Two methods, or routes, are used to administer general anesthetic agents: inhalation and intravenous injection. An inhalation anesthetic is administered as a gas the patient breathes, whereas intravenous agents are administered directly into the bloodstream through a small catheter placed in a vein. No intravenous agent in current use can provide all the required effects and only those effects, so a combination of administration methods is used. The term balanced anesthesia refers to the technique that uses a combination of inhalation and intravenous agents to accomplish general anesthesia. Another (but much less common) anesthesia technique uses a combination of a regional block, such as an epidural, and a light general anesthetic. This technique is useful for select patients undergoing major vascular procedures because it decreases the amount of general anesthetic agents required, helping to maintain cardiovascular stability, and provides an effective means of postoperative pain control. This technique is also valuable for use in selected orthopedic, thoracic, and other surgical specialty procedures.