Energy expenditure in the acute renal failure patient mechanically ventilated

Renal Dysfunction in Cirrhosis: Critical Care Management

Cirrhotic patients with manifestations of the end-stage liver disease have a high risk for developing renal dysfunction even with minor insults. The development of renal dysfunction increases the morbidity and mortality of these patients. Causes of renal dysfunction in cirrhotics can be due to hepatorenal syndrome (HRS) or acute kidney injury (AKI) resulting from prerenal, renal, and postrenal causes. Development of pretransplant renal dysfunction has been shown to affect post-liver transplantation outcomes. Early detection and aggressive strategies for the prevention of further progression of renal dysfunction seem to decrease the morbidity and improve survival in this group of patients. This article aims to outline the pathogenesis of renal dysfunction in cirrhosis, etiological factors, and evaluation of renal dysfunction, strategies for aggressive therapy for renal dysfunction, the indications of renal replacement therapy (RRT) in this group of patients, and the various modalities of RRT with their merits and demerits. A thorough understanding of the pathogenesis, early detection, and aggressive corrective measures for AKI can prevent further progression. In conclusion, a good knowledge of treatment modalities available for renal dysfunction in cirrhosis and institution of timely interventions can significantly improve survival in this group of patients.

Calorie intake and patient outcomes in severe acute kidney injury: findings from The Randomized Evaluation of Normal vs. Augmented Level of Replacement Therapy (RENAL) study trial

Introduction

Current practice in the delivery of caloric intake (DCI) in patients with severe acute kidney injury (AKI) receiving renal replacement therapy (RRT) is unknown. We aimed to describe calorie administration in patients enrolled in the Randomized Evaluation of Normal vs. Augmented Level of Replacement Therapy (RENAL) study and to assess the association between DCI and clinical outcomes.

Methods

We performed a secondary analysis in 1456 patients from the RENAL trial. We measured the dose and evolution of DCI during treatment and analyzed its association with major clinical outcomes using multivariable logistic regression, Cox proportional hazards models, and time adjusted models.

Results

Overall, mean DCI during treatment in ICU was low at only 10.9 ± 9 Kcal/kg/day for non-survivors and 11 ± 9 Kcal/kg/day for survivors. Among patients with a lower DCI (below the median) 334 of 729 (45.8%) had died at 90-days after randomization compared with 316 of 727 (43.3%) patients with a higher DCI (above the median) (P = 0.34). On multivariable logistic regression analysis, mean DCI carried an odds ratio of 0.95 (95% confidence interval (CI): 0.91-1.00; P = 0.06) per 100 Kcal increase for 90-day mortality. DCI was not associated with significant differences in renal replacement (RRT) free days, mechanical ventilation free days, ICU free days and hospital free days. These findings remained essentially unaltered after time adjusted analysis and Cox proportional hazards modeling.

Conclusions

In the RENAL study, mean DCI was low. Within the limits of such low caloric intake, greater DCI was not associated with improved clinical outcomes.

Trial registration

ClinicalTrials.gov number, NCT00221013

Renal replacement therapies: physiological review

INTRODUCTION

A physiological review on renal replacement therapies (RRT) is a challenging task: there is nothing "physiologic" about RRT, since the most accurate, safe and perfectly delivered extracorporeal therapy would still be far from "physiologically" replacing the function of the native kidney.

METHODS

This review will address the issues of physiology of fluid and solute removal, acid base control and impact on mortality during intermittent and continuous therapies: different RRT modalities and relative prescriptions will provide different "physiological clinical effects" to critically ill patients with acute kidney injury (AKI), with the aim of restoring lost "renal homeostasis". On the other side, however, the "pathophysiology" of RRT, consists with unwanted clinical effects caused by the same treatments, generally under-recognized by current literature but often encountered in clinical practice. Physiology and pathophysiology of different RRT modalities have been reviewed.

CONCLUSION

Physiology and pathophysiology of RRT often coexist during dialysis sessions. Improvement in renal recovery and survival from AKI will be achieved from optimization of therapy and increased awareness of potential benefits and dangers deriving from different RRT modalities.

Validation of a predictive method for an accurate assessment of resting energy expenditure in medical mechanically ventilated patients

OBJECTIVE

Use comparison with indirect calorimetry to confirm the ability of our previously described equation to predict resting energy expenditure in mechanically ventilated patients.

DESIGN

Prospective, validation study.

SETTING

Eighteen-bed, medical intensive care unit at a teaching hospital.

PATIENTS

All adult patients intubated >24 hrs were assessed for eligibility. Exclusion criteria were clinical situations that could contribute to erroneous calorimetric measurements.

INTERVENTIONS

Resting energy expenditure was calculated using the original Harris-Benedict equations and those corrected for usual stress factors, the Swinamer equation, the Fusco equation, the Ireton-Jones equation, and our equation: resting energy expenditure (kcal/day) = 8 x weight (kg) + 14 x height (cm) + 32 x minute ventilation (L/min) + 94 x temperature (degrees C) - 4834.

MEASUREMENTS AND MAIN RESULTS

Resting energy expenditure was measured by indirect calorimetry for the 45 included patients. Resting energy expenditure calculated with our predictive model correlated with the measured resting energy expenditure (r2 = .62, p < .0001), and Bland-Altman analysis showed a mean bias of -192 +/- 277 kcal/day, with limits of agreement ranging from -735 to 351 kcal/day. Resting energy expenditure calculated with the Harris-Benedict equations was more weakly correlated with measured resting energy expenditure (r2 = .41, p < .0001), with Bland-Altman analysis showing a mean bias of 279 +/- 346 kcal/day between them and the limits of agreement ranging from -399 to 957 kcal/day. Applying usual stress-correction factors to the Harris-Benedict equations generated wide variability, and the correlation with measured resting energy expenditure was poorer (r2 = .18, p < .0001), with Bland-Altman analysis showing a mean bias of -357 +/- 750 kcal/day and limits of agreement ranging from -1827 to 1113 kcal/day. The use of the Swinamer, Fusco, or Ireton-Jones predictive methods yielded weaker correlation between calculated and measured resting energy expenditure (r2 = .41, p < .0001; r2 = .38, p < .0001; r2 = .39, p < .0001, respectively) than our equation, and Bland-Altman analysis showed no improvement in agreement and variability between methods.

CONCLUSIONS

The Faisy equation, based on static (height), less stable (weight), and dynamic biometric variables (temperature and minute ventilation), provided precise and unbiased resting energy expenditure estimations in mechanically ventilated patients.

Intradialytic nutritional support

PURPOSE OF REVIEW

Intradialytic nutritional support has been used for more than 30 years both in critically ill patients with acute renal failure and during maintenance hemodialysis. Present knowledge allows better estimation of its metabolic and nutritional efficacy, as well its effect on patient outcome.

RECENT FINDINGS

Recent data showed that intradialytic nutritional support is able to counteract these effects of dialysis on protein metabolism and to improve both nitrogen and energy balance. In maintenance hemodialysis patients, the improvement of nutritional status during nutritional support was shown to improve long-term survival. In critically ill patients with acute renal failure, protein sparing is one of the main therapeutic goals. The effect of nutritional support on patient outcome is not demonstrated. Recent data, however, showed that the improvement of nitrogen balance may be associated with a better outcome.

SUMMARY

Current information helps to better assess the effects of intradialytic nutritional support, to clarify the nutritional management of renal failure patients and to provide recommendations. Future research should focus on the possible means to improve the efficacy of nutritional support, either by modifying its components of by associating anabolic or anticatabolic agents.

The trivial function of sleep

Rest in poikilothermic animals is an adaptation of the organism to adjust to the geophysical cycles, a doubtless valuable function for all animals. In this review, we argue that the function of sleep could be trivial for mammals and birds because sleep does not provide additional advantages over simple rest. This conclusion can be reached by using the null hypothesis and parsimony arguments. First, we develop some theoretical and empirical considerations supporting the absence of specific effects after sleep deprivation. Then, we question the adaptive value of sleep traits by using non-coding DNA as a metaphor that shows that the complexity in the design is not a definitive proof of adaptation. We then propose that few, if any, phenotypic selectable traits do exist in sleep. Instead, the selection of efficient waking has been the major determinant of the most significant aspects in sleep structure. In addition, we suggest that the regulation of sleep is only a mechanism to enforce rest, a state that was challenged after the development of homeothermy. As a general conclusion, there is no direct answer to the problem of why we sleep; only an explanation of why such a complex set of mechanisms is used to perform what seems to be a simple function. This explanation should be reached by following the evolution of wakefulness rather than that of sleep. Sleep could have additional functions secondarily added to the trivial one, although, in this case, the necessity and sufficiency of these sleep functions should be demonstrated.

Adequacy of dialysis in acute renal failure

Renal replacement therapy (RRT) is currently the mainstay of management for patients with acute renal failure (ARF). Adequacy of dialysis in the setting of renal failure is defined poorly and encompasses multiple domains of clinical and biochemical outcomes. Multiple operational factors influence the delivery of adequate dialysis. No current standards exist for RRT for ARF; current RRT practices for ARF generally have been extrapolated from end-stage renal disease (ESRD) literature. The heterogeneity of patient population, variation in RRT practices, and differences in outcomes studied have made it difficult to define or study adequate dialysis in ARF or its impact on clinical outcomes.

Renal replacement therapy in acute renal failure

Acute renal failure (ARF) is a common condition in hospitalized patients. The aetiology and physiological characteristics differ from those of chronic renal failure (CRF) and both conditions should be approached differently. At present, the approach to the management of ARF is very heterogeneous. Attempts have therefore been made to improve consensus and to standardize treatment in the Acute Dialysis Quality Initiative (ADQI). Technology for the treatment of ARF is expanding. Traditional intermittent haemodialysis (IHD) is still a major treatment modality but continuous renal replacement therapies (CRRT) and slow, low-efficiency daily dialysis (SLEDD) are commonly used alternatives. Each modality has advantages and disadvantages, but to date no evidence exists for the superiority of one over the other. On the other hand, the availability of multiple options allows us to provide tailor-made treatment: the best modality is chosen depending on local expertise and the individual clinical scenario. Practice guidelines based on the best available evidence and the author's opinion are suggested.

Assessment of resting energy expenditure in mechanically ventilated patients

BACKGROUND

Usual equations for predicting resting energy expenditure (REE) are not appropriate for critically ill patients, and indirect calorimetry criteria render its routine use difficult.

OBJECTIVE

Variables that might influence the REE of mechanically ventilated patients were evaluated to establish a predictive relation between these variables and REE.

DESIGN

The REE of 70 metabolically stable, mechanically ventilated patients was prospectively measured by indirect calorimetry and calculated with the use of standard predictive models (Harris and Benedict's equations corrected for hypermetabolism factors). Patient data that might influence REE were assessed, and multivariate analysis was conducted to determine the relations between measured REE and these data. Measured and calculated REE were compared by using the Bland-Altman method.

RESULTS

Multivariate analysis retained 4 independent variables defining REE: body weight (r(2) = 0.14, P < 0.0001), height (r(2) = 0.11, P = 0.0002), minute ventilation (r(2) = 0.04, P = 0.01), and body temperature (r(2) = 0.07, P = 0.002): REE (kcal/d) = 8 x body weight + 14 x height + 32 x minute ventilation + 94 x body temperature - 4834. REE calculated with this equation was well correlated with measured REE (r(2) = 0.61, P < 0.0001). Bland-Altman plots showed a mean bias approaching zero, and the limits of agreement between measured and predicted REE were clinically acceptable.

CONCLUSION

Our results suggest that REE estimated on the basis of body weight, height, minute ventilation, and body temperature is clinically more relevant than are the usual predictive equations for metabolically stable, mechanically ventilated patients.

Continuous renal replacement therapy: opinions and evidence

Continuous arteriovenous haemofiltration (CAVH) is the first example of continuous renal replacement therapy (CRRT). CAVH was first applied for the treatment of diuretic unresponsive fluid overload. Subsequently, CRRT has undergone a remarkable growth, and it is now performed with pump technology (CVVH) and via double-lumen central venous catheters. In many intensive care units, especially in Australia and in Europe, CRRT has become the dominant, if not exclusive, form of artificial renal support. Continuous haemofiltration is now used beyond the original indications of blood purification, for the treatment of certain drug intoxications, for severe cardiac failure, for volume control during, after cardiopulmonary bypass, and to decrease the toxicity of chemotherapy. Furthermore, there is strong ongoing research into its role or that of derived techniques as possible adjuvant therapies during severe sepsis. Despite its large use, the current state of CRRT is surrounded by some controversies, and an effort should be made to give a dispassionate distillation of the literature for a final common definition of what is based on opinions and what carries sufficient evidence.

High protein intake during continuous hemodiafiltration: impact on amino acids and nitrogen balance

AIMS

To study the effect of combined continuous veno-venous hemodiafiltration (CVVHDF) and high (2.5 g/kg/day) parenteral amino acid supplementation on nitrogen balance, amino acid losses and azotemic control in a cohort of patients with severe acute renal failure (ARF).

METHODS

We administered 2.5 grams/kg/day of amino acids intravenously to seven critically ill patients with ARF. We obtained paired blood and ultrafiltrate (UF) samples (n=20) and calculated amino acid clearances and losses, nitrogen balance, protein catabolic rate and total nitrogen losses.

RESULTS

The median total serum amino acid concentration was high at 5.2 mmol/L with particularly high concentrations of ornithine, lysine, and phenylalanine, but a low level of histidine. The median overall amino acid clearance was 18.6 ml/min (range: 12 to 29 ml/min). UF losses as percentage of administered dose were high for tyrosine (53.6%) but low for methionine (3.0%) and arginine (2.3%). A positive nitrogen balance was achieved in 7 (35%) of the 20 study days with an overall median nitrogen balance of -1.8 g/day. Urea levels were maintained at a median of 26.6 mmol/L.

CONCLUSIONS

High protein intake increases the serum concentrations of most amino acids. Such protein supplementation, when coupled with CVVHDF achieves a slightly negative overall nitrogen balance in extremely catabolic patients while still allowing adequate azotemic control.

Continuous haemofiltration in the intensive care unit

Continuous renal replacement therapy (CRRT) was first described in 1977 for the treatment of diuretic-unresponsive fluid overload in the intensive care unit (ICU). Since that time this treatment has undergone a remarkable technical and conceptual evolution. It is now available in most tertiary ICUs around the world and has almost completely replaced intermittent haemodialysis (IHD) in some countries. Specially made machines are now available, and venovenous therapies that use blood pumps have replaced simpler techniques. Although, it remains controversial whether CRRT decreases mortality when compared with IHD, much evidence suggests that it is physiologically superior. The use of CRRT has also spurred renewed interest in the broader concept of blood purification, particularly in septic states. Experimental evidence suggests that this is a promising approach to the management of septic shock in critically ill patients. The evolution and use of CRRT is likely to continue and grow over the next decade.

How to feed patients with renal dysfunction

Renal dysfunction is common in critically ill patients and its presence has, in the past, posed serious challenges to nutritional support. Such challenges were due to the increased azotemia induced by protein or amino acid administration, the fluid overload caused by the administration of nutrients, and the difficulties associated with the control of these complications by means of conventional dialytic techniques.The development and increasing application of continuous renal replacement therapy has removed such concerns, because control of azotemia and fluid balance can be predictably and reliably achieved in all patients. Accordingly, the presence of renal failure should in no way influence the amount or type of nutritional support administered to a critically ill patient. We recommend that approximately 30-35 kCal/kg/d be administered enterally and begun within the first few hours of admission to the intensive care unit, and that protein intake be kept in the 1.5-2 g/kg/d range.Accumulating evidence also suggest that immune-enhancing enteral preparations decrease the duration of hospital stay, the number of infections, and perhaps mortality. Such preparations should be used in these patients. Finally, adequate vitamin and trace element supplementation is recommended to counterbalance the decrease in antioxidants and the loss of some vitamins during continuous renal replacement therapy. Available evidence suggests that if these steps are applied as part of a protocol-based approach to the nutritional support of patients with renal failure, morbidity and perhaps mortality can be significantly decreased.

Energy expenditure in patients with multiple organ failure

We measured the level of resting energy expenditure (BEE) and its evolution in patients with multiple organ failure (MOF). We studied 30 patients requiring mechanical ventilation and sedation. REE was measured by means of a closed circuit method on days 1-5, 7, 10 and 14 after initiating the protocol. REE values between 115% and 145% of the REE calculated from the Harris-Benedict's formula were considered as moderate hypermetabolism and values above 145% as severe hypermetabolism. A predictive formula for determining caloric requirements was developed and validated in another 25 MOF patients. In the study group, 25 patients presented moderate hypermetabolism (83%) and two severe hypermetabolism(7%). Mean REE in the whole group was stable but individual patients may have had a large variability in REE. The anthropometric variables, body temperature and reason for admission predicted the REE with a coefficient of determination of 0.73, according to the model: REE= -3295 + 105.5S - 8A + 11.7 W + 7.7 H + 93.2 T + 123.1 Tr - 145.6 Su where: S = sex (male = 1, female = 0); A: age in years; W: weight in Kg; H: height in cm; T: temperature in degrees C; Tr: trauma (Tr = 1); Su: surgical (Su = 1). The reliability of the model, taken from the validation group, showed that the shrinkage was 0.8%. In conclusion, when MOF patients are sedated they present moderate hypermetabolism. Day-to-day variability of REE in the individual patients and the large variability in estimating REE with our formula preclude its clinical utility and we recommend to measure REE in MOF patients.

Influence of a novel amino acid solution (enriched with the dipeptide glycyl-tyrosine) on plasma amino acid concentration of patients with acute renal failure

In this randomized, double-blind controlled study we compared the effect of parenteralnutrition with two different amino acid solutions on the plasma concentration of amino acids in 27 patients with acute renal failure. Fourteen patients received the new dipeptide-containing (glycyl-tyrosine) amino acid solution (AADI) in combination with glucose (60%) and fat (10%) as an 'all-in-one' solution over 120 h continuously via a central venous catheter. In the control group (AAST), parenteral nutrition with a standard amino acid solution in isonitrogenous and isocaloric form (0.7 g amino acids/kg BW/day and 25 kcal/kg BW/day) was administered to 13 patients over the same period of time. The administration of the dipeptide-containing amino acid solution caused a return to within the normal range of most of the amino acid concentrations which were decreased at the onset. A significant difference could be found between the AADI and AAST group for the achieved plasma concentrations of threonine (P < 0.01), phenylalanine (P<0.05), isoleucine (P<0.05), tryptophan (P<0.01) and ornithine (P<0.05), The phenylalanine/tyrosine ratio, did not change in the AADI group, while a marked increase was observed in the AAST group. (152.7 +/- 23.5 - 159.8 +/- 37.6 vs 172.6 +/- 24.6 - 310.6 +/- 136.7, respectively). The plasma concentration of glycyl-tyrosine was at the limit of detectability indicating rapid hydrolysis of the dipeptide in acute renal failure. These data suggest that the new dipeptide-containing amino acid solution offers a clear advantage over a standard amino acid formulation in correcting the amino acid imbalances in plasma of patients with ARF and is able to maintain normal tyrosine concentrations and phenylalanine/tyrosine ratio.

A prospective comparative study of moderate versus high protein intake for critically ill patients with acute renal failure

Critically ill patients with acute renal failure are traditionally treated with low-protein diets to help control uremia. This dietary approach may be deleterious to the patient's nutritional status and unnecessary, especially if continuous renal placement therapies (CRRT) are used. However, the optimal amount of protein supplementation during CRRT is unknown. In patients receiving CRRT, a high protein intake may result in a positive nitrogen balance in the absence of uncontrolled uremia. Accordingly, we studied nitrogen metabolism in two consecutive cohorts of acute renal failure patients receiving equal amounts of calories but variable amounts of nitrogen. One group received protein according to the preferences of the attending clinician, the other a high and fixed amount of protein (2.5 g/kg/day). Patients treated according to attending clinician preferences received significantly less dietary protein (1.2 g/kg/day vs. 2.5 g/kg/day; p < 0.0001) and had a negative mean nitrogen balance of -5.5 g/day. Patients receiving a high and fixed amount of protein had a less negative mean nitrogen balance (-1.92 g/day). Such patients were more likely to experience a positive nitrogen balance during any 24-h period (53.6% vs. 36.7%; p < 0.05). They also required more aggressive hemofiltration to maintain control of uremia (mean ultradiafiltrate volume: 2145 mL/h vs. 1658 mL/h; p < 0.0001) and had a significantly higher but still acceptable mean plasma urea level (26.6 mmol/L vs. 18 mmol/L; p < 0.0001). Survival was not significantly different in the two groups (37.5% vs. 31.3%). We conclude that a high-protein diet can be safely administered to critically ill patients with acute renal failure receiving continuous renal replacement therapy. Such a high protein intake improves nitrogen balance when compared to moderate protein intake. A low protein intake is unnecessary in patients treated with CRRT.

[Effect of postoperative complications on nutritional status: therapeutic consequences]

The occurrence of a postoperative complication represents an additional stress factor for patients and leads in many cases rapidly to a malnutrition status. Thus a nutritional support is required as soon as the foreseeable duration of starvation has a longer duration than one week. Considering its lower risk of septic complications and lower cost, enteral feeding should be initiated as soon as possible. Appraisal of caloric needs with standard formulas often leads to inappropriate nutritional management. Therefore the requirements should be assessed by indirect calorimetry if available. Nutritional support is a part of the management of a postoperative septic patient. It must be initiated when initial phase of haemodynamic instability is amended. Branched chain amino acids, medium chain triglycerides and other specific nutrients have failed to demonstrate a real clinical beneficial effect. In case of acute respiratory failure, nutritional support must be cautious with regard to caloric load, as carbohydrates may increase CO2 production and lipids may worsen hypoxaemia. In case of postoperative acute renal failure, nutritional management is facilitated by continuous haemofiltration techniques allowing an unlimited nutrient intake. Solutions containing only essential amino acids are not recommended. During severe acute pancreatitis, enteral feeding is indicated when ileus does not permit the use of the intestinal tract. Jejunal access must be preferred to stomach or duodenum. Lipid emulsions can be used safely if serum triglyceride concentrations remain below 4 g.L-1 during infusion and below 2 g.L-1 between infusions.

A prospective study of continuous hemodiafiltration in the management of severe acute renal failure in critically ill surgical patients

Severe acute renal failure associated with surgical disease and a highly catabolic state poses a major therapeutic challenge. Treatment by conventional dialysis or arteriovenous hemofiltration suffers from serious shortcomings. The current study assesses the clinical and biochemical impact of a newer approach (continuous hemodiafiltration) in a cohort of 60 critically ill surgical patients with severe renal failure. All patients were studied prospectively and assessed for illness severity. Their biochemical response to therapy was analyzed and their clinical course to either death or hospital discharge documented. The use of continuous hemodiafiltration (CHD) permitted full control of azotemia in all patients (mean steady-state urea concentration: 19.8 mmol/L) and was associated with rapid control of acidemia (mean pretreatment pH: 7.27; mean ph after 24-h treatment: 7.35; p < .001). During the 15,696 h of therapy, there were no treatment-induced episodes of hypotension and/or hypoxemia. All patients were able to receive full-dose enteral (9) or parenteral (51) nutritional support with 1.5 to 2.5 g/kg/day of protein as tolerated. Despite their illness severity (mean APACHE II score: 28.9) and the need for vasopressor support and ventilation in 90% of cases, 21 patients (35%) survived to hospital discharge. We conclude that continuous hemodiafiltration is safe and effective in surgical critically ill patients with acute renal failure, and that it is associated with a low morbidity and an encouraging survival rate.

Combined acute respiratory and renal failure: management by continuous hemodiafiltration

OBJECTIVES

To study the impact of continuous hemodiafiltration (CHD) on the morbidity and mortality of acute combined respiratory and renal failure in critically ill patients.

DESIGN

Prospective clinical study.

SETTING

Intensive Care Unit of a tertiary institution.

PATIENTS

One-hundred fifteen critically ill patients with combined acute respiratory and renal failure.

INTERVENTIONS

Treatment of all patients with either continuous arteriovenous hemodiafiltration (CAVHD) or continuous venovenous hemodiafiltration (CVVHD).

MEASUREMENTS

Assessment of illness severity, measurement of plasma urea, serum creatinine, electrolytes and arterial blood gases prior to and during treatment. Duration of oliguria, ICU stay, hospital stay, and final outcome.

RESULTS

One hundred fifteen critically ill patients with combined respiratory and renal failure (mean APACHE II score, 28.1; mean number of failing organs, 4.1) were studied. Thirty-five were treated with CAVHD and 80 with CVVHD for a mean treatment duration of 13.1 days per patient (range 2-47). Blood urea concentration fell from a mean of 29.4 mmol/l to a mean of 19.1 mmol/l (P < 0.001) and the serum creatinine concentration fell from a mean of 520 mumol/l to a mean of 374 mumol/l after 24 h of therapy (P < 0.001). The A-a gradient fell from a mean of 301 mmHg to a mean of 242 mmHg (P < 0.05). Despite the high degree of illness severity and the need for vasoactive drug infusion in 105 patients (91.3%), survival to hospital discharge was achieved in 33 patients (28.7%). For patients who required > 72 h of combined mechanical ventilation, survival was 22% (22 of 100 patients). Complications of continuous hemodiafiltration were few and all related to arterial vascular access.

CONCLUSIONS

In critically ill patients with combined acute respiratory and renal failure, continuous hemodiafiltration controlled azotemia without hypotension and with early improvement in gas exchange. PATIENTS treated with this approach achieved promising survival rates. Our findings support the view that CHD is safe and effective and that it offers important advantages over intermittent hemodialysis. It may be the dialytic therapy of choice in critically ill patients with combined acute respiratory and renal failure.

Plasma interleukin-1 alpha and beta, tumor necrosis factor-alpha, and lipopolysaccharide concentrations during pulmonary exacerbations of cystic fibrosis

Earlier studies have reported the presence of interleukin-1 (IL-1) and tumor necrosis factor (TNF) in the plasma of patients with cystic fibrosis (CF), but the results have been inconsistent. To investigate the relationships among plasma IL-1 alpha, IL-1 beta, TNF, lipopolysaccharide (LPS), and clinical status, measurements were made before and after 14 days of intravenous antibiotic therapy in 13 patients with CF. In addition, whole blood cytokine production rates were measured in 18 hr cultures stimulated with 10 micrograms/mL LPS or sterile saline (control). On admission, patients with CF had significantly greater plasma levels of LPS and IL-1 alpha compared with 20 healthy adult controls. In response to antibiotic therapy, the patients had statistically significant increases in weight, oxygen saturation, chest radiograph score, and forced expiratory volume in 1 second. They had significant decreases in pulse rate, residual volume/total lung capacity ratio, white blood count, neutrophil count, LPS concentration, and resting energy expenditure per kg body weight. There were no significant changes in the plasma concentrations of IL-1 alpha, IL-1 beta, or TNF and no significant changes in the basal or stimulated whole blood production rates of IL-1 alpha, IL-1 beta, or TNF. The immunological variables did not correlate significantly with clinical measurements of severity or the presence of fever. It is likely that in CF local pulmonary effects of cytokines are of more pathophysiologic significance than systemic effects.

Energy metabolism in acute hepatic failure

BACKGROUND

Conflicting data are available concerning energy metabolism in liver disease. Changes should be most pronounced in acute hepatic failure in which loss of 85% of liver cell mass is reported. Metabolic rate could be decreased due to impairment in liver mass but may also be increased as a result of systemic-mediator actions. To clarify this issue we studied energy metabolism in acute hepatic failure.

METHODS

Energy metabolism was evaluated by indirect calorimetry in 12 patients with acute liver failure and 22 sex-, age-, and body size-matched healthy individuals. In controls and 5 patients, studies were performed in the postabsorptive state; the remaining 7 patients received glucose at a rate of 8 mumol/kg body weight.min to prevent hypoglycemia.

RESULTS

Resting energy expenditure was increased in acute liver failure compared with healthy controls (5.1 +/- 0.14 kJ.min-1 x 1.73 m-2 vs. 3.97 +/- 0.08 kJ.min-1 x 1.73 m-2; mean +/- SEM; P < 0.001). Respiratory quotient and oxidation rates for major fuels were not different between the total patient-group and controls. In patients without glucose supply, energy derived from fat was higher and from carbohydrate lower than in healthy controls and patients with glucose supply.

CONCLUSIONS

Energy expenditure is increased in acute liver failure. Altered substrate oxidation can be normalized by glucose supply.

Acute continuous hemodiafiltration: a prospective study of 110 patients and a review of the literature

One hundred ten critically ill patients with acute renal failure receiving acute continuous hemodiafiltration (ACHD) in our intensive care unit were studied prospectively. Acute continuous hemodiafiltration consisted either of continuous arteriovenous hemodiafiltration or of continuous veno-venous hemodiafiltration, and was used for 17,817 hours (mean duration of patient treatment, 161.9 hours), resulting in a fall from a mean pre-ACHD urea of 35.7 mmol/L to a plateau value of 16.8 mmol/L at 72 hours of treatment. The mean urea clearance achieved was 24.9 mL/min. Eighty of these patients (72.7%) were receiving artificial ventilation at the time of ACHD and 45 (40.9%) had more than four failing organs. The mean APACHE II score was 27.7. Despite the degree of illness severity, 42 patients (32.2%) survived to discharge from hospital. The use of ACHD was associated with hemodynamic stability, rapid normalization of electrolytes, and the ability to freely administer drugs, blood, and/or blood products. It also allowed for maintenance of an aggressive, nitrogen-rich, nutritional regimen. Support of these critically ill patients with acute renal failure using ACHD was achieved safely and without the employment of additional dialysis-trained nursing staff. Our own experience and a review of the available literature strongly suggest that the advantages associated with the use of ACHD therapies are clinically significant and support the view that ACHD is a modality of renal replacement most suited to critically ill patients with acute renal failure.

Continuous arteriovenous haemodiafiltration in the critically ill: influence on major nutrient balances

The impact of continuous arteriovenous haemodiafiltration (CAVHD) on nitrogen, lipid and carbohydrate balance was studied in 9 parenterally fed critically ill patients with acute renal failure. The effects on carbohydrate delivery of varying dialysate glucose concentrations or flow rates were also investigated. The total daily nitrogen loss was a mean of 24.1 g (95% CI 20.9-27.3 g/24 h) with non-urea nitrogen losses of 7.6 g (95% CI 5.6-9.6 g/24 h). Glucose delivery was a mean 5.8 g/h with a dialysate glucose concentration of 1.5% and a flow rate of 1 l/h (95% CI 4.5-7.0 g/h). Carbohydrate delivery increased with increased dialysate glucose concentration (mean 11.4 g/h with 2.5% glucose: 95% CI 9.6-13.1 g/h; mean 14.9 g/h with a 4.25% concentration: 95% CI 10.9-19; and with increased dialysate flow rates (mean 9.6 g/h, 95% CI 6.8-12.4 g/h, using 2 l/h of 1.5% glucose). Only trace amounts of cholesterol and/or triglycerides were detected in occasional ultradiafiltrate samples. CAVHD has an important impact on nitrogen and carbohydrate balance, but not on lipid status. Knowledge of these interactions is crucial for the rational planning of nutritional strategies in the critically ill.

Energy expenditure during severe acute pancreatitis

Energy expenditure (EE) was measured, during 3 consecutive days, in six patients suffering from acute pancreatitis. Measurements were achieved postoperatively, under mechanical ventilation, using a mass spectrometer system. EE represented 1.49 times (range: 1.08-1.78) the predicted resting energy expenditure (PREE) according to the reevaluated Harris-Benedict equation. There was a weak positive correlation between EE and core temperature and a negative correlation between EE and nitrogen balance. EE/PREE was not different between septic and nonseptic patients (1.58 +/- 0.06 vs. 1.39 +/- 0.07). The calculations of nutrient oxidation rate indicated a high protein catabolic rate, a neoglucogenesis, and a lipolysis.