M. Heldwein

A comparative study of four intensive care outcome prediction models in cardiac surgery patients

BackgroundOutcome prediction scoring systems are increasingly used in intensive care medicine, but most were not developed for use in cardiac surgery patients. We compared the performance of four intensive care outcome prediction scoring systems (Acute Physiology and Chronic Health Evaluation II [APACHE II], Simplified Acute Physiology Score II [SAPS II], Sequential Organ Failure Assessment [SOFA], and Cardiac Surgery Score [CASUS]) in patients after open heart surgery.MethodsWe prospectively included all consecutive adult patients who underwent open heart surgery and were admitted to the intensive care unit (ICU) between January 1st 2007 and December 31st 2008. Scores were calculated daily from ICU admission until discharge. The outcome measure was ICU mortality. The performance of the four scores was assessed by calibration and discrimination statistics. Derived variables (Mean- and Max- scores) were also evaluated.ResultsDuring the study period, 2801 patients (29.6% female) were included. Mean age was 66.9 ± 10.7 years and the ICU mortality rate was 5.2%. Calibration tests for SOFA and CASUS were reliable throughout (p-value not < 0.05), but there were significant differences between predicted and observed outcome for SAPS II (days 1, 2, 3 and 5) and APACHE II (days 2 and 3). CASUS, and its mean- and maximum-derivatives, discriminated better between survivors and non-survivors than the other scores throughout the study (area under curve ≥ 0.90). In order of best discrimination, CASUS was followed by SOFA, then SAPS II, and finally APACHE II. SAPS II and APACHE II derivatives had discrimination results that were superior to those of the SOFA derivatives.ConclusionsCASUS and SOFA are reliable ICU mortality risk stratification models for cardiac surgery patients. SAPS II and APACHE II did not perform well in terms of calibration and discrimination statistics.

Prediction of mortality in intensive care unit cardiac surgical patients

OBJECTIVES The purpose of this study was to develop a specific postoperative score in intensive care unit (ICU) cardiac surgical patients for the assessment of organ dysfunction and survival. To prove the reliability of the new scoring system, we compared its performance to existing ICU scores. METHODS This prospective study consisted of all consecutive adult patients admitted after cardiac surgery to our ICU over a period of 5.5 years. Variables were evaluated using the patients of the first year who stayed in ICU for at least 24h. The reproducibility was then tested in two validation sets using all patients. Performance was assessed with the Hosmer-Lemeshow (HL) goodness-of-fit test and receiver operating characteristic (ROC) curves and compared with the Acute Physiology and Chronic Health Evaluation (APACHE II) and Multiple Organ Dysfunction Score (MODS). The outcome measure was defined as 30-day mortality. RESULTS A total of 6007 patients were admitted to the ICU after cardiac surgery. Mean HL values for the new score were 5.8 (APACHE II, 11.3; MODS, 9.7) for the construction set, 7.2 (APACHE II, 8.0; MODS, 4.5) for the validation set I and 4.9 for the validation set II. The mean area under the ROC curve was 0.91 (APACHE II, 0.86; MODS, 0.84) for the new score in the construction set, 0.88 (APACHE II, 0.84; MODS, 0.84) in the validation set I and 0.92 in the validation set II. CONCLUSIONS Most of general ICU scoring systems use extensive data collection and focus on the first day of ICU stay. Despite this fact, general scores do not perform well in the prediction of outcome in cardiac surgical patients. Our new 10-variable risk index performs very well, with calibration and discrimination very high, better than general severity systems, and it is an appropriate tool for daily risk stratification in ICU cardiac surgery patients. Thus, it may serve as an expert system for diagnosing organ failure and predicting mortality in ICU cardiac surgical patients.

Third‐Generation Mobile Phones (UMTS) Do Not Interfere with Permanent Implanted Pacemakers

Aims:  Third‐generation mobile phones, UMTS (Universal Mobile Telecommunication System), were recently introduced in Europe. The safety of these devices with regard to their interference with implanted pacemakers is as yet unknown and is the point of interest in this study.

Gaseous emboli during off-pump surgery with T-graft technique, two different mechanisms

OBJECTIVES Gaseous embolism is a possible complication during off-pump coronary surgery with the use of a blower and can cause ischemic injuries. We describe two different possible mechanisms of carbon-dioxide embolization. METHODS Out of 2196 coronary bypass surgeries, between 1 January 2007 and 31 December 2009, there were 977 off-pump operations. Two off-pump cases (0.2%) had gaseous (carbon-dioxide) emboli that migrated against blood stream proximally through T-anastomoses and then into the native coronary vessels. These emboli caused a temporary haemodynamic deterioration in other territories. Two types of T-anastomoses were included [saphenous vein on left internal thoracic artery (LITA) or right internal thoracic artery (RITA) on LITA]. RESULTS Simple procedures and measurements were necessary but enough to regain haemodynamic stability. There was no effect on the postoperative outcome. CONCLUSION We have concluded that carbon-dioxide emboli can also cause massive but temporary haemodynamic deterioration during off-pump surgery despite higher solubility in blood. The blower should be used only when a bull-dog clamp is applied on the graft. Also, proper de-airing and flushing of grafts is very important and avoids consequences of the trapped small emboli.

Prognostic value of daily cardiac surgery score (CASUS) and its derivatives in cardiac surgery patients.

BACKGROUND We aimed to validate the usefulness of CASUS derivatives for cardiac surgery patients and their reliability for daily decision making. METHODS We included, prospectively, the data of all adult cardiac surgery patients who had an ICU stay of at least 12 hours between 20 January 2003 and 14 October 2005 in the Department of Cardiothoracic Surgery of the University of Cologne, Germany. Data were collected until ICU discharge and included initial, maximum, mean, and total CASUS values. δ CASUS (difference from initial value) was calculated at 48 and 96 hours postoperatively. The predictive efficacy of the derivatives was tested with calibration and discrimination statistics. RESULTS 2372 patients were included with a mean age of 66.2 ± 11.2 years. ICU mortality was 3.6 % (n =85). Mean ICU stay was 3.0 ± 6.1 days. The discrimination was very good for all derivatives (area under the curve ranged between 0.988 and 0.926). The calibration was also good except for the total CASUS, which showed a significant difference between the expected and observed mortality. Increased δ CASUS at 48 hours (1038 patients) and 96 hours (435 patients) correlated with an increase in mortality (23.1 % and 42.9 %, respectively), and conversely a decreased mortality rate was observed with decreasing values (1.9 % and 3.8 %, respectively). CONCLUSION CASUS derivatives including δ CASUS have a good prognostic value for cardiac surgery patients with regard to the prediction of mortality and survival during ICU stay, with the exception of total CASUS which was not informative.