1. Discuss hypotensive epidural anesthesia for total hip replacement.

2. Make informed decisions about the use of mepivacaine for spinal anesthesia.

3. Apply knowledge of anesthesia and analgesia for total knee replacement.

4. Review evidence to support the use of upper-extremity anesthetic blocks.

5. Analyze techniques to ensure the success of upper-extremity anesthetic blocks, review the pharmacology of the brachial plexus, and list possible complications associated with peripheral nerve blockade.

Regional Techniques for Orthopedic Surgery
Gregory A. Liguori, MD, Clinical Associate Professor of Anesthesiology, Weill Medical College of Cornell University, and Director, Department of Anesthesiology, and Anesthesiologist-in-Chief, Hospital for Special Surgery, New York, NY

Hypotensive epidural anesthesia for total hip replacement: total hip replacement associated with substantial blood loss (≤1 L) and high rates of deep venous thrombosis (DVT) and pulmonary embolism (PE); neuraxial anesthesia traditionally associated with lower rates of DVT and PE, possibly due to inhibition of inflammatory mediators or enhanced or selective blood flow in lower extremities; hypotensive anesthesia associated with less blood loss (related to blood pressure [BP], not cardiac output); technique involves extensive sympathetic block via epidural or combined spinal-epidural (CSE), low-dose epinephrine infusion, and placement of radial artery lines (to monitor BP)

Extensive sympathetic block: suppresses levels of endogenous catecholamines, epinephrine, and norepinephrine; blocks cardiac accelerator fibers (T1 through T4); leads to decreases in heart rate (HR), central venous pressure (CVP), BP, cardiac output, and stroke volume; addition of epinephrine infusion controls circulation; Sharrock (1992) compared phenylephrine and epinephrine; found cardiac index maintained with epinephrine, but dropped significantly with phenylephrine; starting low-dose epinephrine alone results in increases in HR and CVP, mild decrease in BP, and increase in cardiac output and stroke volume; combination of extensive epidural block, epinephrine infusion at low rate, and close monitoring results in stable HR and CVP, significantly decreased BP, stable cardiac output, and stable stroke volume

Efficacy: significantly less blood loss and fewer blood transfusions; bone-cement interface improved in short term; significantly lower rates of DVT, PE, and mortality

Safety: no increased incidence of stroke, myocardial infarction (MI), or acute renal failure; study looked at total hip replacement under hypotensive epidural anesthesia in patients >70 yr of age with either cardiac disease, hypertension, or diabetes; low BP technique compared with normotensive technique; no differences in cognitive outcomes (at 1 wk and 4 mo) after surgery or in medical complications between groups

Contraindications: significant carotid stenosis; renal insufficiency; severe aortic stenosis (AS); idiopathic hypertrophic subaortic stenosis (IHSS)

Use of mepivacaine as spinal anesthetic: mepivacaine, isobaric lidocaine, isobaric bupivacaine, 2-chloroprocaine, and narcotics (eg, fentanyl, hydromorphone) not approved for spinal anesthesia

Safety and toxicity of local anesthetics (animal studies): Japanese study (Kasaba et al, 2003) in snails found mepivacaine had least adverse effects on growth cones; another Japanese study evaluated growth cones in chicks and found mepivacaine safest drug and lidocaine most toxic; study (Takenami et al, 2004) in rats concluded histologic damage and neurofunctional impairment significantly more severe with highly concentrated lidocaine than with mepivacaine or prilocaine; Gentili study (1980) looked at microscopic evaluation of nerve injury in rats; with intrafascicular injection, most damage occurred with tetracaine, procaine, and lidocaine; least damage with mepivacaine and bupivacaine

Speaker’s retrospective evaluation: looked at outcomes after mepivacaine spinal anesthetic over 3 yr; mean dose ≈52 mg (range, 15-75 mg); 24 cases of new postoperative neurologic findings; 10 cases involved mepivacaine (7 peripheral neuropathies; 1 case of spinal cord needle trauma; 1 related to epidural infusion; 1 unrecognized spinal stenosis)

Efficacy: onset of action, 2 to 3 min; dose-dependent duration of action; high success rates; speaker’s study of dose- response methodology for knee arthroscopy found 45 and 60 mg mepivacaine adequate for most patients; duration of action ≈2 hr for lower extremity blocks and 90 to 120 min for motor blocks; higher doses of isobaric mepivacaine (60 and 80 mg) for anterior cruciate ligament (ACL) reconstruction showed dose-dependent duration of action on sensory and motor function

Side effects: transient neurologic symptoms (TNS)—in speaker’s prospective study comparing mepivacaine to lidocaine, mepivacaine shown to have lower incidence of TNS; later studies showed no difference between lidocaine and mepivacaine in incidence of TNS; subsequent studies found 0% to 30% incidence of TNS with mepivacaine; YaDeau (2005) performed prospective study and found 6% incidence of TNS with mepivacaine spinal

Anesthesia and analgesia for total knee replacement: anesthesia—spinal; epidural; general; CSE; peripheral nerve blocks (PNBs); analgesia—patient-controlled epidural analgesia (PCEA); intravenous (IV) patient-controlled analgesia (PCA); femoral nerve block; sciatic nerve block; various combinations of catheters and blocks; considerations—patient; surgeon; anesthesia provider; safety and efficacy; thromboprophylaxis; rehabilitation schedule

Hospital for Special Surgery (HSS): generally use neuraxial regional anesthesia; surgeons use warfarin or aspirin for thromboprophylaxis; patient out of bed on morning of first postoperative day

Capdevila study (2005): continuous epidural infusion and continuous femoral nerve block associated with less pain and better rehabilitation than IV PCA; complications higher with epidural infusions than with continuous femoral nerve block; however, anesthetic in epidural infusion was 1% concentrated lidocaine (causes dysesthesias and arterial hypotension)

Other studies: Barrington (2005) compared continuous femoral nerve block to continuous epidural; both provided equivalent pain relief at rest and in motion; narcotic use higher with continuous femoral nerve block, but more nausea in epidural group; postoperative range of motion and rehabilitation similar; Salinas (2006) compared single-shot femoral nerve block to continuous femoral nerve block; both placed after resolution of spinal anesthesia; after day 1, continuous femoral nerve block associated with lower pain scores than single shot; hospital length-of-stay and rehabilitation milestones comparable

Techniques at HSS: PCEA plus single-shot femoral nerve block using low concentration local anesthetic; YaDeau found femoral nerve block associated with improved flexion and pain scores through postoperative day 2

Upper-Extremity Blocks: Making Them Work and Preventing Complications
Joseph M. Neal, MD, Clinical Professor of Anesthesiology, University of Washington School of Medicine, and Staff Anesthesiologist, Virginia Mason Medical Center, Seattle

Supportive evidence: interscalene, infraclavicular, and axillary blocks (compared to fast-track general anesthesia) provide better analgesia, decreased opioid side effects, fewer instances of delayed discharge due to nausea and vomiting, and fewer unplanned admissions; once block has worn off, no discernible difference between regional technique and general anesthetic technique; extending block with perineural catheter can be done quickly (and surgeon can bill for procedure), but less effective than single-shot or continuous analgesia, and recent evidence suggests perineural catheter may do harm (particularly with subacromial infusions around fresh joints and cartilage); studies from orthopedic literature indicate continuous subacromial and intra-articular infusions as effective as suprascapular nerve block or interscalene block; however, studies usually unblinded and nonrandomized

Nerve localization: no evidence that choice of technique influences efficacy or safety

Ultrasonography (US): most studies suggest US-guided block at least as fast as nerve stimulation-guided block; however, studies fail to include time required to set up, perform preliminary scan, and place sheath over probe; onset of anesthesia varies; placing local anesthetic near nerve increases concentration gradient, reducing onset time by 2 to 4 min; block quality also variable; no studies proving US safer than other techniques (case reports of complications increasing); studies found no major differences in success rates whether peripheral nerve stimulation (PNS)- guided or US-guided axillary blocks used

Interscalene or supraclavicular block: transarterial, paresthesia, or PNS-type techniques; at origins of brachial plexus, single injection effective; where brachial plexus divides into cords and terminal nerves, 2 to 3 stimulations or injections better than single stimulation; 4 stimulations slightly better but require more time; ideal axillary technique includes injection near radial, musculocutaneous, and median nerves (less important to inject near ulnar nerve)

Infraclavicular block: also better with dual stimulation than single stimulation, both with US and PNS; one injection at posterior cord; studies consistently show infraclavicular block superior to axillary block for surgical anesthesia

Continuous perineural catheter: no evidence that continuous injection techniques increase complications (eg, nerve injury, intravascular injection, infection); shown to promote earlier discharge; may improve rehabilitation; more labor- intensive than single-shot block; more difficult (especially without aid of US) to place catheter around brachial plexus than around femoral nerve; patients prefer ambulatory discharge if designated provider available 24 hr/day by telephone

Selective nerve blocks: either 1) not part of brachial plexus (but involved with upper-extremity surgery), or 2) part of brachial plexus but, because of branching pattern or ineffective spread of local anesthetic, can be missed with regional anesthetic or require supplement

Suprascapular nerve block: primarily sensory nerve; isolated block reduces pain in shoulder arthroscopic procedures under general anesthesia; technique involves placing needle toward scapular spine near suprascapular notch, and blindly injecting 5 to 10 mL of local anesthetic; decreases nausea and vomiting and rate of unplanned admission; useful in recovery, for patients in pain despite seemingly effective interscalene block

Antebrachial cutaneous block: primary anesthesia or rescue anesthesia for volar forearms; subcutaneous infiltration in lower part of upper arm blocks medial antebrachial nerve; lateral antebrachial nerve blocked at cutaneous terminus of musculocutaneous nerve in lateral forearm; does not require placing needle toward peripheral nerve that may be partially blocked and perhaps more prone to injury

Supraclavicular nerve: terminal branches from superficial cervical plexus innervate cape of shoulder; blocked by interscalene approach, due to proximal spread of local anesthetic; more distal block likely to miss supraclavicular nerve; superficial cervical plexus block often beneficial

Pharmacology of brachial plexus: local anesthetics and adjuvants often affect central and peripheral nerves differently (eg, relationship between dose and duration of action); selection of local anesthetic for brachial plexus block ultimately determined by desired length of block (eg, short-acting, 2-chloroprocaine; intermediate-acting [4-6 hr], lidocaine or mepivacaine; long-acting, bupivacaine or ropivacaine); bupivacaine and ropivacaine not equipotent (0.75% ropivacaine required to obtain same block characteristics as 0.5% bupivacaine); for infusion, 0.2% to 0.15% ropivacaine comparable to 0.15% to 0.125% bupivacaine; some evidence of greater preservation of motor function with ropivacaine than with bupivacaine; PNB often may be overdosed, but from practical standpoint, “nothing wrong with overdosing PNBs as long as you don’t have an accident” (eg, nerve damage, intravascular injection); ultra–long–acting local anesthetics not currently available but highly effective

Adjuvants: mostly used with intermediate- and long-acting drugs; however, common adjuvants (eg, epinephrine, clonidine) have little effect on long-acting local anesthetics (cleared at same time or before long-acting local anesthetic); epinephrine—prolongs blockade; acts as intravascular marker; decreases rapid uptake of local anesthetics; increases intensity of block; negative effects include tachycardia and decreased peripheral nerve blood flow (reducing concentration to 2.5 µg/mL eliminates tachycardia and decreases duration by only 10-15 min); clonidine—in relatively small doses, prolongs anesthesia and analgesia by ≈50%; if total dose <150 µg, patient typically does not experience sedation or hypotension; expensive; no better than epinephrine as adjuvant; not recommended for infusion (does not prolong effect or decrease breakthrough pain; increases motor block); buprenorphine—0.3-mg dose increases duration of block

Alkalinization: sodium bicarbonate added to lidocaine epidural increases speed of onset by 5 to 10 min; however, addition of sodium bicarbonate to lidocaine or mepivacaine PNB does not decrease onset time; animal studies show decreased duration and intensity of block; addition of epinephrine results in <1-min increase in speed of onset; significant effect only when added to commercially prepared lidocaine with epinephrine (preparations highly acidic)

Complications: higher incidence of death and cardiac arrest with neuraxial block, compared to PNB, but risk for seizure 5 times more likely with PNB than with epidural block; PNB damages nerves less often than does spinal anesthesia; hemidiaphragmatic paresis—if patient cannot withstand 25% to 30% reduction in pulmonary function, regional anesthesia above clavicle contraindicated; pneumothorax—decreased incidence with modern approaches to placing supraclavicular block (eg, plumb-bob, subclavian perivascular) using US; unintended destination—be vigilant and aggressive in resuscitation; nerve injury—80% to 85% of perioperative nerve injury not caused by anesthesia (focus on surgical and patient-related causes); causes include mechanical trauma, ischemic injury, and chemical injury; no evidence that sharp needle better or worse than blunt needle; if perineural barrier broken, normal clinical concentrations can become toxic (exacerbated by epinephrine)