Faculty Bibliography

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

Transient neurologic symptoms (TNS) led to the abandonment of intrathecal lidocaine. We reviewed the published literature for information about the duration of action and side effects of intrathecal prilocaine, which has been recently reintroduced in Europe. Medline and EMBASE databases were searched for the time period from 1966 to 2014. Fourteen prospective and one retrospective study were retrieved. The duration of the surgical block can be adjusted using doses between 40 and 80mg. Hyperbaric prilocaine in doses as low as 10mg can be used for perianal procedures. Four cases of TNS in 486 patients were reported in prospective studies, and none in 5000 cases in a retrospective data set. Spinal prilocaine appears to be safe and reliable for day case anesthesia. However, as chloroprocaine has a shorter duration and a lower risk of TNS and urinary retention, the indications for prilocaine remain to be defined.

OBJECTIVE: Our aim was to establish a plasma concentration curve for ropivacaine following femoral nerve blockade and to ascertain whether the resulting plasma concentrations differ significantly depending on whether neurostimulation (NS) or ultrasound (US) guidance was used. METHODS: Sixteen male and female subjects aged 18 to 80 who were scheduled to undergo unilateral total knee replacement or anterior cruciate ligament reconstruction under general or spinal anaesthesia, and for whom a femoral nerve block was indicated for postoperative analgesia, were enrolled in this prospective, randomised study. Patients were randomised to undergo either US or NS-guidance femoral nerve blocks. All blocks were performed with 20mL of 5mg/mL ropivacaine. Blood samples were drawn before the nerve block and 20, 30, 40, 50, 60, 70, and 80minutes after the block. Plasma levels of ropivacaine were analysed by high performance liquid chromatography (HPLC). RESULTS: All blocks were successful and no patient showed signs or symptoms of local anaesthetic toxicity. The plasma concentration of ropivacaine peaked at 30minutes in both arms. There was no significant difference in peak levels between US and NS-guidance (0.325+/-0.186 versus 0.356+/-0.106mug/mL). Cmax and tmax were very similar between groups (0.364+/-0.177 versus 0.344+/-0.127mug/mL, 33.75+/-15.06 versus 31.25+/-13.56min for US and NS, respectively). CONCLUSION: Plasma concentrations of ropivacaine peak around 30minutes after a femoral nerve block regardless of the technique used. No significant difference was found between US- and NS-guidance.

This is the protocol for a review and there is no abstract. The objectives are as follows: The objective of this review is to compare the effects of regional versus general anaesthesia on cognitive function after procedures other than cardiac surgery or neurosurgery in adult and in paediatric patients.