FAILED EPIDURAL: CAUSES & MANAGEMENT

1. REVIEW ARTICLES FAILED EPIDURAL: CAUSES & MANAGEMENT PRESENTER : MEI YIN MODERATOR: DR TUAN NORIZAN BT TUAN MAHMUD

2. Failed epidural anaesthesia/ analgesia is more frequent than generally recognized. • Occurs up to 30% in clinical practice. • In heterogeneous cohort of 2140 surgical pt, failure rated of 32% for thoracic & 27% for lumbar epidural.

3. The definitions cover a spectrum ranging from insufficient analgesiato catheter dislodgementto any reason for early discontinuation of epidural analgesia.

5. DEFINITIONS & RATES OF FAILED EPIDURAL ANESTHESIA / ANALGESIA

11. CAUSES OF FAILED EPIDURAL • PHARMACOLOGICAL • DRUGS • DOSES • TECHNICAL • EQUIPMENT • - ANATOMY

12. CAUSES OF FAILED EPIDURAL In imaging study TECHNICAL PHARMACOLOGICAL 50 % Incorrect catheter placement Correctly placed catheter 50% Suboptimal analgesia

14. This review summarizes technical factors known to influence block success & gives an overview of the pharmacological strategies available to optimize epidural anaesthesia & analgesia.

15. TECHNICAL FACTORS INFLUENCING BLOCK SUCCESS

16. Anatomical Catheter Location • Pt Position • Puncture Site • Midline Vs Paramedian • Localization Of Epidural Space • Catheter Insertion & Fixation • Test Dose • Equipment

17. ANATOMICAL CATHETER LOCATION

18. Epidural catheters may primarily be placed incorrectly , OR become dislodged during the course of treatment. 1o misplacement can happens in ~ paravertebral space, ~ pleural cavity & ~ i.v.

19. Even when epidural space correctly identified, the catheter may leave the epidural space through intervertebral foramen at levels above @ below insertion site.

21. Factors contribute to 20 migration of epidural catheters : • Pt’s normal movement - may be displaced by cm • Changes in epidural pressures • CSF oscillations

22. In 60 pt undergoing surgery with thoracic epidural, with CXR taken before & after operation, the catheter had migrated > 1 vertebral level in 24%.

23. PATIENT POSITION

24. Lateral

25. Affects the needle placement by changing the relationship of osseous & soft tissues. Flexed position + head down result in (A) movement of spinal cord at thoracic level & (P) at lumbar.

26. Spinal cord is flexible attached within dural sac & changes in position according to gravity.

27. Sitting position • Shorter insertion times ( no applied to CSE in C-sec) • Higher accuracy at 1st attempt • Cost of more vagal reflexes • Leads to epidural venous plexus distension, the risk of vascular puncture, esp in parturients • Comparable final success rates with lateral position

28. Lateral positioning • the distances from skin to epidural space. • More difficulty in CSE anesthesia for C-sec.

29. PUNCTURE SITE

30. Most studies show that there is a tendency for the site to be more cranial than intended.

32. MIDLINE VS PARAMEDIAN

33. PARAMEDIAN In cadavers • using epiduroscopy, paramedian catheters cause less stenting & pass more cephalad more reliably. In pt • faster catheter insertion times. • Less dependent upon spine flexion.

34. MIDLINE Higher incidence of paraesthesia & bloody puncture in non-pregnant adult.

35. In parturients, the risk of vascular puncture was not associated with lumbar midline OR paramedian techniques.

36. LOCALIZATION OF EPIDURAL SPACE

37. Correct placement requires correct identification of epidural space. Variety method are used to confirm epidural needle position: * LOR using saline ( most widely used) * LOR to air * Hanging drop

40. Meta- analysis 2009 comparing LoR with saline vs air, included 5 RCTs ( total 4422 pts) :  4 in obstetric population & • 1 in general pt population significance difference in any outcome was found, other than 1.5% reduction in PDPH when using saline.

41. Study comparing CSE punctures using air / saline found no difference in success rate / adverse events. A recent retrospective study of 929 obstetric epidurals found that using air for LoR, significantly >> attempts were needed compared with saline with comparable final success.

42. Subgroup analyses showed that the use of the “ preferred technique” ( i.e. the technique used by a practitioner > 70% of the time) resulted in significantly - fewer attempts, - lower incidence of paraesthesia - & fewer dural headaches.

43. Hanging drop technique depends on -ve pressure within the epidural space. Recent experimental study evidence suggests that –ve pressure is poor reliably detecting the epidural space & is useful only in sitting position.

44. Of note, identification of the epidural space was reported 2mm deeper for hanging drop technique when compared with LoR, possibly indicating increase risk of dural perforation.

45. There is growing evidence-base for USG in obese pt & infants. USG is a useful educational tool & can enhance the learning curve for epidural anaestheisa. • pre-assessment of lumbar epidural space depth shown to correlate well with actual puncture depth in obese parturients.

46. In children, UGS allows identifications for the neuraxial structures, particularly neonates. < 3m.o. , only the vertebral bodies are ossified, enabling detailed visualization of spinal structures.

47. Only 1 RCT conducted, found that use of USG lead to : • << bony contact, • shorter time to block success • decreased supplemental opioid requirements.

48. CATHETER INSERTION & FIXATION

49. Optimal depth of insertion in adults is ~ 5 cm Methods of fixation : • Tunnelling of epidural catheter • Suturing • Catheter fixation device

50. Tunneling the epidural catheter for 5cm in cohort of 82 pts a/w less motion of catheter but the % of catheters maintaining original position was not statistically different.