Perioperative Management of a Patient with Ischemic Heart Disease Undergoing Total Knee Replacement


Background & Indications for Knee Replacement


How common are knee replacement surgeries globally and locally?
Around 1.8 million arthroplastic procedures are performed each year worldwide. It is a very prevalent surgery in countries like America and across Europe. In India, and particularly in Kerala, a significant number of knee replacement surgeries are done. In a typical trauma and orthopedic center, at least four to five knee replacements are performed every week.

What are the primary indications for a total knee replacement?
The key indications are:
  • Grade 3 and 4 Osteoarthritis (OA), where the joint space between the tibia and femur is obliterated.
  • Subluxation of the knee.
  • Limitation of daily activities due to pain and reduced patience (tolerance). Pain and limitation are the key factors for replacement.


Cardiovascular Risks and Benefits of Knee Replacement in IHD Patients


What factors exacerbate the risk of cardiovascular disease in IHD patients, specifically in the context of knee replacement?
Factors that exacerbate cardiovascular risk include raised blood pressure, poorly controlled diabetes, smoking, high body mass index, and increased stress. In the specific context of total knee replacement, the major causes are increased stress, use of non-steroidal drugs, underlying inflammation, and physical inability (functional limitation due to osteoarthritis). NSAID use and increased psychological stress are also major causes of cardiovascular issues.

What are the cardiovascular benefits of undergoing a total knee replacement?
Total knee arthroplasty has a proven benefit in improving a patient's pain, mobility, gait, and overall quality of life. By relieving pain and psychological stress, it can reduce the risk of serious cardiovascular events by up to 40%. Increased mobility, such as walking a few days a week, has a direct benefit on hypertension and obesity. This overall improvement in physical activity provides major physiological and psychological relief, which also helps in achieving better control of other comorbidities.


Preoperative Assessment and Optimization: A Case Study


Can you describe the case of the 72-year-old lady presented?
The patient is a 72-year-old lady with a 30-year history of systemic hypertension, managed on Telmisartan 40 mg OD and later Atenolol 25 mg OD. Five years back, she underwent PCI to the LAD and left circumflex artery and currently receives Aspirin 75 mg. She has bilateral knee osteoarthritis with severe functional limitation due to pain. The decision was made to proceed with a left-sided total knee replacement first, as it was more affected, with the right side to be done in a second sitting.

What were the key findings in this patient's preoperative evaluation?
The patient's weight is 54 kg. She has anemia, and her blood pressure was raised at 160 mm Hg systolic. Her pulse rate was 65 and airway assessment was adequate. This is a post-PCI patient undergoing elective surgery. For elective surgeries, routine, useless tests are not needed. The principle is to investigate and treat the patient as if they were not undergoing surgery.

What is the recommended timeline for elective surgery in a post-PCI patient?
For a post-PCI patient:
  • Less than 3 months: Elective surgery should be delayed.
  • 3 to 6 months: This is a preferable window for surgery.
  • More than 6 months: This is the typical time for discontinuing dual anti-platelet therapy (DAPT), and surgery can proceed. For highly elective surgeries like knee replacement, it's common to wait until DAPT can be safely stopped.

How was the patient's functional capacity assessed preoperatively?
Assessing functional capacity was difficult due to the patient's bilateral OA and limited activity, compounded by her anemia. However, a metabolic equivalence (METs) of more than four was expected.

What preoperative investigations were indicated for this patient?
  • ECG: While not recommended on a routine basis, it is clearly indicated in patients with known ischemic heart disease, as guidelines recommend it for intermediate and high-risk cases.
  • Echocardiogram (Echo): Needed to evaluate ejection fraction, check for valvular calcifications or stenosis, and assess for regional wall motion abnormalities.
  • Stress Echo/Thallium: These are indicated if the patient is symptomatic to check for wall motion abnormalities. However, for a highly elective surgery, an asymptomatic patient would not typically be taken up for replacement, so these are not routine.

How was this patient optimized preoperatively, specifically regarding anemia and hypertension?
  • Anemia: There is no clear-cut transfusion trigger, but the general consensus is to keep hemoglobin above 8 g/dL. Guidelines state it should not be less than 7 g/dL. The approach is to use oral ferritin to build up hemoglobin, not intravenous ferritin, as it's an elective procedure.
  • Hypertension: Telmisartan (an ARB) was stopped 24 hours prior to surgery to prevent uncontrollable hypotension and a poor response to vasopressors. Beta-blockers (Atenolol) were continued for better control of heart rate and hypertension.

What other key steps were part of the preoperative preparation?
  • Consent and Discussion: The procedure was explained to the patient. The anesthesiologist discussed postoperative pain management, which is very important to address patient concerns about pain.
  • Blood Arrangement: Blood was arranged because the patient's hemoglobin was low.
  • Surgical Checklist: A WHO-style checklist was used, with a strong emphasis on confirming the correct surgical side.
  • Antibiotics: Administered 60 minutes prior to incision. In this institution, Cefuroxime 1.5 gm and Teicoplanin 400 mg were used, with post-op doses continued.


Intraoperative Management


What was the anesthetic technique of choice for this patient, and why?
The primary technique was a subarachnoid block (spinal anesthesia) using 2.8 to 3 ml of 0.5% heavy Bupivacaine. This was supplemented with an ultrasound-guided Adductor Canal Block (ACB) or an iPACK block for postoperative pain. This regional approach was chosen because patients are often very comfortable and cooperative with it. General anesthesia is not contraindicated and can be used if the patient prefers it.

What intraoperative monitoring was essential for this IHD patient?
Continuous ECG monitoring was recommended, with at least leads II, V5, and V6 being monitored. Invasive blood pressure monitoring and continuous SpO2 monitoring were also essential.

What is Bone Cement Implantation Syndrome (BCIS), and why is it a concern in knee replacement?
BCIS is a concern because a total knee replacement uses around 40 grams of cement. Its clinical features include hypoxia, sudden loss of arterial pressure, pulmonary hypertension, arrhythmias, loss of consciousness, and even cardiac arrest. The pathophysiology is thought to be embolic (microembolism of fat, marrow, and cement) and multimodal (complement activation). Patients at higher risk are those of increasing age, with significant comorbidities, and those on diuretics.

How was the team prepared to manage Bone Cement Implantation Syndrome?
The team prepared by having the surgeon inform the team just prior to cementing. A close watch was kept on the patient's hemodynamic status. Practical steps included keeping the FiO2 high and ensuring adequate volume status. Treatment, if needed, would include 100% oxygen, fluid resuscitation, and vasoactive or inotropic agents.

What is the significance of "tourniquet release" during the surgery?
Just after the procedure is over, when the tourniquet is released, a close watch must be kept on hemodynamics. This is because when the tourniquet is deflated, hypotension can be expected.


Postoperative Management and Analgesia


What was the comprehensive postoperative pain management strategy?
The strategy was multimodal and continuous:
  • A continuous Adductor Canal Block catheter with Ropivacaine 0.2% and Fentanyl was used, with a bolus given before physiotherapy.
  • Multimodal analgesics including Paracetamol were administered.
  • Pain scores were aggressively managed to keep them below 3 or 4, especially to ensure the first physiotherapy session was pain-free to win the patient's confidence.

Why are the Adductor Canal Block (ACB) and iPACK block used for knee replacement analgesia?
  • Adductor Canal Block (ACB): This is a motor-sparing block used for anterior knee pain. It blocks the saphenous nerve and nerve to vastus medialis, which supply the medial and anterior portions of the knee.
  • iPACK (Infiltration between the Popliteal Artery and Capsule of the Knee): This block is used for posterior knee pain, targeting the terminal branches of the tibial and common peroneal nerves that supply the back of the knee. Isolating the tibial nerve with this block avoids the foot drop that can occur with a full sciatic nerve block.

What was the plan for thromboprophylaxis in the postoperative period?
Mechanical prophylaxis with intermittent pneumatic compression devices was used. Pharmacological prophylaxis included low molecular weight heparin (Enoxaparin 40 mg) started six hours after surgery. In this institution, Aspirin 75 mg is often continued for six weeks post-operatively, which is accepted by ACCP and orthopedic associations.

How long was the patient kept in the ICU, and why?
The patient was kept in the ICU for only one day. The primary reasons were for close monitoring of hemodynamic status and to provide optimal pain management, especially through the first physiotherapy session. Keeping elderly patients in the ICU for longer than one day risks ICU psychosis. After a day, the patient was shifted to the room to socialize with relatives, while monitoring (ECG) was continued in the room.


Perioperative Myocardial Infarction (MI) and Other Concerns


How is a perioperative MI recognized and managed in these patients?
Perioperative MIs are often due to supply-demand mismatch rather than plaque rupture. They can be silent, especially in elderly or diabetic patients. Recognition involves:
  • Clinical: Persistent hypotension not responding to usual measures, arrhythmias, severe bradycardia, or a drop in SpO2 after ruling out other causes.
  • ECG: May show changes, but can be difficult to interpret.
  • Biomarkers: Troponin is the key biomarker, typically rising 24-48 hours post-op.
Management focuses on treating the underlying cause—tachycardia and hypotension. Maintaining hemodynamic stability is paramount. Beta-blockers are key for controlling heart rate. If cardiovascular collapse occurs, ACLS protocols are followed.

What is the role of combining RCRI with biomarkers for risk prediction?
Combining the values of biomarkers, specifically high-sensitivity cardiac troponin, with the Revised Cardiac Risk Index (RCRI) gives a very good predictive value regarding a patient's perioperative risk. It can also be used post-operatively to compare values if a cardiac event is suspected.

How is dual antiplatelet therapy (DAPT) managed perioperatively?
For elective surgeries like this, the procedure is typically delayed until DAPT can be safely stopped, often after one year when the stent is fully epithelialized. At that point, Aspirin can be stopped 7-10 days prior and Clopidogrel 5-7 days prior. Bridging is generally not required for elective procedures as surgery is planned after the high-risk period.

Is there a concern about using tranexamic acid in an IHD patient on antiplatelets?
No, this is not a significant concern. Studies on tranexamic acid in IHD patients show it is safe. Its use helps minimize blood loss (which can be 1.5 to 2 liters), which is particularly beneficial in an anemic patient and reduces the need for blood transfusions.

What is the timeframe for increased cardiovascular risk post-surgery?
Studies show that cardiovascular complications are very high in the first two weeks following surgery in IHD patients. However, if the patient survives this initial two-week period, their overall physical activity and cardiac status often improve due to increased mobility and better control of hypertension.