Protein-sparing effect in skeletal muscle of growth hormone treatment in critically ill patients

Pathophysiology and Therapeutic Management of Bone Loss in Patients with Critical Illness

Patients with critical illnesses are at higher risk of comorbidities, which can include bone mineral density loss, bone turnover marker increase, and fragility fractures. Patients admitted to intensive care units (ICUs) have a higher risk of bone fractures. Since hypermetabolism is a characteristic of ICU patients, such patients are often rapidly affected by systemic deterioration, which often results in systemic wasting disease. Major risk factors for ICU-related bone loss include physical restraint, inflammation, neuroendocrine stress, malnutrition, and medications. A medical history of critical illness should be acknowledged as a risk factor for impaired bone metabolism. Bone loss associated with ICU admission should be recognized as a key component of post-intensive care syndrome, and further research that focuses on treatment protocols and prevention strategies is required. Studies aimed at maintaining gut integrity have emphasized protein administration and nutrition, while research is ongoing to evaluate the therapeutic benefits of anti-resorptive agents and physical therapy. This review examines both current and innovative clinical strategies that are used for identifying risk factors of bone loss. It provides an overview of perioperative outcomes and discusses the emerging novel treatment modalities. Furthermore, the review presents future directions in the treatment of ICU-related bone loss.

Variability in Skeletal Muscle Protein Synthesis Rates in Critically Ill Patients

(1) Background: Muscle protein synthesis in critically ill patients is, on average, normal despite dramatic muscle loss, but the variation is much larger than in controls. Here, we evaluate if this variation is due to 1) heterogeneity in synthesis rates, 2) morphological variation or infiltrating cells, or 3) heterogeneity in the synthesis of different protein fractions. (2) Methods: Muscle biopsies were taken from both legs of critically ill patients (n = 17). Mixed and mitochondrial protein synthesis rates and morphologies were evaluated in both legs. Synthesis rates of myosin and actin were determined in combined biopsies and compared with controls. (3) Results: Muscle protein synthesis rates had a large variability in the patients (1.4-10.8%/day). No differences in mixed and mitochondrial protein synthesis rates between both legs were observed. A microscopic examination revealed no morphological differences between the two legs or any infiltrating inflammatory cells. The synthesis rates for myosin were lower and for actin they were higher in the muscles of critically ill patients, compared with the controls. (4) Conclusions: The large variation in muscle protein synthesis rates in critically ill patients is not the result of heterogeneity in synthesis rates, nor due to infiltrating cells. There are differences in the synthesis rates of different proteins, but these do not explain the larger variations.

Protein absorption and kinetics in critical illness

PURPOSE OF REVIEW

Timing, dose, and route of protein feeding in critically ill patients treated in an ICU is controversial. This is because of conflicting outcomes observed in randomized controlled trials (RCTs). This inconsistency between RCTs may occur as the physiology of protein metabolism and protein handling in the critically ill is substantially different from the healthy with limited mechanistic data to inform design of RCTs. This review will outline the current knowledge and gaps in the understanding of protein absorption and kinetics during critical illness.

RECENT FINDINGS

Critically ill patients, both children and adults, lose muscle protein because of substantial increases in protein degradation with initially normal, and over time increasing, protein synthesis rates. Critically ill patients appear to retain the capacity to absorb dietary protein and to use it for building body protein; however, the extent and possible benefit of this needs to be elucidated. More sophisticated methods to study protein absorption and digestion have recently been described but these have yet to be used in the critically ill.

SUMMARY

Adequate understanding of protein absorption and kinetics during critical illness will help the design of better interventional studies in the future. Because of the complexity of measuring protein absorption and kinetics in the critically ill, very few investigations are executed. Recent data using isotope-labelled amino acids suggests that critically ill patients are able to absorb enteral protein and to synthesize new body protein. However, the magnitude of absorption and anabolism that occurs, and possible benefits for the patients need to be elucidated.

Inhibition of jejunal protein synthesis and breakdown in Pseudomonas aeruginosa-induced sepsis pig model

Maintenance of gut integrity has long been recognized as crucial for survival in sepsis, but alterations in protein metabolism have not previously been documented. Therefore, in the present study, we measured in a Pseudomonas aeruginosa-induced porcine sepsis model fractional protein synthesis (FSR) and breakdown rates (FBR) in jejunal mucosa in a fasted, conscious state. FSR was measured by the incorporation rate of stable tracer amino acid (l-[ring-¹³C₆]phenylalanine) into tissue protein. FBR was determined using the relation between blood arterial enrichment and intracellular enrichment of phenylalanine in consecutive mucosal biopsies after a pulse of l-[¹⁵N]phenylalanine. Additionally, we determined the FSR in jejunum, ileum, liver, muscle, and lung tissue. We found in this sham-controlled acute sepsis pig model (control: n = 9; sepsis: n = 13) that jejunal mucosal protein turnover is reduced with both decreased FSR (control: 3.29 ± 0.22; sepsis: 2.32 ± 0.12%/h, P = 0.0008) and FBR (control: 0.72 ± 0.12; sepsis: 0.34 ± 0.04%/h, P = 0.006). We also found that FSR was unchanged in ileum and muscle, whereas it was higher in the liver (control: 0.87 ± 0.05; sepsis: 1.05 ± 0.06%/h, P = 0.041). Our data, obtained with a translational acute sepsis model, suggest that jejunal mucosal protein metabolism is diminished in acute sepsis. Comparison with other tissues indicates that the most serious acute metabolic changes in sepsis occur in the jejunum rather than the muscle. NEW & NOTEWORTHY In a highly translational acute sepsis model, presented data suggest that jejunal mucosal protein metabolism is diminished in acute sepsis, even if the origin of the sepsis is not located in the gut. Comparison with other tissues indicates that the most serious acute changes in the protein synthesis rates in sepsis occur in the gut rather than the muscle. Therefore, we hypothesize that preventing a compromised gut is critical to maintain gut function during sepsis.

Muscle-specific differences in expression and phosphorylation of the Janus kinase 2/Signal Transducer and Activator of Transcription 3 following long-term mechanical ventilation and immobilization in rats

AIM

Muscle wasting is one of the factors most strongly predicting mortality and morbidity in critically ill intensive care unit (ICU). This muscle wasting affects both limb and respiratory muscles, but the understanding of underlying mechanisms and muscle-specific differences remains incomplete. This study aimed at investigating the temporal expression and phosphorylation of the Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway in muscle wasting associated with the ICU condition to characterize the JAK/STAT proteins and the related changes leading or responding to their activation during exposure to the ICU condition.

METHODS

A novel experimental ICU model allowing long-term exposure to the ICU condition, immobilization and mechanical ventilation, was used in this study. Rats were pharmacologically paralysed by post-synaptic neuromuscular blockade and mechanically ventilated for durations varying between 6 hours and 14 days to study muscle-specific differences in the temporal activation of the JAK/STAT pathway in plantaris, intercostal and diaphragm muscles.

RESULTS

The JAK2/STAT3 pathway was significantly activated irrespective of muscle, but muscle-specific differences were observed in the temporal activation pattern between plantaris, intercostal and diaphragm muscles.

CONCLUSION

The JAK2/STAT3 pathway was differentially activated in plantaris, intercostal and diaphragm muscles in response to the ICU condition. Thus, JAK2/STAT3 inhibitors may provide an attractive pharmacological intervention strategy in immobilized ICU patients, but further experimental studies are required in the study of muscle-specific effects on muscle mass and function in response to both short- and long-term exposure to the ICU condition prior to the translation into clinical research and practice.

An attenuated rate of leg muscle protein depletion and leg free amino acid efflux over time is seen in ICU long-stayers

BACKGROUND

There is extensive documentation on skeletal muscle protein depletion during the initial phase of critical illness. However, for intensive care unit (ICU) long-stayers, objective data are very limited. In this study, we examined skeletal muscle protein and amino acid turnover in patients with a prolonged ICU stay.

METHODS

Patients (n = 20) were studied serially every 8-12 days between days 10 and 40 of their ICU stay as long as patients stayed in the ICU. Leg muscle protein turnover was assessed by measurements of phenylalanine kinetics, for which we employed a stable isotope-labeled phenylalanine together with two-pool and three-pool models for calculations, and results were expressed per 100 ml of leg volume. In addition, leg muscle amino acid flux was studied.

RESULTS

The negative leg muscle protein net balance seen on days 10-20 of the ICU stay disappeared by days 30-40 (p = 0.012). This was attributable mainly to an increase in the de novo protein synthesis rate (p = 0.007). It was accompanied by an attenuated efflux of free amino acids from the leg. Leg muscle protein breakdown rates stayed unaltered (p = 0.48), as did the efflux of 3-methylhistidine. The arterial plasma concentrations of free amino acids did not change over the course of the study.

CONCLUSIONS

In critically ill patients with sustained organ failure and in need of a prolonged ICU stay, the initial high rate of skeletal muscle protein depletion was attenuated over time. The distinction between the acute phase and a more prolonged and more stable phase concerning skeletal muscle protein turnover must be considered in study protocols as well as in clinical practice.

TRIAL REGISTRATION

Australian New Zealand Trial Registry, ACTRN12616001012460 . Retrospectively registered on 1 August 2016.

Pharmacological Therapy for the Prevention and Treatment of Weakness After Critical Illness: A Systematic Review

OBJECTIVES

ICU-acquired weakness is a common complication of critical illness and can have significant effects upon functional status and quality of life. As part of preliminary work to inform the design of a randomized trial of a complex intervention to improve recovery from critical illness, we sought to identify pharmacological interventions that may play a role in this area.

DATA SOURCES

We systematically reviewed the published literature relating to pharmacological intervention for the treatment and prevention of ICU-acquired weakness.

STUDY SELECTION

We searched MEDLINE, EMBASE, CINAHL+, Web of Science, and both U.S. and European trial registries up to July 2014 alongside reviews and reference lists from populations with no age or language restrictions. We included studies that reported a measure of muscle structure or physical function as an outcome measure.

DATA EXTRACTION

We estimated pooled odds ratios and 95% CI using data extracted from published articles or where available, original data provided by the authors. Assessment of bias was performed using the Cochrane Collaboration's risk of bias tool.

DATA SYNTHESIS

Ten studies met the inclusion criteria. The current body of evidence does not support the use of any pharmacological agent in this setting, although maintaining euglycemia may reduce the prevalence of critical illness polyneuropathy.

CONCLUSIONS

At present, no pharmacological intervention can be recommended to prevent or treat ICU-acquired weakness. Further research is required into this field to include more novel agents such as myostatin inhibitors. Challenges in the conduct of research in this area are highlighted.

High protein intake without concerns?

The high fashion in nutrition for the critically ill is to recommend a high protein intake. Several opinion leaders are surfing on this wave, expanding the suggested protein allowance upwards. At the same time, there is no new evidence supporting this change in recommendations. Observational data show that in clinical practice protein intake is most often far below current ESPEN recommendations of 1.2–1.5 g/kg/day. Therefore, it may be in the best interests of our patients just to adhere to that guideline, and not to stretch them upwards for protein intake? Here we give arguments to stay conservative.

Does feeding induce maximal stimulation of protein balance?

PURPOSE OF REVIEW

Muscle wasting is dramatic in critically ill patients and related to worsened outcome. The question is whether this can be prevented or reduced by adequate protein feeding. Recommendations for protein requirements are different between different societies, because of limited and weak evidence. Most studies, on which these recommendations are based, use nitrogen balance as primary outcome. However, nitrogen balance to estimate protein needs over short periods, is not reliable.

RECENT FINDINGS

Studies using tracer methodology to assess the effects of feeding on whole-body protein synthesis, breakdown and balance, show that both adult and pediatric critically ill patients can utilize parenterally and enterally given proteins or amino acids to build body protein, and that the extra amino acids are not oxidized.

SUMMARY

Recent studies show a positive correlation between protein intake and protein balance, with many patients reaching a positive protein balance. However, many questions remain. Especially whether adult patients should have a constant positive protein balance, whether the route of administration affects utilization, which proteins are synthesized and whether these are beneficial, is more protein better and what is the upper limit, and whether a positive protein balance affects clinical outcome?

Protein kinetics in human endotoxaemia and their temporal relation to metabolic, endocrine and proinflammatory cytokine responses

BACKGROUND

Sepsis is associated with profound alterations in protein metabolism. The unpredictable time course of sepsis and the multiplicity of confounding factors prevent studies of temporal relations between the onset of endocrine and proinflammatory cytokine responses and the onset of protein catabolism. This study aimed to determine the time course of whole-body protein catabolism, and relate it to the endocrine, metabolic and cytokine responses in a human endotoxaemia model of early sepsis.

METHODS

Six healthy male volunteers were studied twice in random order, before and for 600 min after administration of either an intravenous bolus of Escherichia coli lipopolysaccharide (LPS) or sterile saline. Whole-body protein synthesis, breakdown and net protein breakdown were measured by amino acid tracer infusion, and related to changes in plasma levels of growth hormone, glucagon, cortisol, insulin-like growth factor (IGF) 1, tumour necrosis factor (TNF) α and interleukin (IL) 6.

RESULTS

Protein synthesis, breakdown and net protein breakdown increased and peaked 120 min after LPS administration (P < 0·001), the alterations persisting for up to 480 min. These peaks coincided with peaks in plasma growth hormone, TNF-α and IL-6 concentrations (P = 0·049, P < 0·001 and P < 0·001 for LPS versus saline), whereas plasma cortisol concentration peaked later. No alterations in plasma insulin or glucagon concentrations, or in the IGF axis were observed during the period of abnormalities of protein metabolism.

CONCLUSION

LPS administration induced an early protein catabolic response in young men and this coincided with changes in plasma growth hormone, TNF-α and IL-6 concentrations, rather than changes in cortisol, glucagon, insulin or the IGF axis. Surgical relevance Sepsis in surgical patients is common and remains associated with substantial mortality. Although sepsis is a heterogeneous condition and its pathophysiology therefore difficult to study, a universal and profound clinical problem is protein catabolism not responsive to nutritional support. Human experimental endotoxaemia is a promising model of clinical sepsis that can be used to elucidate underlying pathophysiology and explore novel therapeutic approaches. This study demonstrates that human experimental endotoxaemia replicates the changes in whole-body protein turnover seen in clinical sepsis. Frequent measurements allowed identification of tumour necrosis factor (TNF) α, interleukin (IL) 6 and growth hormone as putative mediators. Human experimental endotoxaemia is a valid model for further study of mechanisms and putative therapies of catabolism associated with sepsis. In particular, effects of TNF-α and IL-6 blockade should be evaluated.

Proteins and amino acids are fundamental to optimal nutrition support in critically ill patients

Proteins and amino acids are widely considered to be subcomponents in nutritional support. However, proteins and amino acids are fundamental to recovery and survival, not only for their ability to preserve active tissue (protein) mass but also for a variety of other functions. Understanding the optimal amount of protein intake during nutritional support is therefore fundamental to appropriate clinical care. Although the body adapts in some ways to starvation, metabolic stress in patients causes increased protein turnover and loss of lean body mass. In this review, we present the growing scientific evidence showing the importance of protein and amino acid provision in nutritional support and their impact on preservation of muscle mass and patient outcomes. Studies identifying optimal dosing for proteins and amino acids are not currently available. We discuss the challenges physicians face in administering the optimal amount of protein and amino acids. We present protein-related nutrition concepts, including adaptation to starvation and stress, anabolic resistance, and potential adverse effects of amino acid provision. We describe the methods for assessment of protein status, and outcomes related to protein nutritional support for critically ill patients. The identification of a protein target for individual critically ill patients is crucial for outcomes, particularly for specific subpopulations, such as obese and older patients. Additional research is urgently needed to address these issues.

Interventions for preventing critical illness polyneuropathy and critical illness myopathy

BACKGROUND

Critical illness polyneuropathy or myopathy (CIP/CIM) is a frequent complication in the intensive care unit (ICU) and is associated with prolonged mechanical ventilation, longer ICU stay and increased mortality. This is an interim update of a review first published in 2009 (Hermans 2009). It has been updated to October 2011, with further potentially eligible studies from a December 2013 search characterised as awaiting assessment.

OBJECTIVES

To systematically review the evidence from RCTs concerning the ability of any intervention to reduce the incidence of CIP or CIM in critically ill individuals.

SEARCH METHODS

On 4 October 2011, we searched the Cochrane Neuromuscular Disease Group Specialized Register, CENTRAL, MEDLINE, and EMBASE. We checked the bibliographies of identified trials and contacted trial authors and experts in the field. We carried out an additional search of these databases on 6 December 2013 to identify recent studies.

SELECTION CRITERIA

All randomised controlled trials (RCTs), examining the effect of any intervention on the incidence of CIP/CIM in people admitted to adult medical or surgical ICUs. The primary outcome was the incidence of CIP/CIM in ICU, based on electrophysiological or clinical examination. Secondary outcomes included duration of mechanical ventilation, duration of ICU stay, death at 30 and 180 days after ICU admission and serious adverse events from the treatment regimens.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted the data and assessed the risk of bias in included studies.

MAIN RESULTS

We identified five trials that met our inclusion criteria. Two trials compared intensive insulin therapy (IIT) to conventional insulin therapy (CIT). IIT significantly reduced CIP/CIM in the screened (n = 825; risk ratio (RR) 0.65, 95% confidence interval (CI) 0.55 to 0.77) and total (n = 2748; RR 0.70, 95% CI 0.60 to 0.82) population randomised. IIT reduced duration of mechanical ventilation, ICU stay and 180-day mortality, but not 30-day mortality compared with CIT. Hypoglycaemia increased with IIT but did not cause early deaths.One trial compared corticosteroids with placebo (n = 180). The trial found no effect of treatment on CIP/CIM (RR 1.27, 95% CI 0.77 to 2.08), 180-day mortality, new infections, glycaemia at day seven, or episodes of pneumonia, but did show a reduction of new shock events.In the fourth trial, early physical therapy reduced CIP/CIM in 82/104 evaluable participants in ICU (RR 0.62. 95% CI 0.39 to 0.96). Statistical significance was lost when we performed a full intention-to-treat analysis (RR 0.81, 95% CI 0.60 to 1.08). Duration of mechanical ventilation but not ICU stay was significantly shorter in the intervention group. Hospital mortality was not affected but 30- and 180-day mortality results were not available. No adverse effects were noticed.The last trial found a reduced incidence of CIP/CIM in 52 evaluable participants out of a total of 140 who were randomised to electrical muscle stimulation (EMS) versus no stimulation (RR 0.32, 95% CI 0.10 to 1.01). These data were prone to bias due to imbalances between treatment groups in this subgroup of participants. After we imputed missing data and performed an intention-to-treat analysis, there was still no significant effect (RR 0.94, 95% CI 0.78 to 1.15). The investigators found no effect on duration of mechanical ventilation and noted no difference in ICU mortality, but did not report 30- and 180-day mortality.We updated the searches in December 2013 and identified nine potentially eligible studies that will be assessed for inclusion in the next update of the review.

AUTHORS' CONCLUSIONS

There is moderate quality evidence from two large trials that intensive insulin therapy reduces CIP/CIM, and high quality evidence that it reduces duration of mechanical ventilation, ICU stay and 180-day mortality, at the expense of hypoglycaemia. Consequences and prevention of hypoglycaemia need further study. There is moderate quality evidence which suggests no effect of corticosteroids on CIP/CIM and high quality evidence that steroids do not affect secondary outcomes, except for fewer new shock episodes. Moderate quality evidence suggests a potential benefit of early rehabilitation on CIP/CIM which is accompanied by a shorter duration of mechanical ventilation but without an effect on ICU stay. Very low quality evidence suggests no effect of EMS, although data are prone to bias. Strict diagnostic criteria for CIP/CIM are urgently needed for research purposes. Large RCTs need to be conducted to further explore the role of early rehabilitation and EMS and to develop new preventive strategies.

Interventions for preventing critical illness polyneuropathy and critical illness myopathy

BACKGROUND

Critical illness polyneuropathy or myopathy (CIP/CIM) is a frequent complication in the intensive care unit (ICU) and is associated with prolonged mechanical ventilation, longer ICU stay and increased mortality. This is an interim update of a review first published in 2009 (Hermans 2009). It has been updated to October 2011, with further potentially eligible studies from a December 2013 search characterised as awaiting assessment.

OBJECTIVES

To systematically review the evidence from RCTs concerning the ability of any intervention to reduce the incidence of CIP or CIM in critically ill individuals.

SEARCH METHODS

On 4 October 2011, we searched the Cochrane Neuromuscular Disease Group Specialized Register, CENTRAL, MEDLINE, and EMBASE. We checked the bibliographies of identified trials and contacted trial authors and experts in the field. We carried out an additional search of these databases on 6 December 2013 to identify recent studies.

SELECTION CRITERIA

All randomised controlled trials (RCTs), examining the effect of any intervention on the incidence of CIP/CIM in people admitted to adult medical or surgical ICUs. The primary outcome was the incidence of CIP/CIM in ICU, based on electrophysiological or clinical examination. Secondary outcomes included duration of mechanical ventilation, duration of ICU stay, death at 30 and 180 days after ICU admission and serious adverse events from the treatment regimens.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted the data and assessed the risk of bias in included studies.

MAIN RESULTS

We identified five trials that met our inclusion criteria. Two trials compared intensive insulin therapy (IIT) to conventional insulin therapy (CIT). IIT significantly reduced CIP/CIM in the screened (n = 825; risk ratio (RR) 0.65, 95% confidence interval (CI) 0.55 to 0.77) and total (n = 2748; RR 0.70, 95% CI 0.60 to 0.82) population randomised. IIT reduced duration of mechanical ventilation, ICU stay and 180-day mortality, but not 30-day mortality compared with CIT. Hypoglycaemia increased with IIT but did not cause early deaths.One trial compared corticosteroids with placebo (n = 180). The trial found no effect of treatment on CIP/CIM (RR 1.27, 95% CI 0.77 to 2.08), 180-day mortality, new infections, glycaemia at day seven, or episodes of pneumonia, but did show a reduction of new shock events.In the fourth trial, early physical therapy reduced CIP/CIM in 82/104 evaluable participants in ICU (RR 0.62. 95% CI 0.39 to 0.96). Statistical significance was lost when we performed a full intention-to-treat analysis (RR 0.81, 95% CI 0.60 to 1.08). Duration of mechanical ventilation but not ICU stay was significantly shorter in the intervention group. Hospital mortality was not affected but 30- and 180-day mortality results were not available. No adverse effects were noticed.The last trial found a reduced incidence of CIP/CIM in 52 evaluable participants out of a total of 140 who were randomised to electrical muscle stimulation (EMS) versus no stimulation (RR 0.32, 95% CI 0.10 to 1.01). These data were prone to bias due to imbalances between treatment groups in this subgroup of participants. After we imputed missing data and performed an intention-to-treat analysis, there was still no significant effect (RR 0.94, 95% CI 0.78 to 1.15). The investigators found no effect on duration of mechanical ventilation and noted no difference in ICU mortality, but did not report 30- and 180-day mortality.We updated the searches in December 2013 and identified nine potentially eligible studies that will be assessed for inclusion in the next update of the review.

AUTHORS' CONCLUSIONS

There is moderate quality evidence from two large trials that intensive insulin therapy reduces CIP/CIM, and high quality evidence that it reduces duration of mechanical ventilation, ICU stay and 180-day mortality, at the expense of hypoglycaemia. Consequences and prevention of hypoglycaemia need further study. There is moderate quality evidence which suggests no effect of corticosteroids on CIP/CIM and high quality evidence that steroids do not affect secondary outcomes, except for fewer new shock episodes. Moderate quality evidence suggests a potential benefit of early rehabilitation on CIP/CIM which is accompanied by a shorter duration of mechanical ventilation but without an effect on ICU stay. Very low quality evidence suggests no effect of EMS, although data are prone to bias. Strict diagnostic criteria for CIP/CIM are urgently needed for research purposes. Large RCTs need to be conducted to further explore the role of early rehabilitation and EMS and to develop new preventive strategies.

Is combined therapy more effective than growth hormone or hyperbaric oxygen alone in the healing of left ischemic and non-ischemic colonic anastomoses?

OBJECTIVE

Our aim was to investigate the effects of growth hormone (GH), hyperbaric oxygen and combined therapy on normal and ischemic colonic anastomoses in rats.

METHODS

Eighty male Wistar rats were divided into eight groups (n = 10). In the first four groups, non-ischemic colonic anastomosis was performed, whereas in the remaining four groups, ischemic colonic anastomosis was performed. In groups 5, 6, 7, and 8, colonic ischemia was established by ligating 2 cm of the mesocolon on either side of the anastomosis. The control groups (1 and 5) received no treatment. Hyperbaric oxygen therapy was initiated immediately after surgery and continued for 4 days in groups 3 and 4. Groups 2 and 6 received recombinant human growth hormone, whereas groups 4 and 8 received GH and hyperbaric oxygen treatment. Relaparotomy was performed on postoperative day 4, and a perianastomotic colon segment 2 cm in length was excised for the detection of biochemical and mechanical parameters of anastomotic healing and histopathological evaluation.

RESULTS

Combined treatment with hyperbaric oxygen and GH increased the mean bursting pressure values in all of the groups, and a statistically significant increase was noted in the ischemic groups compared to the controls (p<0.05). This improvement was more evident in the ischemic and normal groups treated with combined therapy. In addition, a histopathological evaluation of anastomotic neovascularization and collagen deposition showed significant differences among the groups.

CONCLUSIONS

Combined treatment with recombinant human growth hormone and hyperbaric oxygen resulted in a favorable therapeutic effect on the healing of ischemic colonic anastomoses.

Sparing of muscle mass and function by passive loading in an experimental intensive care unit model

The response to mechanical stimuli, i.e., tensegrity, plays an important role in regulating cell physiological and pathophysiological function, and the mechanical silencing observed in intensive care unit (ICU) patients leads to a severe and specific muscle wasting condition. This study aims to unravel the underlying mechanisms and the effects of passive mechanical loading on skeletal muscle mass and function at the gene, protein and cellular levels. A unique experimental rat ICU model has been used allowing long-term (weeks) time-resolved analyses of the effects of standardized unilateral passive mechanical loading on skeletal muscle size and function and underlying mechanisms. Results show that passive mechanical loading alleviated the muscle wasting and the loss of force-generation associated with the ICU intervention, resulting in a doubling of the functional capacity of the loaded versus the unloaded muscles after a 2-week ICU intervention. We demonstrate that the improved maintenance of muscle mass and function is probably a consequence of a reduced oxidative stress revealed by lower levels of carbonylated proteins, and a reduced loss of the molecular motor protein myosin. A complex temporal gene expression pattern, delineated by microarray analysis, was observed with loading-induced changes in transcript levels of sarcomeric proteins, muscle developmental processes, stress response, extracellular matrix/cell adhesion proteins and metabolism. Thus, the results from this study show that passive mechanical loading alleviates the severe negative consequences on muscle size and function associated with the mechanical silencing in ICU patients, strongly supporting early and intense physical therapy in immobilized ICU patients.

Early rehabilitation in critical care (eRiCC): functional electrical stimulation with cycling protocol for a randomised controlled trial

INTRODUCTION

Intensive care-acquired weakness is a common problem, leads to significant impairment in physical functioning and muscle strength, and is prevalent in individuals with sepsis. Early rehabilitation has been shown to be safe and feasible; however, commencement is often delayed due to a patient's inability to co-operate. An intervention that begins early in an intensive care unit (ICU) admission without the need for patient volition may be beneficial in attenuating muscle wasting. The eRiCC (early rehabilitation in critical care) trial will investigate the effectiveness of functional electrical stimulation-assisted cycling and cycling alone, compared to standard care, in individuals with sepsis.

METHODS AND ANALYSIS

This is a single centre randomised controlled trial. Participants (n=80) aged ≥18 years, with a diagnosis of sepsis or severe sepsis, who are expected to be mechanically ventilated for ≥48 h and remain in the intensive care ≥4 days will be randomised within 72 h of admission to (1) standard care or (2) intervention where participants will receive functional electrical muscle stimulation-assisted supine cycling on one leg while the other leg undergoes cycling alone. Primary outcome measures include: muscle mass (quadriceps ultrasonography; bioelectrical impedance spectroscopy); muscle strength (Medical Research Council Scale; hand-held dynamometry) and physical function (Physical Function in Intensive Care Test; Functional Status Score in intensive care; 6 min walk test). Blinded outcome assessors will assess measures at baseline, weekly, at ICU discharge and acute hospital discharge. Secondary measures will be evaluated in a nested subgroup (n=20) and will consist of biochemical/histological analyses of collected muscle, urine and blood samples at baseline and at ICU discharge.

ETHICS AND DISSEMINATION

Ethics approval has been obtained from the relevant institution, and results will be published to inform clinical practice in the care of patients with sepsis to optimise rehabilitation and physical function outcomes.

TRIAL REGISTRATION

Australian and New Zealand Clinical Trials Registry ACTRN12612000528853.

Protein metabolism and gene expression in skeletal muscle of critically ill patients with sepsis

Muscle wasting negatively affects morbidity and mortality in critically ill patients. This progressive wasting is accompanied by, in general, a normal muscle PS (protein synthesis) rate. In the present study, we investigated whether muscle protein degradation is increased in critically ill patients with sepsis and which proteolytic enzyme systems are involved in this degradation. Eight patients and seven healthy volunteers were studied. In vivo muscle protein kinetics was measured using arteriovenous balance techniques with stable isotope tracers. The activities of the major proteolytic enzyme systems were analysed in combination with mRNA expression of genes related to these proteolytic systems. Results show that critically ill patients with sepsis have a variable but normal muscle PS rate, whereas protein degradation rates are dramatically increased (up to 160%). Of the major proteolytic enzyme systems both the proteasome and the lysosomal systems had higher activities in the patients, whereas calpain and caspase activities were not changed. Gene expression of several genes related to the proteasome system was increased in the patients. mRNA levels of the two main lysosomal enzymes (cathepsin B and L) were not changed but, conversely, genes related to calpain and caspase had a higher expression in the muscles of the patients. In conclusion, the dramatic muscle wasting seen in critically ill patients with sepsis is due to increased protein degradation. This is facilitated by increased activities of both the proteasome and lysosomal proteolytic systems.

Preferential skeletal muscle myosin loss in response to mechanical silencing in a novel rat intensive care unit model: underlying mechanisms

The muscle wasting and impaired muscle function in critically ill intensive care unit (ICU) patients delay recovery from the primary disease, and have debilitating consequences that can persist for years after hospital discharge. It is likely that, in addition to pernicious effects of the primary disease, the basic life support procedures of long-term ICU treatment contribute directly to the progressive impairment of muscle function. This study aims at improving our understanding of the mechanisms underlying muscle wasting in ICU patients by using a unique experimental rat ICU model where animals are mechanically ventilated, sedated and pharmacologically paralysed for duration varying between 6 h and 14 days. Results show that the ICU intervention induces a phenotype resembling the severe muscle wasting and paralysis associated with the acute quadriplegic myopathy (AQM) observed in ICU patients, i.e. a preferential loss of myosin, transcriptional down-regulation of myosin synthesis, muscle atrophy and a dramatic decrease in muscle fibre force generation capacity. Detailed analyses of protein degradation pathways show that the ubiquitin proteasome pathway is highly involved in this process. A sequential change in localisation of muscle-specific RING finger proteins 1/2 (MuRF1/2) observed during the experimental period is suggested to play an instrumental role in both transcriptional regulation and protein degradation. We propose that, for those critically ill patients who develop AQM, complete mechanical silencing, due to pharmacological paralysis or sedation, is a critical factor underlying the preferential loss of the molecular motor protein myosin that leads to impaired muscle function or persisting paralysis.

Protein metabolism in leg muscle following an endotoxin injection in healthy volunteers

The human endotoxin model has been used to study the early phase of sepsis. The aim of the present study was to assess leg muscle protein kinetics after an endotoxin challenge given to healthy human volunteers. Six healthy male subjects were studied in the post-absorptive state before and during 4 h following an intravenous endotoxin bolus (4 ng/kg of body weight). Primed continuous infusion of [2H5]phenylalanine and [2H3]3-methylhistidine in combination with sampling from the radial artery, femoral vein and muscle tissue were used to assess leg muscle protein kinetics. Both two- and three-compartment models were used to calculate protein kinetics. In addition 26S proteasome activity and protein ubiquitination were assessed. An increase in the net release of phenylalanine from the leg following the endotoxin challenge was observed; however, this phenylalanine originates from the free intracellular pool and not from protein. Net protein balance was unchanged, whereas both protein synthesis and breakdown were decreased. Degradation rates of contractile proteins were not affected by endotoxin, as indicated by an unchanged rate of appearance of 3-methylhistidine from leg muscle. In addition, proteasome activity and protein ubiquitination were unaffected by endotoxaemia. In conclusion, intravenous endotoxin administration to healthy volunteers resulted in an increased release of free phenylalanine from skeletal muscle, whereas protein balance was unaffected. Both protein synthesis and breakdown were decreased to a similar extent.

Interventions for preventing critical illness polyneuropathy and critical illness myopathy

BACKGROUND

Critical illness polyneuro-and/or myopathy (CIP/CIM) is an important and frequent complication in the intensive care unit (ICU), causing delayed weaning from mechanical ventilation. It may increase ICU stay and mortality.

OBJECTIVES

To examine the ability of any intervention to prevent the occurrence of CIP/CIM.

SEARCH STRATEGY

We searched the Cochrane Neuromuscular Disease Group Trials Register (October 2007), MEDLINE (January 1950 to April 2008), EMBASE (January 1980 to October 2007), checked bibliographies and contacted trial authors and experts in the field.

SELECTION CRITERIA

All randomised controlled trials (RCTs), examining the effect of any intervention on the incidence of CIP/CIM in adult medical or surgical ICU patients. The primary outcome measure was the incidence of CIP/CIM after at least seven days in ICU, based on electrophysiological or clinical examination.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted the data.

MAIN RESULTS

Three out of nine identified trials, provided data on our primary outcome measure. Two trials examined the effects of intensive insulin therapy versus conventional insulin therapy. Eight hundred and twenty-five out of 2748 patients randomised, were included in the analysis. The incidence of CIP/CIM was significantly reduced with intensive insulin therapy in the population screened for CIP/CIM (relative risk (RR) 0.65, 95% confidence interval (CI) 0.55 to 0.78) and in the total population randomised (RR 0.60, 95% CI 0.49 to 0.74). Duration of mechanical ventilation, duration of ICU stay and 180-day mortality but not 30-day mortality, were significantly reduced with intensive insulin therapy, in both the total and the screened population. Intensive insulin therapy significantly increased hypoglycaemic events and recurrent hypoglycaemia. Death within 24 hours of the hypoglycaemic event was not different between groups. The third trial examined the effects of corticosteroids versus placebo in 180 patients with prolonged acute respiratory distress syndrome. No significant effect of corticosteroids on CIP/CIM was found (RR 1.09, 95% CI 0.53 to 2.26). No effect on 180-day mortality, new serious infections and glycaemia at day seven was found. A trend towards fewer episodes of pneumonia and reduction of new events of shock was shown.

AUTHORS' CONCLUSIONS

Substantial evidence shows that intensive insulin therapy reduces the incidence of CIP/CIM, the duration of mechanical ventilation, duration of ICU stay and 180-day mortality. There was a significant associated increase in hypoglycaemia. Further research needs to identify the clinical impact of this and strategies need to be developed to reduce the risk of hypoglycaemia. Limited evidence shows no significant effect of corticosteroids on the incidence of CIP/CIM, or on any of the other secondary outcome measures, except for a significant reduction of new episodes of shock. Strict diagnostic criteria for the purpose of research should be defined. Other interventions should be investigated in randomised controlled trials.

Enhancement of muscle mitochondrial function by growth hormone

CONTEXT

Although GH promotes growth and protein anabolism, which are ATP-dependent processes, the GH effect on mitochondrial regulation remains to be determined.

OBJECTIVE

Our objective was to determine the acute effect of GH on mitochondrial oxidative capacity in skeletal muscle of healthy subjects.

DESIGN AND SETTING

The study was a randomized crossover design at an academic medical center.

PARTICIPANTS

Nine healthy men and women completed the study.

INTERVENTION

GH (150 microg/h) or saline was infused for 14 h on separate days, and muscle biopsies were obtained.

MAIN OUTCOME MEASURES

Outcome measures included mitochondrial function, gene expression, and protein metabolism.

RESULTS

The 4-fold increase in plasma GH caused elevations in plasma IGF-I, insulin, glucose, and free fatty acids and a shift in fuel selection, with less carbohydrate (-69%) and leucine (-43%) oxidation and 29% more fat oxidation. Muscle mitochondrial ATP production rate and citrate synthase activity were increased 16-35% in response to GH. GH also resulted in higher abundance of muscle mRNAs encoding IGF-I, mitochondrial proteins from the nuclear (cytochrome c oxidase subunit 4) and mitochondrial (cytochrome c oxidase subunit 3) genomes, the nuclear-derived mitochondrial transcription factor A, and glucose transporter 4. Although GH increased whole-body protein synthesis (nonoxidative disposal of leucine), no effect on synthesis rate of muscle mitochondrial proteins was observed.

CONCLUSIONS

These results demonstrate that acute GH action promotes an increase in mitochondrial oxidative capacity and abundance of several mitochondrial genes. These events may occur through direct or indirect effects of GH on intracellular signaling pathways but do not appear to involve a change in mitochondrial protein synthesis rate.

Proteasome proteolytic activity in skeletal muscle is increased in patients with sepsis

Patients with sepsis in the ICU (intensive care unit) are characterized by skeletal muscle wasting. This leads to muscle dysfunction that also influences the respiratory capacity, resulting in prolonged mechanical ventilation. Catabolic conditions are associated with a general activation of the ubiquitin-proteasome pathway in skeletal muscle. The aim of the present study was to measure the proteasome proteolytic activity in both respiratory and leg muscles from ICU patients with sepsis and, in addition, to assess the variation of proteasome activity between individuals and between duplicate leg muscle biopsy specimens. When compared with a control group (n=10), patients with sepsis (n=10) had a 30% (P<0.05) and 45% (P<0.05) higher proteasome activity in the respiratory and leg muscles respectively. In a second experiment, ICU patients with sepsis (n=17) had a 55% (P<0.01) higher proteasome activity in the leg muscle compared with a control group (n=10). The inter-individual scatter of proteasome activity was larger between the patients with sepsis than the controls. We also observed a substantial intra-individual difference in activity between duplicate biopsies in several of the subjects. In conclusion, the proteolytic activity of the proteasome was higher in skeletal muscle from patients with sepsis and multiple organ failure compared with healthy controls. It was shown for the first time that respiratory and leg muscles were affected similarly. Furthermore, the variation in proteasome activity between individuals was more pronounced in the ICU patients for both muscle types, whereas the intra-individual variation between biopsies was similar for ICU patients and controls.

Glutamine and recombinant human growth hormone protect intestinal barrier function following portal hypertension surgery

AIM: To evaluate the effects of combined treatment of glutamine (Gln) and recombinant human growth hormone(rhGH) on intestinal barrier function following portal hypertension surgery.

METHODS: This study was designed as a prospective, randomized and controlled clinical trial. Forty two patients after portal hypertension surgery were randomly assigned into 2 groups: control group (n = 20) and supplemental group (adding Gln and rhGH, n = 22). Every patient received isocaloric and isonitrogenous standard total parenteral nutrition (TPN) starting 3 d after surgery for 7 d. Blood samples were obtained before surgery and at the 3rd and 10th day postoperatively. Host immunity was evaluated by measuring levels of CD4, CD8, CD4/CD8, IgG, IgM and IgA, and the inflammatory responses were determined by assessing IL-2, TNF-α and C-reactive protein (CRP) levels. Intestinal permeability and integrity was evaluated by L/M test and histological examination, respectively.

RESULTS: On postoperative d 10, CD4, CD4/CD8, IgG and IL-2 levels in supplemental group were significantly higher than those in control group (33.7 ± 5.5 vs 31.0± 5.4, P < 0.05, (1.17 ± 0.32 vs 1.05 ± 0.15, P < 0.05, 13.94 ± 1.09 vs 12.33 ± 1.33, P < 0.05, and 368.12± 59.25 vs 318.12 ± 45.65, P < 0.05, respectively), whereas the increase in serum TNF-α concentration was significantly reduced (41.02 ± 27.56 vs 160.09 ± 35.17, P < 0.05). The increase in L/M ratio was significantly lower in the supplemental group than in the control group (0.0166 ± 0.0017 vs 0.0339 ± 0.0028, P < 0.05). Moreover, mucosal integrity in the supplemental group was better than in the control group.

CONCLUSION: Postoperative administration of TPN supplemented with Gln and rhGH in patients after portal hypertension surgery improves immune function, modulates inflammatory response, prevents the intestinal mucous membrane from atrophy and preserves intestinal integrity.

Endocrine modifications and interventions during critical illness

The ongoing hypermetabolic response in patients with prolonged critical illness leads to the loss of lean tissue mass. Since the cachexia of prolonged illness is usually associated with low concentrations of anabolic hormones, hormonal intervention has been thought to be beneficial. However, most interventions have been shown to be ineffective and their indiscriminate use even causes harm. Before considering endocrine intervention in these frail patients, a detailed understanding of the neuroendocrinology of the stress response is warranted. It is now clear that the acute phase and the later phase of critical illness behave differently from an endocrinological point of view. The acute stress reponse consists primarily of an actively-secreting pituitary in the presence of low circulating peripheral anabolic hormones, suggesting resistance of the peripheral tissues to the effects of anterior pituitary hormones. However, when the disease process becomes prolonged, there is a uniformly-reduced pulsatile secretion of anterior pituitary hormones with proportionally reduced concentrations of peripheral anabolic hormones. The origin of this suppressed pituitary secretion is located in the hypothalamus, as hypothalamic secretagogues can reactivate the anterior pituitary and restore pulsatile secretion. The reactivated pituitary secretion is accompanied by an increase in peripheral target hormones, indicating at least partial sensitivity of these tissues to anterior pituitary hormones in this chronic phase of illness. Thus, endocrine intervention with a combination of hypothalamic secretagogues that more completely reactivate the anterior pituitary could be a more physiological and effective strategy for inducing anabolism in patients with prolonged critical illness.

Nutrition support and the chronic critical illness syndrome

Critical illness can be viewed as consisting of 4 distinct stages: (1) acute critical illness (ACI), (2) prolonged acute critical illness, (3) chronic critical illness, and (4) recovery. ACI represents the evolutionarily programmed response to a stressor. In ACI, substrate is shunted away from anabolism and toward vital organ support and inflammatory proteins. Nutrition support in this stage is unproven and may ultimately prove detrimental. As critical illness progresses, there is no evolutionary precedent, and man owes his life to modern critical care medicine. It is at this point that nutrition and metabolic support become integral to the care of the patient. This paper (1) delineates and develops the 4 stages of critical illness using current evidence, clinical experience, and new hypotheses; (2) defines the chronic critical illness syndrome (CCIS); and (3) details an approach to the metabolic and nutrition support of the chronically critically ill patient using the metabolic model of critical illness as a guide. It is our hope that this clinical model can generate testable hypotheses that can improve the outcome of this unique population of patients.

Treatment with GH and IGF-1 in Critical Illness

Trauma, sepsis, and surgery are associated with global hypercatabolism and a negative nitrogen balance. When critical illness is prolonged the relentless loss of lean tissue becomes functionally important. Protein catabolism in the critically ill patient is associated with complex changes in the growth hormone (GH)/insulin-like growth factor-1 (IGF-1) axis. Many small clinical studies indicate that treatment with recombinant human (rh) GH would be a safe and effective means of limiting the deleterious effects of the catabolic response. Unexpectedly, however, two large prospective randomized controlled trials (PRCTs) demonstrated that administration of rhGH to long-stay critically ill adults increases morbidity and mortality. Some progress has been made in understanding the mechanisms underlying this observation.

Endocrine interventions in the ICU

Patients with critical illness, particularly those who depend on intensive care for a prolonged period of time, have a high morbidity and mortality. The acute and chronic phases of critical illness are associated with distinct endocrine alterations. Acute endocrine adaptations to the severe stress of critical illness, comprising an activated anterior pituitary function, have been selected by nature and can, as such, be considered as beneficial for surviving. These adaptations disappear or wane during the prolonged phase of critical illness. In this phase there is a reduced pulsatile secretion of different anterior pituitary hormones and the so-called "wasting syndrome" occurs. This prolonged endocrine/metabolic stress response is quite different from the acute response and may, to some extent, no longer be adaptive. Intervention within the endocrine system, however, remains highly controversial, as it is difficult to differentiate between beneficial adaptations and harmful abnormalities and to outline strategies for therapy. Insulin infusion titrated to maintain normoglycemia may be a notable exception, as this intervention has been proven to increase survival and reduce morbidity of surgical intensive care patients. Treatment of "relative adrenal failure" with hydrocortisone also appears to improve the outcome of patients with septic shock, but diagnostic and dosing issues still remain unresolved. Although extensive research has shown that infusion of hypothalamic-releasing peptides is able to restore physiological hormonal patterns within the somatotropic, thyrotropic, and gonadal axes and, thereby, to generate a controlled anabolic response, further research is needed to investigate whether such interventions actually improve the outcome of critical illness.

Refeeding syndrome in patients with gastrointestinal fistula

OBJECTIVE

Although refeeding syndrome has been well documented in starved patients, obese patients, those with anorexia nervosa, malnourished elderly individuals, and certain postoperative patients, little is known about the presence and the importance of refeeding syndrome in patients with gastrointestinal fistula and insufficient nutrition support over the long term. The objective of this study was to estimate the morbidity of this syndrome in these patients, to assess the safety and efficacy of our graduated refeeding regimen, and to emphasize the importance of this syndrome.

METHODS

One hundred fifty-eight patients with gastrointestinal fistula during the past 2 y were reviewed.

RESULTS

Fifteen of these patients were diagnosed as having refeeding syndrome. They were started on the refeeding procedure according to our regimen, and changes in their serum levels of electrolytes were recorded. The symptoms and signs they presented were noted. All patients were successfully advanced to full nutrition support. During the refeeding procedure, patients presented with weakness, paralysis of limbs, slight dyspnea, paresthesia, tachycardia, edema, and diarrhea. Serum phosphorus concentration decreased in all patients within 24 h of refeeding, reaching a mean nadir after 3.3 +/- 1.5 d and another 6.1 +/- 2.1 d to return to above 0.70 mM/L upon phosphorus supplementation. Three patients treated with growth hormone presented more severe hypophosphatemia (<0.20 mM/L) than the others.

CONCLUSIONS

1) Refeeding syndrome occurs commonly in patients with malnutrition secondary to gastrointestinal fistula. 2) Alterations in phosphate metabolism are central to the refeeding syndrome. 3) Supplementation with electrolytes (including especially phosphate) and vitamins is the focal point of the treatment of this syndrome. 4) Growth hormone treatment may aggravate hypophosphatemia.

Effects on skeletal muscle of intravenous glutamine supplementation to ICU patients

OBJECTIVE

To evaluate the effect of four doses of intravenous glutamine supplementation on skeletal muscle metabolism.

DESIGN

A prospective, blinded, randomized study.

SETTING

The general Intensive Care Unit (ICU) of a university hospital.

PATIENTS

ICU patients with multiple organ failure (n=40), who were expected to stay in the unit for more than five days.

INTERVENTION

Patients received 0, 0.28, 0.57 or 0.86 g of glutamine per kg bodyweight per day intravenously for five days as part of an isocaloric, isonitrogenous and isovolumetric diet.

RESULTS

Plasma glutamine concentration responded to glutamine supplementation with normalization of plasma levels in a dose-dependent way, while free muscle glutamine concentration, as well as muscle protein synthesis and muscle protein content, did not change significantly.

CONCLUSION

Intravenous glutamine supplementation to ICU patients for a period of five days resulted in normalization of plasma glutamine concentrations in a dose-dependent way whereas muscle glutamine concentrations were unaffected.

Combined growth hormone/insulin-like growth factor I in addition to glutamine-supplemented TPN results in net protein anabolism in critical illness

Protein loss leading to reduced lean body mass is recognized to contribute to the high levels of morbidity and mortality seen in critical illness. This prospective, randomized, controlled study compared the effects of conventional parenteral nutrition (TPN), glutamine-supplemented (0.4 g.kg-1.day-1) TPN (TPNGLN), and TPNGLN with combined growth hormone (GH, 0.2 IU.kg-1.day-1) and IGF-I (160 microg.kg-1.day-1) on protein metabolism in critical illness. Nineteen mechanically ventilated subjects [64 +/- 3 yr, body mass index (BMI) 23.8 +/- 1.3, kg/m2] were initially studied in the fasting state (study 1) and subsequently after 3 days of nutritional with/without hormonal support (study 2). All had recently been admitted to the ICU and the majority were postemergency abdominal surgery (APACHE II 17.5 +/- 1.0). Protein metabolism was assessed using a primed constant infusion of [1-13C]leucine. Conventional TPN contained mixed amino acids, Intralipid, and 50% dextrose. TPNGLN, unlike TPN alone, resulted in an increase in plasma glutamine concentration ( approximately 50%, P < 0.05). Both TPN and TPNGLN decreased the rate of protein breakdown (TPN 15%, P < 0.002; TPNGLN 16%, P < 0.05), but during these treatments the patients remained in a net negative protein balance. Combined treatment with TPNGLN + GH/IGF-I increased plasma IGF-I levels (10.3 +/- 0.8 vs. 48.1 +/- 9.1 nmol/l, study 1 vs. study 2, P < 0.05), and in contrast to therapy with nutrition alone, resulted in net protein gain (-0.75 +/- 0.14 vs. 0.33 +/- 0.12 g protein.kg-1.day-1, study 1 vs. study 2, P < 0.05). Therapy with GH/IGF-I + TPNGLN, unlike nutrition alone, resulted in net positive protein balance in a group of critically ill patients.

Glutamine and acute illness

This is a literature review over a time period of the past 2 years concerning glutamine in clinical nutrition. Emphasis is put upon studies of glutamine in clinical settings, but a brief overview of the large range of literature over the role of glutamine in various experimental settings is also included. The most interesting concept for the past 2 years is the suggestion to use plasma glutamine concentration at admission to the intensive care unit as a prognostic marker and as a possible indicator for indication of glutamine supplementation.

Molecular basis of skeletal muscle plasticity--from gene to form and function

Skeletal muscle shows an enormous plasticity to adapt to stimuli such as contractile activity (endurance exercise, electrical stimulation, denervation), loading conditions (resistance training, microgravity), substrate supply (nutritional interventions) or environmental factors (hypoxia). The presented data show that adaptive structural events occur in both muscle fibres (myofibrils, mitochondria) and associated structures (motoneurons and capillaries). Functional adaptations appear to involve alterations in regulatory mechanisms (neuronal, endocrine and intracellular signalling), contractile properties and metabolic capacities. With the appropriate molecular techniques it has been demonstrated over the past 10 years that rapid changes in skeletal muscle mRNA expression occur with exercise in human and rodent species. Recently, gene expression profiling analysis has demonstrated that transcriptional adaptations in skeletal muscle due to changes in loading involve a broad range of genes and that mRNA changes often run parallel for genes in the same functional categories. These changes can be matched to the structural/functional adaptations known to occur with corresponding stimuli. Several signalling pathways involving cytoplasmic protein kinases and nuclear-encoded transcription factors are recognized as potential master regulators that transduce physiological stress into transcriptional adaptations of batteries of metabolic and contractile genes. Nuclear reprogramming is recognized as an important event in muscle plasticity and may be related to the adaptations in the myosin type, protein turnover, and the cytoplasma-to-myonucleus ratio. The accessibility of muscle tissue to biopsies in conjunction with the advent of high-throughput gene expression analysis technology points to skeletal muscle plasticity as a particularly useful paradigm for studying gene regulatory phenomena in humans.

Nutritional papers in ICU patients: what lies between the lines?

The abundance of literature related to nutritional support reflects its recently recognised role in preventing metabolic complications and gut dysfunction during critical illness. However, some published studies lack relevance to critically ill patients, as a result of the selection of subjects and outcome variables, or flaws in the study design, as well as in the type, composition, timing, route of administration and amount of nutritional support given. This review will highlight these confounding factors by describing two imaginary (but typical) clinical trials and by analysing some studies published. The point at issue is that basic quality requirements, such as the formulation of a prospective hypothesis and the delineation of the effects of the reference treatment, are often lacking in many studies published. Data analysis was often found to be biased by the absence of statistical power calculation and intention-to-treat analysis. Globally, studies designed to assess the effects of nutritional support on the outcome of critically ill patients, rarely fulfil basic quality requirements and should therefore be interpreted cautiously. We suggest simple strategies or study design that will allow important questions to be answered by future clinical trials.

Recombinant human growth hormone treatment in elderly patients undergoing elective total hip replacement

OBJECTIVE

Measures to prevent postoperative catabolism may be of greatest benefit in the elderly because of their reduced lean tissue reserve. We examined the effects of recombinant human growth hormone (GH) treatment on body composition and physical performance in elderly patients undergoing elective total hip replacement.

METHODS

We recruited 33 patients (aged 60-82 years) scheduled for hip replacement. The study was double-blind and placebo-controlled with parallel groups. GH or placebo was administered for 14 weeks preoperatively (target GH dose 0.04 U/kg/day) and 4 weeks postoperatively (with dose doubled for first 2 weeks postoperatively). Serum IGF-I, body composition, mid-thigh muscle cross-sectional area, muscle strength and 4-min walking distance were measured at baseline, 2-3 days preoperatively and 4 weeks postoperatively.

RESULTS

Mean serum IGF-I doubled during GH treatment. Lean body mass increased preoperatively by an average of 5.2% (representing 1.8 kg) with GH treatment (P < 0.05 vs. placebo), but fell postoperatively by 3% in both groups. Similar changes pre- and postoperatively were seen for mid-thigh muscle cross-sectional area, such that there was no net loss in the GH group but a fall of more than 10% in the placebo group (P < 0.005 vs. GH). There was a trend towards a favourable effect of GH on strength in the majority of muscles tested, but this was significant only for the abductors of the nonoperated hip (P < 0.02), where there was a 7% increase in strength over the whole study compared with a 25% decrease in the placebo group. Four-minute walking distance improved postoperatively by a mean of 26.9 m in the GH group compared with a 19.5 m reduction in the placebo group (P < 0.05). Dose-related side-effects were seen in the majority of patients receiving GH.

CONCLUSIONS

In elderly patients undergoing total hip replacement, preoperative GH treatment results in improvements in lean body mass and skeletal muscle mass that are sufficient to offset postoperative losses. The treatment may also preserve or improve muscle strength and postoperative walking ability.

Beta-blockade and growth hormone after burn

OBJECTIVE

To determine whether propranolol and growth hormone (GH) have additive effects to combat burn-induced catabolism.

SUMMARY BACKGROUND DATA

Both GH and propranolol have been attributed anabolic properties after severe trauma and burn. It is conceivable that the two in combination would have additive effects.

METHODS

Fifty-six children with more than 40% TBSA burns were randomized to one of four anabolic regimens: untreated control, GH treatment, propranolol treatment, or combination GH plus propranolol therapy. Clinical treatment was identical for all groups. Resting energy expenditure was determined by indirect calorimetry and skeletal muscle protein kinetics were measured using stable amino acid isotope infusions before and after each anabolic regimen.

RESULTS

There were no differences in age, sex, or burn size between groups. Tachycardia and energy expenditure were decreased during propranolol treatment ( <.05). The net balance of muscle protein synthesis and breakdown was improved during propranolol and GH plus propranolol treatment ( <.05). There was no significant benefit of GH alone. No additive effect of combination therapy was seen.

CONCLUSIONS

Propranolol is a strongly anabolic drug during the early, hypercatabolic period after burn. No synergistic effect between propranolol and GH was identified.

Effect of growth hormone on muscle and liver protein synthesis in septic rats receiving glutamine-enriched parenteral nutrition

OBJECTIVE

Administration of recombinant human growth hormone (rhGH) to critically ill adults in an attempt to attenuate catabolism was associated with increased morbidity and mortality. Possible explanations included inhibition of glutamine release from skeletal muscle and consequent restriction of splanchnic glutamine supply. In this study, we examined the effects of rhGH on plasma glutamine levels and on muscle and liver glutamine concentrations and protein synthesis rates in sepsis. We investigated the possibility that administration of supplemental glutamine might ameliorate any adverse effects of rhGH.

DESIGN

Prospective study in rats rendered septic by cecal ligation and puncture.

SETTING

University hospital laboratory.

SUBJECTS

A total of 78 male Wistar rats in six groups.

INTERVENTIONS

Animals received 6-hr tail vein infusions, commencing 18 hrs after cecal ligation and puncture, of either (a) 0.9% sodium chloride, (b) a standard parenteral nutrition (PN) solution without glutamine, or (c) an isocaloric, isonitrogenous PN solution with glutamine. PN groups received 400 microg rhGH or equivolume 0.9% sodium chloride vehicle in a divided subcutaneous and intravenous dose at PN commencement. Sacrifice was at the end of the infusion period. A further group was unoperated and uninfused and killed at 24 hrs as baseline controls.

MEASUREMENTS AND MAIN RESULTS

Glutamine concentrations were measured by fluorometry. Protein synthesis in muscle and liver was measured by a "flooding-dose" technique employing L-[4-H]phenylalanine. Plasma glutamine was increased after cecal ligation and puncture except in the saline and glutamine with rhGH animals. Muscle glutamine was reduced after cecal ligation and puncture and was significantly lower in animals receiving standard PN with rhGH vs. saline alone. Liver glutamine was increased in animals receiving saline and those receiving standard PN with rhGH. PN, with or without glutamine, increased muscle protein synthesis, and the administration of rhGH tended to further increase this effect. Neither PN, glutamine, nor rhGH had an effect on the increased liver protein synthesis characteristic of sepsis.

CONCLUSIONS

In sepsis, increased muscle protein synthesis with PN and rhGH administration is not associated with increased muscle glutamine levels. Administration of rhGH does not result in reduced liver glutamine levels or rates of hepatic protein synthesis. PN containing glutamine was no more efficacious than standard PN at increasing muscle protein synthesis.

Dangers of growth hormone therapy in critically ill patients

Prolonged length of stay is the major challenge for modern intensive care because of the associated morbidity and the impact on resource utilization. Severe trauma or infection is associated with a catabolic response, which is characterized by increased protein turnover and negative nitrogen balance. Severe catabolism leads to end-organ dysfunction and muscular weakness, prolonging the need for mechanical ventilation. Catabolism cannot be prevented with standard parenteral or enteral nutritional formulas. In order to prevent the complications of catabolism in intensive care patients, recombinant growth hormone has been applied as an experimental therapy for two decades in patients requiring parenteral nutrition and in patients with respiratory failure. Administration of recombinant growth hormone has resulted in positive nitrogen balance, and studies in mechanically ventilated patients suggest that it may shorten the need for ventilatory support. In contrast to the results of these relatively small studies, a recent multinational randomized controlled trial revealed that the administration of recombinant growth hormone (with doses 10-20 times higher than used for replacement therapy) increases mortality of critically ill patients. The excessive mortality in patients treated with recombinant growth hormone was related to infections and development of multiple organ failure, leading to the conclusion that administration of high doses of recombinant growth hormone cannot be recommended for critically ill patients. This review reinforces that conclusion.

Management of catabolism in metabolically stressed patients: a literature survey about growth hormone application

In the effort to improve the long-term outcome in critically ill patients, the utilization of anabolic agents, such as human recombinant growth hormone, has been proposed in order to reduce catabolism and improve nutritional status. A recent multicentre study regarding the use of human recombinant growth hormone in intensive care unit patients showed an unexpected increase in the mortality rate in human recombinant growth hormone-treated patients. This finding is in contrast with previous literature data reporting either no differences or an even lower mortality rate with the administration of human recombinant growth hormone. This review evaluates the possible reasons for this dramatic difference in outcomes between the multicentre study and the existing literature. Articles dealing with human recombinant growth hormone administration either in intensive care unit patients (n=26) or in postoperative patients (n=16) have been reviewed. Our analysis suggests that the low caloric intake given to patients enrolled in the multicentre study might have been inadequate to compensate for the hypermetabolism of these patients, and could not support the prolonged and delayed administration of high doses of human recombinant growth hormone. Whether the beneficial metabolic effects of human recombinant growth hormone translate into better clinical outcomes deserves further investigation. In addition, the careful selection of patients to be treated, and close monitoring of both the adequacy of caloric support and modality of human recombinant growth hormone administration would favour the safety of human recombinant growth hormone utilization in critical care settings.

Safety aspects of pharmacological GH therapy in adults

The consequences of "pharmacological" growth hormone administration have been studied in a number of conditions, including those characterized by high rates of catabolism. The majority of studies have reported favourable effects on metabolism but recent reports indicate that GH treatment results in increased mortality in critically ill humans. The objective of the study was to assess the safety of large doses of rhGH therapy in human adults. Original trials were identified by searching MEDLINE (1966-March 2000) and the Cochrane database (2000). References of all identified trials were also inspected for more studies. All relevant trials in which GH had been administered to non-GH-deficient (GHD) adult humans were selected from. Outcomes such as death, clinically significant change in function, change in length of hospital stay or need for treatment, and adverse effects were sought. Studies were selected, quality-assessed and passed suitable for inclusion by two independent reviewers. Those studies that were placebo-controlled with satisfactory randomization were considered for inclusion. Twenty-one reports were included in the review. A wide range of patient groups were studied by a variety of investigators, employing a range of doses and duration of GH treatment. The study protocols differed markedly. The majority of studies were small and were designed and/or powered to enable identification of specific effects on nutritional status, protein metabolism, level of function or quality of life. Only two studies were designed to assess safety issues and mortality. In these, GH treatment was associated with a marked increase in mortality in critically ill ICU patients, with a range of diagnoses. Multi-organ failure and the effects of sepsis/infection accounted for most of the excess mortality. In addition morbidity, in terms of length of ICU stay, was increased by GH administration. Other less marked effects were increased fluid retention and hyperglycaemia as a consequence of GH administration. Functional improvement following GH therapy was documented in some studies. There have been few studies assessing the safety aspects of "pharmacological" GH treatment in adult humans. Two well-designed reports indicate that GH administration results in increased morbidity and mortality in a wide variety of critically ill subjects across a spectrum of age ranges. The mechanism(s) of the GH-associated mortality remain poorly understood. Based on current trial evidence, pharmacological GH treatment cannot be recommended for widespread use in critically ill subjects. Well-conducted and reported randomized trials are still needed to inform practice as to whether GH administration will be safe in specific illness categories.

Of flux and flooding: the advantages and problems of different isotopic methods for quantifying protein turnover in vivo : II. Methods based on the incorporation of a tracer

The most common methods for measuring the incorporation of tracer amino acids into tissue protein are the constant tracer infusion and the flooding dose. The flooding dose is an attractive method for measuring tissue protein synthesis because of its convenience and precision. A primary assumption of the method, that the free amino acid precursor pools are equilibrated with the true precursor pool, aminoacyl-transfer RNA, has recently been validated. When short labelling periods are involved, the large dose of amino acid does not appear to alter protein synthesis. The constant tracer infusion is a satisfactory method from a theoretical point of view, but its use requires the measurement of the protein synthetic precursor pool. The best estimate of the aminoacyl-tRNA precursor pool for the constant infusion method appears to be the acid-soluble tissue pool in muscle and VLDL apolipoprotein B-100 in the liver. The experimental approach chosen for measuring tissue protein synthesis should be dictated by the question being addressed.

Nutritional support in sepsis: still skeptical?

The immediate metabolic response to a septic challenge is probably adaptive, meaning that nutritional interference, mainly via the parenteral route, during this early phase of instability can do more harm than good. During the later phases, a gradual increase in enteral nutrition, at the expense of parenteral nutrition, combined with the administration of nutraceuticals such as glutamine and omega-3 fatty acids, can counteract wasting and modulate the complex inflammatory response and immunosuppression associated with sepsis. In these times of scarce resources, there is an urgent need to clearly document the efficacy of immuno/pharmaconutrients, individually and in combination, enterally or parenterally, before proposing them for routine management of septic patients in the intensive care unit.