What is the step‑by‑step technique for performing spinal anaesthesia in an adult patient undergoing lower abdominal, pelvic, perineal, or lower‑limb surgery without contraindications?

How to Perform Spinal Anaesthesia

Spinal anaesthesia should be performed using pencil-point needles ≥25 gauge with low-dose hyperbaric bupivacaine (<10 mg), positioned according to surgical site, with strict attention to contraindications including coagulopathy and patient refusal. 1, 2

Pre-procedure Assessment and Preparation

Verify Absence of Contraindications

• Absolute contraindications must be ruled out: patient refusal, coagulopathy/bleeding disorders, and active anticoagulation 1, 2, 3
• Check platelet count ≥75,000 × 10⁶/L if thrombocytopenia is suspected 1
• For patients with bleeding disorders, specific factor levels are required: Factor VIII/IX ≥50 IU/dL for mild bleeding history, ≥80 IU/dL for severe bleeding history 1
• Fibrinogen ≥1.5 g/L (Clauss method) is acceptable for spinal anaesthesia in patients with hypofibrinogenemia 1

Patient Preparation

• Establish intravenous access and commence fluid therapy before performing the spinal block to prevent hypotension 4
• Limit IV crystalloid to maximum 500 mL to reduce urinary retention risk 1, 5
• Provide clear explanation of the procedure to gain patient confidence and obtain informed consent 4
• Ensure standard monitoring is in place: continuous pulse oximetry, ECG, and blood pressure 2, 3

Equipment Selection

Needle Choice

• Use pencil-point spinal needles ≥25 gauge to minimize post-dural puncture headache (PDPH) incidence to <1% 1, 5
• Avoid cutting-bevel needles which significantly increase PDPH risk 1

Local Anaesthetic Selection

• Hyperbaric bupivacaine is the most commonly used long-acting agent 2
• Use doses <10 mg to significantly reduce hypotension while maintaining adequate anaesthesia 2, 3
• For outpatient procedures, lidocaine remains the most useful agent with rapid recovery 6
• Consider adding intrathecal fentanyl (not morphine) for prolonged analgesia without excessive sedation 3

Positioning Technique

Position According to Surgical Site

• Sitting position: For perianal/perineal procedures to minimize hypotension and motor block 1, 5
• Lateral decubitus: For unilateral procedures (e.g., knee arthroscopy) with operative side down to target the block 1, 2
• Lateral with fractured hip down: For hip fracture surgery in elderly patients to reduce hypotension 2

Positioning Duration

• Maintain position for 15-20 minutes after injection to allow drug fixation 7
• Be aware that position changes even 65 minutes post-injection can cause cardiovascular and respiratory effects with hyperbaric solutions 7

Procedure Steps

Sterile Technique

• Follow routine asepsis techniques as for non-complicated patients 1
• Use standard sterile preparation and draping

Needle Insertion

• Identify appropriate interspace (typically L3-4 or L4-5)
• Insert pencil-point needle ≥25 gauge using midline or paramedian approach
• Confirm free flow of clear cerebrospinal fluid
• Inject calculated dose of local anaesthetic slowly

Intraoperative Management

Monitoring and Support

• Provide supplemental oxygen throughout the procedure 2, 3
• Monitor for hypotension and treat promptly with vasopressors if needed 1
• Be prepared to convert to general anaesthesia if inadequate block develops 4
• Avoid oversedation which can mask important neurological signs 3

Common Pitfalls to Avoid

• Do not use excessive doses of local anaesthetic, especially when combining with other blocks 5
• Do not delay position changes beyond recommended timeframes with hyperbaric solutions 7
• Do not force oral intake postoperatively as this may provoke nausea and delay discharge 1

Postoperative Care and Discharge Criteria

Mobilization Criteria

• Return of perianal sensation (S4-5 dermatomes) 1, 2, 5
• Plantar flexion of foot at pre-operative strength levels 1, 2, 5
• Return of proprioception in the big toe 1, 2, 5

Analgesia Management

• Start oral analgesics BEFORE the spinal block wears off and continue on regular schedule (not PRN) 5
• Administer prophylactic long-acting NSAIDs unless contraindicated 1, 5
• Limit routine opioid use, particularly morphine, to reduce PONV 1, 5

Discharge Instructions

• Patients may be discharged with residual sensory block if limb is protected and adequate home support exists 1, 5
• Provide written and verbal instructions about expected block duration 1, 5
• Include information about PDPH symptoms and management in discharge instructions 1
• Advise against driving, operating machinery, or consuming alcohol for 24 hours 1, 5
• Provide warning signs of complications and emergency contact information 1, 5

PONV Management

• Reserve prophylactic antiemetics for high-risk patients only (history of PONV, motion sickness, specific procedures like laparoscopy) 1, 5
• Treat established PONV aggressively with multimodal regimen 5
• Maintain normothermia to reduce PONV incidence 5