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  • Author or Editor: Carolina Riccó x
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Abstract

Objective—To compare the hemodynamic responses to orotracheal intubation following induction of anesthesia with propofol, ketamine-propofol, and ketamine-diazepam in premedicated dogs.

Design—Prospective, randomized, masked study.

Animals—10 healthy adult Beagles.

Procedures—Dogs were randomly allocated to be anesthetized twice, with a 1-week wash-out interval, by means of 2 of 3 possible protocols (propofol [4 mg/kg {1.8 mg/lb}, n = 6 dogs], ketamine [2 mg/kg {0.9 mg/lb}] and propofol [2 mg/kg; 7], or ketamine [5 mg/kg {2.3 mg/lb}] and diazepam [0.2 mg/kg {0.09 mg/lb}; 6]). After instrumentation, continuous heart rate, systolic arterial blood pressure, mean arterial blood pressure, diastolic arterial blood pressure, cardiac index, stroke volume index, and systemic vascular resistance were recorded. Fifteen minutes after premedication, dogs were anesthetized; all anesthetics were administered IV. After 5 minutes, orotracheal intubation was performed without the use of a laryngoscope. Data were collected prior to intubation (baseline), at intubation, and 30, 60, 90, 120, 150, and 180 seconds thereafter. Results were compared among the 3 groups and over time.

Results—No differences among groups were observed for any variables studied. In all groups, arterial blood pressures were significantly decreased at various time points after intubation. A significant increase in systolic arterial blood pressure was observed between baseline and the 30-second time point in the ketamine-diazepam group. No significant differences were detected over time for the other variables in any group.

Conclusions and Clinical Relevance—Intubation after anesthetic induction with ketamine-diazepam caused transitory hypertension, whereas intubation after induction with propofol or ketamine-propofol did not cause cardiovascular stimulation. In dogs in which hypertension is a concern, propofol or ketamine-propofol may be a better choice for induction prior to orotracheal intubation.

Restricted access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To evaluate the cardiorespiratory effects of IV administration of propofol (4 mg/kg), ketamine hydrochloride and propofol (2 mg/kg each; K-P), or ketamine hydrochloride (5 mg/kg) and diazepam (0.2 mg/kg; K-D) before and after induction of anesthesia (IoA) in dogs sedated with acepromazine maleate and oxymorphone hydrochloride.

Animals—10 healthy adult Beagles.

Procedures—Each dog was randomly allocated to receive 2 of 3 treatments (1-week interval). For instrumentation prior to each treatment, each dog was anesthetized with isoflurane. After full recovery, acepromazine (0.02 mg/kg) and oxymorphone (0.05 mg/kg) were administered IV. Fifteen minutes later (before IoA), each dog received treatment IV with propofol, K-P, or K-D. Cardiorespiratory and arterial blood gas variables were assessed before, immediately after, and 5 minutes after IoA.

Results—Compared with findings before IoA, dogs receiving the K-P or K-D treatment had increased cardiac output, oxygen delivery, and heart rate 5 minutes after IoA; K-P administration did not change mean arterial blood pressure or stroke volume and decreased systemic vascular resistance. Propofol decreased mean arterial blood pressure and systemic vascular resistance immediately after IoA but did not change heart rate, cardiac output, or oxygen delivery. All treatments caused some degree of apnea, hypoventilation, and hypoxemia (Pao 2 < 80 mm Hg).

Conclusions and Clinical Relevance—In dogs, K-P treatment maintained mean arterial blood pressure better than propofol alone and increased heart rate, cardiac output, or oxygen delivery, as did the K-D treatment. Supplemental 100% oxygen should be provided during IoA with all 3 treatments.

Full access
in American Journal of Veterinary Research
in Journal of the American Veterinary Medical Association
in Journal of the American Veterinary Medical Association

Abstract

Objective—To identify ventilatory protocols that yielded good image quality for thoracic CT and hemodynamic stability in cats.

Animals—7 healthy cats.

Procedures—Cats were anesthetized and ventilated via 4 randomized protocols (hyperventilation, 20 seconds [protocol 1]; single deep inspiration, positive inspiratory pressure of 15 cm H2O [protocol 2]; recruitment maneuver [protocol 3]; and hyperventilation, 20 seconds with a positive end-expiratory pressure of 5 cm H2O [protocol 4]). Thoracic CT was performed for each protocol; images were acquired during apnea for protocols 1 and 3 and during positive airway pressure for protocols 2 and 4. Heart rate; systolic, mean, and diastolic arterial blood pressures; blood gas values; end-tidal isoflurane concentration; rectal temperature; and measures of atelectasis, total lung volume (TLV), and lung density were determined before and after each protocol.

Results—None of the protocols eliminated atelectasis; the number of lung lobes with atelectasis was significantly greater during protocol 1 than during the other protocols. Lung density and TLV differed significantly among protocols, except between protocols 1 and 3. Protocol 2 TLV exceeded reference values. Arterial blood pressure after each protocol was lower than before the protocols. Mean and diastolic arterial blood pressure were higher after protocol 3 and diastolic arterial blood pressure was higher after protocol 4 than after protocol 2.

Conclusions and Clinical Relevance—Standardization of ventilatory protocols may minimize effects on thoracic CT images and hemodynamic variables. Although atelectasis was still present, ventilatory protocols 3 and 4 provided the best compromise between image quality and hemodynamic stability.

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE

To determine the effect of oral administration of gabapentin (20 mg/kg) on the minimum alveolar concentration (MAC) of isoflurane in dogs.

ANIMALS

6 healthy adult dogs (3 males and 3 females with a mean ± SD body weight of 24.8 ± 1.3 kg).

PROCEDURES

Each dog was anesthetized twice. Dogs were initially assigned to 1 of 2 treatments (gabapentin [20 mg/kg, PO] followed 2 hours later by anesthesia maintained with isoflurane or anesthesia maintained with isoflurane alone). A minimum of 7 days later, dogs received the other treatment. The MAC of isoflurane was determined by use of an iterative bracketing technique with stimulating electrodes placed in the maxillary buccal mucosa. Hemodynamic variables and vital parameters were recorded at the lowest end-tidal isoflurane concentration at which dogs did not respond to the stimulus. Effect of treatment on outcome variables was analyzed by use of a paired t test.

RESULTS

Mean ± SD MAC of isoflurane was significantly lower when dogs received gabapentin and isoflurane (0.71 ± 0.12%) than when dogs received isoflurane alone (0.91 ± 0.26%). Mean reduction in MAC of isoflurane was 20 ± 14%. Hemodynamic variables did not differ significantly between treatments. Mean time to extubation was significantly less when dogs received gabapentin and isoflurane (6 ± 4 minutes) than when dogs received isoflurane alone (23 ± 15 minutes).

CONCLUSIONS AND CLINICAL RELEVANCE

Oral administration of gabapentin 2 hours before anesthesia maintained with isoflurane had a MAC-sparing effect with no effect on hemodynamic variables or vital parameters of dogs.

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE

To evaluate the sedative and cardiorespiratory effects of IM administration of alfaxalone and butorphanol combined with acepromazine, midazolam, or dexmedetomidine in dogs.

ANIMALS

6 young healthy mixed-breed hounds.

PROCEDURES

Dogs received each of 3 treatments (alfaxalone [2 mg/kg] and butorphanol [0.4 mg/kg] combined with acepromazine [0.02 mg/kg; AB-ace], midazolam [0.2 mg/kg; AB-mid], or dexmedetomidine [0.005 mg/kg; AB-dex], IM) in a blinded, randomized crossover-design study with a 1-week washout period between treatments. Sedation scores and cardiorespiratory variables were recorded at predetermined time points. Data were analyzed by use of mixed-model ANOVA and linear generalized estimating equations with post hoc adjustments.

RESULTS

All treatments resulted in moderate to deep sedation (median score, ≥ 15/21) ≤ 5 minutes after injection. Sedation scores did not differ among treatments until the 40-minute time point, when the score was higher for AB-dex than for other treatments. Administration of AB-dex resulted in median scores reflecting deep sedation until 130 minutes, versus 80 and 60 minutes for AB-ace and AB-mid, respectively, after injection. Heart rate, cardiac output, and oxygen delivery decreased significantly after AB-dex, but not AB-ace or AB-mid administration. Respiratory variables remained within clinically acceptable ranges after all treatments. Undesirable recovery characteristics were observed in 4 dogs after AB-mid treatment. Four dogs required atipamezole administration 180 minutes after AB-dex injection.

CONCLUSIONS AND CLINICAL RELEVANCE

All protocols produced reliable sedation. The results indicated that in young, healthy dogs, AB-mid may produce undesirable recovery characteristics; AB-dex treatment caused cardiovascular depression and should be used with caution.

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE

To investigate the effects of a priming dose of alfaxalone on the total anesthetic induction dose for and cardiorespiratory function of sedated healthy cats.

ANIMALS

8 healthy adult cats.

PROCEDURES

For this crossover study, cats were sedated with dexmedetomidine and methadone administered IM. Cats next received a priming induction dose of alfaxalone (0.25 mg/kg, IV) or saline (0.9% NaCl) solution (0.025 mL/kg, IV) over 60 seconds and then an induction dose of alfaxalone (0.5 mg/kg/min, IV) until orotracheal intubation was achieved. Cardiorespiratory variables were recorded at baseline (immediately prior to priming agent administration), immediately after priming agent administration, after orotracheal intubation, and every 2 minutes until extubation. The total induction dose of alfaxalone was compared between the 2 priming agents.

RESULTS

Mean ± SD total anesthetic induction dose of alfaxalone was significantly lower when cats received a priming dose of alfaxalone (0.98 ± 0.28 mg/kg), compared with when cats received a priming dose of saline solution (1.41 ± 0.17 mg/kg). Mean arterial blood pressure was significantly higher when alfaxalone was used as the priming dose. No cats became apneic or had a hemoglobin oxygen saturation of < 90%. Expired volume per minute was not significantly different between the 2 priming agents.

CONCLUSIONS AND CLINICAL RELEVANCE

Administration of a priming dose of alfaxalone to healthy sedated cats reduced the total dose of alfaxalone needed to achieve orotracheal intubation, maintained mean arterial blood pressure, and did not adversely impact the measured respiratory variables.

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE

To determine pharmacokinetic and pharmacodynamic properties of the injectable formulation of dexmedetomidine administered via the oral transmucosal (OTM) route to healthy dogs.

ANIMALS

6 healthy dogs.

PROCEDURES

Injectable dexmedetomidine was administered IV (5 μg/kg) or via the OTM route (20 μg/kg) in a blinded, single-observer, randomized crossover study. Dogs received dexmedetomidine and a sham treatment at each administration. Serial blood samples were collected from a catheter in a saphenous vein. Heart rate, respiratory rate, and subjective sedation score were assessed for 24 hours after administration. Plasma samples were analyzed for dexmedetomidine concentrations by use of ultraperformance liquid chromatography–tandem mass spectrometry.

RESULTS

For the OTM route, the mean ± SD maximum plasma concentration was 3.8 ± 1.3 ng/mL, which was detected 73 ± 33 minutes after administration. The mean maximum concentration for the IV dose, when extrapolated to the time of administration, was 18.6 ± 3.3 ng/mL. The mean terminal-phase half-life was 152 ± 146 minutes and 36 ± 6 minutes for OTM and IV administration, respectively. After IV administration, total clearance was 8.0 ± 1.6 mL/min/kg and volume of distribution at steady state was 371 ± 72 mL/kg. Bioavailability for OTM administration of dexmedetomidine was 11.2 ± 4.5%. Peak sedation scores did not differ significantly between routes of administration. Decreases in heart rate, respiratory rate, and peak sedation score were evident sooner after IV administration.

CONCLUSIONS AND CLINICAL RELEVANCE

OTM administration of the injectable formulation of dexmedetomidine resulted in a similar degree of sedation and prolonged duration of action, compared with results for IV administration, despite relatively low bioavailability.

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE

To evaluate the pharmacokinetics and pharmacodynamics of naloxone hydrochloride in dogs following intranasal (IN) and IV administration.

ANIMALS

6 healthy adult mixed-breed dogs.

PROCEDURES

In a blinded crossover design involving 2 experimental periods separated by a washout period (minimum of 7 days), dogs were randomly assigned to receive naloxone IN (4 mg via a commercially available fixed-dose naloxone atomizer; mean ± SD dose, 0.17 ± 0.02 mg/kg) or IV (0.04 mg/kg) in the first period and then the opposite treatment in the second period. Plasma naloxone concentrations, dog behavior, heart rate, and respiratory rate were evaluated for 24 hours/period.

RESULTS

Naloxone administered IN was well absorbed after a short lag time (mean ± SD, 2.3 ± 1.4 minutes). Mean maximum plasma concentration following IN and IV administration was 9.3 ± 2.5 ng/mL and 18.8 ± 3.9 ng/mL, respectively. Mean time to maximum concentration following IN administration was 22.5 ± 8.2 minutes. Mean terminal half-life after IN and IV administration was 47.4 ± 6.7 minutes and 37.0 ± 6.7 minutes, respectively. Mean bioavailability of naloxone administered IN was 32 ± 13%. There were no notable changes in dog behavior, heart rate, or respiratory rate following naloxone administration by either route.

CONCLUSIONS AND CLINICAL RELEVANCE

Use of a naloxone atomizer for IN naloxone administration in dogs may represent an effective alternative to IV administration in emergency situations involving opioid exposure. Future studies are needed to evaluate the efficacy of IN naloxone administration in dogs with opioid intoxication, including a determination of effective doses.

Full access
in American Journal of Veterinary Research