofol (2.0 mg/kg) or fentanyl (2.0 micrograms/kg) in bitches undergoing elective ovariohysterectomy. Anaesthesia was prolonged by incremental doses of the induction agents as necessary. The mean (sem) overall doses (including induction) were 0.09 (0.01) mg/kg/min for ketamine, 0.06 (0.01) mg/kg/min for propofol and 0.07 (0.005) microgram/kg/min for fentanyl during procedures which lasted 88 (6) minutes, 72 (3) minutes and 79 (7) minutes, respectively. At the end of the procedure, medetomidine was antagonised with atipamezole. The quality of anaesthesia, heart rate and arterial blood pressure were recorded continuously and arterial blood gases were measured at intervals. At the end of the procedure, the animals received 10 micrograms/kg buprenorphine intramuscularly for postoperative analgesia. From the adequacy of anaesthesia, the lack of significant adverse side effects and the reliable and rapid recovery it is concluded that, in healthy dogs anaesthetised with ketamine or propofol, medetomidine is a satisfactory sedative-analgesic premedicant. The differences in haemodynamics and the quality of recovery suggest that the combination of medetomidine with propofol provided the better quality anaesthesia. The combination of medetomidine with fentanyl was unsuitable for obtaining surgical anaesthesia in spontaneously breathing animals owing to the severity of the respiratory depression at dosages needed for general anaesthesia.

The use of a combination of medetomidine and ketamine as anaesthetic for dental surgery was investigated in 60 dogs. The nature of the interventions varied from inspection of the teeth with cleaning of the teeth or simple tooth extraction to extraction of one or more dental elements or endodontic treatment. The operations lasted between 20 and 70 minutes, with an average of 34 +/- 15 minutes. Medetomidine, 1000 m g/m2 body surface administered intramuscularly, was used as premedication. Anaesthesia was induced with intravenously administered ketamine at a dose of 2-3 mg/kg body weight. The effect of premedication was 'good' in 79.5% of patients, 'moderate' in 12%, and 'poor' in 8.5%. Seven patients were given additional 50% medetomidine, which caused the proportion of animals with 'good' premedication to increase to 91.5%. Twelve of the 60 patients showed convulsion-like symptoms of varying severity directly after the administration of ketamine. In 4 patients the tonic cramps were considered severe enough to warrant once-only administration of midazolam. The quality of anaesthesia in the maintenance phase was considered 'good' in 88% of the patients and 'moderate' in 12%. Recovery was 'good' in 74% of the patients, 'moderate' in 11%, and 'poor' in 15%. Heart rate after premedication with medetomidine was 53 +/- 3 beats per minute and increased to 86 +/- 4 beats per minute (P < 0.05) after administration of ketamine. It thereafter decreased, over a period of 20 minutes, to 60 +/- 3 beats per minute. The respiration rate was 15 +/- 1 per minute and remained unchanged throughout the operation. After completion of surgery, medetomidine was antagonized with atipamezole (2500 m g/m2) given intramuscularly. In 13% of the animals the recovery period was characterized by tremors and restlessness. It can be concluded that the combination medetomidine and ketamine provides adequate analgesia, hypnosis, and muscle relaxation for various dental surgical interventions to be performed.

Background: Epidural administration of an aqueous suspension of n-butyl-p-aminobenzoate (BAB) to humans results in long-lasting sensory blockade without motor block. The dose-response of BAB administered epidurally and intrathecally as a solution was studied in rats to define the local anesthetic properties in an established animal model., Methods: The time course of changes in tail withdrawal latency and motor function were determined in rats after epidural or intrathecal administration of solutions of BAB or bupivacaine. The dose-response relation was determined and median effective dose values were calculated., Results: After epidural and intrathecal administration of BAB solutions, the onset and duration of the antinociceptive action were comparable to bupivacaine. Median effective dose values for tail-withdrawal latency of 6 s or more were significantly greater for BAB. After both routes of administration, BAB clearly affected motor function., Conclusions: When administered epidurally and intrathecally as a solution, BAB is a local anesthetic of relative low potency with onset and duration of action comparable to those of bupivacaine. These findings suggest that the long-lasting action obtained after applying BAB suspension results from the slow dissolution (continuous release) of the solid BAB deposited in the epidural space.

We investigated the effects of combinations of the alpha 2-agonist medetomidine with either ketamine or propofol for their overall quality of anaesthesia, including the possible concomitant changes in respiratory and circulatory function in New Zealand White rabbits. Medetomidine was administered at 0.35 mg/kg, intramuscularly. Following sedation, ketamine (5 mg/kg) or propofol (2 and 3 mg/kg) were administered intravenously via the ear vein. Data on reflexes (palpebral, corneal, ear-pinch and toe-pinch), jaw muscle tone and physiologic parameters (heart rate, blood pressure, respiration rate, body temperature) were recorded before and after administration of drugs. Intermittent arterial blood sampling was performed at predetermined intervals before and after anaesthesia. The results show that the ear-pinch and toe-pinch reflexes and the jaw muscle tone are reliable indices to determine surgical anaesthetic depth. A surgical level of anaesthesia could be obtained reliably with the combination medetomidine-ketamine and medetomidine-propofol (3 mg/kg) with a duration of 19 min (variation 10 to 40 min, n = 6) and 11 min (variation 5 to 15 min, n = 6), respectively. Propofol administered at 2 mg/kg did not produce an adequate anaesthetic level. The data from this study demonstrate a high degree of predictability in achieving a fast induction and adequate anaesthetic depth together with a low incidence of untoward side-effects and a zero mortality with the combinations investigated. The data from the medetomidine-ketamine group show that, although adequate anaesthetic depth of medium duration is achieved, the arterial oxygen tension is reduced to hypoxemic levels. With the use of this combination, the supplemental administration of oxygen is advised. With the combination of medetomidine-propofol (3 mg/kg) a short duration anaesthesia of adequate depth was achieved, whereby physiological variables all remained within acceptable ranges. The use of medetomidine-propofol, in combination with the alpha 2-antagonist atipamezole to shorten recovery time, will provide reliable and very versatile anaesthesia in rabbits.

A fast capillary gas chromatographic method with nitrogen-selective detection is described that allows selective and reproducible quantification of n-butyl-p-aminobenzoate (BAB) and lidocaine in plasma. The sampling and sample storage conditions are critical for the quantification of BAB. Diisopropyl fluorophosphate, an organo-phosphorus pesticide, has to be added during sampling to prevent the rapid decomposition of BAB by cholinesterases.

Veterinary textbook on anaesthesia in birds that volatile anaesthetics can accumulate in the air sac system during spontaneous respiration of birds anaesthetized with inhalational anaesthetics. In order to quantify the extent of accumulation, air samples were collected from the endotracheal tube and from the left abdominal air sac of ten pigeons anaesthetized with O2, NO2, and isoflurane. In this way, O2, CO2, and isoflurane concentrations were measured continuously at two places, during both spontaneous respiration and positive pressure ventilation. During spontaneous respiration, CO2-concentrations were higher in the air sac than in the endotracheal tube in 60% of the animals. The average difference for the whole group was 0.8 volume per cent; individual differences were as high as 2.9 volume per cent. The concentration of isoflurane was on average 1.1 volume per cent lower in the abdominal air sac than in the endotracheal tube. During mechanical ventilation, the percentage of CO2 was lower in the abdominal air sac than in the endotracheal tube in all pigeons. At the same time, the differences between isoflurane concentrations in the endotracheal tube and air sac decreased. Thus the results of our study with isoflurane-anaesthetized pigeons do not support the suggestion that volatile anaesthetics accumulate in the air sacs of spontaneously breathing birds anaesthetized with inhalation anaesthetics. The results also show that, under these conditions, CO2 concentrations in the endotracheal tube can only be measured reliably during positive pressure ventilation.

The necropsy findings of 85 cats that died up to six weeks after administration of injectable anaesthetics are described. The most obvious findings in these cats were degeneration and necrosis of heart muscle fibres followed and related to time after the administration of the anaesthetics, by infiltration of predominantly mononuclear cells and by an increase in collagenous connective tissue. The lesions were most obvious on the inner side of the myocardium, indicating that hypoxic injury occurred during anaesthesia. The possible mechanism of the damage to the heart and its role in the pathogenesis of cardiomyopathy in the cat is discussed.

Before a decision on the anesthetic protocol and the various patient support measures can be taken, the pathophysiological changes that occur during a gastric dilatation-volvulus need to be evaluated. The most important changes are of a circulatory and/or respiratory nature, inducing hypotension, hypovolaemia, cardiac dysrhythmias, a decreased respiratory minute volume, and subsequently resulting in changes in the acid-base balance and plasma electrolyte concentration. In view of these changes and the increased anaesthetic risk for the patient with gastric dilatation-volvulus, the use of barbiturates or ketamine cannot be recommended for anaesthetising these patients. With the use of neurolept-analgesic combinations, such as methadone-droperidol or sufentanil-midazolam, an increased cardiovascular stability and an ample analgesic effect can be obtained. Especially with the potent sufentanil in combination with midazolam, an excellent anaesthesia for patients with gastric dilatation-volvulus can be achieved.

We investigated pressure-dependent autoregulatory responses in mesenteric, iliac, and renal vascular beds of conscious dogs during intravenous infusion of angiotensin II, phenylephrine, or arginine vasopressin at rates which increased arterial pressure by 20-40 mmHg. The arteries supplying these beds were instrumented with an electromagnetic flow probe, a nonoccluding catheter, and an electromagnetic flow probe, a nonoccluding catheter, and an occluder cuff connected with a servo-amplifier, which enabled us to return perfusion pressure to control levels during infusion of the vasoconstrictor agents. We attempted to differentiate between the increase in vascular resistance due to the direct effect of the vasoconstrictor agent and the increase induced by an autoregulatory response induced by elevations of aortic perfusion pressure. We measured a strong degree of autoregulation in the renal vascular bed with a fractional compensation value close to 1. Moderate autoregulation occurred in the mesenteric vascular bed, where the compensation was 0.4-0.5 with angiotensin II and phenylephrine and between 0.74 and 0.94 with vasopressin. No autoregulatory capacity could be demonstrated in the hindlimb. The findings indicate that, under conditions of increased systemic blood pressure, both the renal and the mesenteric vascular beds contribute to the increase in total peripheral resistance by pressure-dependent vasoconstrictor responses.

An aqueous suspension of n-butyl p-aminobenzoate (BAB), a highly lipid-soluble congener of benzocaine, was applied epidurally and around ulnar nerves in dogs. The suspension consisted of 10% BAB and 0.025% polysorbate in 0.9% NaCl. Sensory effects were tested by electrical stimulation. Three epidural injections were given, and the dogs were killed after 21 days. The increase in stimulation threshold was comparable to the effect of lidocaine in a concentration between 0.5% and 1%. Increased sensory threshold lasted for days, whereas no long-lasting motor effects were observed. Pathomorphologic changes were found primarily in the dorsal spinal nerve roots, although slight changes were also found in the ventral spinal roots. White matter degeneration was found only in the lumbar dorsal columns. This result suggested Wallerian degeneration in the dorsal spinal nerves and was at variance with recently published data on epidural BAB. No changes were observed in the ulnar nerves. The authors demonstrated that the pathomorphologic changes were induced by the BAB suspension and not by the suspending additive polysorbate 80. It was postulated that the suspension of BAB, which contains particles of a median size of 15 microns, was mainly confined to the dorsal epidural space where neurolytic changes in axons of the dorsal spinal nerve roots and dorsal columns are induced. This may explain the long-lasting sensory effects seen in intractable cancer pain patients after epidural BAB administration. More research is necessary to define the distribution of BAB in nervous tissue after its epidural administration and to better characterize toxicity, neurolytic effects, and regeneration of nervous tissue after BAB administrations.

In the present paper, findings on the use of ketamine/xylazine, ketamine/midazolam, tiletamine/zolazepam, and medetomidine following intramuscular injection in dogs are reported. The combined use of ketamine/xylazine induced anaesthesia, the duration of which was thirty minutes. Untoward side-effects were not observed. Administration of tiletamine/zolazepam failed to induce a surgical level of anaesthesia. Recovery was prolonged. In this group, five out of the ten dogs showed signs of post-anaesthetic muscle spasms. Neither the combination ketamine/midazolam nor medetomidine induced a surgical level of anaesthesia. Post-anesthetic muscle spasms were a frequently observed side-effect when the combination ketamine/midazolam was administered. The use of medetomidine resulted in a qualitatively satisfactory and prolonged sedation.

A number of experiments was carried out to determine the sequence of events leading to death following administration of the euthanizing agent T61. Simultaneous recordings of the EMG, EEG, ECG and end-tidal CO2 (dogs only) were obtained in acutely instrumented rabbits and dogs. Results show that following T61 administration the loss of consciousness and loss of muscle activity occurred simultaneously. Vocalization and increased muscle movement occurred in the initial phase of the injection in 3 of 8 dogs, injected with T61 or butyramide. From this study it was concluded that the presence of the muscle relaxant does not pose an ethical problem for the use of T61 as an euthanizing agent, but our results suggest that the use of T61 may have some emotionally unpleasant side-effects.

Experiments were carried out to determine the onset of loss of consciousness and muscle relaxation following administration of the euthanising agent T61. Simultaneous recordings of EMG, EEG, ECG and capnogram (dogs only) were obtained in acutely instrumented rabbits and dogs. The results showed that loss of consciousness and muscle activity occurred simultaneously following administration of T61. Vocalisation and increased muscle movement occurred both when T61 and butyramide were used in the initial phase of the injection in three out of eight dogs. From this study, it was concluded that the presence of the muscle relaxant does not pose an ethical problem for the use of T61 as euthanising agent, though the results suggested that the use of T61 may have some emotionally unpleasant side-effects.