In medical terms, aspiration refers to removing fluid or cells from the body, usually under vacuum pressure of a suction unit or an aspiration syringe. A type of medical syringe, an aspiration syringe is utilized to draw cells or liquid material such as blood, pus, cerebrospinal fluid (CSF) or ascites from the body as opposed to administering a medication or fluid. Aside from a very specialized type of aspiration syringe, most are indistinguishable from their medication-administrating cousins. Both types consist of a transparent column with measurement markings on the exterior, holding an interior plunger with a rubber cap on one end and the plunger handle on the other. An aspiration syringe is fitted with a needle of adequate length to reach the location of the fluid to be removed and of adequate gauge, or diameter, to remove the material, whether a watery fluid or a semi-solid substance.
These syringes are often used to remove cells and fluid for a laboratory biopsy to determine whether a nodule or its surrounding fluid is benign or malignant, determining the patient's future treatment. An aspiration syringe is also used to withdraw cerebrospinal spinal fluid (CSF) during spinal taps to ascertain what infectious agents are at work in conditions such as meningitis. Purulent material or pus removed from dermatological boils or carbuncles is also withdrawn with an aspiration syringe and sent to a bacteriological laboratory to determine the specific pathogen causing the infection. These laboratory results help determine what antibiotic would be appropriate for treatment.
Use of an aspiration syringe can not only provide diagnostic information, but also decrease pain and discomfort as well. Liver failure or chronic hepatitis often results in serous fluid — ascites — collecting within the abdominal peritoneal cavity. This fluid buildup can cause abdominal discomfort, anorexia and even shortness of breath as the amount of fluid increases, and begins to exert pressure against the abdominal organs and the diaphragm. If a patient's condition does not require the insertion of a shunt for continuous drainage of the ascites, then an intermittent drainage of the fluid can be accomplished with a large aspiration syringe. Even drainage of joint synovial fluid during periods of acute inflammation — in an injured knee, for example — can provide some pain relief and increased range of motion.
Even syringes used to administer medication intramuscularly (IM) often require aspiration after injection and before the plunger is depressed to administer the medication. This precaution is taken to ensure that an injection meant to be given intramuscularly has not inadvertently punctured a blood vessel. If blood is noted in the syringe during aspiration, the needle is withdrawn slightly prior to finally giving the medication.