My patient is a stroke victim with flaccid paralysis on the left side of her body. She has wonderful, easy-to-see veins on her left arm and tiny, tortuous veins on the right. As I struggled to draw blood from her "good" arm, as I was taught, I questioned this practice. Since the injury is in the brain, not a limb, why are we taught to avoid venipuncture on a stroke victim's flaccid arm?-M.R., ONTARIO
The reason lies not with the brain injury, but with the stroke's impact on mechanisms of venous blood flow. Normal muscle contraction, known as the venous pump, helps force blood back to the heart. These muscle contractions also help prevent blood backflow by forcing upper vein valves to open and lower valves to close. If an arm is paralyzed, the venous pump is lost, dramatically increasing the risk of vein thrombosis.
No matter how good your technique, you disrupt the vein's tunica intima and traumatize the vein every time you perform venipuncture. Add to this the loss of the venous pump, and your patient now has two risk factors for venous thrombosis.
Except for a severe emergency situation, our consultant can't think of any time that using a paralyzed arm for venipuncture would be appropriate. She agrees that you should also avoid tortuous veins in the unaffected arm, but she suspects that these veins are superficial. She suggests that you try palpating for deeper veins. Because the unaffected arm is still active, it will have veins available for venipuncture, but they may not be easy to see.