Hemodynamics and bispectral index (BIS) of dogs anesthetized with midazolam and ketamine associated with medetomidine or dexmedetomidine and submitted to ovariohysterectomy

Abstract

PURPOSE: To evaluate hemodynamics and bispectral index (BIS) in bitches anesthetized with ketamine and midazolam in combination with dexmedetomidine or medetomidine and submitted to ovariohysterectomy. METHODS: Twenty bitches pretreated with levomedetomidine and buprenorphine were anesthetized with 5 mg.kg-1 ketamine and 0.2 mg.kg-1 midazolam i.v. Continuous infusion of 0.4 mg.kg-1.h-1 midazolam and 20 mg.kg-1.h-1 ketamine was initiated in combination with DEX (n=10): 20 µg.kg-1.h-1 dexmedetomidine or MED (n=10): 30 µg.kg-1.h-1 medetomidine over 30 minutes. A pharmacokinetic study provided dexmedetomidine plasma concentration, set to be 3.0 ng.mL-1. RESULTS: BIS decreased in both groups (P<0.05), but it was lower in DEX (P<0.05) as compared to MED. No differences were found in hemodynamic parameters (heart rate, systolic, diastolic and mean arterial pressure) between groups (P>0.05), but heart rate decreased in both groups, as compared to control values (P<0.05). Respiratory rate decreased (P<0.05) and expired end tidal CO2 increased progressively (P<0.05) and similarly in both groups. Anesthetic recovery period was similar between groups (P<0.05) with no adverse effects. CONCLUSION: Continuous administration of dexmedetomidine with calculated plasma concentration equal to 3 ng.mL-1 in combination with midazolam and ketamine provides suitable anesthesia for spay surgery in bitches, hemodynamic stability and calm awakening with no adverse effects.

Effect of dexmedetomidine constant rate infusion on the bispectral index during alfaxalone anaesthesia in dogs

“…However, our CRI doses (0.5 and 1 μg kg −1 hour −1 for groups D1 and D2, respectively) were lower than those reported by Silva Fdo et al. () (20 μg kg −1 hour −1 ), who reported a considerable and continuous decrease of the BIS and EMG in dogs subjected to ovariohysterectomy and anaesthetized with midazolam and ketamine. van Oostrom et al.…”

“…Silva Fdo et al. () reported a considerable decrease in EMG activity in dogs after the administration of medetomidine or dexmedetomidine. There were similar findings in our study in the D2 group, where the values were significantly lower than in groups D0 and D1.…”

Pharmacokinetics of ketamine and three metabolites in Beagle dogs under sevoflurane vs. medetomidine comedication assessed by enantioselective capillary electrophoresis

“…It is used for sedation or as an adjuvant in anesthesia. Only the S-enantiomer dexmedetomidine is pharmacologically active [1][2][3][4]13]. Both enantiomers are able to inhibit cytochrome P450 (CYP) enzymes whereas levomedetomidine is the stronger inhibitor [1,3,4].…”

Evaluation of the cardiorespiratory effects of the alpha-2 adrenoceptor agonists xylazine, medetomidine and dexmedetomidine in combination with ketamine in dogs

“…All α 2 -agonists decrease the rate of respiration, which does not cause an increase in the partial pressure of carbon dioxide (PaCO 2 ) in arterial blood (Lee 2011;Lamont et al 2012;Lee et al 2015;Restitutti et al 2017) but may reduce the respiratory response to hypercapnia (Cardoso et al 2014). Furthermore, α 2 -agonists contribute to an insignificant decrease in body temperature (Sinclair 2003;Carter et al 2010;Silva et al 2010).…”

“…administration of medetomidine results in more pronounced cardiovascular effects than those that manifest following administration through the intramuscular (i.m.) route (Silva et al 2010).…”