Randomized comparison of in vivo performance of TearLab® and I-PEN® osmometry in normal dogs.

OBJECTIVE: To compare tear film (TF) osmolarity measured using TearLab® and I-PEN® osmometers in the same dogs without any ocular surface disease. ANIMAL STUDIED: Fifty-two dogs (98 eyes) of different breeds were evaluated. PROCEDURES: Tear film (TF) osmolarity was evaluated at 2-min intervals. The test was randomly determined, and single measurements were performed using each osmometer. Subsequently, complete ophthalmologic examinations were performed based on Schirmer tear test-1 (STT-1) analysis, tear film breakup time (TFBUT), and slit-lamp biomicroscopy. For each osmometer, the mean ± standard deviation of the TF osmolarity was calculated, and a paired Student's t-test was used to compare the values obtained. Pearson correlation analysis was performed to assess the association between osmolarity and other values such as STT-1, TFBUT, and age. RESULTS: Tear film osmolarity determined using TearLab® (340.42 ± 15.87 mOsm/L) and I-PEN® (321.58 ± 17.39 mOsm/L) were significantly different (p < .001). However, statistical significance could not be confirmed between osmolarity and other values, such as STT-1, TFBUT, and age. CONCLUSIONS: In dogs, the TF osmolarity values obtained using TearLab® tend to be higher than those obtained using I-PEN®, contrary to that observed in humans. These findings can serve as a reference for establishing normal values for each osmometer for clinical use in measuring TF osmolarity in dogs.

Analytical validation and reference intervals for freezing point depression osmometer measurements of urine osmolality in dogs.

Urine osmolality (UOsm) is considered the most accurate measure of urine concentration and is used to assess body fluid homeostasis and renal function. We performed analytical validation of freezing point depression measurement of canine UOsm, to establish reference intervals (RIs) and to determine the effect of age, sex, and reproductive status on UOsm in dogs. Clinically healthy dogs ( n = 1,991) were retrospectively selected and stratified in groups by age (young [0-12 mo], adults [13-84 mo], and seniors [>84 mo]), sex (females and males), and reproductive status (intact and neutered). RIs were calculated for each age group. Intra- and inter-assay coefficients of variation were <1% in all cases. Good linearity ( r2 = 1, p < 0.001) and recovery (89-98%) were observed. The limit of detection and limit of quantification were zero. Urine specific gravity and UOsm had a highly significant positive correlation ( r = 0.96, p < 0.001) but had inconsistent agreement. The 95% RI for canine UOsm was 369-2,416 mOsm/kg in young and adult dogs, and 366-2,178 mOsm/kg in seniors. Senior dogs had a significantly lower UOsm than young and adult dogs ( p < 0.000). Neutered females had a significantly lower UOsm than intact female dogs ( p < 0.002). These results indicate that the method evaluated is adequate for UOsm measurement and that RIs based on age and reproductive status should be used in dogs.

Short- to medium-term effects of consumption of quebracho tannins on saliva production and composition in sheep and goats.

Eight Merino sheep (49.4 ± 4.23 kg BW) and 8 Alpine goats (53.2 ± 2.51 kg BW) were used to study the effect of ingestion of quebracho tannins on salivation. Four sheep and 4 goats were individually fed a daily allotment of 20 g DM of alfalfa hay/kg BW (Control). Another 4 sheep and 4 goats were also given 20 g DM of alfalfa hay/kg BW supplemented with 50 g of quebracho/kg DM (Tannin) for a period of 64 d. The saliva secretion from the left parotid gland was collected by insertion of a polyvinyl chloride catheter into the parotid duct and the amount of parotid saliva produced recorded over three 48-h periods on d 1 and 2 (P1), d 31 and 32 (P2), and d 61 and 62 (P3) after the tannin feeding was initiated. The total amount of saliva produced was estimated from rumen water kinetics determined on d 4, d 34, and d 64 of the experiment. Experimental design was completely randomized, with repeated measures on each experimental unit, performing separate analysis for sheep and goats. Parotid saliva production was not affected by the sampling period in either animal species receiving the Control diet. Corresponding values for sheep were 2.04, 2.12, and 2.27 L/d (P = 0.89) and for goats 1.65, 1.79, and 1.86 L/d (P = 0.95). Sheep fed the Tannin diet produced 55, 73, and 107% of the amount of saliva recorded in sheep fed the Control diet on P1, P2, or P3, respectively. Corresponding values in goats were 88, 130, and 134% on P1, P2, or P3, respectively. Estimated total saliva production was not affected (P = 0.50 for sheep and P = 0.97 for goats) by the ingestion of quebracho. There was no difference (P > 0.10) in osmotic pressure, P, Mg, Ca, urea, and protein concentrations in parotid saliva. There were, however, differences in Na and K concentrations in response to the ingestion of quebracho tannins, with Na concentrations increasing (P = 0.05) and K concentrations decreasing (P = 0.04) in sheep saliva and pH increasing (P = 0.05) in goat saliva. In conclusion, the inclusion of quebracho at 50 g/kg DM for 64 d does not appear to alter saliva production in sheep and goats.

Serum osmolality and effects of water deprivation in captive Asian elephants (Elephas maximus).

Serum from 21 healthy, captive Asian elephants (Elephas maximus) was evaluated by measured and calculated osmolality. Serum osmolality results for this population of Asian elephants had a median of 261 mOsm/kg and an interquartile interval of 258-269 mOsm/kg when measured by freezing point osmometry and a median of 264 mOsm/kg and an interquartile interval of 257-269 mOsm/kg when measured by vapor pressure osmometry. These values are significantly lower than values reported in other mammalian species and have important diagnostic and therapeutic implications. Calculated osmolality produced unreliable results and needs further study to determine an appropriate formula and its clinical application in this species. A 16-hr water deprivation test in 16 Asian elephants induced a small, subclinical, but statistically significant increase in measured serum osmolality. Serum osmolality, blood urea nitrogen, and total protein by refractometer were sensitive indicators of hydration status. Serum osmolality measurement by freezing point or vapor pressure osmometry is a useful adjunct to routine clinical tests in the diagnostic evaluation of elephants.