Nicole P. Bernal

Cerebral and somatic near-infrared spectroscopy in normal newborns

PURPOSE Near-infrared spectroscopy has been used increasingly in the pediatric population as a continuous, noninvasive indicator of trends in organ perfusion and oxygenation. We studied healthy newborn babies to establish normal values during rest and feeding. METHODS Forty-four term newborns were recruited. Near-infrared spectroscopy probes were placed on the forehead and over the right kidney to record cerebral (rSO(2)C) and renal-somatic (rSO(2)R) regional oxyhemoglobin saturation. Readings were collected continuously for 2 to 8 hours, spanning 1 to 3 feeding episodes. RESULTS Data were available on 26 patients, with an average age of 44 +/- 28 hours. The overall average rSO(2)C was 77.9% +/- 8.5%, rSO(2)R was 86.8% +/- 8.1%, and DeltarSO(2)RC (somatic-cerebral rSO(2) difference) was 8.9% +/- 9.4%. During feeding, rSO(2)C was minimally decreased (78.6% +/- 8.4% versus 78.0% +/- 9.0%, P = .023), rSO(2)R did not change (87.0% +/- 8.1% versus 87.3% +/- 8.0%, P = .31), and DeltarSO(2)RC was minimally increased (8.5% +/- 9.5% versus 9.2% +/- 9.1%, P = .014). Over the first 120 hours after birth, average rSO(2)C decreased (P < .01), and rSO(2)R remained relatively unchanged. CONCLUSIONS Clinical utility of near-infrared spectroscopy was partly limited by lack of normative data. These data demonstrate that regional oxygen extraction is greater across cerebral than across renal-somatic beds in normal newborns. Healthy newborns do not have clinically significant changes in organ oxygenation with feeding.

Spatial frequency domain imaging of burn wounds in a preclinical model of graded burn severity

Abstract. Frequent monitoring of early-stage burns is necessary for deciding optimal treatment and management. Both superficial and full thickness burns are relatively easy to diagnose based on clinical observation. In between these two extremes are superficial-partial thickness and deep-partial thickness burns. These burns, while visually similar, differ dramatically in terms of clinical treatment and are known to progress in severity over time. The objective of this study was to determine the potential of spatial frequency domain imaging (SFDI) for noninvasively mapping quantitative changes in chromophore and optical properties that may be an indicative of burn wound severity. A controlled protocol of graded burn severity was developed and applied to 17 rats. SFDI data was acquired at multiple near-infrared wavelengths over a course of 3 h. Burn severity was verified using hematoxylin and eosin histology. From this study, we found that changes in water concentration (edema), deoxygenated hemoglobin concentration, and optical scattering (tissue denaturation) to be statistically significant at differentiating superficial partial-thickness burns from deep-partial thickness burns.

Trends in 393 necrotizing acute soft tissue infection patients 2000–2008 ☆

OBJECTIVE To determine the outcomes effect of changing trends in patients with necrotizing acute soft tissue infections (NASTI) 2000-2008. METHODS A single institution retrospective chart review of all patients treated for NASTI. RESULTS There were 393 patients with mean age 50 years, diabetes 53%, % body surface area excised 3.5. Wounds were located on: extremity 57%, perineum 40%, trunk 26%. Wound cultures %: polymicrobial=62, Staphylococci=48, Streptococci=31. Patients developing complications %: Pulmonary=23, renal insufficiency/failure=27. During the study period, overall mortality rate remained unchanged: 30/393=7.6% (5.5% for patients first admitted by burn/trauma/acute care surgery vs. 29% for all other services, p=0.003). Significant annual increases were found in number of patients, p=0.03, male sex, p=0.000, transfer from outside hospital, p<0.001, BMI p=0.003, ventilator requirement >24h, p=0.0005, APACHE II p=0.002, and number of patients developing any complication, p=0.04. Statistically significant decreases annually were found in: days of antibiotic use, p=0.008, number of operations required for excision, p=0.02, development of non-wound infections, p=0.002, and length of stay in days (LOS), p=0.03. CONCLUSIONS This is the largest cohort of NASTI patients from a single institution to date, demonstrating significantly shorter LOS and decreased non-wound infection rates in the face of increasing BMI and APACHE II scores. The increasing number of patients and BMI suggests a causal relationship between NASTI and obesity. Initial care by surgeons experienced in caring for these patients provides mortality rates well below the national average.

Quantitative long-term measurements of burns in a rat model using Spatial Frequency Domain Imaging (SFDI) and Laser Speckle Imaging (LSI): MEASUREMENTS OF BURNS IN A RAT MODEL

The current standard for diagnosis of burn severity and subsequent wound healing is through clinical examination, which is highly subjective. Several new technologies are shifting focus to burn care in an attempt to help quantify not only burn depth but also the progress of healing. While accurate early assessment of partial thickness burns is critical for dictating the course of treatment, the ability to quantitatively monitor wound status over time is critical for understanding treatment efficacy. SFDI and LSI are both non‐invasive imaging modalities that have been shown to have great diagnostic value for burn severity, but have yet to be tested over the course of wound healing.

Acute discrimination between superficial-partial and deep-partial thickness burns in a preclinical model with laser speckle imaging

A critical need exists for a robust method that enables early discrimination between superficial-partial and deep-partial thickness burn wounds. In this study, we report on the use of laser speckle imaging (LSI), a simple, non-invasive, optical imaging modality, to measure acute blood flow dynamics in a preclinical burn model. We used a heated brass comb to induce burns of varying severity to nine rats and collected raw speckle reflectance images over the course of three hours after burn. We induced a total of 12 superficial-partial and 18 deep-partial thickness burn wounds. At 3h after burn we observed a 28% and 44% decrease in measured blood flow for superficial-partial and deep-partial thickness burns, respectively, and that these reductions were significantly different (p=0.00007). This preliminary data suggests the potential role of LSI in the clinical management of burn wounds.

Quantitative longitudinal measurement in a rat model of controlled burn severity using spatial frequency domain imaging

Background and Objective: Spatial Frequency Domain Imaging (SFDI) is a non-contact wide-field optical imaging technology currently being developed to investigate the feasibility of quantitative non-invasive evaluation of burn wound severity in a rat model. Our objective is to determine the potential of SFDI for mapping quantitative changes in spatially resolved tissue oxygen saturation and water concentration may be indicative of burn wound severity, healing, and further complications. In this portion of the investigation, we focus on the development of a rat burn model and the acute response of tissue to burn wounds. Study Design/Materials and Methods: A controlled burn protocol involving a heated brass comb was applied to 6 rats. Imaging was acquired at 17 evenly spaced wavelengths in the near-infrared from 650 to 970 nm. Over the course of the 3 hour post-burn period, we were able to map quantitative changes in spatially resolved chromophores. Burn severities were verified post-experiment using standard H and E histology and optical microscopy. Results/Conclusion: In total, we were able to induce 12 superficial-partial thickness burns, 8 deep-partial thickness burns, and 4 full thickness burns in our rat models. While several tissue chromophores were tracked, we found that changes in oxygen saturation and water concentration to be sensitive indicators of burn severity. Future work will include additional longitudinal studies over a period of days in order to investigate which parameters are correlated to tissue healing.

Accurate Measurement of Intraoperative Blood Loss during Wound Excision Leads to More Appropriate Transfusion and Reduced Blood Utilization

Objective: To determine if accurate measurement of surgical blood loss using a novel device that photographs surgical sponges and calculates their hemoglobin content affects transfusion practice. Methods: We retrospectively compared transfusion events for patients having wound excisions using visual estimation of blood loss (traditional group; n=178) to similar events following device implementation (study group; n=221). Results: The study group (age 43 ± 22 years, body surface area burn 11.2 ± 18.0%, excision area 624, IQR 757 cm2, preoperative hemoglobin 10.7 ± 2.4 g/dl) did not differ significantly from the traditional group (age 42 ± 23 years (p=0.527), body surface area burn 12.2 ± 22.6% (p=0.661), excision area 753, IQR 505 cm2 (p=0.485), and preoperative hemoglobin 10.7 ± 2.2 g/dl (p=0.833). Postoperative transfusion rates were significantly lower in the study group (6.3% vs. 12.9%; p=0.024), as was the proportion of transfused patients undergoing multiple transfusion events (13.0% vs. 34.9%; p=0.01). Red cell dose (units/transfused patient) was less in the study group compared to the traditional group (1.83 ± 1.09 vs. 2.51 ± 1.61 units; p=0.021). In a subgroup of patients requiring excision of burned areas ≥ 1,000 cm2 (traditional group n=36, study group n=43), these differences were more significant. The postoperative transfusion rate fell from 44.4% to 14.0% (p=0.003), as did the percent of transfused patients experiencing multiple transfusion events (50.0% vs. 14.3%; p=0.004). Conclusions: Accurate measurement of surgical blood loss was associated with a decrease in transfusions suggesting more timely decision making. Informed transfusion decisions may result in fewer transfusions by avoiding over-transfusion related to both excessive hemodilution and inaccurate visual estimates.

Assessing the predictive capability of optical imaging techniques, Spatial Frequency Domain Imaging (SFDI) and Laser Speckle Imaging (LSI), to the gold standard of clinical assessment in a controlled animal model

The current standard for assessment of burn severity and subsequent wound healing is through clinical examination, which is highly subjective. Accurate early assessment of burn severity is critical for dictating the course of wound management. Complicating matters is the fact that burn wounds are often large and can have multiple regions that vary in severity. In order to manage the treatment more effectively, a tool that can provide spatially resolved information related to mapping burn severity could aid clinicians when making decisions. Several new technologies focus on burn care in an attempt to help clinicians objectively determine burn severity. By quantifying perfusion, laser speckle imaging (LSI) has had success in categorizing burn wound severity at earlier time points than clinical assessment alone. Additionally, spatial frequency domain imaging (SFDI) is a new technique that can quantify the tissue structural damage associated with burns to achieve earlier categorization of burn severity. Here we compared the performance of a commercial LSI device (PeriCam PSI, Perimed Inc.), a SFDI device (Reflect RSTM, Modulated Imaging Inc.) and conventional clinical assessment in a controlled (porcine) model of graded burn wound severity over the course of 28 days. Specifically we focused on the ability of each system to predict the spatial heterogeneity of the healed wound at 28 days, based on the images at an early time point. Spatial heterogeneity was defined by clinical assessment of distinct regions of healing on day 28. Across six pigs, 96 burn wounds (3 cm diameter) were created. Clinical assessment at day 28 indicated that 39 had appeared to heal in a heterogeneous manner. Clinical observation at day 1 found 35 / 39 (90%) to be spatially heterogeneous in terms of burn severity. The LSI system was able to detect spatial heterogeneity of burn severity in 14 / 39 (36%) cases on day 1 and 23 / 39 cases (59%) on day 7. By contrast the SFDI system was able to detect spatial heterogeneity of burn severity in 39 / 39 (100%) cases on day 1. Here we have demonstrated that for the purposes of predicting heterogeneity in wound healing, SFDI generated scattering properties were a significantly more effective tool than perfusion images measured using LSI. This indicates that SFDI may be better suited to help clinicians categorize different burns earlier, ultimately informing treatment strategy to improve patient outcomes.

How does blood loss relate to the extent of surgical wound excision

PURPOSE We investigated a novel system that uses image-processing algorithms to accurately measure the hemoglobin content of discarded surgical sponges to determine how blood loss relates to the excised area when current methods to minimize bleeding are employed. The system was used during 130 procedures in adult patients having wound excisions  ≥1% BSA (study group). An historic group of 105 similar cases in whom visually estimated blood was determined was also evaluated. RESULTS Surgical blood loss was less than previous estimates. The correlation between blood loss and the excised area in the study group was poor (R2=0.3988 for all patients and R2=0.1439 for excisions  ≥10% BSA). Moreover, the visual estimates of blood loss in the historic group were more closely related to excised area than the accurate measurements in the study group (R2=0.6017 (historic), R2=0.3988 (study), p<0.001 for both). The mean absolute unstandardized residuals were 140.18±158.52 (historic) vs. 307.99±317.03 (study), p<0.001. CONCLUSIONS As demonstrated in the historic group, visual estimates of blood loss tend to be more related to the size of excision than the amount of bleeding. The actual blood loss is not well correlated with the extent of excision. Clinicians should not rely on traditional blood loss estimates. Accurate measurement is needed to inform transfusion decisions and guide care.

Rising mortality in patients with combined burn and trauma

Combined trauma in the burn patient has been previously shown to have higher mortality. With improved critical care and multidisciplinary approach, we hypothesized the risk of mortality in combined burn and trauma has decreased. A retrospective analysis of trauma, burn and combined burn-trauma patients in the National Trauma Data Bank was performed comparing years 2007-2015 to years 1994-2002. The impact of burn injuries on mortality in patients with minor trauma has decreased (OR 2.45, CI 2.26-2.66, p<0.001 compared to OR 4.04, CI 4.51-4.66, p<0.001) in years 2007-2015 while the impact of burn injuries on mortality in patients with severe trauma has increased (OR 1.37, CI 1.29-1.47, p<0.001 compared to OR 1.26, CI 1.05-1.51, p<0.001). When controlling for known risk factors of mortality in burn and trauma, the contribution of the severity of trauma on mortality in combined burn-trauma patients with total body surface area ≥20% is negligible. In contrast, an increase in percentage of total body surface area burned is associated with a step-wise increase in mortality for all combined burn-trauma patients. However, the largest impact is seen in patients with minor trauma. This population represents a unique overlap of patients where future collaborative research can help identify best practices and improve outcomes.