What anesthetic protocols are safest for chelonians, and how do I calculate induction doses?

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Inhalant induction alone is contraindicated in chelonians — their dive reflex and ability to shunt blood away from pulmonary vessels in low-oxygen environments make gas-only induction unsafe; all protocols require injectable agents either preceding or combined with inhalants.1 Alfaxalone is the current injectable agent of choice, valued for its flexibility across routes (SC, IM, IV) and functions (premedication, induction, and maintenance as a single dose, multiple doses, or constant rate infusion).1 IV alfaxalone produces faster induction and shorter total anesthesia time compared to IM alfaxalone, though both routes provide safe, effective sedation.1 IV access can be difficult in small, dehydrated, or α-2 agonist-premedicated chelonians.1 For opioid analgesia, hydromorphone is the current opioid of choice in chelonians, providing effective antinociception without the side effects seen with morphine (prolonged respiratory depression and hyporexia).1 Butorphanol is not recommended due to questionable antinociceptive properties in chelonians.1 Tiletamine-zolazepam (TZ) produces moderate sedation in red-eared sliders (Trachemys scripta elegans) via the SC route regardless of injection site.2 Recovery times with TZ can be prolonged — in bearded dragons (Pogona vitticeps), mean recovery times range from 57 to 69 minutes, though this is a different species.2 All injectable drugs should be administered in the cranial half of the body. The renal portal system in chelonians means caudal-half injections risk altered pharmacokinetics and pharmacodynamics for nephrotoxic or renally excreted drugs.12 Cranial-half administration is recommended regardless of the practical advantage of reduced bite risk with caudal injections.2 Temperature directly governs drug clearance and recovery. Metabolic rate is already 10–30% of that in similarly sized mammals, and it slows further below the preferred optimum temperature zone — 26–38 °C for terrestrial species and 25–35 °C for aquatic or s