Bedside Calculation of Energy Expenditure Does Not Guarantee Adequate Caloric Prescription in Long-Term Mechanically Ventilated Critically Ill Patients: A Quality Control Study

Nutrition is essential in critically ill patients, but translating caloric prescriptions into adequate caloric intake remains challenging. Caloric prescriptions (P), effective intake (I), and caloric needs (N), calculated with modified Harris-Benedict formulas, were recorded during seven consecutive days in ventilated patients. Adequacy of prescription was estimated by P/N ratio. I/P ratio assessed accuracy of translating a prescription into administered feeding. I/N ratio compared delivered calories with theoretical caloric needs. Fifty patients were prospectively studied in a mixed medicosurgical ICU in a teaching hospital. Basal and total energy expenditure were, respectively, 1361 ± 171 kcal/d and 1649 ± 233 kcal/d. P and I attained 1536 ± 602 kcal/d and 1424 ± 572 kcal/d, respectively. 24.6% prescriptions were accurate, and 24.3% calories were correctly administered. Excessive calories were prescribed in 35.4% of patients, 27.4% being overfed. Caloric needs were underestimated in 40% prescriptions, with 48.3% patients underfed. Calculating caloric requirements by a modified standard formula covered energy needs in only 25% of long-term mechanically ventilated patients, leaving many over- or underfed. Nutritional imbalance mainly resulted from incorrect prescription. Failure of “simple” calculations to direct caloric prescription in these patients suggests systematic use of more reliable methods, for example, indirect calorimetry

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

The cientificWorldJOURNAL Research Article Bedside Calculation of Energy Expenditure Does Not Guarantee Adequate Caloric Prescription in Long-Term Mechanically Ventilated Critically Ill Patients: A Quality Control Study

Nutrition is essential in critically ill patients, but translating caloric prescriptions into adequate caloric intake remains challenging. Caloric prescriptions (P), effective intake (I), and caloric needs (N), calculated with modified Harris-Benedict formulas, were recorded during seven consecutive days in ventilated patients. Adequacy of prescription was estimated by P/N ratio. I/P ratio assessed accuracy of translating a prescription into administered feeding. I/N ratio compared delivered calories with theoretical caloric needs. Fifty patients were prospectively studied in a mixed medicosurgical ICU in a teaching hospital. Basal and total energy expenditure were, respectively, 1361 ± 171 kcal/d and 1649 ± 233 kcal/d. P and I attained 1536 ± 602 kcal/d and 1424 ± 572 kcal/d, respectively. 24.6% prescriptions were accurate, and 24.3% calories were correctly administered. Excessive calories were prescribed in 35.4% of patients, 27.4% being overfed. Caloric needs were underestimated in 40% prescriptions, with 48.3% patients underfed. Calculating caloric requirements by a modified standard formula covered energy needs in only 25% of long-term mechanically ventilated patients, leaving many over-or underfed. Nutritional imbalance mainly resulted from incorrect prescription. Failure of "simple" calculations to direct caloric prescription in these patients suggests systematic use of more reliable methods, for example, indirect calorimetry. Background Delivering a correct amount of calories to critically ill patients is considered to be of cardinal importance Still, discrepancies between theoretical energy requirements and actual delivery of nutrition in intensive care unit (ICU) patients are more rule than exception Methods The study was approved by the hospital's Ethical Committee. Due to its observational nature, the need for informed consent was waived. During a 4-month period, we included all patients older than 18 years admitted to our medicosurgical ICU when intubated and expected to receive mechanical ventilation for at least seven days. Patients were ventilated in pressure-or volume-controlled modes under continuous analgesic sedation with remifentanil and midazolam. Whenever possible, intravenous dextrose infusions were avoided. Insulin was infused to maintain a target blood glucose level of 80-110 mg/dL. All subjects received enteral and/or parenteral feeding, as part of their standard treatment. Feeding was provided according to a dedicated nutritional care plan. The used protocol closely reflected current evidence-based, easyto-use feeding algorithms indicating amount, composition and route of delivery. Gender, age, weight, height, and type of pathology were recorded at study entry. For obese patients, optimal caloric intake was calculated for a theoretical weight corresponding to a body mass index of 30 kg/m 2 Attending ICU physicians, unaware of the study, based their daily caloric prescriptions on the expert-recommended 25 kcal/kg/d regimen Statistical analysis used SPSS 12.0 for Windows (Chicago, IL, USA). Results were expressed as means ± standard deviation and medians (range). Means between groups were compared with the Student's t-test. Statistical significance was accepted at a P value < 0.05. Results 579 patients were admitted to the ICU during the study period. 231 subjects were mechanically ventilated. Of the 81 patients meeting enrolment criteria, thirty-one were excluded from analysis. Reasons for exclusion were extubation before day 7 (n = 14), tracheostomy (n = 6), donot-resuscitate order given (n = 3), and death (n = 8). Finally, fifty patients, 28 males and 22 females, representing a total of 350 nutrition days, were studied. Mean age was 65 (range 34-84) years. Mean body weight and length were, respectively, 76.9 ± 18.3 kg and 169.6 ± 9.7 cm. Twelve patients were obese. Mean APACHE II score was 28 ± 12. Mean resting energy expenditure for all studied patients was 1361 ± 171 kcal/d. Thirteen patients were allocated a stress factor 1.1, 18 patients received 1.2, and 19 subjects were assigned a factor 1.3. This resulted in a mean total energy expenditure of 1649 ± 233 kcal/d. The mean daily amount of calories prescribed during the 350 study days reached 1536 ± 602 kcal. In average, 1424 ± 572 kcal/d were actually delivered to the patient. P and I varied with time 24.6% of the 350 nutritional prescriptions correctly estimated the need. In 40.0% of cases, nutritional needs were insufficiently covered. Overestimation occurred in the remaining 35.4%. Using similar cutoff percentages to evaluate effective feeding, patients were, respectively, correctly, over-, or underfed in 24.3%, 27.4%, and 48.3% of the nutrition days. Underfeeding was more frequent on the first as compared to the next 6 ventilation days The amount of effectively administered calories varied with time. Caloric prescription resulted in accurate delivery in 56.0% of cases. However, effective feeding was not met in 32.6% of prescriptions, and in 9.14% actual feeding surpassed the prescribed amount by more than 10%. The Scientific World Journal Mean P/N ratio rose from 59.3 on day 1 to 102.7 on day 7, whilst the median I/N ratio increased from 62.6 to 97 during the same period. Thus, both estimation of needs and actually administered feeding improved with time. The delivery rate did not vary significantly during the observation period Discussion Nutrition is an indispensable part of overall treatment in critically ill patients. Fundamental goals of nutritional support in the ICU are to meet energy requirements of (hyper)metabolic processes, to prevent nutrient deficiencies and to minimize protein catabolism. Whilst inadequate nutrition, in general, is known to significantly compromise outcome in the critically ill, its unwarranted effects may be even more pronounced in mechanically ventilated patients. Indeed, animals submitted to fasting or receiving long-term hypocaloric feeding in both aerobe and anaerobe conditions experienced muscle decay and dysfunction which incompletely recovered after realimentation Throughout the literature, most discussion regarding nutrition in mechanically ventilated patients is focused on type, composition, and caloric/nitrogen content of available feeding liquids. However, evaluating adequate, that is, correct and effective, feeding in this population remains challenging. The present study confirms that energetic requirements in critically ill, mechanically ventilated patients differ considerably in accordance to the severity of the underlying pathology. In general, energetic needs were well anticipated by the attending physicians, yet variations were large. 25% of the caloric prescriptions were correct, but a stunning 75% resulted in under-or overfeeding. Effective administration of calories followed the same trend as the prescription. However, energetic requirements were met in only 24% of the feeding days. The discrepancy between caloric prescription and intake caused underfeeding in nearly half and overfeeding in 27% of the study days. Our findings also highlighted that nutritional prescription was fairly well translated into effective feeding in the majority of patients but that extreme variations in intake/prescription ratio (up to 720% !) could occur. A possible explanation is that oral nutrition orders were executed without being recorded in the patient's files. Our results, demonstrating (a) > 90% I/P and P/N ratio after 72 hours, are in agreement and even better than those reported recently by Quenot et al. Thirty years ago, Driver and LeBrun described iatrogenic malnutrition in more than 80% of mechanically ventilated patients 4 The Scientific World Journal However, this study is different from ours since patients were given only enteral feeding Nutritional care of critically ill patients is complicated. Patients form heterogeneous groups that are prone to significant and continuous metabolic fluctuations induced by type, severity, and evolution of the disease process. In addition, confounding variables such as over-or underweight, resuscitation edema, and concomitant medication (e.g., sedation) may all hamper correct estimation of metabolic demands Our study has several shortcomings. First, calculations of caloric intake did not account for caloric content of eventually administered dextrose-containing infusions. Second, caloric requirements ideally should be measured by indirect calorimetry. Feeding near-target energy requirements based on repeated calorimetric measurements was associated with lower hospital mortalit