Burn Intensive Care Unit Patients Research Articles

Numerical and Clinical Accuracy of a Continuous Glucose Monitoring System during Intravenous Insulin Therapy in the Surgical and Burn Intensive Care Units

Intensive insulin therapy (IIT) for glycemic control in critically ill patients has been shown to be beneficial. Continuous glucose monitoring systems (CGMSs) have been approved as an adjunct to complement standard glucose monitoring in type 2 diabetes mellitus. This study was designed to evaluate the accuracy of a real-time CGMS (DexCom STS) in the intensive care unit (ICU). We also evaluated its reliability and accuracy using a hyperinsulinemic-euglycemic and a hyperglycemic clamp study. Nineteen patients were enrolled in this 7-day study [13 = surgical intensive care unit (SICU), 6 = burn intensive care unit (BICU)]. The patients were on IIT for at least 2 h prior the subcutaneous sensor insertion. Mean age and body mass index for SICU and BICU patients were 60.3 +/- 3.7 and 64.5 +/- 6.2 years and 36.6 +/- 5.0 and 33.85 +/- 3.4 kg/m2, respectively. DexCom accuracy was analyzed separately for the Johnson & Johnson (J&J) calibration finger sticks, Roche Accucheck finger sticks, and the Hitachi 917 analyzer measurements on serum using Clarke error grid analysis and Bland-Altman analysis. In the clamp studies, 20 patients were enrolled, and the data were analyzed similarly. There were 1065 pairs of DexCom-Accucheck, 232 pairs of DexCom-J&J, and 84 pairs of DexCom-Hitachi in ICU patients. For DexCom-Accucheck, 68.26% of the pairs fell into zone A, 31.83% into zone B, and 0.75% into zone C. There were no values in zones D or E. From the 1102 matching DexCom-Beckman pairs in clamp studies, 42.29% were in zone A, 55.90% were in zone B, and 4.08% were in zone C. Despite the high percentage of measurements in zones A and B, underestimation of hypoglycemia by DexCom measurements makes it an unreliable device in the ICU setting.

Insight in microcirculation and histomorphology during burn shock treatment using in vivo confocal-laser-scanning microscopy

Purpose Microcirculatory disturbances are well known during shock; however, the accompanied histomorphological alterations are widely unknown. We used high resolution confocal-laser-scanning microscopy for the evaluation of microcirculation and histomorphology during Burn Shock treatment. Methods Confocal-laser-scanning microscopy was performed in 10 burn shock patients (4 women, 6 men; aged 40.6 ± 11.4 years, burn extent >20% body surface area) initially and 24 hours after shock resuscitation. Ten matched hemodynamic stable burn intensive care unit patients served as controls. The following parameters were evaluated: quantitative blood cell flow, cell size of the granular layer, basal layer thickness, and epidermal thickness. Results Quantitative blood cell flow in controls was 62.45 ± 3.39 cells per minute. Burn shock significantly reduced blood cell flow to 37.27 ± 3.64 cells per minute; fluid resuscitation effectively restored baseline blood flow (65.18 ± 3.76 cells per minute) after 24 hours. Granular cell size was 793.61 ± 41.58 μm 2 in controls vs 644.27 ± 42.96 μm 2 during burn shock. Post resuscitation granular cell size measured 932.74 ± 38.83 μm 2. Basal layer thickness was 14.84 ± 0.59 μm in controls, 13.26 ± 0.54 μm in burn patients at admission and before resuscitation, and 17.50 ± 0.46 μm after resuscitation. Epidermal thickness in control patients was 49.60 ± 2.36 μm, 37.83 ± 2.47 μm in burn patients at admission and 69.50 ± 3.18 μm after resuscitation. Conclusions Confocal-laser-scanning microscopy provides a noninvasive tool for simultaneous evaluation of microcirculation and tissue histomorphology. It may help to assess the adequacy of and response to resuscitation of burn patients early after trauma.

The Respiratory Quotient has Little Value in Evaluating the State of Feeding in Burn Patients

The respiratory quotient (RQ) is frequently used to predict over or under feeding in burn patients. The purpose of our study was to evaluate the usefulness of RQ obtained from indirect calorimetry to assess feeding adequacy in pediatric burn Intensive Care Unit patients. We evaluated pediatric patients who received enteral nutrition by continuous duodenal tube feeding at a calculated goal rate in the burn intensive care unit from January 2003 to March 2006. RQ lower than 0.85 indicated underfeeding and RQ greater than 1.0 indicated overfeeding. Actual energy intake was recorded and compared with the energy intake divided by measured resting energy expenditure. Underfeeding was defined as a nutritional regimen providing <90% of caloric requirement; appropriate feeding was provision of within +/-10% of caloric requirements and overfeeding was provision of >110% of caloric requirements. On the basis of regression analysis, there was no relationship between energy intake divided by measured resting energy expenditure and RQ (R2 = 0.0059). There was also no relationship between measured RQ and the degree of feeding (N = 222). RQ <0.85 as an indicator of underfeeding had a low sensitivity of 40% and specificity of 77%. RQ >1.0 as an indicator of overfeeding had a poor sensitivity of 23% and a specificity of 85%. The RQ, used in isolation, is a poor method to assess over or underfeeding. Future prospective studies are needed to determine the optimal methodology for the assessment of nutritional needs in children with burn injury.

Error Rates Resulting From Anemia can be Corrected in Multiple Commonly Used Point-of-Care Glucometers

A point-of-care (POC) glucometer (G1) used for critical care at our institution is inaccurate in the presence of low hematocrit (HCT) values. The purpose of this study was to analyze error rates of three additional POC glucometer brands and determine mathematical correction formulas for each. Blood samples (n = 196) from a cohort of surgical, trauma, medical, cardiothoracic, and burn intensive care unit patients were tested on three commonly used POC glucometer brands (G2-G4). Results were compared with reference laboratory values, and correction compared with the validated formula for G1. A mathematical formula specific to each glucometer type was derived from glucose measurements, associated HCT values, and the degree of difference relative to laboratory results. POC glucometer results were consistently elevated compared with reference laboratory values. Glucometer error rates for HCT </= 25% ranged from 15.4% to 22.3% for the three types. Error rates for 25% < HCT < 34% ranged from 16.4% to 18.4%. A correction formula for each glucometer based on the natural log transformation of the HCT predicted reference values with a mean error rate of -0.54% +/- 5.6% for G2, -0.6% +/- 5.5% for G3, and 0.2% +/- 8.0% for G4. Correction was similar to that previously established for G1 (-0.01% +/- 4.8). Significant error rates because of HCT effect were found in all glucometer models tested with accurate prediction of reference values with a simple mathematical formula.

Patterns of exogenous insulin requirement reflect insulin sensitivity changes in trauma

Introduction We investigated patterns of blood glucose and exogenous insulin requirement in the intensive care unit, and questioned whether they reflect fluctuations in insulin activity. Methods Records for burn intensive care unit patients with 7 days of glucose control with insulin were reviewed. Hourly blood glucose and insulin dose were matched for time collected and analyzed with linear and cosine regression. Frequency analysis identified recurring patterns. Results Diurnal patterns of blood glucose and insulin requirement were noted (insulin troughs = noon; insulin peaks = midnight; glucose troughs = 5 am; glucose peaks = 5 pm). Average insulin requirement increased at a constant linear rate (slope = .013, r 2 = .57, P ≤ .001). Conclusions Diurnal patterns in blood glucose and insulin requirement mirror those of healthy subjects and may reflect persistence of normal variability in insulin activity. The 5-hour offset in peaks and troughs is suggestive of complex interplay between insulin availability and receptor sensitivity. The insulin requirement to blood glucose ratio increased, evidence that insulin resistance progresses over time.