INFLUENCE OF HYDROSTATIC-PRESSURE ON CONT INUOUS APPLICATION OF CARDIOVASCULAR DRUGS WITH SYRINGE PUMPS

Administration of highly concentrated, highly potent, and therefore hi ghly dangerous drugs with syringe pumps is common in modern anaesthesi a as well as in intensive care and emergency medicine. Because of thei r exact flow rates down to <1 ml/h, these pumps are predestined for de livery of drugs with short half-lives, such as catecholamines and vaso dilators. But intravenous application of drugs with syringe pumps is n ot without problems. While it is well known that syringes not fixed co rrectly into the pump can empty themselves by the influence of gravity , it seems not to be known that hydrostatic pressure can influence the flow rate of a correctly connected system even during continuous infu sion. In this situation a change of height of the syringe pump in rela tion to the patient's position can have tremedous effects on hemodynam ics due to unintended acceleration or deceleration of the flow rate. T his case report demonstrates that the elevation of a connected epineph rine pump while moving a cardiac surgery patient after ACB operation f rom the operation table into his bed led to critical increases of hear t rate, blood pressure and left atrial pressure. In order to quantify the problem we repeated the situation experimentally. It could be demo nstrated that the elevation of the syringe pump by 80-100 cm delivers an additional bolus of 4-5 drops as the central venous catheter outlet . Lowering the pump consecutively leads to the opposite effect. In the case reported, the accidentally administered bolus of epinephrine was 12-15 mu g (we use a concentration of 60 mu g/ml epinephrine for cont inuous infusion with syringe pumps). From this accidental observation the following conclusion can be drawn: The change of height, in relati on to the patient's position, of a running syringe pump during continu ous infusion of highly concentrated cardiovascular drugs may cause con siderable, even life-threatening hemodynamic disorders. Even in a clos ed infusion system (syringe-extension-central venous catheter), hydros tatic pressure influences infusion rate. Elevation of the pump leads t o unintended bolus administration, and lowering of the pump is followe d by an interruption of the infusion. In the knowledge of this phenome non, unexpected hemodynamic reactions during transport of critically i ll patients cannot always be interpreted as a result of inadequate ane sthesia or volume load, but may be a consequence of incorrect handling of the syringe pumps as described in this report.