HOW TO REMOVE URETHRAL OBSTRUCTION IN CATS Urology Figure 3. Male cat with UO by urolithiasis. Left: X-ray where multiple uroliths are observed in the penile urethra. Right: Endoscopic images: by transvesical access, the urinary bladder trigone with uroliths of different shapes and sizes, and the urinary catheter that emerges from the urethral lumen; note inflammation and ulcers in the urinary mucosa due to the trauma generated by the uroliths. Figure 4. Male cat with UO. Up: X-ray image with non-presence of uroliths, which was confirmed by ultrasonography. Down: Decompressive cystocentesis in the same patient prior to urethral catheterization. Procedure for relief of UO The first step in the process of relieving the UO is to perform a decompressive cystocentesis to provide immediate relief to the severe distension, so reducing the risk of bladder necrosis and also to facilitate the retropulsion of any urethral plugs or uroliths and placement of a urethral catheter. In turn, this allows you to obtain a urine sample for urinalysis and urinary culture (4, 8) (Figure 4). pelvic and caudal nerves without causing loss – The article by Aguiñaga-Negrete et al. (2019) describes in detail the of motor function of the pelvic nerves (4) technique for correctly performing a cystocentesis. (Figure 5). Sedation, anesthesia and epidural blockage It is important to consider that trauma or urethral rupture can occur during the process of UO relief if the urethral catheterization is not properly carried out, so the use of general anesthesia or deep sedation is necessary, except in patients who are in a critical condition (9–11). Because of the severe condition that such patients may have, it is vitally important to place a vascular catheter as a gateway for fluid and emergency drug therapy, in addition to the monitoring of systems during the procedure and recovery. Different anesthetic protocols have been described in the literature that are useful for sedation or anesthesia of the feline UO patient. In our experience, the use of adrenergic alpha-2 receptor agonists such as dexmedetomidine (5–7 µg/kg IV), pure opiates such as fentanyl, or partial agonists such as buprenorphine (0.005–0.02 mg/kg IM or IV), which can be used in combination with a sedative such as midazolam (0.2–0.3 mg/kg IV), are of great use for sedation and favor the relaxation of the urethra. Sometimes the combination of intravenous anesthetics is necessary: phenols such as propofol at doses of 2–4 mg/kg IV, or dissociative anesthetics such as N-methyl-d-aspartame antagonists such as ketamine (2–5 mg/kg IV) or the use of inhaled anesthetics such as isoflurane or sevoflurane (12,13). Along with sedation, it is possible to use a sacrococcygeal epidural, which produces anesthesia in the perineum, penis, urethra, colon and anus by blocking the The epidural technique uses lidocaine, which generates regional blockade 5 minutes post administration, lasting up to 60 minutes. The use of 2% lidocaine is recommended without any mixture of drugs – for example, epinephrine – at a dose of 0.1–0.2 mL/kg, as it requires a low-volume injection and the effect can be achieved with a single dose. The technique of blocking has been described in different publications (14, 15) (Video 1). The risk of complications is relatively low, as the spinal cord ends at around the first sacral vertebra in cats, so the risk of penetrating the subarachnoid space is low. Possible complications include infection or abscess at the injection site and the possibility of systemic absorption of lidocaine, although the dosages described for this procedure are considerably lower than those recommended for intravenous administration (14,15); however, continuous monitoring of the patient is necessary. REMEVET 3
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