Sildenafil increases muscle protein synthesis and reduces muscle fatigue

Reductions in skeletal muscle function occur during the course of healthy aging as well as with bed rest or diverse diseases such as cancer, muscular dystrophy, and heart failure. However, there are no accepted pharmacologic therapies to improve impaired skeletal muscle function. Nitric oxide may influence skeletal muscle function through effects on excitation-contraction coupling, myofibrillar function, perfusion, and metabolism. Here we show that augmentation of nitric oxide-cyclic guanosine monophosphate signaling by short-term daily administration of the phosphodiesterase 5 inhibitor sildenafil increases protein synthesis, alters protein expression and nitrosylation, and reduces fatigue in human skeletal muscle. These findings suggest that phosphodiesterase 5 inhibitors represent viable pharmacologic interventions to improve muscle function.

Preoperative maneuvers to avert postoperative respiratory failure in elderly patients

BACKGROUND

The elderly appear particularly vulnerable to pulmonary complications following surgical procedures.

OBJECTIVE

The purpose of this study was to identify and assess the merit of various maneuvers employed to mitigate respiratory difficulties in elderly patients undergoing surgery.

RESULTS

The literature revealed evidence that diminishing sputum production with selective antibiotics and augmentation of sputum clearance with assisted coughing, postural drainage, and bronchodilators were deemed important. Futhermore, efforts to optimize nutritional status and eliminate tobacco and alcohol consumption are also felt to be of value in improving postsurgical outcome.

CONCLUSION

One significant aspect of this review was the apparent posity of recent work on this subject despite the profound magnitude of the demise related to postsurgical respiratory complications in elderly patients.

Quantification of amino acid transport through interstitial fluid: assessment of four-compartment modeling for muscle protein kinetics

The purpose of this study was to assess a novel technique for quantifying in vivo muscle protein metabolism and phenylalanine transport in septic patients and normal volunteers and thereby assess the influence of sepsis on muscle protein kinetics. In patients resuscitated from sepsis, blood flow and edema may influence the extent of muscle loss. Six adult patients septic from pneumonia underwent a study protocol consisting of infusion of isotopic phenylalanine, indocyanine green dye, and sodium bromide; biopsies of skeletal muscle; and sampling from the femoral artery, vein, and interstitial fluid. Study results demonstrate a substantial net catabolism of muscle, an accelerated flux of phenylalanine, and an increased leg blood flow for septic patients compared with normal volunteers. For septic patients and normal volunteers, the rate of phenylalanine transport through the interstitium was rate limiting for the movement of phenylalanine between vasculature and muscle. Measurements demonstrate a concentration gradient of phenylalanine favoring the net efflux of amino acids from the leg in the septic patients. Despite whole body edema, the extracellular fluid volume within muscle of septic patients was similar to normal. These findings demonstrate that the extent of muscle loss in critically ill patients results from the net increase in the rate of muscle protein breakdown, which subsequently drives amino acids through the interstitial compartment down their concentration gradient. Therefore, any effective therapy to correct illness-induced muscle catabolism should be directed at altering the rates of breakdown and synthesis of muscle protein and are not likely related to tissue edema.

Supportive care in acute respiratory distress syndrome

Although the central focus of acute respiratory distress syndrome (ARDS) is the pathology within the lung, ARDS is very much a systemic disease. As such, the whole body needs care and support while the disease process within the lung runs its course. The issues of pain management, sedation, fluid balance, nutrition, metabolic and hormonal processes, infection control, and patient positioning are important for any patient in a critical care setting. For patients with ARDS, the required ventilatory support and ARDS-associated systemic inflammation mandate the above supportive measures.

Quantification of protein metabolism in vivo for skin, wound, and muscle in severe burn patients

BACKGROUND

In response to injury, muscle catabolism can be extensive, and in theory, the wound consumes amino acids to support healing. The purpose of this study is to assess a technique by which in vivo protein kinetics of muscle, wound, and normal skin can be quantified in burn-injured patients.

METHODS

Study protocol consisting of infusion of d5 phenylalanine; biopsies of skeletal muscle, skin, and donor-site wound on the leg; quantification of blood flow to total leg, wound, and skin; and sequential blood sampling from the femoral artery and vein. Five-compartment modeling was used to quantify the rates of protein synthesis, breakdown, and phenylalanine transport between muscle, wound, and skin.

RESULTS

The study results demonstrated a net release of phenylalanine from muscle yet a net consumption of phenylalanine by the wound. Compared with skin, the wound had a substantially increased rate of protein synthesis and a reduced rate of protein breakdown (p < .01). Transport rates into and out of muscle were significantly higher than those for wound (p < .01).

CONCLUSIONS

This novel methodology enables in vivo quantification of the integrated response of muscle, wound, and skin protein/amino acid metabolism and confirms the long-held theory of a net catabolism of muscle and a net anabolism of wound protein in patients after injury. This methodology can be used to assess the metabolic impact of such measures as nutrition, pharmacologic agents, and surgical procedures.

Hemodynamic and metabolic effects of selective beta1 adrenergic blockade during sepsis

BACKGROUND

Selective beta adrenergic antagonists are commonly used to reduce myocardial demise in patients at risk for cardiac-related death. The purpose of this study was to examine the hemodynamic and metabolic effects of cardiac selective beta adrenergic blockade in patients.

METHODS

Muscle protein kinetics were quantified using isotopic tracer methodology in 6 moderately septic, mechanically ventilated patients with pneumonia before and then at the conclusion of a 3-hour infusion of esmolol of sufficient dose to reduce heart rate by 20% from baseline. A battery of hemodynamic measurements as facilitated by a thermodilution pulmonary artery catheter and indirect calorimetry were also measured before and after the 3-hour selective beta adrenergic blockade.

RESULTS

Selective beta adrenergic blockade was associated with the 20% reduction in heart rate and a comparable decrease in cardiac output. Esmolol administration failed to affect systemic or pulmonary vascular resistance, oxygen consumption, hepatic or leg blood flow, energy expenditure, or ATP availability/energy charge within muscle. Esmolol infuse did incite a shift in fuel oxidation toward an increase in palmitate oxidation and with a decrease in the oxidation of glucose. There was no demonstrable influence beta1 adrenergic blockade on muscle protein kinetics.

CONCLUSIONS

Cardiac selective beta adrenergic blockade with esmolol reduces cardiac output in proportion to the percentage decreases in heart rate in moderately severe septic patients without adversely affecting oxygen utilization or hepatic, peripheral blood flow.

National survey of surgical morbidity and mortality conferences

BACKGROUND

Morbidity and mortality conferences historically have been a paramount meeting for education and quality assurance within surgical departments of teaching institutions. The purpose of this survey was to assess the present educational value and the quality assurance aspect of surgical mortality conferences.

METHODS

Surveys were sent to every academic surgical training program director within the United States and Canada (n = 127) and queried the general format and an individual's experience and attitude toward their institutions conference.

RESULTS

A total of 546 individuals from 34 institutions returned completed surveys. The survey findings showed that 74% of these surgical departments discussed all deaths and 50% discussed all complications. There was general agreement that surgical morbidity and mortality conferences are of good educational value and effective in reducing future error. The majority of respondents expressed that evidence-based literature should be the primary basis of discussion, with comprehensive presentations that focus on analysis of error.

CONCLUSIONS

This survey showed that morbidity and mortality conferences are both educational and perceived by the respondents as effective in reducing future error.

Comparison of peripheral metabolic effects of insulin and metformin following severe burn injury

OBJECTIVE

Both insulin and metformin have been shown to attenuate hyperglycemia and reduce net muscle protein catabolism following burn injury. The purpose of this study was to compare the peripheral metabolic effects of insulin and metformin in severe burn patients.

METHODS

Six adult patients with burns greater than 40% of their body surface underwent metabolic evaluation utilizing isotopic dilution of phenylalanine, femoral arterial and venous blood sampling, and sequential biopsies of leg muscle. Following baseline measurements, insulin was infused into the femoral artery at 0.45 mIU/min 100 mL leg volume. Patients were then given metformin (850 mg every 8 hours) for seven days with repeat metabolic evaluation before and during intra-arterial infusion of insulin.

RESULTS

Intra-arterial administration of insulin significantly increased insulin concentrations within the femoral vein, creating hyperinsulinemia localized to the extremity. Metformin had no significant effect on either peripheral glucose clearance or the rate of glucose oxidation. Furthermore, the availability of ATP and energy charge within muscle was not overtly affected by either insulin or metformin. Metformin did significantly increase the fractional synthetic rate of muscle protein which increased even further with insulin administration. Both metformin and insulin separately increased the rate of muscle protein synthesis as calculated using three compartment modeling.

CONCLUSION

This study demonstrates a significant anabolic effect on muscle protein with metformin and a modest response with insulin. Findings also suggest that metformin and insulin may work synergistically to further improve muscle protein kinetics.

Temporal changes in cellular energy following burn injury

Availability of ADP is a predominant influence on respiratory control. Associated with severe burn injury is an increase in energy expenditure. The purpose of this study was to determine the temporal changes in ATP, ADP, NAD, and NADH following severe burn and thereby assess any related alterations in respiratory control and energy deficit. During isoflurane anesthesia and following intraperitoneal injection of saline, 32 mice were flame burned at 40% body surface area. Twelve mice served as controls. At 12, 24, 72, and 168 h post-burn, groups of mice underwent celiotomy with determination of hepatic surface blood flow using laser Doppler and oxygen saturation using pulse oximetry. Biopsies of liver were then frozen in liquid nitrogen for subsequent quantification of ATP, ADP, AMP, NAD, and NADH by HPLC. Mortality was 12.5% at 72 h post-burn and 25% at 1 week. Oxygen saturation and hepatic surface blood flow remained similar to control values throughout the week after burn. ATP, ADP, and energy charge decreased progressively following burn reaching a significant decrease from unburned controls at 72 h. Availability of NADH remained statistically similar to unburned controls throughout the week after burn. These results demonstrate that despite maintenance of baseline oxygen delivery, there was a nadir in ATP and ADP availability and energy charge in the liver at 72 h after burn. This finding supports the concept of a limitation in phosphorylation after injury. Availability of NADH remained at or above pre-burn concentrations suggesting that the rate of fuel oxidation was not a limiting factor for ongoing oxidative phosphorylation for energy.

Utility of Acellular Allograft Dermis in the Care of Elderly Burn Patients

BACKGROUND

Because skin thins with advancing age, traditional thickness skin grafts cannot always be obtained in very elderly burn patients without creating a new full-thickness wound at the skin graft donor site.

MATERIALS AND METHODS

In an attempt to circumvent this problem, acellular allograft dermis (Alloderm, Life Cell Corp., The Woodlands, TX) and thin autograft (depth 0.005 inches) was used in skin grafting 10 elderly burn patients (age 78 year +/- 2, TBSA burn 17% +/- 2; mean +/- SEM) over a 1-year period. The outcome of patients receiving Alloderm was compared retrospectively to a similar group of 18 elderly patients admitted over the prior year, eight of whom underwent operative wound excision and autografting (depth 0.014 inches) without Alloderm.

RESULTS

Length of hospital stay was significantly reduced in patients treated with Alloderm compared to the total group of elderly in whom selective use of operative debridement and skin grafting was used. Functional outcome was improved in those patients who underwent skin grafting regardless of operative technique. Donor site healing time was significantly reduced with Alloderm (12 days +/- 1 versus 18 days +/- 2), while graft take was similar to conventional autografting. Unfortunately, 3-month mortality remained poor regardless of operative skin grafting or technique used.

CONCLUSIONS

This initial experience suggests that use of Alloderm may allow more elderly burn patients to undergo operative wound closure, thus improving functional outcome and reducing hospitalization. Unfortunately, long-term survival for very elderly burn patients remains poor.

Influence of metformin on glucose intolerance and muscle catabolism following severe burn injury

SUMMARY BACKGROUND DATA

Hyperglycemia and accelerated muscle catabolism have been shown to adversely affect immune response and survival. The purpose of this study was to determine the effect of metformin on glucose kinetics and muscle protein metabolism in severely burned patients and assess any potential benefit of metformin in this clinical setting.

METHODS

In a double-blind, randomized manner, 8 adult burn patients received metformin (850 mg every 8 hours x 7 days), while 5 burn patients received placebo. Infusions of 6,6d2 glucose, d5 phenylalanine, sequential muscle biopsies, and femoral arterial, venous blood sampling allowed determination of glucose and muscle protein kinetics. Measurements were obtained immediately prior and at the conclusion of 7 days of treatment (metformin versus placebo). All patients received enteral feeds of comparable amounts during study.

RESULTS

Patients receiving metformin had a significant decrease in their plasma glucose concentration, the rate of glucose production, and an increase in glucose clearance. Metformin administration was also associated with a significant increase in the fractional synthetic rate of muscle protein and improvement in net muscle protein balance. Glucose kinetics and muscle protein metabolism were not significantly altered in the patients receiving placebo.

CONCLUSIONS

Metformin attenuates hyperglycemia and increases muscle protein synthesis in severely burned patients, thereby indicating a metabolic link between hyperglycemia and muscle loss following severe injury. Therefore, therapies that improve glucose tolerance such as metformin may be of clinical value in ameliorating muscle catabolism in critically injured patients.

Angiosarcoma of the of scalp with calvarium involvement in a 50-year-old African-American man

BACKGROUND

Angiosarcoma of the scalp is a rare, aggressive, and deadly cancer that affects mainly elderly Caucasian men.

OBJECTIVES

The insidious and masquerading presentation of angiosarcoma poses enormous diagnostic challenges for primary care providers.

PATIENTS/METHODS

We present a case of a 50-year-old black man referred for evaluation of a 3.7-cm-x-5.4-cm ulcerated, fluctuant scalp lesion that had failed to respond to different antibiotics and proper wound care.

RESULTS

Surgical excision and subsequent histopathology revealed angiosarcoma.

CONCLUSIONS

This case report highlights the importance of high index of suspicion for early diagnosis of cancerous lesions in wounds and stresses the need to include angiosarcoma in the differential diagnosis for all face and scalp lesions, as early detection may save lives. A comprehensive literature review is also presented.

Extremity hyperinsulinemia stimulates muscle protein synthesis in severely injured patients

Insulin has a well-recognized anabolic effect on muscle protein, yet critically ill, severely injured patients are often considered "resistant" to the action of insulin. The purpose of this study was to assess the in vivo effects of hyperinsulinemia on human skeletal muscle in severely injured patients. To accomplish this goal, 14 patients with burns encompassing >40% of their body surface area underwent metabolic evaluation utilizing isotopic dilution of phenylalanine, femoral artery and vein blood sampling, and sequential muscle biopsies of the leg. After baseline metabolic measurements were taken, insulin was infused into the femoral artery at 0.45 mIU.min(-1).100 ml leg volume(-1) to create a local hyperinsulinemia but with minimal systemic perturbations. Insulin administration increased femoral venous concentration of insulin (P < 0.01) but with only a 4% (insignificant) decrease in the arterial glucose concentration and a 7% (insignificant) decrease in the arterial concentration of phenylalanine. Extremity hyperinsulinemia significantly increased leg blood flow (P < 0.05) and the rate of muscle protein synthesis (P < 0.05). Neither the rate of muscle protein breakdown nor the rate of transmembrane transport of phenylalanine was significantly altered with extremity hyperinsulinemia. In conclusion, this study demonstrates that insulin directly stimulates muscle protein synthesis in severely injured patients.

Sepsis-induced failure of hepatic energy metabolism

HYPOTHESIS

Recent evidence suggests that sepsis may induce an uncoupling of oxidative phosphorylation. The purpose of this study was to quantify temporal changes in hepatic oxygen consumption and cellular energy state with increasing severity of sepsis and thus assess the interrelationship of these parameters as either primary defect or compensatory response.

MAIN OUTCOME MEASURES

Pseudomonas aeruginosa was infused intravenously in eight instrumented anesthetized swine inducing a progressive severity of sepsis to shock. Eight other animals served as instrumented controls. Hepatic blood flow, oxygen use, and concentrations of ATP, ADP, AMP, NAD(+), and NADH were measured at baseline and then sequentially during the study.

RESULTS

Except for an increase in heart rate, there were no temporal changes in measured values for the control animals. For swine receiving P. aeruginosa, hepatic oxygen delivery and consumption increased with early sepsis whereas there were no alterations in the concentrations of adenine nucleotides or NAD(+)/NADH within liver. Septic shock was notable for a decrease in oxygen delivery yet oxygen consumption remained elevated because of an increase in percent oxygen extraction. The hepatic concentrations of ATP and NADH decreased during septic shock.

CONCLUSIONS

These findings suggest that any sepsis-induced limitation in phosphorylation may be initially compensated by an increase in oxygen use. This study also suggests that decreases in NADH availability may be a principal factor in the decompensation of sepsis to shock.

Metabolic response of muscle to alanine, glutamine, and valine supplementation during severe illness

BACKGROUND

Alanine and glutamine are released from muscle in response to critical illness. Subsequent depletion of glutamine from muscle is proposed as a principal factor in the limitation of muscle protein synthesis in severely ill patients. The objective of this study was to assess the peripheral metabolic response to enteral supplementation of alanine, glutamine, and valine in critically ill patients.

METHODS

Isotopic tracers of alanine, glutamine, and phenylalanine were given IV to 6 critically ill patients and 6 healthy volunteers. Blood sampling from the femoral artery and vein along with muscle biopsies provided assessment of leg (ie, muscle) kinetics. Measurements were obtained during enteral nutrition alone and then with combined alanine (11.25 g), glutamine (7.5 g) and valine (11.25 g) supplementation for 3 hours.

RESULTS

Compared with healthy volunteers, critically ill patients had significantly reduced concentrations of alanine and glutamine in arterial plasma (p < .05), which increased significantly with amino acid supplementation. Muscle glutamine concentrations were significantly less in the patients and were not significantly affected by supplementation. Alanine and glutamine transport into and out of muscle and the rates of alanine and glutamine incorporation into and production from muscle were not affected by supplementation. Phenylalanine kinetics, as a marker of muscle protein metabolism, were not significantly altered by alanine, glutamine, and valine intake.

CONCLUSIONS

These results demonstrate that alanine, glutamine, and valine administration fails to significantly affect muscle glutamine availability or muscle protein metabolism. These findings suggest that accelerated muscle catabolism in critically ill patients is not in response to any deficiency in alanine or glutamine availability.

Exogenous nitric oxide increases basal leg glucose uptake in humans

This study addressed the role of blood flow and nitric oxide in leg glucose uptake. Seven subjects (5 men, 2 women) were studied during conditions of resting blood flow and increased blood flow, achieved by infusion of the nitric oxide (NO) donor sodium nitroprusside (SNP) into the femoral artery. Femoral arterial and venous blood samples were obtained and blood flow was determined by infusion of indocyanine green dye. SNP infusion significantly increased leg blood flow (769 +/- 103 v 450 +/- 65 mL. min(-1). leg(-1), P <.001), but did not affect arterial (4.68 +/- 0.13 mmol/L control, 4.63 +/- 0.09 mmol/L SNP) or venous (4.60 +/- 0.14 mmol/L control, 4.54 +/- 0.10 mmol/L SNP) glucose concentrations. Glucose uptake was significantly (P <.01) higher during SNP infusion (65 +/- 6 micromol. min(-1). leg(-1)) than during the basal period (34 +/- 6 micromol. min(-1). leg(-1)), whereas lactate release was unaffected (rest, 45 +/- 11 micromol. min(-1). leg(-1); SNP, 42 +/- 14 micromol. min(-1). leg(-1)). We conclude that blood flow and/or NO increase basal leg glucose uptake.

Increased tissue oxygen extraction and acidosis with progressive severity of sepsis

BACKGROUND

Lactic acidosis and increased production of CO(2) are common in septic shock. Presumably, both acidosis and CO(2) enhance the release of oxygen from hemoglobin. The purpose of this study was to assess the relationship of oxygen utilization, CO(2) production, acidosis, and hemoglobin oxygen (Hgb-O(2)) dissociation with progressive severity of sepsis to shock.

MATERIALS AND METHODS

Femoral arterial and vein, hepatic vein, portal vein, and pulmonary artery catheters were placed in 16 anesthetized swine. Organ blood flow was determined by timed injections of colored microspheres. After baseline measurements, Pseudomonas aeruginosa was infused in eight animals. This bacterial slurry was continued inciting a progression of sepsis to shock. Eight animals served as instrumented controls.

RESULTS

With sepsis and shock, there was a progressive decrease in pH and an increase in pCO(2) in plasma with all sampling sites (P < 0.01 septic shock versus baseline versus control). Blood flow to the liver and intestines increased with sepsis (P < 0.01) but then returned to near baseline control values during shock. VO(2) and/or percent O(2) extraction increased with sepsis and septic shock for the whole body and for the liver, intestine and leg (P < 0.01). There was a strong correlation between venous O(2) saturation, acidosis, and pCO(2) to percent O(2) extraction (r > 60; P < 0.0001). However, calculated P(50) values for Hgb-O(2) dissociation remained unchanged.

CONCLUSIONS

This study demonstrates that increased oxygen extraction in severe sepsis is related to a fall in tissue oxygen availability and not related to any allosteric change in Hgb-O(2) dissociation. Therefore, acidosis and hypercapnia do not have a demonstrable effect on altering oxygen availability during sepsis.

Metformin blunts stress-induced hyperglycemia after thermal injury

BACKGROUND

Hyperglycemia is associated with detriments in immune function and impaired wound healing. The purpose of this study was to assess the effect of metformin, an oral antihyperglycemic agent approved for patients with diabetes mellitus, on glucose metabolism in severely burned patients.

METHODS

Metformin was given in a double-blind, placebo-controlled fashion to 10 patients, all with burns > 60% body surface area (age, 36 +/- 4 years; weight, 92 +/- 3 kg; mean +/- SEM). After 8 days of metformin or placebo, glucose kinetics were quantitated using isotopic dilution with 6,6-d glucose and indirect calorimetry. Measurements were made during fasting; during an intravenous glucose infusion (30 micromol/kg/min); and during a hyperinsulinemic (500 mIU/m2/h), euglycemic clamp (mean plasma glucose concentration, 6.5 +/- 0.3 mmol/L).

RESULTS

During fasting, metformin-treated subjects had a significantly lower rate of endogenous glucose production (met. 9.6) and glucose oxidation than placebo control subjects. With the administration of intravenous glucose, metformin treatment significantly accelerated glucose clearance, thereby attenuating hyperglycemia. During hyperinsulinemia, glucose uptake was significantly greater in metformin-treated patients. Patients receiving metformin also had a significantly higher plasma concentration of insulin.

CONCLUSION

These findings suggest a potential clinical efficacy of metformin to reduce stress-induced hyperglycemia by increasing glucose clearance. This effect may be mediated by either a metformin-induced augmentation of insulin sensitivity or by increasing insulin availability.

Influence of fever on the hypermetabolic response in burn-injured children

BACKGROUND

Burn injury typically elicits a hypermetabolic response characterized by increased energy expenditure and muscle protein catabolism.

HYPOTHESIS

Fever further increases energy expenditure and muscle loss in otherwise highly hypermetabolic burn patients.

DESIGN

Retrospective analysis of experimental study.

SETTING

University hospital.

PATIENTS

Eighty-four children (aged 2-18 years) with burns covering 40% or more of total body surface area.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Simultaneous measurements of indirect calorimetry and leg net balance of phenylalanine (as an index of muscle protein catabolism) were obtained. Patients were stratified by their rectal temperature taken at the time of these metabolic measurements: afebrile (n = 28; temperature, <39.0 degrees C); mild fever (n = 26; temperature, 39.0 degrees C-39.4 degrees C); moderate fever (n = 18; temperature, 39.5 degrees C-39.9 degrees C); or severe fever (n = 12; temperature, > or =40.0 degrees C).

RESULTS

Febrile and afebrile patients were similar in age, body weight, and extent of burn area. Severe fever was associated with significantly increased resting energy expenditure (mean +/- SD resting energy expenditure-predicted basal, 1.38 +/- 0.39 for afebrile patients vs 1.68 +/- 0.30 for patients with severe fever; P<.05) and a greater net loss of phenylalanine from the leg (net balance of phenylalanine, -6.0 +/- 6.2 mg/min per 100 mL of leg volume for afebrile patients vs -10.8 +/- 7.2 mg/min per 100 mL for patients with severe fever; P<.05). Patient groups were similar in plasma glucose concentration and extent of leukocytosis.

CONCLUSIONS

These findings demonstrate the association of severe fever with further increase in energy expenditure and muscle protein catabolism in otherwise hypermetabolic burned children. This suggests a possible metabolic benefit in attenuating fever in such patients.

The use of abdominal computed tomography scan decreases the frequency of misdiagnosis in cases of suspected appendicitis

BACKGROUND

Despite considerable experience the reported frequency of misdiagnosis in patients undergoing appendectomy continues in the range of 20% to 40% in some populations.

METHODS

We developed a clinical guideline that recommended abdominal computed tomography (CT) for all nonpregnant adults in whom the diagnosis of appendicitis was suspected unless the diagnosis could be ruled out clinically. The records of adult patients that underwent appendectomy from July 1998 through October 2001 were reviewed. The clinical guideline was developed in July 2000.

RESULTS

There were 194 appendectomies performed, 114 prior to the guideline and 80 after the development of the guideline. The rate of misdiagnosis decreased from 25% to 6% (P <0.05), the rate of CT use increased from 32% to 84% (P <0.05), and the perforation rate remained unchanged.

CONCLUSIONS

These results support the effectiveness of a clinical guideline that encourage the use of abdominal CT in decreasing the frequency of misdiagnosis in cases of suspected appendicitis.

Glutamine supplementation fails to affect muscle protein kinetics in critically ill patients

BACKGROUND

In vitro work suggests that glutamine availability may be an important factor in controlling the rate of muscle protein synthesis. The objective of this study was to determine if enteral administration of glutamine affects muscle protein metabolism in critically ill patients.

METHODS

Six postsurgical patients requiring prolonged mechanical ventilation for pneumonia (age, 51 +/- 12 years, Acute Physiology and Chronic Health Evaluation [APACHE] 22 +/- 6, mean +/- SEM) and 6 normal healthy volunteers (age, 33 +/- 4 years) underwent evaluation of whole body and muscle protein metabolism using an 8-hour infusion of d5-phenylalanine, 5(15)N glutamine, and d3-alanine with serial blood sampling from the femoral artery and vein and biopsies from the vastus lateralis muscle. Metabolic measurements were obtained while subjects received Peptamen enterally (Basal Period) and with glutamine supplementation (24 g/3 h; Glutamine Period).

RESULTS

Glutamine concentration in muscle was significantly less in the critically ill patients. Glutamine supplementation increased the arterial plasma concentration of glutamine, yet with no demonstratable effect on muscle glutamine concentration or on the rate of muscle protein synthesis in either volunteers or patients. Furthermore, muscle glutamine kinetics (incorporation into muscle, release from muscle, and rate of de novo glutamine synthesis in muscle) were not affected by glutamine supplementation in the critically ill patients. In contrast, there was a significant decrease in these kinetic parameters with glutamine supplementation within the muscle of healthy subjects. Metabolism of alanine was unaffected by administration of glutamine in either group.

CONCLUSIONS

Enteral glutamine supplementation to critically ill patients fails to alter muscle glutamine metabolism or muscle protein synthesis. This suggests a possible restriction in transport of glutamine into muscle of critically ill patients.

Hyperglycemia exacerbates muscle protein catabolism in burn-injured patients

OBJECTIVE

The purpose of this study was to assess if hyperglycemia influences energy expenditure or the extent of muscle protein catabolism in severely burned adults.

DESIGN

Retrospective study.

SETTING

Burn intensive care unit at a university hospital.

PATIENTS

Adults with burns on >/=40% of their body surface area.

INTERVENTIONS

Simultaneous measurement of indirect calorimetry and leg net balance of phenylalanine (as an index of muscle protein catabolism). Patients were stratified by plasma glucose values at the time of metabolic measurements (i.e., normal, glucose at </=130 mg/dL; mild hyperglycemia, glucose at 130-200 mg/dL; severe hyperglycemia, glucose at >200 mg/dL).

MEASUREMENTS AND MAIN RESULTS

Normal (n = 9; plasma glucose, 109 +/- 13 mg/dL [mean +/- sd]), mildly hyperglycemic (n = 13l plasma glucose, 156 +/- 17 mg/dL), and severely hyperglycemic subjects (n = 7, glucose 231 +/- 32 mg/dL) were similar in age, body weight, extent of burn area, and daily caloric intake. Severe hyperglycemia was associated with significantly higher arterial concentrations of phenylalanine (normal, 0.079 +/- 0.027 micromol/L; severe hyperglycemia, 0.116 +/- 0.028; p <.05) and a significantly greater net efflux of phenylalanine from the leg (normal, -0.067 +/- 0.072 micromol.min(-1).100 mL(-1) leg volume; severe hyperglycemia, -0.151 +/- 0.080 micromol.min(-1).100 mL(-1) leg volume; p <.05). Resting energy expenditure and respiratory quotient were similar between patient groups.

CONCLUSIONS

These findings demonstrate an association between hyperglycemia and an increased rate of muscle protein catabolism in severely burned patients. This suggests a possible link between resistance of muscle to the action of insulin for both glucose clearance and muscle protein catabolism.

Relative influence of glucose and insulin on peripheral amino acid metabolism in severely burned patients

BACKGROUND

Protein catabolism and glucose intolerance are prominent in critically injured patients. The objective of this study was to assess if glucose or insulin availability influences the extent of protein catabolism in hypermetabolic patients.

METHODS

Amino acid net balance from the leg was quantitated in 6 severe burn victims. Furthermore, whole body and leg protein kinetics were assessed with 2H5 phenylalanine and 15N alanine. Measurements were obtained after a 9-hour fast, during an IV glucose infusion (30 micromol/kg per minute), and during a hyperinsulinemic (500 mIU/kg per minute) euglycemic clamp.

RESULTS

Compared with fasting values, the administration of glucose resulted in a significantly increased efflux of amino acids from the leg. In contrast, insulin administration significantly decreased the cumulative net efflux of amino acids. During hyperinsulinemia, isotopic measurements demonstrated a significant decrease in alanine appearance and an increase in phenylalanine disappearance into the leg.

CONCLUSIONS

These findings demonstrate that in critically injured patients, acute hyperglycemia increases muscle catabolism despite an endogenous insulin response. In contrast, exogenous insulin given in sufficient amount impedes muscle protein loss. The mechanism for this anabolic effect of insulin may vary between different amino acids.

Nutritional support

Despite the increasing obesity of the American population, many chronically ill patients are malnourished. When this malnutrition is combined with the hypermetabolic response and protein catabolism of an acute event, such as an operation, nutritional support becomes an important facet for optimal critical care. This chapter reviews the basic tenants of nutritional support with special emphasis on patients with pulmonary compromise. Important aspects of caloric and protein support are discussed and enteral nutrition is emphasized because of its numerous advantages and documented improvement in outcome.

Impact of discontinuing a hospital-based air ambulance service on trauma patient outcomes

BACKGROUND

The clinical benefit of aeromedical transportation of injured patients in the civilian population has been debated. The purpose of this study was to examine the effects of discontinuing a hospital-based helicopter transport program on trauma patient outcomes, with the hypothesis that the loss of an air ambulance would result in increased transport time and increased mortality among severely injured patients.

METHODS

Data on injury severity and patient outcomes were collected prospectively for the 12 months immediately preceding and 24 months following discontinuation of the helicopter ambulance service. Transport time, mortality rate, and hospital length of stay was compared.

RESULTS

The number of trauma patient admissions decreased 12%, with a 17% decrease in admissions of severely injured patients. Transport time decreased, with no change in mortality.

CONCLUSION

Discontinuation of a hospital-based air ambulance service did not increase transport time or increase mortality for trauma patients.

Association of hyperglycemia with increased mortality after severe burn injury

BACKGROUND

Hyperglycemia is commonly associated with the hypermetabolic stress response. However, persistent hyperglycemia may adversely affect wound healing and immunity. The purpose of this study was to assess any relationship between hyperglycemia and clinical outcome after severe burn injury.

METHODS

Survey of the medical records from January 1996 to July 1999 identified 58 pediatric patients with burns > or = 60% body surface. Patients were categorized as having poor glucose control (n = 33) if > or = 40% of all plasma glucose determinations were > or = 7.8 mmol/L (140 mg/dL) and compared with patients deemed to have adequate glucose control (n = 25) in whom > or = 40% of all glucose values were > or = 7.8 mmol/L.

RESULTS

Despite similar age, burn size, caloric intake, and frequency of wound infection, patients categorized with poor glucose control had a significantly greater incidence of positive blood cultures (positive blood cultures/length of stay days, 0.42 +/- 0.04 for hyperglycemia patients vs. 0.30 +/- 0.03 for normoglycemia patients; mean +/- SEM, p > or = 0.05). This finding was especially prominent for blood cultures positive for yeast. Hyperglycemia patients had significantly less percentage of skin graft take than did the normoglycemic patients (percent take/operative procedure, 64 +/- 9 for hyperglycemia patients vs. 88 +/- 5 for normoglycemia patients; p < 0.05). Nine patients (27%) with persistent hyperglycemia died compared with only one death (4%) in patients with adequate glucose control (p > or = 0.05).

CONCLUSION

This association between poor glucose control, bacteremia/fungemia, reduced skin graft take, and subsequent mortality in severely burned children may be related to a hyperglycemia-induced detriment in antimicrobial defense. Although this report fails to establish cause and effect, these findings suggest that aggressive maneuvers to normalize plasma glucose in critically injured patients may be warranted.

Measurement of hemoglobin synthesis rate in vivo using a stable isotope method

We developed a method to measure hemoglobin synthesis rate (SynHb) in humans, assuming that free glycine in the red blood cell (RBC) represents free glycine in bone marrow for hemoglobin synthesis. The present rat study examines this assumption of the method and quantifies SynHb in rats. Sprague-Dawley rats (n = 9) were studied, [2-(13)C]glycine was intravenously infused over 24 h (2.5 mg kg(-1) h(-1)), blood was drawn for glycine and heme isolation, and bone marrow was harvested for glycine isolation. Isotopic enrichments of glycine and heme were measured, fractional hemoglobin synthesis rate (fSynHb% day(-1)) was calculated, and from this a value for SynHb (mg g(-1) day(-1)) was derived. Mean body weight was 446 +/- 10 g (mean +/- SE) and hemoglobin concentration was 14 +/- 0.5 g dl(-1). At 24 h, the mean isotopic enrichment, atom percentage excess (APE), of the RBC free glycine (1.56 +/- 0.18 APE) was similar to the bone marrow (1.68 +/- 0.15 APE). The rate of incorporation of (13)C into heme increased over time from 0.0004 APE/h between 6 and 12 h, to 0.0014 APE/h between 12 and 18 h, and 0.0024 APE/h between 18 and 24 h. Consequently, fSynHb (1.19 +/- 0.32, 2.92 +/- 0.66, and 4.22 +/- 0.56% day(-1), respectively) and SynHb (0.11 +/- 0.03, 0.28 +/- 0.05, and 0.42 +/- 0.05 mg g(-1) day(-1), respectively) showed similar patterns over the 24-h study period. We conclude that (1) enrichment of free glycine in the circulating RBC approximates enrichment of bone marrow free glycine for heme formation and (2) this pattern of hemoglobin synthesis rate is reflecting the characteristic release and gradual maturation of reticulocytes in the circulation.

Influence of glucose kinetics on plasma lactate concentration and energy expenditure in severely burned patients

BACKGROUND

In critically ill patients, elevation in the plasma lactate concentration has traditionally been interpreted as indicating a deficiency in oxygen availability and is often an impetus to increase oxygen delivery clinically. However, another possible basis for increased lactate concentrations may be simply a mass effect from increased pyruvate availability (i.e., accelerated glycolysis).

METHODS

In six hypermetabolic burned patients, the rates of glucose production and oxidation were quantified using a tracer infusion of 6,6 d2 glucose combined with indirect calorimetry. Measurements were obtained after a 9-hour fast and after a 3-hour infusion of unlabeled glucose at 30 micromol/kg/min. No patient was overtly septic, hypoxic, or hypovolemic.

RESULTS

The infusion of glucose significantly increased the arterial glucose concentration and rate of glucose oxidation, with a corresponding increase in the arterial plasma concentration of lactate and pyruvate. Resting energy expenditure and oxygen consumption were not affected by the infusion of glucose.

CONCLUSIONS

These findings show that elevations in plasma lactate in severely injured patients may, in part, be related to increases in glucose flux and not entirely a reflection of any deficit in oxygen availability. Such findings highlight a potential pitfall for interpreting plasma lactate concentrations as an index of tissue oxygen availability in hypermetabolic patients.

Determinants of skeletal muscle catabolism after severe burn

OBJECTIVE

To determine which patient factors affect the degree of catabolism after severe burn.

SUMMARY BACKGROUND DATA

Catabolism is associated with severe burn and leads to erosion of lean mass, impaired wound healing, and delayed rehabilitation.

METHODS

From 1996 to 1999, 151 stable-isotope protein kinetic studies were performed in 102 pediatric and 21 adult subjects burned over 20-99. 5% of their total body surface area (TBSA). Patient demographics, burn characteristics, and hospital course variables were correlated with the net balance of skeletal muscle protein synthesis and breakdown across the leg. Data were analyzed sequentially and cumulatively through univariate and cross-sectional multiple regression.

RESULTS

Increasing age, weight, and delay in definitive surgical treatment predict increased catabolism (P < .05). Body surface area burned increased catabolism until 40% TBSA was reached; catabolism did not consistently increase thereafter. Resting energy expenditure and sepsis were also strong predictors of net protein catabolism. Among factors that did not significantly correlate were burn type, pneumonia, wound contamination, and time after burn. From these results, the authors also infer that gross muscle mass correlates independently with protein wasting after burn.

CONCLUSIONS

Heavier, more muscular subjects, and subjects whose definitive surgical treatment is delayed are at the greatest risk for excess catabolism after burn. Sepsis and excessive hypermetabolism are also associated with protein catabolism.

Both dermal matrix and epidermis contribute to an inhibition of wound contraction

Contracture is a major detriment to functional recovery from large wounds. To determine the relative value of dermal replacement and epidermal coverage in inhibiting wound contraction, five full-thickness wounds (all 5 x 5 cm2) were placed on the back of 8 swine and treated in the following manner: (1) open wound, (2) porcine acellular dermis (analogous to AlloDerm for human use), (3) porcine acellular dermis with epidermal autograft placed 7 days postwounding, (4) porcine acellular dermis with immediate epidermal autograft, and (5) conventional-thickness autograft. Scar dimensions and punch biopsies were taken at days 14 and 30 postwounding. The planimetry results demonstrated that wound contraction was significantly greater with the open wounds (group 1) than all other wounds with a dermal substitute. Furthermore, wounds with initial epidermal coverage had significantly less contraction than unepithelialized wounds (14.8 +/- 1.1 cm2 at day 14 in wound group 2 vs. 20.4 +/- 0.6 cm2 in wound group 4; p < 0.05). Biopsy results revealed that wounds with initial epithelial coverage had the least amount of inflammation. These findings suggest that both dermal matrix and epidermal coverage contribute to an inhibition of wound contraction and that prompt epithelial coverage appears to impede contraction by reducing inflammation.

Gut gavage with antiendotoxin antibodies reduces the liberation of tumor necrosis factor-alpha after hemorrhage/resuscitation

OBJECTIVE

To evaluate the effect of gut gavage both alone and with enteral administration of monoclonal antibodies to endotoxin on the liberation of tumor necrosis factor (TNF)-alpha and subsequent hemodynamics after hemorrhage/resuscitation.

DESIGN

Dose response intervention, sham-controlled animal study.

SETTING

Research laboratory at a university medical center.

ANIMALS

Instrumented rats (250-325 g body weight) underwent standardized hemorrhage/resuscitation.

INTERVENTIONS

Animal groups received 4 hrs before hemorrhage/resuscitation: gastric gavage with Colyte alone (group 1), combined with E5 antiendotoxin at either 0.2 mg/100 g (group 2) or 2 mg/100 g body weight (group 3), or sham controls (group 4). There were six animals studied in each of the four groups.

MEASUREMENTS AND MAIN RESULTS

For animals receiving gut gavage and high-dose E5 antiendotoxin, plasma concentrations of TNF-alpha (pg/mL) at 120 mins after hemorrhage/resuscitation were significantly lower compared with sham controls (16+/-4 group 3; 65+/-36 group 4; mean +/- SD, p < .05). At 300 mins, this same treatment group had a significantly higher mean blood pressure (mm Hg) (110+/-6 group 3; 86+/-7 group 4: p < .05). Also at 300 mins after hemorrhage/resuscitation, plasma lactate concentrations (mmol/L) were significantly lower for all gut gavage treatment groups compared with sham control animals (1.9+/-0.2 group 1; 2.0+/-0.2 group 2; 1.8+/-0.2 group 3; 4.8+/-2.8 group 4, p < .05).

CONCLUSIONS

Prior treatment with gut gavage and enterally administered antiendotoxin antibodies reduces TNF-alpha liberation after hemorrhage/resuscitation and confers a subsequent improvement in hemodynamics and decreased plasma lactate concentrations. Such therapy may be efficacious in patients undergoing elective procedures where major hemorrhage is likely or in severely injured patients with continued or recurrent hemorrhage.

Complementary roles of laparoscopic abdominal exploration and diagnostic peritoneal lavage for evaluating abdominal stab wounds: a prospective study

PURPOSE

To determine the roles of laparoscopic abdominal exploration (LE) and diagnostic peritoneal lavage (DPL) in the evaluation of abdominal stab wounds, we prospectively compared LE with mandatory celiotomy (MC) in 76 patients having anterior abdominal stab wounds penetrating the fascia over a 22-month period.

PATIENTS AND METHODS

Twenty-two patients underwent emergency celiotomy. The remaining patients were subjected to DPL and assigned to treatment by either celiotomy or initial LE with subsequent conversion to open exploration at the discretion of the attending surgeon.

RESULTS

Laparotomy was avoided in 55% of the 31 patients undergoing initial laparoscopy, and this group demonstrated a significant decrease in the incidence of nontherapeutic celiotomy, from 19% to 57% (P < 0.05), as well as decreased length of hospital stay (4 +/- 0.6 v 5.9 +/- 0.4 days; P < 0.05), and total hospital cost ($6119 +/- 756 v $8312 +/- 627; P < 0.05). There were no missed intraabdominal injuries or morbidity from laparoscopy identified in follow-up. The DPL (N = 36) was positive in 11 of the 12 patients with injury requiring surgical repair and was negative in 16 of the 25 patients not requiring repair. The sensitivity and specificity of DPL were 0.91 and 0.64 compared with 1.0 and 0.74 for laparoscopy.

CONCLUSIONS

An algorithm to evaluate stable patients with anterior abdominal stab wounds and minimize overall costs of care, incidence of nontherapeutic celiotomy, and rate of missed injuries is suggested consisting of DPL followed by observation in patients with negative DPL and by laparoscopy in patients with positive DPL. Wounds to the thoracoabdominal region may be best evaluated by initial LE, as diaphragmatic wounds may result in a false-negative DPL.

Deficiency in peripheral glutamine production in pediatric patients with burns

Plasma glutamine levels decrease in association with severe injury, which suggests that the consumption of glutamine exceeds the production of glutamine or possibly represents a deficit in the release of glutamine from skeletal muscle. The goal of this study was to assess the peripheral glutamine kinetic response to prolonged stress in children with critical injuries. To accomplish this purpose, we quantitated peripheral glutamine kinetics in vivo with the use of 5N15 glutamine in 5 children with severe burns (total body surface area, 74%+/-14%; mean +/- SEM) and 3 children who underwent elective scar reconstruction. In the children with severe burns, leg blood flow was significantly elevated (16.2+/-2.1 vs 7.5 +/-0.3 mL/min/100 mL leg volume, P < .02) and the arterial concentration of glutamine was significantly reduced (0.31+/-0.04 vs 0.84+/-0.05 mmol/L, P < .001). The rate of glutamine turnover within the leg was significantly reduced in the patients with acute burns, whereas the net efflux of glutamine was similar between the 2 groups. These findings suggest that plasma glutamine concentrations decrease during severe stress as a result of a deficit in peripheral glutamine release in conjunction with an increased central consumption. This preliminary study supports the notion that exogenous glutamine supplementation in pediatric patients with severe injuries may be needed because of this inadequate skeletal muscle response.

Combined effects of hyperaminoacidemia and oxandrolone on skeletal muscle protein synthesis

We investigated whether the normal anabolic effects of acute hyperaminoacidemia were maintained after 5 days of oxandrolone (Oxandrin, Ox)-induced anabolism. Five healthy men [22 +/- 3 (SD) yr] were studied before and after 5 days of oral Ox (15 mg/day). In each study, a 5-h basal period was followed by a 3-h primed-continuous infusion of a commercial amino acid mixture (10% Travasol). Stable isotopic data from blood and muscle sampling were analyzed using a three-compartment model to calculate muscle protein synthesis and breakdown. Model-derived muscle protein synthesis increased after amino acid infusion in both the control [basal control (BC) vs. control + amino acids (C+AA); P < 0.001] and Ox study [basal Ox (BOx) vs. Ox + amino acids (Ox+AA); P < 0.01], whereas protein breakdown was unchanged. Fractional synthetic rates of muscle protein increased 94% (BC vs. C+AA; P = 0.01) and 53% (BOx vs. Ox+AA; P < 0.01), respectively. We conclude that the normal anabolic effects of acute hyperaminoacidemia are maintained in skeletal muscle undergoing oxandrolone-induced anabolism.

Androstenedione does not stimulate muscle protein anabolism in young healthy men

Androstenedione is the immediate precursor of testosterone. Androstenedione intake has been speculated to increase plasma testosterone levels and muscle anabolism. Thus, androstenedione supplements have become widely popular in the sport community to improve performance. This study was designed to determine whether 5 days of oral androstenedione (100 mg/day) supplementation increases skeletal muscle anabolism. Six healthy young men were studied before the treatment period and after 5 days of oral androstenedione supplementation. Muscle protein turnover parameters were compared to those of a control group studied twice as well and receiving no treatment. We measured muscle protein kinetics using a three-compartment model involving infusion of L-[ring-2H5]phenylalanine, blood sampling from femoral artery and vein, and muscle biopsies. Plasma testosterone, androstenedione, LH, and estradiol concentrations were determined by RIA. After ingestion of oral androstenedione, plasma testosterone and LH concentrations did not change from basal, whereas plasma androstenedione and estradiol concentrations were significantly increased (P<0.05). Compared to a control group, androstenedione did not affect muscle protein synthesis and breakdown, or phenylalanine net balance across the leg. We conclude that oral androstenedione does not increase plasma testosterone concentrations and has no anabolic effect on muscle protein metabolism in young eugonadal men.

Accelerated glutamine synthesis in critically ill patients cannot maintain normal intramuscular free glutamine concentration

BACKGROUND

Muscle glutamine is severely depleted in critically ill patients (by approximately 50% to 80% of normal). Because muscle protein breakdown, and thus the release of glutamine from muscle protein, is enhanced in response to metabolic stress, the depletion of intramuscular glutamine could be due to its impaired synthesis or accelerated outward transport or both.

METHODS

To distinguish these possibilities, we measured skeletal muscle glutamine metabolism in five critically ill patients by means of primed, continuous infusions of 5-15N-glutamine and ring-2H5-phenylalanine and compared them to values we previously reported for healthy volunteers.

RESULTS

The intramuscular free glutamine concentration in patients was approximately 70% of that in healthy volunteers (5.8 +/- 0.6 mmol/L intracellular free water vs 21.5 +/- 2.8 mmol/L). Whole-body glutamine rate of appearance was 5.8 +/- 1.0 micromol x kg (-1) body wt x min (-1), and whole-body clearance was 19.3 +/- 3.3 mL x kg(-1) x min (-1). Despite the low intramuscular glutamine concentration in the patients, the rate of unidirectional outward transport from skeletal muscle into venous blood (1.1. +/- 0.2 micromol x 100 mL x leg(-1) x min(-1)) was similar to that observed in healthy volunteers (1.6 +/- 0.2 mol x 100 mL x leg(-1) x min(-1)); intramuscular synthesis was 2.7 +/- 0.9 micromol x 100 mL x leg(-1) x min(-1) compared with a normal value of 0.6 +/- 0.06 micromol x 100 mL x leg(-1) x min(-1). Net balance across the leg was normal.

CONCLUSIONS

The depletion of intramuscular glutamine in critically ill patients is not due to an impairment of the rate of synthesis. In fact, accelerated glutamine production cannot maintain normal intramuscular glutamine levels because of accelerated outward transport.

Bronchoscopic lavage with perfluorocarbon decreases postprocedure hypoxemia in an ovine model of smoke inhalation

OBJECTIVE

Bronchoscopy and lavage are used to confirm diagnosis and can be therapeutic in patients suffering inhalation injury. Lavage is traditionally performed using saline, which is unfortunately associated with profound transient hypoxemia. Perfluorocarbons, having a high gas solubility for oxygen and carbon dioxide, increase oxygenation when instilled into the airway. We hypothesized that the use of perfluorocarbons for bronchoscopic lavage would attenuate this transient hypoxemia.

METHODS

Sheep were prepared for chronic study. They were insufflated with cotton smoke and then randomized to receive a lavage with 200 mL of perfluorocarbon or saline at 2, 6, 12, and 24 hours after injury.

RESULTS

All animals had a steady and significant decline in their pre- to post-PaO2/FiO2 (P/F) ratio. At 2, 6, and 12 hours, the saline lavage group had a significant decrease in their P/F ratio (485+/-32 to 212+/-37 mm Hg, 439+/-22 to 170+/-40 mm Hg, and 381+/-48 to 184+/-59 mm Hg). This decrease in P/F ratio was not observed in the perfluorocarbon group (474+/-19 to 459+/-29 mm Hg, 424+/-32 to 387+/-43 mm Hg, and 366+/-50 to 357+/-67 mm Hg).

CONCLUSION

These findings indicate that perfluorocarbons attenuate the transient hypoxemia associated with saline bronchoscopic lavage and thus may be considered safer for patients with acute lung injury.

Hemodynamic and ventilatory effects associated with increasing inverse inspiratory-expiratory ventilation

BACKGROUND

Increasing the percentage of inspiratory time during mechanical ventilation (i.e., inverse inspiratory-expiratory (I:E) ventilation) is frequently used to improve oxygenation in patients with acute respiratory distress syndrome; however, an optimal I:E ratio is unknown.

METHODS

To assess for an optimal I:E ratio, hemodynamic, ventilatory, and oxygenation parameters were determined in eight adult trauma patients with acute respiratory distress syndrome supported with pressure-control ventilation. An indwelling pulmonary artery catheter facilitated the extensive measurements as I:E ratios were randomly changed between 1:1 and 3:1. Measurements were determined 30 minutes after each change in the I:E ratio.

RESULTS

Increasing the percentage of inspiratory time resulted in a progressive increase in arterial oxygenation (p < 0.05) in conjunction with elevations in mean airway pressure (p < 0.05) and a decrease in alveolar-arterial oxygen difference (p < 0.05). Furthermore, progressive reversal of the I:E ratio significantly diminished alveolar ventilation (p < 0.01), with worsening dynamic compliance (p < 0.01). There were no demonstrable changes in hemodynamics.

CONCLUSION

These findings demonstrate the effectiveness of increasing inspiratory time to improve oxygenation, yet to the detriment of ventilation. This suggests that within the parameter confines of this study, the preferential I:E ratio is a balance between oxygen demands and ventilatory requirements.

Outcome and cost analysis for outpatient skin grafting

BACKGROUND

To reduce cost, outpatient surgery is advocated when feasible; however, the potential of compromising outcome is a concern. The purpose of this review is to assess patient outcome and cost for managing operative burn injuries without hospitalization.

METHODS

During the past 18 months, 54 patients were identified with burns amenable to operative debridement and skin grafting without hospitalization. Twenty patients chose to be hospitalized and underwent prompt skin grafting. Operative skin grafting as an outpatient was chosen by the remaining 34 patients. Of these, four patients were subsequently hospitalized postoperatively (two for pain, one for cellulitis, and one for vomiting).

RESULTS

Hospitalized patients and outpatients were similar in age and extent of burn; however, those hospitalized underwent skin grafting sooner after injury (2.1 +/- 0.4 days for inpatients vs. 11.5 +/- 0.8 days for outpatients; mean +/- SEM). Inpatients also had a significantly larger area skin-grafted (286 +/- 24 cm2 for inpatients vs. 178 +/- 14 cm2 for outpatients). Graft take was very good in each group. Cost, as indexed by patient charge, was substantially less for outpatients ($2,397 +/- $222) than for inpatients ($17,220 +/- $410).

CONCLUSION

These results demonstrate a significant cost reduction with nonhospitalized operative care of burn injuries without any overt detriment in outcome, thus endorsing outpatient skin grafting when amenable. This review also illustrates that delaying operative intervention reduces the burn area required for grafting.

Assessment of human colon cancer protein kinetics in vivo

BACKGROUND

Malignancies enlarge because protein synthesis exceeds the rate of breakdown; however, the specific protein kinetic pattern remains unknown. Determining in vivo protein kinetic rates for a tumor may be useful for quantifying individual responses to a specific therapy. The aim of this study was to assess whether the growth of tumors is related to an increase in protein synthesis or an inhibition of protein breakdown.

METHODS

Five patients (age, 59 +/- 3 years) with adenocarcinoma of the colon undergoing colonoscopy were studied. Tissue protein synthesis and breakdown rates were measured in vivo for both segments of colon cancer and adjacent normal-appearing colonic mucosa by using a primed, continuous infusion of 1(13)C leucine with tissue biopsy and quantitation of regional blood flow by laser Doppler flowmetry.

RESULTS

Segments of colon cancer had a significantly (p < 0.05) greater rate of protein synthesis as quantitated by both the fractional rate of protein synthesis (Ca 45.4% +/- 5.0%/day versus nl mucosa 35.7% +/- 3.1%/day; mean +/- SEM) and by the tissue synthesis rate (Ca 69.4 +/- 9.0 versus nl mucosa 51.6 +/- 5.2 mumol/L leucine/day/100 gm tissue). Regional blood flow was significantly elevated in the cancer (Ca 110.9 +/- 5.8 versus nl mucosa 91.2 +/- 2.9 ml/min/100 gm), which contributed to commensurate rates of tissue breakdown (Ca 28.6 +/- 2.0 versus nl mucosa 28.2 +/- 2.4 mumol/L leucine/day/100 gm).

CONCLUSIONS

These results illustrate that human colon cancers grow in vivo as a result of increases in protein synthesis. Furthermore, increases in regional blood flow limit the rate of tissue protein breakdown of colon cancer, thereby contributing to growth of the malignancy. These findings support the contention that therapeutic strategies aimed at negating this inherent increase in protein synthesis or limiting blood flow may effectively limit the growth of malignancies. This methodology may also provide an index for evaluating the effectiveness of future therapies aimed at reducing tumor growth for individual patients.

Infusion of hot crystalloid during operative burn wound debridement

BACKGROUND

Hypothermia exacerbates coagulopathy and is thus a potentially devastating morbidity during operative debridement of burn wounds. Current techniques for maintaining body temperature include warming intravenous fluids at 38 degrees C. The purpose of this study was to assess the safety of infusing saline heated to 55-60 degrees C.

METHODS

Using a modified fluid warmer, saline heated to 60 degrees C was infused through central venous access in eight adult patients undergoing debridement of burn wounds. The temperature of the saline actually entering the patient was measured by a thermocouple attached at the connection to the central line catheter.

RESULTS

The actual infusate temperature was 54.0 +/- 1.2 degrees C. Over the first hour, 1,100 mL of hot saline was given, thus delivering 17.6 kcal more heat than fluid warmed to the traditional 38 degrees C. Core temperature measured via esophageal and Foley catheters had an insignificant trend toward increase during the operative procedure. There was no evidence of intravascular hemolysis or coagulopathy.

CONCLUSION

This pilot study suggests that infusion of hot crystalloids given via central venous access is safe and may be an acceptable adjuvant in attenuating hypothermia during operative procedures.

Lactic acidosis during sepsis is related to increased pyruvate production, not deficits in tissue oxygen availability

OBJECTIVE

The purpose of this study was to quantitate the derangements in intermediary carbohydrate metabolism and oxygen use in severely septic patients in comparison with healthy volunteers.

SUMMARY BACKGROUND DATA

It commonly has been assumed that the development of lactic acidosis during sepsis results from a deficit in tissue oxygen availability. Dichloroacetate (DCA), which is known to increase pyruvate oxidation but only when tissue oxygen is available, provides a means to assess the role of hypoxia in lactate production.

METHODS

Stable isotope tracer methodology and indirect calorimetry was used to determine the rates of intermediary carbohydrate metabolism and oxygen use in five severely septic patients with lactic acidosis and six healthy volunteers before and after administration of DCA.

RESULTS

Oxygen consumption and the rates of glucose and pyruvate production and oxidation were substantially greater (p < 0.05) in the septic patient compared with healthy volunteers. Administration of DCA resulted in a further increase in oxygen consumption and the percentage of glucose and pyruvate directed toward oxidation. Dichloroacetate also decreased glucose and pyruvate production, with a corresponding decrease in plasma lactate concentration.

CONCLUSIONS

These findings clearly indicate that the accumulation of lactate during sepsis is not the result of limitations in tissue oxygenation, but is a sequelae to the markedly increased rate of pyruvate production. Furthermore, the substantially higher rate of pyruvate oxidation in the septic patients refutes the notion of a sepsis-induced impairment in pyruvate dehydrogenase activity.

Surgically placed gastro-jejunostomy tubes have fewer complications compared to feeding jejunostomy tubes

OBJECTIVE

During laparotomy, jejunostomy tubes (J tubes) are often placed to provide access for enteral nutrition in the immediate postoperative period. However, the placement of such tubes may be associated with potentially devastating intra-abdominal complications possibly related to the tenuous security of a tube through the small bowel wall. An alternative method for enteral nutrition access is to surgically place a "PEG-J" tube (i.e., surgical G/J tube) thus providing for jejunal feedings via a gastrotomy without a jejunotomy. The purpose of this study is to assess whether surgically placed G/J tubes reduce the postoperative complications in comparison to feeding J tubes.

METHODS

Over the past 18 months, 92 J tubes and 56 G/J tubes were placed during laparotomy at a single institution and the method chosen by surgeons' preference. The frequency of complications associated with each tube was determined by review of the postoperative medical records.

RESULTS

There was no enteric leakage in those patient given G/J tubes (p < 0.05). Furthermore 10% of the patients receiving J tubes required operative repair of a J tube complication while no patient with an access complication following G/J tube placement required surgical repair (p < 0.05).

CONCLUSIONS

These results demonstrate that operative positioning of a jejunal feeding tube through a gastrostomy tube (surgical G/J tube) provides a safer route for enteral nutrition than does direct tube placement via the jejunal wall, by significantly reducing both the incidence of enteric leakage and the requirement for operative repair.

In vivo metabolic response of glucose to dichloroacetate in humans

Hyperglycemia is common in severely ill patients and is related principally to an increase in glucose production. Dichloroacetate (DCA), which is known to increase the rate of pyruvate oxidation, has been shown to lower plasma glucose concentrations in normal fasting subjects and in diabetics and thus may be efficacious in treating stress induced hyperglycemia. However, the mechanism by which DCA lowers the plasma glucose concentration in humans has not been elucidated. To examine the human in vivo metabolic alterations induced by DCA, six fasting volunteers were infused with 6,6-D2-glucose and indirect calorimetry was performed prior to and following DCA administration. Glucose, lactate, and alanine net balance across the leg were also quantitated. Following DCA administration, plasma glucose concentrations decreased by 9% due to a proportional decrease in the rate of glucose production (P < 0.05). DCA had no affect on glucose clearance or leg net balance; however, the rate of glucose oxidation increased by 24% from baseline (P < 0.05). This increase in glucose oxidation without a compensatory change in peripheral glucose consumption suggests an improved efficiency in peripheral glucose utilization induced by DCA. Plasma concentrations of lactate and alanine were also lowered by DCA (56% for lactate, 66% for alanine, P < 0.05) without a significant alteration in leg net balance. These results suggest that DCA may decrease gluconeogenesis by limiting the availability of the precursor substrates lactate and alanine. Thus dichloroacetate may be an appropriate alternative to insulin in correcting mild elevations in plasma glucose concentrations. Furthermore, DCA may be especially effective in severely ill patients where hyperglycemia is largely due to increases in gluconeogenesis.

Colloid infusions reduce glomerular filtration in resuscitated burn victims

OBJECTIVE

Colloids are used clinically to minimize edema yet may have detrimental consequences on glomerular filtration. The purpose of this study is to assess the renal and hormonal effects of colloid supplementation in the fluid resuscitation of burn victims.

DESIGN

Analytic cohort study.

MATERIAL AND METHODS

Immediately following their 24 hour post-burn fluid resuscitation with Ringer's lactate, six burn patients (% total body surface area burn 30-57%) were given primed, continuous infusions of inulin and p-aminohippuric acid for 6 hours. Albumin (25% solution, 3 mL/kg/h) was given for the final 4 hours of study.

MEASUREMENTS AND MAIN RESULTS

Albumin infusion increased plasma volume by 37%; however, glomerular filtration rate decreased by 32% (p < 0.05). There was no significant change in urine output, sodium excretion, or effective renal plasma flow. Plasma volume expansion with albumin normalized elevated basal levels of aldosterone and plasma renin activity.

CONCLUSIONS

These findings illustrate that despite substantially increasing plasma volume, colloid infusions reduce glomerular filtration and may limit any associated diuresis. Furthermore, this study demonstrates that hormonal regulation of blood volume remains intact after moderate burn injury.