Several features of orthopedic surgery deserve special consideration – first, these patients are at increased risk for both venous emboli and fat emboli. Second, bone cement can cause hemodynamic instability. Third, tourniquets add a unique set of considerations. Orthopedic anesthesia requires facility with a wide range of techniques (GA, neuraxial, regional), comfort with the difficult airway, different ages, and a breadth of operations.
Bone Cement (methylmethacrylate)
Bone cement is made by mixing methylmethacrylate powder with a liquid methylmethacrylate monomer, which leads to an exothermic polymerization reaction (i.e. formation of polymethylmethacrylate).
The polymerization reaction causes intramedullary hypertension (500 mm Hg) which can lead to embolization of fat, marrow, and cement. Residual monomer is a vasodilator and can reduce SVR. Tissue thromboplastin may be released as well, leading to a hypercoagulable state. Femoral prosthetics are the most dangerous.
The so-called “bone cement implantation syndrome” causes hypotension, arrhythmias, hypoxia (from pulmonary HTN -> R to L shunting), and has lead to death.
Some authors recommend increasing FiO2 and giving volume prior to cementing, and sometimes measuring central pressure. The surgeons can help by creating a vent holes in the distal femur, using high-pressure lavage to remove debris, or avoiding the use of cement altogether.
Cementless prosthetics last longer than the cement-requiring counterparts, but need a longer recovery period and require healthy bone (to grow into the prosthesis), and are thus rarely used on patients > 80 years old.
Creates a bloodless field when inflated to 100 mm Hg in excess of systolic pressure.
The tourniquet can be extremely painful, and unfortunately is relatively resistant to blockade via local anesthesia (hypothesized to be due to the unmyelinated, slow-conduction C fibers [thought to mediate this pain response] which are relatively resistant to local anesthetic blockade). In fact, the pain from a tourniquet can overcome regional anesthesia to the extent that conversion to a GA may be necessary. Tourniquet pain may also manifest itself as a significant SNS response. Tourniquet pain and HTN begin after ~ 60 minutes. IV opiates may not be successful, thus consider 10 minutes of deflation, then reinflating. After 2 hours, post-operative neuropraxias may occur.
In the lower extremity, tourniquets can lead to the development of DVTs, even in minor cases (ex. Knee arthroscopy).
Cuff deflation immediately lowers CVP and MAP – washout of metabolic waste increases PaCO2, ETCO2, lactate and potassium, which can raise minute ventilation and, rarely, cause arrhythmias. Temperature (colder limb) will fall transiently (0.7 C), and a brief metabolic acidosis will ensue after cuff deflation. Deflation, which can lead to a fall in blood pressure, has been reported to cause cardiac arrests. [Valli Het al. Acta Anaesthesiol Scand 31: 279, 1987]
There is some concern about the use of a tourniquet in patients with sickle cell disease, although it has been used safely in SS children [Adu-Gyamfi Y et al. Can J Anaesth 40: 24, 1993]. If used in this patient population, ensure adequate hydration and normothermia.
Other Strategies to Minimize Blood Loss
Orthopedic surgery can e associated with up to 10U of blood loss. Pre-donation, preoperative EPO, induced hypotension, intraoperative hemodilution, aprotinin (not without risks), cell saver (expensive), and maintenance of normothermia should all be considered when developing a blood loss plan.
Many orthopedic procedures require positioning that can compromise patient safety. Positions in which the operative field is above the heart, thus introducing the risk of an air embolus. Prone positioning introduces the risk of retinal artery occlusion. Lateral positioning requires the proper use of “axillary” rolls. Controlled hypotension can increase the risk of tissue ischemia or necrosis, thus extra care should be taken to ensure proper padding and alignment. Patients with RA should avoid excessive neck flexion.
Knee arthroscopy has a low risk (~ 3%), but total hips, total knees, and lower extremity trauma operations carry up to a 50% risk. Other risk factors include immobility (> 4 days), age (> 60), use of a tourniquet, duration of procedure, and type of anesthesia. Note that unfractionated heparin has been given safely intraoperatively – a study of 989 patients given a single, 15U/kg dose of IV heparin before femur surgery showed a 7.1% incidence of asymptomatic DVTs and a 0.88% risk of clinically-significant DVTs [DiGiovanni CW et al. Clin Orthop 379: 178, 2000]. Similar results have been seen in knee arthroscopy. [Nassif JM et al. J Arthroplasty 15: 16, 2000]
For at-risk patients, SQH 8000 TID should be initiated. Interestingly, a metaanalysis including 409 patients showed that the odds ratio of developing a DVT after regional anesthesia for THR was 0.27 that following GA [Mauermann et al]. Proposed mechanisms include increased venous blood flow, antiinflammatory effects of local anesthetics, decreased platelet reactivity, attenuated increase in factor VIII and vWF, preserved postoperative antithrombin III levels, and alterations in stress hormone release. Post-operative analgesia does not reduce the risk of DVTs, however. [Sharrock NE et al. J Arthroplasty 8: 133, 1993]
Note that the effects of epidural analgesia and heparin on prevention of DVT are additive.
All patients with long bone fractures will suffer some degree of pulmonary dysfunction, but clinically-significant dysfunction occurs in only 10-15% of patients.
Usually presents with dyspnea, petechiae, and confusion within 72 hours of a long bone or pelvic fracture (i.e. in the middle of corrective surgery, or afterwards). Fat emboli cause the release of vasoactive amines and prostaglandins, mimicking ARDS (underlying pathophysiology is endothelial breakdown leading to hemorrhagic exudates in both the lungs and brain). During GA, may manifest as decreased ETCO2, decrease SpO2, increased PAP, ST changes, or R heart strain.
Mortality rate is 10-20% and there is no effective treatment, although oxygen therapy with PPV, and possibly high-dose corticosteroid therapy (in the presence of cerebral edema) may be beneficial.
(for more information, see Fat Embolism)
Common Coexisting Diseases
Importantly, the cervical spine, TMJ, and limbs (access sites) can be affected. Patients with RA have an increased incidence of ischemic heart disease (thought to be due to steroid treatment) and infections (likely due to the autoimmune nature of the disease as well as its treatment), and are often wasted and malnourished – overall, these patients are at increased risk for a poor surgical outcome. [Pellicci PM et al. J Bone Joint Surg Am 63: 342, 1981]
Rheumatoid arthritis is associated with several technical difficulties, including difficulty placing IVs and arterial cannulas (small, calcified vessels, tendency for carpal tunnel syndrome to recur), difficulty with placing IJ lines (fusion/flexion of the neck), and difficulty with intubation (atlantoaxial instability, cricoarytenoid arthritis).
Neck positioning should be as gentle as possible. Extreme cases of rheumatoid arthritis can involve both the cervical spine and the temporomandibular joint. Intubation in the setting of atlantoaxial subluxation can lead to protrusion of the odontoid process into the foramen magnum, with potentially disastrous consequences – flexion and extension films should be obtained in all RA patients with requiring steroids or methotrexate. If atlantoaxial instability exceeds 5 mm, conduct an awake fiberoptic intubation (nasal may be required if the TMJ is affected). Cricoarytenoid arthritis (hoarseness or inspiratory stridor) may lead to narrowing of the glottic opening and postextubation airway obstruction.
Patients with arthritis commonly take NSAIDs for pain, and may be at risk for gastrointestinal bleeding, renal failure, and platelet dysfunction.
These patients will have impaired lung function, and often develop aortic regurgitation and/or bundle branch blocks. Like RA patients, they carry the risk of cervical instability and often need to be intubated fiberoptically. Lumbar access (for spinal or epidural anesthesia) is usually impossible to perform.
In-hospital mortality rate is 3-10%, and one-year mortality rate is 20-25% following hip fracture (average age = 80, most are women). Most common causes of death are MI and PE.
Patients who sustain hip fractures are often hypovolemic due to occult blood loss and dehydration (reduced PO intake). Preoperatively, they are also often hypoxemic, probably due to a combination of fat emboli, atelectasis from bed rest, and in some patients congestive heart failure (elderly) or infection.
The choice between GA and regional is up to the anesthesiologist – Rodgers et al. conducted a metaanalysis of 141 trials including 9559 patients, which showed that neuraxial analgesia reduced overall mortality by about a third (OR=0.70, 95% CI 0.54 to 0.90, p=0.006). Neuraxial blockade reduced the odds of DVT by 44%, PE by 55%, transfusion by 50%, pneumonia by 39%, and respiratory depression by 59% (all p<0.001) [Rodgers A et al. BMJ 321: 1493, 2000]. Some authors suggest that at 2 months there is no significant difference in mortality.
Additionally, early ambulation appears to be critical for recovery, and epidural analgesia, femoral or fascia-iliacus blocks should be considered on that basis as well.
Total Hip Arthroplasty
Many patients undergoing total hip replacement suffer from osteoarthritis or rheumatoid arthritis (also osteonecrosis). Debilitation and limited joint mobility make it almost impossible to assess exercise tolerance – perfusion and stress testing should be strongly considered.
Consider preoperative epidural placement (for post-operative analgesia)
Total hip replacement (THR) is associated with three potentially life-threatening complications: profuse hemorrhage, VTE (most commonly during insertion of the femoral prosthesis), and bone cement implantation syndrome, thus invasive arterial monitoring should be strongly considered. Because the risk of VTE is lower during regional anesthesia [Mauermann et al], many practitioners will either conduct a regional anesthetic or add epidural analgesia on top of their general anesthetic.
The original controlled hypotension study showed reductions in blood loss from 1183 to 406 and 326 cc using volatile and IV agents, respectively (to achieve MAP of 50 mm Hg) [Thompson GE et al. Anesthesiology 48: 91, 1978]. A randomized, controlled study of 40 patients undergoing hypotensive TIVA vs. hypotensive epidural analgesia for THR showed reductions in less blood loss in the epidural group despite similar MAPs [Eroglu A et al. J Clin Anesth 17: 420, 2005]. Sharrock et al. randomized 40 patients to MAP = 50 vs. MAP = 60 and found a statistically-significant reduction in blood loss at the lower pressures (179 vs. 263, p = 0.004) [Sharrock et al]. Hip arthoplasties are complicated by positioning, as they are most often done in the lateral decubitus position (V/Q mismatch, possible injury to the brachial plexus and compression of the axillary artery).
Because of the risk of fat embolism, when using cement, some authors recommend pulmonary artery pressure monitoring with PA pressures in excess of 200 dyn x s / cm5 mandating postponement of the second side. The availability of uncemented hip arthroplasties obviates PAP monitoring.
Major concern is blood loss. Controlled hypotension is sometimes used to minimize blood loss, improve cementing, and decrease the duration of surgery. Anticipate significant transfusion and consider preoperative EPO, intraoperative aprotinin (does not seem to increase risk of DVTs), and the using cell saver. Normothermia (which maintains coagulation) appears to reduce blood loss.
Minimally Invasive Arthoplasty
Computer-assisted surgery in conjunction with minimally invasive techniques helps reduce post-operative pain and expedites discharge and recovery. In fact, some techniques are amenable to a 24h discharge. The most common anesthetic regimen for these techniques is epidural + propofol + LMA.
GA with facemask vs. LMA and SCh or mivacurium
Outpatient procedure. General anesthesia is usually combined with a pneumatic tourniquet, although some centers use neuraxial anesthesia. A 3-in-1 femoral nerve + lateral femoral cutaneous + psoas compartment block can be combined with local anesthesia and sedation as well. Post-operative pain control is critical to good recovery, thus intraarticular local anesthetics should be considered and combined with IA morphine and/or steroids, or IV ketorolac.
Total or Partial Knee Replacement
Most patients have bilateral disease and would prefer a single operation, however in the orthopedic surgery community there is substantial debate about the wisdom of performing bilateral knee operations as the surgical risks are generally higher (ex. postoperative confusion, cardiopulmonary complications, and increased need for blood).
Some patients will tolerate a regional anesthetic along with sedation, although many will require GA (b/c of the tourniquet). Note that tourniquets increase the risk of DVT/PE [Wauke K et al. Arch Orthop Trauma Surg 122: 442, 2002], and tourniquet release is associated with an embolic shower that can increase PVR. Bone cement implantation syndrome is less likely than with hip arthroplasty, but is still possible with the use of cement in the distal femur (RARE when used in the tibia, fibula, or patella).
Epidural catheter placement can significantly improve post-operative analgesia, although a 48h femoral sheath catheter is also a reasonable option. Knee replacements are painful post-operatively (worse than THR), and good analgesia is necessary for rehabilitation/recovery.
Note that while intraoperative blood loss is minimal due to the tourniquet, each knee will drain on average 500 to 1000 postoperatively, thus 24 hr monitoring may be necessary.
Upper Extremity Operations
Usually performed in the “beach chair” position but can also be done in lateral decubitus position. Interscalene approach to a brachial plexus block is ideal. If GA is used, significant relaxation must be achieved. Occasionally, the surgeon may request controlled hypotension.
Carpal tunnel release is one of the most common procedures requiring anesthesia – options include IVRA (Bier), as well as propofol/desflurane + LMA.
Hand operations that take more than an hour can be done with a brachial plexus block. For operations below the elbow (ex. all hand surgery), the axillary approach is preferred.
Posterior cervical decompression is either performed in the sitting position (risk of air embolism) or in the prone position (external pressure on the eyes), both of which complicate anesthetic management. Intubation should be expected to be difficult, and awake FOB should be considered. Some authors recommend lightening the anesthetic once the patient is positioned, asking the patient to move his/her toes and open and close his/her hands, which, along with spontaneous breathing, ensures the c-spine is still intact. Because of the risk of kinking, consider an armored endotracheal tube.
SSEPs are often used during cervical spinal surgery (relatively high risk of quadriplegia), in which case TIVA should be used.
When caring for patients with RA, consider obtaining a full set of cervical spine films, intubating with a FOB, maintaining the neck in neutral position, and minimizing intraoperative fluid intake. Post-operatively, keep the head up for 3 to 5 hours to minimize the upper airway obstruction (presumably from upper airway edema caused by trauma during intubation, excessive fluid, and prolonged dependency. Cervical spinal surgery has been performed using local anesthesia and should be considered.
Scoli/deformity patients often have restrictive lung disease and may have other congenital abnormalities (ex. heart disease, neuromuscular disease [possible malignant hyperthermia]). Particular concerns for these operations are positioning, IV access, blood loss, neuromonitoring, and post-operative pain management.
SSEPs, EMGs, and MEPs are common. If neuromonitoring is used, TIVA is indicated, although partial paralysis (monitor with TOF) will still allow EMG to be used. Wake up tests are the gold standard but are less common. Their major advantage is that they are unaffected by anesthetic agents and also will allow one to monitor the anterior cord, which is at risk during distraction (SSEPs only monitor the posterior cord).
Because the potential for blood loss and hemodynamic stability is high, adequate IV access (consider a central line), and arterial catheterization should be considered.
Pulmonary disorders are the most common post-operative complications. Post-operative blindness is extremely but is one of the most feared complications – risk factors include hypotension, anemia, massive intraoperative blood loss, and duration of surgery.
Many of these patients are already on opiates, thus post-operative pain control can be difficult. Consider giving ketamine 0.25 mg/kg followed by 2-2.5 ucg/kg/min, a dose which has been shown to improve pain scores, reduce nausea, decrease narcotic requirements, and at the same time does not elicit hallucinations.
Can range from minimally invasive procedures to massive operations as in the thoracic spine, in which case the considerations (see above) are the same. Can perform an anesthetic with lumbar epidural anesthesia alone (less bleeding and improved post-operative analgesia [Joshi GP et al. Anesth Analg 80: 511, 1995]). If not done beforehand, and epidural catheter can always be placed intraoperatively by the surgeon.
Allograft or Autograft Transplantation Surgery
Allografts (from donors) or autografts (from the fibula)can be used to bridge bony gaps left after tumor removal, trauma, or due to osteonecrosis. Many patients undergoing these operations are highly debilitated, thus putting them at increased risk.
The procedures themselves can last from 2-10 hours. Intentional hemodilution and controlled hypotension should be considered as these can be bloody procedures and they are reconstructive in nature. The benefits of controlled hypotension must be considered in light of the desire to maintain cardiac output (and thus blood flow to the new graft).
Pelvic and Sacral Resections
Usually done for removal of cancer. Most often performed in the lateral or prone positions. Blood and heat losses can be considerable. Consider a lower extremity pulse oximeter. Provision of adequate post-operative analgesia can be difficult.
Pediatric Orthopedic Surgery
Many of these children have undergone multiple operations/hospitalizations and have suffered significant social isolation due to pain, disability, and deformity.
Preoperative evaluation should focus on birth history as many of these patients were premature and may have bronchopulmonary dysplasia, tracheomalacia, irritable airways, and lung dysfunction. FOB or regional techniques deserve consideration. Children with CP are at increased risk for GERD and many will have recurrent pneumonias. They also may have hypothalamic dysfunction predisposing them to hypothermia. Contractures make intraoperative positioning difficult, and ligamentous laxity increases the risk of intraoperative neurologic injury (ex. quadriparesis).
Juvenile Rheumatoid Arthritis
Airway can be very difficult due to cervical spine fusion, hypoplastic mandible (premature closure of epiphyseal plates). Unfortunately, many of these children also have lumbar hyperlordosis, complicating the use of neuraxial techniques.
Regional in Pediatric Orthopedics
Much easier to administer regional anesthesia to sedated children, and the potential for nerve injury is not supported by the literature [Uguralp S et al. J Pediatr Surg 37: 610, 2002; Krane EJ et al. Reg Anesth Pain Med 23: 433, 1998], thus, unlike adults, these patients should be sedated.
Regional Anesthesia for Orthopedic Surgery
Most of the deep shoulder is innervated by C5/6, thus an interscalene brachial plexus block usually suffices. Occasionally an intercostobrachial nerve block (SQ injection) must be added to cover the posterior shoulder. Despite the absence of any major trauma or fluid shifts, shoulder surgery can be complicated by bradycardia and/or hypotension, both of which occur in ~ 20% of cases [Roch J and Sharrock NE. Reg Anesth 16: 64, 1991] and can be treated with atropine (not glycopyrrolate) and IV fluids, respectively. Interestingly, in a prospective, randomized trial of 150 patients, Liquori et al. found that prophylactic beta blockade (metoprolol titrated to HR < 60) reduced the incidence of bradycardia-induced hypotension in shoulder surgery from 28% to 5% (glycopyrrolate had no significant effect) [Liguori et al]. A retrospective review by Kahn et al., however, found no association with preoperative beta blockade and bradycardic-hypotensive events [Kahn et al].
Elbow and Hand
Elbow operations can be performed under either interscalene or axillary blocks. Intercostobrachial (T1-2) blocks in the axilla may be necessary to supplement the axillar block of medial incisions are made. For surgery of the medial hand/forearm, an axillary brachial plexus block (C7-T1) may be preferable because the interscalene approach may not provide complete coverage. An alternative to the axillary brachial plexus block is the coracoid block (can be used for the elbow, forearm, or hand). The major advantages of the coracoid block are its prominent bony landmarks, and its distance from the lungs, which make it easier to perform and reduce the risk of pneumothorax. Peripheral nerve blocks (bupivacaine, ropivacaine) can also be used, mainly to provide postoperative pain relief.
In addition to spinal, epidural, or CSE blocks, one can use femoral, sciatic, or combination blocks for operations involving the thigh or leg. One must take into account tourniquet time when considering depend on the site of the surgery and the necessity for a tourniquet. For operations below the knee, sciatic blocks are adequate if tourniquets are not used.
Femoral nerve blocks can be performed preoperatively or postoperatively, and are particularly effective for hip or femur fractures as well as for knee surgery.
Knee arthroscopy is usually performed under spinal anesthesia or with CSE, the most common downside being TENS (mostly with lidocaine) and the least common but most severe downside being hemodynamic catastrophe. Three-in-one blocks (i.e., femoral plexus block) may also be used provided that tourniquet times are not prolonged.
Ankle surgery cannot be reliably performed using an ankle block. Epidural anesthesia is satisfactory but can be time consuming (~ 30 minutes to dose the epidural appropriately), although these times can be reduced by addition of an opiates, epinephrine, clonidine, or bicarbonate. Spinal anesthesia is much more rapid. Regional blockade can be accomplished by using a sciatic or popliteal block alone, as the sciatic innervates all the deep structures of the ankle.
Forefoot procedures can be performed under ankle or midtarsal block, or by blocking the sciatic and femoral nerves more proximally. Operations involving the medial aspect of the foot require a block of the saphenous branch of the femoral nerve (at the level of the ankle or above). Blocks, however, may preclude the use of thigh tourniquets.
Of all the joints, knees are the most painful post-operatively. Potential modalities should include epidural analgesia, nerve catheters, intra-articular injections, NSAIDs (although not routinely recommended due to concerns about renal disease [Feldman et al., Ann Int Med 126: 193, 1997]), and, as a last resort, IV opiates.
The major concern with epidural analgesia is the risk of bleeding when combined with low molecular weight heparin (there is much less of, or no risk when combined with aspirin, coumadin, or unfractionated heparin). Another, less-common but equally serious concern is that of occult compartment syndrome (particularly in trauma patients), thus if the likelihood is high, epidural analgesia may need to be avoided.