The objective of this study was to determine if BCS influences the sedative effect of IM premedication or the dose of IV propofol needed for intubation in dogs. For IV dosing of lipid-soluble medications (eg, propofol), dose based on lean body mass may be more appropriate, whereas calculation according to actual body mass may be preferred for IM medications.
Dogs were allocated into a normal-weight group (NG; BCS 4–5; n = 25) or overweight group (OG; BCS >6; n = 21). Dogs received an IM injection of medetomidine (5 µg/kg) and butorphanol (0.2 mg/kg), calculated on actual body weight and were sedation-scored before injection and 20 minutes later. The degree of sedation after IM premedication was not different between the groups.
Anesthesia was induced by IV infusion of propofol (1.5 mg/kg/min). The infusion was stopped when there was near-ablation or loss of palpebral reflexes, loss of jaw tone, and no or minimal gagging such that endotracheal intubation was achievable.
Mean propofol doses were 2.24 mg/kg for NG dogs and 1.83 mg/kg for OG dogs. Although BCS does not affect sedation levels from IM dosing of α2-agonists and opioids, overweight and obese dogs have lower dose requirements for IV propofol.