In an 83‑year‑old patient, can I perform a pre‑operative ultrasound‑guided femoral peripheral nerve block followed by a subarachnoid (spinal) block, and what are the appropriate local‑anesthetic drug, dose and volume for each technique?

Combined Femoral Nerve Block and Spinal Anesthesia for Elderly Hip Fracture Surgery

Direct Answer

Yes, you can and should perform a pre-operative ultrasound-guided femoral nerve block followed by a subarachnoid block in your 83-year-old patient—this combination is explicitly recommended by current guidelines to optimize analgesia while minimizing opioid requirements and postoperative delirium risk. 1, 2

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Sequencing and Timing

Perform the femoral nerve block first, before positioning the patient for spinal anesthesia. 3

• The femoral block provides analgesia that makes positioning for the spinal block significantly less painful (median pain score 2 vs 3, p=0.037) and reduces the time required to perform the spinal procedure (10 vs 12 minutes, p=0.033). 3
• Wait approximately 5 minutes after the femoral block to allow adequate onset before moving the patient into sitting position for the spinal. 3

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Femoral Nerve Block: Drug, Dose, and Volume

Administer 20–25 mL of 0.25% bupivacaine for the femoral nerve block under ultrasound guidance. 1

Specific Dosing Details:

• Volume range: 20–30 mL total, with the lower end (20 mL) preferred in an 83-year-old to reduce systemic toxicity while maintaining adequate analgesia. 1
• Concentration: 0.25% bupivacaine is the standard choice, providing 12–18 hours of postoperative analgesia. 1
• Alternative agent: 0.2% ropivacaine at the same volume offers comparable efficacy with potentially lower cardiac toxicity risk. 1
• Maximum safe dose: Do not exceed 30 mL in this elderly patient; volumes >40 mL should never be used due to systemic toxicity risk. 1

Technical Requirements:

• Ultrasound guidance is mandatory in elderly patients to minimize volume requirements, improve needle accuracy, confirm local anesthetic spread, and reduce vascular puncture risk. 1, 4, 5
• The femoral block is relatively safe even in anticoagulated patients because the injection site is compressible, unlike neuraxial techniques. 1, 2

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Subarachnoid Block: Drug, Dose, and Volume

Administer 7.5 mg of 0.5% hyperbaric bupivacaine plus 20–25 µg intrathecal fentanyl for the spinal anesthetic. 1, 2

Specific Dosing Rationale:

• Use the lower bupivacaine dose (7.5 mg rather than 10 mg) in this 83-year-old patient, especially if cardiovascular disease is present, to reduce hypotension risk while still achieving adequate surgical anesthesia. 1, 2
• Doses <10 mg of intrathecal bupivacaine reduce hypotension incidence in elderly patients with moderate-strength evidence. 1, 2
• Intrathecal fentanyl (20–25 µg) provides 2–5 hours of postoperative analgesia without the respiratory depression or cognitive impairment associated with intrathecal morphine. 1, 6

Age-Related Dose Adjustment:

• Pharmacokinetic and pharmacodynamic changes in patients >55 years warrant a 20–25% reduction in anesthetic agent doses per decade of age. 1

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Pre-Procedure Safety Checks

Anticoagulation Status:

• Verify INR <1.5 before performing the spinal anesthetic if the patient is on chronic anticoagulation therapy. 1, 2
• The femoral block may proceed even with mild coagulopathy because the site is compressible. 1, 2

Cardiovascular Assessment:

• Cardiovascular disease, chronic diuretic use, and reduced baseline functional status are strong predictors of severe intra-operative events and 30-day mortality in elderly surgical patients. 1
• Consider invasive arterial blood pressure monitoring before induction if cardiovascular risk factors are present. 1

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Intra-Operative Hemodynamic Management

Maintain systolic blood pressure within ±20% of pre-induction baseline, using vasopressors preferentially rather than fluid boluses. 1

• Keep phenylephrine (100–200 µg bolus) or metaraminol immediately available and administer before additional IV fluids to prevent volume overload. 1
• Target mean arterial pressure >65 mm Hg, as hypotension below this threshold is associated with increased mortality in older patients. 1, 2
• Avoid excessive IV fluid administration for spinal-induced hypotension; use vasopressors first. 1, 2

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Sedation Strategy

Use minimal or no sedation during the spinal anesthetic to reduce delirium risk. 1, 2

• Long-acting benzodiazepines must be completely avoided because of their strong association with postoperative delirium in patients >60 years. 1, 2, 6
• Ketamine should not be used for sedation in this population due to significant postoperative confusion risk despite its cardiovascular stability advantages. 1, 6
• Opioids should not be used as the sole adjunct to anesthesia because of respiratory depression and postoperative confusion potential. 1, 2, 6

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Critical Pitfalls to Avoid

Never combine spinal and general anesthesia simultaneously—this causes precipitous intra-operative hypotension and is explicitly contraindicated. 1, 2, 6

• The combination of femoral block followed by spinal anesthesia is safe and recommended; the prohibition applies only to simultaneous spinal plus general anesthesia. 1, 2
• Do not rely on landmark (non-ultrasound) techniques for the femoral block in elderly patients; ultrasound guidance markedly improves safety and reduces required volume. 1
• Do not use the femoral nerve block as the sole anesthetic for surgery; it provides analgesia but must be supplemented with spinal or general anesthesia for operative cases. 1

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Expected Clinical Outcomes

This combined technique reduces pre-operative morphine consumption from 19.4 mg to 0.4 mg (p=0.05) and increases patient-reported satisfaction by 31% in patients ≥65 years. 1

• Peripheral nerve blockade decreases postoperative opioid requirements and lowers the risk of postoperative confusion. 1, 2
• The femoral block extends postoperative analgesia beyond the spinal anesthetic duration and further reduces opioid consumption. 1, 2