Insertion of Durable Ventricular Assist Devices

What the Anesthesiologist Should Know before the Operative Procedure

What is a Ventricular Assist Device (VAD)?

A ventricular assist device (VAD) is a mechanical pump that replaces a portion of the native function of either the left (LVAD) or right ventricle (RVAD) by diverting blood away from the diseased ventricle and pumping it directly into its associated great vessel. The VAD system consists of several main components:

• an inflow cannula attached to either the LV apex or RV

• a pump which circulates blood drawn from the inflow cannula into the systemic or pulmonary vasculature via the outflow cannula

  ---

  Continue Reading

• an outflow cannula that delivers blood from the pump into either the ascending aorta (for LVAD) or pulmonary artery (for RVAD)

• a driveline attached to the pump that exits the body and connects to an external monitor and battery pack

Since the first-generation of pulsatile VADs were approved by the FDA in the 1990s, VADs have evolved considerably. Current devices are significantly smaller than their predecessors, have continuous-flow technology, and are far less susceptible to mechanical wear. The devices most commonly implanted today are the Thoratec^® HeartMate II^® (HMII) and the HeartWare^® HVAD^®. The HMII is second-generation, axial pump that sits in a pre-peritoneal or abdominal space (see Figure 1). The HVAD is a third-generation, centrifugal pump that sits in the pericardial space (see Figure 2). Both devices can generate up to 10 L/min of flow. Newer, even smaller versions are currently undergoing clinical trials, including the third-generation, centrifugal flow Thoratec^® HeartMate III^® and the fourth-generation, axial flow HeartWare^® MVAD^®.

Figure 1.

Figure 2.

How do VADs work?

LVADs offload a failing LV by taking over native LV pump function. As a result, the dilated LV will decompress and mitral regurgitation (MR) is often reduced. The LVAD is preload-dependent and relies the RV to deliver its volume. LVADs are also afterload-sensitive; high systemic MAPS can impede LVAD forward flow. The goals of VAD management are to maintain preload, optimize RV function, and minimize afterload.

The operator can change only one variable on the VAD control monitor: the VAD speed in rotations per minute (RPM). The HMII allows for speeds of 6,000 to 15,000 RPMs; speeds are usually set around 9,000 RPMs. The HVAD allows for speeds of 1,800 to 4,000 RPMs with recommended speeds being in the range of 2,400 to 3,200 RPMs. The console will display the set speed, the power generated by the pump (measured), flow through the pump in L/min (calculated), and a display of pulsatility which represents change in the flow through the pump over time.

Other than pump speed, all of the VAD parameters are influenced by preload, afterload, and native contractility.

Surgical Considerations

Most LVADs are implanted via median sternotomy incision. Minimally invasive techniques have been described for HVAD implantation, consisting of a combination of mini-sternotomy and left mini-thoracotomy incisions. The newer generation MVAD^® is designed to be placed via left thoracotomy. Cardiopulmonary bypass (CPB) is almost always used for VAD implantation; standard arterial and venous cannulation is usually sufficient. Aortic cross-clamp and cardiac arrest are not required, unless concomitant procedures are performed, such as valve surgery or closure of a patent foramen ovale (PFO). When attempted chest closure leads to hemodynamic instability, typically caused by right heart failure, the sternum is left open at the end of the surgery and closed once right heart function improves.

What are the indications for VAD placement?

LVADs are inserted as a treatment for advanced heart failure (AHA/ACC stage D) in patients who have failed maximal medical therapy. There are three indications for LVAD placement: destination therapy (DT) for patients who are not candidates for heart transplant, bridge-to-transplant (BTT) for patients who are waiting for a transplant but have not yet received an organ, and bridge-to-candidacy (BTC) for patients who are not currently transplant candidates but may become transplant-eligible after a course of LVAD therapy. For example, severe pulmonary hypertension is often a contraindication to heart transplant, but this can improve significantly after LVAD implantation due to remodeling of the pulmonary vasculature.

The HMII^® is FDA-approved as both BTT and DT therapy and the HVAD^® is approved for as BTT therapy but is often placed off-label for DT therapy. There are case reports of two HVAD^® devices being placed concurrently in the LV and RV for biventricular support. Survival of patients with advanced heart failure has improved significantly since the initiation of LVAD therapy, but prognosis for patients requiring biventricular durable VAD support is still poor. It is rare to place a durable RVAD in absence of an LVAD. Neither device in use today is FDA-approved for RVAD use.

What are the contraindications for VAD placement?

Patients with any contraindication to anticoagulation cannot undergo VAD implantation, as they will need ongoing anticoagulation to reduce the risk of pump thrombosis.

Patients with either a systemic infection or infection localized to the incision or driveline site should not have any foreign device placed until infection has cleared.

Patients must be mentally and physically capable of caring for and troubleshooting their device; they must also have social support in place to help them do so.

There are several cardiac conditions that are relative contraindications to VAD placement; they interfere with optimal VAD functioning and must be addressed surgically at the time of VAD implantation. Aortic insufficiency (AI) reduces effective cardiac output by allowing blood from outflow cannula to be pumped in a retrograde direction through the incompetent aortic valve back into the LV, creating circular flow between LVAD and LV. Anything beyond mild AI should be addressed, either by bioprosthetic aortic valve replacement or by oversewing the aortic valve to prevent any flow through the valve. Mitral stenosis (MS) impedes LVAD filling by restricting blood flow into the LV; this must be rectified via bioprosthetic mitral valve replacement or mitral commissurotomy. Mechanical valves are not used as they require a higher INR goal than VADs alone and may lead to increased risk of bleeding and/or thrombosis. Severe tricuspid regurgitation (TR) from a dilated tricuspid annulus may increase risk of RV failure following LVAD placement; tricuspid ring annuloplasty has been described to reduce the risk of RV failure.

Thrombus in the LV or the left atrial appendage (LAA) is not an uncommon phenomenon in patients with very low cardiac output; these clots must be removed prior to turning the LVAD on to prevent pump thrombosis and systemic thromboembolism.

PFOs and atrial septal defects (ASDs) must be repaired at time of LVAD implantation. Defects in the interatrial septum would allow for right-to-left shunting once the LVAD was turned on and left sided pressures were reduced, resulting in hypoxia.

Patients with severe RV dysfunction undergoing LVAD placement may require concomitant RVAD placement (either durable or temporary). RVAD implantation may either be pre-planned, or placed as a rescue device in patients unable to wean from CPB due to RV failure.

Tricuspid stenosis and moderate or severe pulmonary insufficiency would have similar implications to RVAD implantation as MS and AI in LVAD implantation. These valvular lesions should be fixed at time of RVAD implantation.

What types of patients present for VAD implantation?

As mentioned above, patients requiring VAD implantation will have AHA/ACC stage D heart failure, and will have failed maximal medical therapy. Within this population, patients will present in a wide range of hemodynamic conditions, from stable at home to “crashing and burning”. The Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) has developed profiles for patient status at the time of VAD implantation (see Table I). The vast majority of patients undergoing LVAD or BiVAD implantation fall into INTERMACS Levels 1-4, which includes patients in critical cardiogenic shock, patients with progressive decline in functional status, patients who are stable but inotrope-dependent, and patients with heart failure symptoms at rest, respectively. Some patients may also have an intra-aortic balloon pump (IABP) prior to surgery.

Table I.

What is the urgency of the surgery?

What is the risk of delay in order to obtain additional preoperative information?

The urgency of the surgery is dependent on the hemodynamic status of the patient.

Emergent surgery

Surgery should proceed in an emergent fashion in patients in critical cardiogenic shock (INTERMACS Level 1 patients). These patients may go to the OR to have a durable VAD implanted, or in some situations, may have a temporary VAD or extracorporeal membrane oxygenation (ECMO) cannulas placed either surgically or percutaneously. Temporary VADs and ECMO will be discussed in a separate chapter. These patients are gravely ill, and may be on multiple inotropes and vasopressors, and/or intubated requiring mechanical ventilation. Delaying surgery for further pre-operative workup in these situations is not advisable, as the patient may not survive the delay.

Urgent surgery

Patients who fall into INTERMACS Levels 2 and 3 (progressively declining, and stable but inotrope-dependent) require surgery in a matter of days to weeks. Level 3 patients on inotrope infusions may be at home (on milrinone and/or dobutamine), or may be admitted to the hospital, often waiting for a heart transplant. Delaying surgery for further workup or medical management in these patients may be warranted, depending on the patient’s status. For example, hemodynamically stable patients on chronic anticoagulation therapy can be bridged with a heparin infusion in the pre-operative period.

Elective surgery

Patients who are INTERMACS Level 4 (stable, with symptoms at rest), can undergo elective scheduling of VAD placement. These patients are usually at home, and can tolerate delays in surgery to complete pre-operative workup and optimize medical therapy.

2. Preoperative evaluation

The pre-operative evaluation for patients undergoing durable VAD implantation should be extensive, and include a thorough investigation of all cardiopulmonary, neurologic, gastrointestinal, hepatic, renal, and hematologic disorders.

a. Cardiovascular

The cardiovascular evaluation should include the following:

The preoperative TTE provides important information such as LV and RV size and function, presence of LV or LAA thrombus, severity of valvular disorders, and presence of PFO or ASD. Many of these lesions will affect the surgical procedure performed. If the TTE is inconclusive for PFO or thrombus, a preoperative transesophageal echocardiogram (TEE) may be performed for clarification.

Right heart catheterizations (RHC) are often performed in patients with advanced heart failure, to assess cardiac function, measure pulmonary vascular pressures and monitor the effectiveness of inotropic therapy. Important information gleaned from the RHC are cardiac index, pulmonary artery pressures, and pulmonary vascular resistance.

Left heart catheterization (LHC) should be performed in patients with known ischemic cardiomyopathy to ensure there is no further treatment (percutaneous intervention or surgical bypass grafting) that may improve myocardial function prior to VAD insertion. LHC should also be performed on patients with a diagnosis of non-ischemic cardiomyopathy to rule out an ischemic component of their disease.

Patients with prior sternotomy may undergo thoracic CT scan to evaluate the position of heart relative to the sternum. The results may determine whether the surgeon cannulates peripherally prior to sternotomy.

b. Pulmonary

Many patients with advanced heart failure have coexisting COPD. Preoperative pulmonary function tests may be indicated to grade severity of COPD and response to bronchodilators. In addition, patients in decompensated heart failure often have pulmonary edema or pleural effusions due to volume overload. A chest x-ray is always indicated preoperatively to evaluate lung fields. Interviewing the patient to determine whether he or she can comfortably lay flat will be important for planning anesthetic induction.

c. Neurologic

Patients with neurological impairment should receive a full workup prior to surgery. Appropriate mentation is imperative for the patient to care for and troubleshoot the VAD. In patients in critical cardiogenic shock, the neurological status of the patient may not be known. If there is concern for devastating neurologic injury, VAD implantation may not be indicated.

d. GI/Hepatic

Liver congestion secondary to right heart failure may be present in patients presenting for VAD placement. Patients in acute decompensated heart failure may have shock liver. Evaluation of liver function should include liver function tests, and synthetic function such as albumin and INR (in patients who are not medically anticoagulated). Liver ultrasound may also be indicated.

e. Renal

Patients with advanced heart failure often have chronic renal insufficiency due to low cardiac output and resultant renal malperfusion. Patients with acute decompensated heart failure will have acute kidney injury. Pre-operative workup should include evaluation of kidney function, including measuring current blood urea nitrogen and creatinine levels, and comparing them to historical values. Renal ultrasound may be indicated to rule out other causes of renal dysfunction.

Most patients are severely volume overloaded. These patients will likely be on chronic loop diuretic therapy but may be relatively resistant to effects. Assessing and managing volume status prior to surgery is critical.

Electrolytes should be measured, and optimized prior to surgery. Potassium and magnesium are often low due to diuretic use, and should be replaced to reduce risk of perioperative arrhythmias. Alternatively, patients with failing kidneys may be hyperkalemic and require dialysis.

f. Heme

Patients are often on anticoagulation and/or antiplatelet therapy. The INR, PTT, platelets, and hemoglobin should be evaluated prior to surgery. The benefit of holding anticoagulation and anti-platelet therapy to reduce perioperative bleeding should be weighed against the risk of developing intracardiac thrombus or in-stent thrombosis.

g. Endocrine

Patients with diabetes mellitus (DM) benefit from blood glucose control prior to surgery to optimize wound healing. Blood glucose and hemoglobin A1c should be measured and insulin therapy started if necessary.

h. Infectious Disease

Any suspicion of infection, including elevated white blood cell count, positive blood cultures, ongoing fever and endocarditis, should be thoroughly investigated. A durable VAD should not be placed in a patient with systemic infection or local infection at sternum or driveline insertion site.

3. What are the implications of co-existing disease on perioperative care?

a. Cardiovascular system

As mentioned previously, patients may have unstable hemodynamics and be on multiple inotropes and vasopressors. An IABP may be in place. The goals of therapy include maintaining cardiac output, and avoiding tachycardia and hypotension. Adding or increasing inotropes or vasopressors may be indicated.

Patients with ischemic cardiomyopathy often have had prior coronary bypass grafting surgeries, and will undergo a redo sternotomy for LVAD placement. The anesthesiologist must be prepared to quickly transfuse blood products in the event that sternotomy or dissection results in significant bleeding.

Many patients with stage D heart failure will have cardiac implantable electrical devices (CIEDs) for a variety of reasons, including pacing-dependent lesions, cardiac resynchronization therapy, or defibrillation for malignant heart rhythms. A thorough knowledge of patient’s electrophysiology history and how to appropriately reprogram the device for surgery is necessary.

b. Pulmonary

Coexisting COPD may alter ventilator management in the perioperative period. Hypercarbia and hypoxia should be avoided to optimize RV function both before and after LVAD placement.

c. Renal/GI

Renal dysfunction may worsen in the early post-operative period due to preoperative dye loads or intraoperative hypotension. However, renal function often improves after LVAD placement due to improved blood flow to kidneys. Preoperatively, volume status should be optimized with diuretics, fluid restriction, and ultrafiltration, if necessary.

The presence of significant liver dysfunction should warrant re-evaluation of surgical risk, as these patients are unlikely to do well following VAD implantation.

d. Neurologic

As discussed previously, significant cognitive impairment and limitation of physical activity, such as hemiparesis or hemiplegia, can impair the ability to operate the VAD effectively. Any suspicion of neurologic impairment should be thoroughly investigated to rule out contraindications to VAD insertion. The anesthesiologist should consider intraoperative cerebral oximetry in patients with prior stroke or current carotid artery stenosis to monitor cerebral perfusion.

e. Endocrine

Blood sugar in patients with DM should be managed with insulin as needed. Patients without DM often experience stress-induced hyperglycemia due to cardiac surgery; these patients should also receive insulin therapy. Patients on chronic corticosteroids should receive stress-dose steroids to combat intraoperative adrenal insufficiency.

g. Additional systems/conditions which may be of concern in a patient undergoing this procedure and are relevant for the anesthetic plan (e.g., musculoskeletal in orthopedic procedures, hematologic in a cancer patient)

Patients undergoing VAD implantation often have multiple hematologic issues that significantly increase the risk of post-bypass bleeding. These patients may have preexisting coagulopathy or platelet dysfunction secondary to their chronic heart failure. Many are on chronic anticoagulation therapy to treat or reduce risk of developing intracardiac thrombus. Patients with ischemic disease and coronary stents may be on anti-platelet agents. Prior sternotomy for coronary artery bypass grafting surgery or other cardiac procedures increases the risk of perioperative bleeding, both due to adhesions and the possibility of ventricular injury with re-do sternotomy.

h. Are there medications commonly seen in patients undergoing this procedure and for which should there be greater concern?

• Chronic drug therapy

  Angiotensin converting enzyme (ACE) inhibitors

  Angiotensin receptor blockers

  Beta blockers

  Antiplatelet agents (clopidogrel)

  Anticoagulation (warfarin)

  Diuretics

  Inotropic infusion (milrinone and dobutamine) – indication of severity of heart failure

  Antiarrhythmics (amiodarone)

• Acute drug therapy

  Inotropes and vasopressor infusions, (epinephrine, norepinephrine, dopamine) – indication of critical status of patient

  Heparin infusion, either as bridge from warfarin or a new therapy

  Antiplatelet infusion (eptifibatide)

  Nitroglycerin infusion

i. What should be recommended with regard to continuation of medications taken chronically?

ACE inhibitors taken in the preoperative period can result in profound intraoperative hypotension. If possible, ACE inhibitors should be held 1-2 days prior to surgery.

When patients are stable enough to delay surgery, chronic anticoagulant therapy should be bridged with a heparin infusion. Likewise, for elective surgery, patients with recent stent placement may have antiplatelet COX-2 inhibitors held 7-10 days prior to surgery. However, the risk of in-stent thrombosis should be weighed against the increased risk of surgical bleeding. If VAD placement is emergent after recent MI and PCI, patient may also be on an infusion of glycoprotein IIb/IIIa inhibitors and have a significant risk of increased bleeding.

Inotropes and vasopressors should be continued through the perioperative period.

j. How to modify care for patients with known allergies?

Those with a history of heparin induced thrombocytopenia (HIT) present a special challenge. These patients may have persistent antiplatelet antibodies for up to six months following the last heparin exposure. However, it may be prudent to administer a one-time dose of heparin if six months or more have passed since the last exposure. Alternately, other agents, such as bivalirudin, may be useful for anticoagulation for CPB. Unfortunately, utility of these agents are limited by lack of a suitable reversal agent. Preoperative plasmapheresis is an option which will reduce heparin-PF4 antibodies, allowing for safe perioperative administration of heparin. Thorough discussion and planning with the surgical and perfusion teams are essential prior to surgery; a hematology consult may also be necessary.

Patients with known sensitivity to protamine may also present a special challenge. These cases may require a test dose to confirm true sensitivity and premedication with antihistamines and steroids. Alternatives to protamine are rarely used.

k. Latex allergy- If the patient has a sensitivity to latex (e.g., rash from gloves, underwear, etc.) versus anaphylactic reaction, prepare the operating room with latex-free products.

Latex allergy is not uncommon in the perioperative setting. Most modern operating rooms are adequately equipped with non-latex equipment to be used for the surgery. However, some pulmonary artery (PA) catheter balloons contain latex. This should be confirmed before placing a PA catheter in a patient with latex allergy.

l. Does the patient have any antibiotic allergies – Common antibiotic allergies and alternative antibiotics

See antibiotic section below.

m. Does the patient have a history of allergy to anesthesia?

If a patient has a documented case of malignant hyperthermia (MH), standard precautions should be taken, including avoiding all trigger agents, such as succinylcholine, and inhalational anesthetics. An important consideration that is often overlooked is the volatile agent included in the CPB circuit; this should be replaced with a total intravenous anesthetic. Clear communication with the perfusion team regarding the anesthetic plan is essential.

5. What laboratory tests should be obtained and has everything been reviewed?

In addition to the preoperative evaluation previously discussed, the following laboratory tests and studies should be performed immediately prior to surgery: comprehensive metabolic panel, LFTs, complete blood count, INR, PTT, type and cross, EKG and CXR. There will not be time for an extensive workup of Level 1 INTERMACS patients presenting for emergent VAD placement. However, type and cross of appropriate blood products is essential.

Intraoperative Management: What are the options for anesthetic management and how to determine the best technique?

a. Regional anesthesia –Regional anesthesia is not indicated for this procedure.

b. General anesthesia – General anesthesia is the technique of choice in these cases.

Pre-induction

For the anesthesiologist, induction of general anesthesia will be one of the most challenging parts of the case. In addition to standard ASA monitors, a large bore intravenous line and an arterial line are mandatory prior to induction of anesthesia. Patients on preoperative inotrope therapy will already have central access; some may also have a PA catheter in place. Inotrope infusions should be continued throughout the pre-bypass period. Patients not on preoperative inotropic therapy may or may not require placement of pre-induction central access and pulmonary arterial monitoring; the anesthesiologist should use his or her judgment. If patient does not have implanted cardioverter defibrillator (ICD), defibrillator pads should be placed pre-induction and connected to the defibrillator.

Induction

These patients have extremely poor cardiac function and limited cardiac reserve. Low cardiac output equates to a prolonged circulation time, making it important to administer induction agents slowly. A judicious combination of opioids such as fentanyl, benzodiazepines such as midazolam, and volatile agents may be sufficient for induction. Small doses of propofol or etomidate may be also be used. Boluses or infusions of inotropes or vasopressors may be necessary to combat the hemodynamic effects of induction agents. Care should be taken to ensure cardiovascular stability during this critical phase.

Monitoring and Positioning

Following induction, central access should be obtained and PA catheter placed if not done previously. Large bore intravenous access (both peripherally and centrally) is required. Other monitoring should be considered, such as cerebral oximetry, bispectral index, and multiple temperature sites (bladder and nasal). TEE probe should be placed and full exam performed; results should be communicated to surgeon (see below for further details). Patient will be positioned supine with arms tucked; ensure proper functioning of arterial lines and peripheral iv in final position prior to surgical prep.

CIED

If patient has a CIED in place, it should be appropriately reprogrammed prior to incision to avoid potentially dangerous electrocautery interference. Therapy to treat ventricular tachycardia and fibrillation (VT/VF) should be disabled once external defibrillator pads are in place. In patients who are pacemaker-dependent, the pacemaker should be reprogrammed to an asynchronous mode.

Maintenance and Weaning from CPB

Maintenance of anesthesia is accomplished with a combination of opioids, volatile agents and muscle relaxants. Vasopressor agents or inotropes may need to be initiated or increased to maintain cardiovascular stability prior to initiation of CPB. On CPB, inotropes can be discontinued, but vasopressor infusions may be necessary to maintain adequate systemic perfusion. Frequent communication with the perfusionist is necessary to achieve hemodynamic goals. Prior to weaning CPB, inotrope infusions should be started to optimize post-bypass RV function; epinephrine and milrinone are commonly used. Vasopressor infusions should be titrated to maintain adequate MAPs for RV and systemic perfusion, but not so high to impede LVAD forward flow. MAPs between 60-80 mm Hg are often appropriate.

Transfusion

Blood products should be available throughout the case. Administration of antifibrinolytic infusions such as aminocaproic acid or tranexamic axid is routine. Prior to discontinuation of CPB, a plan should be developed to manage any coagulopathy that may occur. Packed RBC are administered on CPB as needed. Several units of fresh frozen plasma (FFP) are often given either prior to or immediately following liberation from CPB. Post-bypass, protamine is administered to reverse the effects of heparin. Platelets (PLT) and cryoprecipitate are commonly given thereafter, often empirically. Any further bleeding can be treated with FFP, PLT, cryoprecipitate, prothrombin complex concentrates (PCCs) such as Profilnine^®, Kcentra^®, and FEIBA^®, and/or factor VII concentrates such as NovoSeven^®. Factor concentrates have the benefit of limiting volume in a patient who is already volume overloaded, as well as reducing exposure to antigenic compounds in BTT patients. However, these agents must be used judiciously to avoid development of thrombus that could interfere with pump function or result in systemic thromboembolism. Laboratory studies such as platelet count, fibrinogen, INR, PTT, and thromobelastography (TEG^® or ROTEM^®) should be used to guide post-bypass blood product administration.

Other

Once LVAD is turned on, a post-bypass TEE exam should be performed (see below). At the end of the case, the CIED should be reprogrammed to appropriate settings, which will likely include restoration of VT/VF therapy and overdrive pacing at a rate between 90-110 bpm.

c. Monitored Anesthesia Care – Monitored anesthesia care is not indicated for this procedure.

6. What is the author's preferred method of anesthesia technique and why?

a. What prophylactic antibiotics should be administered?

Antibiotics should be administered within 1 hour prior to skin incision. Antibiotic coverage varies extensively among institutions but should cover skin and GI flora, with strong consideration for antifungal coverage. An antibiotic with MRSA coverage should be selected for hospitalized patients, known carriers, and patients with risk factors. Ultimately, antibiotic selection must reflect local pathogens and sensitivities and address patient allergies. At our institution, we currently use a combination of tigecycline, imipenem and fluconazole.

b. What do I need to know about the surgical technique to optimize my anesthetic care?

As discussed previously, most VADs are implanted via median sternotomy with standard cannulation sites. Cases with prior sternotomy may require alternate approaches to the aorta. The axillary artery or femoral artery may be cannulated to initiate bypass prior to sternotomy. It is always prudent to discuss these approaches with the surgical team since approaches like axillary artery cannulation may affect blood pressure monitoring with a radial arterial line on the same side. If there is significant risk of ventricular injury with sternotomy, based on the preoperative CT scan, the anesthesiologist should consider having a rapid infuser available to deliver large amounts of warmed blood products. The patient may require additional surgery to repair cardiac lesions such as valvular stenosis or regurgitation, or PFOs, as mentioned above. These additional procedures will require longer bypass times, cardiac arrest and often aortic cross clamping. Risks of bleeding and RV dysfunction will be increased and should be considered when developing a plan for weaning from CPB.

c. What can I do intraoperatively to assist the surgeon and optimize patient care?

Communication regarding TEE findings are essential for the surgical team to plan the surgical procedure. The pre-bypass exam should include evaluation of LV function and RV function, assessment of AI, MS, and TR severity, presence of thrombus, and investigation of PFO with bubble study. A PFO not be evident pre-bypass, even with a proper bubble study, given the high pressures in the LA. Many of these findings may alter the surgical plan. Once on CPB, the surgeon may ask for TEE visualization of the LV apex to determine adequate positioning for VAD apical ring. Post CPB, prior to starting LVAD, de-airing under TEE visualization is crucial. Following initiation of LVAD flows, TEE exam should include size of LV (which should be decompressed compared to prior), position of inflow cannula (ideally directed toward mitral valve opening and away from all LV walls), Doppler velocities of inflow and outflow cannula to evaluate for obstruction, position of interventricular septum (IVS), RV size and function, TR severity, opening of aortic valve, and re-evaluation of PFO with bubble study. With high LVAD speeds, the IVS can shift towards the LV and distort the geometry of the RV, leading to worsening TR and RV function. TEE can help guide setting of appropriate LVAD speed and decision to place RVAD in a failing RV.

Any findings of decrease in cerebral oximetry values while on CPB should be communicated to the perfusionist, as they can decrease sweep speed of carbon dioxide to promote vasodilation of cerebral vasculature. Once LVAD is turned on, decrease in cerebral oximetry or bispectral index may indicate a problem with VAD flow; the surgical team should be notified immediately.

d. What are the most common intraoperative complications and how can they be avoided/treated?

The most common intraoperative complications relate to the cardiovascular system. Patients will frequently display hypotension and low cardiac output prior to initiation of bypass, due to the vasodilatory and myocardial depressant effects of anesthesia medications. These should be anticipated and treated with inotropes and vasopressors, as appropriate. Dysrhythmias should be promptly treated, especially those requiring electrical conversion, as patients may have their rhythm management devices disabled.

RV Failure

RV failure is a serious complication and can occur after LVAD insertion. A number of factors contribute to RV failure. Patients with left sided heart failure often have some degree of pre-existing RV dysfunction. Once the LVAD is turned on, the thin-walled, already dysfunctional RV is now responsible for providing all preload to the LVAD, in addition to receiving a full complement of venous return from the LVAD. As discussed above, high LVAD speeds can distort septal geometry and worsen RV function. Volume resuscitation and blood transfusion in the post-bypass period contribute to distension of the RV.

There are variety of techniques that can be employed to prevent and treat RV failure in patients with LVAD. Hypotension should be avoided to maintain perfusion to the right coronary artery (RCA) and RV. Thorough de-airing should be performed prior to weaning from bypass to prevent air embolus down the RCA. Euvolemia should be maintained as the LVAD is preload dependent; however, RV volume overload should be avoided to prevent tricuspid annular dilation and worsening of TR. RV distension can be prevented with judicious fluid and blood product administration, and rapid pacing to reduce diastolic filling time. In addition, the perfusionist can remove volume via ultrafiltration while on CPB. RV contractility should be optimized with inotropes. Afterload reduction of the RV is accomplished with inhaled pulmonary vasodilators such as nitric oxide or prostaglandin analogues, as well as the avoidance of hypothermia, hypoxemia, hypercarbia, and acidemia, all of which can result in pulmonary arterial vasoconstriction.

When severe RV dysfunction persists despite optimizing these techniques, insertion of temporary or durable RVAD may be indicated.

Bleeding

The other major intraoperative complication relates to bleeding. A combination of CPB and exposure of blood elements to the synthetic surface of the VAD chamber can result in a significant coagulopathy. In addition, acquired von Willebrand disease occurs immediately upon initiation of LVAD flows. Management of coagulopathy is discussed above.

b. If the patient is intubated, are there any special criteria for extubation?

Patients are left intubated in the postoperative period until they are hemodynamically stable, with minimal bleeding, and have satisfactory arterial blood gas results. Pain must be well controlled and patient must be fully awake prior to extubation, to avoid increases in pulmonary vascular resistance or hypercarbia that could result in worsened RV function. If the sternum was left open at the end of surgery, patients should remain intubated until chest closure.

Postoperative management

1. What analgesic modalities can I implement?

A multi-modal approach to postoperative analgesia is usually successful, to include systemic opioids, acetaminophen, and/or gabapentin. Ketamine or lidocaine infusions can be considered for patients with chronic pain or opioid tolerance. Postoperative neuraxial analgesia is contraindicated due to coagulopathy and need for anticoagulation.

2. What level bed acuity is appropriate?

Patient receiving VADs will require intensive care unit (ICU) admission for at least several days postoperatively. Complications such as bleeding, RV failure, and respiratory failure may result in longer ICU stays. The nursing staff caring for patients with VADs require specialty training, both in the ICU and on general wards. This often will limit patient placement to certain hospital locations.

3. What are common postoperative complications, and ways to prevent and treat them?

Unfortunately, complications following VAD implantation are frequent and can be very serious. The most common complications in the early post-operative period are RV failure and bleeding. Prevention and treatment of these complications should be prioritized.

RV Failure

Ways to prevent and treat RV failure are discussed above. Inotropes are often weaned slowly, over the course of several days, until there is return of adequate native RV function. Pulmonary vasodilators are also continued several days into the post-operative period.

Bleeding

Postoperative coagulopathy is common. Strict monitoring of the coagulation profile is mandatory, as is prompt treatment with appropriate blood products. Caution should be exercised in patients who have had a VAD placed as a bridge to transplant. Unnecessary blood transfusion can sensitize a potential heart transplant candidate to major histocompatibility complex (MHC) antigens, which can result reduce potential donor pool and increase risk of allograft rejection.

Arrhythmias

Perioperative arrhythmias are common, especially in patients with pre-existing arrhythmias. Atrial fibrillation with rapid ventricular response is frequent in this patient population and is usually treated with amiodarone or cardioversion. Ventricular arrhythmias (VAs), especially monomorphic ventricular tachycardia, are also common. Arrhythmias result in hemodynamic instability when RV filling of the LVAD is impaired; immediate treatment with synchronized cardioversion or defibrillation is indicated in the unstable patient. Lidocaine and amiodarone are also useful in the management and suppression of VAs.

Infection

Prolonged courses of prophylactic antibiotics are often implemented as the impact of systemic infection on a prosthetic device such as a VAD can be devastating.

Copyright © 2017, 2013 Decision Support in Medicine, LLC. All rights reserved.

No sponsor or advertiser has participated in, approved or paid for the content provided by Decision Support in Medicine LLC. The Licensed Content is the property of and copyrighted by DSM.