Perioperative Mx of pts with ventricular assist devices undergoing non-cardiac surgery blue book article Flashcards
What are ventricular assist devices?
Mechanical circulatory support devices giving temporary or long-term support for pts with advanced heart failure non-responsive to maximal medical therapy.
They can support the LV, RV or both.
What is funding for VADs approved for?
as a bridge to heart transplantation
What’s the periop M&M with pts with VADs undergoing non-cardiac surgery or pregnancy?
low in the immediate periop period & @ 12/12 follow-up
What’s the physiological goal of a VAD?
reduce LV work & provide adequate systemic perfusion by active unloading of the LV & returning blood to the aorta under +ve pressure
blood is drained from the LV apex via an inflow cannula & returned to the ascending aorta via an outflow cannula
What are the 3 devices used for VAD support in ANZ? type of continuous flow pump? pump speed? where implanted? anticoagulation targets (warfarin)?
Heartmate II- axial pump- 9000rpm- subdiaphragmatically implanted- INR 2.5-3.5
Heartmate III- magnetically driven centrifugal pump- 5000-6000rpm- implanted within the pericardium- INR 2-3
HeartWare HVAD- magnetically driven centrifugal pump- 2500rpm- implanted within the pericardium- INR 2-3
all use continuous flow pumps
While it’s not an approved indication in ANZ, what’s the most common indication for VAD implantation worldwide?
destination therapy- in pts with advanced HF ineligible for heart transplant
What proportion of pts with VADs have unplanned hospitalisation within the first 6/12 of device placement? main reasons?
30%
bleeding
infection (esp driveline)
stroke or device thrombosis (pts require strict anticoagulation regimen)
RHF
What are the most common non-cardiac procedures for pts with VADs?
UGI endoscopy (incr risk GI bleeding as these pts need anticoagulation)
Should cardiac anaesthetists be involved in the care of pts with VADs presenting for non-cardiac surgery?
yes if major surgery, the pt has multiple comorbidities or is on long-term pharmacological support
They should be managed at cardiac centres with experience in VADs, though
What’s the most notable periop issue for pts with VADs? others?
hypotension
AKI
excess bleeding
arrhythmias
What should occur for periop Ax/planning of pts undergoing elective surgery with VADs?
Multi-D Ax by anaesthetist, procedurals, HF cardiologist, VAD nurse specialist or perfusionist
May require consultation with card surg or haematologist
Ax:
functional status
organ function (renal, hepatic, haematological, obtain ECG & CXR, up-to-date echo for all but the most minor procedures & particularly focus on RV function which is often impaired)- correct any reversible issues eg. electrolytes, hypotension
meds
function of the VAD
function of any ICD or pacemaker
Planning:
anticipate greater than usual blood loss & blood typed & X-matched for transfusion
Monitoring:
-IABP for all but the most minor procedures (use US guidance given non-pulsatile arterial flow)
-Large-bore IV as bleeding risk
-Non-invasive BP monitoring (eg. intermittent MAP via doppler US)
-pulse ox trace quality poor due to non-pulsatile flow but can still get readings
-NIRS (near infra-red cerebral spectroscopy) is useful, doesn’t rely on pulsatile flow
-BIS useful since haemodynamic responses to nociception/awareness may be absent or blunted
-place external defibrillator pads prior to induction
-consider CVC if large fluid shifts or inotrope requirement anticipated
-intra-op TOE useful for most cases
-cardiac surgeon should be immediately available for procedures occurring in close proximity to a VAD
-VAD specialist present, interrogate device prior to OT & be present throughout- should advise anaesthetist & procedurals particularly if reduced VAD flow (L/min) for a given pump speed (rpm)
-on transfer to OT, VAD uses it’s battery power (battery life 6-10 hrs); once pt positioned, connect to UPS
-spare batteries should remain with pt throughout the case
-pacemaker tech- common in pts with VAD. program to asynchronous mode immediately prior to any surgery & antitacchycardia & defibrillator functions disabled
-post-op likely extubated but then to ICU, if minor procedure CCU may be appropriate
optimise intravascular volume, prevent hypox/hypercapnia (PVR), avoid nosocomial sepsis, adequate analgesia to limit SNS stimulation.
urgently assess any change in VAD functioning with echo.
keep pt connected to external defibrillator until any ICD or pacemaker is reprogrammed.
recommencement of anticoagulant & anti platelets is a multi-D discussion- no evidence incr thromboembolic risk if bridging heparin omitted yet no incr rate of periop bleeding or transfusion if use heparin- once acute bleeding risk passed, use UFH to bridge until INR >2.
What factors confound physical examination of pts with VADs?
arterial pulses typically non-palpable
NIBP requires portable continuous wave Doppler device
device hum obscures any HS & murmurs
Along with anticoagulation with warfarin, what else are pts with VADs on?
antiplatelet- aspirin or if aspirin resistance, clopidogrel added
What’s the anticoagulation plan for pts with VAD undergoing surgery?
elective: withhold warfarin for 5 days, bridge with UFH infusion once INR <2.0
emergency: reverse to INR <1.5 depending on procedure & pts thrombotic risk- should use a factor concentrate NOT vitamin K, given the pt will require warfarin reintroduction early postop
Why are major regional & neuraxial techniques typically avoided in pts with VADs?
risks ass’d with anticoagulation & higher incidence of hepatic dysfunction
What are the 2 most important haemodynamic goal for pts with a VAD?
maintaining normotension- both hypo- & hyper- tension impact VAD performance; target MAP 60-80mmHg
Avoid increased PVR- SO avoid hypercarbia & hypoxia; avoid hypoventilation with deep sedation or spontaneous vent on a LMA
How do preload & afterload impact a VAD?
preload dependent and afterload sensitive
What are the consequences of a MAP <60mmHg, above 80mmHg & >90mmHg on VAD performance?
<60mmHg risks causing or exacerbating end-organ dysfunction- particularly renal
>80mmHg adversely affects VAD performance, lower flow for a given pump speed
persistently >90mmHg associated with worsening AR, pump thrombosis & CVA
How achieve BP control intraop?
vasopressors or vasodilators- very rarely should VAD be changed perioperatively
How may the VAD have inadequate preload?
Any precipitant for RV failure (including excessive fluid) or hypovolaemia
How may TOE be useful intra-op for a pt with VAD?
diagnosing the cause of low VAD flows & guide therapy, eg. low preload to the VAD from RV dysfunction or hypovolaemia.
Why is milrinone a useful inotrope for RV dysfunction in pts with a VAD? what agent may need to be co-administered?
increases RV contractility + provides pulmonary VD
NAdr (low dose) may need to counteract milrinone-induced hypoT
How to correct hypercarbia without increasing RV afterload?
incr resp rate
What’s a suction event? how to manage?
where low preload to the VAD (either due to RV dysfunction or hypotension) causes the LV to “suck down” on the inflow cannula positioned @ the LV apex. The low flow alarm on the VAD is triggered, the pt becomes acutely hypotensive. LV dramatically reduced in size.
Malignant ventricular arrhythmias may ensue
Reduce pump speed to release the suction, slowly increase the pump speed over 30-60secs. Rx depending on cause (fluid for hypovolaemia or inotrope for acute RV failure)
For how long is bridging heparin infusion usually stopped prior to OT in a pt with a VAD? (of course whether to hold & duration depends on pt & procedure)
2-4hrs
Whats the rate of transfusion for pts with VADs undergoing non-cardiac surgery? main reason?
30%
improper warfarin preop
What are reasons, other than anticoagulation medication, that pts with VADs have higher bleeding risk? What could therefore rarely be considered for high bleeding risk procedures?
acquired von willebrand syndrome (device-related circulatory shear stress) & factor XIII deficiency.
desmopressin
Why may pts with VADs be at increased risk of GI bleeding (aside from anticoagulant meds, acquired VW syndrome & factor XIII deficiency)?
incr risk of developing GI AV malformations
Is infection within the VAD a concern?
yes. huge concern. risk sepsis & arterial embolisation. attention to aseptic technique vital. Broad spectrum ABx + consideration of anti fungal for GI tract. for others, commonly vancomycin & cefazolin. consider excluding the externalised driveline entry site from prep/drape to avoid contamination.
Which type of diathermy should be used for pts with VAD?
ideally bipolar, to avoid EMI. if no alternative to monopolar, place grounding pad as far as possible from the pump & driveline.
Who should control pt positioning?
cautious team- VAD specialist may be responsible for driveline, controller & power source- damage to the drive line could cause device malfunction (catastrophic)
How may pt position impact VAD function?
trendelenburg: increases Pit & augments RV filling which may adversely impact RV function, impairing preload to the VAD.
reverse trendelenburg: suddenly reduces preload to the VAD.
Avoid prone if possible.
How may pt pneumoperitoneum impact VAD function?
adversely; initially incr preload then venous return is reduced
raised IAP increases afterload
CO2 & SNS stimulation increase PVR
pneumoperitoneum may therefore reduce pump flow & precipitate a suction event
Pneumoperitoneum should be established in a step-wise manner allowing for circulatory support with fluids & vasopressors
Keep IAP <12cmH2O
avoid insufflation ports close to device or driveline
What’s an important perioperative consideration for VAD patients?
as per the International Society for Heart and Lung Transplantation, a cardiac surgeon should be immediately available for procedures in close proximity to a VAD
What are most likely causes of cardiac arrest in VAD patients?
ventricular arrhythmias
suction events
events unrelated to VAD (eg. anaphylaxis)
only rarely device malfunction the cause
What should occur if the pt has severe hypotension?
confirm the problem is real, inform OT team
inspect pt & listen to VAD hum
VAD specialist report pump speed & device flow
Echo useful for Ax cause hypoT
cardioversion & defibrillation are both safe for VAD electrical function
chest compressions are relatively contraindicated as may damage device but are recommended if sustained MAP <50mmHg or ETCO2 <20mmHg
if chest compressions done, echo post-resus to check inflow cannula & device functioning
