Postoperative Pain After Inguinal Herniorrhaphy with Different Types of Anesthesia

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Abstract
In a randomized, double-blind study,postoperative pain was assessed in 36 patients undergoing inguinal herniorrhaphy with three types of anesthesia: general (thiopental-nitrous oxide-halothane); general with the addition of local (infiltration of the abdominal wall with 0.25% bupivacaine along the line of the proposed incision); and spinal (0.5% bupivacaine). The severity of constant incisional pain, movement-associated incisional pain, and pain upon pressure applied to the surgical wound using an algometer was assessed with a visual analogue self-rating method at 24 h, 48 h, and 10 days after surgery. The addition of local anesthesia significantly decreased the intensity of all types of postoperative pain. This effect was especially evident with constant incisional pain that disappeared almost completely 24 h after surgery. With pain caused by pressure on the site of the surgical incision, the pain score difference between general and general plus local anestheisa was obvious even 10 days after the surgery (with 0.4-kg/cm2 pressure, the pain scores were 16 .+-. 3 vs 2 .+-. 1, P < 0.01). The difference in postoperative pain scores between spinal and general anesthesia groups indicated that spinal anesthesia also decreases the pain intensity. However, this decrease is less pronounced than that seen with the addition of local anesthesia: movement-associated pain scores 24 h after surgery were 72 .+-. 5 in the general anesthesia group, 40 .+-. 6 in the spinal anesthesia group, and 16 .+-. 3 in the general plus local anesthesia group, and 16 .+-. 3 in the general plus local anesthesia group (with P < 0.002 between the groups). Our results indicate that postoperative pain after inguinal herniorrhaphy can be significantly decreased if the surgery is performed with the use of local or spinal anesthesia. We hypothesize that neural blockade, by preventing nociceptive impulses from entering the central nervous system during and immediately after surgery, suppresses the formation of the sustained hyperexcitable state in the central nervous system that is responsible for the maintenance of postoperative pain.