this was a retrospective cohort study approved by our institutional review board as a quality improvement research . the records of catheter days 1 year before the introduction of midlines ( group a : august 1 , 2011 , to july 31 , 2012 ) and catheter days of 1 year after the regular use of midlines ( group b : november 1 , 2012 , to october 31 , 2013 ) in the ventilator unit were collected ( table 1 ) . during the period from august 2012 to november 2012 , internal medicine residents and nursing staff underwent training on the use and insertion of midline catheters and their care . this dedicated team was responsible for replacing cvcs by midlines as per our new practices . the midlines that we used were powerwand ( access scientific , san diego , calif ) . before midline catheter , patient days : number of days the patient was in the ventilator unit ; catheter days : number of days the patient had a central venous catheter and after midline catheter , patient days : number of days the patient was in the ventilator unit ; catheter days : number of days the patient had a midline catheter we chose this unit because it has a constant denominator of the number and type of patients . most of the patients in this unit are ventilator dependent and being treated for problems such as health care  associated pneumonia , urinary tract infections , wound and pressure ulcer infections , or other long - term conditions requiring acute care that can not be administered at a nursing home facility . the patients here have longer length of stay compared with other units and generally have difficult venous access . the most common reason for cvc use in this unit is for difficult and long - term intravenous access . indications of cvcs in these patients included antibiotic therapy , infusion therapy , diagnostic procedures , transfusions , and blood draws . the department of infection control of the hospital reports all the clabsi per 1000 catheter days in the hospital , categorized by location and unit . the number of clabsi during this period along with the type of bacteria and the date of culture was obtained from the microbiology department . we compared the clabsi rates between group a and group b to see whether it decreased through the use of midlines in comparison with central lines . we trained a team of residents for a period of 3 months in the insertion of ultrasound - guided midline catheters , which would replace cvcs by midline catheters whenever possible . the same antiseptic precautions used in cvc catheter placements under ultrasound guidance were applied to the placement of midlines . the policy for replacing the central lines included the following guidelines : any patient with a cvc in a femoral vein had their line removed and replaced by a midline catheter . all patients who were not on an ionotropic agent or total parenteral nutrition had their cvc replaced by midlines . a midline catheter replaced any cvc in place longer than a week . a patient on antibiotic therapy being sent to nursing home for further management received a midline catheter . the total number of catheter days was compared with the rate of clabsi in the 2 groups . catheter days were calculated as the number of central line catheters on the unit every day . adding the total number of catheters on the unit per day and adding this daily number for the length of time of the study help calculate catheter days . central line  associated bsi was reported as rate per 1000 catheter days and can be calculated as follows : ( total number of clabsi / total number of catheter days )  1000 . we used a  test to compare the number of catheter days per patient days in the 2 groups as well as to compare infections based on the number of catheter days in each group ( table 2 ) . comparing the number of catheter days per patient days in the 2 groups , as well as comparing infections based on the number of catheter days in each group there was a significant decrease in the total number of catheter days on the ventilator unit in group a from 2408 catheter days in the 1 year ( august 1 , 2011 , to july 31 , 2012 ) before the introduction of midline catheters to 1521 catheter days in group b in the following year ( november 1 , 2012 , to october 31 , 2013 ; p < 0.05 in both groups ) . the total number of clabsi infections in these periods was also significantly decreased from 8 to 0 ( table 3 ) . this calculates to 3.32 clabsi per 1000 catheter days and 0 clabsi per 1000 catheter days , respectively ( add  ) . the number of inpatient days during these periods was 3058 and 2948 days ( table 4 and 5 ) . continuation of the  test  test : observed frequency  test : expected ( theoretical ) frequency , asserted by the null hypothesis there were no bsis associated with midlines in this study . the centers for disease control and prevention has put in place guidelines to reduce the incidence of clabsi . these guidelines brought about by numerous studies for years have helped bring down the rate of clabsi . these measures include the following : reducing the number of dwell days by removing catheters as early as possible ; reducing the use of central lines by using other means of venous access ; proper care and technique for cvcs ; maximum sterile barrier precautions during insertion ; use of chlorhexidine for skin disinfection before catheter insertion ; avoidance of the femoral insertion site ; and use of recommended insertion site dressing care practices . prolonged dwell time has been shown to increase clabsi rates rapidly after 9 catheter days . replacing central lines with midlines decreases the dwell time and also the total number of catheter days . it may be argued that the decrease in the use of central lines and thereby reducing the number may be responsible in decreasing clabsi ; however , our denominator is constant for comparison . the use of midlines reduces the use of and the dwell days for central lines , and with this study , we show that it can be a factor in reducing clabsi as well . another study showed that clabsi rates were higher in patients who had central lines for longer than 7 days . in our study , by replacing central lines with midlines in patients , we essentially decreased risk factors such as dressing changes , catheter care , and duration of central line use . a more obvious outcome is the decrease in use of central lines itself , causing a drop in the infection rates . the fall in infection rate may be attributed to the fewer number of catheters in place for longer than 7 days . before the introduction of midlines , difficult intravenous access in these chronically ill patients mandated the use of central lines . there are other complications of central lines , including inadvertent arterial puncture ( 3% ) , hemothorax , or pneumothorax ( 1%-2% ) . central lines and picc lines require x - ray confirmation of tip placement , exposing the patient to radiation . midlines have complications as well ; our most common problem was the loss or malfunction of the midline including extravasations in 2 patients . the bsi rate of midlines in various studies has been reported to be between 0% and 0.9% . the combination of better available products and the increasing use of ultrasound guidance for intravenous catheter placement has renewed interest in midline catheters . some limitations of midline catheters are inability to use for vasopressors , total parenteral nutrition or when large peripheral veins are not available such as in amputates and patients with arteriovenous fistulas . we conclude that the use of midline catheters to replace central lines for difficult intravenous access decreases the rate of clabsi in a ventilator unit in a community hospital .
hypothesisour objective was to evaluate whether the use of midline venous catheters in place of central line venous catheters , when appropriate , decreased the overall incidence of central line  associated bacteremia in a ventilator unit.methodsthe time interval between february 2012 and february 2013 was divided into 2 periods . 
 group a was the first half of the year , before the introduction of midline catheters , and group b was the second half of the year , 6 months after their introduction . 
 central line  associated bloodstream infection ( clabsi ) was calculated using the equation : ( total number of clabsi / total number of catheter days )  1000 . 
 the z test was used for proportions between independent groups to compare the significance in the difference in clabsi between groups a and b.resultsthere was a significant decrease in the total number of catheter days on the ventilator unit in group a from 2408 catheter days in 1 year ( august 1 , 2011 , to july 31 , 2012 ) before the introduction of midline catheters to 1521 catheter days in group b in the following year ( november 1 , 2012 , to october 31 , 2013 ; p < 0.05 for both groups).conclusionsmidline catheters in place of central lines decrease the rate of clabsi in a ventilator unit . 
 in addition , no bloodstream infections were associated with midline catheters .