What are the necessary preoperative and postoperative considerations for a patient with underlying conditions such as diabetes and heart disease undergoing an above-knee amputation?

Preoperative and Postoperative Management for Above-Knee Amputation in Patients with Diabetes and Heart Disease

For patients with diabetes and heart disease undergoing above-knee amputation, multispecialty team collaboration is essential, with priority given to cardiovascular risk stratification, glycemic optimization, and assessment of cardiac autonomic neuropathy before surgery, followed by intensive postoperative surveillance for wound complications and metabolic derangements. 1

Preoperative Assessment

Cardiovascular Evaluation

Comprehensive cardiac assessment is mandatory given the high perioperative risk in this population. 1

• Obtain a current 12-lead ECG to evaluate for ischemia, silent myocardial infarction (which presents atypically in diabetics as dyspnea or weakness rather than chest pain), tachycardia, arrhythmias, and prolonged QTc interval 1
• Calculate the Lee (Revised Cardiac Risk Index) score; if ≥2 with functional capacity <4 METs, refer to cardiology for further cardiac ischemia testing 1
• Measure BNP or pro-BNP levels if cardiac ischemia or heart failure is suspected, as diabetic patients have 2-3 times higher risk of heart failure with 10 times higher mortality after the first episode 1
• Perform echocardiography to assess left ventricular function, particularly if severe heart failure (ejection fraction <30%) is present 1
• Review prior coronary revascularization history and current cardiac symptoms 1

Cardiac Autonomic Neuropathy Screening

Screen all diabetic patients for cardiac autonomic neuropathy (CAN), as this significantly increases perioperative hemodynamic instability and mortality risk. 1

• Assess for CAN symptoms: permanent tachycardia, orthostatic or postprandial hypotension, severe unfelt hypoglycemia, absence of nocturnal blood pressure dipping 1
• Perform respiratory heart rate variability testing during deep breathing 1
• Measure orthostatic vital signs (blood pressure and heart rate changes from supine to standing) 1
• If CAN is confirmed, expect increased perioperative vasopressor requirements and plan for intensive hemodynamic monitoring 1
• Measure QTc interval on ECG; if prolonged, obtain 24-hour continuous ECG monitoring to detect paroxysmal ventricular arrhythmias 1

Diabetes Management

Optimize glycemic control while avoiding hypoglycemia, which is the primary cause of unexplained weakness in diabetic surgical patients. 2

• Check HbA1c, fasting glucose, creatinine, and urinalysis to assess current glycemic control and diabetic complications 3
• Screen for diabetic nephropathy, neuropathy, and retinopathy, as these complications impact perioperative risk 1, 3
• Hyperglycemia alone does not delay surgery unless the patient is ketotic or severely dehydrated 4
• Implement hospital-specific perioperative diabetes protocols 4

Medication Management

Continue ACE inhibitors (ramipril) on the morning of surgery with a sip of water, as there is no evidence that withholding improves outcomes in urgent surgery. 4

• Review all medications for polypharmacy (20% of patients >70 take >5 medications; 80% of adverse drug reactions are potentially avoidable) 4
• Stop metformin the night before surgery due to lactic acidosis risk, particularly in patients with renal failure (creatinine clearance <60 mL/min), dehydration, or severe heart failure (ejection fraction <30%) 1
• Do not restart metformin until 48 hours postoperatively for major surgery and only after confirming adequate renal function 1
• For insulin pump users, understand the total basal delivery rate and have a replacement scheme ready (long-acting insulin dose if pump is stopped) to prevent ketoacidosis 1

Anemia Assessment

Preoperative anemia occurs in 40% of patients and is a critical risk factor for amputation failure. 4, 5

• Check hemoglobin; if <9 g/dL or <10 g/dL with cardiac history, consider preoperative transfusion 4
• Preoperative anemia was present in 100% of patients who ultimately required above-knee amputation in one series, with average hemoglobin of 99.9 g/dL versus 118.2 g/dL in limb salvage patients 5
• Anemia exacerbates silent myocardial ischemia in diabetic patients and contributes to postoperative weakness 2

Vascular Assessment

The quality of femoral pulse significantly affects wound healing after above-knee amputation. 6

• Palpate femoral pulses bilaterally; a diminished or absent femoral pulse is associated with significantly higher wound complication rates 6
• Patients with diminished femoral pulse should undergo arteriography before amputation 6
• Evaluate for stenosis or occlusion of the common femoral or profunda femoral artery 6
• Consider reconstructive vascular surgery before amputation if feasible, or primary hip disarticulation in the presence of multiple risk factors 6

Additional Risk Factors

Identify high-risk factors that predict poor functional outcomes and increased amputation failure. 7, 5

• Age ≥70 years is independently associated with death (HR 3.1), failure of ambulation (HR 2.3), and failure to maintain independent living (HR 4.0) 7
• Severe comorbidities, alcohol abuse, and end-stage renal disease significantly increase risk of amputation failure 5
• Nonambulatory status before amputation is the strongest predictor of not wearing a prosthesis postoperatively (OR 9.5) 7
• Dementia (OR 2.4) and coronary artery disease (OR 2.0) independently predict failure to use prosthesis 7

Emergency Situations

In patients with life-threatening sepsis from foot infection, extensive tissue necrosis with metabolic derangements, or septic/gas gangrene, emergency amputation takes precedence over optimization. 1

• Emergency amputation is necessary to prevent catastrophic circulatory collapse 1
• Life over limb is the prevailing factor in these scenarios 1

Anesthetic Planning

Regional anesthesia (spinal or epidural) is strongly preferred over general anesthesia for diabetic patients with heart disease. 1, 3

• Regional anesthesia reduces sympathetic hyperactivity, which is elevated in diabetic patients and those with metabolic syndrome 1
• Spinal and epidural anesthesia decrease sympathetic nervous influx and may improve outcomes in patients with cardiac autonomic neuropathy 1, 3
• Regional anesthesia allows better postoperative pain control, early mobilization, and better cooperation with physiotherapy 4, 3
• In patients with severe cardiac disease, cardiomyopathy, congestive heart failure, or renal failure, regional anesthesia is preferred over surgical approaches when feasible 1
• Peripheral nerve blocks are not contraindicated but require documentation of preoperative clinical examination for dysautonomia and pre-existing polyneuropathy 1

Postoperative Management

Glycemic Control

Maintain blood glucose levels below 10 mmol/L (180 mg/dL) to decrease risk of death, infection, and prolonged hospital stay. 2

• Implement continuous glucose monitoring in the immediate postoperative period 2
• Prolonged perioperative fasting and irregular food intake significantly increase hypoglycemia risk 2
• Renal or hepatic dysfunction decreases clearance of antidiabetic medications and increases hypoglycemia risk 2
• If unexplained weakness occurs, immediately measure capillary blood glucose and administer urgent glucose if hypoglycemia is confirmed 2

Wound Surveillance

Wound complications and hospital readmission rates are high in patients with diabetes and heart disease undergoing major limb amputation, reflecting the burden of advanced cardiovascular disease and comorbidities. 1

• Implement intensive wound surveillance protocols 1
• Monitor for signs of infection, dehiscence, and stump complications 1
• Ensure adequate perfusion to the amputation site for healing 1

Cardiovascular Monitoring

Monitor for silent myocardial ischemia and heart failure, which commonly present atypically in diabetic patients. 2

• Continuous cardiac monitoring for arrhythmias, particularly in patients with prolonged QTc or cardiac autonomic neuropathy 1
• Serial troponin and BNP measurements if cardiac symptoms develop 2
• Monitor for hemodynamic instability, as perioperative vasopressor requirements correlate with degree of dysautonomia 1

Multispecialty Team Collaboration

A multispecialty care team is essential to meet the broad needs of patients with diabetes and heart disease undergoing amputation. 1

• Team should include vascular surgery, cardiology, endocrinology, wound care specialists, physical therapy, and prosthetics 1
• Implement management plan for diabetes and medical comorbidities at the time of amputation 1
• Patient education, appropriate extremity pressure offloading with prescription shoes, and foot surveillance examinations are essential to reducing wound recurrence 1

Critical Pitfalls to Avoid

• Do not delay surgery for "optimization" of chronic conditions unless life-threatening cardiac instability exists; delay increases mortality and complications 4
• Do not withhold ACE inhibitors perioperatively 4
• Do not ignore preoperative anemia, as it is present in all patients who ultimately fail amputation and should be aggressively treated 5
• Do not overlook cardiac autonomic neuropathy screening, as it predicts perioperative hemodynamic instability and long-term mortality 1
• Do not restart metformin before 48 hours postoperatively without confirming adequate renal function 1
• Do not assume normal glucose levels exclude hypoglycemia as the cause of postoperative weakness; repeat testing if clinical suspicion is high 2

Functional Outcome Considerations

Patients with limited preoperative ambulatory ability, age ≥70, dementia, end-stage renal disease, and advanced coronary artery disease perform poorly and should be counseled accordingly. 7

• Only 5 of 25 patients (20%) in one series were walking even to a limited degree with prosthesis after above-knee amputation 8
• Functional outcomes are particularly poor when amputation is performed for periprosthetic joint infection or after failed total knee replacement 8
• Younger healthy patients with below-knee amputations achieve functional outcomes similar to successful lower extremity revascularization 7