A device and method for determining intravascular pressure and irregular needle placement in a hemodialysis procedure include analyzing means for automatically deriving venous access pressure (VAP) at a location of venous needle insertion into the patient and determining a ratio of VAP to mean arterial pressure, where the analyzing means determines multiple VAP values over multiple time periods and determines multiple ratios, one for each VAP value. Detecting means compare each ratio to a predetermined standard ratio derived from a moving average of prior VAP ratios, where the detecting means detects irregular needle placement when elevation of the ratio above the standard ratio is indicated.