Effect of sodium bicarbonate infusions on ionized calcium and total calcium concentrations in serum of clinically normal cats

The effects of sodium bicarbonate (0.5 mEq/kg of body weight, 1.0 mEq/kg, 2.0 mEq/kg, and 4.0 mEq/kg) on ionized and total calcium concentrations were determined in clinically normal cats. Also, serum pH, whole blood pH, and serum albumin, serum total protein, and serum phosphorus concentrations were measured. Intravenous administration of sodium bicarbonate to awake cats decreased serum ionized calcium and serum total calcium concentrations. All dosages of sodium bicarbonate were associated with significant decreases of serum ionized calcium concentration. This effect lasted for greater than 180 minutes when cats were given 2.0 mEq/kg or 4.0 mEq/kg. When cats were given 4 mEq of sodium bicarbonate/kg, serum ionized calcium concentration was significantly decreased, compared with that when cats were given lower doses, but only at 10 minutes after infusion. After sodium bicarbonate infusion, serum total calcium concentration, measured by ion-specific electrode and colorimetry, was lower than baseline values at most of the times evaluated. Decreases in serum ionized calcium and serum total calcium concentrations can be attributed only in part to an increase in serum or whole blood pH and to a decrease in serum protein concentration. Serum total calcium concentrations measured by ion-specific electrode and by colorimetry were positively correlated, but the variability was high. Only 44% of the variability in serum ionized calcium concentration could be predicted when serum total calcium, albumin, total protein, phosphorus, and bicarbonate concentrations and pH were considered.     

Acute effects of intravenous dronedarone on electrocardiograms,hemodynamics and cardiac functions in anesthetized dogs

Dronedarone is a class III antiarrhythmic that has been used for management of atrial fibrillation in humans, but limited information was found in dogs. The objective of this study was to determine the acute effects of escalating concentrations of dronedarone on electrocardiograms (ECG), hemodynamics and cardiac mechanics in healthy dogs. A total of 7 beagle dogs were anesthetized with isoflurane and instrumented to obtain lead II ECG, pressures at ascending aorta, right atrium, pulmonary artery and left ventricle, and left ventricular pressure-volume relationship. Five dogs were given vehicle and followed by escalating doses of dronedarone (0.5, 1.0 and 2.5 mg/kg, 15 min for each dose), and two dogs were used as a vehicle-treated control. All parameters were measured at 15 min after the end of each dose. The results showed that all parameters in vehicle-treated dogs were unaltered. Dronedarone at 2.5 mg/kg significantly lengthened PQ interval (P<0.01), reduced cardiac output (P<0.01) and increased systemic vascular resistance (P<0.01). Dronedarone produced negative inotropy assessed by significantly lowered end-systolic pressure-volume relationship, preload recruitable stroke work, contractility index and dP/dt_max. It also impaired diastolic function by significantly increased end-diastolic pressure-volume relationship, tau and dP/dt_min. These results suggested that acute effects of dronedarone produced negative dromotropy, inotropy and lusitropy in anesthetized dogs. Care should be taken when given dronedarone to dogs, especially when the patients have impaired cardiac function.     

The effects of surgery and anesthesia on blood magnesium and calcium concentrations in canine and feline patients

OBJECTIVE: To demonstrate the effect of anesthesia and surgery on serum ionized magnesium and ionized calcium concentrations in clinical canine and feline patients. ANIMALS: 37 client-owned dogs, ASA PS I-III and 10 client-owned cats, ASA PS I, all receiving anesthesia for elective or emergent surgery at a Veterinary Teaching Hospital. MATERIALS AND METHODS: Plasma ionized and serum total magnesium, and plasma ionized calcium were measured prior to and after a group-standardized anesthetic protocol. RESULTS: Regardless of pre-operative medication (hydromorphone or butorphanol), anesthetic induction (thiopental or lidocaine/hydromorphone/diazepam (LHD) and propofol combination), or type of surgical procedure (peripheral surgery or laparotomy), post-operative plasma ionized calcium concentration decreased in all groups of dogs, while post-operative plasma ionized magnesium increased in all groups, although the changes were not always significant. The dogs who were induced with an LHD and propofol technique had a greater increase in ionized magnesium (0.36 +/- 0.07 to 0.42 +/- 0.07 mmol L(-1)) than the group in which anesthesia was induced with thiopental (0.41 +/- 0.07 to 0.42 +/- 0.07 mmol L(-1), p = 0.009). The cats showed similar changes in ionized magnesium and ionized calcium, and also had a significant increase in serum total magnesium (2.17 +/- 0.20 to 2.31 +/- 0.25 mg dL(-1), p = 0.009) CONCLUSIONS, CLINICAL RELEVANCE: A post-operative decrease in ionized calcium was demonstrated in healthy animals, as well as an increase in ionized or total magnesium after various anesthetic protocols and surgeries. These changes, while statistically significant, do not appear to be clinically significant, as values remained within reference ranges at all times.     

Effects of slow infusion of a low dosage of endotoxin on systemic haemodynamics in conscious horses

The effects of intravenous (iv) infusion of endotoxin for 60 mins at a cumulative dosage of 0.03 micrograms/kg bodyweight on systemic arterial, right atrial and pulmonary arterial pressures, heart rate, cardiac output, and derived pulmonary vascular resistance and total peripheral vascular resistance were compared to the effects of iv infusion of saline solution in four healthy horses. Heart rate was increased significantly after endotoxin infusion, although diastolic arterial pressure, systolic arterial pressure, electronically averaged arterial pressure, cardiac output, total peripheral resistance, and right atrial pressure did not change significantly. Average pulmonary arterial pressure was increased significantly by endotoxin infusion. This was accompanied by a trend toward increased diastolic pulmonary arterial pressure (P = 0.1), systolic pulmonary arterial pressure (P = 0.08) and pulmonary vascular resistance (P = 0.07). These results suggest that low dosages of endotoxin produce pulmonary hypertension without causing hypotensive, hypodynamic shock.     

Secondary hypoparathyroidism attributed to hypomagnesemia in a dog with protein-losing enteropathy.

Severe hypomagnesemia (0.8 mg/dl; reference range, 1.6 to 2.3 mg/dl), hypocalcemia, and protein-losing enteropathy were identified in a 5-year-old castrated male 3-kg (6.6 lb) Shih Tzu examined because of anorexia, lethargy, paresis, and abdominal distention. Histologic examination of intestinal biopsy specimens revealed lymphangiectasia and lymphocytic, plasmacytic, neutrophilic infiltrates. Initial treatment included administration of magnesium (0.80 mEq/kg [0.36 mEq/lb]) of body weight in a balanced electrolyte solution. This treatment resulted in normalization of the serum magnesium concentration (1.7 mg/dl); resolution of the lethargy, paresis, and tachycardia; and an increase in the serum parathyroid hormone and ionized calcium concentrations. Findings were consistent with secondary hypoparathyroidism attributable to hypomagnesemia. Magnesium concentration should be monitored in all dogs with gastrointestinal tract disease, especially those with protein-losing enteropathy, anorexia, and weakness.     

Efficacy of milbemycin oxime against naturally acquired or experimentally induced Ancylostoma spp and Trichuris vulpis infections in dogs.

The efficacy of milbemycin oxime was evaluated at dosages of 0.25, 0.50, and 0.75 mg/kg of body weight in dogs naturally infected with mature Ancylostoma spp, at a dosage of 0.50 mg/kg in dogs with experimentally induced immature and mature A caninum, and at dosages of 0.55 to 0.86 mg/kg in dogs naturally infected with mature Trichuris vulpis. Milbemycin oxime was 95 and 99% effective against mature Ancylostoma spp at dosages of 0.50 and 0.75 mg/kg, respectively, but only 49% effective at a dosage of 0.25 mg/kg. Efficacy was 49% against pulmonary L3-L4 stages of A caninum (36 hours after inoculation), greater than 80% against L4 (120 hours after inoculation) and early L5 stages (216 hours after inoculation), and greater than 90% against experimentally induced mature stages (360 hours after inoculation). Milbemycin oxime was also 97% effective in the removal of mature Tr vulpis from naturally infected dogs. Adverse reactions were not observed following treatment in any of the dogs.     

Effects of dopamine administration on cecal mechanical activity and cecal blood flow in conscious healthy horses

Lateral cecal arterial blood flow, carotid arterial pressure, heart rate, and mechanical activity of the circular and longitudinal muscle layers of the cecal body were measured in 7 conscious healthy horses during IV infusion of physiologic saline solution for 60 minutes (control), during a 60-minute IV infusion of dopamine (at dosages of 1, 2.5, and 5 micrograms/kg/min), and for 60 minutes after IV infusion of dopamine. The mean values for lateral cecal arterial blood flow during IV infusion of dopamine at a dosage of either 1 or 2.5 micrograms/kg/min were not significantly different from the mean values for lateral cecal arterial blood flow during IV infusion of saline solution. The mean values for lateral cecal arterial blood flow, however, were significantly greater during IV infusion of dopamine at a dosage of 5 micrograms/kg/min than the mean values for lateral cecal arterial blood flow during IV infusion of saline solution. Intravenous infusion of dopamine at 1 and 2.5 micrograms/kg/min did not significantly change the mean values for carotid arterial pressure. In contrast, the mean values for carotid arterial pressure were significantly less during IV infusion of dopamine at dosages of 2.5 and 5 micrograms/kg/min than during infusion of saline solution. The mean values for heart rate were not significantly altered by infusion of dopamine at a dosage of either 1 or 2.5 micrograms/kg/min, but infusion of dopamine at a dosage of 5 micrograms/kg/min significantly increased heart rate.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of an anaesthetic technique used in dogs undergoing craniectomy for tumour resection

ObjeCTIVE: To evaluate a total intravenous anaesthetic technique in dogs undergoing craniectomy. STUDY DESIGN: Prospective clinical study. ANIMALS: Ten dogs admitted for elective surgical resection of rostro-tentorial tumours. METHODS: All dogs were premedicated with methadone, 0.2 mg kg(-1) intramuscularly 30 minutes prior to induction of anaesthesia. Anaesthesia was induced with propofol administered intravenously (IV) to effect, following administration of lidocaine 1 mg kg(-1) IV and maintained with a continuous infusion of propofol at < or =0.4 mg kg(-1) minute(-1) during instrumentation and preparation and during movement of the animals to recovery. During surgery, anaesthesia was maintained using a continuous infusion of propofol at 相似文献   

Effect of marbofloxacin on cardiovascular variables in healthy isoflurane-anesthetized dogs

OBJECTIVE: To study the hemodynamic effects of marbofloxacin (MBF) in isoflurane-anesthetized dogs. ANIMALS: 6 healthy 8-month-old Beagles. PROCEDURE: Anesthesia was induced with sodium thiopental and maintained with isoflurane. Cardiovascular variables were monitored throughout anesthesia. Marbofloxacin was administered by an IV bolus at 2 mg/kg, followed 10 minutes later by an infusion at a rate of 40 mg/kg/h for 30 minutes (total dose, 20 mg/kg). Plasma MBF concentrations were measured by high-performance liquid chromatography. RESULTS: The mean peak concentration during MBF infusion was 34.2 +/- 6.4 microg/mL. The IV administration of the MBF bolus did not alter any cardiovascular variable in isoflurane-anesthetized dogs. Significant changes were found during infusion when a cumulative dose of 12 mg/kg had been given. The maximal decreases observed at the end of the infusion were 16% in heart rate, 26% in systolic left ventricular pressure, 33% in systolic aortic pressure, 38% in diastolic aortic pressure, 29% in cardiac output, and 12% in QT interval. All dogs recovered rapidly from anesthesia at the end of the experiment. CONCLUSIONS AND CLINICAL RELEVANCE: MBF may safely be used at 2 mg/kg IV in isoflurane-anesthetized dogs, and significant adverse cardiovascular effects are found only when 6 to 8 times the recommended dose is given.     

Effect of sustained release isosorbide dinitrate (EV151) in dogs with experimentally-induced mitral insufficiency

To investigate the hemodynamic effects on seven anesthetized dogs with experimentally-induced mitral insufficiency, isosorbide dinitrate (ISDN) in sustained release form (EV151) was administered at different dosages (0, 2, 8 and 16 mg/kg). The drug administration resulted in altered pulmonary arterial wedge pressure (preload), and cardiac output and total systemic resistance (afterload). Arterial pressure increased in the control group and in animals receiving 2 mg/kg, but decreased in animals 1-2 hr after receiving 8 and 16 mg/kg dosages. Cardiac output increased in animals receiving 2, 8 and 16 mg/kg dosages, with concomitant decreases in total systemic resistance. ISDN caused mild vasodilation at 2 mg/kg and severe vasodilation at 8 and 16 mg/kg. Future experiments on non-anesthetized dogs may be of benefit.     

Alterations in epinephrine-induced arrhythmogenesis after xylazine and subsequent yohimbine administration in isoflurane-anesthetized dogs

Effects of xylazine (1.1 mg/kg of body weight, IV bolus, plus 1.1 mg/kg/h infusion) and subsequent yohimbine (0.125 mg/kg, IV bolus) administration on the arrhythmogenic dose of epinephrine (ADE) in isoflurane (1.8% end-tidal)-anesthetized dogs were evaluated. The ADE was defined as the total dose of epinephrine that induced greater than or equal to 4 premature ventricular contractions within 15 seconds during a 3-minute infusion period or within 1 minute after the end of infusion. Total ADE values during isoflurane anesthesia, after xylazine administration, and after yohimbine injection were 36.6 +/- 8.45 micrograms/kg, 24.1 +/- 6.10 micrograms/kg, and 45.7 +/- 6.19 micrograms/kg, respectively. Intravenous xylazine administration significantly (P less than 0.05) increased blood pressure and decreased heart rate, whereas yohimbine administration induced a significant (P less than 0.05) decrease in blood pressure. induced a significant (P less than 0.05) decrease in blood pressure. After yohimbine administration, the ADE significantly (P less than 0.05) increased above that after isoflurane plus xylazine administration. After yohimbine administration, blood pressure measured immediately before epinephrine-induced arrhythmia was significantly (P less than 0.05) less than the value recorded during isoflurane plus xylazine anesthesia. Heart rate was unchanged among treatments immediately before epinephrine-induced arrhythmia. Seemingly, yohimbine possessed a protective action against catecholamine-induced arrhythmias in dogs anesthetized with isoflurane and xylazine.     

Comparison of the cardiopulmonary effects of etomidate and thiamylal in dogs.

The cardiopulmonary effects of etomidate, a nonbarbiturate, short-acting, IV anesthetic, were compared and contrasted with those of thiamylal sodium in chronically instrumented conscious dogs. Etomidate, when administered IV at dosages of 1.5 and 3.0 mg/kg of body weight, produced anesthesia lasting from 8 +/- 5 and 21 +/- 9 minutes, respectively. Heart rate, aortic blood pressure, left ventricular peak pressure, left ventricular end diastolic pressure, left ventricular contractile force, and myocardial oxygen consumption were unchanged after administration of either dose of etomidate; however, the dosage of 1.5 mg/kg produced significant (P less than 0.05) increases in respiratory rate and decreases in tidal volume. The minute volume remained unchanged from base-line values. Significant (P less than 0.05) decreases in tidal volume, arterial pH, and partial pressure of oxygen were produced, and minute volume remained unchanged when 3.0 mg of etomidate/kg of body weight was administered. Thiamylal sodium (8.0 mg/kg of body weight; given IV) produced anesthesia lasting for 14 +/- 5 minutes. Significant increases (P less than 0.05) in heart rate, arterial blood pressure, left ventricular peak pressure, and myocardial oxygen consumption were observed after IV administration. Left ventricular contractility was significantly (P less than 0.05) decreased. Respiratory rate was not significantly (P less than 0.05) affected by thiamylal although tidal volume and minute volume were decreased. These respiratory alterations resulted in significant (P less than 0.05) increases in the arterial partial pressure of carbon dioxide and decreases in pH and the partial pressure of oxygen. On the basis of cardiopulmonary function, etomidate offered rapid, safe, short duration anesthesia superior to that of thiamylal sodium.     

Doxapram: cardiopulmonary effects in the horse

The cardiopulmonary effects of 3 dosages of doxapram hydrochloride (0.275 mg/kg, 0.55 mg/kg, and 1.1 mg/kg, IV) were studied in 6 adult horses. Doxapram given IV significantly (P less than 0.05) decreased PaCO2 and increased respiratory rate, cardiac output arterial blood pressures (systolic, mean, and diastolic) arterial pH, and PaO2 at 1 minute after each dose was administered. Heart rate and mean and diastolic pulmonary arterial blood pressure were significantly (P less than 0.05) increased 1 minute after the 2 larger dosages of doxapram were given (0.55 mg/kg and 1.1 mg/kg, IV), but not after the smallest dosage was given. All measurements, except heart rate and cardiac output, had returned to base line by 5 minutes after each dosing. Heart rate remained significantly (P less than 0.05) increased 10 minutes after the 0.55 mg/kg dosage was given and 30 minutes after the 1.1 mg/kg dosage. Cardiac output remained significantly (P less than 0.05) increased at 10 minutes, 5 minutes, and 30 minutes after the 0.275, 0.55, and 1.1 mg/kg dosages, respectively, were given.     

Preclinical evaluation of a liposome-encapsulated formulation of cisplatin in clinically normal dogs

OBJECTIVE: To determine the acute and short-term adverse effects of a liposome-encapsulated form of cisplatin at increasing dosages of up to twice the known maximally tolerated dose (MTD) of unencapsulated cisplatin in clinically normal dogs. ANIMALS: 4 healthy 2.5-year-old sexually intact female hound-type dogs. PROCEDURE: 4 dosages (70, 100, 125, and 150 mg/m2) were evaluated, and the 4 dogs received a total of 9 infusions (1 to 3 infusions/dog). Dogs were monitored to detect changes in clinical and clinicopathologic status. Evaluations consisting of a physical examination, CBC, serum biochemical analysis, and urinalysis were performed before and 7 and 21 days after each infusion. RESULTS: Acute anaphylactic-like reactions to liposome-encapsulated cisplatin were common but clinically manageable. Nephrotoxicosis and substantial myelosuppression, toxic effects commonly associated with unencapsulated cisplatin, were not observed in dogs treated with liposome-encapsulated cisplatin at dosages equivalent to twice the known MTD of unencapsulated cisplatin. CONCLUSIONS AND CLINICAL RELEVANCE: Liposome-encapsulated cisplatin can be safely administered to clinically normal dogs at dosages of up to 150 mg/m2 without the need for concurrent hydration protocols. This was a necessary prerequisite to enable phase I clinical trials in dogs with naturally developing cancers that could theoretically benefit from escalation in the dosage of cisplatin. Determination of an MTD, cumulative and long-term toxic effects, and efficacy can now be conducted in the context of phase I trials in tumor-bearing dogs.     

Acute cardiovascular effects of diltiazem in anesthetized dogs with induced atrial fibrillation

Atrial fibrillation (AF) is one of the most important arrhythmias of dogs. In a previous study, we determined the dosage of intravenously administered diltiazem necessary to reduce ventricular response (VR), cardiac output (CO), and mean systemic arterial pressure (P(Ao)) to values similar to those observed during sinus rhythm (SR) before induction of AF. The present study was conducted to establish an acute, effective dosage of diltiazem given PO. AF was produced by rapid atrial pacing in healthy, anesthetized Beagle Hounds. Dogs were instrumented to record hemodynamic and electrophysiological parameters. Four dogs were given 2.5 mg/kg diltiazem, and another 4 dogs were given 5 mg/kg diltiazem by stomach tube, whereas 4 other dogs received vehicle in equivalent volumes. Plasma concentrations of diltiazem were measured at various intervals after dosing. A dosage of 5 mg/kg diltiazem produced plasma concentrations of 32-100 ng/mL 3 hours after administration, concentrations within the published effective range for dogs with naturally occurring AF. Between 2 and 3 hours after this dosage, the rate pressure product (RPP) and an index of left ventricular efficiency returned to values similar to those observed during SR. Thus, we believe that diltiazem at anorally administered dosages of 5 mg/kg should be considered to produce therapeutic blood concentrations and favorable hemodynamic effects in dogs with naturally occurring AF. These data must be extrapolated with caution to dogs with long-standing AF produced by natural causes.     

Pharmacokinetic disposition of dimethyl sulfoxide administered intravenously to horses

Dimethyl sulfoxide (DMSO) was administered IV to 6 Thoroughbred horses at 2 dosages: 1.0 g/kg and 0.1 g/kg. The pharmacokinetics seemed linear, with biological half-lives of 8.6 +/- 0.3 hours and 9.8 +/- 2.2 hours for the 1.0 g/kg and 0.1 g/kg dosages, respectively. This was further substantiated by mean residence times of 9.8 +/- 0.44 hours and 13.8 +/- 4.25 hours, areas under the curve of 12.55 +/- 1.42 mg/ml/hr and 1.63 +/- 0.49 mg/ml/hr, and the clearances of 0.081 +/- 0.009 L/kg/hr and 0.066 +/- 0.022 L/kg/hr for the large and small dosages, respectively. At 12 hours after 1.0 g/kg was administered, 26.6% of the DMSO dose was excreted unchanged into the urine; at 12 hours after 0.1 g/kg was administered, 25.3% of the DMSO dose was excreted unchanged into the urine. It was predicted that 29.4% and 40.6% of the total DMSO dose would be excreted into the urine for the 1.0 g/kg and 0.1 g/kg dosages, respectively. A 10% DMSO concentration in normal saline solution was safe to give as rapid IV infusion. Slow administration is recommended for more concentrated solutions. Based on the half-life, DMSO should be administered 2 times a day IV for the treatment of increased intracranial pressure and/or cerebral edema in horses.     

Excess rumen product anions in cattle. II. Toxic and lethal effects with butyrate.

Toxicity to butyrate was observed in 100-250 kg male Holstein calves following intravenous injection of 0.7-3.6 mmole/kg body weight, intravenous infusion with 0.12-0.53 mmole/min/kg body weight and intraruminal dosage with 19.4 mmole/kg body weight butyrate. Lower doses produced ataxia and serous nasal discharge. Higher doses produced sudden flaccid paralysis and death from asphyxia. No postmortem lesions, gross or histological, were observed. Plasma K+ was reduced to 2.2-2.5 mEq/L. When infusions were stopped, rapid recovery preceded clearance of butyrate and low K+ remained. Nerve depolarization in the central nervous system may be the cause of the toxic effects. Butyrate acidosis is suggested as a factor in unexplained sudden deaths in ruminants.     

Plasma calcium, inorganic phosphate and magnesium during hypocalcaemia induced by a standardized EDTA infusion in cows

The intravenous Na2EDTA infusion technique allows effective specific chelation of circulating Ca2+ leading to a progressive hypocalcaemia. Methods previously used were not described in detail and results obtained by monitoring total and free ionic calcium were not comparable due to differences in sampling and analysis. This paper describes a standardized EDTA infusion technique that allowed comparison of the response of calcium, phosphorus and magnesium between 2 groups of experimental cows. The concentration of the Na2EDTA solution was 0.134 mol/l and the flow rate was standardized at 1.2 ml/kg per hour. Involuntary recumbency occurred when ionised calcium dropped to 0.39-0.52 mmol/l due to chelation. An initial fast drop of ionized calcium was observed during the first 20 min of infusion followed by a fluctuation leading to a further drop until recumbency. Pre-infusion [Ca2+] between tests does not correlate with the amount of EDTA required to induce involuntary recumbence. Total calcium concentration measured by atomic absorption remained almost constant during the first 100 min of infusion but declined gradually when the infusion was prolonged. The concentration of inorganic phosphate declined gradually in a fluctuating manner until recumbency. Magnesium concentration remained constant during infusion. Such electrolyte responses during infusion were comparable to those in spontaneous milk fever. The standardized infusion technique might be useful in future experimental studies.     

Total intravenous anesthesia in greyhounds: pharmacokinetics of propofol and fentanyl--a preliminary study

OBJECTIVE: To evaluate concomitant propofol and fentanyl infusions as an anesthetic regime, in Greyhounds. ANIMALS: Eight clinically normal Greyhounds (four male, four female) weighing 25.58 +/- 3.38 kg. DESIGN: Prospective experimental study. METHODS: Dogs were premedicated with acepromazine (0.05 mg/kg) by intramuscular (i.m.) injection. Forty five minutes later anesthesia was induced with a bolus of propofol (4 mg/kg) by intravenous (i.v.) injection and a propofol infusion was begun (time = 0). Five minutes after induction of anesthesia, fentanyl (2 microg/kg) and atropine (40 microg/kg) were administered i.v. and a fentanyl infusion begun. Propofol infusion (0.2 to 0.4 mg/kg/min) lasted for 90 minutes and fentanyl infusion (0.1 to 0.5 microg/kg/min) for 70 minutes. Heart rate, blood pressure, respiratory rate, end-tidal carbon dioxide, body temperature, and depth of anesthesia were recorded. The quality of anesthesia, times to return of spontaneous ventilation, extubation, head lift, and standing were also recorded. Blood samples were collected for propofol and fentanyl analysis at varying times before, during and after anesthesia. RESULTS: Mean heart rate of all dogs varied from 52 to 140 beats/min during the infusion. During the same time period, mean blood pressure ranged from 69 to 100 mm Hg. On clinical assessment, all dogs appeared to be in light surgical anesthesia. Mean times (+/- SEM), after termination of the propofol infusion, to return of spontaneous ventilation, extubation, head lift and standing for all dogs were 26 +/- 7, 30 +/- 7, 59 +/- 12, and 105 +/- 13 minutes, respectively. Five out of eight dogs either whined or paddled their forelimbs in recovery. Whole blood concentration of propofol for all eight dogs ranged from 1.21 to 6.77 microg/mL during the infusion period. Mean residence time (MRTinf) for propofol was 104.7 +/- 6.0 minutes, mean body clearance (Clb) was 53.35 +/- 0.005 mL/kg/min, and volume of distribution at steady state (Vdss) was 3.27 +/- 0.49 L/kg. Plasma concentration of fentanyl for seven dogs during the infusion varied from 1.22 to 4.54 ng/mL. Spontaneous ventilation returned when plasma fentanyl levels were >0.77 and <1.17 ng/mL. MRTinf for fentanyl was 111.3 +/- 5.7 minutes. Mean body clearance was 29.1 +/- 2.2 mL/kg/min and Vdss was 2.21 +/- 0.19 L/kg. CONCLUSION AND CLINICAL RELEVANCE: In Greyhounds which were not undergoing any surgical stimulation, total intravenous anesthesia maintained with propofol and fentanyl infusions induced satisfactory anesthesia, provided atropine was given to counteract bradycardia. Despite some unsatisfactory recoveries the technique is worth investigating further for clinical cases, in this breed and in mixed breed dogs.     

Effects of acepromazine on the cardiovascular actions of dopamine in anesthetized dogs

OBJECTIVE: To evaluate the effects of acepromazine maleate on the cardiovascular changes induced by dopamine in isoflurane-anesthetized dogs. STUDY DESIGN: Prospective, randomized cross-over experimental design. ANIMALS: Six healthy adult spayed female dogs weighing 16.4 +/- 3.5 kg (mean +/- SD). METHODS: Each dog received two treatments, at least 1 week apart. Acepromazine (0.03 mg kg(-1), IV) was administered 15 minutes before anesthesia was induced with propofol (7 mg kg(-1), IV) and maintained with isoflurane (1.8% end-tidal). Acepromazine was not administered in the control treatment. Baseline cardiopulmonary parameters were measured 90 minutes after induction. Thereafter, dopamine was administered intravenously at 5, 10, and 15 microg kg(-1) minute(-1), with each infusion rate lasting 30 minutes. Cardiopulmonary data were obtained at the end of each infusion rate. RESULTS: Dopamine induced dose-related increases in cardiac index (CI), stroke index, arterial blood pressure, mean pulmonary arterial pressure, oxygen delivery index (DO(2)I) and oxygen consumption index. In the control treatment, systemic vascular resistance index (SVRI) decreased during administration of 5 and 10 microg kg(-1) minute(-1) of dopamine and returned to baseline with the highest dose (15 microg kg (-1) minute(-1)). After acepromazine treatment, SVRI decreased from baseline during dopamine administration, regardless of the infusion rate, and this resulted in a smaller increase in blood pressure at 15 microg kg (-1) minute(-1). During dopamine infusion hemoglobin concentrations were lower following acepromazine and this contributed to significantly lower arterial O(2) content. CONCLUSIONS: Acepromazine prevented the return in SVRI to baseline and reduced the magnitude of the increase in arterial pressure induced by higher doses of dopamine. However, reduced SRVI associated with lower doses of dopamine and the ability of dopamine to increase CI and DO(2)I were not modified by acepromazine premedication. CLINICAL RELEVANCE: Previous acepromazine administration reduces the efficacy of dopamine as a vasopressor agent in isoflurane anesthetized dogs. Other beneficial effects of dopamine such as increased CO are not modified by acepromazine.