Comparison of the effect of propofol and sevoflurane on the urethral pressure profile in healthy female dogs

OBJECTIVE: To compare the effects of propofol and sevoflurane on the urethral pressure profile in female dogs. ANIMALS: 10 healthy female dogs. PROCEDURE: Urethral pressure profilometry was performed in awake dogs, during anesthesia with sevoflurane at 1.5, 2.0, and 3.0% end-tidal concentration, and during infusion of propofol at rates of 0.4, 0.8, and 1.2 mg/kg/min. A consistent plane of anesthesia was maintained for each anesthetic protocol. Maximum urethral pressure, maximum urethral closure pressure, functional profile length, and functional area were measured. RESULTS: Mean maximum urethral closure pressure of awake dogs was not significantly different than that of dogs anesthetized with propofol at all infusion rates or with sevoflurane at 1.5 and 2.0% end-tidal concentration. Functional area in awake dogs was significantly higher than in anesthetized dogs. Functional area of dogs during anesthesia with sevoflurane at 3.0% end-tidal concentration was significantly lower than functional area for other anesthetic protocols. Individual differences in the magnitude of effects of propofol and sevoflurane on urethral pressures were observed. CONCLUSIONS AND CLINICAL RELEVANCE: Sevoflurane is an alternative to propofol for anesthesia in female dogs undergoing urethral pressure profilometry. Use of these anesthetics at appropriate administration rates should reliably distinguish normal from abnormal maximum urethral closure pressures and functional areas. Titration of anesthetic depth is a critical component of urodynamic testing.     

Anesthetic indices of sevoflurane and isoflurane in unpremedicated dogs

OBJECTIVE: To compare the anesthetic index of sevoflurane with that of isoflurane in unpremedicated dogs. DESIGN: Randomized complete-block crossover design. ANIMALS: 8 healthy adult dogs. PROCEDURE: Anesthesia was induced by administering sevoflurane or isoflurane through a face mask. Time to intubation was recorded. After induction of anesthesia, minimal alveolar concentration (MAC) was determined with a tail clamp method while dogs were mechanically ventilated. Apneic concentration was determined while dogs were breathing spontaneously by increasing the anesthetic concentration until dogs became apneic. Anesthetic index was calculated as apneic concentration divided by MAC. RESULTS: Anesthetic index of sevoflurane (mean +/- SEM, 3.45 +/- 0.22) was significantly higher than that of isoflurane (2.61 +/- 0.14). No clinically important differences in heart rate; systolic, mean, and diastolic blood pressures; oxygen saturation; and respiratory rate were detected when dogs were anesthetized with sevoflurane versus isoflurane. There was a significant linear trend toward lower values for end-tidal partial pressure of carbon dioxide during anesthesia with sevoflurane, compared with isoflurane, at increasing equipotent anesthetic doses. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that sevoflurane has a higher anesthetic index in dogs than isoflurane. Sevoflurane and isoflurane caused similar dose-related cardiovascular depression, but although both agents caused dose-related respiratory depression, sevoflurane caused less respiratory depression at higher equipotent anesthetic doses.     

Effect of tepoxalin on renal function and hepatic enzymes in dogs exposed to hypotension with isoflurane

ObjectiveTo evaluate the possible renal and hepatic toxicity of tepoxalin in dogs exposed to hypotension during isoflurane anesthesia.Study designProspective, randomized experimental study.AnimalsTwenty adult mixed-breed dogs, weighing 18.8 ± 2.8 kg.MethodsThe animals received 10 mg kg^?1 tepoxalin orally 2 hours before the anesthetic procedure (PRE; n = 6), or 30 minutes after anesthesia (POST; n = 6), along with a control group (CON; n = 8), which were only anesthetized. The PRE and POST groups also received the same dose of tepoxalin for 5 days post-procedure. All dogs were anesthetized with propofol and maintained with isoflurane and the end-tidal isoflurane (Fe’Iso) was increased until mean arterial pressure decreased to 50–60 mmHg. These pressures were maintained for 60 minutes. Heart rate, arterial pressures and Fe’Iso were recorded at 0, 10 and every 10 minutes up to 60 minutes of hypotension. Blood gases, pH, electrolytes and bleeding time were analyzed before and at 30 and 60 minutes of hypotension. Renal and hepatic changes were quantified by serum and urinary biochemistry and creatinine clearance.ResultsSerum concentrations of alanine amino transferase (ALT), alkaline phosphatase (ALP) and σ-glutamyl transferase (GGT), blood urea nitrogen (BUN) and creatinine (Cr), and urinary output, urinary Cr, Cr clearance, and GGT:Cr ratio remained stable throughout the evaluations. During the anesthetic procedure there were no important variations in the physiological parameters. No side effects were observed in any of the groups.Conclusions and clinical relevanceTepoxalin did not cause significant effects on renal function or cause hepatic injury in healthy dogs exposed to hypotension with isoflurane, when administered pre- or postanesthetic and continued for five consecutive days.     

Efficacy of preanesthetic intramuscular administration of ephedrine for prevention of anesthesia-induced hypotension in cats and dogs

To determine if the preanesthetic administration of ephedrine would prevent anesthesia-induced hypotension in dogs and cats, 10 cats were anesthetized with acepromazine, butorphanol, ketamine, and isoflurane, and 8 dogs were anesthetized with acepromazine, morphine, propofol, and halothane. Cats received ephedrine or saline 10 minutes after premedication. Dogs received ephedrine or saline at the time of premedication. Systolic arterial blood pressure, respiratory rate, heart rate, end-tidal CO₂, O₂ saturation, cardiac rhythm, and rectal temperature were recorded.     

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.     

PRACTICALITY, USEFULNESS, AND LIMITS OF END-TIDAL CARBON DIOXIDE MONITORING IN CRITICAL SMALL ANIMAL PATIENTS

End-tidal monitors for measuring carbon dioxide (CO₂) have become widely available for clinical use in the last two decades. This non-invasive technology has been previously evaluated in anesthetized veterinary patients, but its accuracy has not been assessed in critical patients. We investigated the usefulness and limits of end-tidal CO₂ monitoring in two populations of critical small animal patients: spontaneously breathing dogs and mechanically ventilated patients with healthy and damaged lungs. In analyzing samples from 43 spontaneously breathing dogs and 34 ventilated patients (28 dogs and six cats), the end-tidal CO₂ was generally lower than pCO₂. The predictive value for hypoventilation was excellent in both populations (100%). The linear correlation of the end-tidal CO₂ and arterial pCO₂ in non-panting dogs with healthy lungs was 0.84 (p<0.0001), and the 95% confidence interval (CI) of the difference was ± 3.2 mm Hg. However, the measures were uncorrelated in panting dogs (r=0.37, p=0.27), and the 95% CI was ± 13.37 mm Hg. Furthermore, where multiple samples could be obtained in individual patients, the r values and differences of end-tidal compared to arterial pCO₂ varied unpredictably. These variations did not appear to be predicted by patient factors such as lung disease. We conclude that the end-tidal CO₂ monitor is clinically useful for detecting hypoventilation and monitoring apnea, but it should be supplemented with arterial pCO₂ determinations if it is important to obtain accurate pCO₂ measures.     

Cardiovascular Effects of Intravenous Sodium Penicillin, Sodium Cefazolin, and Sodium Citrate in Awake and Anesthetized Horses

Sodium penicillin, sodium cefazolin, and sodium citrate were administered to six adult horses on separate occasions, when awake and during anesthesia. The order of administration was randomized and studies were separated by a minimum of 7 days. Arterial blood pressure decreased significantly (less than 0.05) from control 5 minutes after intravenous (IV) sodium penicillin in awake and anesthetized horses. Systolic arterial blood pressure remained significantly (less than 0.05) decreased 10 minutes after IV sodium penicillin in anesthetized horses. Sodium cefazolin and sodium citrate did not significantly affect any of the measured cardiovascular variables. Although the changes in arterial blood pressure were small (8-15 mm Hg), monitoring of arterial blood pressure is advised when sodium penicillin is administered IV to anesthetized horses.     

Romifidine, medetomidine or xylazine before propofol-halothane-N2O anesthesia in dogs.

The objective of this paper was to evaluate romifidine as a premedicant in dogs prior to propofol-halothane-N2O anesthesia, and to compare it with the other alpha2-agonists (medetomidine and xylazine). For this, ten healthy dogs were anesthetized. Each dog received 3 preanesthetic protocols: atropine (10 microg/kg BW, IM), and as a sedative, romifidine (ROM; 40 microg/kg BW, IM), xylazine (XYL; 1 microg/kg, IM), or medetomidine (MED; 20 microg/kg BW, IM). Induction of anesthesia was delivered with propofol 15 min later and maintained with halothane and N2O for one hour in all cases. The following variables were registered before preanesthesia, 10 min after the administration of preanesthesia, and at 5-minute intervals during maintenance: PR, RR, rectal temperature (RT), MAP, SAP, and DAP. During maintenance, arterial oxygen saturation (SpO2), end-tidal CO2 (EtCO2) and percentage of halothane necessary for maintaining anesthesia (%HAL) were also recorded. Induction dose of propofol (DOSE), time to extubation (TE), time to sternal recumbency (TSR) and time to standing (TS) were also registered. The statistical analysis was carried out during the anesthetic period. ANOVA for repeat measures revealed no differences between the 3 groups for PR and RR; however, MAP, SAP and DAP were higher in the MED group; SpO2 was lower in MED and EtCO2 was lower in ROM; %HAL was higher in XYL. No statistical differences were observed in DOSE, TE, TSR or TS. Percentage of halothane was lower in romifidine and medetomidine than in xylazine premedicated dogs also anesthetized with propofol. All the cardiorespiratory variables measured were within normal limits. The studied combination of romifidine, atropine, propofol, halothane and N2O appears to be a safe and effective drug combination for inducing and maintaining general anesthesia in healthy dogs.     

Effects of intravenous ethyl pyruvate on cardiopulmonary variables and quality of recovery from anesthesia in horses

ObjectiveTo determine the effects of intravenous ethyl pyruvate, an anti-inflammatory with putative benefits in horses with endotoxemia, on cardiopulmonary variables during anesthesia and the quality of anesthetic recovery.Study designRandomized, crossover, blinded experimental design.AnimalsA total of six healthy Standardbred geldings, aged 13 ± 3 years and weighing 507 ± 66 kg (mean ± standard deviation).MethodsHorses were anesthetized for approximately 90 minutes on two occasions with a minimum of 2 weeks apart using xylazine for sedation, ketamine and diazepam for induction, and isoflurane in oxygen for maintenance. Lactated Ringer’s solution (LRS; 10 mL kg^–1 hour^–1) was administered during anesthesia. Treatments were randomized and administered starting approximately 30 minutes after induction of anesthesia and infused over 60 minutes: LRS (1 L) or ethyl pyruvate (150 mg kg^–1 in 1 L LRS). Invasive arterial pressures, heart rate, respiratory rate and end-tidal carbon dioxide tensions were recorded every 5 minutes for the duration of anesthesia. Arterial blood gases, glucose and lactate concentrations were measured every 20 minutes. Anesthetic recovery was video recorded, stored, and subsequently rated by two individuals blinded to treatments. Total recovery time, time to extubation, number of attempts and time to sternal recumbency, number of attempts to stand and time to stand were recorded. Quality of recovery was analyzed. Data between treatments and within a treatment were assessed using two-way repeated-measures anova and a Pearson correlation coefficient, significant at p < 0.05.ResultsAll horses completed the study. No significant differences were detected between the ethyl pyruvate and LRS treatments for either the cardiopulmonary variables or quality of recovery from anesthesia.Conclusions and clinical relevanceThe results suggest that intravenous ethyl pyruvate can be administered to healthy anesthetized horses with minimal impact on the cardiopulmonary variables studied or the quality of recovery from anesthesia.     

Investigation of changes in the middle latency auditory evoked potential during anesthesia with sevoflurane in dogs

OBJECTIVE: To investigate the middle latency auditory evoked potential (MLAEP) in awake dogs and dogs anesthetized with 2 concentrations of sevoflurane. ANIMALS: 10 adult Beagles. PROCEDURE: The MLAEP was recorded while dogs were awake and anesthetized with sevoflurane (end-tidal concentration, 2.7% or 3.5%).Three needle electrodes were inserted SC, and click stimuli were delivered biaurally. Signal acquisition, averaging, and analysis were performed by use of computer software developed in-house. Signals were recorded for 128 milliseconds, and the responses to 1,024 stimuli were averaged. Waveforms from 10 recordings in each dog were averaged, and latencies of peaks were measured. Data acquired for awake dogs and dogs anesthetized with high and low sevoflurane concentrations were compared statistically. RESULTS: Sevoflurane anesthesia attenuated the MLAEP so that only peaks P0, Na, and Pa could be identified. The MLAEP changes were maximal at the lower concentration of sevoflurane evaluated. The latencies of these peaks were significantly shorter in awake dogs, compared with values in anesthetized dogs. No difference in the peak latency was detected between the sevoflurane concentrations. CONCLUSIONS AND CLINICAL RELEVANCE: In terms of CNS responsiveness, the effects of anesthesia with sevoflurane are similar to those of anesthesia with isoflurane. Data suggest that sevoflurane is not the inhalant agent of choice in a research setting where electroencephalographic measurements are to be recorded during anesthesia. The depression of the MLAEP waveform by sevoflurane also suggests that the MLAEP is not a suitable tool with which to monitor anesthetic depth during sevoflurane anesthesia in dogs.     

Effects of sevoflurane, isoflurane and halotane anaesthesia on fluorescein angiographic phases of dogs: a comparative study

A fluorescein angiography method was developed to compare the onset and the total duration of the fluorangiographic phases between three anaesthetic protocols in six healthy mixed-breed dogs. The animals were anaesthetized three times. Each dog received, as pre-anaesthetic protocol, atropine (10 micrograms/kg intramuscularly), and as a sedative, romifidine (80 micrograms/kg intravenously). Fifteen minutes later, induction of anaesthesia was delivered with propofol (1 mg/kg intravenously) and maintained either with sevoflurane (SEVO group), isoflurane (ISO group) or halothane (HAL group) for 30 min in all cases. Some angiographic, cardiovascular and respiratory variables were registered during the procedure. Recovery times were also registered. Angiographic variables recorded were: onset of the arterial phase (TA), onset of the arteriovenous phase (TAV), onset of the venous phase (TV), complete arterial phase duration (I1), complete arteriovenous phase duration (I2) and I1 plus I2 (I3). Mean heart rate, mean arterial pressure, systolic arterial pressure, diastolic arterial pressure, respiratory rate, tidal volume, arterial oxygen saturation and end-tidal CO2 during SEVO and ISO anaesthesia, were similar in dogs. Minute ventilation and rectal temperature were higher in dogs with SEVO than ISO. HAL produced higher arterial pressures and a lower arterial oxygen saturation than ISO and SEVO. Mean respiratory rate, rectal temperature and minute ventilation were higher in HAL. Pulse rate, end-tidal CO2 and tidal volume were similar in the dogs of the three groups. No differences in recovery times were found. The fluorescein angiographic times were within the normal range. There were no significant differences between protocols in I1, I2 or I3. HAL produced a significant increase of all temporal variables (TA, TAV and TV) when compared with ISO; TA was higher in HAL than SEVO-treated dogs. All protocols appear to be safe and effective for inducing and maintaining general anaesthesia in healthy dogs for performing fluorescein angiography.     

The effect of nitrous oxide on halothane, isoflurane and sevoflurane requirements in ventilated dogs undergoing ovariohysterectomy

OBJECTIVE: To examine the effect of 64% nitrous oxide (N2O) on halothane (HAL), isoflurane (ISO) or sevoflurane (SEV) requirements in dogs undergoing ovariohysterectomy. STUDY DESIGN: Prospective, randomized, clinical trial. ANIMALS: Ninety, healthy dogs of (mean +/- SD) body weight 21.2 +/- 10.0 kg and age 17.8 +/- 22.8 months. MATERIALS AND METHODS: After premedication with acepromazine, hydromorphone and glycopyrrolate, anesthesia was induced with thiopental administered to effect. Dogs received one of six inhalant protocols (n = 15 group): HAL; HAL/N2O; ISO; ISO/N2O; SEV; or SEV/N2O. End-tidal CO2 was maintained at 40 +/- 2 mmHg with intermittent positive pressure ventilation (IPPV). Body temperature, heart rate, indirect systemic arterial blood pressures, inspired and end-tidal CO2, volatile agent, N2O and O2 were recorded every 5 minutes. The vaporizer setting was decreased in 0.25-0.5% decrements to elicit a palpebral reflex, and this level maintained. Statistical analysis included two-way anova for repeated measures with Bonferroni's correction factor and statistical significance assumed when p < 0.05. Percentage reduction in end-tidal volatile agent was calculated at 60 minutes after starting study. RESULTS: End-tidal HAL, ISO and SEV decreased when N2O was administered. Percentage reduction: HAL (12.4%); ISO (37.1%) and SEV (21.4%). Diastolic, mean and systolic blood pressures increased in ISO/N2O compared with ISO. Heart rate increased in ISO/N2O and SEV/N2O compared with ISO and SEV, respectively. Systolic, mean and diastolic blood pressures increased in SEV compared with HAL and ISO. Systolic, mean, diastolic blood pressures and heart rate increased in SEV/N2O and ISO/N2O compared with HAL/N2O. CONCLUSIONS: N2O reduces HAL, ISO and SEV requirements in dogs undergoing ovariohysterectomy. Cardiovascular stimulation occurred when N2O was used with ISO, less so with SEV and not with HAL     

Recovery from neuromuscular block in dogs: restoration of spontaneous ventilation does not exclude residual blockade

ObjectiveTo evaluate if return of spontaneous ventilation to pre-relaxation values indicates complete recovery from neuromuscular blockade.Study designProspective, with each individual acting as its own control.AnimalsTen healthy adult female Beagle dogs weighing 6.2–9.4 kg.MethodsDogs were anesthetized with propofol, dexemedetomidine and isoflurane. Spontaneous ventilation was assessed by measuring end-tidal CO₂, expired tidal volume, peak inspiratory flow, respiratory rate and minute ventilation. Vecuronium 25 μg kg^?1 IV was administered and neuromuscular block was evaluated by measuring the train-of-four (TOF) ratio with acceleromyography in the hind limb. During spontaneous recovery from neuromuscular block, the TOF ratio when each ventilatory variable returned to baseline was recorded.ResultsThis dose of vecuronium produced moderate neuromuscular block in all dogs, with TOF ratio values of 0–18% at maximal block. Expired tidal volume, peak inspiratory flow and minute ventilation returned to pre-relaxation values when the median TOF ratio was ≤ 20%. The median TOF ratio was 42% when the end-tidal CO₂ returned to pre-relaxation values.Conclusions and clinical relevanceSignificant residual neuromuscular block could be measured at the hind limb with acceleromyography when ventilation had spontaneously returned to pre-vecuronium values. Monitoring spontaneous ventilation, including end-tidal CO₂, expired tidal volume, peak inspiratory flow or minute ventilation cannot be used as a surrogate for objective neuromuscular monitoring, and this practice may increase the risk of postoperative residual paralysis.     

The effect of a pre‐anesthetic infusion of amino acids on body temperature,venous blood pH,glucose, creatinine,and lactate of healthy dogs during anesthesia

ObjectiveTo evaluate the effect of preanesthetic, intravenous (IV) amino acids on body temperature of anesthetized healthy dogs.Study designRandomized, experimental, crossover study.AnimalsEight mixed-breed dogs approximately 2 years of age weighing 20.7 ± 2.1 kg.MethodsDogs received 10% amino acid solution (AA) or 0.9% saline (SA) IV at 5 mL kg⁻¹ over 60 minutes. Body temperature (BT) was recorded at 5 minute intervals during infusions. Dogs were then anesthetized with sevoflurane for 90 minutes. BT was recorded at 5 minute intervals during anesthesia. Jugular blood samples were analyzed for pH, glucose, creatinine, and lactate concentrations at baseline, after infusion, after anesthesia and after 24 hours.ResultsBT at conclusion of infusion decreased -0.34 ± 0.42 °C in group AA and -0.40 ± 0.38 °C in group SA and was not different between groups (p = 0.072). BT decreased 2.72 ± 0.37 °C in group AA and 2.88 ± 0.26 °C in group SA after anesthesia and was different between groups (p < 0.05). Creatinine in group AA was increased immediately after infusion (p < 0.0001) and at 24 hours (p < 0.0001). There were no differences between groups for other parameters. Values for both groups were never outside the clinical reference ranges.Conclusions and clinical relevanceIn healthy dogs, preanesthetic IV infusion of amino acids attenuated heat loss compared to controls, however, the amount attenuated may not be clinically useful. Further studies are warranted to determine if nutrient-induced thermogenesis is beneficial to dogs undergoing anesthesia.     

Cardiovascular effects of butorphanol administration in isoflurane-O2 anesthetized healthy dogs

Cardiovascular consequences of butorphanol tartrate (0.2 mg/kg of body weight, IV) administration during isoflurane (1.7% end-tidal concentration) anesthesia were determined in mechanically ventilated healthy dogs. Butorphanol administration caused significant (P less than or equal to 0.05) reductions in mean, systolic, and diastolic arterial blood pressures; cardiac output; and rate-pressure product.     

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.     

Bacterial Isolates from Blood Cultures of Dogs Undergoing Dentistry

Bacteria in blood cultures in 30 dogs undergoing high-speed dental scaling and tooth extraction were examined. One or more positive blood cultures were identified in 9 of 30 (30%) dogs. Pasteurella spp. were most frequently (5 dogs) isolated and were sensitive to ampicillin, penicillin, cephalothin, chloramphenicol, tetracycline, amoxicillin with clavulanic acid, and sul-famethoxazole with trimethoprim. Twg groups of 15 dogs each, anesthetized or sedated but not undergoing dental procedures, served as non-dentistry controls. There were no significant (p < .05) differences between the number of positive cultures in dentistry and non-dentistry groups. In healthy dogs undergoing high-speed dental scaling and tooth extraction, the occurrence of bacteria in blood cultures was much lower than previously reported. The clinical significance of positive blood cultures was uncertain.     

Acute cardiovascular effects and pharmacokinetics of carvedilol in healthy dogs

OBJECTIVE: To determine acute cardiovascular effects and pharmacokinetics of carvedilol in healthy dogs. ANIMALS: 14 mature healthy Beagles. PROCEDURE: 12 dogs were anesthetized with morphine and alpha-chloralose. Catheters were placed in the aorta, left ventricle, and right atrium to record systemic and pulmonary pressures and determine vascular resistance and cardiac output. Electrocardiograms (leads I, aVF, and V3) were recorded to determine electrocardiographic changes. Variables were measured before and after IV injection of incremental doses of carvedilol (cumulative doses, 10, 30, 70, 150, 310, and 630 microg/kg of body weight; n = 6) or vehicle alone (6). Pharmacokinetic analysis was performed, using 2 conscious dogs given 160 microg of carvedilol/kg as a single IV injection. RESULTS: Heart rate and velocity of fiber shortening at zero load (Vmax) increased slightly but significantly from baseline values at doses of carvedilol > or = 310 microg/kg and 10 microg/kg, respectively. Carvedilol did not affect systemic and pulmonary pressures or vascular resistances. Intravenous administration of approximately 150 microg of carvedilol/kg resulted in a plasma carvedilol concentration of approximately 100 ng/ml. Mean elimination half-life was 54 minutes, half-life of distribution was 3.5 minutes, and volume of distribution was 2,038 ml/kg. CONCLUSIONS AND CLINICAL RELEVANCE: The therapeutic plasma concentration of carvedilol in humans is 100 ng/ml. At that plasma concentration in dogs, the reduction in afterload and positive inotropic effect that we observed would be beneficial for treating heart failure and minimizing the cardiotoxic effects of doxorubicin.     

Effects of Cephalothin, Cefazolin, and Cefmetazole on the Hemostatic Mechanism in Normal Dogs: Implications for the Surgical Patient

Twenty-six female beagles were used to evaluate the effects of intravenous and long-term subcutaneous administration of cephalothin, cefazolin, and cefmetazole on platelet function and the coagulation cascade. Platelet aggregation in response to an adenosine diphosphate (ADP) agonist, bleeding time, platelet count, platelet size, prothrombin time (PT), and activated partial thromboplastin times (aPTT) were evaluated before and 90 minutes after two intravenous doses (22 mg/kg) of cephalothin, cefazolin, and cefmetazole given at 90-minute intervals. Dogs given saline injections were used as controls. Platelet count, platelet size, PT, and aPTT were evaluated after 7 days of subcutaneous administration of saline, cefazolin, and cefmetazole (22 mg/kg every 8 hours). A significant decrease in platelet aggregation in response to ADP was detected 90 minutes after intravenous administration of cephalothin. Bleeding time was increased significantly 90 minutes after intravenous administration of cefmetazole. Platelet size was decreased significantly 24 hours after onset of the study in all animals, including controls. No significant changes in platelet count, platelet size, PT, or aPTT were detected after 7 days of subcutaneous administration. Cefazolin had no adverse effects on platelet aggregation in response to ADP, bleeding time, platelet count, platelet size, PT, or aPTT. Therefore, cefazolin should be considered as a perioperative antibiotic in dogs with conditions predisposing to hemostatic complications.     

The effect of carotid artery occlusion on lingual arterial blood pressure in dogs.

Although temporary occlusion of the carotid arteries is commonly done to reduce blood loss during nasal surgery in the dog, data supporting its use are mostly anecdotal and subjective. Twelve dogs were placed under general inhalation anesthesia and mechanically ventilated to maintain normocapnea and an end-tidal halothane concentration equivalent to 1.3 times the minimum alveolar concentration. Tourniquets were placed around both carotid arteries of each dog. Both lingual arteries were cannulated in each dog and their heart rate and blood pressure were measured bilaterally. During unilateral carotid artery occlusion, the blood pressures in the ipsilateral lingual artery were significantly (P < 0.05) lower than the preocclusion control pressures and pressures recorded in the contralateral vessel. Bilateral carotid artery occlusion resulted in a further significant (P < 0.05) fall in all lingual arterial pressures. The recorded heart rates only varied significantly from preocclusion control values when they increased during bilateral carotid occlusion (P < 0.05). The results of this study confirm that carotid artery occlusion has the potential to reduce intraoperative blood loss during oronasal surgery in the dog.