How should a sick rat be sedated? - briefly
Administer a short‑acting injectable anesthetic such as medetomidine combined with ketamine, or use inhalational isoflurane via a calibrated vaporizer, dosing according to the rat’s weight and health status. Continuously monitor respiration, heart rate, and temperature, and provide supportive oxygen and fluids as needed.
How should a sick rat be sedated? - in detail
Sedation of a diseased laboratory rat requires systematic evaluation, selection of appropriate agents, precise dosing, and continuous physiological monitoring.
Initial assessment includes measurement of body weight, temperature, heart rate, respiratory rate, and identification of organ dysfunction that could alter drug metabolism. Blood chemistry (glucose, electrolytes, renal and hepatic parameters) guides the choice of anesthetic regimen and predicts potential adverse effects.
Agent selection prioritizes agents with rapid onset, short duration, and minimal cardiovascular depression. Commonly employed combinations are:
- «ketamine» (dissociative anesthetic) paired with «xylazine» (α2‑adrenergic agonist) for balanced sedation and analgesia. Typical dose: 40–60 mg kg⁻¹ intraperitoneally for ketamine and 5–10 mg kg⁻¹ for xylazine.
- «midazolam» (benzodiazepine) combined with low‑dose «propofol» for deeper sedation without significant respiratory compromise. Recommended dose: 2–5 mg kg⁻¹ intraperitoneally for midazolam and 5–10 mg kg⁻¹ for propofol.
- «isoflurane» administered via a calibrated vaporizer for inhalational maintenance when prolonged procedures are anticipated. Induction concentration: 3–4 % in oxygen, maintenance at 1–2 %.
Administration route depends on the animal’s condition. Intraperitoneal injection is practical for short procedures and when venous access is limited. Intravenous delivery via tail vein provides rapid plasma levels and allows titration, useful in critically ill subjects. Inhalation requires a sealed chamber with scavenging to protect personnel.
Monitoring protocols encompass pulse oximetry, capnography, and rectal temperature. Supplemental oxygen (0.5–1 L min⁻¹) prevents hypoxemia, especially when using agents that depress respiration. Body temperature should be maintained within the normothermic range (36.5–38 °C) using a heating pad.
Recovery management includes cessation of anesthetic delivery, placement in a quiet environment, and observation until the rat regains sternal recumbency and exhibits normal gait. Analgesic support with non‑steroidal anti‑inflammatory drugs (e.g., «meloxicam» 1–2 mg kg⁻¹ subcutaneously) mitigates post‑procedural pain.
Contraindications: avoid high‑dose xylazine in rats with severe cardiac disease; limit ketamine in animals with elevated intracranial pressure; reduce propofol in hepatic insufficiency. Adjust doses proportionally to body weight and organ function to minimize toxicity.
Adherence to these guidelines ensures safe and effective sedation of ill rodents, facilitating experimental procedures while preserving animal welfare.