A syringe pump is used to inject precise doses of drugs having a strong action; for example, vasoactive drugs. Unexpected and undetected halt of a syringe pump can lead to potentially life-threatening complications. We experienced a sudden halt in the movement of a syringe pump (Terufusion syringe pump; Terumo, Tokyo, Japan) in two patients while administering norepinephrine in the intensive care unit (ICU). Fortunately, the patients had only transient hypotension, which was immediately detected and promptly treated, without any untoward sequelae. As a result of the occurrence of such cases, we conducted a detailed investigation of the causes of this sudden halt in the syringe pump. We could not reproduce the aberration of the syringe pump and thus could not specify the cause in the first patient. In the second patient, however, a false setting on the syringe was suspected to be the cause of the problem. In order to prove this, we tried to reproduce the situation where a syringe pump, due to a false syringe setting, abruptly terminated while giving a “syringe loss” warning, after a period of precise functioning. Once we had determined how a false setting of the syringe could occur without the syringe pump giving off an alarm from the onset, we collaborated with the Terumo Company to revise their current instruction manual to incorporate this as a warning. We also helped in the development of a new model, including a new safety feature that would prevent a false setting of the syringe from occurring at all. This new model was released in December 2003.