Electroencephalographic recordings in dogs suffering from idiopathic and symptomatic epilepsy: diagnostic value of interictal short time EEG protocols supplemented by two activation techniques

The diagnostic value of interictal short time electroencephalographic (EEG) recordings in epileptic dogs under general anaesthesia with propofol and the muscle relaxant rocuronium bromide was investigated. Two activation techniques, namely photic stimulation and hyperventilation, were evaluated for their potential to enhance the diagnostic validity of these recordings. Sixty-one dogs suffering from idiopathic epilepsy and 28 dogs suffering from symptomatic epilepsy were included. Electroencephalograms were recorded using five subdermal EEG electrodes (F3, F4, Cz, O1 and O2). All 89 EEGs were analysed visually and 61 were also evaluated quantitatively with fast Fourier transformation. Interictal paroxysmal epileptiform activity was found in 25% of idiopathic and in 29% of symptomatic epileptic dogs. Quantitative analysis of the EEGs (qEEGs) detected significant differences of frequency analysis in single reading points without any continuous changes of frequency bands. A comparison between healthy and affected brain hemispheres in seven dogs with focal lesions of one hemisphere did not show any significant differences in qEEG analysis. qEEG was not more sensitive than visual evaluation. Despite the use of activation techniques, the results showed that short time EEG recordings in epileptic dogs can detect interictal epileptic activity in less than one third of all seizuring dogs and is not a useful screening method.     

Electroencephalographic recordings in dogs: Prevention of muscle artifacts and evaluation of two activation techniques in healthy individuals

This study was performed to improve a standard anesthetic protocol for electroencephalography (EEG) in dogs and to evaluate the effect of photic stimulation and hyperventilation on the EEG of healthy dogs. Ten clinically and neurologically normal beagle dogs were anesthetized with propofol given intravenously with average doses of 7.5 mg/kg for induction and 0.37 mg/kg/min constant rate infusion for maintenance. Rocuronium bromide (0.4 mg/kg IV) was used as a peripheral muscle relaxant in order to prevent muscle artifacts. EEGs were recorded digitally using five subdermal needle electrodes. Photic stimulation and hyperventilation were performed to evaluate two activation techniques commonly used in human EEG recording methods. Monopolar and bipolar montages were analyzed visually and quantitatively. The use of rocuronium produced muscle artifact-free EEG recordings during the given recording procedure which indicates that rocuronium is a valuable adjunct to anesthesia during EEG recording. Photic stimulation and hyperventilation did not provoke paroxysmal discharges in the EEG of healthy dogs. Analysis of quantitative EEG data showed that background activity did not differ significantly between periods with and without stimulation. This data are important basic values and will further help to compare the effects of photic stimulation and hyperventilation of healthy dogs and those suffering from epilepsy.     

Propofol anaesthesia in cats

Propofol was administered to 49 cats to induce anaesthesia. The mean dose required was 6.8 mg/kg and this was not affected by prior administration of acepromazine maleate. In 27 cases, propofol was also used as the principal maintenance agent (mean dose rate 0.51 mg/kg/minute). Inductions were very smooth and problem free. Intubation was easily achieved in 15 cats with the aid of local desensitisation by lignocaine spray or neuromuscular relaxation by suxamethonium. Heart rate did not vary significantly during induction or maintenance of anaesthesia but respiratory rates did fall significantly. Recovery from anaesthesia was remarkably smooth in all cases and there was no significant difference in recovery times between the cats in which halothane was the principal maintenance agent and cats which received propofol alone. Side effects were seen during recovery in eight cats and included retching, sneezing and pawing of the face.     

Clinical evaluation of Alfaxan-CD® as an intravenous anaesthetic in young cats

Objective   To describe and evaluate the use of Alfaxan-CD ® as an intravenous anaesthetic in young cats.
Design   Thirty-five Domestic Short-hair cats aged from 3 to 12 months were admitted into the University Veterinary Teaching Hospital-Sydney for elective surgery. Anaesthesia was induced with Alfaxan-CD® and maintained with isoflurane: 22 cats received no premedication and 13 cats received acepromazine (0.03 mg/kg) and butorphanol (0.3 mg/kg) subcutaneously 30 min prior to induction.
Qualitative and quantitative data for induction and recovery were recorded. Physiological parameters were recorded at 0, 2 and 5 min post induction, and every 5 min thereafter until the end of the procedure.
Results   Intravenous injection of Alfaxan-CD® resulted in rapid induction of anaesthesia with a mean time to intubation of 122 s. The mean dose of Alfaxan-CD® used was 4.2 mg/kg in unpremedicated cats and 2.7 mg/kg in premedicated cats. All cats maintained a heart rate above 95 beats/min. No cat developed hypoxaemia. Hypercapnoea was detected in 4 cats and hypotension was observed in 18 cats. Time to extubation ranged from 1 to 9 min. The mean time to sternal recumbency for premedicated cats was 11 min; 77% of premedicated cats and 23% of unpremedicated cats had a recovery score of 1 or 2.
Conclusion   Alfaxan-CD® is an effective anaesthetic agent in young healthy cats, providing a smooth induction and rapid recovery. Cats that were premedicated with acepromazine and butorphanol prior to induction with Alfaxan-CD® had better recovery scores than those that were not premedicated.     

The Effects of Consecutive Day Propofol Anesthesia on Feline Red Blood Cells

This study investigated the potential for multiple exposures of propofol to induce oxidative injury, in the form of Heinz body production, to feline red blood cells. Anesthesia was induced in six healthy cats with propofol (6 mg/kg, intravenous [IV]) and maintained for 30 minutes with a propofol infusion (0.20 to 0.30 mg/kg/min, IV). The initial protocol was designed for each cat to receive 10 consecutive days of propofol anesthesia. All cats spontaneously breathed room air. Heart rate, respiratory rate, and indirect blood pressure were measured and recorded before and during anesthesia. Time to complete recovery after each infusion was measured and recorded. Heinz body analysis was performed before and after each day of propofol anesthesia. Based on predetermined criteria for discontinuing daily infusions, the mean number of consecutive days of propofol anesthesia was six and propofol administration did not continue beyond 7 days in any cat. Heart rate, respiratory rate, and indirect blood pressure did not change significantly during propofol anesthesia compared with awake values. Following the third consecutive day of propofol anesthesia, there was a significant increase from baseline in the mean percentage of Heinz bodies. Hemolysis was not detected in any cat. Recovery time significantly increased after the second consecutive day of propofol anesthesia compared with the first day. Five of six cats developed generalized malaise, anorexia, and diarrhea on day 5, 6, or 7, and two cats developed facial edema. All clinical signs resolved without treatment 24 to 48 hours after discontinuing propofol anesthesia. This study suggests that consecutive day propofol anesthesia in normal cats can induce oxidative injury to feline red blood cells in the form of excessive Heinz body formation, result in increased recovery times, and result in clinical signs of illness.     

Propofol Anaesthesia in Cats

Propofol was administered to forty nine cats to induce anaesthesia. The mean dose required was 6.8 mg/kg and this was not affected by prior administration of acepromazine maleate. In 27 cases, propofol was also used as the principal maintenance agent (mean dose rate 0.51 mg/kg/minute). Inductions were very smooth and problem free. Intubation was easily achieved in 15 cats with the aid of local desensitization by lignocaine spray or neuromuscular relaxation by suxamethonium. Heart rate did not vary significantly during induction or maintenance of anaesthesia but respiratory rates did fall significantly.     

The use of propofol for induction of anaesthesia in dogs premedicated with acepromazine, butorphanol and acepromazine-butorphanol

Cardiovascular, pulmonary and anaesthetic-analgesic responses were evaluated in 18 male and female dogs to determine the effect of the injectable anaesthetic propofol used in conjuction with acepromazine and butorphanol. The dogs were randomly divided into three groups. Dogs in Group A were premeditated with 0.1 mg/kg of intramuscular acepromazine followed by an induction dose of 4.4 mg/kg of intravenous propofol; Group B received 0.2 mg/kg of intramuscular butorphanol and 4.4 mg/kg of intravenous propofol; dogs in Group AB were administered a premeditation combination of 0.1 mg/kg of intramuscular acepromazine and 0.2 mg/kg of intramuscular butorphanol, followed by induction with 3.3 mg/kg of intravenous propofol. The induction dose of propofol was given over a period of 30-60 seconds to determine responses and duration of anaesthesia. Observations recorded in the dogs included heart and respiratory rates, indirect arterial blood pressures (systolic, diastolic and mean), cardiac rhythm, end-tidal CO, tension, oxygen saturation, induction time, duration of anaesthesia, recovery time and adverse reactions. The depth of anaesthesia was assessed by the response to mechanical noxious stimuli (tail clamping), the degree of muscle relaxation and the strength of reflexes. Significant respiratory depression was seen after propofol induction in both groups receiving butorphanol with or without acepromazine. The incidence of apnea was 4/6 dogs in Group B, and 5/6 dogs in Group AB. The incidence of apnea was also correlated to the rate of propofol administration. Propofol-mediated decreases in arterial blood pressure were observed in all three groups. Moderate bradycardia (minimum value > 55 beats/min) was observed in both Groups B and AB. There were no cardiac dysrhythmias noted in any of the 18 dogs. The anaesthetic duration and recovery times were longer in dogs premeditated with acepromazine/butorphanol.     

Effects of different propofol infusion rates on EEG activity and AEP responses in rats

Parameters calculated from the auditory-evoked potential (AEP) recorded over the auditory cortex and from the electroencephalogram (EEG) recorded over the near vertex were compared in rats at three different infusion rates of propofol (62.5, 35 and 25 mg/kg/h). Depth of anaesthesia was assessed clinically using the strength of the pedal withdrawal reflex. Well-defined AEP responses were consistently obtained. As the propofol concentration was reduced, peak latencies decreased and peak to peak amplitudes increased. Amplitude and latency values were closely associated with the strength of the pedal withdrawal responses. Parameters calculated from the EEG showed no significant change as the propofol concentration was reduced. Periods of burst suppression became more frequent as the propofol infusion rate was increased. The study showed some of the difficulties that may be encountered when using EEG as a tool to assess depth of anaesthesia during propofol infusion. The AEP showed dose dependent changes in rats at different infusion rates of propofol. However, large variability between animals limits the use of this technique for monitoring depth of anaesthesia.     

Induction of anaesthesia in dogs and cats with propofol

Propofol was used to induce anaesthesia in 89 dogs and 13 cats of either sex, various breeds and of widely different ages and weights; they varied considerably in physical condition and were anaesthetised for a variety of investigations and surgical procedures. They were premedicated with acepromazine, papaveretum, diazepam, pethidine, atropine and scopolamine in different combinations. After induction with propofol, anaesthesia was maintained with halothane, isoflurane, methoxyflurane and enflurane and, or, nitrous oxide. The mean (+/- sd) induction doses of propofol in unpremedicated and premedicated animals were 5.2 +/- 2.3 mg/kg and 3.6 +/- 1.4 mg/kg respectively for dogs, and 5.0 +/- 2.8 mg/kg and 5.3 +/- 4.3 mg/kg for cats. There were no differences between the sexes. Premedication did not affect recovery times. The incidence of side effects was very low. One dog showed evidence of pain when propofol was injected. No incompatibility was observed between propofol and the premedicants and other anaesthetic agents used.     

Electroencephalographic evaluation of gold wire implants inserted in acupuncture points in dogs with epileptic seizures

The purpose of this study was to evaluate both, clinically and with electroencephalographic (EEG) recordings, the effect of gold wire implants in acupuncture points in dogs with uncontrolled idiopathic epileptic seizures. Fifteen dogs with such diagnosis were enrolled in the study. A first EEG recording was performed in all dogs under anaesthesia with xylazine (1 mg/kg) and propofol (6 mg/kg) before the treatment protocol, and a second EEG was performed 15 weeks later. Relative frequency power, intrahemispheric coherence available through EEG, number of seizures and seizure severity were compared before and after treatment using a Wilcoxon signed-rank test. There were no significant statistical differences before and after treatment in relative power or in intrahemispheric coherence in the EEG recording. However, there was a significant mean difference in seizure frequency and seizure severity between control and treatment periods. After treatment, nine of the 15 dogs (60%) had at least a 50% reduction in seizures frequency during the 15 weeks established as follow-up of this treatment.     

Cardiovascular Effects of a Continuous Two-Hour Propofol Infusion in Dogs Comparison With Isoflurane Anesthesia

The cardiovascular effects during 2 hours of anesthesia with either a continuous propofol infusion or isoflurane were compared in the same six healthy dogs. Dogs were randomly assigned to be anesthetized with either propofol (5 mg/kg, IV administered over 30 seconds, immediately followed by a propofol infusion beginning at 0.4 mg/kg/min), or isoflurane (2.0% end-tidal concentration). The propofol infusion was adjusted to maintain a light plane of anesthesia. Dogs anesthetized with propofol had higher values for systemic arterial pressure due to higher systemic vascular resistance. Dogs anesthetized with isoflurane had higher values for heart rate and mean pulmonary artery pressure. Cardiac index was not different between the two groups. Apnea and cyanosis were observed during induction of anesthesia with propofol. At the end of anesthesia the mean time to extubation for dogs anesthetized with either propofol or isoflurane was 13.5 min and 12.7 min, respectively. A continuous infusion of propofol (0.44 mg/kg/min) provided a light plane of anesthesia. Ventilatory support during continuous propofol infusion is recommended.     

Medetomidine-ketamine anaesthesia induction followed by medetomidine-propofol in ponies: infusion rates and cardiopulmonary side effects

REASONS FOR PERFORMING STUDY: To search for long-term total i.v. anaesthesia techniques as a potential alternative to inhalation anaesthesia. OBJECTIVES: To determine cardiopulmonary effects and anaesthesia quality of medetomidine-ketamine anaesthesia induction followed by 4 h of medetomidine-propofol anaesthesia in 6 ponies. METHODS: Sedation consisted of 7 microg/kg bwt medetomidine i.v. followed after 10 min by 2 mg/kg bwt i.v. ketamine. Anaesthesia was maintained for 4 h with 3.5 microg/kg bwt/h medetomidine and propofol at minimum infusion dose rates determined by application of supramaximal electrical pain stimuli. Ventilation was spontaneous (F(I)O2 > 0.9). Cardiopulmonary measurements were always taken before electrical stimulation, 15 mins after anaesthesia induction and at 25 min intervals. RESULTS: Anaesthesia induction was excellent and movements after pain stimuli were subsequently gentle. Mean propofol infusion rates were 0.89-0.1 mg/kg bwt/min. No changes in cardiopulmonary variables occured over time. Range of mean values recorded was: respiratory rate 13.0-15.8 breaths/min; PaO2 29.1-37.9 kPa; PaCO2 6.2-6.9 kPa; heart rate 31.2-40.8 beats/min; mean arterial pressure 90.0-120.8 mmHg; cardiac index 44.1-59.8 ml/kg bwt/min; mean pulmonary arterial pressure 11.8-16.4 mmHg. Recovery to standing was an average of 31.1 mins and ponies stood within one or 2 attempts. CONCLUSIONS: In this paper, ketamine anaesthesia induction avoided the problems encountered previously with propofol. Cardiovascular function was remarkably stable. Hypoxaemia did not occur but, despite F(I)O2 of > 0.9, minimal PaO2 in one pony after 4 h anaesthesia was 8.5 kPa. POTENTIAL RELEVANCE: The described regime might offer a good, practicable alternative to inhalation anaesthesia and has potential for reducing the fatality rate in horses.     

A comparison of cardiorespiratory variables during isoflurane-fentanyl and propofol-fentanyl anaesthesia for surgery in injured cats

OBJECTIVE: To compare haemodynamic and respiratory variables during isoflurane-fentanyl (IF) and propofol-fentanyl (PF) anaesthesia for surgery in injured cats. STUDY DESIGN: Prospective, randomized, controlled clinical study. ANIMALS: Thirty-three client-owned injured cats undergoing orthopaedic surgery. MATERIALS AND METHODS: Pre-anaesthetic medication was intravenous midazolam 1 mg kg(-1), butorphanol 0.4 mg kg(-1) and ketamine 2 mg kg(-1). Anaesthesia was induced with propofol (P) and maintained with either: (a) a continuous rate infusion (CRI) of fentanyl (F) 0.02 mg kg(-1) hour(-1) and isoflurane (initial end-tidal concentration of 1%), (b) a fentanyl CRI (dose as before) and sevoflurane (initial end-tidal concentration of 2%) or (c) a CRI of propofol (12 mg kg(-1) hour(-1)). All three techniques were given to effect until surgical anaesthesia was achieved. Heart rate and rhythm (ECG), mean arterial blood pressure, respiratory rate, tidal volume and end-tidal CO(2) concentration were recorded. Venous blood gas analysis was performed before and after sedation, and at the end of anaesthesia. Blood chemistry and blood cell counts were assessed before, at the end of, and 24 hours after anaesthesia. The variables recorded from cats anaesthetized with IF and PF were compared. RESULTS: Mean end-expiratory isoflurane concentration was 1.19 +/- 0.19%. The propofol infusion rate was 11.4 +/- 0.8 mg kg(-1) hour(-1). No significant differences between the two groups in heart rate were identified; no cardiac dysrhythmias were recorded. Mean arterial blood pressure was significantly lower in IF cats during skin incision (p = 0.01), during surgery without intense surgical stimulation (p < 0.01) and during surgery with intense surgical stimulation (p = 0.01). Nine of 11 cats in the IF group were markedly hypotensive (34-49 mmHg) while seven of 11 cats in group PF were mildly hypotensive (49-59 mmHg). One of 11 cats in group IF and nine of 11 cats in group PF required intermittent positive pressure ventilation (IPPV) to maintain end-tidal CO(2) levels below 6.66 kPa (50 mmHg). CONCLUSION AND CLINICAL RELEVANCE: Despite the necessity to ventilate the lungs of cats in the PF group, arterial blood pressure was better maintained. Propofol-fentanyl anaesthesia is better for surgery in injured cats providing the means to impose IPPV are available.     

Evaluation of propofol containing 2% benzyl alcohol preservative in cats

Propofol emulsion containing benzyl alcohol preservative (BA) was evaluated in cats. Eight (PB) received 1% propofol containing 2% benzyl alcohol and eight (PC) preservative-free propofol. In phase 1, cats were anaesthetised (8 mg/kg) three times at 48 h intervals. In phase 2, cats underwent three anaesthetic procedures at 48 h intervals where anaesthesia was maintained until 24 mg/kg had been administered. Clinical examination and haematological and biochemical analyses were performed regularly. Cardiorespiratory function was monitored throughout anaesthesia. Neurological examination was performed daily for 7 days after phase 2. All cats were euthanased 7 days after phase 2 and examined post mortem to determine any organ toxicity and to comply with regulatory requirements. Anaesthesia was as expected for propofol in cats and no clinically relevant differences between PB and PC were detected. The addition of BA has no additional effect when propofol is used at normal-to-high clinical doses in healthy cats.     

Clinical evaluation of a new formulation of propofol in a medium-chain and long-chain triglycerides emulsion in dogs

Propofol formulated in a mixed medium-chain and long-chain triglycerides emulsion has been recently introduced for clinical use as an alternative to the conventional long-chain triglycerides formulation. This prospective multicentric study evaluated the clinical effectiveness and the complications associated with the use of this new formulation of propofol in dogs. Forty-six Spanish veterinary clinics participated in this study. A total of 541 anaesthesias (118 ASA I, 290 ASA II, 101 ASA III and 32 ASA IV) performed for various diagnostic and therapeutic purposes were evaluated. The anaesthetic protocol was not controlled, with the exception that propofol had to be used at least for induction of anaesthesia. The induction dose of propofol and the incidence of anaesthetic complications throughout the procedure were recorded. A chi-square test compared the incidence of complications according to the maintenance agent used (propofol vs. inhalatory anaesthesia), anaesthetic risk (ASA classification) and the reason for the anaesthesia. The patients premedicated with alpha2 agonists needed lower doses (mean +/- SD, 2.9 +/- 1.3 mg/kg i.v.) than the animals premedicated with phenothiazines (3.9 +/- 1.4 mg/kg i.v.) or benzodiazepines (4.0 +/- 1.4 mg/kg i.v.). The most frequent complications were difficult endotracheal intubation (1.3%), postinduction apnoea (11.3%), cyanosis (0.6%), bradypnoea (2.6%), tachypnoea (2.8%), bradycardia (2%), tachycardia (2.6%), hypotension (0.2%), shock (0.2%), vomiting (4.6%), epileptiform seizures (2.8%), premature awakening (7.4%) and delayed recovery (0.9%). There were no cases of pain on injection or aspiration pneumonia. Three dogs died (0.55%), one during induction and two during recovery from anaesthesia. This study demonstrates that the new formulation of propofol is an useful and effective drug to induce general anaesthesia in dogs.     

Propofol-halothane-nitrous oxide/oxygen anaesthesia for mega-voltage radiotherapy in dogs

Observations were made on 49 dogs aged 3–13 years, of ASA Grades I and 11, during 83 periods of mega-voltage radiotherapy. The dogs weighed 5.847.0 kg and the total duration of anaesthesia ranged from 12–52 min (mean ± sem, 22 ± 8). No premedication was given. Anaesthesia was induced with iv propofol and, following endotracheal intubation, maintained with halothane/nitrous oxide/oxygen and intermittent injections of propofol. The dose of propofol needed to induce jaw relaxation sufficient for intubation was 3.5–10.8 mgkg bwt (5.67 ± 0.15) administered over 7–137 s (36 ± 2). On 91 occasions in 54 periods of anaesthesia, supplementary doses of propofol ranging from 0.2–4.9 mg/kg bwt (1.42 ± 0.14) were needed during positioning for irradiation. The times elapsing from extubation to swallowing, response to voice, spontaneous head lifting and walking were 3, 6, 7 and 13 min, respectively. A 12% incidence of tonic-clonic movements indicated that the method of anaesthesia cannot be regarded as entirely satisfactory for mega-voltage radiotherapy.     

Case Series: Continuous electroencephalographic monitoring of status epilepticus in dogs and cats: 10 patients (2004–2005)

Objective – To describe the use of continuous electroencephalographic (EEG) monitoring for management of status epilepticus (SE) in dogs and cats. Design – Retrospective study. Setting – University teaching hospital. Animals – Ten patients (7 dogs, 3 cats) with SE of differing etiology (idiopathic epilepsy, n=3; toxicity, n=4; meningoencephalitis, n=2; undefined, n=1). Interventions – The EEG was recorded continuously from 5 stainless‐steel needle electrodes inserted SC. Animals were treated with diazepam and phenobarbital followed by either propofol (n=3) or pentobarbital (n=7) as a continuous rate of infusion. Measurements and Main Results – Clinical seizures stopped after induction of anesthesia in each animal. The EEG, however, still showed distinct epileptiform patterns (spikes, polyspikes) in all animals. Paroxysms were suppressed by increasing the infusion rate of either pentobarbital or propofol. A burst‐suppression pattern was achieved in 5 animals. EEG epileptiform activity reappeared in 4 animals when attempting to taper the dose after >6 hours of anesthesia. This was interpreted as ongoing EEG seizure activity and an increased risk for clinical seizures, and the anesthetic dosage was adjusted accordingly. Conclusion – Continuous EEG monitoring appears to be a useful tool for therapeutic monitoring of SE in dogs and cats. It allows the detection of EEG seizures without the appearance of clinical seizures. Further investigations with blinded investigators and homogeneous animal groups to define therapeutic endpoints are warranted.     

The effects of halothane and nitrous oxide on the pharmacokinetics of propofol in dogs

The pharmacokinetics of propofol, 6.5 mg/kg, administered as a bolus dose intravenously (i.v.) were studied in six dogs (group 1). The effect of maintaining anaesthesia with halothane and nitrous oxide in oxygen on propofol pharmacokinetics was also investigated in six dogs undergoing routine anaesthesia (group 2). Induction of anaesthesia was rapid in all animals. Post-induction apnoea was a feature in three of the 12 dogs. The blood propofol concentration-time profile was best described by a bi-exponential decline in two dogs in group 1 and in 3 dogs in group 2, and by a tri-exponential decline in four dogs in group 1 and 3 dogs in group 2. The elimination half-life was long in both groups (90.9 min and 75.2 min, respectively), the volume of distribution at steady state large (4889 and 4863 ml/kg) and the clearance rapid (58.6 and 56.3 ml/kg.min). There were no significant differences between the groups, thus indicating that maintenance of anaesthesia with halothane and nitrous oxide had no effect on the pharmacokinetics of propofol in the dog.     

Effect of variable-dose propofol alone and in combination with two fixed doses of ketamine for total intravenous anesthesia in cats

OBJECTIVE: To determine the minimum infusion rate (MIR50) for propofol alone and in combination with ketamine required to attenuate reflexes commonly used in the assessment of anesthetic depth in cats. ANIMALS: 6 cats. PROCEDURE: Propofol infusion started at 0.05 to 0.1 mg/kg/min for propofol alone or 0.025 mg/kg/min for propofol and ketamine (low-dose ILD] constant rate infusion [CRI] of 23 microg/kg/min or high-dose [HD] CRI of 46 microg/kg/min), and after 15 minutes, responses of different reflexes were tested. Following a response, the propofol dose was increased by 0.05 mg/kg/min for propofol alone or 0.025 mg/kg/min for propofol and ketamine, and after 15 minutes, reflexes were retested. RESULTS: The MIR50 for propofol alone required to attenuate blinking in response to touching the medial canthus or eyelashes; swallowing in response to placement of a finger or laryngoscope in the pharynx; and to toe pinch, tetanus, and tail-clamp stimuli were determined. Addition of LD ketamine to propofol significantly decreased MIR50, compared with propofol alone, for medial canthus, eyelash, finger, toe pinch, and tetanus stimuli but did not change those for laryngoscope or tail-clamp stimuli. Addition of HD ketamine to propofol significantly decreased MIR50, compared with propofol alone, for medial canthus, eyelash, toe pinch, tetanus, and tail-clamp stimuli but did not change finger or laryngoscope responses. CONCLUSIONS AND CLINICAL RELEVANCE: Propofol alone or combined with ketamine may be used for total IV anesthesia in healthy cats at the infusion rates determined in this study for attenuation of specific reflex activity.     

Clinical use of dexmedetomidine as premedicant in cats undergoing propofol-sevoflurane anaesthesia

The purpose of this report was to evaluate the cardiorespiratory effects and efficacy of dexmedetomidine as a premedicant agent in cats undergoing ovariohysterectomy anaesthetized with propofol-sevoflurane. Cats were randomly divided into two groups of eight animals each. Dexmedetomidine (0.01 mg/kg) or 0.9% saline was administered intravenously (D and S, respectively). After 5 min, propofol was administered intravenously and anaesthesia was maintained with sevoflurane. Heart and respiratory rates, arterial blood pressure, oxygen saturation, rectal temperature and the amount of propofol needed for induction were measured. Premedication with dexmedetomidine reduced the requirement of propofol (6.7+/-3.8 mg/kg), but induced bradycardia, compared with the administration of saline (15.1+/-5.1 mg/kg). Recovery quality was significantly better in D but no significant difference in time to return of swallowing reflex was observed between groups (D=2.5+/-0.5 min; S=3.2+/-1.8 min). In conclusion, dexmedetomidine is a safe and effective agent for premedication in cats undergoing propofol-sevoflurane anaesthesia with minimal adverse effects.