Effects of Sedation with Medetomidine and Dexmedetomidine on Doppler Measurements of Ovarian Artery Blood Flow in Bitches

SIMPLE SUMMARY: Alpha-2 agonists have widely been used in dogs as sedative and preanesthetic agents. These drugs have successfully been used in many different reproductive surgical procedures in dogs, including ovariectomy (OV) and ovariohysterectomy (OVH). The main problem associated with the alpha-2 agonists’ use is their dose-dependent cardiovascular effects and the changes induced on organ perfusion. Nowadays, the use of Doppler ultrasonography is the most commonly used method to assess physiological and pathological organ perfusion in veterinary medicine as it is a noninvasive technique. In bitches, Doppler ultrasonography has shown its usefulness to assess placental, ovarian and uterine blood flow during normal and abnormal pregnancy. We compared the ovarian artery flow velocity by duplex Doppler ultrasound before and after sedation with two commonly used alpha-2 agonists: medetomidine and dexmedetomidine. The results showed that the administration of medetomidine or dexmedetomidine induced an important decrease in blood flow velocities in the ovarian artery. Hence, their use could be indicated in surgeries to avoid excessive bleeding of the ovarian pedicle. ABSTRACT: The aim was to evaluate if medetomidine and dexmedetomidine affected arterial ovarian blood flow in dogs. The dogs were randomly assigned to two different groups. In Group 1, medetomidine (10 µg/kg) was administered intramuscularly and, in Group 2, dexmedetomidine (5 µg/kg) was used. After a preliminary exam, arterial blood pressure (BP) was measured and a duplex Doppler ultrasonographic examination of both ovarian arteries was performed. Twenty minutes after the administration of medetomidine or dexmedetomidine, BP and ovarian Doppler ultrasonography were repeated. High quality tracings of ovarian artery flow velocity were obtained in all dogs and Doppler parameters: Peak Systolic Velocity (PSV), End Diastolic Velocity (EDV) and Resistive Index (RI) were measured before and after drug administration in the left (LO) and right (RO) ovaries. PSV and EDV values decreased significantly after drug administration (p < 0.05) compared to the non-sedated values, but no differences were found between the LO and RO (p > 0.05). The RI was not affected by drugs administration in neither of the groups studied (p > 0.05). In conclusion, the administration of medetomidine or dexmedetomidine causes a decrease in blood flow velocity in the ovarian artery and may be a good choice to avoid excessive bleeding prior surgeries in which ovariectomy.