Cefazolin and rifampin: A coagulopathy-inducing combination

Infective Endocarditis Complicated by Iatrogenic Intracranial Hemorrhage Secondary to Cefazolin-Induced Coagulopathy

Infective endocarditis can be acute or subacute. It can be caused by viral, bacterial, fungal, and sometimes nonbacterial etiologies. It is an important cause of mortality and morbidity in children as well as adolescents, despite advances in management. A 59-year-old male with a past medical history of aortic valve (AV) replacement on warfarin presented to the Emergency Department with dull right flank pain and poor dentition on examination. Computerized tomography (CT) scans of the abdomen revealed the presence of splenic and renal infarcts. Warfarin was held after the international normalized ratio (INR) was noted to be elevated at 11. Following the activation of the sepsis bundle in the ER, he received intravenous fluids (30 cc/kg) and was started on vancomycin and ceftriaxone. On further evaluation, the transesophageal echocardiogram revealed mobile densities on the aortic surface concerning vegetation. Antibiotics were transitioned to cefazolin, gentamycin, and rifampin for the management of prosthetic valve endocarditis. The patient's INR improved to 3.5 on the third day of hospitalization, and heparin was initiated to maintain anticoagulation for the prosthetic valve. However, on the eighth day of hospitalization, the patient developed left-sided weakness and slurred speech. The CT head showed acute frontoparietal intracranial hemorrhage (ICH), with an INR noted to be 5. Heparin was reversed with protamine sulfate, and vitamin K was administered, following which the INR improved to 2.3. The patient was transferred to intensive care, but on the second day of the ICU stay, the INR again shot up to 6 with normal LFTS. The patient received vitamin K, but the INR only improved to 5. Subsequently, antibiotics were changed from cefazolin to nafcillin. INR thus fell to 1.6 in two days after changing the antibiotics. The patient was soon transferred to a higher center for aortic valve replacement. While few case reports have described severe coagulopathy induced by cefazolin, it is particularly seen with impaired renal function; however, our patient's renal function was completely normal. Coagulopathy is due to the drug's effect on intestinal flora and its structural methyl-thiadiazole side chain, which has similar effects as epoxide reductase inhibitors and results in INR elevation. Patients on cefazolin need to be closely monitored for INR levels every day, as there is a high likelihood of developing complications like ICH, as noted in this patient. While the monitoring of cefazolin levels is not necessarily indicated, it is necessary to place patients on fall precautions and monitor INR levels every day, as mentioned above.