Renal replacement and extracorporeal therapies in critical care: current and future directions.

There are a wide number of indications for extracorporeal therapies in the critical care environment. A common indication seen by the acute physician is continuous renal replacement therapy (CRRT) in a proportion of patients with acute kidney injury. It is therefore important that acute physicians have a sound understanding of the principles of CRRT in the acutely unwell patient. This review will outline the indications for its use, commonly used methods and anticoagulation considerations. It will discuss when to start and stop CRRT as well as describing potential treatment complications. This review will also discuss the role of therapeutic plasma exchange in critical care and novel extracorporeal therapies including blood purification in sepsis and carbon dioxide removal in acute respiratory distress syndrome and acute exacerbations of obstructive lung disease. Extracorporeal membrane oxygenation is outside of the scope of this article.

Preweaning intake and postweaning dietary energy effects on intake and metabolism of calves weaned at 26 days of age.

Holstein calves (n = 48) were used to evaluate whether preweaning feeding management affects postweaning DMI and metabolism after abrupt weaning at 26 d of age. Calves were fed only whole milk until d 19 of age. From d 19 to 26, calves were provided one of three isocaloric and isonitrogenous diets: milk at 15% of d-1 BW, milk at 12% of d-1 BW plus a grain-based supplement added to the pail, or milk at 12% of d-1 BW and drenched (force-fed) with the supplement. After weaning, calves were offered a low or high energy (1.7 or 5.8% ether extract) starter. From d 26 to 36, starter intake was similar between calves fed the supplement in the pail and those fed only milk but lower than for calves drenched with supplement. Plasma NEFA increased threefold from d 26 to 27, and calves fed only milk had higher NEFA than drenched calves. From d 26 to 42, plasma VFA of drenched calves were higher than those fed only milk. Except for an increase in plasma NEFA at d 36 and 42, high energy starter did not affect any variable. Preweaning drenching of calves stimulated postweaning adaptation to dry diets. Intake postweaning appears to depend more on physiological adaptation to dry diets than a preweaning feeding management.

Evaluation of starter diet crude protein level and feeding regimen for calves weaned at 26 days of age.

The objectives of this study were to evaluate two levels of CP in starter diets offered to calves weaned on d 26 and to compare postweaning intake of starter diets and performance of calves weaned at 26 or 42 d. Forty Holstein calves were housed in individual outdoor hutches and assigned to one of four treatments. Treatments consisted of weaning on d 26 after offering a 20% CP starter diet from d 1, or d 21, or after offering a 25% CP starter diet from d 21, or weaning on d 42 after offering a 20% CP starter diet from d 1 (control). Between d 42 and 84, calves were commingled in outdoor group pens. On d 42, BW of control calves was heavier than that of early weaned calves. On d 84, BW did not differ among treatments. Consumption of starter diet was not affected by the age at which it was first offered. Weaned calves consumed more starter diet than controls from d 29 to 42. Postweaning performance was not affected by increasing CP in the starter diet. Weaning treatment did not affect the incidence of scours. Comparison of CP intakes with current NRC recommendations suggests that CP requirements for young milk-fed calves are adequate.

Growth and plasma metabolites of lambs weaned to legume pasture at 28 days of age.

Two trials evaluated the potential for weaning lambs directly onto legume pasture at 28 d of age. Ewes and their twin-reared lambs were placed in paddocks on d 19; ewes were removed on d 28. In Trial 1, 60 lambs were allocated to three treatments: unweaned controls (CON1), lambs weaned onto first-cut alfalfa either without supplementary grain (WOG) or with up to 270 g.hd-1.d-1 supplementary grain (WG). Daily gains for the CON1, WOG and WG lambs were 309, 118 and 159 g for the period from d 28 to 40 (P greater than .05) and 241, 195 and 245 g for the period from d 40 to 56 (P greater than .05), respectively. In Trial 2, 80 lambs were allocated to four treatments: weaning onto first-cut alfalfa (early alfalfa, EA), second-cut alfalfa (late alfalfa, LA) birdsfoot trefoil (BFT) and unweaned controls (CON2, pastured on second-cut alfalfa). Daily gains for CON2 lambs were greater (P less than .05) than gains of EA and LA lambs (327 vs 136 and 136 g, respectively) for d 28 to 40, but not different (P greater than .05) for d 40 to 56 (245, 227 and 195 g, respectively). Gains for BFT lambs were lower (P less than .05) than for CON2 lambs for both periods (122 and 136 g, respectively), and BFT lambs appeared to be unthrifty after weaning. By d 32, weaning caused plasma glucose to decline 16.0 mg/dl and plasma nonesterified fatty acids to increase 365 mu eq/liter from preweaning levels. Hematocrit values ranged from 31 to 35% (Trial 1) and 25 to 29% (Trial 2), suggesting that the weaned lambs did not suffer from dehydration. Crossbred lambs can be weaned at 28 d of age directly onto first-cut or second-cut alfalfa.

The synthesis of glucose and ammonia by kidney tubules isolated from suckling and early-weaned lambs.

Glucose and ammonia production were examined in kidney tubules isolated from suckling and early-weaned lambs, on days 10-30 after birth, with abrupt weaning occurring at day 14. There were no differences in the rates of glucose or ammonia production for a given substrate by tubules isolated from any of the lambs, regardless of age or stage of weaning. The preferred substrates for gluconeogenesis were glycerol = lactate greater than propionate = pyruvate = fructose = proline greater than alanine greater than glutamate greater than glutamine greater than aspartate greater than glycine greater than serine, and for ammoniagenesis were glutamine much greater than alanine greater than aspartate much greater than serine greater than glycine = glutamate = proline.

Growth, intakes and metabolic responses of artificially reared lambs weaned at 14 d of age.

In two experiments, a total of 46 Finn Cross and Dorset lambs were artificially group-reared. Thirty eight were weaned abruptly at 14 d of age from a commercial milk replacer (MR) to a dry starter diet (SD). Lambs were self-fed cool (10 to 15 C) MR reconstituted to 25% dry matter (DM). The ground (2-mm screen) SD averaged 26.2% crude protein and 7.4% fat (DM basis). For both experiments, birth and weaning weights averaged 3.8 and 8.0 kg, respectively. Experiment 1 tested a strategy for encouraging postweaning DM intake. Fifteen lambs received MR reconstituted to 33% DM from d 11 to 14, and 15 lambs received standard 25% DM MR. Between d 14 and 15, intakes of DM, gross energy, crude protein and water dropped 86, 89, 85 and 64%, respectively. Lambs doubled their birth weights during the milk-feeding period and consumed 1.41 kg SD between d 14 and 25. The MR reconstitution rate did not affect weaning weight, postweaning SD or water intake, or growth check (GC, P greater than .10). Postweaning GC averaged 12.2 d and was not influenced (P greater than .10) by birth weight, sex or weaning weight. Mortality and disease rates under these conditions were negligible. Experiment 2 was designed to differentiate between the dual effects at weaning of altering the type of diet and of reducing the level of nutrient intake. Eight lambs were weaned to SD at 14 d, and eight lambs were bottle-fed isocaloric levels of MR from d 12 to 30. At weaning, plasma glucose concentration declined 1.4 mM from 6.7 mM due to fasting and an additional 1.0 mM due to the change of the type of diet (P less than .01). Plasma acetate and urea N concentrations rose steadily after d 16 in the SD-weaned lambs, but not in the MR-fed lambs (P less than .01), suggesting that the SD-weaned lambs absorbed ruminal fermentation products. These results indicate that artificially reared lambs may be routinely weaned to a dry diet at 14 d of age. The major alterations in plasma metabolites that occur within 6 to 8 d after abrupt weaning may define the period when these lambs become functional ruminants.

Effects of butylene and propylene glycols on body composition and fatty acid synthetase in lambs.

To test whether lipogenesis is limited by lack of glucose precursors, 45 lambs (30 kg) were randomly grouped by sex and initial weight and fed ad libitum in pens of three in a growth and slaughter experiment. The diets consisted of a basal mixed chopped hay (C), hay + 4% butylene glycol (BD) and hay + 4% propylene glycol (PG). On a dry matter basis, the crude protein content and in vitro true digestibility of the hay were 9.6 and 64%, respectively. Growth and feed intake were recorded. After 13 weeks, the lambs were killed. Blood glucose concentrations, feed intake and weight gains did not differ between diets, but intake and weight gains were minimal. BD increased (P greater than .01) blood ketones. Perirenal adipose tissue fatty acid synthetase (FAS) activity averaged 2.6, 2.4 and 1.2 nmole NADPH oxidized/mg cytosol protein/min for the BD, PG and C lambs, respectively. Values for both glycol-fed groups were higher (P greater than .01) than the control value. Carcass chemical composition followed a similar pattern, with BD, PG and C carcasses containing 38.1, 39.2 and 35.8% dry matter, respectively, and the dry matter containing 36.6, 39.4 and 30.0% fat, respectively. Carcasses of the BD and PG lambs did not differ significantly from each other, but both groups had more (P greater than .05) fat and less (P greater than .05) protein and ash than did the C carcasses, suggesting that the chemical composition of lamb carcasses may be nutritionally manipulated. The essentially equal response of adipose FAS activity and carcass fat in lambs fed PG and lambs fed BD indicates that the inclusion of glucogenic substances did not promote lipogenesis in these lambs fed at or slightly above maintenance.

detection of pregnancy in ewes with the ultrasonic scanopreg.

The accuracy of the ultrasonic Scanopreg was evaluated in tests with 24 commercials, West Virginia ewe flocks. Two Scanopreg units were used to check for pregnancy in 1,644 ewes that had been exposed to rams during the fall breeding season. Predictions were compared against lambing records. Possible accuracy errors were: type 1 (ewes diagnosed pregnant but failed to lamb) and type 2 (ewes diagnosed open but subsequently lambed). Type 1 error rate for 1,270 ewes was 1.2%. Type 2 error rates were 55.2, 15.5, 6.2, 1.1 and 4.0% for ewes pregnant less than 60, 60 to 69, 70 to 79, 80 to 120 and greater than 120 days at diagnosis, respectively. Accuracy of diagnoses during late pregnancy (greater than 120 days) was increased if obviously pregnant ewes were sorted out before testing. The combined error rate (all type 1 errors + type 2 errors for ewes 80 to 120 days pregnant) for 1,018 ewes was 2.5%. Ewe age had no apparent effect on type 2 error rates for ewes 80 to 120 days pregnant. Among flocks, type 1 and type 2 error rates varied from 0 to 11.8% and 0 to 7.1%, respectively. Variations in accuracy among flocks were associated primarily with undetected abortions (type 1 errors) and operator inexperience (type 2 errors). Scanopreg accuracy was not affected by individual units or inclement weather. We concluded that the Scanopreg is accurate and can be a reliable management tool if used to test ewes 80 to 120 days after they have been exposed to rams.