Characterization of the clinical characteristics, electrolytes, acid–base, and renal parameters in male cats with urethral obstruction

Objective: To characterize the clinical characteristics, electrolyte changes, acid–base changes, and renal parameters in a consecutive population of cats with urethral obstruction. Design: Retrospective clinical study. Setting: University Veterinary Teaching Hospital. Animals: Two hundred and twenty‐three male cats that presented consecutively with urethral obstruction between 1997 and 1999. Interventions: None. Measurements and main results: The medical records of 223 cats with urethral obstruction were reviewed for signalment, previous medical history, indoor/outdoor status, body weight, clinical signs, physical examination findings, renal function tests (blood urea nitrogen and creatinine), and blood gas and electrolyte analysis. The majority of cats were relatively stable without serious metabolic derangements. Only 12% (24/199) of cats had severe hyperkalemia (>8.0 mmol/L). Hyperkalemia did not occur in isolation; the majority of these cats had concurrent acidemia and low ionized calcium concentrations. Potassium was significantly inversely correlated with pH, bicarbonate, pCO₂, sodium, chloride, and ionized calcium, but positively correlated with blood urea nitrogen and creatinine. Ionized calcium was positively correlated with pH and bicarbonate. Of the animals with a potassium concentration greater than 8.0 mmol/L, 75% (18/24) had an ionized calcium concentration of less than 1.0 mmol/L. Seventy‐nine percent (19/24) of cats with a potassium concentration greater than 8.0 mmol/L had a blood pH<7.20. Similarly, 74% (23/31) of cats with a pH<7.20 had an ionized calcium concentration <1.00 mmol/L. Conclusions: The majority of cats with urethral obstruction presented with mild electrolyte and blood gas changes and were relatively stable, although 12% of cats had multiple, life‐threatening metabolic derangements. Of 219 cats in this study, 205 (93.6%), where it could be determined, survived to discharge from the hospital, supporting the fact that most cats with urethral obstruction survive the acute episode with emergency treatment.     

Historical and physical parameters as predictors of severe hyperkalemia in male cats with urethral obstruction

Objective: To evaluate selected historical and physical parameters as predictors of hyperkalemia in male cats with urethral obstruction. Design: Retrospective study. Setting: Veterinary teaching hospital. Animals: Two hundred and twenty‐three male cats. Interventions: None. Measurements and main results: The metabolic derangements of 223 male cats that presented with urethral obstruction from 1997 through 1999 were reported in a companion article. Approximately 12% of the cats had multiple, life‐threatening metabolic derangements. In the present study, historical and physical parameters were evaluated as predictors of hyperkalemia (K⁺≥8.0 mmol/L) in cats with urethral obstruction. The 4 historical parameters significantly associated with hyperkalemia were: first time obstruction, outdoor status, anorexia, or vomiting. The 5 physical parameters significantly associated with hyperkalemia were: rectal temperature, heart rate, respiratory rate, pulse quality, and the presence of arrhythmia. Of the physical parameters, a rectal temperature below 95–96.6°F (35–35.9°C) or a heart rate below 120 b.p.m. were the most accurate predictors. When used in combination (i.e., evidence of bradycardia and hypothermia), the specificity for hyperkalemia was 98–100%. Conclusions: Rectal temperature and heart rate were the best parameters for predicting hyperkalemia in this population.     

Assessment of blood pressure in cats presented with urethral obstruction

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.     

The HemoCue® for point-of-care hemoglobin measurement and packed cell volume estimation in cats

Objective: To determine conversion formulas so that values from the HemoCue^® hemoglobinometer (Hb_HQ) could be equated to hemoglobin concentrations measured by the gold‐standard cyanomethemoglobin (Hb_CY) method and used for estimation of packed cell volume (PCV) in cats. Study design: Prospective, in vitro. Animals: Twelve healthy, adult, client‐owned cats. Interventions: The PCV of 12 parent blood samples was manipulated between ～3 and ～80% by removing or adding autologous plasma. Hemoglobin was measured by the Hb_CY method at a university clinical pathology laboratory and by the azidemethemoglobin method in a Hb_HQ. PCV was determined by micro‐centrifugation. Measurements and main results: Hemoglobin varied from 1–26 g/dL. Repeated‐measures regression of Hb_CY on Hb_HQ demonstrated that the Y‐intercept was not different from zero. When the regression was repeated, forcing the line through the origin the coefficient for converting Hb_HQ to Hb_CY was not significantly different from 1.0 (adjusted R²=99.7%). The conversion formula was Hb_CY=Hb_HQ. Using similar methods, the conversion formula for estimating PCV was PCV=3.1 Hb_HQ (adjusted R²=99.8%). Conclusion: Hemoglobin concentration measured by the HemoCue^® was indistinguishable from the (Hb_CY) method in feline blood over a wide range of hemoglobin concentrations. This study demonstrates that in cats PCV=3.1Hb_HQ. Clinical relevance: The HemoCue^® is useful for point‐of‐care hemoglobinometry and for estimating PCV in cats.     

Serum and red cell folate and serum vitamin B12 levels in horses

SUMMARY Vitamin B12 and folate concentrations were determined by radioimmunoassay in groups of horses in Queensland. Highest serum vitamin B¹² levels were found in supplemented performance horses. These, together with pastured horses that included pregnant and lactating mares, had significantly greater serum folate activity than permanently stabled animals. The range of red cell folate concentrations was much narrower in horses in training than from any other group. Red cell folate may be a better indicator of a horse's folate status than the serum folate value. Vitamin B¹² and folate concentrations were highest in spring and summer. Small intestinal dysfunction in 2 horses was not associated with vitamin B¹² or folate malabsorption. Serum folate levels returned to normal 24 h after intramuscular injections of 75 to 150 mg folic acid, whereas serum vitamin B¹² values remained elevated for at least one week following injections of 8 to 10 mg to non-supplemented horses.     

Effect of 1,25 dihydroxyvitamin D3 on the calcium and magnesium metabolism of lactating cows

Administration of 1,25 dihydroxyvitamin D3 (1,25(OH)2D3) to lactating dairy cows resulted in increased dietary calcium absorption and elevated concentrations of plasma calcium. Dietary magnesium absorption was unaffected by 1,25(OH)2D3 however, plasma magnesium concentration was depressed. Injections of 1,25(OH)2D3 were effective in elevating plasma calcium concentrations in both normal and hypomagnesaemic cows. This indicates a potential use for 1,25(OH)2D3 to prevent and treat hypocalcaemic cows with or without concurrent hypomagnesaemia.     

Serum concentrations of ionized calcium, vitamin D3, and parathyroid hormone in captive thick-billed parrots (Rhynchopsitta pachyrhyncha).

Serum collected from 68 thick-billed parrots (Rhynchopsitta pachyrhyncha) from 15 institutions was analyzed for ionized Ca (iCa), total Ca (tCa), P, total protein (TP), albumin (Alb), parathyroid hormone (PTH), and vitamin D3. Values were not distributed normally; 95% frequency intervals were as follows: iCa (0.82-1.3 mmol/L), tCa (1.37-2.09 mmol/L,), P (0.35-1.75 mmol/L), TP (21-39 g/L), Alb (9-13 g/L), PTH (0-65.68 pmol/L), and vitamin D3 (5.2-51 nmol/L). Sixty percent (+/-7.5%) of tCa was ionized. Female thick-billed parrots had significantly higher mean iCa (1.11 mmol/L, n = 22) than male thick-billed parrots (1.05 mmol/L, n = 32). tCa and iCa values in thick-billed parrots were lower than the reported values for other psittacine species. A significant positive linear relationship existed between Alb-TP and iCa-tCa ratios. A significant inverse linear relationship was also identified between the tCa-P ratio and PTH. These findings are consistent with known domestic avian Ca physiology.