Total Knee Arthroplasty (TKA)
Patient phenotype
Typically 60–80, OA-driven, often obese, frequently HTN + diabetes + sometimes CAD. Outpatient or 1-night admit. Increasing use of regional anesthesia + ERAS pathways.
Procedure
Anterior knee incision, cement femoral + tibial implants, polyethylene insert, optional patellar resurfacing. Tourniquet inflated for cement curing. ~90 min surgical time.
Anesthetic plan
Spinal (bupivacaine 0.75% hyperbaric 10–15 mg without intrathecal opioid for ERAS) + adductor canal block + IPACK block + sedation. GA only if neuraxial contraindicated. Multimodal opioid-sparing analgesia.
Setup
- ·Standard ASA monitors
- ·Two PIVs (one large for blood loss)
- ·Spinal kit + 25g pencil-point
- ·Ultrasound for blocks
- ·Tourniquet (record time + pressure)
- ·Type & screen (rarely transfused)
- ·Lower-extremity SCDs
Biggest concerns by phase
DVT prophylaxis + anticoagulation timing
TKA = major DVT risk. Most institutions use ASA 81 mg + mechanical SCDs for low-risk; LMWH or DOACs for higher-risk. For neuraxial: ASRA guidelines — hold LMWH 12 h (prophylactic) or 24 h (treatment); DOACs 72 h. Document last dose.
Spinal placement + dose for ERAS
Hyperbaric bupivacaine 0.75% 10–12 mg gives reliable T10 level, lasts ~2 h. Intrathecal opioid (morphine, fentanyl) historically added but in ERAS protocols often omitted for faster ambulation + less PONV/pruritus. Adductor canal block provides postop analgesia without quad weakness.
Tourniquet — pain, hypertension, deflation reactions
Tourniquet inflated 90–120 min typical. Persistent tourniquet pain breaks through spinal at ~60 min — give propofol or convert to GA if too long. Deflation: sudden ↓BP, ↑ETCO₂, possible TXA effect — pretreat with phenylephrine + ensure tourniquet documented (location, pressure, time).
Bone cement implantation syndrome (BCIS)
When cement cures in marrow cavity, fat + marrow contents embolize. Severity grades: grade 1 = ↓SpO₂ 5% / ↓BP 20%; grade 2 = ↓SpO₂ 10% / ↓BP 40%; grade 3 = cardiovascular collapse. Risk factors: pulmonary HTN, ASA 3-4, long-stem prostheses. Warn surgeon, communicate, fluid + vasopressor ready.
TXA — opioid-sparing for blood loss control
Tranexamic acid 10–20 mg/kg IV at incision + closure (or topical). Reduces transfusion need by 30–50%. Contraindications: active thromboembolism, recent stent. Most ortho protocols use 1 g pre-tourniquet + 1 g at deflation, sometimes also topical 1 g to wound.
Multimodal pain + early ambulation
Adductor canal block (sensory only, preserves quad) + IPACK block (posterior knee). Acetaminophen 1 g IV q6h, NSAID if no contraindication, gabapentin 300 mg pre-op. Early ambulation within 6 hours improves outcomes + DVT prevention.
Mock-defense scenarios
Practice answering these out loud. The probes show what an examiner is listening for.
Your TKA patient is 78, BMI 36, mild aortic stenosis (peak gradient 25 mmHg). Just after the surgeon cements the femoral component, BP drops from 130/80 to 75/45 and SpO₂ falls from 99 to 88. What's happening and what do you do?
What an examiner probes for
- ▹Recognizes BCIS — fat / marrow embolism
- ▹First moves: 100% O₂, fluid bolus, vasopressor (NE > phenyl in AS)
- ▹Considers concurrent differentials: PE, MI, anaphylaxis to cement
- ▹Communication: tell surgeon, may need TEE if profound + sustained
Patient had ASA 81 mg this morning + apixaban 5 mg last evening. ortho wants to do a spinal. What do you do, and what's your rationale?
What an examiner probes for
- ▹Recognizes apixaban + neuraxial = ASRA guidelines
- ▹Apixaban: hold 72 h before neuraxial, or check anti-Xa if unable to wait
- ▹Alternative: GA + adductor canal block + IPACK
- ▹Risk-benefit: spinal hematoma rare but devastating
Sources
- Miller's Ch 60 (regional)
- ASRA Anticoagulation Guidelines 2018
- ERAS Society TKA
Anatomy reference
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