Disorders of potassium homeostasis

Treatment strategies for hyperkalemia secondary to urethral obstruction in 50 male cats: 2002-2017

OBJECTIVES

The aims of this study were: to describe the potassium-lowering treatment strategies used to manage moderate-to-severe hyperkalemia in male cats with urethral obstruction (UO); to determine how much dextrose was required per unit of insulin to prevent hypoglycemia; to determine whether early initiation of a dextrose continuous rate infusion (CRI) prevented hypoglycemia; and to determine whether in-hospital mortality was associated with presenting plasma potassium concentration ([K⁺]).

METHODS

The medical records of male cats presenting with a [K⁺] ⩾7.0 mEq/l due to UO that had another [K⁺] measured within 6 h were reviewed retrospectively. All [K⁺] values within the first 6 h, blood glucose concentrations, treatments for hyperkalemia and survival to discharge were recorded. Analyses were performed to test for associations between dextrose:insulin ratios or method of dextrose administration and the development of hypoglycemia; and for presenting [K⁺] and mortality. Normally distributed groups of continuous data were compared with a t-test and categorical data were compared with a Fisher's exact test.

RESULTS

Fifty cats were included. Mean presenting [K⁺] was 8.9 ± 1.0 mEq/l, while the mean final [K⁺] within 6 h was 6.6 ± 1.4 mEq/l. Forty-two (84%) cats were treated with intravenous fluids and 40 (80%) were treated with dextrose and insulin. Median dextrose:insulin ratio was 2 g/u (range 0.4-100). No dextrose:insulin ratio was found to protect against hypoglycemia, and 3/8 cats that became hypoglycemic had received ⩾2 g dextrose per unit of insulin. There was no association between the early initiation of a dextrose-containing CRI and avoidance of hypoglycemia. No association was found between presenting [K⁺] and mortality.

CONCLUSIONS AND RELEVANCE

While no specific dextrose:insulin ratio was found to protect against hypoglycemia, there is evidence that the commonly recommended dextrose:insulin ratio of 2 g/u may be inadequate in preventing hypoglycemia in every cat. Severity of hyperkalemia was not associated with mortality.

Renal and cardiorespiratory effects of treatment with lactated Ringer's solution or physiologic saline (0.9% NaCl) solution in cats with experimentally induced urethral obstruction

OBJECTIVE

To compare the renal and cardiorespiratory effects of IV treatment with lactated Ringer's solution (LRS) or physiologic saline (0.9% NaCl) solution (PSS) in severely decompensated cats with urethral obstruction (UO).

ANIMALS

14 cats (4 cats were used only to establish infusion rates).

PROCEDURES

An occluded urethral catheter was used to induce UO in each cat. After development of severe metabolic acidosis, hyperkalemia, and postrenal azotemia, the obstruction was relieved (0 hours); LRS or PSS (5 cats/group) was administered IV (gradually decreasing rate) beginning 15 minutes before and continuing for 48 hours after UO relief. Ten minutes before urethral catheter placement (baseline), at start of fluid therapy (SFT), and at intervals during fluid administration, various physical and clinicopathologic evaluations were performed.

RESULTS

Metabolic acidosis was detected in the PSS-treated group at SFT and 2 hours after relief of UO and in the LRS-treated group only at SFT The PSS-treated group had significantly lower blood pH and bicarbonate concentrations at 8 through 48 hours and lower base excess values at 2 through 48 hours, compared with the LRS-treated group. Hypocalcemia and hypernatremia were detected in the PSS-treated group at 2 and 12 hours, respectively. Absolute serum potassium and chloride concentrations did not differ significantly between groups at any time point.

CONCLUSIONS AND CLINICAL RELEVANCE

Treatment with LRS or PSS appeared to be safe and effective in cats with experimentally induced UO; however, LRS was more efficient in restoring the acid-base and electrolyte balance in severely decompensated cats with UO.

Therapeutic approach to chronic electrolyte disorders

Chronic disorders of sodium and potassium occur and occasionally need symptomatic therapy. Hypernatremia primarily indicates loss of free water, whereas hyponatremia may be attributable to various problems. It is important not to correct major aberrations of serum sodium concentrations too quickly lest the therapy be more detrimental than the electrolyte abnormality. In distinction, hypokalemia and hyperkalemia may be corrected quickly. Hypomagnesemia is relatively common, but its clinical significance is still being determined.

Diagnosis and treatment of naturally occurring hypoadrenocorticism in 42 dogs

Hypoadrenocorticism was diagnosed in 42 dogs over a two-and-a-half-year period. The disease occurred more commonly in young to middle-aged dogs, with a female:male ratio of 2:1. Most dogs had chronic intermittent signs (eg, poor appetite, lethargy and vomiting), but more than a third were in acute adrenal crisis at the time of diagnosis. Serum biochemical testing revealed azotaemia, hyperphosphataemia, hyperkalaemia and hyponatraemia in almost all the dogs. In all dogs, results of adrenocorticotrophic hormone (ACTH) stimulation testing revealed a low to low-normal serum baseline cortisol concentration that failed to increase after ACTH administration. In two dogs with persistently normal serum electrolytes concentration, one had a markedly high plasma ACTH concentration diagnostic for primary hypoadrenocorticism, whereas the other had a low concentration confirming secondary hypoadrenocorticism. Fludrocortisone acetate was initially used for mineralocorticoid replacement in 33 of the 37 treated dogs with primary hypoadrenocorticism (final median dosage, 27.0 micrograms/kg/day), but supplementation was changed to desoxycorticosterone pivalate (DOCP) in four dogs because of poor response or adverse effects. Seven dogs with primary hypoadrenocorticism were treated with DOCP (final median dosage, 2.02 mg/kg/month). Prednisone, initially administered to 36 dogs, was discontinued in 11 dogs because of side effects. Of the dogs treated with fludrocortisone, the response was considered good to excellent in 26 dogs (78.8 per cent), fair in three, and poor in four. All dogs treated with DOCP responded well.

Basal and ACTH-stimulated plasma aldosterone concentrations are normal or increased in dogs with trichuriasis-associated pseudohypoadrenocorticism

We measured plasma concentrations of cortisol and aldosterone before and after administration of adrenocorticotropin (ACTH) in dogs with trichuriasis. These dogs had physical examination, historical, and serum electrolyte findings suggestive of hypoadrenocorticism; trichuriasis-associated pseudohypoadrenocorticism has been reported previously. We found normal basal and ACTH-stimulated plasma cortisol concentrations. Basal and ACTH-stimulated plasma aldosterone concentrations were normal in 2 dogs and increased in 3 dogs, suggesting that the electrolyte abnormalities seen in this clinical syndrome are not due to aldosterone deficiency.

Fluid and electrolyte balance in critical patients

Recognition and appropriate management of fluid and electrolyte disorders in critical patients is extremely important. In many cases, these secondary problems are more complicated and more serious than the initiating disease process. A severely ill diabetic patient, for example, is more likely to die from dehydration, hyperosmolality, metabolic acidosis, hypokalemia or hypophosphatemia than from hyperglycemia or lack of insulin therapy. Proper fluid therapy and treatment of electrolyte abnormalities make a major difference in the survival rate of critically ill animals.