Optimal solder and power density for diode laser tissue soldering (LTS).

BACKGROUND AND OBJECTIVE: Laser tissue soldering (LTS) using albumin and indocyanine green dye (ICG) is an effective technique utilized in various reconstructive surgical procedures. The purpose of this study was to describe in vivo and in vitro temperature profiles of an albumin-based solder while varying ICG concentration and laser power density (PD), and to describe immediate and short-term tensile strength measurements and histology of tissue with variable ICG concentrations and PD. STUDY DESIGN/MATERIALS AND METHODS: ICG ranged from 0.31 to 20 mg/mL while PD ranged from 3.2 to 63.7 W/cm(2). Direct solder temperature measurements were obtained at 5-second intervals during laser activation. Differential temperature measurements were determined within the dermis of rat skin and the overlying solder. Eighteen rats were subjected to 2.0-cm incisions (n = 113) created on the dorsal skin followed by closure with LTS at varying PD and ICG concentrations. ICG concentrations included 0.31, 2.5, and 20 mg/mL, while PD ranged from 8.0 to 63.7 W/cm(2). Tensile strength (TS) profiles were measured immediately and 10 days post-operatively. Histological examination was performed at the time of sacrifice. RESULTS: Temperature profiles of the ICG/albumin solder differed significantly only at the highest concentration of ICG (20 mg/mL), but showed statistically significant variability at different laser PD. Using solder color changes as an endpoint of LTS, average peak solder temperature ranged from 69 degrees C at a PD of 8.0 W/cm(2), 105 degrees -120 degrees C at PD 15.9-31.8 W/cm(2), and > 200 degrees C at PD > or = 47.7 W/cm(2). Peak intradermal temperatures remained below 50 degrees C at all PDs. Varying ICG concentration only had an effect on the immediate TS of wounds at the lowest power densities. Increasing PD resulted in statistically significant increases in immediate TS up to a PD of 23.9 W/cm(2) at an ICG concentrations of 0.31 and up to a PD of 15.9 W/cm(2) at a concentration of 2.5 mg/mL. Statistically insignificant decreases in 10-day would strength resulted from higher PD. Power densities > or = 23.9 W/cm(2) showed significant thermal injury upon histologic examination. CONCLUSIONS: Power density, not ICG concentration, is the primary determinant of solder and tissue temperature during LTS. Effective and reproducible laser tissue soldering may be achieved primarily by power density control when using diode laser and ICG-based albumin solder. Alterations in PD show the most direct and predictable effects on the healing properties of skin closed by LTS. Optimal laser wound closure occurs with an ICG of 2.5 mg/mL and at a PD between 15.9 and 23.9 W/cm(2).

Pulmonary hypertension in children following extracorporeal membrane oxygenation therapy and repair of congenital diaphragmatic hernia.

OBJECTIVE: Pulmonary hypertension (PHT) is present in all children at birth, but its degree and rate of resolution in infants diagnosed with congenital diaphragmatic hernia (CDH) requiring extracorporeal membrane oxygenation (ECMO) need to be established. STUDY DESIGN: Twenty-one ECMO/CDH survivors (aged 3.2 +/- 1.4 years) were prospectively evaluated by Doppler echocardiography (ECHO) to determine the presence of PHT. Twenty children without structural heart disease were used as controls. Study patients received a physical examination and an electrocardiograph examination, and their charts were reviewed for neonatal course data. Patients found to have PHT by ECHO received a complete history and exercise treadmill/oxygen desaturation study. RESULTS: Eight of the 21 patients (38%) met echocardiographic criteria for PHT. No neonatal course data were found to be predictive of eventual PHT status. There was no correlation between physical examination or electrocardiographic findings and PHT. Complete histories showed five of the eight patients with PHT had some degree of exercise intolerance and seven had wheezing. Two of the seven patients studied on the treadmill desaturated 5% or greater from baseline. CONCLUSION: There is evidence that PHT either persists or recurs in a significant portion of the ECMO/CDH population and may remain symptomatic well beyond the neonatal period.

Comparison of dermal and epithelial approaches to laser tissue soldering for skin flap closure.

BACKGROUND AND OBJECTIVE: Prior studies of laser tissue soldering (LTS) of epithelial skin have shown poor wound strength in the short-term; however, we hypothesize that greater tensile strength and healing properties will result from directing laser energy to the dermal aspect of the skin. The current study compares wound strength and histology in a rat skin flap model of epithelial and dermally applied LTS. STUDY DESIGN/MATERIALS AND METHODS: Skin flaps (2.5 x 4 cm) were raised and bisected on the dorsum of Sprague-Dawley rats. The center line of bisection was closed from a dermal approach by LTS (LTS-D, diode laser 15.9 W/cm2 + Columbia solder), the upper incision by epithelial LTS (LTS-E), and the lower incision by suturing (7-0 Vicryl). Wound skin strips (1-2 mm x 10 mm) were studied immediately (N = 14) and at 3 (N = 57), 7 (N = 31), and 10 (N = 28) days postoperatively and were subjected to tensiometric analysis. Histologic staining with hematoxylin and eosin and Mallory's trichrome methods were used to define wound architecture. RESULTS: No wound dehiscences were noted in any group. Greater immediate tensile strength was noted in wounds closed by LTS-D (521 +/- 61 g/cm2) versus LTS-E (342 +/- 65 g/cm2); however, this difference was not statistically significant (P = .08). By 3 days, both LTS-D (476 +/- 55 g/cm2) and LTS-E (205 +/- 37 g/cm2) maintained their initial strength; however, LTS-D and sutured (436 +/- 49 g/cm2) wounds were stronger (P < .05) than LTS-E. At 7 and 10 days, LTS-D (2,433 +/- 346 g/cm2 and 3,100 +/- 390 g/cm2) showed superior tensile strength (P < .05) compared to both LTS-E (1,542 +/- 128 g/cm2 and 2,081 +/- 219 g/cm2) and suturing (1,342 +/- 119 g/cm2 and 1,661 +/- 115 g/cm2). Histologic analysis of LTS-D wounds at 3 days showed full-thickness tissue apposition, complete epithelialization, and minimal inflammation or thermal injury. At 7 days, solder was present in the wounds. In contrast, LTS-E wounds at 3 days displayed lack of epithelialization secondary to thermal injury and partial-thickness tissue apposition. However by 7 days, epithelialization was complete with moderate scarring, and no solder was seen. Sutured samples appeared similar to LTS-D, except for poorer tissue apposition at the hypodermis. CONCLUSION: Our results show that skin flap wound healing after dermal LTS is superior to epithelial LTS and emphasizes the importance of site specificity in the utilization of this operative technique in reconstructive surgery.

Survivors of extracorporeal membrane oxygenation at 1 year of age: the relationship of primary diagnosis with health and neurodevelopmental sequelae.

OBJECTIVE: Although extracorporeal membrane oxygenation (ECMO) has been responsible for the improved survival of infants with cardiorespiratory failure, its use over the last decade has raised concern as to the health of the survivors and the severity of neurodevelopmental sequelae. Though infants meeting ECMO criteria have a variety of reasons prompting the use of this therapy, most studies to date have simply reported outcome on the entire population that has survived without regard to the original nature of the child's illness. The purpose of this study was to determine the type and extent of health-related problems and neurodevelopmental sequelae in infants requiring ECMO therapy and the association of these findings with the infants' primary diagnosis. METHODS: Eighty-two neonates required ECMO therapy between May 1990 and December 1993. The most common diagnosis prompting ECMO therapy included 26% with meconium aspiration syndrome, 34% with congenital diaphragmatic hernia (CDH), 16% with persistence of the fetal circulation, and 9% with sepsis. Information concerning the hospital course was obtained through chart review, and the infants were seen at 6 and 12 months of age for medical and neurodevelopmental follow-up. Data were analyzed using descriptive statistics and Fisher's exact test, t-tests, and analysis of variance where appropriate. Assessment of hospital course and discharge data focused on the four main diagnostic groups, whereas follow-up data were further limited to the two most frequently encountered groups (meconium aspiration syndrome and CDH). RESULTS: Overall survival was 79%. Significant differences in survival were noted based on primary diagnostic category. Those with CDH fared the worst, with an overall survival rate of 68% and a more complicated hospital course with a longer duration of ECMO. At discharge, the CDH group demonstrated a greater incidence of bronchopulmonary dysplasia, gastroesophageal reflux, feeding dysfunction, and hypotonia. No significant differences were noted in the incidence of intraventricular hemorrhage, cerebral infarction, extra-axial fluid collection, or seizures. Hearing loss was uncommon. During the first year of life, although no differences were noted in growth rate, infants in the CDH group continued to experience a higher incidence of gastroesophageal reflux (43%) and feeding dysfunction, with 36% of this group requiring tube feedings for nourishment. Although 40% of the entire ECMO population was diagnosed with bronchopulmonary dysplasia before initial discharge, by 1 year of age, 50% of those with CDH versus 17% of those with meconium aspiration syndrome continued to be clinically symptomatic. Although the ECMO population as a whole scored in the normal range developmentally, CDH infants had significantly lower motor and slightly lower cognitive scores at 1 year of age. Despite finding abnormal muscle tone in a high percentage of the entire ECMO population at discharge, most demonstrated resolution by 1 year of age. Of the CDH infants, however, 75% continued to evidence some degree of hypotonicity, which affected acquisition and quality of gross motor skills. CONCLUSION: Despite the impact that ECMO has had on the survival of infants with severe respiratory failure, the efficacy of ECMO cannot be assessed accurately without an analysis of the extent and morbidity in the surviving population. Most centers are reporting relatively low morbidity for the entire ECMO population. However, upon separating this population into primary diagnostic categories, we found that the CDH population encountered a greater number of neurodevelopmental, respiratory, and feeding abnormalities during the first year of life. The reasons for these differences are unclear but may be related to the severity of the primary illness itself or the variables associated with prolonged ECMO therapy. Stratifying outcome by primary diagnosis gives the health care provider more information to improve

Outcome for infants with congenital diaphragmatic hernia requiring extracorporeal membrane oxygenation: the first year.

Congenital diaphragmatic hernia (CDH) has been associated with a high mortality rate. The purposes of this study were to determine the impact of extracorporeal membrane oxygenation (ECMO) on the survival of infants with CDH and to document the sequelae and 1-year neurodevelopmental outcome for CDH infants who required ECMO. Thirty neonates with CDH were admitted between May 7, 1990 and October 1, 1992. Twenty required ECMO and were enrolled in our neonatal follow-up program. Information about the infants' neonatal course was obtained from chart review, and the infants were seen at 3, 6, and 12 months of age for medical and neurodevelopmental follow-up. Primary diaphragmatic repair was performed in 13 infants. Five required Goretex graft reconstruction (GGR), and two did not have repair. Sixteen (80%) of the 20 infants who required ECMO survived. The overall survival rate increased from 31% (10 of 32) in the 5 years previous to the start of the ECMO program to 63% (19 of 30) since then (P = .01). The most common sequelae noted by the time of discharge included gastroesophageal reflux (GER; 81%), the need for tube feeding (69%), and chronic lung disease (CLD; 62%). At 1 year of age, mean cognitive skills were average (87 +/- 23) and motor skills were borderline (75 +/- 24) according to the Bayley Scales of Infant Development. Hypotonia was present in 10 of 13 patients.(ABSTRACT TRUNCATED AT 250 WORDS)