A comparison of hemolysis rates using intravenous catheters versus venipuncture tubes for obtaining blood samples Authors: C o l l e e n K e n n e d y , RN, A D N , S a r a h A n g e r m u l l e r , RN, M g d , M S N , R o b i n K i n g , RN, B S N , S h e r i N o v i e l l o , RN, M S N , J o a n n W a l k e r , RN, A D N , J o a n i e W a r d e n , RN, M S N , a n d S u s a n V a n g , RN, M S N , C o l u m b u s , G e o r g i a

Objective

T h e p r i m a r y p u r p o s e of t h i s s t u d y w a s to c o m p a r e t h e r a t e of h e m o l y s i s in b l o o d s a m p l e s o b t a i n e d b y a n IV c a t h e t e r v e r s u s t h e r a t e in s a m p l e s o b t a i n e d b y v e n i p u n c t u r e ( V a c u t a i n e r t u b e s a n d n e e d l e s ; B e c t o n D i c k i n s o n V a c u t a i n e r S y s t e m s , F r a n k l i n Lakes , N.J.). S u b s e q u e n t l y , v a r i a n c e in IV c a t h e t e r d i a m e t e r w a s r e v i e w e d to d e t e r m i n e i t s i n f l u e n c e o n h e m o l y s i s r a t e of IV c a t h e t e r a sp i r a t e .

Design

A r a n d o m i z e d , p r o s p e c t i v e s t u d y w a s u s e d to e v a l u a t e h e m o l y s i s d i f f e r e n c e s b e t w e e n t h e t w o b l o o d s a m - p l i n g m e t h o d s . A d e s c r i p t i v e , r e t r o s p e c t i v e r e v i e w of s t u d y d a t a w a s u s e d to e v a l u a t e t h e i m p o r t a n c e of t h e v a r i a b l e IV c a t h e t e r d i a m e t e r .

Methods

T h e s t u d y g r o u p c o n s i s t e d of p a t i e n t s w h o c a m e to t h e e m e r g e n c y d e p a r t m e n t a n d r e q u i r e d b o t h a n IV i n f u s i o n a n d b l o o d s a m p l i n g for d e t e r m i n a t i o n of e l e c t r o l y t e l e v e l s a n d c o m p l e t e b l o o d cel l c o u n t . P e d i a t r i c p a t i e n t s ( y o u n g e r t h a n 16 y e a r s ) w e r e e x c l u d e d . T h e ED p a t i e n t s w h o q u a l i f i e d for t h e s t u d y w e r e r a n d o m l y a s s i g n e d to e i t h e r g r o u p A or B. T h e b l o o d s a m p l e s for p a t i e n t s in t h e A g r o u p w e r e o b t a i n e d t h r o u g h t h e IV c a t h e t e r a t t h e t i m e of i n s e r t i o n . T h e IV c a t h e t e r s r a n g e d in s i ze f r o m 24 g a u g e to 14 g a u g e . P a t i e n t s in t h e B g r o u p a l so h a d i n s e r t i o n of a n IV l ine, b u t t h e i r b l o o d s a m p l e s w e r e o b t a i n e d b y V a c u t a i n e r v e n i p u n c t u r e a t a s e p a r a t e s i te . T h e V a c u t a i n e r n e e d l e w a s s t a n d a r d i z e d a t 21 g a u g e . All b l o o d s a m p l e s w e r e c o l l e c t e d b y o n e of s e v e n e x p e r i e n c e d ED n u r s e s . T h e n u r s e w h o col- l e c t e d t h e b l o o d s a m p l e for a n y s t u d y p a t i e n t w a s r e s p o n s i b l e for r e s u l t fo l low-up .

Colleen Kennedy, Sarah Angermuller, Sheri Noviello, Joann Walker, Joanie Warden, and Susan Vang are staff nurses, and Robin King is assistant nurse manager, Emergency Department, The Medical Center, Columbus, Georgia. Ms. Angermuller, Ms. King, Ms. Noviello, Ms. Warden, and Ms. Vang are instructors in the nursing program at Columbus State University, Columbus, Georgia. For reprints, write Colleen Kennedy, RN, ADN, 14021 Upatoi Lane, Upatoi, GA 31829. Copyright �9 1996 by the Emergency Nurses Association. 0099-1767/96 $500 + 0 18/9/77088

Results A t o t a l of 165 p a t i e n t s p a r t i c i p a t e d in t h e s t u d y ; 87 p a t i e n t s w e r e a s s i g n e d to t h e A (IV) g r o u p , a n d 78 p a t i e n t s p a r t i c i p a t e d in t h e B ( v e n i p u n c t u r e ) g r o u p . In g r o u p A a t o t a l of 12 of 87 (13 .7%) b l o o d s a m p l e s h e m o l y z e d . H e m o l y s i s o c c u r r e d in 3 of 78 (3.8%) of g r o u p B s a m p l e s . T h e s e f i n d i n g s w e r e s t a t i s t i c a l l y s i g n i f i c a n t (p < 0.05). W h e n w e e x a m - i n e d t h e v a r i a b l e IV c a t h e t e r d i a m e t e r , w e n o t e d a l o w e r i n c i d e n c e of h e m o l y s i s w i t h l a r g e r c a t h e t e r d i a m e t e r s : 24 g a u g e (100%), 22 g a u g e (25%), 20 g a u g e (15%), 18 g a u g e (10%), 16 g a u g e (0%), 14 g a u g e (0%). Th i s f i n d i n g w a s s t a t i s t i c a l l y s i g n i f i c a n t (p < 0.05).

Conc lus ions

H e m o l y s i s of b l o o d s a m p l e s o b t a i n e d b y a n IV c a t h e t e r w a s s igni f icant ly h i g h e r t h a n w h e n b lood w a s o b t a i n e d t h r o u g h V a c u t a i n e r v e n i p u n c t u r e . T h e r e is a n i n v e r s e c o r r e l a t i o n b e t w e e n IV c a t h e t e r d i a m e t e r a n d t h e r a t e of h e m o l y s i s . (J E m e r y N u r s 1996;22:566-9)

B e fo re t h i s s t u d y , m o s t b l o o d s p e c i m e n s in ou r

e m e r g e n c y d e p a r t m e n t w e r e o b t a i n e d b y

V a c u t a i n e r p h l e b o t o m y . H o w e v e r , if a p a t i e n t

r e q u i r e d b o t h a n IV i n f u s i o n a n d b l o o d t e s t s , m o s t of

ou r n u r s e s e l e c t e d to o b t a i n t h e b l o o d s a m p l e s

t h r o u g h t h e IV c a t h e t e r a t t h e t i m e of i t s i n s e r t i o n .

N o t on ly w a s p a t i e n t d i s c o m f o r t m i n i m i z e d , b u t w e

p e r c e i v e d t h a t r e s u l t s w e r e a s a c c u r a t e a s t h o s e

s a m p l e s o b t a i n e d b y V a c u t a i n e r v e n i p u n c t u r e . In

a d d i t i o n , o b t a i n i n g b l o o d s a m p l e s t h r o u g h t h e IV l ine

w a s t h o u g h t to s a v e v a l u a b l e c l in i ca l t i m e b e c a u s e

i n s e r t i o n of t h e IV c a t h e t e r a n d b l o o d s a m p l i n g w e r e

p e r f o r m e d s i m u l t a n e o u s l y .

U n f o r t u n a t e l y , t h e h o s p i t a l l a b o r a t o r y r e p o r t e d a

h i g h i n c i d e n c e of h e m o l y s i s * in s a m p l e s o b t a i n e d in

*Hemolysis is the b r eakdown of red blood cells wi th the "l iberation" of the hemoglobin. Other intracellular contents , especially potassium, are re leased into the serum. The pres- ence of hemolysis, part icularly in complete blood cell counts (CBCs) and electrolyte tests , general ly requires new blood samples and addit ional tes ts , which is expens ive and t ime consuming. Therefore it is desirable for emergency depart- men t s to select a me thod of blood collection t ha t minimizes hemolysis.

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Table 1 Comparison of h e m o l y s i s rates of two blood sampl in g m e t h o d s

Blood sam pl ing method No. of pat ients H e m o l y z e d samples H e m o l y s i s rate (%)

Group A (IV catheter) 87 12 13.7 Group B (Vacutainer) 78 3 3.8

the emergency depar tment for complete blood cell counts (CBCs) and electrolyte levels. The high hemOl- ysis rate was at t r ibuted to the ED pract ice of obtain- ing blood samples through IV catheters. When our nurse manager proposed a policy prohibit ing blood sampling through IV catheters, the clinical nurses vigorously disagreed.

We disputed the laboratory's assert ion that blood s p e c i m e n s hemolyzed more frequently when ob ta ined through an IV ca the te r than through Vacutainer venipuncture. Important clinical consid- erations such as pat ient comfort and nursing effi- c iency prompted our ED nursing staff to confront this cl inical ques t ion of IV hemolys is rate versus Vacutainer hemolysis rate scientifically.

The clinical nursing staff reviewed the current literature for s tudies comparing hemolysis rates of blood spec imen collection by Vacutainer venipunc- ture versus through IV catheters. One medical s tudy evaluated the accuracy of CBCs and blood chemistry panels in samples obta ined through a functioning IV line. 1 A serendipi tous finding noted that hemolysis occurred in 3 of 33 (9%) blood samples obtained by IV sampling. However, there was no mention of hemol- ysis in the Vacutainer control group in this study. Because we were unable to find the necessary data to support our view that no difference existed in blood samples obtained through IV catheters and those obtained through Vacutainer venipuncture, we devised our own clinical study.

Methods After approval by the hospital 's investigational review board, a prospect ive study was des igned whereby pat ients who came to our emergency depar tment were evaluated for inclusion in our study comparing hemolysis rates of blood from an IV catheter versus those ob t a ined by Vacuta iner ven ipunc ture . Candida tes for s tudy inclusion were those pat ients who required inser t ion of an IV line, and de termi- nat ion of CBCs and electrolytes. We excluded pedi- a t r ic pa t i en t s (those younger than 16 years). Seven expe r i enced ED nurses were responsible for pa t i en t

Table 2 Correlation of h e m o l y s i s rates w i t h IV catheter s i z e

IV catheter Sample Hemolys i s s i z e (gauge) s i z e (n) rate (%)

24 1 100 22 4 25 20 39 15 18 40 10 16 2 0 14 1 0

selection, obta in ing blood samples , and da ta collec- tion.

If pa t ien ts met all se lec ted criteria, they were enrolled in the s tudy and randomly a s s igned to group A or B. Pa t ien ts in group A had an IV line inser ted and blood samples were ob ta ined through the IV ca the te r hub before any fluid infusion. Insy te c a t h e t e r - o v e r - n e e d l e IV l ines (Becton Dickinson, Sandy, Utah), were used. Catheter size ranged from 24 g a u g e to 14 gauge . The IV ca the ter size and ven ipunc tu re s i te were at the nurse ' s dis- cretion. Blood was a sp i r a t ed in sufficient quant i ty to obta in a CBC and de te rmine electrolyte levels. A 12 ml syr inge was used to gent ly asp i ra te the blood. The blood was t ransfer red to the appropr ia te tubes via an 18-gauge needle . The r eg i s t e red nurse who ob ta ined the blood sample then imme- dia te ly sent the blood to the hospi ta l laboratory where all ED laboratory work is done "stat." The laboratory technolog is t de t e r m i ne d whe ther the sample was hemolyzed. The reg i s t e red nurse who ob ta ined the sample was respons ib le for recording these data.

Patients ass igned to the B group had blood sam- ples obtained by Vacutainer venipuncture. The blood was drawn through a 21-gauge needle directly into tubes for the CBC and electrolytes. The nurse was responsible for sending the blood to the laboratory, obtaining the results, and recording data.

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100

tw U)

80

60

40

20

0 14 1T3 18 20 22 24

IV Catheter Size

Figure 1 Data revealed an inverse correlation between the IV catheter size and the rate of blood hemolysis, with a higher rate of hemolysis found with smaller IV catheter diameters.

Results

A total of 165 pat ients par t ic ipated in the hemolysis study. Group A (IV collection group) consisted of 87 patients. A total of 85 pat ients were initially enrolled in the B (Vacutainer) group, but the nurses were unsuccessful in obtaining blood samples from 7 of these patients; therefore the B group consisted of 78 patients.

In group A a total of 12 of 87 (13.7%) blood sam- ples hemolyzed. The electrolytes were hemolyzed in all 12. Three of these 12 samples also had a hemolyzed CBC.

In group B only 3 of 78 (3.8%) blood samples hemolyzed. Of these three, one CBC and all three electrolyte tests were hemolyzed.

A comparison of the percentage of hemolyzed samples be tween study groups A and B was made with chi-square (Z2). A p value <0.05 was considered significant. Group A was found to have a statistically higher hemolysis rate than group B (Z 2 = 4.89, p = 0.03) (Table 1).

Although blood aspi ra ted from an IV catheter had a significantly higher hemolysis rate than that aspira ted by Vacutainer venipuncture, it was noted that the rate of hemolysis declined with larger IV catheter d iameter (the larger the catheter diameter the smaller the IV gauge number).

The hemolysis rates for the various IV catheter sizes were as follows: 24 gauge (100%), 22 gauge (25%), 20 gauge (15%), 18 gauge (10%), 16 gauge (0),

14 gauge (0). A regression analysis was conducted to study the relationship be tween IV catheter size and the rate of blood hemolysis. An inverse correlation was found be tween the IV catheter diameter and the rate of hemolysis: the smaller the IV catheter diame- ter the higher the rate of hemolysis. The regression coefficient (R value) is +0.82 and the p value is 0.047 (Table 2 and Figure 1).

Discussion The finding that blood samples obtained through IV catheters had higher hemolysis rates than those obtained by Vacutainer venipuncture was surprising to the nurses who accumulated the data. It had been our clinical percept ion that no difference would exist. We have learned that although clinical "intuition" is valuable, it is not always objective.

In d i scuss ing the merits of this research it is important to note a number of limitations, as follows: 1. IV catheter diameter emerged as an important

variable that requires further study. Although the regression model showed a relationship be tween IV catheter diameter and hemolysis rate, the number of subjects in the very small (24 gauge, 22 gauge) and the very large (16 gauge, 14 gauge) catheter groups was limited; therefore the conclusions from this model are not as strong as they could be.

2. Venipuncture site is another variable that could have affected the s tudy outcome. Did blood sam- ples obtained from hand veins hemolyze more frequently than those obta ined from forearm veins? Did forearm blood hemolyze more often than blood from the antecubi tal area? Although we recorded the sample site and it does not appear that a difference in hemolysis rates exists from one venipuncture site to another, this vari- able was not controlled. A definitive conclusion would require further research.

3. Syringe suc t ion dur ing sampl ing from IV ca the te rs may have affected the higher IV blood hemolysis rate. Al though "gentle" suc- tion was used, we were unable to quantify this variable. At the t ime of this study, Vacutainer tube adap te r s were not avai lable at our inst i tu- tion. These adap te r s a t tach to IV catheter hubs and allow blood to be drawn direct ly into vac- uum tubes . In add i t ion to e l imina t ing the syr inge suc t ion variable in IV blood drawing, it is a safer p rac t ice than t ransferr ing blood with a syr inge and needle. We r ecommend further s tudy and cont inue to bel ieve that desp i t e

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apparent higher hemolysis rates, some valid clini- cal reasons exist for obtaining blood samples from an IV catheter. Frequently a patient who requires both an IV infusion and blood sampling has just "one good vein." Perhaps the most compelling incentive for obtaining blood samples through the IV catheter is patient comfort For patients who

find venipuncture frightening, the possibility of just one "stick" is reassuring.

Reference

1. Herr RD, Bossart P J, Blaylock RC, Kroger K, Owen J. Intravenous catheter aspiration for obtaining basis analytes during intravenous infusion. Ann Emerg Med 1990;19:789-92.

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