Combined hyponatremia and hyperkalemia mimicking acute hypoadrenocorticism in three pregnant dogs

HYPERKALEMIA IN FOUR ANESTHETIZED RED WOLVES (CANIS RUFUS)

Four clinically healthy red wolves (Canis rufus) developed hyperkalemia during routine anesthetic procedures. All cases were anesthetized using a combination of dexmedetomidine (10-24 mcg/kg), ketamine (2-3 mg/kg), and either midazolam (0.25-0.5 mg/kg) or butorphanol (0.2-0.48 mg/kg). Additional anesthetics were given to effect. Total anesthetic time ranged from 60 to 420 min. Three out of four cases were treated using terbutaline (0.01 mg/kg SC), which successfully resolved the hyperkalemia. No bradyarrhythmias were seen in any cases where electrocardiography (ECG) was monitored (3/4). All cases recovered from anesthesia, with one prolonged recovery. All animals are clinically healthy at the time of writing. Factors including anesthetic duration, the use of α-2 agonists, hyperthermia, and genetics are discussed as possible triggers for hyperkalemia. Serial blood gases, with electrolyte measurements, are recommended during anesthesia of red wolves, particularly when anesthetic time may be prolonged or the patient suffers from hyperthermia. Terbutaline appears to be a successful treatment should hyperkalemia arise.

Hyperkalemia during general anesthesia in two Greyhounds

CASE DESCRIPTION

A 36-kg (79-lb) castrated male Greyhound (dog 1) and a 25-kg (55 lb) spayed female Greyhound (dog 2) underwent general anesthesia for dental care with similar perianesthetic protocols on multiple occasions from 2013 to 2016. Both dogs had periodontal disease but were otherwise deemed healthy. Both dogs developed clinically relevant hyperkalemia, with signs including loss of P waves on ECG tracings, during multiple anesthetic events.

CLINICAL FINDINGS

Dog 1 developed hyperkalemia during 2 of 2 anesthetic events, with ECG changes noted during the first event. Dog 2 developed hyperkalemia during 3 of 4 anesthetic events, with ECG changes identified during the second and third events. Serum potassium concentration for both dogs was within the reference range prior to and between anesthetic events. No underlying etiopathogenesis for hyperkalemia was identified for either dog.

TREATMENT AND OUTCOME

In each hyperkalemic event, the clinician stopped the dental procedure and continued to provide supportive care and monitoring while the dog recovered from anesthesia. The ECG changes resolved, and serum potassium concentration returned to the reference range rapidly after inhalant anesthetic administration was discontinued. The dogs were discharged from the hospital without further complications.

CLINICAL RELEVANCE

Hyperkalemia in anesthetized Greyhounds resulted in serious cardiac conduction abnormalities, which could be potentially fatal if not recognized and promptly treated. Further investigation into the etiopathogenesis, prevention and treatment strategies, and genetic or familial components of this condition is indicated.

Recurrent Hyperkalemia During General Anesthesia in a Dog

Objective: To describe the development of recurrent hyperkalemia in a dog that underwent general anesthesia at two different hospitals within a month. The definitive underlying cause of the hyperkalemia remains unknown. Case summary: A 11 year-old male neutered Rottweiler underwent general anesthesia on two separate occasions at two different hospitals for ophthalmic surgery within a month and developed marked hyperkalemia on each occasion. The patient received similar drug protocols in both instances, including propofol, midazolam, non-depolarizing neuromuscular blocking agents, and isoflurane inhalant anesthetic. The patient showed ECG changes consistent with hyperkalemia during the first anesthetic event, but not the second. No underlying cause of hyperkalemia was definitively identified. The patient responded to standard therapy for hyperkalemia on both occasions and serum potassium levels returned to normal. The patient was discharged from the hospital without further complications and post-operative rechecks showed persistently normal serum potassium levels. New or unique information provided: Considering that there is a relationship between the development of severe hyperkalemia and propofol administration in human patients, it is possible that such a relationship exists in veterinary patients. However, numerous other diseases and medications can also lead to peri-operative hyperkalemia. Veterinary professionals should be aware that hyperkalemia can develop intra-operatively and remains be an important differential diagnosis in bradycardic patients under anesthesia that are not responding to traditional therapies.

Evaluation of the Cortisol-to-ACTH Ratio in Dogs with Hypoadrenocorticism, Dogs with Diseases Mimicking Hypoadrenocorticism and in Healthy Dogs

Background

The adrenocorticotropic hormone (ACTH) stimulation test is the gold standard for diagnosing hypoadrenocorticism (HA) in dogs. However, problems with the availability of synthetic ACTH (tetracosactrin/cosyntropin) and increased costs have prompted the need for alternative methods.

Objectives

To prospectively evaluate the cortisol‐to‐ACTH ratio (CAR) as a screening test for diagnosing canine HA.

Animals

Twenty three dogs with newly diagnosed HA; 79 dogs with diseases mimicking HA; 30 healthy dogs.

Methods

Plasma ACTH and baseline cortisol concentrations were measured before IV administration of 5 μg/kg ACTH in all dogs. CAR was calculated and the diagnostic performance of ACTH, baseline cortisol, CAR and sodium‐to‐potassium ratios (SPRs) was assessed based on receiver operating characteristics (ROC) curves calculating the area under the ROC curve.

Results

The CAR was significantly lower in dogs with HA compared to that in healthy dogs and in those with diseases mimicking HA (P < .0001). There was an overlap between HA dogs and those with HA mimicking diseases, but CAR still was the best parameter for diagnosing HA (ROC AUC 0.998), followed by the ACTH concentration (ROC AUC 0.97), baseline cortisol concentration (ROC AUC 0.96), and SPR (ROC AUC 0.86). With a CAR of >0.01 the diagnostic sensitivity and specificity were 100% and 99%, respectively.

Conclusion and Clinical Importance

Calculation of the CAR is a useful screening test for diagnosing primary HA. As a consequence of the observed overlap between the groups, however, misdiagnosis cannot be completely excluded. Moreover, additional studies are needed to evaluate the diagnostic reliability of CAR in more dogs with secondary HA.