Assessment of blood pressure in cats presented with urethral obstruction

Abstract

Objective: To determine the arterial blood pressure at presentation in male cats with acute urethral obstruction, and to determine whether there was any correlation between these measurements and concurrent metabolic abnormalities. Design: Prospective, single cohort, observational study. Setting: Private, small animal, after‐hours emergency clinic. Animals: Twenty‐eight client‐owned male cats with acute urethral obstruction and no other known coexisting disease. Interventions: Indirect oscillometric blood pressure measurements obtained before blood sampling and treatment. Measurements and main results: Mean arterial blood pressure (MAP) measurements, physical examination parameters, serum blood urea nitrogen (BUN), creatinine, potassium, phosphorus, total calcium and magnesium concentration, venous pH, lead II electrocardiogram, and urine volume in bladder were evaluated. No cats were hypotensive at presentation; 71% (20/28) were normotensive (median MAP=100 mmHg, range 93–140 mmHg); and 29% (8/28) were hypertensive (median MAP=153 mmHg, range 145–176 mmHg). Compared with hypertensive cats, normotensive cats had significantly lower heart rates (P=0.0201) and lower calcium (P=0.0152). For all 28 cats, MAP correlated with serum potassium and total calcium (P=0.0033). Conclusions: Though potassium and total calcium were inversely and directly correlated respectively with blood pressure in cats with urethral obstruction, none of the cats were hypotensive on presentation. Normotension on admission does not support the absence of biochemical and physical abnormalities in obstructed cats.

Biochemical, electrolytic, and cardiovascular evaluations in cats with urethral obstruction

“…It has been hypothesized that acid-base and electrolyte abnormalities could have maintained pressure within the normal range in these cats. This is because there is a balance between the forces that increase and decrease blood pressure in felines and is, therefore, less susceptible to hypotension [36]. In the same study, it was also found that patients severely affected by UO had normal blood pressure, while patients who exhibited early signs of the disease were more likely to exhibit hypertension, which was also a finding in our study.…”

“…Hypotension was not observed in the animals, despite the severity of clinical changes. Other studies have also reported a lack of hypotension in patients in UO [35,36]. It has been hypothesized that acid-base and electrolyte abnormalities could have maintained pressure within the normal range in these cats.…”

“…We may infer that specific factors contributed to hypertension on D1, such as activation of the renin-angiotensin-aldosterone system, as described in a study involving dogs with ureteral obstruction, thus increasing renin release and consequent increase in blood pressure [37]. In addition, stress and pain are also factors that have been reported to contribute to increased sympathetic nervous system activity and cause increased heart rate and blood pressure [35,36].…”

Obstructive Uropathy and Nephropathy

“…In one study, the median volume of urine removed by urinary catheter at the time initial obstruction was relieved in 28 cats was 85 mL (range, 35 to 280 mL) (Malouin, Milligan, Drobatz, 2007). In one study, the median volume of urine removed by urinary catheter at the time initial obstruction was relieved in 28 cats was 85 mL (range, 35 to 280 mL) (Malouin, Milligan, Drobatz, 2007).…”