A new algorithm to allow early prediction of mortality in elderly burn patients

Introduction

The elderly are the fastest growing population segment, and particularly susceptible to burns. Predicting outcomes for these patients remains difficult. Our objective was to identify early predictors of mortality in elderly burn patients.

Methods

Our Burn Center's prospective database was reviewed for burn patients 60+ treated in the past 10 years. Predictor variables were identified by correlative analysis and subsequently entered into a multivariate logistic regression analysis examining survival to discharge.

Results

203 patients of 1343 (15%) were eligible for analysis. The average age was 72 ± 10 (range 60–102) and the average total body surface area (TBSA) burned was 23 ± 18% (range 1–95). Age, TBSA, base deficit, pO₂, respiratory rate, Glasgow Coma Score (GCS), and Revised Trauma Score (RTS, based on systolic blood pressure, respiratory rate, and GCS) all correlated with mortality (p ≤ 0.05). Using multiple logistic regression analysis, a model with age, TBSA and RTS was calculated, demonstrating:

increased risk of mortality=β₀+1.12 (age)+1.094 (TBSA)+0.718 (RTS)$\text{increased risk of mortality}={\beta }_0+1.12(\text{age})+1.094(\text{TBSA})+0.718(\text{RTS})$     

Acid–base physiology: new concepts

The traditional approach to acid–base physiology is based on the Henderson–Hasselbalch equation which is derived from the CO₂/HCO₃⁻${\text{CO}}_2/{{\text{HCO}}_3}^{-}$ buffer system. However, it is becoming increasingly recognized that this is an incomplete analysis as it focuses on only one of the six reactions involving H⁺ and can lead to the incorrect assumption that CO₂ and HCO₃⁻${{\text{HCO}}_3}^{-}$ are independently adjusted factors that ultimately determine pH. In 1983, Stewart, a Canadian physiologist, proposed that a fuller understanding of acid–base physiology required consideration of biological fluids as a complex dynamic system, taking into account the interactions of all the chemical species involved. He showed that the true independent variables controlling the pH of any given fluid compartment are: the difference in the concentration of ‘strong ions’, the total concentration of ‘weak acid’, and the PCO₂. Importantly, H⁺ and HCO₃⁻${{\text{HCO}}_3}^{-}$ are dependent variables and it is incorrect to think of them as being specifically regulated to manipulate pH. This review will discuss the importance of pH homeostasis and highlight the implications of the Stewart approach in our understanding of acid–base control mechanisms and disorders. In particular, the true mechanisms by which the kidney regulates plasma pH will be discussed, emphasizing key misconceptions that have been propagated as a result of the traditional approach.     

A priori and a posteriori error estimates of H1‐Galerkin mixed finite element method for parabolic optimal control problems

In this exposition, we study both a priori and a posteriori error analysis for the H¹‐Galerkin mixed finite element method for optimal control problems governed by linear parabolic equations. The state and costate variables are approximated by the lowest order Raviart‐Thomas finite element spaces, whereas the control variable is approximated by piecewise constant functions. Compared to the standard mixed finite element procedure, the present method is not subject to the Ladyzhenskaya‐Babuska‐Brezzi condition and the approximating finite element spaces are allowed to be of different degree polynomials. A priori error analysis for both the semidiscrete and the backward Euler fully discrete schemes are analyzed, and $L^{\infty }(L^2)$ convergence properties for the state variables and the control variable are obtained. In addition, L²(L²)‐norm a posteriori error estimates for the state and control variables and $L^{\infty }(L^2)$‐norm for the flux variable are also derived.     

Acid–base physiology: new concepts

The traditional approach to acid–base physiology is based on the Henderson–Hasselbalch equation which is derived from the ${\text{CO}}_2/{{\text{HCO}}_3}^{?}$ buffer system. However, it is becoming increasingly recognized that this is an incomplete analysis as it focuses on only one of the six reactions involving H⁺ and can lead to the incorrect assumption that CO₂ and ${{\text{HCO}}_3}^{?}$ are independently adjusted factors that ultimately determine pH. In 1983, Stewart, a Canadian physiologist, proposed that a fuller understanding of acid–base physiology required consideration of biological fluids as a complex dynamic system, taking into account the interactions of all the chemical species involved. He showed that the true independent variables controlling the pH of any given fluid compartment are: the difference in the concentration of ‘strong ions’; the total concentration of ‘weak acid’; and the PCO₂. Importantly, H⁺ and ${{\text{HCO}}_3}^{?}$ are dependent variables and it is incorrect to think of them as being specifically regulated to manipulate pH. This review will discuss the importance of pH homeostasis and highlight the implications of the Stewart approach in our understanding of acid–base control mechanisms and disorders. In particular, the true mechanisms by which the kidney regulates plasma pH will be discussed, emphasizing key misconceptions that have been propagated as a result of the traditional approach.     

Risk Factors for Fractures Identified in the Algorithm Developed in 5-Year Follow-Up of Postmenopausal Women From RAC-OST-POL Study

The aim of the study was to establish factors with an impact on fracture risk and to develop an algorithm to predict osteoporotic fracture. A total of 978 postmenopausal women from the epidemiological, population-based RAC-OST-POL study with a mean age of 65.7?±?7.3 years were enrolled. At baseline, bone mineral density at hip and clinical risk factors for fracture were collected. Afterward, each person was asked annually on fracture incidence in the 5-year follow-up. Finally, data for complete 5-year observation were gathered for the group of 802 patients. During the follow-up, 92 osteoporotic fractures occurred in 78 women. The most common fracture site was the forearm (n?=?45). The following baseline factors were found as significant for fracture incidence: femoral neck bone mineral density, prior fractures, steroid use, falls within previous 12 months, and height. Fracture risk was predicted by the following formula: $\mathit{Risk}of\mathit{fracture}\mathit{incidence}=\frac{1}{1+e^{?\left(\begin{array}{l}?9.899+1.0771\mathit{STEROIDS}+0.681\\ 1\mathit{PRIORFALLS}+0.6111\mathit{PRIORFRACTURES}\\ ?0.4831FN\mathit{Tscore}+0.0421\mathit{HEIGHT}\end{array}\right)}}$. In our current longitudinal study, an algorithm predicting fracture occurrence over a period of 5 years was developed. It may find application in daily medical practice.     

Effects of Contrast Enhancement on In-Body Calibrated Phantomless Bone Mineral Density Measurements in Computed Tomography

We aimed to test the potential of phantomless volumetric bone mineral density (PLvBMD) measurements for the determination of volumetric bone mineral density (vBMD) in routine contrast-enhanced computed tomography (CECT). We evaluated 56 tri-phasic abdominal computed tomography scans, including an unenhanced scan as well as defined CECT scans in the arterial and portalvenous phase. PLvBMD analysis was performed by 4 radiologists using an FDA-approved tool for phantomless evaluation of bone density (IntelliSpace, Philips, The Netherlands). Mean vBMD of the first 3 lumbar vertebrae in each contrast phase was determined and interobserver variance of vBMD independent of contrast phase was analyzed using intraclass correlation, Bland-Altman plots, and Student's t test. CECT scans were associated with a significantly higher PLvBMD compared with unenhanced scans (unenhanced computed tomography: 97.8?mg/cc; arterial CECT: 106.3?mg/cc, portalvenous CECT: 106.3?mg/cc). Overall, there was no significant difference of PLvBMD between data acquisition in arterial and portalvenous phases (increase of 8.6% each, standard deviation ratio 37.7%–38.3%). In Bland-Altman analysis, there was no evidence of a relevant reader-related bias or an increase in standard deviation of PLvBMD measurements in contrast-enhanced scans compared with unenhanced scans. The following conversion formulas for unenhanced PLvBMD were determined: $\mathit{unenhanced}\mathit{PLvBMD}=0.89\times \mathit{arterial}\mathit{PLvBMD}+3,74mg/cc$(r²?=?0.94) and $\mathit{unenhanced}\mathit{PLvBMD}=0.88\times \mathit{venous}\mathit{PLvBMD}+4,56mg/cc$(r²?=?0.93). Compared with the results of phantom-based quantitative computed tomography measurements reported in the literature, the PLvBMD changes associated with contrast enhancement were relatively moderate with an increase of 8.6% in average. The time-point of the contrast-enhanced PLvBMD measurements after injection of contrast media did not appear to affect the results. With the adjustment formulas provided in this study, the method can improve osteoporosis screening through detection of reduced bone mass of the vertebrae in routinely conducted CECT.     

Effect of aspirin in coronary artery bypass grafting

To evaluate the effect of aspirin (ASA) therapy on postoperative blood loss, transfusion requirements, reoperation for bleeding, duration of stay in the intensive care unit and in the hospital in a selected population undergoing a first coronary artery bypass grafting (CABG) surgery. Prospective observational study in consecutive patients during a 3-month period. A teaching cardiothoracic center. Two hundred forty consecutive patients undergoing elective coronary artery bypass grafting surgery for the first time. Two hundred forty consecutive patients admitted for a first CABG the day before surgery were visited. Patients with an abnormal routine coagulation screen or taking drugs that might have affected their coagulation mechanisms were prospectively excluded (n = 96). The date of the last dose of ASA was recorded in the 144 remaining patients, and data were acquired prospectively. Total mediastinal blood drainage, blood products usage, reopening, and duration of intensive care unit and hospital stay were recorded. Patients were grouped by days free of ASA. There were no significant differences detected between groups. In patients undergoing a first CABG and with no known factors affecting their coagulation, ASA therapy did not appear to increase blood loss, reopening for bleeding, or blood products usage requirements during the hospital stay. ASA therapy did not influence the duration of stay in intensive care or in the hospital.     

Predictors of blood loss after coronary artery bypass grafting

To assess the predictive value of variables possibly associated with blood loss after coronary artery bypass grafting (CABG). A prospective study. A university hospital. Eighty-nine patients scheduled for elective CABG. Blood samples were drawn before and after surgery. Chest tube drainage was measured hourly until removal of drains. Activation of coagulation and fibrinolysis, routine clotting tests, and expression of platelet surface antigens were analyzed using flow cytometry. A significant correlation was found among blood loss and activated partial thromboplastin time, fibrinogen, prothrombin fragment 1 + 2, D-dimers, platelet count, GPlb and P-selectin expression on platelets, use of internal thoracic artery, cross-clamp time, and thrombin-antithrombin III complex. In a multiple regression model, glycoprotein (GP) Ib expression on platelets, platelet count, use of internal thoracic artery, and D-dimers were significantly associated with blood loss. Logistic regression analysis showed that GPIb and D-dimers predicted an increased blood loss with a positive predictive value of 73% and a negative predictive value of 91%. Postoperative D-dimers and GPIb expression may be useful to exclude nonsurgical causes in bleeding patients after CABG.     

The prognostic value of lymph node ratio and log odds of positive lymph nodes in patients with lung adenocarcinoma

Objective

To investigate whether lymph node ratio and log odds ratio can be used for predicting the prognosis of patients with lung adenocarcinoma.

Pain management in cardiac surgery patients: Comparison between standard therapy and patient-controlled analgesia regimen

To compare standard nurse-based pain therapy with a patient-controlled analgesia (PCA) regimen. Prospective, randomized study. Single-institutional, clinical investigation in an urban, university-affiliated hospital. Sixty patients undergoing elective first-time cardiac surgery were included. In 30 patients, a standard analgesic regimen was used, and in 30 patients, a PCA regimen was used. The perioperative and postoperative management was similar for all patients. Degree of sedation, satisfaction, and pain (by visual analog scale [Vas]) was assessed within the first 3 postoperative days. Vital capacity (VC) and forced expiratory volume in 1 second (FEV₁) were measured using a portable spirometry system. Cortisol and troponin T (TnT) plasma levels were also measured. The expectation of pain was similar in both groups, and the postoperative pain score was significantly lower in the PCA than in the standard group throughout the study period. Significantly more piritramid was used in the PCA (total, 75.6 ± 33.4mg) than in the standard group (total, 20.1 ± 31.9 mg). VC and FEV₁ were significantly lower in the standard group compared with the PCA patients. Cortisol and TnT plasma levels were similar in both groups. Frequency of side effects were similar for both groups. Because of the beneficial effects with regard to degree of pain and satisfaction, pain management using PCA systems can be recommended for cardiac surgery patients. It appears to be superior to standard nurse-based pain therapy.     

The effect of three different doses of tranexamic acid on blood loss after cardiac surgery with mild systemic hypothermia (32°C)

Prophylactic administration of tranexamic acid (TA), an antifibrinolytic agent, decreases bleeding after cardiac surgery with systemic hypothermia (25°C to 29°C). Warmer systemic temperatures during cardiopulmonary bypass (CPB) may reduce bleeding and thus alter the requirement for TA. The effect of three different doses of TA on bleeding after cardiac surgery with mild systemic hypothermia (32°C) is evaluated. Double-blind, prospective, randomized study. University hospital. One hundred fifty adult patients undergoing aortocoronary bypass or valvular cardiac surgery. Patients received TA, 50 (n = 50), 100 (n = 50), or 150 (n = 50) mg/kg intravenously before CPB with mild systemic hypothermia. Blood loss through chest drains over 6, 12, and 24 hours after surgery and total hemoglobin loss were measured. Autotransfused blood, transfused banked blood and blood products, and coagulation profiles were measured. Analysis of variance on log-transformed data for blood loss and confidence intervals (Cis) of 0.95 were calculated and transformed to milliliters of blood. No patient was re-explored for bleeding. Blood loss at 6 hours was statistically greater in the 50-mg/kg group compared with the other two groups (p = 0.03; p = 0.02). Total hemoglobin loss was statistically greater in the 50-mg/kg group compared with the 150-mg/kg group (p = 0.04). There was no statistical difference in blood transfusion rate or coagulation profiles among the three groups. However, preoperative hemoglobin level was statistically lower in the 150-mg/kg group compared with the other two groups (p = 0.01). Of the three doses of TA studied, the most efficacious and cost-effective dose to reduce bleeding after cardiac surgery with mild hypothermic systemic perfusion is 100 mg/kg.     

Comparison of the effects of red cell separation and ultrafiltration on heparin concentration during pediatric cardiac surgery

To determine the effects of red cell separation and ultrafiltration on heparin concentration. Prospective study. University-affiliated, pediatric medical center. Thirty-one children undergoing cardiac surgery. Blood sampled for heparin concentration and coagulation tests. Thirteen infants underwent modified veno-venous ultrafiltration (UF) after cardiopulmonary bypass (CPB). In addition, residual blood in the CPB circuit was hemoconcentrated by UF and reinfused (UF group). Heparin concentration increased from 2.0 ± 0.6 to 2.5 ± 0.8 U/mL, following modified UF; while activated coagulation time (ACT) decreased from 701 ± 177 to 627 ± 107 seconds. Heparin concentration of CPB circuit residual increased from 1.9 ± 0.7 to 3.1 ± 1.0 U/mL.In 18 children (older than 1 year old), the residual blood in the CPB circuit was hemoconcentrated by cell separation (CS) and reinfused (CS group). Heparin concentration of CPB circuit residual decreased from 2.6 ± 0.6 to 0.3 ± 0.2 U/mL. After reinfusion, patient heparin concentration remained unchanged at <0.05 U/mL. Thrombin time increased from 28 ± 6 to 48 ± 29 seconds and did not correlate with H. The plasma concentration of heparin increased after veno-venous modified UF of the patient. Heparin concentration also increased after UF of residual CPB circuit blood. In contrast, circuit blood hemoconcentrated by CS contained minimal heparin, and, when infused, did not increase patient's heparin concentration. ACT and thrombin time did not correlate with heparin concentration.