Anesthesiology

Amputation of the Leg, Above the Knee and Below the Knee

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What the Anesthesiologist Should Know before the Operative Procedure

Patients present for amputations of the lower extremity for a variety of reasons, including, but not limited to, infection, vascular compromise, tumors, and trauma. The underlying reason for the amputation should be elucidated, if it is not obvious. The primary reason that the amputation is required will result different approaches to care, prior to proceeding to the operating room. The different approaches to patient evaluation are discussed in other sections of this chapter.

1. What is the urgency of the surgery?

What is the risk of delay in order to obtain additional preoperative information?

Many times, the urgency to proceed with amputation surgery is high. Patients often have comorbidities that have contributed to the need for amputation of a lower extremity. These comorbidities (e.g., diabetes mellitus, peripheral arterial disease) often are associated with significant systemic effects that may complicate the anesthesia.

Emergent:Patients presenting for emergent amputation surgery may be septic, have significant traumatic injuries, or have major vascular bleeding or compromise to the affected extremity. Delaying surgery at this point for further work-up may result in mortality. For infected or necrotic tissue, early and aggressive removal is associated with improved clinical outcome. Therefore, the risk of delay is very high.

Urgent: Patients presenting for urgent amputation surgery have similar comorbidities as those presenting for emergent surgery, but usually they are less severe. Other patients presenting for urgent surgery may have complications from long-standing diabetes that may be addressed prior to surgery (e.g., evaluation of renal function). Often, urgent surgeries for amputations may be delayed for several hours to better prepare a patient to decrease risk (e.g., dialysis for hyperkalemia or fluid overload).

Elective: Few amputation surgeries are truly elective. If a patient has a slow growing tumor, surgery may be delayed for days to weeks depending on the type of tumor. Of course, even for these operations, risk of a prolonged delay (metastasis) may be too great to proceed with an intervention requiring weeks to months of delay (e.g., stent placement for coronary artery disease).

2. Preoperative evaluation

Peripheral artery disease: This disease results in obstructive disease in the arterial system, usually caused by atherosclerosis. Atherosclerosis in the distal extremities is highly associated with diabetes mellitus, smoking, hypertension, and/or dyslipidemia. Evaluation of complications from these diseases is therefore warranted.

Other atherosclerotic disease: Evaluation for coronary artery disease, carotid artery disease, and renal artery disease should also be undertaken as these may be associated with peripheral artery disease as well.

Diabetes mellitus: Complications of diabetes, aside from peripheral neuropathy, should be actively evaluated including coronary artery disease, hypertension, carotid artery disease, hyperglycemia, gastroparesis, and renal insufficiency. Acute evaluation of blood sugar and electrolytes perioperatively is also indicated.

Trauma: Trauma patients should be evaluated for other sites of injury (airway, intrathoracic, intra-abdominal, intracranial) as well as for signs or symptoms of shock (tachycardia, hypotension, pallor, oliguria, tachypnea, altered level of consciousness). Evaluation of hemorrhage and acid-base disturbance is necessary and appropriate resuscitation in also required.

Infections/sepsis: Sepsis results in an excessive systemic inflammatory response leading to multiorgan damage. The more organ systems that are involved, the higher is the mortality. Specific evaluations of cardiovascular, neurologic, and renal systems are warranted as derangements in these are associated with the highest predictors of mortality. Other signs/symptoms of early impairment secondary to systemic infection include hypothermia, respiratory alkalosis, edema, hypotension, increased cardiac output, and lactic acidosis.

Medically unstable conditions warranting further evaluation include hypovolemia,unstable angina, loss of airway, and severe metabolic derangements.Delaying surgery may be indicated if resuscitation post-trauma is notcomplete or dialysis is required.

3. What are the implications of co-existing disease on perioperative care?

Perioperative evaluation Is highly dependent on the reason for amputation:

Peripheral artery disease

This disease results in obstructive disease in the arterial system, usually caused by atherosclerosis. Atherosclerosis in the distal extremities is highly associated with diabetes mellitus, smoking, hypertension, and/or dyslipidemia. Evaluation of complications from these diseases is therefore warranted.

The perioperative risk reduction strategy is to evaluate anticoagulation status. Many patients will be on an anticoagulant, which may or may not preclude regional anesthesia.

Other atherosclerotic disease

Evaluation for coronary artery disease, carotid artery disease, and renal artery disease should also be undertaken as these may be associated with peripheral artery disease as well.

Diabetes mellitus

Complications of diabetes, aside from peripheral neuropathy, should be actively evaluated including coronary artery disease, hypertension, carotid artery disease, hyperglycemia, gastroparesis, and renal insufficiency. Acute evaluation of blood sugar and electrolytes perioperatively is also indicated.

Trauma

Trauma patients should be evaluated for other sites of injury (airway, intrathoracic, intra-abdominal, intracranial). Evaluate for signs of symptoms of shock (e.g., tachycardia, hypotension, pallor, oliguria, tachypnea, altered level of consciousness). Evaluation of hemorrhage and acid-base disturbance is necessary and appropriate resuscitation in also required.

Infections/sepsis

Sepsis results in an excessive systemic inflammatory response leading to multiorgan damage. The more organ systems involved, the higher is the mortality. Specific evaluations of cardiovascular, neurologic, and renal systems are warranted as derangements in these are associated with the highest predictors of mortality. Other signs/symptoms of early impairment secondary to systemic infection include hypothermia, respiratory alkalosis, edema, hypotension, increased cardiac output, and lactic acidosis.

b. Cardiovascular system

Evaluation of the cardiovascular system prior to anesthesia for amputations will be dependent on the primary reason the patient is presenting for amputation.

Acute/unstable conditions such as hypovolemia status post trauma may contraindicate neuraxial regional anesthesia (e.g., spinal). Acute myocardial ischemia should be treated according to American Heart Association (AHA)/American College of Cardiology (ACC) guidelines.

For baseline coronary artery disease or cardiac dysfunction, management of chronic cardiac conditions (and the decision about timing of surgery should also be managed according to AHA/ACC guidelines. Aortic stenosis is an example of a chronic disease state that may contraindicate spinal anesthesia. Goals of management for patients with baseline coronary artery disease or cardiac dysfunction will not stray from standard best practice of minimizing myocardial oxygen demand while maintaining adequate oxygen delivery to the myocardium.

c. Pulmonary

Chronic obstructive pulmonary disease (COPD)

Perioperative evaluation should include severity of disease, typically assessed with a preoperative assessment of symptoms (e.g., dyspnea, cough, wheezing, prior hospitalizations, exacerbations requiring hospital admissions/intubation and/or systemic steroid therapy), functional capacity, and recent pulmonary infections. Laboratory examination such as arterial blood gases, pulmonary function testing, or chest radiography is rarely necessary unless they change management (rule out recent pneumonia or assess for reversibility with bronchodilator therapy).

Perioperative risk reduction includes maintaining all chronic medications, aggressive pulmonary hygiene, and ideally avoiding instrumentation of the airway, to decrease the risk of perioperative pulmonary complications.

Obstructive sleep apnea (OSA)

Patients with sleep apnea should have the severity of the disease assessed and appropriate strategies developed to reduce the potential for postoperative exacerbation of their disease by opioid-induced respiratory depression. They should continue the use of their CPAP therapy in the perioperative period.

Reactive airway disease (asthma)

The perioperative evaluation and risk reduction strategies are similar to those for patients with COPD.

d. Renal-GI:

The goals of management for patients with baseline renal or gastrointestinal disease are not significantly altered by amputation surgery.

e. Neurologic:

Acute issues: Prior to performing neuraxial regional anesthesia, evaluate the patient for signs/symptoms of increased intracranial pressure (e.g., bradycardia, hypertension, respiratory depression, and/or headache).

Chronic disease: Chronic neuropathy should be evaluated prior to performing regional anesthesia in most cases. However, in patients requiring amputation, chronic neuropathy is less of a concern due to the nature of the surgery.

f. Endocrine:

Diabetes mellitus and its complications are a major concern in patients requiring amputation, because complications from long-standing diabetes often require amputation. Usually, by the time the patient has complications from diabetes that require amputation, other organ systems in addition to the peripheral circulation are also compromised. Chronic renal insufficiency or renal failure should be evaluated. The cardiovascular system should be evaluated by history and physical exam. Tight blood glucose control should be undertaken throughout the perioperative arena.

g. Additional systems/conditions which may be of concern in a patient undergoing this procedure and are relevant for the anesthetic plan (eg. musculoskeletal in orthopedic procedures, hematologic in a cancer patient)

If the reason for amputation includes any infective process (e.g., gangrene with septicemia), regional anesthesia may not be the anesthetic of choice. Regional anesthesia has the potential to spread infection directly with the needle. There is limited evidence in this area, but nevertheless, the potential risk of infection compared to the risk of general anesthesia must be weighed when choosing an anesthetic.

4. What are the patient's medications and how should they be managed in the perioperative period?

Most cardiovascular and antimicrobial medications can be continued perioperatively. Although herbal medications can decrease hemostasis, they do not contraindicate most regional anesthesia. Oral hypoglycemics can be withheld the day of surgery (e.g., metformin), but strict blood sugar control is then recommended. Patient using insulin should be given half the normal dose of insulin while NPO on the day of surgery.

h. Are there medications commonly seen in patients undergoing this procedure and for which should there be greater concern?

Anticoagulants (type, dosage, timing) should be evaluated prior to placing any central neuraxial or peripheral nerve blocks. Full regional anesthesia and anticoagulation guidelines are outside the scope of this chapter but can be found easily at www.ASRA.org. If the patient is receiving clopidogrel and/or aspirin to reduce the chance of restenosis of intracoronary stents, then discussion with the cardiologist and surgeon in necessary to develop an appropriate perioperative anticoagulation strategy.

i. What should be recommended with regard to continuation of medications taken chronically?

As mentioned, chronic medications can be continued with the exception of oral medications taken for diabetes. Diabetic medication recommendations are given above.

j. How To modify care for patients with known allergies -

Avoid drugs or products to which the patient is allergic.

k. Latex allergy- If the patient has a sensitivity to latex (eg. rash from gloves, underwear, etc.) versus anaphylactic reaction, prepare the operating room with latex-free products.

If the patient has a sensitivity to latex or a history of anaphylactic reaction, prepare the operating room with latex-free products.

l. Does the patient have any antibiotic allergies? (common antibiotic allergies and alternative antibiotics)

Avoid drugs or products to which the patient is allergic. A standard antibiotic allergy includes penicillin/cephalosporins; an alternative antibiotic choice is vancomycin or clindamycin. The preferred choice is cefazolin 1 to 2 g IV. If the patient has a beta-lactam allergy, the choice is clindamycin 600-900 mg IV or vancomycin 1 g IV. If there is a known history of MRSA, the choice is vancomycin 1 g IV.

m. Does the patient have a history of allergy to anesthesia?

Malignant hyperthermia (MH)

For documented MH, avoid all trigger agents such as succinylcholine and inhalational agents. The proposed general anesthetic plan includes total intravenous anesthetic (TIVA) and ensuring that an MH cart is available. When there is a family history or risk factors for MH, follow the same proposed general anesthetic plan.

Local anesthetics/muscle relaxants

Continuous muscle relaxation is usually not indicated for amputations and can therefore be avoided. For intubation, consider using a muscle relaxant in a different class if the patient has an allergy (depolarizing versus nondepolarizing or benzylisoquinoline versus amino steroid). Many allergies related to local anesthetics are associated with the epinephrine used as an additive. Careful history can help to differentiate between a true allergy and a reaction to epinephrine. If there is a true allergy to local anesthetics, consider using a local anesthetic in a different class (amide versus ester).

5. What laboratory tests should be obtained and has everything been reviewed?

Laboratory tests should be based on the patient's comorbidities. A type and screen and a hematocrit can be useful in patients undergoing amputations and should be ordered if indicated by the patient's condition. If the patient has been on anticoagulants, the appropriate coagulation panel should be ordered.

Intraoperative Management: What are the options for anesthetic management and how to determine the best technique?

Anesthesia for amputations can be performed with general anesthesia, regional anesthesia, or a combination of both. Patients presenting for amputation surgery can have many comorbidities that need to be considered when choosing an appropriate anesthetic plan.

a. Regional anesthesia

This offers many benefits in patients presenting for amputation surgery. Neuraxial and/or peripheral nerve blocks can provide complete anesthesia to the surgical extremity as well as provide analgesia postoperatively. Emerging evidence shows regional anesthesia may also decrease chronic pain associated with amputations.

Spinal

Subarachnoid blocks can be performed with a variety of local anesthetics. The most common local anesthetic used for amputation surgery of the lower extremity is bupivacaine. Bupivacaine 0.5% or 0.75% is typically dosed at 10 to 15 mg for below the knee amputation (BKA) or above the knee amputation (AKA). This dose will provide adequate anesthesia for 2 to 4 hours, which will usually outlast the surgical time requirements for an amputation. The addition of an adjuvant such as opioids (fentanyl 10 to 25 mcg or preservative-free morphine 100 to 200 mcg) provides an even denser block of longer duration. The addition of epinephrine (5 to 50 mcg) will prolong the duration of the spinal anesthetic if a longer block is desired.

Benefits: Subarachnoid block with local anesthetics is a common method to apply dense, reliable anesthesia to the surgical site. Most anesthesiologists are able to perform spinal anesthesia with ease. The failure rate of spinal anesthetics is very low.

Drawbacks: Patients with preexisting infections (sepsis/bacteremia) or local skin infections at the spinal site may not be appropriate candidates due to the risks of direct spread of the infection to the intrathecal space from needle trauma. Additionally, coagulation status must be assessed where appropriate due to the risks of spinal or epidural hematoma. Patients who are hypovolemic or hemodynamically unstable may not tolerate the variations in blood pressure that are associated with spinal anesthetics.

Issues: Spinal anesthesia has the potential to provide some preemptive analgesia to the amputation site and may decrease central sensitization from nociception elicited by the amputation surgery.

Epidural anesthesia

Similar to spinal anesthesia, epidural anesthesia can provide anesthesia and/or analgesia to the surgical site.

Benefits: Epidural analgesia may be provided prior to surgery to limit postsurgical complications from amputation and phantom-limb pain (PLP). Studies suggest that epidural analgesia should be initiated 48 hours prior to surgery and continued in the postoperative period to provide significant reduction of PLP. Most anesthesiologists are familiar with the placement of lumbar epidurals. The onset of epidural anesthesia can be performed slowly, via an epidural catheter. This can be useful in patients who may not tolerate the rapid onset of a subarachnoid block.

Drawbacks: Epidural anesthesia can be less dense than a spinal nerve block. Similar to spinal anesthesia, patients with preexisting infections (sepsis/bacteremia) or local skin infections at the needle entry site may not be appropriate candidates due to the risk of direct spread of the infection to the epidural space. Additionally, coagulation status must be assessed where appropriate due to the risks of spinal or epidural hematoma. These bleeding risks extend into the postoperative period, where continuous epidural catheters must be managed with caution in the event that postoperative anticoagulation is used.

Issues: To provide reliable dense anesthesia, consider dosing the epidural with 2% lidocaine or 2% 2-cholorprocaine. Other local anesthetic agents are also effective, with longer duration. However, longer duration local anesthetics (bupivacaine, ropivacaine) also result in prolonged side effects (hypotension).

Peripheral nerve block

Peripheral nerve blocks offer similar benefits to those given for neuraxial blockade. These include dense anesthesia for surgery, prolonged postsurgical analgesia, and the ability to attenuate chronic PLP.

Benefits: Unlike neuraxial anesthesia, peripheral nerve blocks are not associated with significant hypotension. Therefore, in unstable patients, peripheral nerve blockade may be advantageous over neuraxial or general anesthesia. Properly performed peripheral nerve blocks can result in complete anesthesia, requiring minimal/no sedation or general anesthesia. This may be particularly useful in unstable patients. Continuous nerve block catheters can be placed prior to amputation surgery in the hope of attenuating central sensitization from surgical nociception.

Drawbacks: There is no single block site where the entire thigh or leg can be anesthetized with one injection. There are two major plexuses that must be blocked to provide complete anesthesia to the leg (lumbar plexus and sacral plexus). The plexi can be blocked more distally and still provide adequate anesthesia/analgesia for lower extremity amputations. Like neuraxial anesthesia, coagulation status must still be evaluated as the performance of deep nerve blocks in noncompressible regions can result in major hematomas. Localized infection may preclude the use of regional anesthesia in these areas as well.

Issues: Appropriate peripheral nerve blocks must be performed to achieve desired end points. To provide complete anesthesia for a BKA, a sciatic nerve block and a femoral or saphenous nerve block is required. For an AKA, a lumbar plexus/psoas compartment block and a sciatic nerve block are required. If postoperative analgesia is all that is required, a sciatic nerve block catheter should be placed for a BKA. For an AKA, a femoral nerve block catheter or lumbar plexus catheter should be used.

b. General anesthesia

General anesthesia is an appropriate choice for some patients undergoing amputation of the lower extremity.

Benefits: General anesthesia is reliable and is familiar to all anesthesiologists.

Drawbacks: General anesthesia provides analgesia only during the operative period. If significant reduction in PLP is desired, similar to that provided with epidural infusions, aggressive addition of preoperative and postoperative pain control with intravenous patient-controlled analgesia (IV PCA) is needed.

Other issues: Hypotension from anesthetic agents may cause pronounced cardiovascular insufficiency in patients who are hypovolemic and have significant comorbidities.

Airway is always a concern before inducing general anesthesia.

c. Monitored anesthesia care (MAC)

In diabetics with severe peripheral neuropathy, distal leg and foot amputations can be performed under MAC as sensation to the distal extremity can be minimal.

Drawbacks: Often, MAC can rapidly switch to general anesthesia if the surgical incision is extended to areas of increased sensation. The anesthesiologists must be prepared for a rapid conversion to general anesthesia.

Other issues: MAC can be provided in conjunction with neuraxial anesthesia or peripheral nerve blocks. Typically, propofol infusions provide stable, reproducible, titratable sedation for these cases.

Benefits: General or neuraxial anesthesia and the hemodynamic effects associated with each can be avoided.

6. What is the author's preferred method of anesthesia technique and why?

The preferred technique for amputation is as follows:

Early identification of patient presenting for amputation if possible

  • Preemptive analgesia for 48 hours with continuous peripheral nerve blocks or epidural analgesia or IV PCA

  • Continuous femoral nerve block for AKA or through-the-knee amputation

  • Continuous sciatic nerve block for BKAMultimodal analgesics preoperatively, intraoperatively, and postoperatively including pregabalin/gabapentin, NSAIDs, ketamine, opioids

  • Regional anesthesia for intraoperative management (peripheral nerve blocks, spinal, epidural) or general anesthesia

  • Aggressive treatment of any postoperative nociception (opioids, pregabalin/gabapentin, ketamine).

  • Continue any regional anesthesia for extended duration (days to weeks)

  • Aggressive multidisciplinary follow-up addressing psychosocial disability as well as pain

Often, infections are a primary cause for lower extremity infection. If antibiotics are scheduled, consider staying on the currently scheduled antibiotics. If no antibiotics are scheduled, use current SCIP recommendations.

Confirm with the surgery team where the amputation will take place—above or below the knee—as this will dictate which nerve blocks to place. Also, surgeons have varying degrees of blood loss for the same case. If the patient is anemic or has increased oxygen requirements that necessitate higher hematocrit levels, consider having blood replacement available. Often, blood loss in these cases is found in the field/surgical drapes and not in the suction canister. Be wary of blood loss, especially with prolonged surgery. If placing peripheral nerve block catheters, consider the postsurgical dressings. Attempt to place the nerve block catheter proximal enough along the leg so the catheter is not covered by the surgical dressing. If the catheter is not under the dressings, it can more easily be managed during the postoperative period. Surgical tourniquets are not often used if the indication for amputation is ischemic disease, but if they are to be used, attention to catheter placement in relation to the tourniquet is needed.

Intraoperative assistance includes providing adequate anesthesia. The most common intraoperative complication is blood loss, and replacement must be provided when appropriate.

In prolonged surgery, if there are any complications, surgery may outlast a spinal anesthetic or MAC. Be ready to convert to general anesthesia.

a. Neurologic:

Nerve injury is possible but often not identified or relevant because of preexisting neuropathy.

b. If the patient is intubated, are there any special criteria for extubation?

If the patient presented to surgery intubated (from the intensive care unit or direct from trauma), return the patient intubated. If a general anesthesia is used for a scheduled case, there are usually no special requirements for extubation.

c. Postoperative management

Analgesia

Peripheral nerve block catheters or epidural catheters are the preferred method to extend analgesia into the postoperative period. If these are contraindicated, consider opioids. Also, a multimodal approach to postoperative analgesia can be considered with gabapentin/pregabalin, acetaminophen, NSAIDs, or ketamine. Regardless of the analgesic modality that is chosen, it is likely important to control pain prior to amputation, not just postoperatively, to lessen the chance of PLP.

Standard postsurgical hospital floors are appropriate for these cases. If the patient presented from a higher acuity floor, he or she should be returned to similar.

Common postoperative complications

Pain: PLP can result in severe post-amputation pain in many patients. To lessen the chances of PLP developing, consider preemptive nerve blocks/multimodal analgesic therapy to decrease preoperative pain. The attenuation of preoperative pain may decrease the chances of postsurgical PLP, which often begins in the immediate postoperative period or the few days that follow the amputation. Optimized analgesia using continuous nerve blocks been extended for weeks and has shown benefit in limiting PLP post amputation.

Bleeding: Notify the surgical team if excessive bleeding is occurring.

Delirium: Consider multimodal analgesic therapy to limit opioids.

What's the Evidence?

Argoff, C, Albrecht, P, Irving, G, Rice, F. "Multimodal analgesia for chronic pain: rationale and future directions". Pain Med. vol. 10. 2009. pp. S53-66.

Buvanendran, A, Kroin, J. "Multimodal analgesia for controlling acute postoperative pain". Curr Opin Anaesthesiol. vol. 22. 2009. pp. 588-93.

Borghi, B, D'Addabbo, M, White, P, Gallerani, P, Toccaceli, L, Raffaeli, W, Tognu, A, Fabbri, N, Mercuri, M. "The use of prolonged peripheral neural blockade after lower extremity amputation: The effect on symptoms associated with phantom limb syndrome". Anesth Analg. vol. 111. 2010. pp. 1308-15.

Enneking, F, Chan, V, Greger, J, Hadzic, A, Lang, S, Horlocker, T. "Lower-extremity peripheral nerve blockade: essentials of our current understanding". Reg Anesth Pain Med. vol. 30. 2005. pp. 4-35.

Karanikolas, M, Aretha, D, Tsolakis, I, Monantera, G, Kiekkas, P, Papdoulas, S, Swarm, R, Filos, K. "Optimized perioperative analgesia reduces chronic phantom limb pain intensity, prevalence, and frequency: A prospective randomized clinical trial". Anesthesiology. vol. 114. 2011. pp. 1144-54.

Tintle, S, Keeling, J, Shawen, S, Forsberg, J, Potter, B. "Traumatic and trauma-related amputations: Part I: General principles and lower-extremity amputations". J Bone Joint Surg Am. vol. 92. 2010. pp. 2852-68.

Weeks, S, Anderson-Barnes, V, Tsao, J. The Neurologist. vol. 16. 2010. pp. 277-86.

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