A new device for intraoperative renal blood flow measurement during open-heart surgery: an experimental study and the clinical pilot study.

Renal blood flow (RBF) may vary during cardiopulmonary bypass and low flow may cause insufficient blood supply of the kidney triggering renal failure postoperatively. Still, a valid intraoperative method of continuous RBF measurement is not available. A new catheter combining thermodilution and intravascular Doppler was developed, first calibrated in an in vitro model, and the catheter specific constant was determined. Then, application of the device was evaluated in a pilot study in an adult cardiovascular population. The data of the clinical pilot study revealed high correlation between the flow velocities detected by intravascular Doppler and the RBF measured by thermodilution (Pearson's correlation range: 0.78 to 0.97). In conclusion, the RBF can be measured excellently in real time using the new catheter, even under cardiopulmonary bypass.

Treatment of gram-positive deep sternal wound infections in cardiac surgery--experiences with daptomycin.

The reported incidence of deep sternal wound infection (DSWI) after cardiac surgery is 0.4-5% with Staphylococcus aureus being the most common pathogen isolated from infected wound sternotomies and bacteraemic blood cultures. This infection is associated with a higher morbidity and mortality than other known aetiologies. Little is reported about the optimal antibiotic management. The aim of the study is to quantify the application of daptomycin treatment of DSWI due to gram-positive organisms post cardiac surgery. We performed an observational analysis in 23 cases of post sternotomy DSWI with gram-positive organisms February 2009 and September 2010. When the wound appeared viable and the microbiological cultures were negative, the technique of chest closure was individualised to the patient. The incidence of DSWI was 1.46%. The mean dose of daptomycin application was 4.4 ± 0.9 mg/kg/d and the average duration of the daptomycin application was 14.47 ± 7.33 days. In 89% of the patients VAC therapy was used. The duration from daptomycin application to sternal closure was 18 ± 13.9 days. The parameters of infection including, fibrinogen (p = 0.03), white blood cell count (p = 0.001) and C-reactive protein (p = 0.0001) were significantly reduced after daptomycin application. We had no mortality and wound healing was successfully achieved in all patients. Treatment of DSWI due to gram-positive organisms with a daptomycin-containing antibiotic regimen is safe, effective and promotes immediate improvement of local wound conditions.Based on these observations, daptomycin may offer a new treatment option for expediting surgical management of DSWI after cardiac surgery.

Comparison of urinary neutrophil glucosaminidase-associated lipocalin, cystatin C, and α1-microglobulin for early detection of acute renal injury after cardiac surgery.

OBJECTIVE: Acute renal injury is a frequent complication after cardiac surgery that necessitates additional treatment and increases mortality. To apply measures for optimizing renal function in a well-directed and effective way, it is most important to detect acute kidney injury at an early stage. The present study compares three markers of renal tubular function for detection of acute renal injury according to the acute kidney injury (Acute Kidney Injury Network (AKIN)) criteria. METHODS: Urinary concentration of the tubular markers neutrophil glucosaminidase-associated lipocalin (NGAL), α1-microglobulin (α1MG), and cystatin C (CysC) were measured in 50 patients after elective cardiac surgery. Samples were taken once preoperatively and postoperatively every 12 h for up to 5 days. Based on the highest recorded postoperative AKIN score, patients were divided into two groups (AKIN 0 and AKIN 1-3). Statistical analysis was done for marker concentrations at three time points: preoperative, after admission to the intensive care unit (ICU), and at the highest postoperative AKIN level. In addition, all concentrations of marker proteins were multiplied by the ratio of creatinine concentrations in serum and urine; these products were also analyzed statistically. In this way, we were able to eliminate the influence of varying degrees of diuresis on marker concentrations. RESULTS: As early as at admission to the ICU, all marker proteins showed significantly higher concentrations compared with preoperative values. However, differences in concentrations between the groups AKIN 0 and AKIN 1-3 were only statistically significant for NGAL. Using receiver operating characteristic (ROC) analysis, we found that only NGAL concentrations were suitable for detecting acute kidney injury with adequate sensitivity and specificity (area under the curve (AUC)=0.773). Levels of α1MG yielded a comparable accuracy when urinary concentrations were multiplied by the serum/urine creatinine ratio (AUC=0.712). CONCLUSION: An increase in urinary NGAL is an early sign of acute kidney injury after cardiac surgery. After multiplication by the serum/urine creatinine ratio, urinary α1MG is also suitable for detection of acute kidney injury at an early stage.

Validation of a clinical score to determine the risk of acute renal failure after cardiac surgery.

OBJECTIVE: Preoperative assessment of risk factors for postoperative acute renal failure (ARF) is a key point in the management of cardiac surgery patients. A reliable evaluation of individual risk permits the efficient application of prophylactic and therapeutic measures to patients with increased risk of ARF. In 2005, Thakar published a scoring system to determine the ARF risk prior to surgery. The score allowed calculation of the incidence of postoperative ARF requiring dialysis (ARF-D) with a high level of precision. METHODS: In order to examine the reproducibility of the results on different patient populations, we retrospectively applied the scoring system to 3,508 cardiac surgery patients at the Goettingen University Hospital. RESULTS: We found a qualitative correlation between the score value and ARF-D, but prognostic significance, when judged by the area under the receiver operating characteristic (ROC) curve, was considerably reduced. Also, the incidence of ARF-D in the Goettingen population was remarkably higher than the incidence shown by Thakar for patients with the same score. CONCLUSIONS: The correlation between score values and incidence of ARF-D shows that the Thakar score is qualitatively transferable to cardiac surgery patients from other centres. Though the score allows the discrimination between patients with higher or lower risks of ARF-D within the Goettingen collective, it was not suitable to estimate the real incidence of postoperative ARF-D with sufficient precision.