We report a successful ultrasound-guided transversus abdominis plane (TAP) block as an analgesic option for minor abdominal surgery in a 66-year-old patient with cardiac, respiratory, and renal dysfunction caused by primary systemic amyloidosis. Bilateral TAP blocks with 120 mg (1.8 mg/kg) of ropivacaine provided sufficient intra- and postoperative analgesia for insertion of a continuous ambulatory peritoneal dialysis catheter. However, the plasma concentration of ropivacaine reached a maximum of 2.5 µg/mL at 15 minutes after the TAP block, a concentration that was potentially neurotoxic. Although apparent signs of local anesthetic systemic toxicity (LAST) such as convulsion or changes in an electrocardiogram were not observed, the patient became drowsy after the TAP block, which might be one of the mild symptoms of LAST. A TAP block by itself can thus be an anesthetic option for patients undergoing minor abdominal surgery. However, cardiac and renal dysfunction might influence the pharmacokinetics of a local anesthetic used, and attention should be paid to the possibility of LAST even with a low dose of a local anesthetic for patients with cardiac and renal failure.