Clinically normal dogs were evaluated in states of dehydration, euhydration, and after fluid administration to determine effects of hydration state on renal clearance values. Endogenous creatinine, exogenous creatinine, and [(14)C]inulin clearances, were determined to measure glomerular filtration rate (GFR); in some experiments p-aminohippurate clearance was determined to measure renal plasma flow. Dehydration caused significant (P < 0.05) decrease in clearance values, compared with euhydration, and clearance values during euhydration were significantly (P < 0.05) less than values obtained after a single gavage with water (30 ml/kg of body weight). Sustained administration of 3 fluid regimens was evaluated for effects on clearance values (treatment A = 30 ml of lactated Ringer's solution/kg/h; treatment B = 30 ml of water/kg by gavage hourly; treatment C = 10 ml of glucose:lactated Ringer's solution/ kg/h). All regimens of fluid therapy caused significant P < 0.05), progressive increases in GFR, but treatment C resulted in the most stable GFR values. Increases in clearance values were associated with positive fluid balance; the rate of fluid administration was greater than the rate of urine formation. Data from 285 GFR determinations on 85 dogs were evaluated retrospectively. For each determination, three 20-minute urine collections were made beginning 40 minutes after 30 mi of water/kg was given by gavage. Values between collections were significantly (P < 0.05) different, but varied by < 3%. Comparison of methods for measurement of GFR indicated that endogenous creatinine clearance and [14)C]inulin clearance were highly correlated (R(2) = 0.82), but mean clearance values were markedly different (mean +/- SEM, 28.70 +/- 0.01 and 37.07 +/- 1.29 ml/min, respectively). Exogenous creatinine clearance and [(14)C]inulin clearance were highly correlated (R(2) = 0.95), and mean values were 40.54 +/- 0.70 and 41.02 +/- 0.70 ml/min respectively. We conclude that: state of hydration has a marked effect on GFR; rate of fluid administration that exceeds rate of urine production results in progressive increases in GFR; a single water gavage of 30 ml/kg gives stable GFR values for three 20-minute collection periods, may avoid subclinical states of dehydration, and facilitates accurate urine collections; and endogenous creatinine clearance, as conducted in this study, does not accurately measure GFR.

Nine adult female sheep were each surgically fitted with an Ivan and Johnston reentrant cannula in the cranial part of the duodenum just distal to the pylorus. By diversion (loss) of abomasal outflow, this model has been shown to consistently induce hypochloremic, hypokalemic metabolic alkalosis, accompanied by hyponatremia and dehydration. Each sheep was subjected to 3 treatment trials, each preceded by a 24-hour prediversion period, and a diversion period during which a syndrome of hypochloremia (68 +/- 2 mEq/L), hypokalemia, hyponatremia, and metabolic alkalosis was induced. Development of this syndrome was attributable to losses of large amounts of acid and electrolytes in the abomasal effluent. Mean total electrolyte contents of the effluent were: Cl-, 650 +/- 27 mEq; Na+, 388 +/- 23 mEq; and K+, 123 +/- 12 mEq, with total volume loss ranging from 3.6 to 10.0 L of gastric contents and pH ranging from 3 to 5. Decreases in plasma electrolyte concentrations also can be attributed to decreased intake, because anorexia developed shortly after the onset of diversion. Electrolyte losses in urine during diversion were minimal for Cl-(mean +/- SEM, 12.0 +/- 5.1 mEq), but were greater for Na+ (124.2 +/- 14.5 mEq) and K+ (185.1 +/- 31.2 mEq). Treatments consisted of 0.9% NaCl (300 mosm/ L), 3.6% NaCl (1,200 mosm/L, and 7.2% NaCl (2,400 mosm/L) administered over a 2-hour period, with the administered volume determined by the estimated total extracellular fluid Cl- deficit. Significant difference was not found among treatments, with all solutions resulting in return of clinicopathologic and physical variables to prediversion values within 12 hours of treatment. We concluded that rapid iv replacement of Cl-, with small volumes of hypertonic saline solution, is safe and effective for correction of experimentally induced hypochloremic, hypokalemic, metabolic alkalosis in sheep.