Richard G. Barton

Invited Review: Nutrition Support in Critical Illness

Sepsis, shock, multiple trauma, and burns are often associated with altered metabolism characterized by severe catabolism, wasting of the lean body mass, immune dysfunction, and compromised wound healing. Nutrition support is one of the mainstays in the management of these critically ill patients and is aimed at minimizing these complications. The purpose of this article is to compare stress hypermetabolism and starvation metabolism, to review current recommendations for the provision of energy and substrate to the critically ill patient, and to review pertinent literature regarding enteral vs parenteral nutrition. Finally, this article will provide a brief overview of new and future therapies with emphasis on specific substrates and growth factors and the potential for their use in the critically ill patient.

Etiology and consequences of respiratory failure in thermally injured patients

Inhalation injury predisposes burn patients to pneumonia, respiratory failure, and death, but the incidence and consequences of respiratory failure in the absence of inhalation injury are not well known. In a review of 529 burn patients admitted over a 4-year period, patients with inhalation injury had a 73% incidence of respiratory failure (hypoxemia, multiple pulmonary infections, or prolonged ventilator support) and a 20% incidence of adult respiratory distress syndrome (ARDS). In patients without inhalation injury, respiratory failure developed in 5% of patients and ARDS in 2% (both p < 0.001). Patients with respiratory failure display a high incidence of multiple organ failure and mortality (27% to 50%), regardless of the presence of inhalation injury. All patients who died had multiple organ failure. This review demonstrates that respiratory failure, regardless of its cause, frequently leads to multiple organ failure and death. Inhalation injury, in the absence of respiratory failure, does not appear to contribute to mortality.

Dietary omega-3 fatty acids decrease mortality and Kupffer cell prostaglandin E2 production in a rat model of chronic sepsis.

We tested the hypothesis that substitution of omega-3 fat for dietary omega-6 fat would reduce mortality and decrease Kupffer cell prostaglandin E2 (PGE2) production in a rat model of chronic sepsis. Rats were fed via gastrostomy for 12 days with isonitrogenous, isocaloric diets containing 15% of calories as either safflower oil (omega-6) or a 10:1 mixture of menhaden oil (omega-3) and safflower oil. After five days of feeding, animals received an intra-abdominal abscess of defined bacterial content. Survivors were killed on post-laparotomy day 6 in conjunction with liver perfusion and protease liver digestion for Kupffer cell isolation. Kupffer cell PGE2 production was measured by radioimmunoassay after 18 hours of cell culture and again after stimulation with 0 LPS, 10 ng/ml LPS, and 10 micrograms/LPS. Mortality was decreased in menhaden oil-fed animals compared with safflower oil-fed animals (16% vs. 35%). Kupffer cell PGE2 production was decreased in menhaden oil-fed animals at 18 hours (354 +/- 54 vs. 570 +/- 95 pg/0.1 ml; p = 0.09) and after stimulation with 10 micrograms/ml LPS (140 +/- 41 vs. 288 +/- 45 pg/0.1 ml; p = 0.03) compared with safflower oil-fed animals.

Survey of intensive care physicians on the recognition and management of intra-abdominal hypertension and abdominal compartment syndrome*

Objective:To assess current understanding and clinical management of intra-abdominal hypertension and abdominal compartment syndrome among critical care physicians. Design:A ten-question, written survey. Setting:University health sciences center. Subjects:Physician members of the Society of Critical Care Medicine (SCCM). Interventions:The survey was sent to 4,538 SCCM members with a response rate of 35.7% (1622). Measurements and Main Results:Primary training, intensive care unit type, and methods for management of abdominal compartment syndrome were assessed. Surgically trained intensivists managed the highest number of abdominal compartment syndrome cases (47% managed 4–10 cases, 16% managed >10 cases). No cases were seen by 25% of medically trained and pediatric trained intensivists. Respondents agreed that bladder pressures and clinical variables were needed to diagnose abdominal compartment syndrome (70%) vs. bladder pressure (7%) or clinical variables (20%) alone. Two percent of surgical intensivists were unaware of a bladder pressure measurement procedure compared with 24% (p < .0001) of pediatric and 23% (p < .0001) of medical intensivists. Forty-two percent of respondents believed bladder pressures of 20–27 mm Hg may cause physiologic compromise. However, 25–27% of pediatric, medicine, or anesthesia trained intensivists believed that compromise occurs between 12 and 19 mm Hg compared with 18% of surgeons. No respondent believed that physiologic compromise occurred at <8 mm Hg. Thirty-eight percent of pediatric intensivists believed that physiologic compromise was patient dependent vs. 7–17% from other specialties (p < .0001; all comparisons). In managing intra-abdominal hypertension, 33% of pediatric intensivists and 19.6% of medical intensivists would never use decompression laparotomy to treat abdominal compartment syndrome compared with 3.6% of intensivists with surgical training (p < .0001; both comparisons). Conclusions:Significant variation across medical training exists in the management of intra-abdominal hypertension and abdominal compartment syndrome. A significant percentage of intensivists may be unaware of current approaches to abdominal compartment syndrome management including monitoring bladder pressures and decompression laparotomy. Future research and education are necessary to establish clear diagnostic criteria and standards for treatment of this relatively common life-threatening disease process.

A guide to drug therapy in patients with enteral feeding tubes: Dosage form selection and administration methods

Drug therapy may be complicated in hospitalized patients receiving nutrition via enteral feeding tubes. Dosage form selection and appropriate administration methods are crucial in patients with feeding tubes. Although hospitalized patients receive nutritional support through various routes, oral nutrition is preferred. Enteral or parenteral nutrition may be used if oral intake is inadequate or inadvisable. Patients with functional gastrointestinal tracts usually receive enteral nutrition. Administering oral medications through the enteral feeding tube can lead to complications like tube clogging or decreased drug activity. However, drug therapy need not be compromised in patients receiving enteral nutrition. Careful selection and preparation of dosage forms reduces the complications of medication administration. Flushing the feeding tube and screening for drug incompatibilities decreases the incidence of tube clogging and replacement.

Resuscitation of thermally injured patients with oxygen transport criteria as goals of therapy

Resuscitation from shock based on oxygen transport criteria has been widely used in trauma and surgical patients, but has not been examined in thermally injured patients. To study the possible efficacy of this type of resuscitation, the oxygen transport characteristics of burn resuscitation were studied in nine adults, of whom six had inhalation injuries, with a mean burn size of 45% total body surface area and a mean age of 33.4 years, who were resuscitated based on oxygen transport criteria. Pulmonary artery balloon flotation catheters were placed and hemodynamic and oxygen transport parameters (Fick method) were measured hourly for 6 hours. Patients received fluid boluses in addition to resuscitation calculated by the Parkland formula, until the pulmonary artery wedge pressure reached 15 mm Hg, after which dobutamine infusions (5 micrograms/kg/min) were initiated. Cardiac index increased from 2.51 to 6.57 L/min/m2 (p < 0.05), whereas systemic vascular resistance fell from 1534 to 584 dyne sec/cm5 (p < 0.05). Oxygen delivery (DO2I) and oxygen consumption (VO2I) indexes increased significantly during the study period (573 +/- 47 to 1028 +/- 57, and 132 +/- 8 to 172 +/- 16 ml/min/m2, respectively; p < 0.05). VO2I appeared dependent on DO2I at levels of DO2I less than 800 ml/min/m2. In this study, depressed cardiovascular function in patients with burn injuries responded to volume loading and inotropic support much as it does in patients with shock of other etiologies. Whether oxygen transport-based resuscitation is effective in improving survival or the incidence of multiple organ failure is unknown and will need to be evaluated in randomized trials.

Implementation of an Enoxaparin Protocol for Venous Thromboembolism Prophylaxis in Obese Surgical Intensive Care Unit Patients

Background:: Venous thromboembolism (VTE) is a serious health care issue that affects a large number of people. Few standards exist for delineating the optimal dosing strategy for VTE prevention in obese patients, especially in the setting of major surgery or trauma. Objective: To document the efficacy of a surgical intensive care unit (SICU)–specific, weight-based dosing protocol of enoxaparin 0.5 mg/kg given subcutaneously every 12 hours for VTE prophylaxis in morbidly obese (defined as body mass index [BMI] ≥35 kg/m2 or weight ≥150 kg) SICU patients, using peak anti-factor Xa levels to determine therapeutic endpoints. Methods: Data were collected retrospectively in an academic, university-based SICU on 23 morbidly obese patients who received weight-based enoxaparin for VTE prophylaxis from December 1, 2008, through June 30, 2010. Results: A weight-based dosage range of enoxaparin 50-120 mg twice daily (median 60) was given to 23 patients. The mean BMI was 46.4 kg/m2. The initial mean anti-factor Xa level (measured after the third dose) was 0.34 IU/mL (range 0.20-0.59). Patients received an average of 18 doses. Two cases required an increase or decrease in dosage based on anti-factor Xa levels. Morbidity related to this dosing included a single event of minor endotracheal bleeding and a single deep vein thrombosis that was likely present prior to treatment. Conclusions: Weight-based dosing with enoxaparin in morbidly obese SICU patients was effective in achieving anti-factor Xa levels within the appropriate prophylactic range. This regimen reduced the rate of VTE below expected levels and no additional adverse effects were reported.

Propofol is associated with favorable outcomes compared with benzodiazepines in ventilated intensive care unit patients.

RATIONALE Mechanically ventilated intensive care unit (ICU) patients are frequently managed using a continuous-infusion sedative. Although recent guidelines suggest avoiding benzodiazepines for sedation, this class of drugs is still widely used. There are limited data comparing sedative agents in terms of clinical outcomes in an ICU setting. OBJECTIVES Comparison of propofol to midazolam and lorazepam in adult ICU patients. METHODS Data were obtained from a multicenter ICU database (2003-2009). Patient selection criteria included age greater than or equal to 18 years, single ICU admission with single ventilation event (>48 h), and treatment with continuously infused sedation (propofol, midazolam, or lorazepam). Propensity score analysis (1:1) was used and mortality measured. Cumulative incidence and competing risk methodology were used to examine time to ICU discharge and ventilator removal. MEASUREMENTS AND MAIN RESULTS There were 2,250 propofol-midazolam and 1,054 propofol-lorazepam matched patients. Hospital mortality was statistically lower in propofol-treated patients as compared with midazolam- or lorazepam-treated patients (risk ratio, 0.76; 95% confidence interval [CI], 0.69-0.82 and risk ratio, 0.78; 95% CI, 0.68-0.89, respectively). Competing risk analysis for 28-day ICU time period showed that propofol-treated patients had a statistically higher probability for ICU discharge (78.9% vs. 69.5%; 79.2% vs. 71.9%; P < 0.001) and earlier removal from the ventilator (84.4% vs. 75.1%; 84.3% vs. 78.8%; P < 0.001) when compared with midazolam- and lorazepam-treated patients, respectively. CONCLUSIONS In this large, propensity-matched ICU population, patients treated with propofol had a reduced risk of mortality and had both an increased likelihood of earlier ICU discharge and earlier discontinuation of mechanical ventilation.

Predictors of Mortality in Pulmonary Contusion

BACKGROUND Associated injuries and central nervous system (CNS) trauma are historically associated with poor outcome in patients with pulmonary contusions, but the value of specific factors reflecting shock, fluid resuscitation requirement and pulmonary parenchymal injury in predicting mortality in this population is not well established. METHODS The medical records of 100 consecutive patients with pulmonary contusion, admitted over a 5-year period, were retrospectively reviewed. Survivors and nonsurvivors were compared in terms of age, Injury Severity Score (ISS), Glasgow Coma Score (GCS), PaO2/FiO2 (oxygenation ratio), the severity and adequacy of shock resuscitation reflected in plasma lactate, resuscitation volume and transfusion requirements, using one-way ANOVA. To determine the contribution of individual, interdependent variables to mortality, the data were then analyzed using multivariable analysis. RESULTS ISS and transfusion requirement were significantly higher, and GCS and PaO2/FiO2 at 24 and 48 hours after admission were significantly lower in nonsurvivors than in survivors. After multiple regression analysis, the factors most strongly associated with mortality included patient age, oxygenation ratio at 24 hours after admission, and resuscitation volume. CONCLUSIONS Outcome in patients with pulmonary contusion is dependent upon a number of variables including the severity of pulmonary parenchymal injury as reflected in PaO2/FiO2 ratio.

Decreased mortality from necrotizing pancreatitis

BACKGROUND Necrotizing pancreatitis has been associated with mortality rates of 25% to 80%. We reviewed our experience to determine whether aggressive debridement and comprehensive critical care improves survival. METHODS The records of 989 patients with the diagnosis of pancreatitis admitted between January 1990 and September 1997 were retrospectively reviewed. Twenty-six patients required surgery for necrotizing pancreatitis and are the subjects of this review. RESULTS Five of twenty-six patients (19%) died. For all patients, mean Ransons score was 4.3 of 11, mean admission APACHE II score was 17.2, and mean Multiple Organ Dysfunction (MOD) score was 9.1. Poor outcome was associated with infected pancreatic necrosis (P = 0.03), elevated APACHE II score on admission (P = 0.04), and progression of MOD during the week after admission (P = 0.02). CONCLUSIONS This review demonstrates improved survival in seriously ill patients with necrotizing pancreatitis as a result of comprehensive surgical and critical care.