Impact on blood loss and transfusion rates following administration of tranexamic acid in major oncological abdominal and pelvic surgery: A systematic review and meta-analysis.

BACKGROUND AND OBJECTIVES: Major bleeding and receiving blood products in cancer surgery are associated with increased postoperative complications and worse outcomes. Tranexamic acid (TXA) reduces blood loss and improves outcomes in various surgical specialities. We performed a systematic review and meta-analysis to investigate TXA use on blood loss in elective abdominal and pelvic cancer surgery. METHODS: A literature search was performed for studies comparing intravenous TXA versus placebo/no TXA in patients undergoing major elective abdominal or pelvic cancer surgery. RESULTS: Twelve articles met the inclusion criteria, consisting of 723 patients who received TXA and 659 controls. Patients receiving TXA were less likely to receive a red blood cell (RBC) transfusion (p < 0.001, OR 0.4 95% CI [0.25, 0.63]) and experienced less blood loss (p < 0.001, MD -197.8 ml, 95% CI [-275.69, -119.84]). The TXA group experienced a smaller reduction in haemoglobin (p = 0.001, MD -0.45 mmol/L, 95% CI [-0.73, -0.18]). There was no difference in venous thromboembolism (VTE) rates (p = 0.95, OR 0.98, 95% CI [0.46, 2.08]). CONCLUSIONS: TXA use reduced blood loss and RBC transfusion requirements perioperatively, with no significant increased risk of VTE. However, further studies are required to assess its benefit for cancer surgery in some sub-specialities.

Comparison of freehand 3-D ultrasound calibration techniques using a stylus.

In a freehand 3-D ultrasound system, a probe calibration is required to find the rigid body transformation from the corner of the B-scan to the electrical center of the position sensor. The most intuitive way to perform such a calibration is by locating fiducial points in the scan plane directly with a stylus. The main problem of this approach is the difficulty in aligning the tip of the stylus with the scan plane. The thick beamwidth makes the tip of the stylus visible in the B-scan, even if the tip is not exactly at the elevational center of the scan plane. We present a novel stylus and phantom that simplify the alignment process for more accurate probe calibration. We also compare our calibration techniques with a range of styli. We show that our stylus and cone phantom are both simple in design and can achieve a point reconstruction accuracy of 2.2 mm and 1.8 mm, respectively, an improvement from 3.2 mm and 3.6 mm with the sharp and spherical stylus. The performance of our cone stylus and phantom lie between the state-of-the-art Z-phantom and Cambridge phantom, where accuracies of 2.5 mm and 1.7 mm are achieved.

A mechanical instrument for 3D ultrasound probe calibration.

We present a novel technique for 3D ultrasound probe calibration. The principle of operation is that the beam is aligned with a set of coplanar wires strung across a rigid frame. The probe and frame are mounted on a precision-manufactured mechanical instrument which allows adjustment and measurement of their relative pose. Semi-automatic image processing facilitates alignment of the beam and wires to within a tolerance of around 0.2 mm, despite the considerable beam thickness. The calibration process requires just a single view and relatively little user expertise. In a series of experiments with different ultrasound probes, we demonstrate the technique's high accuracy and precision. The latter is partly due to the elimination of the position sensor, a significant source of measurement noise, from the end-user calibration process.