Anesthesia for Extracorporeal Shock Wave Lithotripsy (ESWL)

1. Introduction

Extracorporeal Shock Wave Lithotripsy (ESWL) is a non-invasive procedure to break renal or ureteric calculi into smaller fragments using focused shock waves, allowing spontaneous passage via the urinary tract.

• First introduced in 1980 (Dornier HM3).
• Most effective for:
• Renal stones ≤2 cm
• Upper ureteric stones
• Not suitable for cystine stones or very hard calcium oxalate monohydrate stones.

 2. Procedure Overview

• The patient lies on a water-filled cushion or is immersed in a water bath.
• Shock waves are focused on the stone under fluoroscopic or ultrasound guidance.
• Typically 1500–2500 shocks/session, energy 12–24 kV.
• Treatment time: ~30–60 minutes.

3. Indications & Contraindications

✅ Indications

• Renal stones ≤2 cm (pelvis, upper/mid calyx)
• Ureteric stones (proximal)
• Patients unfit for invasive surgery

❌ Contraindications

4. Anesthetic Considerations

A. Preoperative Evaluation

• Full stone work-up (KUB X-ray, NCCT, USG)
• Urine culture → must be sterile prior to ESWL
• RFTs, coagulation profile
• Check for anatomical anomalies (e.g., horseshoe kidney)

 5. Anesthetic Techniques

Choice of anesthesia depends on:

• Type of machine (first-gen vs newer)
• Site of stone (renal vs ureteric)
• Pain threshold and age
• Duration of therapy

1. No Anesthesia / Sedation Only

• In cooperative adults with newer generation machines (electromagnetic)
• Often used for ureteric stones

2. Monitored Anesthesia Care (MAC)

• Short-acting IV opioids (fentanyl 1–2 µg/kg)
• Midazolam (0.5–2 mg IV)
• Ideal for short procedures and moderate discomfort

3. Regional Anesthesia

• Spinal anesthesia (T8–T10 level)
• Used for renal stones
• Less common now due to brief duration and better pain control with IV agents

4. General Anesthesia

• In pediatric patients, anxious adults, or complex long cases
• TIVA or short-acting agents (propofol, remifentanil)

6. Intraoperative Considerations

A. Positioning

• Usually supine or semi-Fowler
• Modified positions for lower ureteric stones (prone/lateral)

B. Monitoring

• Standard ASA monitors
• O₂ supplementation if sedation used
• Watch for arrhythmias during shocks (especially near heart)

ECG Gating (R-wave Synchronization)

• Modern ESWL machines are equipped with R-wave synchronization systems.
• Shock waves are timed to the absolute refractory period (i.e., after the R-wave on ECG) to prevent triggering arrhythmias.

C. Ventilation

• Controlled ventilation in GA cases
• Respiratory gating may be used to synchronize shocks

7. Complications of ESWL

💊 8. Postoperative Management

• Analgesia: NSAIDs, paracetamol
• Hydration: Encouraged to flush out fragments
• α-blockers (e.g., tamsulosin): To facilitate stone passage
• Monitor urine color, volume
• Warn about colicky pain during fragment passage

💡 9. Anesthesia in Pediatric ESWL

• Almost always requires GA with spontaneous or controlled ventilation
• Face mask or LMA sufficient for short cases
• Maintain normothermia, avoid hypovolemia

🧠 Viva Tips

Q. Why is GA preferred in children?
→ For immobility, pain control, and airway safety.

Q. Why can arrhythmias occur during ESWL?
→ Shock waves can stimulate the myocardium, especially for left-sided stones near the heart.

Q. What is Steinstrasse?
→ “Stone street” – multiple fragments blocking the ureter, leading to pain, obstruction, or infection.