Case 51 - total hip replacement

Question 1

why are coronary stents important?

Answer 1

• foregin body nature of stents serves as a nidus for thombi formation.
• pts on dual anti-PLT therapy
• after period of time, stent struts are incorporated into coronary artery endothelium –> risk of thrombus is reduced

ASA recommend:

• need to know type, timing, number and location of stent
• consider cardiac consult and echo to assess perfusion and ventricular function (also to plan for perioperative stent management)

Question 2

what are preop anes considerations for a pt with coronray artery DES currently taking antiplatelet meds?

Answer 2

ASA recommends:

1) delay elective noncardiac procedure that have significant bleeding potential:

• BMS - min 1 month (usually choose this stent over DES if urgent surgery is imminnet or planned ahead of time)
• DES - 12 months

2) all procedures (including urgent or emergent), continue ASA therapy through periop period
3) beyond this time frame, d/c clopidogrel 7 days or ticlodipine for 14 days before surgery, restart therapy once hemostasis controlled.

Question 3

is there evidence for bridging therapy to decrease the risk of stent thrombosis resulting from premature discontiuation of thienopyridine therapy?

Answer 3

• premature d/c of plavix increases risk of life-threateningstent thrombosis and acute MI in periop period
• american heart associatoin and american college of cardiology –> no clear benefits of using any anticoaglants (including warfarin and heparin) as bridging therapy to decrease stent thrombosis

Question 4

85 yo female falls, sustains hip injury and requires a total hip replacement. She has had a recent DES placed 6 months ago, and is currently on plavix and ASA. What are the risks/benefit of hip surgery in this patient?

Answer 4

1) delaying surgery

• benefit - avoid premature d/c of anti-PLT therapy (avoid increasing risk of in-stent thrombosis assoc with early d/c of therapy)
• Risk - mortaility high for elderly patients not undergoing hip sx soon after injury
• Risk - higher incidence of pneumonia, presure ulcers while bed bound, overall decreaes in quality of life.

2) premature d/c of anti-PLT to proceed with surgery

• Benefit - early surgery reduces risk in mortality (<72 hrs after fx)
• Risk - early d/c of anti-PLT –> higher incidence and mortality of stent thrombosis
  
  • stressful, procoagulant, and proinflammatory nature of surgery may exacerbate stent thrombosis too.
• Risk - surgical bleeding if proceeding with sx

Plan:

best approach –> explain risks and benefits to the patient

Question 5

What are the ASRA guidelines for Neuraxial Anesthesia for heparin, plavix, and warfarin?

Answer 5

1) Thienpyridine (ADP recep antag)

• cath insert - stop plavix 7 days; ticlopidine - 14 days
• cath removal - restart as soon as possible after stable hemostasis

2) Warfarin

• check INR if dose given > 24 hrs or more than 1 dose given pre-op
• cath insert - Initiating therapy
  
  • INR < 1.5 or 1st dose given w/i 48 hr
  • long term therapy - d/c 5 days with normal INR
• cath removal - no wait time necessary (warfarin takes > 24 hrs to reeach peak effect)

3) Heparin

• safe with 5000 U BID
• unsure about TID dosing or > 10,000 U/dau (monitor carefully postop)
• heparin therapy > 4 days –> get PLT for HIT
• cath insert
  
  • 2-4 hrs after heparin is stopped
• Cath removal
  
  • restart 1 - 2 hrs after cath removal

Question 6

what are the ASRA guidelines for neuraxial anesthesia for LMWH, NSAID, glyco iib/iiia inhibitors?

Answer 6

4) LWMH

• no evidence for routine checking of anti-Xa
• female, elderly, renal impair, concomitant a/c –> higher risk of spinal hematoma
• Cath insert
  
  • 12 hrs after prophylactic dose
  • 24 hrs after high doses
• Cath removal
  
  • wait to restart 24 hrs after bloody or difficult placement
  • BID dosing - first dose 24 hrs after sx, but remove catheter 2 hrs prior to giving 1st dose
  • Daily dosing - remove cath 12 hrs after last dose, restart med 2 hrs later.

5) NSAID
* no contraindication
6) glyco iib/iiia

• risk with neuraxial anes unknown
• abciximab - 24 to 48 hrs wait time prior to block
• tirofibain - 4 to 8 hrs wait time prior to block
• unclear about catheter management

Question 7

what are asra guidelines for neuraxial anes for thrombin inhibitor, factor Xa inhibitor, and thrombolytics?

Answer 7

7) Thrombin inhibitor (agratrobain, bivalirudin)

• avoid neuraxial techniques (no reversal agent)
• dabigatran - wait 5 to 7 days prior to block
• unknown catheter management

8) Factor Xa inhibitor (fondaparinux, rivaroxaban)

• unknown risk
• unknown catheter management

9) thromolytics
* avoid neuraxial techniques
10) herbal meds
* no contraindications

Question 8

What should you do if you accidentaly placed an epidural in a patient who was recently on thrombolytics?

Answer 8

several considerations:

1) review H&P to ensure no concomitant a/c that would increase risk of spinal hematoma

2) high risk pts recieving a/c

• intensive neurologic monitoring and vigilant nursing checks q1-2 h
• neuraxial solution titrated to minimize sensory and motor blockade

3) bloody or difficult tap
* no data to support cancellation of sx. discuss with surgical team for appropriate management

Question 9

what is INR < 1.5 chosen as the cutoff point for neuraxial blockade?

Answer 9

• warfarin inhibits Vitamin K-dependent clotting factors
  
  • II (thrombin), VII, IX, X
  • Half-life FVII = 6 hrs
  • Half-life of rest = 24-80 hrs
• INR sensitive to levels of factor VII (first to leave)
• **INR 1.5 = factor VII activity level of 40% = minimal needed for normal coagulation. ** Anything less than this increases risk of bleeding

Warfarin initiated > 48 hours

• check INR prior to block placement
• incurs higher risk of epidural hematoma b/c activity of F IX and F II (not reflected by INR) may decrease to hemorrhagic levels.

Warfarin chronic therapy

• d/c for 5 days
• 5 days = full normalizatoin of all factors (although F VII is the first to return, INR will not reflect this until 5 days later)

Question 10

what is dabigatran and current ASRA guidelines?

Answer 10

Dabigatran (Pradaxa)

• direct thrombin antagonist
• half life 17 hrs after multiple dose (8 hrs after single dose)
• cleared by kidneys (avoid in renal dz)
• consider waiting 5 days after d/c of med for block
  
  • avoid restarting during indwelling catheter placement.

Question 11

what are the established beneifts of regional anesthesia?

Answer 11

Benefits:

• thoracic epidural
  
  • reduce incidence of MI
  • risk of postop pneumonia
  • seen in vasc and ortho pts
• epidural analgesia in general
  
  • decrease post-op ileus
  • increase patient satisfaction
  • decrease pain score at rest and activity
• peripheral nerve blocks
  
  • superior pain control compared to systemic opioids for major ortho surgery
  • decrease length of stay, n/v, pruritus, sedation
  • pts able to tolerate physical therapy

Question 12

85 yo female on plavix comes for hip surgery. She discontinued her plavix prematurely due to urgent nature of sx. Plans are to restart plavix perioperatively after surgical hemostasis. What are options of your post op plan?

Answer 12

• multimodal postoperative analgesia
  
  • tylenol
  • nsaid (depending on bleeidng risk)
  • opioids (long acting vs short acting)
  • gabapentin
• IV PCA
• Regional Anesthesia - Lumbar plexus block
  
  • deep block
  • follow neuraxial asra guideline (not the best choice for a plavix pt)
• Regional anesthesia - femoral nerve block
  
  • not a deep block, compressible vessel

Question 13

85 yo female on plavix comes for hip surgery. She discontinued her plavix prematurely due to urgent nature of sx. Plans are to restart plavix perioperatively after surgical hemostasis. What is your intra-op plan?

Answer 13

• in absence of significant airway or pulmonary problems, proceed with General Anesthesia
  
  • avoid neuraxial anes due to bleeding risk
• d/c plavix to minimize surgical hemorrhage
• blood products ready (RBC and PLT)