Turbulence in surgical suction heads as detected by MRI.

BACKGROUND: Blood loss is common during surgical procedures, especially in open cardiac surgery. Allogenic blood transfusion is associated with increased morbidity and mortality. Blood conservation programs in cardiac surgery recommend re-transfusion of shed blood directly or after processing, as this decreases transfusion rates of allogenic blood. But aspiration of blood from the wound area is often associated with increased hemolysis, due to flow induced forces, mainly through development of turbulence. METHODS: We evaluated magnetic resonance imaging (MRI) as a qualitative tool for detection of turbulence. MRI is sensitive to flow; this study uses velocity-compensated T1-weighted 3D MRI for turbulence detection in four geometrically different cardiotomy suction heads under comparable flow conditions (0-1250 mL/min). RESULTS: Our standard control suction head Model A showed pronounced signs of turbulence at all flow rates measured, while turbulence was only detectable in our modified Models 1-3 at higher flow rates (Models 1 and 3) or not at all (Model 2). CONCLUSIONS: The comparison of flow performance of surgical suction heads with different geometries via acceleration-sensitized 3D MRI revealed significant differences in turbulence development between our standard control Model A and the modified alternatives (Models 1-3). As flow conditions during measurement have been comparable, the specific geometry of the respective suction heads must have been the main factor responsible. The underlying mechanisms and causative factors can only be speculated about, but as other investigations have shown, hemolytic activity is positively associated with degree of turbulence. The turbulence data measured in this study correlate with data from other investigations about hemolysis induced by surgical suction heads. The experimental MRI technique used showed added value for further elucidating the underlying physical phenomena causing blood damage due to non-physiological flow.

A New Evaluation Q-Factor to Be Calculated for Suction Geometries as a Basis for Smooth Suction in the Operating Field to Ensure the Highest Possible Blood Integrity for Retransfusion Systems.

Blood hemolysis caused by mechanical impact is a serious problem in medicine. In addition to the heart-lung machine (artificial surfaces, flow irritating connection points) which contributes to hemolysis, blood suction and surgical suction devices are influencing factors. Goal of our research is to develop best flow optimizing suction geometry that represents the best compromise between all influencing effects. Based on data that negative pressure and turbulence have a negative impact on blood components, 27 surgical suction tips have been examined for acoustic stress and negative pressure behavior. Furthermore, a dimensionless factor Q was introduced to assess the overall performance of the suction tips investigated.

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.

The risk-to-benefit ratio of transcatheter aortic valve implantation in specific patient cohorts: a single-centre experience.

BACKGROUND: Transcatheter aortic valve implantation (TAVI) has recently developed into an acceptable alternative to conventional surgery in high-risk patients. However, information on the identification of patients gaining most benefit from this procedure is still limited. The aim of this study was to evaluate safety and efficacy of TAVI in different patient cohorts. METHODS: Between August 2008 and December 2010, 180 high-risk patients underwent TAVI at our institution (97 transapical and 83 transfemoral approaches). Periprocedural complications as well as mortality and incidence of MACCE during follow-up were recorded. RESULTS: Mean age was 82 ± 5 years, and mean logistic EuroScore 27 ± 14%. In the total cohort, 30-day mortality was 8.9% and 12-month survival (according to Kaplan-Meier-analysis) 72%, with no significant differences between the two approaches. However, a significant difference in survival was obvious after stratification of patients according to logistic EuroScore mortality estimates. Survival proportions at 1 year were 62% in patients with logistic EuroScore >40%, 71% in patients with EuroScore 20-40% and 80% in octogenarians with EuroScore <20% (P = 0.009). Furthermore, the observed median event-free survival as an indicator for morbidity ranged between 315 days in the first, 442 days in the second and 710 days in the third group (P = 0.1). CONCLUSIONS: TAVI proved to be feasible with reproducible results. However, mortality and rehospitalization rates were considerably high in specific patient cohorts, suggesting that the risk-to-benefit ratio of TAVI should be validated individually. In the present study, octogenarians with logistic EuroScore <20% could be identified as candidates apparently gaining high benefit from the procedure.

Intrathoracic fire during preparation of the left internal thoracic artery for coronary artery bypass grafting.

A surgical fire is a serious complication not previously described in the literature with regard to the thoracic cavity. We report a case in which an intrathoracic fire developed following an air leak combined with high pressure oxygen ventilation in a patient with severe chronic obstructive pulmonary disease. The patient presented to our institution with diffuse coronary artery disease and angina pectoris. He was treated with coronary artery bypass graft surgery, including left internal thoracic artery harvesting. Additionally to this rare presentation of an intrathoracic fire, a brief review of surgical fires is included to this paper.

Comparison of continuous cardiac output measurements in patients after cardiac surgery.

OBJECTIVE: To investigate in a direct comparison accuracy and precision of continuous cardiac output measurements assessed by continuous pulmonary artery thermodilution technique (TDCCO), continuous pulse contour analysis (PCCO), and noninvasive partial CO(2)-rebreathing technique (NICO) in patients after coronary artery bypass grafting (CABG) during the postoperative period. DESIGN: Prospective, controlled clinical study. SETTING: University hospital. PARTICIPANTS: Twenty-two patients undergoing elective CABG surgery. INTERVENTIONS: Hemodynamic measurements were performed after admission to the ICU and in sequence every 2 hours during the subsequent 6-hour period. Simultaneously, cardiac output (CO) was measured using a TDCCO, PCCO, and NICO. After the continuous cardiac output measurements were read, bolus thermodilution-derived cardiac output was obtained from thermodilution curves detected in the pulmonary artery (TDBCO(pa)). Four intermittent consecutive boli consisting of 10 mL of ice-cold saline were randomly injected over the ventilatory cycle. MEASUREMENTS AND MAIN RESULTS: The comparison between the continuous cardiac output measurement methods TDCCO versus PCCO showed a bias of -0.12 L/min, between TDCCO versus NICO -0.17 L/min, and between PCCO versus NICO -0.44 L/min. The comparison to the reference technique between TDBCO(pa) versus TDCCO revealed a bias of -0.28 L/min, between TDBCO(pa) versus PCCO -0.40 L/min, and between TDBCO(pa) versus NICO -0.64 L/min. CONCLUSIONS: The results of this clinical investigation show agreement between TDCCO and PCCO to satisfy clinical requirements in a setting of postoperative patients after cardiac surgery. In contrast, the NICO monitor is of very limited use in these patients.