Anesthetizing a 12-Year-Old Cat With IRIS Stage 2 Kidney Disease
Mochi is a 12-year-old spayed female domestic shorthair cat weighing 3.6 kg with a body condition score of 3/9, scheduled for full-mouth dental scaling and possible extractions. The owner reports six months of gradual weight loss, intermittent vomiting, and increasingly bad breath. Pre-anesthetic bloodwork shows BUN 42 mg/dL, creatinine 2.4 mg/dL, SDMA 22 micrograms/dL, urine specific gravity 1.018, PCV 34%, total protein 7.6 g/dL, potassium 3.6 mmol/L, sodium 152 mmol/L, and glucose 128 mg/dL. Awake Doppler blood pressure is 168 mmHg systolic. Auscultation reveals a grade I/II left parasternal systolic murmur with a gallop rhythm; Mochi is bright, well hydrated, and has no arrhythmia. On oral examination there is marked calculus, gingival recession on both maxillary fourth premolars, and a mobile right mandibular canine. The veterinarian asks you to draft the anesthesia and monitoring plan for review before any drugs are drawn up. A second cat is scheduled 45 minutes from now and the team is moving quickly.
1. Propose a premedication and induction plan for Mochi and explain which drugs you would limit or avoid, with your reasoning.
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Guiding principles: this cat has reduced renal reserve, a small body mass with little thermal buffer, a murmur with a gallop (suggesting impaired diastolic filling, not just a benign flow murmur), and hypertension. The plan should minimize cardiovascular depression, preserve renal perfusion, and keep the total drug burden low so recovery is rapid.
Premedication: opioid-based. An opioid such as buprenorphine or methadone provides analgesia without vasodilation or myocardial depression, with or without a low-dose benzodiazepine (midazolam) for anxiolysis and muscle relaxation. This combination is my preference.
Limit or avoid:
- Acepromazine: alpha-1 blockade produces vasodilation and hypotension, and this cat has hypertension and borderline renal perfusion. Avoid.
- High-dose alpha-2 agonists: predictable vasoconstriction and bradycardia that reduce renal blood flow and increase afterload. If used at all, only a microdose with a specific reason.
- Ketamine: it is metabolized partly by the kidney, and although it is not absolutely contraindicated in stable chronic kidney disease, I would not choose it here when alternatives that don't depend on renal clearance exist.
- NSAIDs for analgesia: avoid perioperatively given azotemia, hypertension, and questionable hydration status until the veterinarian and renal values say otherwise.
Induction: alfaxalone titrated intravenously to effect (or propofol titrated slowly), never a mask induction, then intubation and maintenance with isoflurane or sevoflurane in oxygen, vaporizer adjusted to effect. Give intraoperative balanced crystalloid at roughly 3 mL/kg/hr unless the veterinarian specifies otherwise.
2. Describe the monitoring you would perform and the specific values at which you would intervene. How would you manage hypotension in this cat?
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Monitors and observations, at minimum: heart rate and rhythm on ECG, respiratory rate and pattern, pulse oximetry, capnography, Doppler or oscillometric blood pressure every 5 minutes, temperature every 15 minutes, mucous membrane color and CRT, esophageal or rectal temperature, surgical blood loss estimated by weighing sponges, and urine output if a collection system is in place.
Intervention thresholds:
- Systolic blood pressure below 90 mmHg, or mean arterial pressure below 60 mmHg.
- Heart rate more than 20% above or below the baseline established after induction, or a new arrhythmia.
- SpO2 below 95%, or end-tidal CO2 outside roughly 35 to 45 mmHg.
- Temperature below 98 F (36.7 C), which in a 3.6 kg cat happens fast.
Stepwise management of hypotension:
- Recheck the reading and confirm with a second method or a repeat measurement before acting.
- Assess anesthetic depth and reduce the vaporizer or give a light plane adjustment; many hypotensive episodes are simple anesthetic overdose.
- Check for surgical stimulation and provide analgesia or a local block rather than deepening the anesthetic.
- Give a crystalloid bolus as directed (for example 5 to 10 mL/kg over 10 to 15 minutes) while watching respiratory rate and lung sounds for volume overload.
- Look for blood loss, a kinked endotracheal tube, or a pneumoperitoneum; correct the cause rather than only the number.
- If refractory, prepare vasopressor support such as dopamine or norepinephrine as ordered, with the veterinarian at the table.
3. What recovery concerns are specific to Mochi, and what postoperative analgesia plan would you propose to avoid further renal insult?
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Recovery concerns:
- Hypothermia: low body condition score, small body mass, and open-mouth procedures all accelerate heat loss. Use forced-air warming, warm the IV fluids, limit body cavity exposure time, and continue active warming into recovery with a temperature probe rather than touch.
- Prolonged or rough recovery: impaired renal clearance and a lower lean body mass mean drug effects last longer. Extubate only when swallowing is present, and stay with her through the transition.
- Dehydration and delayed return to eating: keep intravenous fluids running postoperatively until she is drinking and eating on her own, and offer water and a small amount of palatable food early.
- Hypertension and the murmur: continue her cardiac medications as directed, keep stress low, and recheck blood pressure during recovery.
- Masked pain: cats hide it. Use a validated feline pain scale and look at behavior, facial expression, posture, and willingness to eat.
Analgesia plan:
- Multimodal, opioid-centered: buprenorphine (approximately 0.01 to 0.02 mg/kg IV or IM q6 to 8h) or another opioid, plus local anesthesia.
- Local blocks: mandibular and maxillary nerve blocks with bupivacaine, keeping the total dose within 2 mg/kg across all blocks, so systemic opioid requirements drop.
- Adjuncts: gabapentin can be used for chronic oral pain.
- NSAIDs: avoid during the perioperative period with azotemia and hypertension. If the veterinarian later wants one, it should only be after rehydration, documented stable renal values, and normal blood pressure, and with a discussion with the owner.