Indwelling Devices in ICU Patients and a Revised Method for Calculating Central Line-Associated Bloodstream Infection Rates Based on Total Number of Central Venous Catheters

Background: Invasive devices are common in ICU patients and use of these devices is associated with infection risk. Current methods for calculation of catheter days do not take into account the presence of more than one central venous catheter (CVC).

Objective: To evaluate the frequency of invasive devices in an ICU population and determine if adjusting for the presence of multiple CVC altered the rate of CLA-BSI.

Methods: Manual device counts were obtained weekdays over the course of one month in two ICU’s including a 19-bed med/surg ICU (Unit 1) and a 12-bed cardiothoracic ICU (Unit 2).  Patients were identified using an electronic report of patients with an invasive device present.  Assessment for the presence of catheters (CVC, peripheral IV (PIV), arterial catheter (AC), urinary catheter (UC)), endotracheal tubes, and tracheostomies was performed.  Rates of CLA-BSI in the units were monitored and defined using NHSN definitions. Estimated rates of CLA-BSI were calculated using line days based on actual number of CVC’s present (2 CVC’s present for one day in a single patient=2 CVC days) and the baseline rate from 7/09 to 6/10.

Results: A total of 1352 devices were observed over a total of 425 patient days.  All patients had at least one invasive device and averaged 3.2 (±1.23) devices/patient day with up to 7 devices present.  The most common devices present were CVCs and UCs with mean rates of 0.98 (±0.59) and 0.71 (±0.45) per patient day respectively.  On average, each patient had 2.8 catheters in place per day and a total of 1096 catheters were observed.  When intravascular catheters were considered (CVC, AC, PIV) 794 were present with an average of 1.87 per patient day.  CVC catheters were present on 82% (347/425) of patient days with 19.1% of CVC days having 2 or more CVC’s present (64 with 2 CVC’s, 2 with 3 CVC’s).  NHSN CVC patient days were 347.  Counting each individual CVC as a day resulted in an increase of 68 days or 1.196 times more CVC days.  CLA-BSI in Unit 1 and 2 during the year preceding were 2.36 and 1.65 respectively with a combined rate of 2.1 infections/1000 patient days.  Denominator data was estimated using the correction factor of 1.196 and over the previous year CLA-BSI rates in Unit 1, Unit 2, and combined decreased to 2.0, 1.4, and 1.7 CLA-BSI/1000 CVC days respectively.

Conclusions: The prevalence of invasive devices and catheters in the ICU is high with intravascular catheters being most common.  A significant number of patients have more than one CVC and recalculation of rates based upon the number of lines present would result in an approximately 20% decrease in CLA-BSI rates in the ICU.