Lactic acidosis and osmotic diuresis produced by xylitol infusion

Management of Glucose Control in Noncritically Ill, Hospitalized Patients Receiving Parenteral and/or Enteral Nutrition: A Systematic Review

Hyperglycemia is a common occurrence in hospitalized patients receiving parenteral and/or enteral nutrition. Although there are several approaches to manage hyperglycemia, there is no consensus on the best practice. We systematically searched PubMed, Embase, Cochrane Central, and ClinicalTrials.gov to identify records (published or registered between April 1999 and April 2019) investigating strategies to manage glucose control in adults receiving parenteral and/or enteral nutrition whilst hospitalized in noncritical care units. A total of 15 completed studies comprising 1170 patients were identified, of which 11 were clinical trials and four observational studies. Diabetes management strategies entailed adaptations of nutritional regimens in four studies, while the remainder assessed different insulin regimens and administration routes. Diabetes-specific nutritional regimens that reduced glycemic excursions, as well as algorithm-driven insulin delivery approaches that allowed for flexible glucose-responsive insulin dosing, were both effective in improving glycemic control. However, the assessed studies were, in general, of limited quality, and we see a clear need for future rigorous studies to establish standards of care for patients with hyperglycemia receiving nutrition support.

HMR1402, a potassium ATP channel blocker during hyperdynamic porcine endotoxemia: effects on hepato-splanchnic oxygen exchange and metabolism

OBJECTIVE

To assess the effects of the potassium ATP (KATP) channel blocker HMR1402 (HMR) on systemic and hepato-splanchnic hemodynamics, oxygen exchange and metabolism during hyperdynamic porcine endotoxemia.

DESIGN

Prospective, randomized, controlled study with repeated measures. SETTING. Animal laboratory.

SUBJECTS

Eighteen pigs allocated to receive endotoxin alone (control group, CON, n=10) or endotoxin and HMR (6 mg/kg h(-1), n=8).

INTERVENTIONS

Anesthetized, mechanically ventilated, and instrumented pigs receiving continuous i.v. endotoxin were resuscitated with hetastarch to maintain mean arterial pressure (MAP) >60 mmHg. Twelve hours after starting the endotoxin infusion, they received HMR or its vehicle for another 12 h.

RESULTS

HMR transiently increased MAP by about 15 mmHg, but this effect was only present during the first 1 h of infusion. The HMR decreased cardiac output due to a fall in heart rate, and thereby reduced liver blood flow. While liver O(2) delivery and uptake remained unchanged, HMR induced hyperlactatemia [from 1.5 (1.1; 2.0), 1.4 (1.2; 1.8), and 1.2 (0.8; 2.0) to 3.1 (1.4; 3.2), 3.2 (1.6; 6.5), and 3.0 (1.0; 5.5) mmol/l in the arterial, portal and hepatic venous samples, respectively] and further increased arterial [from 8 (3; 13) to 23 (11; 57); p<0.05], portal [from 9 (4; 14) to 23 (14; 39); p<0.05] and hepatic vein [from 7 (0; 15) to 30 (8; 174), p<0.05] lactate/pyruvate ratios indicating impaired cytosolic redox state.

CONCLUSION

The short-term beneficial hemodynamic effects of KATP channel blockers have to be weighted with the detrimental effect on mitochondrial respiration.

Adenosine triphosphate-magnesium dichloride during hyperdynamic porcine endotoxemia: effects on hepatosplanchnic oxygen exchange and metabolism

OBJECTIVE

To assess the effects of adenosine triphosphate-magnesium dichloride (ATP-MgCl2) on systemic and hepatosplanchnic hemodynamics, oxygen exchange, and energy metabolism over 24 hrs of hyperdynamic normotensive porcine endotoxemia.

DESIGN

Prospective, randomized, controlled experimental study with repeated measures.

SETTING

Investigational animal laboratory.

SUBJECTS

Seventeen pigs were divided into two groups: eight animals receiving endotoxin served as a control group and nine animals received endotoxin (lipopolysaccharide) and ATP-MgCl2.

INTERVENTIONS

Pigs were anesthetized, mechanically ventilated, and instrumented. Endotoxemia was achieved by continuous intravenous infusion of Escherichia coli lipopolysaccharide. Animals were resuscitated by hetastarch targeted to maintain mean arterial pressure of >75 mm Hg. Twelve hours after the start of the endotoxin infusion, ATP-MgCl2, or its vehicle, were administered for 12 hrs.

MEASUREMENTS AND MAIN RESULTS

Mean arterial pressure was maintained in the control group because of a sustained increase in cardiac output achieved by fluid resuscitation, whereas ATP-MgCl2 significantly decreased mean arterial pressure because of further systemic vasodilatation. ATP-MgCl2 markedly increased portal venous flow. In contrast to the controls, hepatic arterial flow remained unchanged until the end of the experiment, despite the further increase in cardiac output. The ileal mucosal-arterial PCO2 gap (Delta PCO2) progressively increased (p <.05) in control animals, whereas it was restored to prelipopolysaccharide levels during ATP-MgCl2 infusion. Changes in Delta PCO2 correlated with those of portal vein blood flow in these animals (r = -.68, p <.05). Moreover, ATP-MgCl2 blunted the lipopolysaccharide-induced decrease in hepatic lactate balance but did not affect portal venous pH, hepatosplanchnic oxygen exchange, splanchnic lactate/pyruvate ratios, isoprostane, NO2- + NO3-, cytokine concentrations, or tissue nucleotide content.

CONCLUSION

During long-term hyperdynamic porcine endotoxemia, ATP-MgCl2 normalized the otherwise progressive rise of the ileal mucosal-arterial Delta PCO2. Furthermore, it allowed blunting of the continuous decrease in hepatic lactate clearance, thus preserving the metabolic coupling between lactate release from the intestine and lactate utilization by the liver.

Fructose, xylitol and glucose in total parenteral nutrition

A comparison was made between isocaloric amounts of 24% glucose and 24% Triofusin (composed of 120 g fructose, 60 g glucose and 60 g xylitol per liter) during the course of a 6-day, 3-phase crossover study of 15 patients undergoing total parenteral nutrition. The patients received a total of 0.5 g carbohydrate per kg per day. Plasma glucose as significantly higher during glucose infusion (7-22 mmol/l, median: 9 mmol/l,) than during Triofusin infusion (5-16 mmol/l, median: 6 mmol/l). A moderate to severe glucosuria was detected in three patients during infusion of 24% glucose, and this declined considerably during the Triofusin period. The total renal carbohydrate loss during the glucose period was 0-143 g, median: 6 g per day, and during the Triofusin period was 6-68 g, median: 10 g per day. The nitrogen balance and carbamide production rate were the same in the two infusion regimes. Changes in biochemical liver parameters were observed in most of the patients, but these could not be attributed to parenteral nutrition. None of the patients developed symptoms of metabolic acidosis. There was a slightly but significantly higher urinary excretion of oxalate in the Triofusin period (0.1-1.1 mmol per day, median: 0.5 mmol per day) than in the glucose period (0.1-1.0 mmol per day, median: 0.4 mmol per day). Most of the patients exhibited a slightly increased urinary excretion of urate, irrespective of the infusion regimen. Serum urate remained normal. It was concluded that Triofusin infused in the described dosage is a suitable calorie source for parenteral nutrition, but that it does not present a distinct advantage over the use of pure glucose solution. In patients suffering from reduced glucose tolerance, however, Triofusin represents a more easily manageable calorie course.

Metabolic interactions of xylitol and ethanol in healthy males

The effects of oral administration of xylitol on the rate of ethanol elimination and on the ethanol-induced changes in blood concentrations of lactate and pyruvate were studied in seven healthy male subjects. Xylitol (1.0 g/kg body weight) was administered orally and ethanol (0.8 g/kg body weight) intravenously. In the control experiments glucose was given instead of xylitol. Xylitol had no significant effect on the rate of ethanol elimination or on the ethanol-induced increase in the blood lactate concentration. The ethanol-induced changes in the lactate/pyruvate ratio were not affected by xylitol. It is suggested that the ineffectiveness of xylitol is due to its low concentration in the liver after oral administration. Ethanol induced a 5--10 fold increase in the blood concentration of xylitol. This is most probably due to inhibition of xylitol oxidation in the liver by the ethanol-induced reduction in the hepatic redox state. The clinical significance of this finding is unknown.

[Comparison of metabolic effects of infusions of glucose and glucose substitutes]

The side effects of high dosed infusions of glucose and glucose substitutes (fructose, sorbitol, xylitol) in metabolically healthy volunteers have been studied. Infusions of glucose or fructose in high dose cause an increase in blood lactate levels. This effect, to a lesser degree, is observed with sorbitol. No effect, however, was seen with xylitol. Following the termination of the glucose infusions the lactate levels remain elevated, whereas after termination of the fructose infusions the lactate concentration is normalized within a short time. A decrease in the serum phosphate levels was observed for all the substances used. The most active were glucose and xylitol, followed by fructose and sorbitol, respectively. Similarly, all these substances cause an elevation of the serum bilirubin levels, though enzyme activities in serum remain unaffected. Xylitol had the greatest effect on bilirubin levels, however, glucose was also effective. The only side effect caused by the glucose substitutes was the stimulation of uric acid synthesis. In this respect xylitol was most effective. Some of metabolic effects of glucose and glucose substitutes are not yet clearly understood. However, even at very high doses these effects are not to be regarded as true "side-effects".

[Studies on the pharmacokinetics of carbohydrates as a basis for their use in parenteral feeding]

Metabolic effects of glucose, fructose, sorbitol, xylitol and their combinations during intravenous application in men were investigated. The totale and metabolic clearance, the renal and metabolic elimination, the half-time and the turnover rate were measured. For all sugars intravenous long-term infusions from six to twelve hours were performed. Up to a dosage of 0.75 g/kg/h for glucose 0.5 g/kg/h for sorbitol and 0.25 g/kg/h for fructose and xylitol a steady state of substrates and metabolites has been found. If these dosage-limits are exceeded during glucose application a hyperglucosemia, after sorbitol a continous rise in sorbitol blood level, during fructose a rise in lactate and during xylitol infusion clinical side effects occurred. It could be shown that during simultaneous application of glucose, fructose and xylitol the utilization of glucose rises whereas the utilization of fructose and xylitol remain on such levels as if these sugar were infused alone.

Identification of crystals deposited in brain and kidney after xylitol administration by biochemical, histochemical, and electron diffraction methods

The positive identification of crystals of calcium oxalate occurring in brain and kidney after xylitol administration is described. Biochemical, histochemical, conventional light and electron microscopical methods, including selected area electron diffraction, were used to characterize the crystals.