Good afternoon!

Pre-anesthetic considerations:
Recommend thoracic films before surgery to assess for congestive heart failure and potential pulmonary metastasis.
Non-invasive blood pressure measurements before surgery as this pet may be hypertensive from the mass involving the kidney and/or adrenal gland.
I would also recommend placing a second venous catheter in the event that excessive bleeding takes place during surgery given the proximity of the mass to the vena cava and renal artery.
Maintenance fluids before surgery with a balanced crystalloid.

Anesthetic plan:
Cerenia 1 mg/kg IV
Fentanyl 5 mcg/kg IV
Midazolam 0.3 mg/kg IV
Alfaxalone or propofol 4-6 mg/kg IV
***Preoxygenate 3-5 mins with 100% 02 before induction.

Anesthetic maintenance: Isoflurane or Sevoflurane

Pain management: Fentanyl constant rate infusion (CRI) 3-10 mcg/kg/hr during surgery

Fluid therapy: 3 mls/kg/hr with a balanced crystalloid. The total volume per hour should include the CRI. Judicious fluid boluses (5 mls/kg/hr) may be administered if excessive blood loss occurs during surgery.

For intraoperative hypotension: Dobutamine or dopamine CRI at 3-10 mcg/kg/min. Often times the patients will become hypotensive from surgical compression of the surrounding abdominal organs and caudal vena cava. I would allow the patient to be mildly hypotensive (MAP 50-60 mmHg) as it limits bleeding during the surgical removal of the kidney/mass. Also, if you begin aggressive blood pressure support with vasopressors you run the risk of having rebound hypertension once the surgeon takes pressure off of the abdominal organs and vena cava. Hypertension is definitely contraindicated with mitral valve disease thus mild hypotension is reasonable during the removal of the kidney/mass.

Postoperative pain management:
Continue fentanyl CRI at 3-5 mcg/kg/hr. NSAID administration is recommended post-operatively if the renal values remain stable and/or the patient is in acute pain. A PCV/TS and renal panel is recommended after surgery.