Determination of concentration of ropivacaine in venous blood in prolonged analgesia of postoperative wound
Aim. Determinations of concentrations of total ropivacaine in venous blood with use of the selected scheme of prolonged analgesia of the postoperative wound after cesarean operation. Materials and Methods. The study involved 47 female patients after cesarean operation in whom during suturing of the laparotomy wound a multiperforated catheter was installed under aponeurosis of the abdominal muscles for a prolonged postoperative analgesia. With use of infusion pump, 0.2% ropivacaine solution was introduced at constant speed 4 ml/h with the total amount 200.0 ml. Blood was taken by puncture of the peripheral vein in control points in 30 min, 24 hours and 48 hours after the start of injection of the solution. The quantitative determination of the concentration of the total ropivacaine of venous blood plasma (free and bound with plasma proteins) was conducted using gas chromatograph with mass-selective detector. Results. The highest concentrations of the total ropivacaine of venous blood were recorded in 48 hours Me (Q1; Q3)=0.053 (0.043; 0.071) which was significantly lower than minimal potentially toxic concentrations. Also not a single case of appearance of clinical signs of systemic toxicity of local anesthetics was recorded. No statistically reliable correlation was found between body mass, height, body mass index and concentration of total ropivacaine in blood. Conclusion. The given study permitted to confirm safety of the selected scheme of introduction of the solution of local anesthetic, since no potentially toxic concentrations of the total ropivacaine were reached in venous blood in a single patient included into the study.