Faculty Bibliography

OBJECTIVES: To determine the effect of spinal anesthesia (SA) on short-term outcomes when compared with general anesthesia in operatively managed tibial plateau fractures. DESIGN: This is an institutional review board-approved retrospective review of prospectively collected data. SETTING: Two level-1 trauma centers. PARTICIPANTS: One hundred twelve patients with a surgically managed tibial plateau fracture were identified within a registry of patients. INTERVENTION: Of these, 29 (25.9%) received SA and 83 (74.1%) received general anesthesia in a nonrandomized fashion. MAIN OUTCOME MEASURES: Short Musculoskeletal Functional Assessment scores, pain levels, knee range of motion, complications, and reoperations. RESULTS: SA was found to be a predictor of lower pain scores at 3 months (odds ratio, 0.32; 95% confidence interval, 0.12-0.95; P = 0.039) but not at 6 months (P = 0.266) or the latest follow-up (P = 0.056). In the multivariate Short Musculoskeletal Functional Assessment model, although anesthesia type was not found to be a statistically significant predictor, other predictors were identified. Anesthesia type was not a predictor of complications or reoperations. In the univariate analysis, SA was associated with an increased knee range of motion at 3 months (121 vs. 111 degrees; P = 0.048) but not at 6 months (P = 0.31) or the latest follow-up (P = 0.053). CONCLUSION: In patients who undergo surgical management of a tibial plateau fracture, the use of SA is associated with decreased pain levels in the early postoperative period; however, there was no effect on functional assessment scores. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Regarding nerves as simple cables and electrical conduits is a gross error that does not allow us to understand the anomalies and disorders observed postoperatively. Instead, nerves should be seen as a living tissue of which physiological regulation is as complex as that of the blood-brain barrier. This review describes the basic structure and functions of this blood-nerve barrier and highlights the mechanisms of its breakdown and the resultant disorders. For clinical practice, it is important to note that the diffusion of molecules from the perineurium or from the blood is very limited, and so the blood-nerve barrier is a major pharmacologic barrier. Any stress upon neural physiological balance, particularly the terminal vascular blood supply, will induce the classic inflammatory cascade. Due to the complexity of the vascular system, nerve ischaemia will occur more quickly when the terminal blood supply is compromised. This blood supply can adapt in a variety of ways but when these possibilities of adaptation are exceeded, tissue ischaemia may be more extensive. Also, even after the initial injury has subsided, inflammation can cause a secondary insult. This could be particularly important in some patients with subclinical neuropathy.

BACKGROUND: Saphenous nerve block contributes to analgesia after knee and lower leg surgery. However, literature reports a wide range of volumes of local anesthetic being used for this block. METHODS: A non-randomized controlled trial in a single university hospital in March 2015. Eighteen healthy volunteers (ASA 1 status, aged 27-43 years; male-to-female ratio 11/7) were needed to determine the minimum local anesthetic volume (MLAV) of mepivacaine 2% using the Dixon up-and-down method to achieve a selective ultrasound-guided saphenous nerve block. The primary endpoint MLAV (ED50 and ED95) for an ultrasound-guided saphenous nerve block were determined. The secondary endpoints were the position of the saphenous nerve, block onset and duration of action, cutaneous spread of the block, and the occurrence of femoral nerve motor block. RESULTS: The measured MLAV dose that was effective in 50% of cases (ED50) for a complete saphenous nerve block was 1.5 mL; the calculated MLAV dose for 95% of cases (ED95) was 1.9 mL. The saphenous nerve was encountered in almost all cases on the anterior/anteromedial aspect of the femoral artery. We found no correlation between local anesthetic volume and the onset or duration of the block. Cutaneous spread of the nerve block was observed on the anteromedial aspect of the lower leg, with considerable individual variation between individuals in the study. No femoral motor block was observed. CONCLUSIONS: For a selective ultrasound-guided saphenous nerve block, the ED95 MLAV of mepivacaine 2% is 1.9 mL.

Background: The objective of this study is to determine subclinical changes in hand sensation after brachial plexus blocks used for hand surgery procedures. We used Semmes-Weinstein monofilament testing to detect these changes. We hypothesized that patients undergoing brachial plexus nerve blocks would have postoperative subclinical neuropathy detected by monofilament testing when compared with controls. Methods: In total, 115 hand surgery adult patients were prospectively enrolled in this study. All patients undergoing nerve-related procedures were excluded as well as any patients with preoperative clinically apparent nerve deficits. Eighty-four patients underwent brachial plexus blockade preoperatively, and 31 patients underwent general anesthesia (GA). Semmes-Weinstein monofilament testing of the hand was performed preoperatively on both the operative and nonoperative extremities and postoperatively at a mean of 11 days on both hands. Preoperative and postoperative monofilament testing scores were compared between the block hand and the nonoperated hand of the same patient, as well as between the block hands and the GA-operated hands. Results: There were no recorded clinically relevant neurologic complications in the block group or GA group. A statistically significant decrease in sensation in postoperative testing in the operated block hand compared with the nonoperated hand was noted. When comparing the operated block hand with the operated GA hand, there was a decrease in postoperative sensation in the operated block hand that did not reach statistical significance. Conclusions: Brachial plexus blockade causes subtle subclinical decreases in sensibility at short-term follow-up, without any clinically relevant manifestations.

Introduction Successful total knee replacement (TKA) is dependent, among other factors, on balancing the pressure in both femoro-tibial compartments using judicious soft-tissue release and insert thickness. Recently, some surgeons have started to test passive, soft tissue controlled pressure balance with the assistance of a sterile sensor system intra-operatively. One surgeon at our institution requested for the anesthesia team to provide surgical anesthesia for his patients that would allow him to monitor active pressure balance intra-operatively, i.e., with the patient actively flexing and extending the knee during surgery. A high-dose intrathecal sufentanil in combination with low dose local anesthetic can provide a sensation-only block with no added medical or pain risk to the patient. By performing a motor-sparing spinal anesthetic with an intraoperative wake up test, we can allow surgeons to test active pressure balance to improve the accuracy of the pressure balancing technique. Materials and methods (NA for case report) NA Results/Case report A 46-year-old male with a history of right knee osteoarthritis underwent a right TKA. A spinal anesthetic was performed at the L3-L4 interspace using a mixture of 7.5 mcg of sufentanil diluted to 1.5 mL using normal saline, and 1mL of isobaric bupivacaine (5 mcg/mL). Sedation was maintained with a propofol infusion. Once components were cemented, sedation was paused and a wake-up test was performed. The patient was verbally responsive. The surgeon then asked the patient to lift his right leg up in the air and to flex and extend at the knee. The patient complied without signs of weakness or pain. The patient was then sedated again with 1 mg midazolam, 25 mcg fentanyl, and the propofol infusion was resumed for the remainder of the case. Post-operatively in PACU, the patient was hemodynamically stable, reported a pain score of 0, had intact lower extremity strength and no recollection of the intraoperative test. Discussion The current standard of care for patients undergoing a TKA under spinal anesthesia typically includes 2 to 3 mL of a long acting local anesthetic such as 0.5% bupivacaine. This dose used for single shot spinals is adequate for surgical anesthesia; however, patients will also exhibit motor weakness. As a result, a test of active soft tissue pressure balance will not be possible with this dose. Especially in obstetrics where motor function is important, neuraxial opioids can be combined with a lower dose local anesthetic to provide to surgical anesthesia and analgesia. Using a spinal solution with a low dose of local anesthetic in combination with an opioid such as sufentanil, the motor function of the operated leg is not inhibited during surgery. Other studies have used 5 mcg of intrathecal sufentanil, but due to a reduced dose of local anesthetic, we elected to increase the dose of sufentanil to ensure the patient would not experience pain. A prospective study examining the reliability of this technique as well as, from the orthopedic standpoint, the influence of balancing the pressures with active motion on the outcome of the TKA is planned