Feline procedural sedation and analgesia: When, why and how

Abstract

Practical relevance: Procedural sedation and analgesia (PSA) describes the process of depressing a patient's conscious state to perform unpleasant, minimally invasive procedures, and is part of the daily routine in feline medicine. Maintaining cardiopulmonary stability is critical while peforming PSA.

Clinical challenges: Decision-making with respect to drug choice and dosage regimen, taking into consideration the cat's health status, behavior, any concomitant diseases and the need for analgesia, represents an everyday challenge in feline practice. While PSA is commonly perceived to be an uneventful procedure, complications may arise, especially when cats that were meant to be sedated are actually anesthetized.

Aims: This clinical article reviews key aspects of PSA in cats while exploring the literature and discussing complications and risk factors. Recommendations are given for patient assessment and preparation, clinical monitoring and fasting protocols, and there is discussion of how PSA protocols may change blood results and diagnostic tests. An overview of, and rationale for, building a PSA protocol, and the advantages and disadvantages of different classes of sedatives and anesthetics, is presented in a clinical context. Finally, injectable drug protocols are reported, supported by an evidence-based approach and clinical experience.

Keywords: Acepromazine; agonists of α2-receptors; alfaxalone; benzodiazepines; chemical restraint; ketamine; sedation.

Figure 1

Primary causes of sedation- and anesthesia-related deaths in cats. From Brodbelt et al (2008)

Figure 2

Feline-friendly handling techniques should be used throughout procedural sedation and analgesia (PSA) to minimize stress and fear and provide a good hospital experience. The mantras ‘less is more’ and ‘go slow to go fast’ are true during feline handling. Towels can be used around the neck and body for physical restraint and gentle care, and to avoid scruffing. An Elizabethan collar will provide additional protection for the handler from aggressive cats. This particular patient is safely restrained for a procedure such as intramuscular injection or intravenous catheter placement

Figure 3

Cats may be examined and handled in top-opening or side-opening carriers to facilitate the procedure and maximize comfort during veterinary consultations

Figure 4

Supplies prepared in advance of PSA, in case intubation of the cat’s trachea is required. a = cuffed endotracheal tube; b = cuff inflation syringe; c = lidocaine with a syringe and catheter for topical application on the arytenoids to prevent laryngospasm during intubation; d = topical eye lubrication; e = sterile endotracheal tube lubrication; f = roll gauze for securing the endotracheal tube in place; g = mask for oxygen supplementation; h = square gauze to help grasp the patient’s tongue during intubation; i = laryngoscope; j = stylet for placement within the endotracheal tube; the stylet should be introduced only as far as 3–5 cm past the arytenoids, and is removed once the endotracheal tube is in place, taking care not to cause pharyngeal or tracheal trauma; k = manual resuscitation bag and attachment for oxygen insufflation. Note: A Mapleson D (Bain) non-rebreathing circuit attached to an anesthetic machine may be used in lieu of a manual resuscitation bag at flow rates of 150–300 ml/kg/min

Figure 5

Oral transmucosal (buccal) administration of dexmedetomidine and buprenorphine can provide 'hands-off' sedation, analgesia and chemical restraint. Palatability is generally acceptable. Drug absorption is by the transmucosal route, assuming the drug is not spilled or swallowed by the cat

Figure 6

Capnography (performed using a side-stream adapter), pulse oximetry and cardiac auscultation in a cat undergoing procedural sedation and analgesia for an abdominal ultrasound examination. Courtesy of Mary T Schacher