The use of vacuum-assisted closure therapy for the treatment of lower-extremity wounds with exposed bone

Lower-extremity wounds with exposed tendon, bone, or orthopedic hardware present a difficult treatment challenge. In this series of patients, subatmospheric pressure therapy was applied to such lower-extremity wounds. Seventy-five patients with lower-extremity wounds, most of which were the result of trauma, were selected for this study. Dressings made of sterile open-cell foam with embedded fenestrated tubing were contoured to the wound size and placed into the wound. The site was covered with an adhesive plastic sheet. The sheet was placed beneath any external fixation devices, or the fixation device was enclosed within the sheet. The tubing was connected to the vacuum-assisted closure pump. Continuous subatmospheric suction pressure (125 mmHg) was applied to the wound site. The wounds were inspected and the dressings were changed every 48 hours.Vacuum-assisted closure therapy greatly reduced the amount of tissue edema, diminishing the circumference of the extremity and thus decreasing the surface area of the wound. Profuse granulation tissue formed rapidly, covering bone and hardware. The wounds were closed primarily and covered with split-thickness skin grafts, or a regional flap was rotated into the granulating bed to fill the defect. Successful coverage was obtained without complication in 71 of 75 patients. Wounds have been stable from 6 months up to 6 years.

Use of specialized bone screws for intermaxillary fixation

Fixation of the injured mandible to the maxilla is a proven method of stabilizing mandibular fractures and ensuring proper occlusion. The authors report their results with new specialized intraoral bone screws (IMF Screw System; Howmedica Leibinger, Inc., Carrollton, TX) that are designed for the purpose of achieving intermaxillary fixation (IMF). Nineteen patients were placed into rigid IMF using IMF screws alone. Indications were nondisplaced mandibular fractures; symphyseal, body, and angle fractures; midfacial fractures requiring temporary IMF; and edentulous patients with any of these fracture types and an adequate prosthesis. All procedures were performed with the patient under general anesthesia. The authors found that the operative time was markedly shorter than with standard IMF techniques, patient satisfaction was high, and there were no infections related to the screws. All 19 patients remained in stable, accurate occlusion and had adequate healing. One patient continues to have paraesthesias in the mental nerve distribution after screw removal. Although there is the potential for tooth and nerve injury when screws are placed improperly, the IMF Screw System seems to be a safe and reliable method of achieving secure mandibular fixation.

Single-stage approach to skin grafting the exposed skull

Four patients are presented who suffered full-thickness loss of the scalp, exposing the skull. Removal of the outer table, immediate application of a split-thickness skin graft, and treatment with the VAC for 3 to 4 days resulted in approximately 100 percent graft take in each case without complications. When compared with the usual two-stage approach to skin grafting the exposed skull, this method spares the patient a longer hospital stay and a second operative procedure, and it results in a significant cost savings.

A prefabricated free flap for eyelid reconstruction

Patients with severe soft-tissue trauma to the ipsilateral upper and lower eyelid and surrounding structures represent a reconstructive challenge. The authors present a new approach to eyelid reconstruction, by creating a prefabricated free flap from the contralateral lower eyelid. New Zealand white rabbits were anesthetized, and the central artery and vein of the ear were mobilized and placed in a subcutaneous tunnel in the lower eyelid. After a delay procedure, flaps were made that measured 50 percent of the lower lid area. In an initial group (n = 9), the flaps were harvested at 3 weeks, and injected with Microfil, to demonstrate visual and radiologic patency and perfusion from the neopedicle. In a subsequent group of animals (n = 6), full-thickness defects of 50 percent of the left upper lid were created. Prefabricated free flaps from the right lower lid were transferred, anastomosing to the central artery and vein on the side of the eyelid being reconstructed. Tissue removed from the upper eyelid was placed in the defect of the lower lid donor site to serve as a control. Flaps were followed for periods of up to 6 months, documenting results photographically and by injection. Prefabricated free flaps from the lower eyelid maintained long-term patency and full-thickness perfusion from the pedicle, and also maintained size, shape, and accessory skin appendages better than composite graft controls. The authors concluded that prefabricated free flaps may be used to reconstruct eyelid defects; a surgical technique for application to human subjects is proposed.

Synthesis and degradation of collagens in skin of healthy and protein-malnourished rats in vivo, studied by 18O2 labelling

To explore the effects of growth retardation, caused by restricted protein intake, on collagen turnover in the whole skin, Sprague-Dawley rats (n = 20) were labelled with 18O2 and fed on either an adequate (18%) or a low (3%) lactalbumin diet. Skin biopsies were obtained at intervals during the following 6 months. Independent groups of animals (n = 186) were used to determine the size of the 0.5 M-acetic acid-soluble and -insoluble collagen pools in the entire skin of healthy and malnourished rats. Collagen was estimated by measurement of hydroxyproline. Soluble-collagen synthesis rates were equivalent to 99 +/- 8 mumol of hydroxyproline/day in healthy animals and 11 +/- 2 mumol/day in malnourished rats. Insoluble-collagen synthesis rates were 32 and 5 mumol of hydroxyproline/day in the healthy and protein-depleted rats respectively. The degradation of soluble collagen amounted to 37 +/- 8 and 6 +/- 2 mumol of hydroxyproline/day in the healthy and malnourished groups respectively. Efflux of collagen from the soluble collagen, defined as the sum of the rate of soluble collagen that is degraded plus that which matures into insoluble collagen, was 70 +/- 8 and 11 +/- 2 mumol of hydroxyproline/day in the healthy and malnourished groups respectively. Insoluble collagen was not degraded in either group. The fraction of soluble collagen leaving the pool that was converted into insoluble collagen was 0.46 in both diet groups. It is concluded that the turnover of soluble collagen is markedly decreased with malnutrition, but degradation and conversion into insoluble collagen account for the same proportions of efflux from the soluble-collagen pool as in rapidly growing rats.

Synthesis and degradation rates of collagens in vivo in whole skin of rats, studied with 1802 labelling

Rats of synthesis and degradation in vivo of collagens in 0.5 M-acetic acid-soluble and -insoluble extracts from skins of three growing rats were determined by using a labelling procedure involving exposure of the animals to an atmosphere of 18O2 for 36 h. For comparison, rats also received injections of [2H]proline. Serial skin biopsies were taken at frequent intervals over 392 days. Enrichment of 18O and 2H in the hydroxyproline of the collagen fractions was determined by gas chromatography-mass spectrometry. Changes in size of the soluble and insoluble collagen pools were considered in the evaluation of isotope kinetic data. The insoluble collagen fraction showed no degradation. The efflux (mean +/- S.D., expressed as mumol of hydroxyproline) from the soluble collagen pool was estimated to be 59.9 +/- 1.9 per day from the 18O data, and 25.5 +/- 7.5 per day from the 2H results. The finding indicates significant reutilization of 2H-radiolabelled proline for hydroxyproline synthesis. From these isotope data and estimates of size of the collagen pools it was determined that 55% of the collagen disappearing from the soluble pool was due to maturation into insoluble collagens and 45% of the disappearance was a result of actual degradation of soluble collagen. These results confirm the utility of 18O2 as a non-reutilizable label for studies of collagen turnover in vivo.

Adequacy of a modular tube feeding diet for burned patients

Recent research on nutrition needs following thermal injury suggests that carbohydrate and caloric excess must be avoided while an attempt is made to meet relatively large protein requirements. The nutrition regimen in this investigation for adult and pediatric burned patients provides calories at twice the predicted basal metabolic rate, protein at 2.5 gm/kg/day, and carbohydrate at 5 mg/kg/minute. Lipids are provided to meet the caloric deficit after protein and carbohydrate administration. Even though such nutrients are readily provided parenterally, the high carbohydrate content of standard tube feedings makes it difficult to provide adequate protein without excess of carbohydrate and calories. As a result, a modular tube feeding, containing appropriate macro- and micronutrients and tailored to the individual patient, has been used in our burn units. The adequacy of the diet was assessed by the effect on nitrogen balance, weight change, selected serum indexes of visceral metabolism, and compliance with planned dietary goals. Patients remained in positive nitrogen balance more than 80% of the time while the modular diet was used in conjunction with other modes of therapy (parenteral and/or oral). More than 90% of the time, positive balance was achieved when the modular diet was used as the sole source of nutrition. Compliance with the caloric goal and physicians' diet orders for the modular diet exceeded, on average, the 80% level, which has previously been the established lower limit. The results in this study suggest that the modular diet is an appropriate method of nutrition support.

Closed-circuit metabolic system with multiple applications

A closed-circuit metabolic system has been designed and tested for multiple applications. Air pressure within a closed chamber is regulated electronically while allowing for respiratory gas exchange. Compared with a previously reported standard indirect calorimetry system, the new device had by virtue of longer duration of measurement improved precision (coefficient of variation 3% vs. 14%) during studies of O2 consumption both at room temperature and at 5 degrees C. In addition, a more physiological atmospheric environment is maintained. This system has also been utilized for simultaneously labeling groups of up to 20 weanling rats with 18O2 over a 2-day period and for exposure of rats to a hyperoxic (84% O2), normobaric environment for 4-day periods. Potential applications include maintenance of pressure (hypobaric through hyperbaric) and O2 (hypoxic through hyperoxic) controlled environments, exposure to toxic gases, study of diurnal variations in metabolic rate, measurement of metabolic expenditure with activity, and adaptation to other species including humans.

In vivo total body electrical conductivity following perturbations of body fluid compartments in rats

Total body electrical conductivity (TOBEC) provides a rapid and safe noninvasive technique for the assessment of total body water in animals and man. An instrument employing this principle has been shown to measure body water in healthy Sprague-Dawley rats. With the exception of adult obesity in humans, alterations in body fluid compartments that could theoretically affect the utility of conductivity measurements have not been studied. We, therefore, applied the total body electrical conductivity measurement in rats following perturbations of body fluid/electrolyte spaces including obesity, furosemide diuresis, severe burn, and low protein diet. Our findings confirm that total body water can be accurately measured by TOBEC in conditions of abnormal body fluid distribution. However, when the ratio of intracellular to extracellular fluid is significantly reduced, such as the severe burn or low protein intake, TOBEC does not reflect the intracellular (potassium) space but does predict total water and extracellular (sodium) space.

Weight maintenance in pediatric burned patients

Weight change, defined as the difference between the preadmission and discharge weights, has often been used as an indicator of the adequacy of nutrition support. Weight change has been found to be uninterpretable in burned patients because excision and grafting contribute to weight loss but do not reflect systemic physiology. Also, normal growth during hospitalization contributes to weight gain but is not included in traditional methods of assessing weight change of children. We examined weight change corrected for escharectomies and growth in 42 adult and pediatric burned patients. Thirty-five of the patients had weight loss within 10% of their premorbid weight. Moreover, weight loss was correlated with three observable patient characteristics: age, percent initial burn size, and preburn weight. It was concluded that the dietary regimen of providing twice the predicted basal metabolic rate in terms of calories, based on ideal body weight, was adequate to prevent significant weight loss in most patients but that further refinement is necessary to improve individual reliability. Furthermore, significant weight losses may not affect morbidity/mortality as previously thought.

Prediction of total urinary nitrogen from urea nitrogen for burned patients

Although many of the current nutrition assessment techniques are inappropriate for burned patients, we have found nitrogen balance to be a helpful measure of the effectiveness of nutrition therapy if it is used in conjunction with other measures of nutritional status. Many clinicians suggest that a 24-hour urinary urea nitrogen (UUN) measurement, in addition to a correction term of 2 to 4 gm nitrogen, will accurately represent all nitrogen losses (urinary non-urea nitrogen, fecal, integumental). However, since no burned patients were used in the development of that method, its use may not be appropriate for burned patients. As an alternative to total urinary nitrogen (TUN), which is costly and time consuming, we have developed a simple way to predict TUN from UUN, percent initial total body surface area burn, and age for pediatric and adult burned patients. We propose that nitrogen balance may then be determined from the predicted TUN by an equation showing that nitrogen balance equals daily nitrogen intake minus predicted TUN plus fecal and normal nitrogen loss.

Dietary compliance for pediatric burned patients

Physician diet orders written for pediatric burned patients frequently differ from the diets patients actually receive. At Shriners Burns Institute in Boston, such deviations from the diet order were generally not recognized for at least two days. In order to increase compliance with physician diet orders, changes in the nutritional support program were implemented which included physician diet orders containing specific macronutrient requirements in addition to the caloric goal, which was changed in response to recent research demonstrating that the previously used formula provided excessive calories; introduction of modular diets for parenteral and enteral feedings; institution of daily nutrition flow sheets; and a change of the time at which daily caloric intake records were calculated. In order to assess the benefits of the new measures, the average deviation from the caloric goal was calculated for patients who did not receive the new assessment tools (control group, N = 51), compared with those who did (study group, N = 50). Least squares regression analysis indicated a trend toward improved compliance and less deviation from the calculated caloric goal following implementation of the four measures.

Urea, glucose and alanine kinetics in man: effects of glucose infusion

1. The simultaneous effects of an intravenous glucose infusion on plasma urea, glucose and alanine kinetics were investigated in normal post-absorptive man. 2. The primed constant intravenous infusion of compounds labelled with stable isotopes, [15N2]urea, [6-2H]glucose and [3-13C]alanine, was used. 3. The rate of appearance of glucose and urea in the plasma was rapidly reduced by the 17.7 mumol min-1 kg-1 glucose infusion. 4. In contrast, during the glucose infusion there was an increased rate of appearance of alanine in the plasma, and an increased percentage of glucose carbon atoms derived from alanine. 5. Reduced production of glucose and urea during the glucose infusion was not due to decreased gluconeogenesis from alanine.