Histidine metabolism after Bretschneider cardioplegia in cardiac surgical patients.

Bretschneider (histidine-tryptophan-ketoglutarate) solution with its high histidine concentration (198 mM) is one of many cardioplegic solutions, which are routinely used for cardiac arrest. The aim of this study was to evaluate the physiological biochemical degradation of administered histidine to histamine and its major urinary metabolite N-methylimidazole acetic acid. A total number of thirteen consecutive patients scheduled for elective isolated coronary artery bypass grafting with cardiopulmonary bypass were enrolled in the prospective observational designed study at the Department of Thoracic and Cardiovascular Surgery between 04/2016 and 06/2016. Patients received 1.7 l Bretschneider solution on average. Before and at the end of operation as well as in the postoperative course, urine samples gathered from the urinary catheter bag were analyzed. During the operative period, urinary histidine concentration significantly increased from 29 micromol/mmol creatinine to 9,609 micromol/mmol creatinine. Postoperatively, histidine excretion reduced while histamine as well as N-methylimidazole acetic acid excretion rose significantly. Patients showed elevated levels of histidine, histamine as well as N-methylimidazole acetic acid in urine, but no unmanageable hemodynamic instability possibly arising from the histamine's biological properties. Chemically modified histidine might reduce uptake and metabolization while maintaining the advantages of buffer capacity.

Risk factors for bleeding complications after percutaneous dilatational tracheostomy: a ten-year institutional analysis.

Bleeding complications after percutaneous dilatational tracheostomy (PDT) are infrequent but may have a tremendous impact on a patient's further clinical course. Therefore, it seems necessary to perform risk stratification for patients scheduled for PDT. We retrospectively reviewed the records of 1001 patients (46% male, mean age 68.1 years) undergoing PDT (using the Ciaglia Blue Rhino® technique with direct bronchoscopic guidance) in our cardiothoracic ICU between January 2003 and February 2013. Patients were stratified into two groups: patients suffering acute moderate, severe, or major bleeding (Group A) and patients who had no or only mild bleeding (Group B). In the majority of patients, no or only mild bleeding during PDT occurred (none: 425 [42.5%], mild: 488 [48.8%]). In 84 patients (8.4%), bleeding was classified as moderate. Three patients suffered from severe bleeding; only one major bleed with need for emergency surgery occured. Patients in Group A had a significantly higher Simplified Acute Physiology Score on the day of PDT (P=0.042), higher prevalence of renal replacement therapy on the day of PDT (P=0.026), higher incidence of coagulopathy (P=0.043), lower platelet counts (P=0.037), lower fibrinogen levels (P=0.012), higher proportion of PDTs performed by residents (P=0.034) and higher difficulty grading of PDT (P=0.001). Using logistic regression analyses, difficult PDT, less experienced operator, Simplified Acute Physiology Score>40 and low fibrinogen levels were independent predictors of clinically significant bleeding after PDT. Low fibrinogen levels, as well as difficult PDT, less experienced operator and Simplified Acute Physiology Score>40 are associated with an increased risk for bleeding during PDT.