Similar to the kidney donor, anesthetic and analgesic agents must be chosen according to the individual patient’s physiologic status and signalment as each transplant patient is unique; there is no universal protocol that can be used for every patient. Preoperative medication using a combination of the μ‐opioid receptor agonist, fentanyl, and a benzodiazepine is common since neither fentanyl nor the benzodiazepine class of drugs substantially affects cardiovascular function at clinically acceptable doses (Table 44.1) [34–37]. For example, fentanyl or a fentanyl analog (including sufentanil, alfentanil, and remifentanil) and midazolam are commonly used intravenously to facilitate anesthetic induction, provide analgesia, and reduce the stress response to surgery. Fentanyl is also advantageous since it has a relatively short duration of action, which facilitates rapid adjustments, does not release histamine, and is minimally excreted (< 10%) unchanged by the kidneys [38–40]. Although other opioids, such as hydromorphone, may be acceptable for use as analgesics, systemic morphine is not recommended. Systemic morphine administration increases plasma histamine levels, which can be associated with systemic hypotension [38]. In addition, morphine‐6‐glucuronide is an active metabolic product of morphine in dogs and humans, and delayed elimination of this metabolite in patients with renal insufficiency may prolong drug effects [41–45]. Although cats have low levels of glucuronyl transferase and morphine undergoes a different type of conjugation reaction in this species, the pharmacokinetics of morphine are somewhat similar to those of dogs and humans, but clearance rates may be slightly slower [46–48]. Hence, systemic morphine administration in feline kidney recipients is not routinely recommended when other opioids are available. Similarly, α₂‐adrenergic receptor agonists, such as dexmedetomidine, should be avoided as they reduce cardiac output with increases in systemic vascular resistance [21–26]. Phenothiazines are also not recommended as a routine premedication in recipients since administration can reduce systemic vascular resistance and potentially decrease arterial blood pressure in dogs and cats via peripheral α‐adrenergic receptor blockade [20,49,50].

Anesthetic induction can be accomplished with slow administration of small doses of propofol as it is rapidly metabolized by both hepatic and extra‐hepatic means and RBF and GFR are minimally affected (Table 44.1) [51,52]. Although the effects of alfaxalone on RBF and GFR are not specifically reported in cats, small boluses of alfaxalone may also be used since postinduction cardiovascular effects appear similar to those of propofol (for review, see [53]). Although significantly metabolized in the liver, ketamine is usually avoided since its active metabolite, norketamine, is excreted unchanged by the kidney [54] and may contribute to prolonged drug effects in animals with decreased renal function. If ketamine is required as a premedication or induction agent (for example, due to animal behavior or lack of an alternative), doses should be reduced as much as possible by combination with appropriate coinduction agents. Etomidate may be used but is not commonly recommended since, although it has minimal cardiovascular effects, it induces transient adrenal suppression, which has been associated with increased postoperative mortality in critically ill humans [55,56]. Etomidate’s effect on postoperative mortality in compromised cats is unknown.

During anesthetic maintenance (Table 44.1), most inhalant anesthetics reduce GFR (isoflurane, sevoflurane, and desflurane), and attempts to reduce levels and maintain systemic blood pressure should be made [52,57]. Therefore, it is common to use a constant rate infusion of fentanyl or another fentanyl analog throughout the surgical procedure to reduce inhalant levels and enhance antinociception [58–60]. In addition, an epidural containing preservative‐free morphine may be used; addition of local anesthetics to the epidural is usually avoided to reduce any further hypotension from profound decreases in vascular resistance due to sympathetic nervous system blockade. Following such epidural techniques, cats should be closely monitored for associated hypotension. Although there have been concerns that sevoflurane may not be safe for use in AKI or CKD due to the production of potentially nephrotoxic compound A (in rodents) and inorganic fluoride, no adverse effects have been shown in clinical patients and sevoflurane can be used in these patients, as can isoflurane and desflurane [57,61–63].

Intraoperative anesthetic monitoring is essential for the risk management of renal transplant patients. For example, intraoperative hypoxemia is associated with reduced overall survival rates [13]. Thus, monitoring includes pulse oximetry, capnometry, inhalant agent levels, electrocardiography, and core body temperature. In addition, intraoperative hemodynamic monitoring and management are imperative to ensure reasonable organ perfusion pressure, yet not subject the patient to fluid overload. Although CVP does not always correlate well with the patient’s overall fluid status, acute CVP changes may indicate impending fluid overload. However, this relationship is still debated [64]. Pulse pressure variation or pleth variability index may be better indices of fluid status in the mechanically ventilated patient, although their usefulness in cats have not been fully investigated [65]. Invasive blood pressure should be closely monitored since patients may experience normo‐, hypo‐, or hypertension throughout the procedure and into the postoperative period. An arterial catheter should be placed in the dorsal pedal or femoral artery; however, the descending aorta or its major branches may be occluded during renal artery anastomosis, and the signal will be lost during this period. The coccygeal artery may be used but can be difficult to keep clean postoperatively, which may negate its use in an immunosuppressed patient. Care in handling these catheters is essential as patients may be purposely heparinized and excessive bleeding at the puncture site may occur. Indirect blood pressure measurement using an ultrasonic Doppler flow detector or oscillometric technique applied to the front limb should be performed concurrently with invasive monitoring as these indirect techniques can be used during aortic occlusion and/or if an artery cannot be catheterized; however, they can be less accurate depending on circumstances [66–70].

Intravenous fluid therapy in human transplant surgeries has recently been addressed [71]. Large crystalloid volumes are not recommended, but accelerated fluid administration during the initial period of graft ischemia may improve subsequent kidney function. Thus, feline fluid rates of 3–5 mL/kg/h based on the individual patient’s needs and comorbidities (e.g., heart disease) with small, accelerated (3–5 mL/kg) fluid boluses over approximately 15 min as needed during ischemia are recommended. These guidelines also suggest that a balanced electrolyte solution should be used; 0.9% sodium chloride is not recommended due to extracellular shifts in serum potassium, increases in serum chloride, and a decrease in pH (hyperchloremic acidosis) [71–74]. In fact, hyperkalemia does not worsen with balanced solutions, and 0.9% sodium chloride can actually result in significant metabolic disorders [71–74]. Synthetic colloids such as hydroxyethyl starches should not be used due to potential adverse effects such as coagulopathies, reticuloendothelial system dysfunction, and delayed or impaired renal function [71,75].

If patients are normovolemic during surgery, yet remain hypotensive under general anesthesia, β‐adrenergic receptor agonists, such as dobutamine, can be used to increase cardiac output. The use of dopamine remains controversial because of species differences in receptor pharmacology and potential increases in systemic vascular resistance with higher doses [45]. If the patient cannot tolerate further fluid loading, titrated vasopressors, such as norepinephrine, may be considered to treat hypotension, despite the risk of renal vasoconstriction. In humans, norepinephrine use does not have a negative effect on recipient graft function since the harmful effects of systemic hypotension likely outweigh the potential renal vasoconstriction caused by norepinephrine [76,77]. However, this has yet to be tested in clinical veterinary transplant patients.

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