Case study: Cardiopulmonary arrest in a cat with urethral obstruction

feline urethral obstruction
Anubis, the cat, recovering from his surgery. A urethral obstruction led to cardiopulmonary arrest, but quick intervention led to a happy outcome for both cat and owner.

Anubis is a six-year-old MN domestic short hair who presented to Northside Emergency Veterinary Service with a one-week history of vomiting and not moving during the day. His owner brought him after he was found collapsed on the bed. He lived indoors—with three other cats—with access to a balcony. He had not had any previous health issues.

On arrival he was laterally recumbent and minimally responsive. His temperature was found to be off-scale low. Flow by oxygen was started and while an intravenous catheter was being placed, it was noticed that he become apnoeic which quickly progressed to cardiopulmonary arrest (CPA). Cardiopulmonary resuscitation (CPR) was started with chest compressions at 100-120 BPM using the cardiac pump technique and a timer was started. He was intubated and intermittent positive pressure ventilation (IPPV) was started at 10 breaths per minute using an ambubag and oxygen. A capnograph was attached between the ET tube and the ambubag but unfortunately did not work during the duration of the resuscitation. An ECG was also placed and a full two-minute round of CPR was performed. 

The cause of his arrest was found to be due to urethral obstruction as a large turgid, non-expressible, bladder was found on abdominal palpation. Due to the likelihood of hyperkalaemia being the cause of the arrest, Anubis was given 1ml/kg of Calcium gluconate (0.22mmol/kg) IV to restore the gap between resting membrane potential and threshold potential to allow cardiac myocyte depolarisation.

He was given a 0.01mg/kg (low dose) adrenaline and 0.04mg/kg atropine IV during the second round of CPR. Ideally this would have been given earlier but problems with his ET tube delayed it. Low dose adrenaline was repeated at the end of the fourth round. 

He underwent four full rounds of CPR with no heartbeat and pulseless electrical activity (PEA) diagnosed on ECG at the end of each round, however a heartbeat started to be felt midway through the fifth round. At the end of this round, CPR was stopped due to return of spontaneous circulation (ROSC).

He was then given 2IU Actrapid followed by 4g glucose (50%) diluted, intravenously, to drive potassium intracellularly. He was also given a 10ml/kg Hartmanns bolus over 15 minutes.

IPPV was continued for approximately 10 minutes until he was ventilating spontaneously. He was then unblocked while still unconscious, and found to have a large urethral plug at the tip of his penis and a gritty obstruction approximately 1cm into the penis. An indwelling 3.5FR 14cm Slippery Sam urethral catheter was placed and connected to a close collection system. 

A venous blood gas was run on a blood sample which had been taken from his IV catheter when it was placed showed a pH 6.91 (7.24-7.40), HCO3 7.9 (22-24 mmol/l), pCO2 42 (34-38), sodium 144 (150-165 mmol/l), potassium off scale high (3.5-5.8mmol/l), chloride 113 (112-129 mmol/l) confirming severe metabolic acidosis and hyperkalaemia.

He was given a further 10ml/kg Hartmanns bolus over 30mins, had a nasal O2 catheter placed and was extubated approximately 30mins after ROSC when he was swallowing.

A fresh blood sample was then taken and showed a mild improvement in his pH (6.95) and a readable potassium of 9.2mmol/l. He was also found to be severely azotaemic with urea 81.9 (5.7-12.9mmol/l), creatinine of 1090 (71-212 umol/l) and phosphorus of 3.42 (1-2.42 mmol/l). An AFAST was performed and did not find any free abdominal fluid or echogenic stones. 

Although he was not hypoxaemic, he was placed on unilateral nasal oxygen for support, along with continuous ECG, pulse oximetry and blood pressure monitoring and hourly temperature and blood glucose checks. 

Due to his severe azotaemia he was expected to have severe post obstructive diuresis so was placed on a two-bag (maintenance and replacement) fluid plan of IV fluid rate matching urine output plus insensible losses (1ml/kg/hr) with adjustment every four hours when the urine output was measured. Both bags were Hartmanns with glucose added to the maintenance bag to make 2.5%, to continue to drive potassium intracellularly. 

As per the RECOVER guidelines, although his post arrest temperature was 32.4°C, he was not initially actively warmed. This is due to the potentially neuroprotective effect that hypothermia can have post arrest. Ideally temperature should be increased at 0.25-0.5C/hr and no faster than 1C/hr. His temperature took approximately 12hrs to normalise with initially just a blanket, then warm packs.

Over the next 24hrs his mentation improved but he was found to be centrally blind. This is common after CPA due to cerebral hypoxaemia and normally resolves within two weeks. Surprisingly he did not develop significant post obstructive diuresis. He was weaned off oxygen and his potassium had almost normalised to 5.1mmol/l within 6hrs and his azotaemia resolved within 24hrs. 

He was discharged 48 hours post presentation on buccal Buprenorphine 0.02mg/kg q 8-12hrs and Prazosin 0.5mg PO q 12hrs. He was still blind at discharge but this is likely to resolve.

The RECOVER Guidelines state that the average chance of survival to discharge across all CPAs is as low as 6%, however the prognosis varies greatly depending on the cause of the arrest. Rapidly reversible situations such as hyperkalaemia and Gastric Dilation Volvulus (GDV) have a significantly higher chance of survival with peri anaesthetic arrests having a 45-50% survival rate when good quality CPR is instigated rapidly.

Dr Lucy Kirton BVetMed MANZCVS (VetECC) MRCVS, Emergency veterinarian

feline urethral obstruction

Dr Kirton graduated from the Royal Veterinary College, London in 2004. She worked initially in mixed practice but quickly moved into small animal general practice. She came to Australia in 2011, quickly settling in Sydney. 

Having developed an interest when working on Sydney’s Northern Beaches, providing critical care to tick paralysis patients, she began working in emergency practice in 2013, initially at the Small Animal Specialist Hospital (SASH), and then Northside Emergency Veterinary Service (NEVS) in 2016.

She passed her ANZCVS memberships in Emergency and Critical Care in 2014 and was a membership examiner in 2017 and 2018. She has a particular interest in critical care, ventilation, cardiopulmonary resuscitation (CPR) and training. She became a RECOVER CPR trainer in 2017 and is a director in FlexiVet Training Pty Ltd which offers small animal emergency and CPR training.

Dr Kirton lives in the Sydney Hills District with her partner and stepdaughter. In her spare time, she enjoys sailing and yoga. 


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