Prediction of the mediastinal drainage after coronary artery bypass surgery.

Using multiple correlation and linear regression approaches, we investigated the association between the amount of mediastinal drainage for the first 24 postoperative hours and clinical variables as well as multiple haematological tests performed at three time points: before anaesthesia induction, 10 minutes after protamine administration and just after skin closure, on 46 patients undergoing primary coronary artery bypass grafting. Three models from the three times were then developed to predict mediastinal drainage. The number of internal mammary grafts, the total number of grafts and plasma fibrinogen concentration were useful predictors of mediastinal drainage at all three times. The platelet count taken only after skin closure was found to provide additional predictive information. Each regression model explained approximately 60% of the variation in postoperative mediastinal drainage. The information obtained from these predictive models is useful in defining high-risk populations.

The Effect of Preoperative Aspirin and/or Heparin Therapy on Coagulation and Postoperative Blood Loss after Coronary Artery Bypass Surgery.

OBJECTIVE: To assess the effects of preoperative aspirin and/or intravenous heparin therapy on perioperative coagulation tests and postoperative blood loss for 24-hour after coronary artery bypass surgery. METHODS: Multiple conventional coagulation tests, activated clotting time, thrombelastograph, skin bleeding time and platelet aggregation were performed before induction of anaesthesia, following protamine administration and after skin closure in 45 patients. RESULTS: There was no significant difference in either coagulation tests or postoperative blood loss (median of 860 mL with a range of 275 to 2800 mL, versus 833 ml with a range of 500-1380 mL) between the aspirin and no-aspirin patients. Preoperative heparin therapy affected most coagulation tests (e.g. international normalised ratio, activated partial thromboplastin time, thrombin clotting time, prothrombin time, activated clotting time and coagulation time of thrombelastography) before anaesthesia. The effects disappeared following protamine administration and after skin closure. Post operative blood loss was not significantly increased for the heparin group compared with the no-heparin group (median of 850 mL with a range of 700-1400 mL, versus 856 mL with a range of 275-2800 mL, respectively). Similar results were seen in patients receiving preoperative co-administration of aspirin and heparin compared with patients receiving aspirin alone. There was no suppression of platelet activity in patients receiving preoperative heparin or co-administration of aspirin and heparin. However, such suppression was found in patients receiving aspirin only. CONCLUSION: This study suggests that preoperative aspirin ingestion and intravenous heparin therapy should be administered as indicated and that concerns about the risk of postoperative bleeding should not lead to modification or cessation of such therapy.

Comparative assessment of electroglottographic and acoustic measures of jitter in pathological voices.

Jitter, or the amount of cycle-to-cycle variation in the fundamental frequency, is a characteristic of the vocal folds' vibration that may affect electroglottographic (EGG) and acoustic signals in similar ways, because the translaryngeal conductance and the oral pressure are modulated by the same physiological mechanism. Despite the apparent simplicity in jitter computation and the relative facility in recording and analyzing EGG signals, only a few studies comparing EGG and acoustic jitter have been reported. This can be attributed to the remarkable sensitivity of measures of acoustic jitter to such features as the type of sound being analyzed, the equipment used for data acquisition, or the algorithms used to identify glottal cycle boundaries. To assess the agreement achievable by measures from these signals in pathological voices, acoustic and EGG waveforms of sustained vowels (/i/, /a/, /u/) produced by 15 dysphonic patients were analyzed by jitter extraction methods on the basis of peaks, zero crossings, and a waveform matching technique. The agreement, expressed as normalized absolute differences between acoustic- and EGG-derived jitter, was poorer for /i/ and /u/ than for /a/ vowels. For /a/ vowels, a method of acoustic jitter estimation is also proposed that combines peaks and zero crossings and resulted in increased consistency with the zero crossing-based EGG measures (mean normalized absolute difference: 10.95%, SD: 6.44%; range: 23.81%). The proposed method, which has a built-in-test intended to reject unreliable estimates, may provide more confidence in acoustic measures in dysphonic speakers and lead to a better understanding of the relationships between acoustic and EGG signals.