THERAPY/PREVENTION

Criteria abstracted from The Users' Guides to the Medical Literature series in JAMA

Crit Care Med 2009 Mar;37(3):1090-6..[abstract]

Review posted May 24, 2010

1. What is being studied?

   The study objective:

   To determine whether ultrasound (US) increases successful central venous catheter (CVC) placement, decreases site attempts, and decreases CVC placement complications compared to CVC placement using a landmark (LM) technique.         

   The study design:

   A single site, prospective observational cohort study.

   The patients included:

   Medical and surgical patients were prospectively enrolled into the landmark group (N=93) and then after training on new equipment, patients were enrolled into the ultrasound group (N=119).  Patients were included into the study if they required placement of a CVC while in the PICU.

   Patients excluded:

   Patients excluded from the study were those who had catheters placed outside of the PICU or those placed by non-critical care services.

   The interventions compared:

   Data was collected from the prospective landmark group prior to training of personnel with the ultrasound guided technique.  The CVCs were then placed using the ultrasound technique.

   The outcomes evaluated:

   The primary outcomes evaluated were; successful catheter placement, time to successful placement of catheter, number of attempts to place catheters, and number of inadvertent arterial punctures.

2. Are the results of the study valid?
   
   

   Primary questions:

   1. Was the assignment of patients to treatments randomized?

      No, the patients were prospectively enrolled into a landmark study group and an ultrasound guided group in a “before-after� study design.

   2. Were all of the patients who entered the trial properly accounted for and attributed at its conclusion?

      Yes.  Results for all specified outcome measures were reported.  Outcomes included whether US increased successful CVC placement, if US decreased the number of site attempts, and whether or not US decreased CVC placement complications as compared to the LM technique of CVC placement.

      Was followup complete?

      Yes.  Outcomes (rate of placement success, number of attempts until success or failure, complications including successes and failures, and time to wire in patients where CVC placement was successful) were reported for all patients in the LM and US groups. 

      Secondary questions:

   3. Were patients, health workers, and study personnel "blind" to treatment?

      No.  The study design is an observational cohort.  Bias is potentially introduced due to the method of which the LM placed CVC were monitored.  The LM CVC placement was timed with a stop watch and determined to be successful when the guidewire was inserted.  A similar timing study was not performed with the US guided CVCs placed to include the organization and set up of the ultrasound machine prior to CVC placement.

   4. Were the groups similar at the start of the trial?

      Yes.  There were not statistically significant differences between the LM and US groups for age, weight, primary disease processes, use of sedation and ventilation, neuromuscular blockade, vasoactive infusions, and history of CVC placement (whether difficult or emergent placement).  Comparison of the emergently placed CVC showed a higher number in the LM group (29.4) vs the US group 17.7%.  The authors mentioned that the LM artery puncture rates were greater than in other studies and attributed it to the higher number of emergent CVC placed via LM technique.

   5. Aside from the experimental intervention, were the groups treated equally?

      Not known, but not relevant.  CVC placement by the traditional landmark procedure group was conducted first.  Operator training level, disease process, circumstances of CVC placement (emergent vs routine), anatomical sites attempted, and complications were assessed.  The operators for the LM group included residents, fellows, attendings, and nurse practitioners.  The data was collected for the LM group and the initial portion of the study was closed prior to proceeding to the ultrasound group study.  The ultrasound group portion of the study was initiated after the operators were instructed in use of the ultrasound.  The operators included in the ultrasound group consisted of fellows, attendings, and nurse practitioners.  The factors recorded in the ultrasound CVC placement were the number of previous CVCs placed with the ultrasound per practitioner, the practitioners comfort with the ultrasound, and the opinion of the practitioner on the utility of the ultrasound. How the patients were being treated for their underlying diseases may have differed between the two groups but is not likely to be relevant for the purposes of this investigation.

3. What were the results?
   
   
   1. How large was the treatment effect?
      1. CVC Success:  There were no statistically significant differences in success rates between the LM (88.2%) and US (90.8%). (p = 0.54) 
      2. Site Attempts:  The study demonstrated a statistically significant decrease in the median number of all CVC attempts with the use of US from 3 to 1.  (p < 0.001)
      3. Complications: Decreased arterial puncture with the US technique was the only statistically significant change in complication rate. Overall, the arterial puncture rate in the LM group was 19.4% and 8.5% in the US group (table 2). The OR of arterial puncture in the US vs. LM group was 0.39 (p = 0.03)
      4. Time to successful CVC placement:  No statistically significant difference was noted between techniques. (p = 0.14)
      5. Also mentioned, a significant number of IJ catheters were placed using the US technique (16) as opposed to only 2 IJ catheters placed using the LM technique.  The authors did not evaluate whether the increased number of inadvertent arterial punctures were likely due to the anatomic site chosen for CVC placement, however, did comment that there were less attempts made with use of the US technique. 
         
         
   2. How precise was the estimate of the treatment effect?

      Confidence intervals were not published in the article.  The calculated confidence intervals based on the published data for successful CVC placement for the LM group was 80 to 93%, and for the US group was 84 to 95% .  The calculated confidence intervals for number of site attempts demonstrated wide intervals, likely due to small sample size..

4. Will the results help me in caring for my patients?
   
   
   1. Can the results be applied to my patient care?

      The study demonstrated a statistically significant decrease in the number of site attempts with the use of US and risk of arterial puncture during placement.  There were not statistically significant differences in the success of placement and the time to placement of the CVCs between the groups.  This study does not provide evidence to support widespread implementation of the ultrasound guided CVC placement in the ICU setting.  However, a larger study with randomization may provide further supportive evidence for the use of US over the LM technique for CVC placement.  The study was performed in a PICU so therefore should be generalizable to the pediatric intensive care setting.  The patients that I take care of are similar in demographics to those that were included in the study as is the size of the unit.

   2. Were all clinically important outcomes considered?

      Clinically relevant outcomes such as line infections, pneumo/hemothoraces, and hematoma formations were not discussed in detail; they were included in a general category of ‘complications’.  The incidence of line infections could also be considered.   The sites changing to the IJ instead of femoral could have infectious implications.   The results of the study lead to the conclusion that it would be beneficial for pediatric intensive care units to purchase an ultrasound unit.  It would be a significant investment in not only time as well as education and instruction in the use of the ultrasound device, but should lead to improved success of insertion of central venous catheters.

   3. Are the likely treatment benefits worth the potential harms and costs?

      The authors of the article stated that they believed the US guided CVC placement “decreased the number of anatomical sites attempted, decreased the number of access attempts, and decreases inadvertent artery punctures in children.�  From the data provided by the authors, it would be difficult to ascertain whether or not one method (the landmark versus the US) would provide more benefit over the other to justify the equipment cost and training required to use US uniformly with all CVC placements.
      
      In comparison, a study of the utility of ultrasound guided central venous cannulation in pediatric surgical patients by Leyvi, 149 patients were retrospectively studied (1).  The study evaluated placement of internal jugular venous catheters in pediatric patients undergoing cardiac surgery.  Success rate for cannulation via use of the ultrasound was 91.5% with success rate for landmark technique to be 72.5% (p=0.01).  The study found no significant difference for rate of traumatic complications between the two methods.   Success rates for both techniques in children less than 10kg and those less than 1 year old were lower as compared to children over 1 year and greater than 10kg, however, ultrasound guided placement was more successful than landmark techniques in that subset of patients.  Results of decreased successful placement of catheters in children less than 1 year and those weighing less than 10kg were attributed to difficulty in obtaining proper positioning in smaller patients for placement of the ultrasound transducer.  The study does show that ultrasound guided catheter placement is superior to the landmark technique in placement of an internal jugular vein CVC.  The study did not report the amount of training in US use that the operators completed, but did state that all procedures were performed by senior anesthesia residents with faculty direction. 
      
      In conclusion, there have been many studies performed on assessing ultrasound to guide in placement of CVCs.  There have been well documented studies in adult journals showing improved success of catheter placement as well as in nursing journals regarding peripheral central venous catheter placement with the use of ultrasound.   Although the study by Froehlich et al did not show statistical difference in success rates of placement by US as compared to landmark techniques, other supportive studies (1-3) have been performed focusing on specific anatomic sites which would suggest that ultrasound guided CVC placement is superior to the traditional landmark technique.  

References

1. Galina Leyvi MD, David G Taylor MD, Elizabeth Reith MD and John D Wasnick MD MPH.  Utility of ultrasound-guided central venous cannulation in pediatric surgical patients: a clinical series.  Pediatric Anesthesia 2005; 15: 953-958.
2. Milling, Truman J Jr MD; Rose, John MD; Briggs, Willam M PhD; Birkhahn, Robert MD, MS; Gaeta, Theodore J DO, MPH; Bove, Joseph J MD; Melniker, Lawrence A MD, MS.  Randomized, controlled clinical trial of point-of-care limited ultrasonography assistance of central venous cannulation:  The Third Sonography Outcomes Assessment Program (SOAP-3) Trial.  Critical Care Medicine 2005; 33 (8): 1764-1769.
3. Nichols, Inez RN, MSN, CRNI; Doellman, Darcy RN, BSN, CRNI.  Pediatric Peripherally Inserted Central Catheter Placement:  Application of Ultrasound Technology.  Journal of Infusion Nursing 2007; 30 (6): 351-356.

Last Updated: May 24, 2010

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