Cardiopulmonary bypass surgery is associated with extensive blood loss in upto 20% of patients. Tranexamic acid (TXA) is a routinely administered antifibrinolytic agent that reduces blood loss and blood transfusion requirement. However, standard dosing of TXA in patients suffering from renal dysfunction and undergoing cardiopulmonary bypass surgery may lead to higher blood concentration of TXA when compared to the patients with normal renal function. Solid phase microextraction (SPME) is a fast and simple method to measure TXA levels. This prospective study on cadiac surgical patients undergoing cardiopulmonary bypass aims to study the pharmacokinetics of TXA in patients with renal dysfunction. Two patient groups will be studied who will receive either TXA 50mg/kg bolus or BART regimen (30 mg/kg, 16 mg/kg/h + 2 mg/kg pump prime) depending on the type of cardiac surgical procedure and bleeding risk.

Hypothesis: Standard dosing of TXA used in cardiac surgery result in higher blood concentration of TXA in patients with renal dysfunction when compared to patients with normal renal function.

Inclusion Criteria:

• Cardiac surgical patients above 18 years of age with renal dysfunction (stage 1, 2 ,3, 4 and 5 of the Kidney Disease Outcome Quality - Initiative classification of chronic kidney disease)

Exclusion Criteria:

• All patients under 18 years of age or unable to give consent
• Documented drug allergy to tranexamic acid
• Deep hypothermic circulatory arrest
• Pre-existing coagulopathy
• Pregnancy
• Advanced liver disease
• Renal transplant recipients
• Concomitant treatment with contraceptives, tretinonin

Cardiac surgical patients with chronic renal dysfunction