Local identifiability and sensitivity analysis of neuromuscular blockade and depth of hypnosis models.

This paper addresses the local identifiability and sensitivity properties of two classes of Wiener models for the neuromuscular blockade and depth of hypnosis, when drug dose profiles like the ones commonly administered in the clinical practice are used as model inputs. The local parameter identifiability was assessed based on the singular value decomposition of the normalized sensitivity matrix. For the given input signal excitation, the results show an over-parameterization of the standard pharmacokinetic/pharmacodynamic models. The same identifiability assessment was performed on recently proposed minimally parameterized parsimonious models for both the neuromuscular blockade and the depth of hypnosis. The results show that the majority of the model parameters are identifiable from the available input-output data. This indicates that any identification strategy based on the minimally parameterized parsimonious Wiener models for the neuromuscular blockade and for the depth of hypnosis is likely to be more successful than if standard models are used.

Impairment after burns: a two-center, prospective report.

Impairment rating is regularly reported for trauma and other conditions but rarely for burns. The purposes of this study were: (1) to report impairment collected prospectively at our burn center, (2) to relate this impairment to measures of psychosocial and functional outcome, and (3) to compare these data to similar data from another burn center to verify that rating impairment is standardized and that the impairments are similar. We studied 139 patients from the University of Washington (UW) Burn Center and 100 patients from the University of Texas (UT) Southwestern Burn Center. The average whole person impairment (WPI) ratings at the University of Washington were 17% and this correlated with total body surface area burned and days off work. It did not correlate with Brief Symptom Inventory (BSI), Functional Independence Measure (FIM), Short-Form 36-Item Health Survey (SF-36), Satisfaction With Life Scale (SWLS), and the Community Integration Questionnaire (CIQ). Average whole person impairment ratings at UT Southwestern were similar at 19%. Several components of the impairment rating, however, differed at the two institutions. To minimize this variation, we recommend: (1) use the skin impairment definitions of the fifth edition of the Guides to the Evaluation of Permanent Impairment (or the most recent published versions of the Guide), and (2) include sensory impairment in healed burns and skin grafts in the skin impairment.

Prospective trial of thick vs standard split-thickness skin grafts in burns of the hand.

For best function and appearance, thick skin grafts for hands are generally preferred to thinner grafts. But how thick is thick enough? This prospective randomized trial was designed to compare 0.015-inch skin grafts for burned hands to hand grafts that are 0.025 inches thick. Consecutive patients receiving skin grafts to hands were randomized to have sheet grafts using donor sites of 0.015-inch or 0.025-inch thickness. To prevent delayed healing and potential hypertrophic scarring, the thick graft donor sites were grafted with 0.008-inch grafts. There were no significant differences in range of motion, final appearance, or patient satisfaction between the two groups at 1 year. There were problems with donor site healing in both groups. We recommend that hand grafts for adults be at least 0.015 inches thick but do not see an advantage to the use of very thick (0.025-inch) grafts, even with thin split-thickness skin grafts to the donor site.

Dexter: a tool to facilitate impairment ratings.

Calculating impairment in burn patients is crucial to understanding outcome. However, it is rarely reported after burns, presumably because the process of calculating impairment ratings is complicated and tedious. Computerized systems have been developed that facilitate the process, but it has not been established in burn patients that these systems reduce the time required to calculate impairment. We evaluated the Dexter Evaluation and Therapy System by Cedaron Medical Inc (Davis, CA). A sample of 10 manually recorded ratings was compared with 10 performed on the Dexter. Mean time for the manual technique was 65 +/- 35 minutes versus 37 +/- 13 minutes for the Dexter (P < .05, Mann-Whitney). The time taken to perform impairment ratings in burn survivors is significantly reduced by the use of the Dexter system. Time saving occurs primarily at three points: (1) electronic data entry directly from the measuring instruments, (2) compilation of data, and (3) rapid generation of reports.

Incidence of the concrete scalp deformity associated with deep scalp donor sites and management with the Unna cap.

The scalp has become a popular donor site for split-thickness skin grafts. This donor site does, however, have complications, including the concrete scalp deformity, which consists of hairs embedded in a thick, desiccated, exudative crust. This article presents our burn unit's experience with this complication. Fifty-six patients underwent scalp skin graft harvesting between 1984 and 1996. All grafts were quite thick and were used for resurfacing facial burns. Thirty-eight donor sites were treated with medicated gauze, and 18 were treated with the Unna cap, which is an Unna dressing applied over Aquaphor gauze (Beiersdorf, Norwalk, Conn). Eighteen of the 38 patients (32%) treated with medicated gauze developed the concrete scalp deformity. None of the patients treated with the Unna cap developed the deformity. Although useful, the deep scalp donor site has complications, including the concrete scalp deformity. However, with use of the Unna cap dressing, we have had no occurrences of this problem.

The Unna "cap" as a scalp donor site dressing.

Deep scalp donor sites can be difficult to manage because of the higher incidence of healing complications that can make daily wound care exquisitely painful. When faced with this problem, we prospectively studied the Unna "cap" dressing on the scalp. Group 1 received our standard treatment--Xeroform gauze (Sherwood Medical, St Louis, Mo) and daily wound care. Group 2 received the Unna cap--Aquaphor gauze (Beiersdorf, Norwalk, Conn) and Dome Paste gauze (Bayer Corp, West Haven, Conn) with wound care every 3 days. Pain, healing time, and costs were compared. Twelve patients between the age of 1 and 54 years were studied. A significant number of patients in Group 1 developed wound complications after initial healing, resulting in a longer length of stay and higher costs. Group 2 reported significantly less procedural pain, comparable healing (11 days +/- 2 SD), and fewer dressing changes, resulting in an institutional savings of $5.51 to $16.25 per patient up to postoperative day 13. This study supports use of the Unna cap as a less painful, safe, and cost-effective alternative to our standard deep scalp donor site dressing.

Silipos neck wraps.

Burns of the neck are a problem. Grafted anterior necks can result in disfiguring hypertrophic scar contractures and wrinkling of the graft. The development of contractures can be prevented by effective splinting as soon as possible after the burn and by following a continuous wearing schedule until scar maturation is complete. Traditional neck conformers do not allow free neck rotation and can lead to stiffness as a result of decreased mobility. We used Silipos neck wraps for 10 patients who had good range of motion in the neck and who required pressure only for flattening of grafts and wrinkle prevention. The neck wrap is user-friendly, low in cost, and easy to fabricate and custom-fit for individual patients.

Value of the head-at-risk concept in assessing the prognosis in Legg-Calvé-Perthes disease.

Seventy-five hips affected by Legg-Calvé-Perthes disease were reviewed. Three therapeutic groups were defined: conservative treatment, marrow emptying of the femoral neck, and varus derotation femoral osteotomy. Results were analyzed according to head-at-risk concept. Patients with head not at risk had better results regardless of treatment. Results in other groups were worse, but improved significantly with varus derotation femoral osteotomy. In children greater than 9 years of age, the results were almost invariably poor, irrespective of head-at-risk designation.