Nutrition support and the chronic critical illness syndrome

Managing the Chronically Ventilated Critically Ill Population

Advances in intensive care over the past few decades have significantly improved the chances of survival for patients with acute critical illness. However, this progress has also led to a growing population of patients who are dependent on intensive care therapies, including prolonged mechanical ventilation (PMV), after the initial acute period of critical illness. These patients are referred to as the "chronically critically ill" (CCI). CCI is a syndrome characterized by prolonged mechanical ventilation, myoneuropathies, neuroendocrine disorders, nutritional deficiencies, cognitive and psychiatric issues, and increased susceptibility to infections. It is associated with high morbidity and mortality as well as a significant increase in healthcare costs. In this article, we will review disease burden, outcomes, psychiatric effects, nutritional and ventilator weaning strategies as well as the role of palliative care for CCI with a specific focus on those requiring PMV.

Signals for Muscular Protein Turnover and Insulin Resistance in Critically Ill Patients: A Narrative Review

Sarcopenia in critically ill patients is a highly prevalent comorbidity. It is associated with a higher mortality rate, length of mechanical ventilation, and probability of being sent to a nursing home after the Intensive Care Unit (ICU). Despite the number of calories and proteins delivered, there is a complex network of signals of hormones and cytokines that affect muscle metabolism and its protein synthesis and breakdown in critically ill and chronic patients. To date, it is known that a higher number of proteins decreases mortality, but the exact amount needs to be clarified. This complex network of signals affects protein synthesis and breakdown. Some hormones regulate metabolism, such as insulin, insulin growth factor glucocorticoids, and growth hormone, whose secretion is affected by feeding states and inflammation. In addition, cytokines are involved, such as TNF-alpha and HIF-1. These hormones and cytokines have common pathways that activate muscle breakdown effectors, such as the ubiquitin-proteasome system, calpain, and caspase-3. These effectors are responsible for protein breakdown in muscles. Many trials have been conducted with hormones with different results but not with nutritional outcomes. This review examines the effect of hormones and cytokines on muscles. Knowing all the signals and pathways that affect protein synthesis and breakdown can be considered for future therapeutics.

Nature and impact of in-hospital complications associated with persistent critical illness

Background: Persistent critical illness (PerCI) is defined as an intensive care unit (ICU) admission lasting ≥ 10 days. The in-hospital complications associated with its development are poorly understood. Aims: To test whether PerCI is associated with a greater prevalence, rate and specific types of in-hospital complications. Methods: Single-centre, retrospective, observational case-control study. Results: We studied 1200 patients admitted to a tertiary ICU from 2010 to 2015. Median ICU length of stay was 16 days (interquartile range [IQR], 12-23) for PerCI patients v 2.3 days (IQR, 1.1-3.7) for controls, and median hospital length of stay was 41 days (IQR, 22-75) v 8 days (IQR, 4-17) respectively. A greater proportion of PerCI patients received acute renal replacement therapy (37% v 6.8%) or underwent reintubation (17% v 1%) and/or tracheostomy (36% v 0.6%); P < 0.0001. Despite these complications, PerCI patients had similar hospital mortality (29% v 27%; P = 0.53). PerCI patients experienced a greater absolute number of complications (12.1 v 4.0 complications per patient; P < 0.0001) but had fewer exposure-adjusted complications (202 v 272 complications per 1000 hospital bed-days; P < 0.001) and a particularly high overall prevalence of specific complications. Conclusions: PerCI patients experience a higher prevalence, but not a higher rate, of exposure-adjusted complications. Some of these complications appear amenable to prevention, helping to define intervention targets in patients at risk of PerCI. Funding: Austin Hospital Intensive Care Trust Fund.

Protein delivery in intermittent and continuous enteral nutrition with a protein-rich formula in critically ill patients-a protocol for the prospective randomized controlled proof-of-concept Protein Bolus Nutrition (Pro BoNo) study

Background

Critically ill patients rapidly develop muscle wasting resulting in sarcopenia, long-term disability and higher mortality. Bolus nutrition (30–60 min period), whilst having a similar incidence of aspiration as continuous feeding, seems to provide metabolic benefits through increased muscle protein synthesis due to higher leucine peaks.

To date, clinical evidence on achievement of nutritional goals and influence of bolus nutrition on skeletal muscle metabolism in ICU patients is lacking. The aim of the Pro BoNo study (Protein Bolus Nutrition) is to compare intermittent and continuous enteral feeding with a specific high-protein formula. We hypothesise that target quantity of protein is reached earlier (within 36 h) by an intermittent feeding protocol with a favourable influence on muscle protein synthesis.

Methods

Pro BoNo is a prospective randomised controlled study aiming to compare the impact of intermittent and continuous enteral feeding on preventing muscle wasting in 60 critically ill patients recruited during the first 48 h after ICU admission. The primary outcome measure is the time until the daily protein target (≥ 1.5 g protein/kg bodyweight/24 h) is achieved. Secondary outcome measures include tolerance of enteral feeding and evolution of glucose, urea and IGF-1. Ultrasound and muscle biopsy of the quadriceps will be performed.

Discussion

The Basel Pro BoNo study aims to collect innovative data on the effect of intermittent enteral feeding of critically ill patients on muscle wasting.

Trial registration

ClinicalTrials.gov NCT03587870. Registered on July 16, 2018. Swiss National Clinical Trials Portal SNCTP000003234. Last updated on July 24, 2019.

Pre- and Peri-Operative Factors Associated with Chronic Critical Illness in Liver Transplant Recipients

Background: Chronic critical illness (CCI) is a new and increasing entity that accounts for substantial cost despite its low incidence. We hypothesized that patients with end-stage liver failure undergoing liver transplant would be at high risk for developing CCI. With limited liver donors it is essential to understand pre- and peritransplant predictors of CCI. Methods: To accomplish this we performed a retrospective cohort study at a large academic transplant center of all adult liver transplant patients from 2011 to 2017. We defined CCI as the need for mechanical ventilation for seven days or more post-transplant. Recipients who had re-transplantation during their index admission, acute rejection, or who died during transplant surgery were excluded. Logistic regression was performed using the Akaike information criterion (AIC) and the likelihood ratio test. Results: We identified 382 transplant recipients. Forty-five (11.8%) developed CCI. Univariable analysis identified 16 pre-transplant factors associated with post-transplant CCI. Subsequent multivariable logistic regression identified eight independent factors associated with CCI in liver transplant recipients including previous liver transplant, acute renal failure, frailty, lower albumin level, higher international normalized ratio, need for mechanical ventilation, and higher systolic pulmonary artery pressure. Pre-transplant factors associated with protection against CCI included higher Model for End-Stage Liver Disease (MELD) score. Conclusion: The incidence of CCI post-liver transplant is similar to the general population admitted to the intensive care unit. Pre-transplant factors associated with CCI can help identify at-risk patients, and furthermore, promote further research and interventions with the goal to decrease the incidence of CCI in the liver transplant recipients.

Anterior pituitary function in critical illness

Critical illness is hallmarked by major changes in all hypothalamic-pituitary-peripheral hormonal axes. Extensive animal and human studies have identified a biphasic pattern in circulating pituitary and peripheral hormone levels throughout critical illness by analogy with the fasting state. In the acute phase of critical illness, following a deleterious event, rapid neuroendocrine changes try to direct the human body toward a catabolic state to ensure provision of elementary energy sources, whereas costly anabolic processes are postponed. Thanks to new technologies and improvements in critical care, the majority of patients survive the acute insult and recover within a week. However, an important part of patients admitted to the ICU fail to recover sufficiently, and a prolonged phase of critical illness sets in. This prolonged phase of critical illness is characterized by a uniform suppression of the hypothalamic-pituitary-peripheral hormonal axes. Whereas the alterations in hormonal levels during the first hours and days after the onset of critical illness are evolutionary selected and are likely beneficial for survival, endocrine changes in prolonged critically ill patients could be harmful and may hamper recovery. Most studies investigating the substitution of peripheral hormones or strategies to overcome resistance to anabolic stimuli failed to show benefit for morbidity and mortality. Research on treatment with selected and combined hypothalamic hormones has shown promising results. Well-controlled RCTs to corroborate these findings are needed.

INTRAVENOUS PAMIDRONATE IS ASSOCIATED WITH REDUCED MORTALITY IN PATIENTS WITH CHRONIC CRITICAL ILLNESS

OBJECTIVE

Chronic critical illness (CCI), characterized by prolonged mechanical ventilation and tracheostomy, commonly manifests with elevated bone resorption, which has previously been shown to abate after treatment with intravenous (IV) bisphosphonates. Our study assessed the impact of pamidronate administration on clinical outcomes in a CCI cohort.

METHODS

A retrospective case series was performed on 148 patients admitted to The Mount Sinai Hospital Respiratory Care Unit (RCU) from 2009-2010. We identified patients with CCI who did (n = 30) or did not (n = 118) receive IV pamidronate (30 to 90 mg). Both groups included patients with normal and abnormal renal function. Pamidronate was administered for elevated urine or serum N-telopeptide, hypercalciuria, or hypercalcemia.

RESULTS

RCU and 1-year mortality were significantly lower in the pamidronate group (0 and 20%, respectively) compared to nonreceivers (19 and 56%, respectively) (P = .0077 and P = .0004, respectively). After adjusting for differences in baseline creatinine, estimated glomerular filtration rate, and serum calcium, the association with reduced mortality remained significant at 1 year (P = .0132) and with borderline significance for RCU mortality (P = .0911). Creatinine was significantly lower 7 days following pamidronate administration (P = .0025), with no significant difference at 14 days compared to baseline. Pamidronate receivers showed a greater increase in albumin during the RCU stay (2.49 to 3.23 g/dL), compared to nonreceivers (2.43 to 2.64 g/dL) (P = .0007). Pamidronate administration was associated with a significantly reduced rate of hypoglycemia compared to RCU patients not receiving pamidronate (0.09 versus 0.12; P = .0071).

CONCLUSION

Pamidronate use in a CCI population is associated with reduced mortality, lower hypoglycemia rates, improved albumin, and stable renal function.

ABBREVIATIONS

BMI = body mass index CCI = chronic critical illness CI = confidence interval CKD = chronic kidney disease CTx = C-telopeptide eGFR = estimated glomerular filtration rate ICU = intensive care unit IV = intravenous NTx = N-telopeptide PMV = prolonged mechanical ventilation RCU = respiratory care unit.

The reality of patients requiring prolonged mechanical ventilation: a multicenter study

OBJECTIVE

The number of patients who require prolonged mechanical ventilation increased during the last decade, which generated a large population of chronically ill patients. This study established the incidence of prolonged mechanical ventilation in four intensive care units and reported different characteristics, hospital outcomes, and the impact of costs and services of prolonged mechanical ventilation patients (mechanical ventilation dependency ≥ 21 days) compared with non-prolonged mechanical ventilation patients (mechanical ventilation dependency < 21 days).

METHODS

This study was a multicenter cohort study of all patients who were admitted to four intensive care units. The main outcome measures were length of stay in the intensive care unit, hospital, complications during intensive care unit stay, and intensive care unit and hospital mortality.

RESULTS

There were 5,287 admissions to the intensive care units during study period. Some of these patients (41.5%) needed ventilatory support (n = 2,197), and 218 of the patients met criteria for prolonged mechanical ventilation (9.9%). Some complications developed during intensive care unit stay, such as muscle weakness, pressure ulcers, bacterial nosocomial sepsis, candidemia, pulmonary embolism, and hyperactive delirium, were associated with a significantly higher risk of prolonged mechanical ventilation. Prolonged mechanical ventilation patients had a significant increase in intensive care unit mortality (absolute difference = 14.2%, p < 0.001) and hospital mortality (absolute difference = 19.1%, p < 0.001). The prolonged mechanical ventilation group spent more days in the hospital after intensive care unit discharge (26.9 ± 29.3 versus 10.3 ± 20.4 days, p < 0.001) with higher costs.

CONCLUSION

The classification of chronically critically ill patients according to the definition of prolonged mechanical ventilation adopted by our study (mechanical ventilation dependency ≥ 21 days) identified patients with a high risk for complications during intensive care unit stay, longer intensive care unit and hospital stays, high death rates, and higher costs.

Nutrition rehabilitation in the intensive care unit

The maintenance of homeostasis after severe injury requires the restoration of the physiological regulation of food intake. A wide array of functional alterations can hinder the intake of adequate amounts of nutrients to support the recovery from critical illness. These alterations encompass changes in the preprandial phase, reflected by a loss of appetite; changes in the prandial phase, yielding swallowing disorders; and changes in the postprandial phase, including impairments of gastric emptying, gut motility, and satiety. This tutorial aims to review these often overlooked features and to suggest recommendations for the nutrition rehabilitation of the critically ill.

IGF-1, the cross road of the nutritional, inflammatory and hormonal pathways to frailty

The decline in functional capacity is a heterogeneous phenomenon in the elderly. An accelerated ageing determines a frail status. It results in an increased vulnerability to stressors for decreased physiological reserves. The early identification of a frail status is essential for preventing loss of functional capacity, and its clinical consequences. Frailty and mobility limitation result from an interplay of different pathways including multiple anabolic deficiency, inflammation, oxidative stress, and a poor nutritional status. However, the age-related decline in insulin-like growth factor 1 (IGF-1) bioactivity deserves special attention as it could represent the ideal crossroad of endocrine, inflammatory, and nutritional pathways to frailty. Several minerals, namely magnesium, selenium, and zinc, appear to be important determinants of IGF-1 bioactivity. This review aims to provide an overview of the potential usefulness of nutrients modulating IGF-1 as potential therapeutic targets in the prevention of mobility limitation occurring in frail older subjects.

Appropriate protein provision in critical illness: a systematic and narrative review

BACKGROUND

Widely varying recommendations have been published with regard to the appropriate amount of protein or amino acids to provide in critical illness.

OBJECTIVE

We carried out a systematic review of clinical trials that compared the metabolic or clinical effects of different protein intakes in adult critical illness and comprehensively reviewed all of the available evidence pertinent to the safe upper limit of protein provision in this setting.

DESIGN

MEDLINE was searched for clinical trials published in English between 1948 and 2012 that provided original data comparing the effects of different levels of protein intake on clinically relevant outcomes and evidence pertinent to the safe upper limit of protein provision to critically ill adults.

RESULTS

The limited amount and poor quality of the evidence preclude conclusions or clinical recommendations but strongly suggest that 2.0-2.5 g protein substrate · kg normal body weight⁻¹ · d⁻¹ is safe and could be optimum for most critically ill patients. At the present time, most critically ill adults receive less than half of the most common current recommendation, 1.5 g protein · kg⁻¹ · d⁻¹, for the first week or longer of their stay in an intensive care unit.

CONCLUSION

There is an urgent need for well-designed clinical trials to identify the appropriate level of protein provision in critical illness.

Nutrition management for the patient requiring prolonged mechanical ventilation

Patients requiring prolonged mechanical ventilation are often medically complex and present with a wide range of pulmonary conditions, including neuromuscular diseases, chronic pulmonary diseases, and chronic critical illness. These patients present the nutrition support professional with many challenges. However, accurate nutrition assessment, timely and effective nutrition interventions, and careful monitoring will help patients meet their medical and nutrition goals.

Physiotherapy in critically ill patients

Prolonged stay in Intensive Care Unit (ICU) can cause muscle weakness, physical deconditioning, recurrent symptoms, mood alterations and poor quality of life. Physiotherapy is probably the only treatment likely to increase in the short- and long-term care of the patients admitted to these units. Recovery of physical and respiratory functions, coming off mechanical ventilation, prevention of the effects of bed-rest and improvement in the health status are the clinical objectives of a physiotherapy program in medical and surgical areas. To manage these patients, integrated programs dealing with both whole-body physical therapy and pulmonary care are needed. There is still limited scientific evidence to support such a comprehensive approach to all critically ill patients; therefore we need randomised studies with solid clinical short- and long-term outcome measures.

Impaired postoperative hyperglycemic stress response associated with increased mortality in patients in the cardiothoracic surgery intensive care unit

OBJECTIVE

To describe the association of tight glycemic control with intensive insulin therapy and clinical outcome among patients in the cardiothoracic surgery intensive care unit.

METHODS

All patients who underwent cardiothoracic surgery and were admitted to the cardiothoracic surgery intensive care unit between September 13, 2007, and November 1, 2007, were enrolled. Clinical and metabolic data were prospectively collected. All patients received intensive insulin therapy using a nurse-driven dynamic protocol targeting blood glucose values of 80 to 110 mg/dL. Four stages of critical illness were defined as follows: acute critical illness (intensive care unit days 0-2), prolonged acute critical illness (intensive care unit 3 or more days), chronic critical illness (tracheotomy performed), and recovery (liberated from ventilator).

RESULTS

One hundred fourteen patients were enrolled. Seventy-three (64%) recovered during acute critical illness, 26 (23%) recovered during prolonged acute critical illness, and 15 (13%) progressed to chronic critical illness. All 6 deaths were among patients in chronic critical illness. Admission blood glucose and average blood glucose values for the first 12 hours were lower in patients who developed chronic critical illness and died and were higher in patients who developed chronic critical illness and survived (P = .007 and P = .007, respectively). Severe hypoglycemia (blood glucose <40 mg/dL) occurred once (0.03% of all measurements). Lower initial blood glucose values, which reflect an impaired stress response immediately after surgery, were associated with increased mortality, and a significant delay in achieving tight glycemic control with intensive insulin therapy was associated with prolonged intensive care unit course, but no increase in mortality.

CONCLUSION

The study findings suggest that acute postoperative hyperglycemia and its prompt correction with intensive insulin therapy are associated with favorable outcomes in patients in the cardiothoracic surgery intensive care unit.

Glycemic control and nutritional strategies in the cardiothoracic surgical intensive care unit--2010: state of the art

Patients in the cardiothoracic surgical intensive care unit are generally critically ill and undergoing a systemic inflammatory response to cardiopulmonary bypass, ischemia/reperfusion, and hypothermia. This presents several metabolic challenges: hyperglycemia in need of intensive insulin therapy, catabolism, and uncertain gastrointestinal tract function in need of nutritional strategies. Currently, there are controversies surrounding the standard use of intensive insulin therapy and appropriate glycemic targets as well as the use of early enteral nutrition ± parenteral nutrition. In this review, an approach for intensive metabolic support in the cardiothoracic surgical intensive care unit is presented incorporating the most recent clinical evidence. This approach advocates an IIT blood glucose target of 80-110 mg/dL if, it can be implemented safely, with early nutrition support (using parenteral nutrition as needed) to prevent a critical energy debt.

The difficult-to-wean patient

Up to 20% of patients requiring mechanical ventilation will suffer from difficult weaning (the need of more than 7 days of weaning after the first spontaneous breathing trial), which may depend on several reversible causes: respiratory and/or cardiac load, neuromuscular and neuropsychological factors, and metabolic and endocrine disorders. Clinical consequences (and/or often causes) of prolonged mechanical ventilation comprise features such as myopathy, neuropathy, and body composition alterations and depression, which increase the costs, morbidity and mortality of this. These difficult-to-wean patients may be managed in two type of units: respiratory intermediate-care units and specialized regional weaning centers. Two weaning protocols are normally used: progressive reduction of ventilator support (which we usually use), or progressively longer periods of spontaneous breathing trials. Physiotherapy is an important component of weaning protocols. Weaning success depends strongly on patients&#x2019; complexity and comorbidities, hospital organization and personnel expertise, availability of early physiotherapy, use of weaning protocols, patients&#x2019; autonomy and families&#x2019; preparation for home discharge with mechanical ventilation.

Understanding, recognizing, and managing chronic critical illness syndrome

PURPOSE

No evidence-based guidelines exist for the care of patients with chronic critical illness syndrome (CCIS), a growing population of patients being cared for by nurse practitioners (NPs). The purpose of this article is to provide NPs with a beginning physiological framework, allostasis, to guide their understanding and management of patients with CCIS.

DATA SOURCES

Scientific publications, related clinical guidelines.

CONCLUSIONS

Patients with CCIS are a distinct group of critically ill patients whose care needs are different from those of patients who are acutely critically ill. These patients demonstrate widespread tissue and organ damage. The widespread tissue and organ damage results in a syndrome of interrelated elements, which include neuroendocrine problems, severe malnutrition, wounds, infections, bone loss, polyneuropathy and myopathy, delirium and depression, and suffering.

IMPLICATIONS FOR PRACTICE

In caring for patients with CCIS, NPs need to focus on treating the elements of the syndrome as a cohort of interrelated elements and on re-establishing normalcy for the patient.

Bone physiology and therapeutics in chronic critical illness

Modern medical practices allow patients to survive acute insults and be sustained by machinery and medicines for extended periods of time. We define chronic critical illness as a later stage of prolonged critical illness that requires tracheotomy. These patients have persistent elevations of inflammatory cytokines, diminished hypothalamic-pituitary function, hypercatabolism, immobilization, and malnutrition. The measurement of bone turnover markers reveals markedly enhanced osteoclastic bone resorption that is uncoupled from osteoblastic bone formation. We review the mechanisms by which these factors contribute to the metabolic bone disease of chronic critical illness and suggest potential therapeutics.

Chronic critical illness

Although advances in intensive care have enabled more patients to survive an acute critical illness, they also have created a large and growing population of chronically critically ill patients with prolonged dependence on mechanical ventilation and other intensive care therapies. Chronic critical illness is a devastating condition: mortality exceeds that for most malignancies, and functional dependence persists for most survivors. Costs of treating the chronically critically ill in the United States already exceed $20 billion and are increasing. In this article, we describe the constellation of clinical features that characterize chronic critical illness. We discuss the outcomes of this condition including ventilator liberation, mortality, and physical and cognitive function, noting that comparisons among cohorts are complicated by variation in defining criteria and care settings. We also address burdens for families of the chronically critically ill and the difficulties they face in decision-making about continuation of intensive therapies. Epidemiology and resource utilization issues are reviewed to highlight the impact of chronic critical illness on our health care system. Finally, we summarize the best available evidence for managing chronic critical illness, including ventilator weaning, nutritional support, rehabilitation, and palliative care, and emphasize the importance of efforts to prevent the transition from acute to chronic critical illness. As steps forward for the field, we suggest a specific definition of chronic critical illness, advocate for the creation of a research network encompassing a broad range of venues for care, and highlight areas for future study of the comparative effectiveness of different treatment venues and approaches.

Intensive metabolic support: evolution and revolution

OBJECTIVE

To describe a new aspect of critical care termed intensive metabolic support.

METHODS

We performed a MEDLINE search of the English-language literature published between 1995 and 2008 for studies regarding the metabolic stages of critical illness, intensive insulin treatment, and intensive metabolic support in the intensive care unit, and we summarize the clinical data.

RESULTS

Intensive metabolic support is a 3-component model involving metabolic control and intensive insulin therapy, early nutrition support, and nutritional pharmacology aimed at preventing allostatic overload and the development of chronic critical illness. To improve clinical outcome and prevent mortality, intensive metabolic support should start on arrival to the intensive care unit and should end only when patients are in the recovery phase of their illness.

CONCLUSIONS

Intensive metabolic support should be an essential part of the daily treatment strategy in critical care medicine. This will involve a newfound and extensive collaboration between the endocrinologist and the intensivist. We call for well-designed future studies involving implementation of this protocol to decrease the burden of chronic critical illness.

Bisphosphonates and metabolic bone disease in the ICU

PURPOSE OF REVIEW

The purpose of this review is to discuss the elements of critical illness that predispose to rapid and severe bone loss and illustrate how potent nitrogen containing intravenous bisphosphonates can mitigate this potentially serious disease.

RECENT FINDINGS

Recent studies confirm that inflammatory cytokines, immobilization, and hormonal irregularities incite osteoclast-mediated bone resorption. Bisphosphonates are antiresorptive agents and well suited to treat this bone loss. Intravenous bisphosphonates have long been considered safe, but recent evidence has raised concerns in regard to such serious side effects as atrial fibrillation, osteonecrosis of the jaw, and 'frozen bone'.

SUMMARY

Metabolic bone disease in the ICU is potentially a devastating consequence of critical illness. Screening with biochemical markers of bone turnover may allow identification of those most likely to have fracture after ICU discharge. Intravenous bisphosphonates are safe and very effective at preventing osteoporotic fracture in other populations. There is likely a subset of individuals who remain critically ill for a prolonged period of time that may benefit from an intravenous infusion of a potent aminobisphosphonate.

Impact of new technologies on metabolic care in the intensive care unit

PURPOSE OF REVIEW

Technological innovations in the ICU have lead to extraordinary advances in modern critical care. Renal replacement therapy (RRT) innovations and ventricular assist devices (VAD) are now becoming common interventions in the ICU environment. The purpose of this article is to describe the impact of RRT and VAD on critical care medicine with particular reference to metabolic care.

RECENT FINDINGS

Continuous venovenous hemofiltration and slow low efficient daily dialysis are effective modalities of RRT in hemodynamically unstable patients. These continuous forms of RRT can result in accentuated protein and nutrient losses but also provide an opportunity for intradialytic parenteral nutrition support. VAD patients typically have cardiac cachexia and develop chronic critical illness syndrome. Intensive metabolic support, incorporating trophic, concentrated, semielemental enteral nutrition, supplemental parenteral nutrition, and intensive insulin therapy is a rational strategy to implement in VAD patients. Unfortunately, there is insufficient evidence at this time to support the routine use of these nutritional interventions with RRT and VAD.

SUMMARY

Patients requiring RRT or VAD are at high nutritional risk, which negatively affects ICU outcome. Prompt nutritional risk assessment and early optimization of metabolic care is crucial in this patient population.

Arginine, scurvy and Cartier's "tree of life"

Several conifers have been considered as candidates for "Annedda", which was the source for a miraculous cure for scurvy in Jacques Cartier's critically ill crew in 1536. Vitamin C was responsible for the cure of scurvy and was obtained as an Iroquois decoction from the bark and leaves from this "tree of life", now commonly referred to as arborvitae. Based on seasonal and diurnal amino acid analyses of candidate "trees of life", high levels of arginine, proline, and guanidino compounds were also probably present in decoctions prepared in the severe winter. The semi-essential arginine, proline and all the essential amino acids, would have provided additional nutritional benefits for the rapid recovery from scurvy by vitamin C when food supply was limited. The value of arginine, especially in the recovery of the critically ill sailors, is postulated as a source of nitric oxide, and the arginine-derived guanidino compounds as controlling factors for the activities of different nitric oxide synthases. This review provides further insights into the use of the candidate "trees of life" by indigenous peoples in eastern Canada. It raises hypotheses on the nutritional and synergistic roles of arginine, its metabolites, and other biofactors complementing the role of vitamin C especially in treating Cartier's critically ill sailors.

Early nutrition support in the intensive care unit: a US perspective

PURPOSE OF REVIEW

Early nutrition support, defined as within the first 24-48 h of ICU care, is recommended by clinical practice guidelines. The purpose of this paper is to provide an evidence-based US perspective on early nutrition support in critical illness, explain its mechanism of action, and describe its implementation using combined enteral and parenteral nutrition support.

RECENT FINDINGS

Recent American and Canadian guidelines recommend starting enteral nutrition within the first 24-48 h of ICU care. This is mainly due to accrued 'energy debt' from underfeeding in certain patients. This energy debt leads to increased risks of complications and longer lengths of stay. Strong clinical evidence, however, in the form of prospective, randomized, controlled intervention studies of early nutrition support in the setting of routine intensive insulin therapy, is lacking.

SUMMARY

Early enteral nutrition should be first-line therapy in the ICU. If a caloric goal of 20-25 kcal/kg/day is not possible, then combined enteral and parenteral nutrition should be started. In the new age of intensive insulin therapy, parenteral nutrition has not been shown to confer significant additional infective risk. There are many unanswered questions, but a proactive posture for metabolic support in the ICU is advocated.