Case 9 - LVAD for noncardiac surgery

Question 1

What are ventricular assist devices (VADs) intended for, how do they work, what is the most common VAD on the market?

Answer 1

Define

• pumps implantated to assist failing ventricle and maintain systemic perfusion

Intentions

• bridge to recovery
• bridge to transplantation
• destination therapy

Function of LVAD

• drain blood from apex of LV, return blood by pump to the ascending aorta

Most common VAD

• 2nd generation, HeartMate II - nonpulsatile circulatory support

Question 2

What are your preop considerations for a patient with LVAD?

Answer 2

1) history

• reason for LVAD placement
• end-organ damage sustained during low CO state before VAD implantation
• pre-existing comorbidities - cover all systems

2) periop fluid management

3) periop anticoagulation

4) periop abx prophylaxis

5) periop managment of PPM and ICDs

6) PACU or ICU seting post-op

7) post op pain control

Question 3

what anesthetic agents and techniques are appropriate for LVAD pts?

Answer 3

• no superior anesthetic agent
• general more appropriate than regional because pts are on anticoagulation with VADs
• no reason to keep VAD pt intubated just because they have a VAD. use normal extubation criteria

Question 4

what are goals of fluid management in LVAD? Can RV function contribute to dec LV preload?

Answer 4

Goal - EUVOLEMIC or slightly HYPERVOLEMIC

• hypovoemia results in underfilled arterial tree
• LVAD output is dependent on intravascular volume

Maintain RV function

• dec RV function will casue dec blood flow to left side of heart = dec preload of LV
• prevent futher decreases in RV function by preventing inc in PVR
  
  • acidosis
  • hypoxemia
  • hypercarbia
  • hypothermia
  • symp stim (pain, light anesthesia)

Question 5

how would you handle the patient’s anticoagulation status prior to surgicla procedure (ie would you reverse it, how would you manage this)?

Answer 5

• anesthesiologist, surgeon, and physician managing VAD need to discuss risk of thromboembolism of VAD vs risk of surgical bleeding
• VAD pts are on A/C due to significant risk of thrombemoblic events associated with extracorporeal circulation –> require A/C

Management

• option is to stop warfarin and place patient on heparin infusion
• consider partial reversal, goal to aim at lower limit of manufactuer’rs recommendation
  
  • lower with FFP or cryo
• intra-op, frequent measurement of coag testing is important to balance dual potential of complications of hemorrhage and thromboembolism

Question 6

how should ICD and PPM be managed perioperatively in LVAD patient

Answer 6

• periop managment of PPM and ICD is the same in all patients
• need to determine: reason for placement, present mode, is it functioning appropriately, magnet response, is ICD present

ICD

• deactivated (magnet or programmer) and external defib pads placed

PPM

• if surgical site close to device, PPM should be programmed to asynchronous mode (magnet if no ICD present, or programmer if ICD present)
• if surgical site below umbilicus, can keep PPM on at current setting

Electrosurgical unit

• bipolar preferable
• bovie pad away from PPM site (drives current of cautery away from PPM device)

remember - after surgery, return devices to original settings

Question 7

is an arterial line necessary in LVAD patients?

Answer 7

Yes

• newer LVADs provide non-pulsatile flow
  
  • may seem some pulsatility (possibly due to heart flowing from LV into Aorta during systole as heart contracts
  • this small pulsatility is lost during hypovolemic states, such as fluid loss, induction of anesthesia (vasodilation)
    
    • no blood for heart to pump through aortic valve into aorta as all the remaning blood is ‘sucked’ into LVAD.
• two monitors affected = BP and SaO2
• arterial line under ultrasound

Question 8

Is it possible to get RV failure 2/2 LVAD support?

Answer 8

YES

• Decompression of LV by LVAD causes a leftward shift of interventricular septum
  
  • resutls in altered RV geometry, increased RV compliance, decreased RV contractility
• LVAD allows for high output -> increases RV preload
  
  • patient with pre-existing inc in PVR may experience increased RV afterload 2/2 increased right-sided and pulmonary artery flow

Question 9

would you use a central line or PAC in a VAD patient?

Answer 9

CVC

• detect developing RV failure
• guide fluid management (follow CVP trends)
• access for drug infusions
• transvenous pacing wires

PAC

• little info obtained regarding CO since LVAD console shows continuous CO
• can calculate SVR
  
  • an abrupt inc in SVR will cause residual volume in the LVAD pump, or Power number on console will increase
• SVO2
• at risk for complications

Question 10

what is pump flow, pump speed, pump power, and pulsatility index on LVAD?

Answer 10

Pump Flow

• output of device (like CO), L/min

Pump speed

• number of revolutions per minute at which the impeller is rotating
• high speed = inc ventricular unloading and inc flow through pump

Pump Power

• power required to spin the impeller at set speed
• increases in speed or flow -> inc power
• sudden inc in Power suggest abrupt SVR increase, thrombus, or obstruction of rotor rotation

pulsatility index

• reflects amount of assistance provided by device
• high PI means less assistance, low PI means high assistance
  
  • low PI = need to inc preload, inc contractility