Blood Samples
Blood samples are obtained through a finger-prick or withdrawn through a needle placed into a vein. The most commonly used vein is the one on the inside of the elbow. A cream anesthetic, EMLA, can be used to numb the area beforehand. It should be applied to the skin about an hour before blood is drawn. A surgically implanted catheter can allow for easy access to veins without repeated needle sticks. The Hickman and Broviac catheters are external catheters. A small catheter is inserted into a vein near the collarbone and threaded into a large vein near the heart. The end of the catheter exits the skin above the nipple line. The catheter is usually implanted while the patient is under general anesthesia. Another option is a subcutaneous port or catheter. One end of this device is threaded into a large vein near the heart, but at the other end a special cap or portal is placed flat against the chest wall underneath the skin. A needle is used to access the port.
Bone Marrow Aspiration
During a bone marrow aspiration the doctor uses a thin needle to remove a small amount of tissue from a bone, usually the hip. The amount removed is about one teaspoonful. Samples may be taken from a few different areas of bone, because the percentages of cells found can vary from place to place. The patient lies face down on a table. The skin on top of the bone is anesthetized with Novacaine® or Lidocaine®. The doctor inserts a needle into the hip area and into the bone, and removes samples of marrow through the needle.
Bone Marrow Biopsy
This procedure is similar to a bone marrow aspiration, but it involves removing more marrow and tissue than in an aspiration. It is usually done at the time of the bone marrow aspiration. The doctor uses a larger needle, and removes a piece of marrow and bone about 1/16 inch in diameter and half an inch long. The sample is usually taken from the hip bone. Several samples may be taken during the procedure, because the percentage of cells found can vary from place to place. Often, people feel pressure when the needle is inserted.
Lymph Node Biopsy
A lymph node biopsy is a surgical procedure in which lymph nodes are removed so they can be examined in the laboratory for abnormal cells. If the lymph nodes are close to the surface of the body, the surgeon might perform the procedure using only a local anesthetic. For nodes that are deeper in the body, such as in the abdomen, the surgeon will use general anesthesia.
Lumbar Puncture
A lumbar puncture gives a doctor access to the cerebrospinal fluid, which bathes the central nervous system. The procedure can be used to collect the fluid for laboratory tests or to inject drugs into the fluid. The patient lies on his side with his knees by his chest. After applying a local anesthetic, the doctor inserts a needle into the lower back, between two vertebrae, and into the space that contains the fluid. The fluid can then be collected through the needle or drugs can be injected into the fluid. The procedure is also called a spinal tap. If medicine is given through the needle, it is called intrathecal therapy.
