Year in review 2013: Critical Care--metabolism

Is there a relationship between nutritional goal achievement and pressure injury risk in intensive care unit patients receiving enteral nutrition?

OBJECTIVES

To assess pressure injury risk and time until pressure injury development according to the achievement of nutritional goals, i.e. caloric and protein intake within the first 72 hours of the intensive care admission.

METHOD

Prospective observational cohort study conducted in two units at a public university hospital. The development of pressure injury was considered the dependent variable. Survival curves were prepared with the Kaplan Meier method. Univariate and multivariate Cox regression analysis was used to identify factors associated with the development of pressure injury.

RESULTS

The study sample included 181 patients, of which 56.4% were male and the average age was 55 years. Neurological pathologies were the most frequent cause of hospitalisation (44.8%). The average length of stay was 17.5 days and mortality 30.4%. With regards to nutritional goals, 105 patients (58.0%) achieved their caloric goal, 130 (71.8%) achieved protein goals, and 98 (54.1%) achieved both. The frequency of pressure injury occurrence was 31.5%. Caloric intake (hazard ratio [HR] 2.3, 95% confidence interval [CI] 1.24-4.36) and protein intake (HR 3.21, 95% CI 1.76-5.86), were identified as independently associated with pressure injury development. Higher Braden scores were identified as a protective factor (HR 0.65, 95% CI 0.56-0.77).

CONCLUSIONS

These results indicate that the time to pressure injury development in the group of patients who did not achieve nutritional goals was shorter compared to those who achieved nutritional goals. Further studies should be conducted to confirm these data and to study the relationships in greater detail.

Insulin sensitivity in critically ill patients: are women more insulin resistant?

Background

Glycaemic control (GC) in intensive care unit is challenging due to significant inter- and intra-patient variability, leading to increased risk of hypoglycaemia. Recent work showed higher insulin resistance in female preterm neonates. This study aims to determine if there are differences in inter- and intra-patient metabolic variability between sexes in adults, to gain in insight into any differences in metabolic response to injury. Any significant difference would suggest GC and randomised trial design should consider sex differences to personalise care.

Methods

Insulin sensitivity (SI) levels and variability are identified from retrospective clinical data for men and women. Data are divided using 6-h blocks to capture metabolic evolution over time. In total, 91 male and 54 female patient GC episodes of minimum 24 h are analysed. Hypothesis testing is used to determine whether differences are significant (P < 0.05), and equivalence testing is used to assess whether these differences can be considered equivalent at a clinical level. Data are assessed for the raw cohort and in 100 Monte Carlo simulations analyses where the number of men and women are equal.

Results

Demographic data between females and males were all similar, including GC outcomes (safety from hypoglycaemia and high (> 50%) time in target band). Females had consistently significantly lower SI levels than males, and this difference was not clinically equivalent. However, metabolic variability between sexes was never significantly different and always clinically equivalent. Thus, inter-patient variability was significantly different between males and females, but intra-patient variability was equivalent.

Conclusion

Given equivalent intra-patient variability and significantly greater insulin resistance, females can receive the same benefit from safe, effective GC as males, but may require higher insulin doses to achieve the same glycaemia. Clinical trials should consider sex differences in protocol design and outcome analyses.

Insulin sensitivity in critically ill patients: are women more insulin resistant?

BACKGROUND

Glycaemic control (GC) in intensive care unit is challenging due to significant inter- and intra-patient variability, leading to increased risk of hypoglycaemia. Recent work showed higher insulin resistance in female preterm neonates. This study aims to determine if there are differences in inter- and intra-patient metabolic variability between sexes in adults, to gain in insight into any differences in metabolic response to injury. Any significant difference would suggest GC and randomised trial design should consider sex differences to personalise care.

METHODS

Insulin sensitivity (SI) levels and variability are identified from retrospective clinical data for men and women. Data are divided using 6-h blocks to capture metabolic evolution over time. In total, 91 male and 54 female patient GC episodes of minimum 24 h are analysed. Hypothesis testing is used to determine whether differences are significant (P < 0.05), and equivalence testing is used to assess whether these differences can be considered equivalent at a clinical level. Data are assessed for the raw cohort and in 100 Monte Carlo simulations analyses where the number of men and women are equal.

RESULTS

Demographic data between females and males were all similar, including GC outcomes (safety from hypoglycaemia and high (> 50%) time in target band). Females had consistently significantly lower SI levels than males, and this difference was not clinically equivalent. However, metabolic variability between sexes was never significantly different and always clinically equivalent. Thus, inter-patient variability was significantly different between males and females, but intra-patient variability was equivalent.

CONCLUSION

Given equivalent intra-patient variability and significantly greater insulin resistance, females can receive the same benefit from safe, effective GC as males, but may require higher insulin doses to achieve the same glycaemia. Clinical trials should consider sex differences in protocol design and outcome analyses.

Effects and mechanisms of glucose-insulin-potassium on post-procedural myocardial injury after percutaneous coronary intervention

OBJECTIVE

To evaluate the effects and mechanisms of glucose-insulin-potassium (GIK) on post-procedural myocardial injury (PMI) after percutaneous coronary intervention (PCI).

METHODS

A total of 200 non-diabetic patients with documented coronary heart disease (CHD) were divided into the Group GIK and Group G, with 100 patients in each group. Patients in Group G were given intravenous infusion of glucose solution 2 hours before PCI. As compared, patients in Group GIK were given GIK.

RESULTS

Both post-procedural creatine phosphokinase isoenzyme MB (CK-MB; 62.1 ± 47.8 vs. 48.8 ± 52.6 U/L, P = 0.007) and cTnI (0.68 ± 0.83 vs. 0.19 ± 0.24 ng/mL, P < 0.001) in Group GIK were significantly higher than those in Group G. In Group G, 9.0% and 4.0% of patients had post-procedural increases in CK-MB 1-3 times and > 3 times, which were significantly lower than those in Group GIK (14.0% and 7.0%, respectively; all P values < 0.01); 13.0% and 7.0% of patients had post-procedural increases in cTnI 1-3 times and > 3 times, which were also significantly lower than those in Group GIK (21.0% and 13.0%, respectively; all P < 0.001). Pre-procedural (10.2 ± 4.5 vs. 5.1 ± 6.3, P < 0.001) and post-procedural rapid blood glucose (RBG) levels (8.9 ± 3.9 vs. 5.3 ± 5.6, P < 0.001) in Group G were higher than those in Group GIK. In adjusted logistic models, usage of GIK (compared with glucose solution) remained significantly and independently associated with higher risk of post-procedural increases in both CK-MB and cTnI levels > 3 times. Furthermore, pre-procedural RBG levels < 5.0mmol/L were significantly associated with higher risk of post-procedural increases in both CK-MB and cTnI levels.

CONCLUSIONS

In non-diabetic patients with CHD, the administration of GIK may increase the risk of PMI due to hypoglycemia induced by GIK.

Elevated Glycemic Gap Predicts Acute Respiratory Failure and In-hospital Mortality in Acute Heart Failure Patients with Diabetes

Diabetes is a common comorbidity in patients hospitalized for acute heart failure (AHF), but the relationship between admission glucose level, glycemic gap, and in-hospital mortality in patients with both conditions has not been investigated thoroughly. Clinical data for admission glucose, glycemic gap and in-hospital death in 425 diabetic patients hospitalized because of AHF were collected retrospectively. Glycemic gap was calculated as the A1c-derived average glucose subtracted from the admission plasma glucose level. Receiver operating characteristic (ROC) curves were used to determine the optimal cutoff value for glycemic gap to predict all-cause mortality. Patients with glycemic gap levels >43 mg/dL had higher rates of all-cause death (adjusted hazard ratio, 7.225, 95% confidence interval, 1.355-38.520) than those with glycemic gap levels ≤43 mg/dL. The B-type natriuretic peptide levels incorporated with glycemic gap could increase the predictive capacity for in-hospital mortality and increase the area under the ROC from 0.764 to 0.805 (net reclassification improvement = 9.9%, p < 0.05). In conclusion, glycemic gap may be considered a useful parameter for predicting the disease severity and prognosis of patients with diabetes hospitalized for AHF.

In-vitro model for assessing glucose diffusion through skin

Pig ear skin membrane-covered glucose biosensor based on oxygen electrode has been assessed as a tool to evaluate glucose penetration through skin in-vitro. For this, glucose oxidase (GOx) was immobilised on oxygen electrode and covered with the skin membrane. Exposing this electrode to the solution of glucose resulted in glucose penetration though skin membrane, its oxidation catalysed by GOx, consumption of O₂ and decrease of the current of the oxygen electrode. By processing the biosensor responses to glucose, we found that glucose penetration through 250 µm thick skin membrane is slow; 90% of steady-state current response was reached in 32( ± 22) min. Apparent diffusion coefficient for glucose in skin was found to be equal to 0.15( ± 0.07)* 10^-6 cm² s^-1. This value is 45 times lower than glucose diffusion coefficient in water. Tape-stripping of stratum corneum (SC) allows considerably faster glucose penetration. The electrodes covered with tape-stripped skin reached 90% of steady-state current response in 5.0(± 2.7) min. The theoretical estimate of glucose flux through SC was considered exploiting four-pathway theory of transdermal penetration. Theoretical flux values were more that three orders lower than measured experimentally. This high discrepancy might indicate that glucose penetration through healthy human skin could be even slower, allowing much lower flux, than it was found in our study for skin membranes from pig ears.

Upper esophageal sphincter augmentation reduces pharyngeal reflux in nasogastric tube-fed patients

OBJECTIVES/HYPOTHESIS

Aspiration of gastric refluxate is one of the most commonly observed complications among long-term nasogastric tube (NGT) fed patients. The upper esophageal sphincter (UES) pressure barrier is the main defense mechanism against pharyngeal reflux of gastric contents. Our objective was to investigate the efficacy and safety of the UES assist device (UES-AD) in preventing gastric reflux through the UES in long-term NGT-fed patients.

STUDY DESIGN

Self-Controlled Case series.

METHODS

We studied 10 patients (mean age = 90.6 ± 3.4 years, four females) with dysphagia caused by stroke or dementia who were fed for 0.5 to 5 years (median = 3 years) by NGT. External pressures of 20 to 30 mm Hg were applied by using a handmade UES-AD, which was started 2 hours after the beginning of NGT infusion and was alternated between periods of 2 hours on and 2 hours off, for a total of 12 hours. Placement of the impedance sensors within the UES was guided by high-resolution manometry. Trans-UES and intraesophageal reflux events were recorded by using 24-hour combined pH-impedance measurements.

RESULTS

No aspiration pneumonia events were noted in the period 1 month before or during the study in any of the cohort. Baseline UES pressure averaged 17.5 ± 9.4 mm Hg and was increased to 38.9 ± 11.9mm Hg after application of the UES-AD. Overall frequency of trans-UES reflux decreased significantly with the UES-AD compared to without (0.8 ± 0.9 vs. 3.3 ± 2.8, P < .05 for the 12-hour study period). There was no effect of the UES-AD on esophageal reflux events (7.4 ± 4.4 vs. 6.4 ± 3.0, P > .05).

CONCLUSIONS

UES-AD significantly decreases the number of trans-UES reflux events and can potentially reduce the aspiration risk associated with NGT feeding.

LEVEL OF EVIDENCE

4. Laryngoscope, 128:1310-1315, 2018.

Critical Care Glucose Point-of-Care Testing

Maintaining blood glucose concentration within an acceptable range is a goal for patients with diabetes mellitus. Point-of-care glucose meters initially designed for home self-monitoring in patients with diabetes have been widely used in the hospital settings because of ease of use and quick reporting of blood glucose information. They are not only utilized for the general inpatient population but also for critically ill patients. Many factors affect the accuracy of point-of-care glucose testing, particularly in critical care settings. Inaccurate blood glucose information can result in unsafe insulin delivery which causes poor glucose control and can be fatal. Healthcare professionals should be aware of the limitations of point-of-care glucose testing. This chapter will first introduce glucose regulation in diabetes mellitus, hyperglycemia/hypoglycemia in the intensive care unit, importance of glucose control in critical care patients, and pathophysiological variables of critically ill patients that affect the accuracy of point-of-care glucose testing. Then, we will discuss currently available point-of-care glucose meters and preanalytical, analytical, and postanalytical sources of variation and error in point-of-care glucose testing.

An Elevated Glycemic Gap is Associated with Adverse Outcomes in Diabetic Patients with Acute Myocardial Infarction

Acute hyperglycemia is a frequent finding in patients presenting to the emergency department (ED) with acute myocardial infarction (AMI). The prognostic role of hyperglycemia in diabetic patients with AMI remains controversial. We retrospectively reviewed patients' medical records to obtain demographic data, clinical presentation, major adverse cardiac events (MACEs), several clinical scores and laboratory data, including the plasma glucose level at initial presentation and HbA1c levels. The glycemic gap, which represents changes in serum glucose levels during the index event, was calculated from the glucose level upon ED admission minus the HbA1c-derived average glucose (ADAG). We enrolled 331 patients after the review of medical records. An elevated glycemic gap between admission serum glucose levels and ADAG were associated with an increased risk of mortality in patients. The glycemic gap showed superior discriminative power regarding the development of MACEs when compared with the admission glucose level. The calculation of the glycemic gap may increase the discriminative powers of established clinical scoring systems in diabetic patients presenting to the ED with AMI. In conclusion, the glycemic gap could be used as an adjunct parameter to assess the severity and prognosis of diabetic patients presenting with AMI. However, the usefulness of the glycemic gap should be further explored in prospective longitudinal studies.

Establishment and Validation of GV-SAPS II Scoring System for Non-Diabetic Critically Ill Patients

BACKGROUND AND AIMS

Recently, glucose variability (GV) has been reported as an independent risk factor for mortality in non-diabetic critically ill patients. However, GV is not incorporated in any severity scoring system for critically ill patients currently. The aim of this study was to establish and validate a modified Simplified Acute Physiology Score II scoring system (SAPS II), integrated with GV parameters and named GV-SAPS II, specifically for non-diabetic critically ill patients to predict short-term and long-term mortality.

METHODS

Training and validation cohorts were exacted from the Multiparameter Intelligent Monitoring in Intensive Care database III version 1.3 (MIMIC-III v1.3). The GV-SAPS II score was constructed by Cox proportional hazard regression analysis and compared with the original SAPS II, Sepsis-related Organ Failure Assessment Score (SOFA) and Elixhauser scoring systems using area under the curve of the receiver operator characteristic (auROC) curve.

RESULTS

4,895 and 5,048 eligible individuals were included in the training and validation cohorts, respectively. The GV-SAPS II score was established with four independent risk factors, including hyperglycemia, hypoglycemia, standard deviation of blood glucose levels (GluSD), and SAPS II score. In the validation cohort, the auROC values of the new scoring system were 0.824 (95% CI: 0.813-0.834, P< 0.001) and 0.738 (95% CI: 0.725-0.750, P< 0.001), respectively for 30 days and 9 months, which were significantly higher than other models used in our study (all P < 0.001). Moreover, Kaplan-Meier plots demonstrated significantly worse outcomes in higher GV-SAPS II score groups both for 30-day and 9-month mortality endpoints (all P< 0.001).

CONCLUSIONS

We established and validated a modified prognostic scoring system that integrated glucose variability for non-diabetic critically ill patients, named GV-SAPS II. It demonstrated a superior prognostic capability and may be an optimal scoring system for prognostic evaluation in this patient group.

Role of Tyrosine Isomers in Acute and Chronic Diseases Leading to Oxidative Stress - A Review

Oxidative stress plays a major role in the pathogenesis of a variety of acute and chronic diseases. Measurement of the oxidative stress-related end products may be performed, e.g. that of structural isomers of the physiological para-tyrosine, namely meta- and ortho-tyrosine, that are oxidized derivatives of phenylalanine. Recent data suggest that in sepsis, serum level of meta-tyrosine increases, which peaks on the 2(nd) and 3(rd) days (p<0.05 vs. controls), and the kinetics follows the intensity of the systemic inflammation correlating with serum procalcitonin levels. In a similar study subset, urinary meta-tyrosine excretion correlated with both need of daily insulin dose and the insulin-glucose product in non-diabetic septic cases (p<0.01 for both). Using linear regression model, meta-tyrosine excretion, urinary meta-tyrosine/para-tyrosine, urinary ortho-tyrosine/para-tyrosine and urinary (meta- + orthotyrosine)/ para-tyrosine proved to be markers of carbohydrate homeostasis. In a chronic rodent model, we tried to compensate the abnormal tyrosine isomers using para-tyrosine, the physiological amino acid. Rats were fed a standard high cholesterol-diet, and were given para-tyrosine or vehicle orally. High-cholesterol feeding lead to a significant increase in aortic wall meta-tyrosine content and a decreased vasorelaxation of the aorta to insulin and the glucagon-like peptide-1 analogue, liraglutide, that both could be prevented by administration of para-tyrosine. Concluding, these data suggest that meta- and ortho-tyrosine are potential markers of oxidative stress in acute diseases related to oxidative stress, and may also interfere with insulin action in septic humans. Competition of meta- and ortho-tyrosine by supplementation of para-tyrosine may exert a protective role in oxidative stress-related diseases.

The Impact of Hypoglycemia on the Cardiovascular System: Physiology and Pathophysiology

Intensive glycemic control may increase cardiovascular (CV) risk and mortality due to hypoglycemia. The pathophysiology of glucose counter-regulation in patients with type 1 or type 2 diabetes for over 15 years is characterized by impairment of the defense mechanisms against hypoglycemia. Hypoglycemia causes pronounced physiological and pathophysiological effects on the CV system as consequences of autonomic system activation and counter regulatory hormones release. These effects provoke a series of hemodynamic changes that include an increase in heart rate and peripheral systolic blood pressure, a decrease in central blood pressure, reduced peripheral arterial resistance, and increased myocardial contractility and cardiac output. Cardiac electrophysiological changes including flattening or inversion of T waves, QT prolongation, and ST segment depression were observed in both insulin-induced and spontaneous hypoglycemia. Sympathoadrenal activation is the main cause of these changes through mechanisms that involve, but are not limited to, catecholamine-mediated hypokalemia. Hypoglycemia is also involved in platelet activation. There is growing concern about the long-term effects of hypoglycemia, especially as related to inflammation and atherogenesis.

Usefulness of Glycemic Gap to Predict ICU Mortality in Critically Ill Patients With Diabetes

Stress-induced hyperglycemia (SIH) has been independently associated with an increased risk of mortality in critically ill patients without diabetes. However, it is also necessary to consider preexisting hyperglycemia when investigating the relationship between SIH and mortality in patients with diabetes. We therefore assessed whether the gap between admission glucose and A1C-derived average glucose (ADAG) levels could be a predictor of mortality in critically ill patients with diabetes.We retrospectively reviewed the Acute Physiology and Chronic Health Evaluation II (APACHE-II) scores and clinical outcomes of patients with diabetes admitted to our medical intensive care unit (ICU) between 2011 and 2014. The glycosylated hemoglobin (HbA1c) levels were converted to the ADAG by the equation, ADAG = [(28.7 × HbA1c) - 46.7]. We also used receiver operating characteristic (ROC) curves to determine the optimal cut-off value for the glycemic gap when predicting ICU mortality and used the net reclassification improvement (NRI) to measure the improvement in prediction performance gained by adding the glycemic gap to the APACHE-II score.We enrolled 518 patients, of which 87 (17.0%) died during their ICU stay. Nonsurvivors had significantly higher APACHE-II scores and glycemic gaps than survivors (P < 0.001). Critically ill patients with diabetes and a glycemic gap ≥80 mg/dL had significantly higher ICU mortality and adverse outcomes than those with a glycemic gap <80 mg/dL (P < 0.001). Incorporation of the glycemic gap into the APACHE-II score increased the discriminative performance for predicting ICU mortality by increasing the area under the ROC curve from 0.755 to 0.794 (NRI = 13.6%, P = 0.0013).The glycemic gap can be used to assess the severity and prognosis of critically ill patients with diabetes. The addition of the glycemic gap to the APACHE-II score significantly improved its ability to predict ICU mortality.