Effects of acetylpromazine or morphine on urine production in halothane-anesthetized dogs

Cardiovascular and renal effects of constant rate infusions of remifentanil, dexmedetomidine and their combination in dogs anesthetized with sevoflurane

We evaluated changes in cardiovascular and renal functions as well as arginine vasopressin (AVP) secretion, with remifentanil and dexmedetomidine administration alone or in combination in sevoflurane-anesthetized dogs. Six healthy adult Beagle dogs received one of the following four treatments in a randomized crossover study: saline (C), remifentanil alone at successively increasing doses (R; 0.15, 0.60, and 2.40 µg/kg/min), dexmedetomidine alone (D; 0.5 µg/kg intravenously for initial 10 min followed by a constant rate infusion at 0.5 µg/kg/hr), and a combination of remifentanil and dexmedetomidine at the above-mentioned doses (RD). Sevoflurane doses were adjusted to 1.5 times of minimum alveolar concentration (MAC) equivalent according to MAC-sparing effects with remifentanil and dexmedetomidine as previously reported. Cardiovascular measurements, renal function data, and plasma AVP concentrations were determined before and every 60 min until 180 min after drug administration as per each treatment. In the R, D and RD, heart rate significantly decreased and mean arterial pressure significantly increased from baseline or with C. Cardiac index significantly decreased and systemic vascular resistance index increased with D and RD. Oxygen extraction ratio, renal blood flow, and glomerular filtration rate were not affected. The plasma AVP concentrations significantly decreased in D and RD, but increased in R. Only in D, the natriuresis was elicited. The combination of remifentanil and dexmedetomidine in sevoflurane-anesthetized dogs was acceptable in terms of the hemodynamics, oxygenation, and renal function. Remifentanil may interfere with dexmedetomidine-induced diuresis and inhibition of AVP secretion.

Comparison of acid-base and electrolyte changes following administration of 6% hydroxyethyl starch 130/0.42 in a saline and a polyionic solution in anaesthetized dogs

OBJECTIVE

To evaluate the effects of a 6% hydroxyethyl starch (130/0.42) in either a buffered, electrolyte-balanced (HES-BAL) or saline (HES-SAL) carrier solution on electrolyte concentrations and acid-base parameters in healthy anaesthetized dogs.

STUDY DESIGN

Prospective randomised clinical study.

ANIMALS

A group of 40 client-owned dogs undergoing general anaesthesia for elective surgical procedures or diagnostic imaging.

METHODS

During anaesthesia, dogs were intravenously administered 15 mL kg^-1 of either HES-SAL (n = 20) or HES-BAL (n = 20) over 30-40 minutes. Jugular blood samples were analysed before (T₀) and 5 minutes (T₅), 1 hour (T₆₀) and 3 hours (T₁₈₀) after fluid administration. Sodium, potassium, chloride, ionised calcium, phosphate, albumin, pH, venous pCO₂, base excess (BE), bicarbonate and anion gap were determined and strong ion difference (SID) and total quantity of weak nonvolatile acids were calculated for each time point.

RESULTS

Chloride was significantly increased at T₅, T₆₀ and T₁₈₀ compared with T₀ after HES-SAL, and was significantly greater after HES-SAL than after HES-BAL at T₅ (p = 0.042). Ionised calcium was significantly decreased at T₅ compared with T₀ after HES-SAL, and was significantly lower after HES-SAL than after HES-BAL at T₅ (p < 0.001). Bicarbonate was significantly lower after HES-SAL than after HES-BAL at T₅ (p = 0.004) and T₆₀ (p = 0.032). BE was significantly lower after HES-SAL than after HES-BAL at T₅ (p < 0.001) and T₆₀ (p = 0.007). SID was significantly decreased after HES-SAL at T₅ and T₆₀ compared with T₀, and was significantly lower after HES-SAL than after HES-BAL at T₅ (p = 0.027). Mean electrolyte and acid-base parameters remained within or marginally outside of reference intervals.

CONCLUSIONS AND CLINICAL RELEVANCE

Changes in both groups were minor and short-lived with either fluid in healthy individuals, but might become clinically relevant with higher fluid doses or in critically ill dogs.

Anaesthetic induction and recovery characteristics of a diazepam-ketamine combination compared with propofol in dogs

Induction of anaesthesia occasionally has been associated with undesirable behaviour in dogs. High quality of induction of anaesthesia with propofol has been well described while in contrast variable induction and recovery quality has been associated with diazepam-ketamine. In this study, anaesthetic induction and recovery characteristics of diazepam-ketamine combination with propofol alone were compared in dogs undergoing elective orchidectomy. Thirty-six healthy adult male dogs were used. After habitus scoring (simple descriptive scale [SDS]), the dogs were sedated with morphine and acepromazine. Forty minutes later a premedication score (SDS) was allocated and general anaesthesia was induced using a combination of diazepam-ketamine (Group D/K) or propofol (Group P) and maintained with isoflurane. Scores for the quality of induction, intubation and degree of myoclonus were allocated (SDS). Orchidectomy was performed after which recovery from anaesthesia was scored (SDS) and times to extubation and standing were recorded. Data were analysed using descriptive statistics and Kappa Reliability and Kendall Tau B tests. Both groups were associated with acceptable quality of induction and recovery from anaesthesia. Group P, however, was associated with a poorer quality of induction (p = 0.014), prolonged induction period (p = 0.0018) and more pronounced myoclonus (p = 0.003), but had better quality of recovery (p = 0.000002) and shorter recovery times (p = 0.035) compared with Group D/K. Diazepam-ketamine and propofol are associated with acceptable induction and recovery from anaesthesia. Propofol had inferior anaesthetic induction characteristics, but superior and quicker recovery from anaesthesia compared with diazepam-ketamine.

Defining normal adrenal function testing in the intensive care unit setting: a canine study

OBJECTIVE

To determine whether intensive care medicine therapies and testing influence hypothalamic-pituitary-adrenal test results. It is routine in intensive care medicine to measure hypothalamic-pituitary-adrenal function, commonly utilizing the adrenocorticotropic hormone stimulation test to diagnose absolute or relative adrenal insufficiency.

DESIGN

Prospective, 96-hr animal study.

SETTING

Research laboratory.

SUBJECTS

Twenty-four healthy canines.

INTERVENTIONS

Animals were randomized into two groups--awake and unrestrained or treated with intensive care medicine therapies, including sedation, intubation, and mechanical ventilation. Animals were further randomized to receive dexamethasone (or placebo) or undergo either a total of four or seven adrenocorticotropic hormone stimulation tests over 96 hrs.

MEASUREMENTS AND MAIN RESULTS

Sedation, intubation, and mechanical ventilation transiently increased both basal and postadrenocorticotropic hormone total and free cortisol concentrations >2-fold as compared with baseline for the first 24 hrs (p < or = .05 for both). Performance of seven stimulation tests increased both basal and postadrenocorticotropic hormone total and free cortisol concentrations from baseline by >1.5-fold for the duration of the 96-hr study (p < or = .05). Neither sedation, intubation, and mechanical ventilation nor the performance of more stimulation tests affected delta cortisol measurements (total or free cortisol, p = NS). In contrast, dexamethasone suppressed basal total cortisol concentrations by >2-fold (p < or = .005) at all time points and transiently increased delta total cortisol by approximately 35% during the first 24 hrs of the study (p < or = .05).

CONCLUSIONS

Total and free cortisol measurements--whether pre- or post- adrenocorticotropic hormone or as a calculated delta--were altered by intensive care therapies or frequent adrenocorticotropic hormone stimulation testing with one exception. Delta free cortisol was the only hypothalamic-pituitary-adrenal measurement unaffected by sedation, intubation, and mechanical ventilation, completion of more adrenocorticotropic hormone stimulation tests, or dexamethasone therapy. These findings support the need to determine normal ranges for hypothalamic-pituitary-adrenal testing in subjects receiving intensive care medicine before establishing laboratory criteria for the diagnosis of relative adrenal insufficiency.

Evaluation of the efficacy and safety for use of two sedation and analgesia protocols to facilitate assisted ventilation of healthy dogs

OBJECTIVE

To determine the effectiveness and safety of 2 sedative-analgesic protocols to facilitate assisted ventilation in healthy dogs.

ANIMALS

12 healthy dogs.

PROCEDURES

Dogs were randomly assigned to 2 groups. Mean dosages for protocol 1 were diazepam (0.5 mg/kg/h [n = 3 dogs]) or midazolam (0.5 mg/kg/h [3]), morphine (0.6 mg/kg/h [6]), and medetomidine (1.0 microg/kg/h [6]). Mean dosages for protocol 2 were diazepam (0.5 mg/kg/h [n = 3]) or midazolam (0.5 mg/kg/h [3]), fentanyl (18 microg/kg/h [6]), and propofol (2.5 mg/kg/h [6]). Each dog received the drugs for 24 consecutive hours. All dogs were mechanically ventilated with adjustments in minute volume to maintain normocapnia and normoxemia. Cardiorespiratory variables were recorded. A numeric comfort score was assigned hourly to assess efficacy. Mouth care, position change, and physiotherapy were performed every 6 hours. Urine output was measured every 4 hours.

RESULTS

Use of both protocols maintained dogs within optimal comfort ranges > 85% of the time. The first dog in each group was excluded from the study. Significant decreases in heart rate, oxygen consumption, and oxygen extraction ratio were evident for protocol 1. Cardiac index values in ventilated dogs were lower than values reported for healthy unsedated dogs. Oxygen delivery, lactate concentration, and arterial base excess remained within reference ranges for both protocols.

CONCLUSIONS AND CLINICAL RELEVANCE

Use of both protocols was effective for facilitating mechanical ventilation. A reduction in cardiac index was detected for both protocols as a result of bradycardia. However, oxygen delivery and global tissue perfusion were not negatively affected.