Glycemic control in the burn intensive care unit: focus on the role of anemia in glucose measurement

THE RISKS OF FIRST ONSET PRIMARY HYPERTENSION DIAGNOSIS IN THERMAL-INJURED PATIENTS

ABSTRACT

Introduction: Hypertension is a prevalent condition in the United States and leads to an increased risk of developing various comorbidities. However, the impact of new-onset hypertension after severe burns on patient outcomes is not known. We posit that hypertension onset after severe burn is associated with increased risk of developing comorbidities and mortality. Methods: Using the TriNetX database, burned patients diagnosed with essential hypertension after injury were compared with those who did not develop hypertension; neither had prior hypertension. Each cohort was grouped by sex, percent total body surface area (TBSA) burned, and age, then propensity matched for sex, race, ethnicity, and laboratory values. Outcomes assessed were acute kidney injury (AKI), hyperglycemia, heart failure, myocardial infarction (MI), and death. Results: Those diagnosed with hypertension after severe burn were 4.9 times more likely to develop AKI, 3.6 times for hyperglycemia, 5.3 times for heart failure, 4.7 times for acute MI, and 1.5 times for mortality. Sex analysis shows that men were at greater risk for AKI (1.5 times), heart failure (1.1 times), and death (1.4 times). Women were 1.3 times more likely to develop hyperglycemia. Percent TBSA burned grouping showed increased risk for all outcomes with increasing severity. Age grouping indicated an elevated risk of developing AKI, heart failure, acute MI, and death. Conclusion: New-onset hypertension diagnosis in severely burned patients is associated with acute kidney injury, heart failure, acute MI, and death. Overall, males, older patients, and those with a higher % TBSA burned are at a higher risk of developing these comorbidities.

Results of a Multicenter Feasibility Study of an Automated Bedside Glucose Monitoring System in the Burn Intensive Care Setting

Intensive blood glucose regimens required for tight glycemic control in critically ill burn patients carry risk of hypoglycemia and are ultimately limited by the frequency of which serum glucose measurements can be feasibly monitored. Continuous inline glucose monitoring has the potential to significantly increase the frequency of serum glucose measurement. The objective of this study was to assess the accuracy of a continuous glucose monitor with inline capability (Optiscanner) in the burn intensive care setting. A multicenter, observational study was conducted at two academic burn centers. One hundred and six paired blood samples were collected from 10 patients and measured on the Optiscanner and the Yellow Springs Instrument. Values were plotted on a Clarke Error Grid and mean absolute relative difference calculated. Treatment was guided by existing hospital protocols using separately obtained values. 97.2% of results obtained from Optiscanner were within 25% of corresponding Yellow Springs Instrument values and 100% were within 30%. Mean absolute relative difference was calculated at 9.6%. Our findings suggest that a continuous glucose monitor with inline capability provides accurate blood glucose measurements among critically ill burn patients.

Accuracy of Blood Glucose Measurement and Blood Glucose Targets

BACKGROUND

To summarize new evidence regarding the methodological aspects of blood glucose control in the intensive care unit (ICU).

METHODS

We reviewed the literature on blood glucose control in the ICU up to August 2019 through Ovid Medline and Pubmed.

RESULTS

Since the publication of the Leuven studies, the benefits of glycemic control have been recognized. However, the methodology of blood glucose control, notably the blood glucose measurement accuracy and the insulin titration protocol, plays an important but underestimated role. This may partially explain the negative results of the large, pragmatic multicenter trials and made everyone realize that tight glycemic control with less-frequent glucose measurements on less accurate blood glucose meters is neither feasible nor advisable in daily practice. Blood gas analyzers remain the gold standard. New generation point-of-care blood glucose meters may be an alternative when using whole blood of critically ill patients in combination with a clinically validated insulin dosing algorithm.

CONCLUSION

When implementing blood glucose management in an ICU one needs to take into account the interaction between aimed glycemic target and blood glucose measurement methodology.

Glucose: archetypal biomarker in diabetes diagnosis, clinical management and research

The clinical utility of diabetes biomarkers can be considered in terms of diagnosis, management and prediction of long-term vascular complications. Glucose satisfies all of these requirements. Thresholds of hyperglycemia diagnostic of diabetes reflect inflections that confer a risk of developing long-term microvascular complications. Degrees of hyperglycemia (impaired fasting glucose, impaired glucose tolerance) that lie below the diagnostic threshold for diabetes identify individuals at risk of progression to diabetes and/or development of atherothrombotic cardiovascular disease. Self-measured glucose levels usefully complement hemoglobin A1c levels to guide daily management decisions. Continuous glucose monitoring provides detailed real-time data that is of value in clinical decision making, assessing response to new diabetes drugs and the development of closed-loop artificial pancreas technology.

Clinical Impact of Accurate Point-of-Care Glucose Monitoring for Tight Glycemic Control in Severely Burned Children

OBJECTIVES

The goal of this study was to retrospectively evaluate the clinical impact of an accurate autocorrecting blood glucose monitoring system in children with severe burns. Blood glucose monitoring system accuracy is essential for providing appropriate intensive insulin therapy and achieving tight glycemic control in critically ill patients. Unfortunately, few comparison studies have been performed to evaluate the clinical impact of accurate blood glucose monitoring system monitoring in the high-risk pediatric burn population.

DESIGN

Retrospective analysis of an electronic health record system.

SETTING

Pediatric burn ICU at an academic medical center.

PATIENTS

Children (aged < 18 yr) with severe burns (≥ 20% total body surface area) receiving intensive insulin therapy guided by either a noncorrecting (blood glucose monitoring system-1) or an autocorrecting blood glucose monitoring system (blood glucose monitoring system-2).

MEASUREMENTS AND MAIN RESULTS

Patient demographics, insulin rates, and blood glucose monitoring system measurements were collected. The frequency of hypoglycemia and glycemic variability was compared between the two blood glucose monitoring system groups. A total of 122 patient charts from 2001 to 2014 were reviewed. Sixty-three patients received intensive insulin therapy using blood glucose monitoring system-1 and 59 via blood glucose monitoring system-2. Patient demographics were similar between the two groups. Mean insulin infusion rates (5.1 ± 3.8 U/hr; n = 535 paired measurements vs 2.4 ± 1.3 U/hr; n = 511 paired measurements; p < 0.001), glycemic variability, and frequency of hypoglycemic events (90 vs 12; p < 0.001) were significantly higher in blood glucose monitoring system-1-treated patients. Compared with laboratory measurements, blood glucose monitoring system-2 yielded the most accurate results (mean ± SD bias: -1.7 ± 6.9 mg/dL [-0.09 ± 0.4 mmol/L] vs 7.4 ± 13.5 mg/dL [0.4 ± 0.7 mmol/L]). Blood glucose monitoring system-2 patients achieve glycemic control more quickly (5.7 ± 4.3 vs 13.1 ± 6.9 hr; p< 0.001) and stayed within the target glycemic control range longer compared with blood glucose monitoring system-1 patients (85.2% ± 13.9% vs 57.9% ± 29.1%; p < 0.001).

CONCLUSIONS

Accurate autocorrecting blood glucose monitoring system optimizes intensive insulin therapy, improves tight glycemic control, and reduces the risk of hypoglycemia and glycemic variability. The use of an autocorrecting blood glucose monitoring system for intensive insulin therapy may improve glycemic control in severely burned children.

The effects of intravenous vitamin C on point-of-care glucose monitoring

Ascorbic acid (vitamin C) decreases systemic inflammation and lowers fluid requirements after thermal injury; therefore it has been adopted in many burn centers as an adjunct to resuscitation. However, recent concerns have been expressed over clinically significant hypoglycemic events caused by vitamin C interference with the point-of-care (POC) glucose measurements. This case series presents a direct comparison of POC and laboratory reference glucose values in the patients receiving vitamin C infusion. Vitamin C was administered at 66 mg/kg/hour in seven patients with burns >30% TBSA. The baseline characteristics and burn characteristics were recorded. POC glucose measurements were made with a commonly used hand-held device, and the laboratory values were obtained using standard spectrophotometric methods. POC and laboratory glucose values drawn within the same hour were compared. Hemoglobin, which is known to cause interference in POC testing, was also recorded. All the patients demonstrated falsely elevated POC glucose values during and/or immediately after the infusion period, with discrepancies ranging from 10 to 200 mg/dl. These findings were irregular, unpredictable and unrelated to hemoglobin levels. The findings suggest an idiosyncratic reaction that cannot be easily corrected at the bedside using mathematical equations. POC glucose monitoring should be avoided during and after vitamin C therapy.

Clinical impact of sample interference on intensive insulin therapy in severely burned patients: a pilot study

Severely burned patients benefit from intensive insulin therapy (IIT) for tight glycemic control (TGC). The authors evaluated the clinical impact of automatic correction of hematocrit and ascorbic acid interference for bedside glucose monitoring performance in critically ill burn patients. The performance of two point-of-care glucose monitoring systems (GMSs): 1) GMS1, an autocorrecting device, and 2) GMS2, a noncorrecting device were compared. Sixty remnant arterial blood samples were collected in a prospective observational study to evaluate hematocrit and ascorbic acid effects on GMS1 vs GMS2 accuracy paired against a plasma glucose reference. Next, we enrolled 12 patients in a pilot randomized controlled trial. Patients were randomized 1:1 to receive IIT targeting a TGC interval of 111 to 151 mg/dl and guided by either GMS1 or GMS2. GMS bias, mean insulin rate, and glycemic variability were calculated. In the prospective study, GMS1 results were similar to plasma glucose results (mean bias, -0.75 [4.0] mg/dl; n = 60; P = .214). GMS2 results significantly differed from paired plasma glucose results (mean bias, -5.66 [18.7] mg/dl; n = 60; P = .048). Ascorbic acid therapy elicited significant GMS2 performance bias (29.2 [27.2]; P < .001). Randomized controlled trial results reported lower mean bias (P < .001), glycemic variability (P < .05), mean insulin rate (P < .001), and frequency of hypoglycemia (P < .001) in the GMS1 group than in the GMS2 group. Anemia and high-dose ascorbic acid therapy negatively impact GMS accuracy and TGC in burn patients. Automatic correction of confounding factors improves glycemic control. Further studies are warranted to determine outcomes associated with accurate glucose monitoring during IIT.

Hypoglycemia is associated with increased postburn morbidity and mortality in pediatric patients

OBJECTIVE

The objective of this study was to determine the prevalence of hypoglycemia after burn injury and whether hypoglycemia is associated with increased postburn morbidity and mortality.

DESIGN

Cohort analysis.

SETTING

Academic pediatric burn hospital.

PATIENTS

This analysis included 760 pediatric burn patients, who were stratified according the number of hypoglycemic episodes (< 60 mg/dL glucose) they experienced while in the ICU. Clinical outcomes and metabolic and inflammatory biomarkers were analyzed during the first 60 days post admission. Patients with one or more hypoglycemic events were matched with patients not experiencing any event using propensity score matching, and outcomes and biomarker expression were compared between groups.

MEASUREMENTS AND MAIN RESULTS

Eighty-four patients had one episode of hypoglycemia, 108 patients had two or more episodes of hypoglycemia, and 568 patients never experienced hypoglycemia. Patients with one or more hypoglycemic episodes had longer hospitalization, as well as more frequent infections, sepsis, multiple organ failure, and death (p < 0.05). The 166 propensity score-matched patients with one or more hypoglycemic events had greater inflammatory and metabolic responses, prevalence of sepsis, multiple organ failure, and mortality than burn patients without hypoglycemic (p < 0.05).

CONCLUSIONS

Hypoglycemic episodes correlate with injury severity and inhalation injury. When adjusted for injury severity, hypoglycemia is associated with significantly higher postburn morbidity and mortality.

Glycemic management in medical and surgical patients in the non-ICU setting

Hyperglycemia is commonly observed in hospitalized patients with and without previously known diabetes and is associated with adverse outcomes. For this reason, measurement of blood glucose (BG) is recommended for all patients at admission. Measurement of an A1C identifies patients with either newly recognized diabetes or uncontrolled diabetes. Current guidelines advise fasting and premeal BG <140 mg/dl, with maximal random BG <180 mg/dl for the majority of noncritically ill patients. Rational use of basal bolus insulin (BBI) regimens is effective in achieving these glycemic goals, with low risk for hypoglycemia. The safety of BBI relies upon provider knowledge for initiation and adjustment of insulin doses for changes in nutritional status or use of medications affecting glucose metabolism. Smooth transition of care to the outpatient setting is facilitated by providing oral and written instructions regarding timing and dosing of insulin, as well as education in basic skills for home management.

Glycemic targets and approaches to management of the patient with critical illness

Hyperglycemia during critical illness is associated with adverse outcome. The proof-of-concept Leuven studies assessed causality, and revealed that targeting strict normoglycemia (80-110 mg/dL) with insulin improved outcome compared with tolerating hyperglycemia to the renal threshold (215 mg/dL). A large multicenter trial (NICE-SUGAR [Normoglycaemia in Intensive Care Evaluation and Survival Using Glucose Algorithm Regulation]) found an intermediate blood glucose target (140-180 mg/dL) safer than targeting normoglycemia. Differences in design and in execution of glycemic control at the bedside may have contributed to these results. In NICE-SUGAR (Normoglycaemia in Intensive Care Evaluation and Survival Using Glucose Algorithm Regulation), the blood-glucose target range in the control group was lower, there were problems to reach and maintain normoglycemia in the intervention group, and inaccurate handheld blood glucose meters and variable blood sampling sites were allowed. Inaccurate tools led to insulin-dosing errors with consequently (undetected) hypoglycemia and unacceptable blood glucose variability. Also, the studies were done superimposed upon different nutritional strategies. Thus, such differences do not allow simple, evidence-based recommendations for daily practice, but an intermediate blood glucose target may be preferable while awaiting better tools to facilitate safely reaching normoglycemia.

Blood glucose measurements in critically ill patients

Studies on tight glycemic control by intensive insulin therapy abruptly changed the climate of limited interest in the problem of hyperglycemia in critically ill patients and reopened the discussion on accuracy and reliability of glucose sensor devices. This article describes important components of blood glucose measurements and their interferences with the focus on the intensive care unit setting. Typical methodologies, organized from analytical accuracy to clinical accuracy, to assess imprecision and bias of a glucose sensor are also discussed. Finally, a list of recommendations and requirements to be considered when evaluating (time-discrete) glucose sensor devices is given.

Tight glycemic control in critical care--the leading role of insulin sensitivity and patient variability: a review and model-based analysis

Tight glycemic control (TGC) has emerged as a major research focus in critical care due to its potential to simultaneously reduce both mortality and costs. However, repeating initial successful TGC trials that reduced mortality and other outcomes has proven difficult with more failures than successes. Hence, there has been growing debate over the necessity of TGC, its goals, the risk of severe hypoglycemia, and target cohorts. This paper provides a review of TGC via new analyses of data from several clinical trials, including SPRINT, Glucontrol and a recent NICU study. It thus provides both a review of the problem and major background factors driving it, as well as a novel model-based analysis designed to examine these dynamics from a new perspective. Using these clinical results and analysis, the goal is to develop new insights that shed greater light on the leading factors that make TGC difficult and inconsistent, as well as the requirements they thus impose on the design and implementation of TGC protocols. A model-based analysis of insulin sensitivity using data from three different critical care units, comprising over 75,000h of clinical data, is used to analyse variability in metabolic dynamics using a clinically validated model-based insulin sensitivity metric (S(I)). Variation in S(I) provides a new interpretation and explanation for the variable results seen (across cohorts and studies) in applying TGC. In particular, significant intra- and inter-patient variability in insulin resistance (1/S(I)) is seen be a major confounder that makes TGC difficult over diverse cohorts, yielding variable results over many published studies and protocols. Further factors that exacerbate this variability in glycemic outcome are found to include measurement frequency and whether a protocol is blind to carbohydrate administration.