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AS5.{3,6} | Peripheral Nerve Blocks and Common Surgical Blocks — SDL Guide (Part 3)
Self-Assessment: Peripheral and Surgical Blocks
Having completed this SDL, test your understanding against the following questions — answer each without reference before checking yourself.
Can you name the four terminal nerve territories of the axillary brachial plexus block and explain why a fifth injection (musculocutaneous nerve) is routinely needed? Can you explain why an interscalene block is contraindicated in a patient with contralateral phrenic nerve palsy? Can you describe in sequence what you would see on ultrasound when performing a femoral nerve block — from probe placement to LA spread? Do you know the approximate volume of local anaesthetic for each major block and what concentration of bupivacaine is commonly used for prolonged analgesia?
More critically: if a patient's blood pressure drops 10 minutes into a supraclavicular block with 20 mL of 0.5% bupivacaine, and the patient reports dizziness and tinnitus, what is your differential and what is your first action? The answer — stop the injection, call for help, prepare 20% intralipid, maintain airway — must be automatic, not recalled under stress.
Finally, reflect on the observation sessions you have attended or plan to attend. The competency for AS5.3 and AS5.6 is "observe and describe" — but the spirit of that competency is that you can walk into a room where a block is being performed, understand what is happening anatomically, predict what will be blocked, and contribute meaningfully to the assessment of its success. That level of informed observation requires the knowledge in this SDL to be truly internalised, not merely recognised on a multiple-choice examination.
SELF-CHECK
A TAP (transversus abdominis plane) block provides excellent analgesia after caesarean section for which of the following types of pain?
A. Uterine cramping and visceral pain from the peritoneum
B. Anterior abdominal wall pain from the skin incision and fascia
C. Pain from the bladder dome mobilised during surgery
D. Shoulder tip pain from residual peritoneal gas
Reveal Answer
Answer: B. Anterior abdominal wall pain from the skin incision and fascia
The TAP block targets the anterior rami of T10–L1 as they run in the plane between the internal oblique and transversus abdominis muscles. These nerves supply the skin, subcutaneous tissue, and anterior abdominal wall musculature — not the visceral peritoneum, uterus, or diaphragm. Therefore the TAP block provides excellent somatic analgesia for the skin incision but does not relieve uterine cramping (visceral pain from the uterus, mediated by T10–L1 sympathetic afferents travelling with visceral nerves, not somatic nerves), bladder pain, or shoulder tip pain (phrenic nerve, C3–C5). It is used as an adjunct — not a replacement — for neuraxial opioid analgesia after caesarean section.
CLINICAL PEARL
The "LAST rescue" that every observer must know: When any peripheral nerve block results in sudden CNS excitation (seizures, loss of consciousness) or cardiovascular collapse (broad complex arrhythmia, asystole), the diagnosis is local anaesthetic systemic toxicity (LAST) until proven otherwise. Management: STOP injection, call for help, maintain airway with 100% O2, treat seizures with a benzodiazepine, initiate CPR if arrested, and give 20% intralipid 1.5 mL/kg IV bolus immediately — then infusion at 0.25 mL/kg/min. Intralipid works as a lipid sink for lipophilic LAs (especially bupivacaine). Adrenaline should be used in small doses only (≤1 mcg/kg) during LAST resuscitation — large doses worsen the LA-induced arrhythmia. Prolonged CPR is justified because the lipid sink gradually reverses toxicity. Every anaesthetic room should have Intralipid available before any LA is injected.