An observational study to assess coagulation abnormalities in patients with elevated levels of urea and/or creatinine secondary to renal failure, presenting for renal biopsy – challenging conventional testing using visco-elastic testing

Rodrigues, Jacques

An observational study to assess coagulation abnormalities in patients with elevated levels of urea and/or creatinine secondary to renal failure, presenting for renal biopsy – challenging conventional testing using visco-elastic testing

Master Thesis

2018

Abstract

Introduction Coagulation abnormalities are well described in patients with elevated levels of urea and/or creatinine secondary to renal failure. These range from hypercoagulable to hypocoagulable states due to a range of mechanisms well described in the literature. Conventional tests of coagulation such as INR and PTT do not adequately assess these disorders of coagulation. Thromboelastography (TEG®) has proven to be a suitable alternative test of coagulation that serves as a dynamic test of global coagulation including assessment of thrombus formation as well as its breakdown. TEG® and ROTEM® assesses the visco-elastic properties of blood in vitro to define in vivo coagulability. The standard of care in our institution to assess the bleeding risk in patients with renal failure (defined by a raised urea and/or creatinine level) presenting for a renal biopsy is to use the conventional tests of coagulation, including a bleeding time if their creatinine is above 300 µmol/L. The aim of this study is to evaluate the conventional standard laboratory tests of coagulation (including a bleeding time where available), TEG® and ROTEM® in assessing coagulation disorders in patients with elevated levels of urea and/or creatinine presenting for renal biopsy. Methodology Patients with elevated levels of urea and/or creatinine presenting for a renal biopsy will be identified by the nephrology team responsible for their medical management. Prior to the renal biopsy, these patients will be approached by the study team and reviewed for inclusion into the study. Informed consent will be obtained on agreement to participate in the study. We will collect a blood sample for the TEG® and ROTEM® and this test will be performed by a laboratory technician in the Department of Anaesthesia. The clinician/nephrologist performing the biopsy will not be influenced by the outcome of these viscoelastic tests. A convenience sample of a minimum of 25 patients with renal impairment presenting for a renal biopsy will be included in this study. Results A total of 44 adult participants was entered into this observational study. Results for 1 participant were excluded from this study as their biopsy was delayed, allowing their renal function to improve and return to normal with medical management on the day that they presented for a renal biopsy. 43 patients were worked up for a renal biopsy but only 38 patients proceeded to a renal biopsy. Of these, only 31 patients had a bleeding time performed on the day of their renal biopsy. The participants ages ranged from 24 to 69 years and included 24 male and 19 female participants. Renal biopsies were cancelled by the consultant nephrologist in 5 patients on the day of their biopsy. Control samples, from 10 members in the Department of Anaesthesia, fell within the specified range of the various manufacturers. An interesting TEG® result was an average MA result of 74.22 mm (normal range 64 – 72 mm), which lies above the upper limit of normal. Two patients developed a small renal haematoma on ultrasound after the biopsy, with 1 of these patients also developing haematuria. Conclusion TEG® and ROTEM® provides a global assessment of coagulation and might be helpful in assessing coagulation defects in patients with elevated levels of urea and/or creatinine presenting for a renal biopsy, with possible extension to the surgical patient with abnormal renal function presenting for a surgical procedure to assess their risk of bleeding, especially in those who are being considered for a regional or neuraxial technique - as this could be an unacceptable risk in this population sub-group .

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