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Failure to monitor warfarin levels


A 70-year-old woman with a history of diabetes, hypercholesterolemia, and hypertension was taken to Hospital A, due to severe aortic stenosis. The patient was admitted, and Cardiothoracic Surgeon A successfully performed an aortic valve replacement. 

The patient was provided a warfarin prescription and discharged from the hospital two days later. Follow-up instructions included making an appointment with her primary care physician in one week, and to follow up with the surgeon in one to two weeks. Detailed instructions and information about warfarin were also provided to the patient.


Physician action

The patient scheduled her follow-up appointment with Primary Care Physician A in two weeks, rather than one week as instructed. Eleven days after discharge from the hospital, the patient came to the physician as a walk-in patient reporting nausea, vomiting, constipation, clammy skin, diarrhea, and lightheadedness. A physician assistant (PA) supervised by Primary Care Physician B saw the patient.

The patient told the PA about her recent surgery and her scheduled follow-up appointment with the surgeon in two weeks. The PA reconciled the medication list, but failed to include warfarin. The patient was diagnosed with viral gastroenteritis and no labs were ordered.

The next day, the patient went to Hospital B’s emergency department (ED) at 12:46 p.m. She reported shortness of breath, nausea, vomiting, and weakness. Medications listed on the history and physical form included warfarin 5 mg. 

Labs were completed and showed an INR of greater than 10. (The most common INR target range is between 2.0 and 4.0.) The emergency physician informed Cardiothoracic Surgeon A of the patient’s condition at 2:36 p.m. After waiting more than three hours with no response from Cardiothoracic Surgeon A, the emergency physician asked Cardiothoracic Surgeon B for a consult. The patient was given Vitamin K to decrease the warfarin effects and transferred to the ICU at 7:34 p.m.

ICU admission notes state that the patient reported “3 days of shortness of breath that has gotten progressively worse from mild exertion to minimal exertion and having shortness of breath even at rest.”

The ICU physician noted that the patient was developing bruising on the right side of her chest sustained from a fall two days before. She was constipated and using stool softener, which gave her diarrhea. Vital signs were heart rate 98-105 bpm, respirations 16, blood pressure 97/62 to 128/74 mm Hg and O2 saturations at 98%. 

The assessment was as follows: “suspect pneumonpericardium considering pericardial effusion with supratherapeutic INR; no evidence of overt cardiac tamponade since the patient’s vital signs normal; rule out acute coronary syndrome; shortness of breath; reverse INR; renal failure on chronic kidney disease unknown baseline.”

While in the ICU, a pulmonary consult, a cardiology consult, and a renal consult were obtained. The cardiology’s assessment was pericardial effusion with early evidence of tamponade, with the recommendation that the patient undergo urgent pericardiocentesis or pericardial window. Documentation included plans to contact Cardiothoracic Surgeon A to discuss the case and obtain recommendations about a pericardiocentesis versus pericardial window.

Earlier in the afternoon, a nurse documented that she spoke to Cardiothoracic Surgeon A’s nurse and was told he was in surgery and would call back. At 7:24 p.m., the nurse noted that Cardiothoracic Surgeon A had not called back.

At 10:30 p.m., the patient reported difficulty breathing. The cardiologist was notified, and the patient was transferred to the catheterization lab at 12:03 a.m. Pericardiocentesis was attempted, but was unsuccessful. The patient died at 2:01 a.m.



The patient’s daughter filed a lawsuit against the PA who worked with Primary Care Physician B. The allegations included failure to perform the necessary blood work to monitor the patient’s warfarin level, which led to her death. The plaintiff also filed lawsuits against Primary Care Physician B and the medical practice for failure to appropriately supervise the PA.


Legal implications

Defense consultants were critical of the care provided to this patient. One consultant stated that the PA should have sent the patient to the ED at Hospital A. Staff there would have been familiar with her care and her recent procedure. A second consultant stated the patient should have scheduled follow-up INR testing, but that the health care professionals in the case did not know who was to conduct testing for the patient.



This case against the PA was settled. Primary Care Physician B and the practice also contributed to the settlement.


Risk management considerations

Medication reconciliation should be documented in the patient’s record to avoid the hazard of poly-pharmacy and adverse drug interactions. Medications should be reviewed at each visit to monitor compliance and help prevent adverse interactions. In this case, an incomplete reconciliation resulted in a drug-induced illness.

When employing an advanced practice provider, it is important to have written protocols regarding responsibilities, scope of practice, and standing delegation orders. The plaintiffs’ expert opined that a physician, instead of a PA, should have seen the patient at the first post-surgical appointment.

There were many providers involved with caring for this patient, yet there was no clear follow-up plan for sharing and tracking test results. Continuity of care includes having a consistent process to track referrals and lab or diagnostic tests. Additionally, if the patient does not make or keep an appointment, documentation regarding efforts to contact the patient should be noted.