We report a case in which a radial arterial line was placed prior to induction of general anaesthesia in a 76 year old male with prostate cancer and multiple co-morbidities who presented for thoracoscopic resection of a right lower lobe carcinoid lung tumor. The patient's intra-operative course was complicated by acute blood loss requiring conversion to an open procedure. A subsequent injury to the superior vena cava resulted in the need for immediate re-exploration at the conclusion of surgery. While the arterial line was still indicated in this patient's postoperative course in the ICU, malfunction on post-operative day one resulted in removal of the catheter. The catheter was secured by stay sutures and during the attempt to cut these sutures, the arterial catheter was inadvertently severed and a fragment remained within the patient's radial artery. Surgical intervention was required to remove the retained catheter and the patient recovered without evidence of residual injury or deficit to the artery and extremity. Literature review reveals only one other case report of a retained catheter in a radial artery caused by accidental transection during removal. We review indications for arterial line placement, complications, as well as methods for securing arterial catheters.