Effects of ketamine constant rate infusions on cardiac biomarkers and cardiac function in dogs

Effect of a constant rate infusion of ketamine on left ventricular systolic and diastolic function in dogs anesthetized with propofol

OBJECTIVE

To evaluate the effect of a constant rate infusion of ketamine on left ventricular systolic and diastolic function in dogs anesthetized with propofol.

STUDY DESIGN

Prospective randomized, blinded clinical study.

ANIMALS

Sixteen healthy dogs.

METHODS

Dogs were randomized into two groups, the propofol-ketamine group (GPK) and propofol group (GP), with eight animals each. Anesthesia was induced with propofol and maintained with a constant rate infusion (CRI) of propofol at a rate of 0.8 mg/kg/min. All dogs were mechanically ventilated throughout the study. Thirty-five minutes after anesthesia started, the GPK received a bolus of ketamine (0.5 mg/kg IV, over 2 minutes) followed by the CRI of ketamine at 30 μg/kg/min, while the GP received the same volume of 0.9% NaCl over 2 minutes followed by the CRI of 0.9% NaCl at the same rate. Hemodynamic and echocardiographic variables were recorded 15 min after initiating CRI of propofol (M0), immediately after each treatment bolus (M1), and 20 (M2) and 40 min (M3) after initiating CRI of ketamine or 0.9% NaCl solution in both groups.

RESULTS

Cardiac index, stroke index, and peripheral vascular resistance index were not significantly different between treatments. No significant differences in left ventricular systolic and diastolic functions derived from echocardiographic variables were observed between groups.

CONCLUSIONS AND CLINICAL RELEVANCE

During treatment with CRI of ketamine at the proposed rate, hemodynamic parameters and echocardiographic variables, used to measure left ventricular systolic and diastolic function, were maintained stable in healthy dogs anesthetized with propofol.

Plasma concentration, cardiorespiratory and analgesic effects of ketamine-fentanyl infusion in dogs submitted to mastectomy

Background

The analgesic and cardiorespiratory effects of ketamine, fentanyl, or ketamine-fentanyl constant rate infusion (CRI) in dogs undergoing mastectomy were evaluated. Seventeen female dogs received CRI of ketamine (GK [n = 6]: bolus 0.5 mg/kg; CRI 20 µg/kg/min in intra- and postoperative periods], fentanyl (GF [n = 5]: bolus 20 µg/kg; intraoperative CRI 5 20 µg/kg/hour and postoperative CRI 2 20 µg/kg/hour), or combination of ketamine-fentanyl (GKF [n = 6]: aforementioned doses) for 8 h. Cardiorespiratory, blood gas analyses, plasma drug concentrations, sedation score (SS), Pain Scores were evaluated.

Results

The heart rate decreased in the GF and GKF (p < 0.04); the mean arterial pressure was lower in the GKF than in the GK at 35 min (p < 0.001). Maximum plasma concentrations were observed 5 min after bolus in the GK (2847.06 ± 2903.03 ng/mL) and GKF (2811.20 ± 1931.76 ng/mL). Plasma concentration in intraoperative period of ketamine was of > 100 ng/mL in 5/5 and 2/5 animals in the GKF and GK, respectively; and > 1.1 ng/mL of fentanyl in 4/5 and 3/5 in GKF and GF, respectively.

Conclusion

Ketamine with/without fentanyl provided analgesia without significant cardiorespiratory and guaranteed the minimal plasma levels with analgesic potential during the 8 h.

Effect of administering dexmedetomidine with or without atropine on cardiac troponin I level in isoflurane-anesthetized dogs

We aimed to determine whether dexmedetomidine administration with or without atropine increases cardiac troponin I (cTnI) level in healthy dogs. We hypothesized that 10 µg/kg dexmedetomidine + atropine increases the cTnI level, whereas 5 µg/kg dexmedetomidine + atropine does not. Eighteen healthy, pet dogs that underwent an orthopedic surgery or ovariohysterectomy were included in this study. The dogs were randomly assigned to atropine (0.02 mg/kg)–dexmedetomidine (10 µg/kg), saline–dexmedetomidine (10 µg/kg), and atropine (0.02 mg/kg)–dexmedetomidine (5 µg/kg) groups. Each dog was premedicated with atropine or saline intramuscularly (IM). After 10 min, they were IM injected with dexmedetomidine (10 or 5 µg/kg)–morphine (0.5 mg/kg)–midazolam (0.2 mg/kg). Following this, anesthesia was induced after 10 min with propofol and maintained with isoflurane in 100% oxygen. The median plasma cTnI level at 6, 12 and 24 hr after premedication was significantly higher than that at baseline. The cTnI level in the atropine–dexmedetomidine (10 µg/kg) group was significantly higher than that in the saline–dexmedetomidine (10 µg/kg) and atropine–dexmedetomidine (5 µg/kg) groups at 6 and 12 hr after premedication. The cTnI level returned to normal within 72 hr after premedication in all groups. The administration of atropine in combination with 10 µg/kg dexmedetomidine increased the cTnI level, indicating subclinical myocardial damage.

Branham sign in dogs undergoing interventional patent ductus arteriosus occlusion or surgical ligation: A retrospective study

Background:

The Branham sign is a baroreceptor response that follows patent ductus arteriosus (PDA) closure. Although described in dogs following both interventional and surgical ductal closure, a direct comparison of the Branham sign elicited by these two techniques has not been made.

Aim:

Since closure with an Amplatz canine ductal occluder (ACDO) occurs over 10 minutes and surgical ligation (SL) is more rapid, we hypothesized that the Branham sign following occlusion of a PDA with an ACDO would be less severe than following SL.

Methods:

Clinical records of dogs diagnosed with left-to-right shunting PDA between 2008 and 2018 were retrospectively reviewed. Of 139 dogs undergoing PDA occlusion, only 41 dogs (ACDO n = 32, SL n = 9) were included after applying exclusion criteria. Heart rate (HR) and blood pressure (BP) from occlusion time (T₀) until 30 minutes post occlusion (T₃₀) were recorded. Signalment and anesthetic protocol were also recorded. The influence of age and weight on the hemodynamic variations was assessed. Hemodynamic variables and calculations were compared between and within groups using a repeated measures general linear model, and post hoc tests were applied if significance was identified.

Results:

A mild Branham sign was present in both groups, and hemodynamic changes were not significantly different between groups. In both groups, there was a significant decrease in HR (11 bpm, 5.3–16.3; p < 0.001) (10.4%, 5.4–15.5; p < 0.001) and increase in diastolic BP (9.5 mmHg, 3–16; p = 0.002) (23.5%, 7.1–39.9; p = 0.002), but systolic BP did not change significantly (p = 0.824). Age and weight did not influence Branham sign.

Conclusion:

The Branham sign in dogs is mild in both groups, lasts for at least 30 minutes, and is independent of the method of PDA closure.

Clinical and pharmacokinetic interactions between oral fluconazole and intravenous ketamine and midazolam in dogs

OBJECTIVE

To evaluate drug interactions between fluconazole and the intravenous (IV) anesthetic induction agents, ketamine and midazolam.

STUDY DESIGN

Randomized parallel study.

ANIMALS

A group of 12 adult healthy Beagle dogs.

METHODS

Dogs were randomly allocated to two groups of six dogs. Dogs in group KM were administered IV ketamine (7 mg kg^-1) and IV midazolam (0.25 mg kg^-1), and dogs in group KMF were administered fluconazole (5 mg kg^-1) orally 12 and 24 hours prior to ketamine-midazolam using the same doses as KM. Sedation scores (0-4) were assigned by investigators unaware of group assignment. Heart rate (HR) and times to sternal and standing were obtained and compared between groups for differences with p < 0.05 considered statistically significant. Blood was obtained and plasma drug concentrations were measured using liquid chromatography-mass spectrometry.

RESULTS

The times to sternal, mean 32.3 and 24.6 minutes, for groups KMF and KM, respectively, were not different between the groups. The time to standing, 73 and 36 minutes in groups KMF and KM, respectively, was significantly different (p = 0.002). The duration of elevated HR compared with baseline was longer in KMF (110 minutes) than in KM (25 minutes) (p < 0.05). In group KMF, one dog developed hyperthermia (40.6 °C), which resolved spontaneously. The clearance of ketamine and midazolam was significantly slower (approximately 50%) and the area under the curves were significantly higher (two-fold) in group KMF (p = 0.02).

CONCLUSIONS AND CLINICAL RELEVANCE

A significant interaction between oral fluconazole and IV ketamine-midazolam occurred, but the effects appear minor in healthy dogs. Based on these data, a single dose of ketamine-midazolam is not contraindicated in dogs treated with fluconazole, but the duration of effects and pharmacokinetics are altered.