Perineural dexamethasone with subsartorial saphenous nerve blocks in ACL reconstruction

Subsartorial saphenous nerve blockade (SSNB) is an effective analgesic alternative to femoral nerve blockade after anterior cruciate ligament (ACL) reconstruction with bone-tendon-bone (BTB) autograft. It was hypothesized that dexamethasone in a SSNB will prolong analgesia, improve pain and satisfaction, and reduce postoperative opioid requirements and side effects. One hundred ninety-five patients undergoing ACL reconstruction with BTB autograft (ages 16-65) were enrolled. Subjects received SSNB with 13 ml of 0.5 % bupivacaine (control group), 1 mg preservative-free dexamethasone +0.5 % bupivacaine (treatment group I), or 4 mg preservative-free dexamethasone +0.5 % bupivacaine (treatment group II). Subjects received identical perioperative management. On postoperative days 1 and 2, subjects reported perceived block duration, pain scores, satisfaction, opioid use, and side effects. Cox-proportional hazards modelling was used to compare block duration, adjusting for body mass index, age, sex, tourniquet time, American Society of Anesthesiologists classification, and intravenous dexamethasone dose. Patient-perceived block duration was significantly increased in treatment group I [hazard ratio (95 % confidence interval [CI]) 0.48 (0.31-0.75); P = 0.001] and treatment group II (hazard ratio (95 % CI): 0.52 (0.33-0.81); P = 0.004) compared to control. The block was extended from a median (95 % CI) of 33.1 (28.4-37.3) to 41.2 (32.4-50.9) and 46.5 (35.8-48.9) hours, respectively. Additionally, patients in treatment group II reported increased time that block provided pain relief, higher patient satisfaction, lower pain scores at rest, and decreased drowsiness and confusion. The addition of 1 and 4 mg of dexamethasone to the block injectate significantly increased SSNB duration by 8-13 h compared to control. Therapeutic study, level 1.