A patient care system (90) comprising an interface unit (100), an infusion pump unit (150a), and a capnography unit (150b) is disclosed. The infusion pump unit (150a) is used to administer medical fluids to a patient, including the administration of anesthetics, analgesics, or sedatives. The capnography unit (150b) provides monitoring of the patient's expired air, in particular, the end tidal CO 2 levels in the expired air and the respiration rate. When the capnography unit (150b) indicates to the interface unit that the end tidal CO 2 level and/or pulse rate has reached a point outside a specified range, the interface unit (100) initiates visual and audio alarms and controls the infusion pump unit (150a) by modifying the flow or by shutting off the pump unit. In patient controlled analgesia applications, the interface unit (100) may block patient-controlled bolus doses of the analgesic until reset by a qualified medical professional or until the measured capnography values return to a normal range. The interface unit (100) also contains communication ports, which the interface unit can use to send signals to external devices, such as to alert medical personnel.