Oxygen transport

The maintenance of adequate oxygen delivery to the tissues is essential in the care of critically ill patients, however, there is debate over what that level of oxygen delivery should been or how best to assess the adequacy of tissue oxygenation. Survival amongst critically ill patients is closely related to the ability to maintain a high cardiac output, oxygen delivery and oxygen consumption. This fact led to the hypothesis that increasing oxygen delivery could decrease oxygen debt and reduce mortality. Clinical trials have been designed to investigate whether intervention to increase oxygen delivery leads to a reduction in mortality in high-risk surgical, trauma and critically ill patients. These trials have shown mixed results, though there is a consensus view that aggressive attempts to increase oxygen delivery in all critically ill patients is not justified.It has been hypothesized that organ failure in critically ill patients may be due to a failure of oxygen utilization rather than oxygen delivery. There is a considerable amount of research demonstrating that mitochondrial dysfunction may arise in sepsis, through a variety of mechanisms, resulting in impaired oxygen consumption. Recent work has suggested that oxygen utilization and metabolic efficiency may be influenced by genetic factors. (c) 1999 Harcourt Publishers Ltd     

New-onset atrial fibrillation in critically ill adult patients—an SSAI clinical practice guideline

Background

Acute or new-onset atrial fibrillation (NOAF) is the most common cardiac arrhythmia in critically ill adult patients, and observational data suggests that NOAF is associated to adverse outcomes.

Methods

We prepared this guideline according to the Grading of Recommendations Assessment, Development and Evaluation methodology. We posed the following clinical questions: (1) what is the better first-line pharmacological agent for the treatment of NOAF in critically ill adult patients?, (2) should we use direct current (DC) cardioversion in critically ill adult patients with NOAF and hemodynamic instability caused by atrial fibrillation?, (3) should we use anticoagulant therapy in critically ill adult patients with NOAF?, and (4) should critically ill adult patients with NOAF receive follow-up after discharge from hospital? We assessed patient-important outcomes, including mortality, thromboembolic events, and adverse events. Patients and relatives were part of the guideline panel.

Results

The quantity and quality of evidence on the management of NOAF in critically ill adults was very limited, and we did not identify any relevant direct or indirect evidence from randomized clinical trials for the prespecified PICO questions. We were able to propose one weak recommendation against routine use of therapeutic dose anticoagulant therapy, and one best practice statement for routine follow-up by a cardiologist after hospital discharge. We were not able to propose any recommendations on the better first-line pharmacological agent or whether to use DC cardioversion in critically ill patients with hemodynamic instability induced by NOAF. An electronic version of this guideline in layered and interactive format is available in MAGIC: https://app.magicapp.org/#/guideline/7197 .

Conclusions

The body of evidence on the management of NOAF in critically ill adults is very limited and not informed by direct evidence from randomized clinical trials. Practice variation appears considerable.     

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??Complication of nutrition therapy for critically ill patients WU Wu-lin, LIN Feng. Department of Gastrointestinal Surgery, People’s Hospital of Guangdong Province, Guangzhou 510080, China
Corresponding author ??LIN Feng??E-mail??wuwulin@medmail.com.cn
Abstract Parenteral nutrition is associated with mechanical, metabolic and infectious complications. Infections are not uncommon and are associated with refractory hyperglycemia caused by stress response. Hyperglycemia is one of the metabolism characteristics in critically ill patients. Patents performed enteral nutrition treatment have a relative low incidence of metabolic and infectious complications. One of the most important infectious complications is aspiration pneumonia. Risk factors that significantly correlated with pneumonia were low bed backrest, vomiting, gastric feedings, a Glasgow Coma Scale score <9, gastroesophageal reflux disease, high sedation level and the use of paralytic agents. Gastrointestinal complications are very common in enterally fed patients. The reasons causing gastrointestinal complications are complex, and medication should be based on different reasons.     

Hyperglycemia in critically ill patients: clinical implications for treatment

Hyperglycemia is frequent during critical illness and is perceived by the clinician as part of the systemic metabolic response to stress. Of all patients with "stress hyperglycemia" only one third are known to have diabetes mellitus. Previous studies reported that patients presenting hyperglycemia during acute illness have an increased risk for nosocomial infections. Morbidity and mortality also increases in patients with myocardial infarction or stroke who develop hyperglycemia. Contemporary medical practice states that hyperglycemia under these conditions should only be treated with insulin if blood glucose levels are > 200 mg/dl. A recent trial showed that intensive insulin treatment of critically ill patients in the intensive care unit with the goal of maintaining blood glucose levels between 80 and 110 mg/dl significantly reduced morbidity and mortality without significant risk of hypoglycemia. These benefits of insulin treatment are not yet well understood, but some pathophysiological evidence suggests that hyperglycemia contributes to perpetuate the systemic proinflammatory response, and insulin--a natural endogenous hormone that has a major role in the intermediary metabolism--participates actively in the systemic anti-inflammatory response. As a result of these findings, we recommend that hyperglycemia during critical illness should be treated with insulin, in order to achieve blood glucose levels in a normal range, regardless of whether or not these patients have diabetes mellitus.     

Metabolic support of the critically ill: 2008 update

Nutrition support in critically ill patients is not merely simple nutrition, but rather metabolic support. In the last few years, the pharmacological properties of nutrients have been specifically addressed in a new field called pharmaconutrition. This review will offer a deeper insight into this field, focusing on the properties of arginine, glutamine, antioxidants, and omega-3 fatty acids as well as the level of blood glycemia which should be maintained in critically ill patients.     

Gastrointestinal dysfunction

Gastrointestinal dysfunction is common in critically ill patients and it is important to try to prevent or manage its manifestations. In this article we discuss the aetiology, management and prevention of: stress ulceration, ileus, bacterial translocation, intra-abdominal hypertension, abdominal compartment syndrome, diarrhoea and constipation in the context of critically ill patients. We also discuss feeding strategies for intensive care patients who cannot be fed normally.     

围手术期血糖调控的科学原理和临床意义

大手术后高血糖的发生是很普遍的现象,并且该现象受很多因素调控.这些因素包括手术期间患者的代谢状况、手术中管理以及患者对外科手术的神经内分泌应激反应.此外围手术期的急性胰岛素抵抗也是发生高血糖症的重要因素.高血糖症的发生还与危重患者及手术患者的预后不良相关.大部分的研究文献已广泛地提到“高血糖”这个概念并尝试了各种途径的...     

Albumine dans les états infectieux graves

Human serum albumin is a small (66 kD) globular protein representing over 60 % of the total plasma protein content. It is made up of 585 amino 6 acids and contains 35 cysteine residues forming disulfide bridges that contribute to its overall tertiary structure. It has a free cysteine-derived thiol group at Cys-34, which accounts for 80 % of its redox activity. Physiologically, serum albumin exists in a reduced form with a free thiol contributing to its antioxidant properties. It is synthesized primarily in the liver and is an acute-phase protein. It is a multifunctional plasma protein ascribed ligand-binding and transport properties as well as antioxidants and enzymatic functions. It maintains colloid osmotic pressure, modulates inflammatory response and may influence oxidative damage. Hypoalbuminemia is common in the intensive care unit and may be due to decreased synthesis by the liver and/or to increased losses or increased proteolysis and clearance. Although albumin was long used to control vascular collapse in critically ill patients, the evidence suggests that it does not offer a benefit over crystalloid solutions in vascular collapse. However, human serum albumin is an important circulating antioxidant and it may be beneficial in critically ill patients to limit oxidative damage. A number of studies suggest that in specific groups of hypoalbuminemic critically ill patients, albumin administration may have beneficial effects on organ function, although the exact mechanisms remain undefined. Further trials are needed to confirm theses observations and to clearly demonstrate whether albumin should be administered in critically ill patients with hypoalbuminemia.     

Clinical nutrition in liver and pancreatic diseases

According to international and national surveys, 5-15% of patients admitted to hospitals require partial or total artificial nutrition. The development or progression of malnutrition influences patients' lives significantly and also increases the costs of their treatment substantially and unnecessarily. Nutrition therapy, meaning a balanced intake of food or provision of nutrients, is an essential part of the critically ill patient's care. The proper concern of physicians today is not whether nutritional support is indicated in hepatic and pancreatic diseases, but when and how it should be given. Author, therefore, gives guidelines to the nutritional therapy of patients suffering from liver and pancreatic diseases since their metabolic support still remains the most challenging problems in clinical nutrition.     

Drug Dosing During Continuous Renal Replacement Therapy

Continuous renal replacement therapy (CRRT) has given clinicians an important option in the care of critically ill patients. The slow and continuous dialysate and ultrafiltrate flow rates that are employed with CRRT can yield drug clearances similar to an analogous glomerular filtration rate of the native kidneys. Advantages such as superior volume control, excellent metabolic control, and hemodynamic tolerance by critically ill patients are well documented, but an understanding of drug dosing for CRRT is still a bit of a mystery. Although some pharmaceutical companies have dedicated postmarket research in this direction, many pharmaceutical companies have chosen not to pursue this information as it is not mandated and represents a relatively small part of their market. This lack of valuable information has created many challenges in the care of the critically ill patient as intermittent hemodialysis drug dosing recommendations cannot be extrapolated to CRRT. This drug dosing review will highlight factors that clinicians should consider when determining a pharmacotherapy regimen for a patient receiving CRRT.     

Analgesia and sedation in intensive care patients]

Analgesia and sedation with the associated reduction of undesired vegetative reactions are important components in the therapeutic regimen of intensive care patients. None of the sedative drugs available can fulfil every one of the criteria expected of an "ideal" sedative. Four commonly used drug combinations have been established as standards: 1. opioid and neuroleptic, 2. opioid and benzodiazepine, 3. ketamine and benzodiazepine, and 4. opioid and propofol. In everyday use one must take not only the specific side-effects of a drug into consideration but also its pharmacokinetic properties. These are often markedly altered in critically ill patients who have impaired functions of vital organs. The pharmacokinetics of a drug is affected by disturbed renal or hepatic function, interactions with other drugs, altered protein binding and the induction or inhibition of metabolic enzymes. The best method of drug administration is by motor-driven pump, with which large fluctuations of the dosage can be avoided. Constant ratios of drug combinations are not recommended, since the pharmacokinetics of each drug is affected to a different degree in the critically ill patient. Withdrawal symptoms, can occur for example after prolonged administration of benzodiazepines, can often be avoided by slowly reducing the dose or by switching to a short-acting substance. In some patients (e.g. those with a history of alcohol abuse) a massive increase of the drug dose is not indicated when the effect is not adequate. Instead, an entirely different substance should be employed and the administration of less frequently used drugs should be considered. Despite detailed knowledge of the altered pharmacokinetics in critically ill patients, the drugs should be dosed as dictated by the situation, true to the anaesthesiologists' adage: "Dosage according to effect!"     

Nutritional gain versus financial gain: The role of metabolic carts in the surgical ICU

BACKGROUND: Adequate nutritional replacement of critically ill and injured patients is of paramount importance, as it decreases infectious morbidity and mortality. However, multiple methods of determining nutritional requirements exist, including mathematical formulas, weight based calculations, and the use of metabolic cart measurements, the latter of which is associated with significant labor and equipment costs. We hypothesized that metabolic cart measurements, despite increasing the cost of care, would more accurately determine nutritional requirements in a critically ill population than formulaic or weight-based calculations. METHODS: Consecutive metabolic cart measurements were prospectively obtained on 59 critically ill surgery and trauma patients, and compared with predicted values as determined by the Harris-Benedict equation and weight-based calculations. Comparison was made to actual resting energy expenditure data acquired via indirect calorimetry data obtained from serial metabolic carts. RESULTS: There were 59 patients who formed the study population, with 37% of the population having two or more metabolic cart readings (total number of cart readings was 106). There was no statistically significant difference between the metabolic cart results, the predicted resting energy expenditure as calculated by the Harris-Benedict equation adjusted with a factor of 1.5, and a weight based calculation at 30 kcal/kg adjusted body weight. Metabolic requirements were stable over time (4-48 days) without significant variation. Nutritional parameters, as evaluated by the visceral proteins prealbumin and transferrin significantly increased with time in injured patients. CONCLUSIONS: Either 30 kcal/kg adjusted body weight or the resting energy expenditure calculated from the Harris-Benedict equation multiplied by 1.5 adequately predicts the nutritional requirements of critically ill surgery and trauma patients. The addition of metabolic cart data does not provide any additional information in the determination of caloric needs in the critically ill and injured patient. In this population, omission of metabolic cart data would have saved 33,000 dollars without adversely affecting patient outcome.     

Transthoracic echocardiography is not cost-effective in critically ill surgical patients

BACKGROUND: Echocardiography has been shown to be valuable in critically ill surgical patients. Transthoracic echocardiography (TTE) often fails to provide adequate imaging in critically ill patients, necessitating subsequent transesophageal echocardiography (TEE). The objective of this study was to determine and quantify factors associated with failure of transthoracic echocardiography (TTE) in critically ill surgical patients, and to define a cost-effective strategy for echocardiography in these patients. METHODS: Demographic and clinical data were collected retrospectively and evaluated to determine which factors were associated with failure of TTE to provide adequate imaging. In addition, models were developed to estimate costs for echocardiography in critically ill surgical patients. RESULTS: TTE has a high failure rate in critically ill surgical patients. This failure rate increases significantly in patients who gain > 10% body weight from admission weight, who are supported with > or = 15 cm H(2)O positive end-expiratory pressure, and in those with chest tubes. As a result, the use of TTE in critically ill surgical patients is not cost-effective. TEE, however, is highly effective in this group of patients, and is more cost-effective than TTE in evaluating those critically ill surgical patients requiring echocardiography. CONCLUSION: The routine use of TTE to initially evaluate all critically ill surgical patients who require echocardiography should be abandoned because it is not cost-effective. TEE appears to be the most cost-effective echocardiographic modality in the surgical intensive care unit.     

Derived oxygen saturations are not clinically useful for the calculation of oxygen consumption.

In critically ill patients, oxygen consumption (VO2) and delivery (DO2) are used to determine optimal haemodynamic management and to grade severity of illness. VO2 may be measured by indirect calorimetry with metabolic gas monitoring systems or derived using the reverse Fick principle. Oxygen saturation (SaO2) may be measured directly by co-oximetry or derived by equations for incorporation into reverse Fick equations. A prospective study comparing VO2 measured by these methods was performed in 20 critically ill patients. The mean VO2 measured by the metabolic gas monitoring system (308 +/- 63.9 ml/min) was significantly greater than that measured by reverse Fick using measured SaO2 (284 +/- 72.0 ml/min) (P < 0.01). This difference may be due to intrapulmonary VO2. When SaO2 was calculated from three logarithmic equations and incorporated into the reverse Fick equations, calculated VO2's were significantly greater (P < 0.001) than those measured by indirect calorimetry. Correlation was poor and wide limits of agreement (-118 to +350 ml/min) were demonstrated. VO2 should ideally be measured by indirect calorimetry in the critically ill, or if reverse Fick is used, SaO2 should be measured by co-oximetry as the use of equations for clinical measurement of SaO2 is clinically suspect.     

Variation in the resting metabolic rate of mechanically ventilated critically ill patients

There has been increasing interest in the nutritional support of the critically ill patient. The day-to-day variation in resting energy expenditure (REE) was studied over a 3-5-day period in 17 postoperative mechanically ventilated critically ill patients to gain insight as to how often caloric intake should be reassessed, whether changes observed over 3-5 days are of sufficient magnitude to make frequent adjustments in caloric intake, and what factors are associated with large alterations in metabolic rate. REE was measured daily for 3-5 days, and the percent variation in REE [(highest REE--lowest daily REE)/(lowest daily REE) x 100] calculated. The variation ranged from 4 to 56%, and on further analysis two distinct groups were identified, one with a mean variation of 12 +/- 4% (SD) (range 4-18%) and the other with a mean variation of 46 +/- 8% (range 37-56%). The former group was clinically stable, whereas the latter was not. Clinically stable patients need less frequent measurements than those who are more ill, but when designing a nutritional regimen for them, at least 20-25% should be added to the REE, 15% to account for day-to-day variation and 5-10% for activity.     

Diabetic and nondiabetic hyperglycemia in the ICU

Hyperglycemia is a common feature in critically ill patients, whether they are diabetic or not, and it is associated with unfavorable outcome. The more severe the underlying disease, the more important the hyperglycemia appears to be although, we still cannot define whether hyperglycemia is just a marker of the severity of the acute illness or rather an active contributor to poor outcome. The review of the literature on this subject published from 2001 up today conveys a massive amount of information the interpretation of which is equivocal, due to the heterogeneity of patients (nondiabetic vs. diabetic, medical intensive care unit (ICU) pts vs. surgical ICU pts) and of interventions (dose and modality of insulin infusion).The association between high glucose level and mortality is strong in critically ill patients without a previous history of diabetes. Admission hyperglycemia seems to be an independent risk factor of in-hospital mortality in patients both with and without diabetes in cardiac, cardiothoracic and neurosurgical ICUs. No data are still available on general surgical ICU patients.Tight control of blood glucose levels has been demonstrated to improve outcome in both diabetic and nondiabetic critically ill patients. In surgical ICUs, tight glucose control improves mortality and reduces morbidity only among patients admitted in ICU for more than 5 days, while outcome is not improved in patients who stay in ICU for less than 3 days.However, it is not yet understood if such favorable effect is secondary to glucose control itself or if insulin plays a part, by means of its nonglucose, anabolic effects. More randomized controlled trials are needed, addressing specific issues—such as the optimal target glucose concentration and the most effective insulin regimen—especially in the general surgical patient.     

Increased susceptibility to apoptosis in circulating lymphocytes of critically ill patients

BACKGROUND AND AIMS: Lymphocyte apoptosis may influence immune responsiveness in systemic inflammation. Therefore, we investigated whether early signs of apoptosis (i.e., annexin-V binding and cell shrinkage) in peripheral lymphocytes were different among patients with severe sepsis, critically ill, nonseptic patients after major surgery, and healthy individuals. PATIENTS/METHODS: Ten patients with severe sepsis and ten critically ill, nonseptic patients after major surgery admitted to a surgical intensive care unit in a university hospital were included in the study. In addition, ten healthy blood donors were included for comparison. We investigated early signs of apoptosis using flow cytometric measurement of annexin-V binding to the cell surface and cell shrinkage of peripheral lymphocytes. RESULTS: The percentage of apoptotic lymphocytes determined as annexin-V positive and propidium iodide negative cells was increased in freshly prepared cells of patients with severe sepsis (11.4 +/- 0.5%) and critically ill, nonseptic patients after major surgery (18.5 +/- 2.0%) relative to healthy blood donors (4.4 +/- 0.5%) (P < 0.05). No significant difference between patients with severe sepsis and patients after major surgery were found. Annexin-V binding increased significantly after OKT-3 stimulation of lymphocytes in patients with severe sepsis (34.4 +/- 1.6%), patients after major surgery (33.8 +/- 3.4%), and healthy blood donors (21.1 +/- 2.8%). No significant difference among groups was detected following OKT-3 stimulation. Furthermore, freshly isolated peripheral lymphocytes of patients with severe sepsis and critically ill, nonseptic patients after major surgery revealed a significantly higher proportion of cell shrinkage than in healthy blood donors (55.0 +/- 2.2%, 21.5 +/- 2.4% vs 3.6 +/- 0.7%; P < 0.05). CONCLUSION: Circulating lymphocytes of critically ill patients show a high degree of early signs of cellular apoptosis. This may contribute to hyporesponsiveness of immune cells in systemic inflammation.     

Lactate- or bicarbonate-buffered solutions in continuous extracorporeal renal replacement therapies

BACKGROUND: Continuous renal replacement therapies (CRRTs) are well accepted for critically ill patients with acute renal failure (ARF). Today, daily fluid exchange in CRRT reaches 30 to 40 liter and more. Therefore, the composition of the substitution/dialysate fluid, often primarily developed either for intermittent treatment or for peritoneal dialysis, becomes more relevant. Lactate (30 to 45 mmol/liter) is frequently used as the buffer because of the high stability of this substance. However, lactate is thought to have negative effects on metabolic and hemodynamic parameters. METHODS: Published data for different substitution fluids are presented with respect to acidosis and lactate concentration, uremia, and hemodynamic and metabolic alterations. RESULTS: Only a few studies compare substitution fluids with different buffers. Uremia and acidosis (pH, base excess) were sufficiently controlled during CRRT with an exchange volume of in average 30 liters using either buffer. If patients with severe liver failure and lactic acidosis were excluded, no difference in hemodynamic and metabolic parameters between the solutions occurred. The plasma lactate concentration was elevated during lactate use in some cases, but lactate levels remained within normal limits in patients without liver impairment. The bicarbonate concentration in the solutions should exceed 35 to 40 mmol/liter, as in some cases the buffer capacity of the solutions was inadequate. In patients with severe liver failure or lactic acidosis, solutions with lactate buffer were shown not to be indicated. CONCLUSION: In patients with reduced lactate metabolism, for example, concomitant severe liver failure, after liver transplantation or in lactic acidosis, bicarbonate-buffered solutions should be used. In nearly all other cases of critically ill patients with ARF, lactate-buffered solutions may be used as well as bicarbonate solutions.     

Fluid management in the critically ill child

Fluid management has a major impact on the duration, severity and outcome of critical illness. The overall strategy for the acutely ill child should be biphasic. Aggressive volume expansion to support tissue oxygen delivery as part of early goal-directed resuscitation algorithms for shock—especially septic shock—has been associated with dramatic improvements in outcome. Recent data suggest that the cost-benefit of aggressive fluid resuscitation may be more complex than previously thought, and may depend on case-mix and the availability of intensive care. After the resuscitation phase, critically ill children tend to retain free water while having reduced insensible losses. Fluid regimens that limit or avoid positive fluid balance are associated with a reduced length of hospital stay and fewer complications. Identifying the point at which patients change from the ‘early shock’ pattern to the later ‘chronic critical illness’ pattern remains a major challenge. Very little data are available on the choice of fluids, and most of the information that is available arises from studies of critically ill adults. There is therefore an urgent need for high-quality trials of both resuscitation and maintenance fluid regimens in critically ill children.