Pain Management
The physiology
Nociception has four steps: transduction, transmission, modulation, and perception. Central sensitization ("wind-up") explains why untreated acute pain becomes harder to control and why pre-emptive analgesia matters. Distinguish acute from chronic pain, somatic from visceral, and inflammatory from neuropathic pain, because the drug choices differ.
Assessment
Physiologic signs - heart rate, respiration, blood pressure, pupil size - are supportive but unreliable alone, especially in a sedated or fearful patient. Use validated composite pain scales (for example the Glasgow Composite Measure Pain Scale) and observe behaviour, posture, grooming, appetite, and interaction. A quiet patient is not necessarily a comfortable one.
Multimodal analgesia
Combine classes: opioids, NSAIDs, local anesthetics, and adjuncts (ketamine, gabapentin, lidocaine infusions). Pure opioid agonists (morphine, hydromorphone, fentanyl) suit severe pain; buprenorphine is a partial agonist; butorphanol is an agonist-antagonist with a ceiling effect and is a poor choice for severe pain. NSAIDs inhibit COX enzymes and carry GI and renal risk - never combine with corticosteroids or another NSAID, and use feline-specific dosing. Local anesthetics have maximum doses that must be calculated.
Worked example
A postoperative patient receiving an NSAID still scores high on a pain scale. Add an opioid and consider a local block rather than increasing the NSAID, which adds risk without addressing the mechanism.
Traps
Assuming cats do not feel pain, relying on a single drug class, and using butorphanol for moderate-to-severe pain.