UDK 616.12-089
Review
Received: 3. November 2010
Accepted: 26. January 2011.
PostoPerative management of Patients after
vaD imPlementation
Nikola Bradić1, mislav Planinc2, stjepan Barišin1
1
Department of anesthesiology and intensive Care, University Hospital Dubrava,
Zagreb, Croatia; 2Department of Cardiac surgery, University Hospital Dubrava,
Zagreb, Croatia
Summary
After the implantation of the left ventricular assisted device (LVAD), patients are
admitted in intensive care unit (ICU). During the period of first several days, the goal of
the postoperative care is to stabilize the patients’ hemodynamics. Monitoring the continuous cardiac output, filling volumes and outflow resistance is necessary for the proper
functioning of the pump. The use of pulmonary artery catheter and the transesophageal
echocardiography are primary procedures. During the operation of the left ventricular support, the measuring of proper ventricular function and the early recognition of
its dysfunction is important for a positive outcome. Further potential complications in
connection with these patients are an increased risk of hemorrhage and thromboembolism. The infection of drivelines and devices in the early postoperative period occurs
in up to 40 % of these patients. In case of a cardiac arrest, a special procedure has to
be performed in patients in whom LVAD was implanted. Finally, we have shown the
anesthesiologic management in cases when patients with LVAD have to undergo noncardiac surgery.
Keywords: LVAD; hemodynamics; TEE; LVAD; noncardiac surgery
After the implementation of ventricular assisted device (VAD), patients are admitted to the intensive care unit (ICU). Recommendations for anesthetic approach
during the surgery suggest the use of total intravenous anesthesia (TIVA), in order to minimize the hemodynamic impact; e.g. TIVA technique using an opioid;
benzodiazepine such as midazolam; and long-acting muscle relaxant. Halogenated
anesthetic agents may be used as supplementation to intravenous anesthesia, but
only in patients who can tolerate them hemodynamically. In many centers, as well
Corresponding author: Nikola Bradić
E-mail: nbradic@kbd.hr
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N. Bradić: Postoperative management of patients after VAD implementation
as in ours, there is no advantage to attempting a “fast-track” approach, since these
patients are required to remain intubated overnight or longer, regardless of the type
of device implanted. During this period, it is important to stabilize the patients’ hemodynamics and coagulation, and perform the transesophageal echocardiography
to check VAD and heart function.
Hemodynamics
in all the patients undergoing the implantation of vaD, continuous hemodynamic monitoring has to be implemented. It is recommended to implant a catheter
for measuring both the continuous cardiac output (CCO) and the mixed venous
saturation (SvO2). The hemodynamic management of an LVAD patient is important,
as the pump function of each device depends on both the filling volume and the
outflow resistance. HeartMate, Novacor, and Thoratec pumps all exhibit sensitivity
to changes in the preload, especially when functioning in the “fill-to-empty” mode.
While these devices exhibit no Starling effect with respect to stroke volume or stroke
work, they can only pump the volume delivered to them, and inadequate filling will
result in a decreased flow through a decrease in the stroke rate. Thus, the maintenance of an adequate preload is of crucial importance. Direct decreases in the pump
flow occur when the preload declines, as a consequence of a decreased venous return secondary to an increased venous capacitance, alterations in the body position
that reduce the venous return (lateral decubitus or reverse Trendelenburg position),
inadequate administration of intravenous fluids, or uncontrolled surgical bleeding.
the preload sensitivity of these devices suggests that the invasive monitoring of
RV and pump filling pressures using a central venous, pulmonary artery catheter, or two-dimensional transesophageal echocardiography is necessary. Negative
inotropic drugs and factors that can reduce rv output by increasing pulmonary
vascular resistance (such as hypoxemia, hypercarbia or acidosis) should be avoided.
Progressive increases in the central venous pressure and rv dilatation, combined
with simultaneous reductions in LVAD output (or thermodilution-derived cardiac
output), are highly suggestive of RV dysfunction and may require an intervention
with either positive inotropic drugs (milrinone, dobutamine, or levosimendan) or
selective pulmonary vasodilators (inhaled nitric oxide or prostaglandins).
Right-sided circulatory failure
right-sided circulatory management is the key for successful postoperative
care in patients with left ventricular assist device (LVAD). The strategies include the
maintenance of chronotropy in the right ventricle (RV) and the decreasing of the
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N. Bradić: Postoperative management of patients after VAD implementation
pulmonary vascular resistance. Inhaled nitric oxide may be invaluable in the early
management of patients with LVAD, because its vasodilatative effect on pulmonary
vasculature without the systemic hypotensive effect is more potent than other pulmonary artery vasodilators. Further approaches include the use of a phosphodiesterase inhibitor (most frequently milrinone), nesiritide or levosimendan, usually
in combination with a systemic vasoconstrictor. In these patients, vasopressin has
an advantage over other alpha-adrenergic agonists, as it possesses minimal vasocostrictive effects on the pulmonary vasculature. The use of other systemic vasoconstrictors in patients with lvaD is common, as the systemic arterial vasodilation
commonly occurs due to various reasons.
Hemorrhage
Postoperative hemorrhage is common in these patients. The preoperative heart
dysfunction leads to hepatic congestion and renal dysfunction, both leading to imbalances in the platelet function and the coagulation cascade. An additional exposure of blood to foreign surfaces of cardiopulmonary bypass can exacerbate postoperative bleeding. In the intensive care unit, the prevention of bleeding is provided
with warming the patient and with replenishing of platelets and other factors of the
coagulation cascade. It is important that in patients, who are transplant candidates,
transfusions of platelets and erythrocytes should be given through leukocyte filters
to prevent develop antibodies against future donated organs. Fresh frozen plasma
and cryoprecipitate do not have a high leukocyte content, and they do not need
filtration.
Thromboembolism
Thromboembolism is associated with all current assist systems. The patient
with a novacor or thoratec device is chronically treated with warfarin, except Heartmate iP/Xve, which appears to have the lowest overall thromboembolic rate and
is generally maintained with chronic aspirin therapy alone.
Infection
Device-related infections are the most common cause of morbidity in the chronically supported patients. Driveline and device infections occur in up to 40 % of
these patients. The vast majority of these infections may be managed with chronic
antibiotic therapy until transplantation. The infection of the blood contacting surfaces of the device (valves or diaphragm) necessitates device change.
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N. Bradić: Postoperative management of patients after VAD implementation
Cardiac arrest
In case ventricular tachycardia or ventricular fibrillation occur, it is important
– though that device provides given cardiac output – to terminate these rhythm
disturbances, primarily due to extreme oxygen consumption. If external defibrillation/cardioversion is used, it is important not to disconnect the percutaneous lead
from the system controller and not to stop the pump prior to delivering the shock.
the percutaneous lead should only be disconnected in cases where open-heart defibrillation is required. In the event the LVAD stopped operating and blood were
stagnant in the pump and conduits for more than a few minutes (depending on
the anticoagulation status of the patient), a risk of stroke and/or thromboembolism
would exist if the device were restarted. Retrograde flow might occur during pump
stoppage. During cardiopulmonary resuscitation (CPR), external chest compressions should be avoided. External chest compressions pose a risk due to the location
of the outflow graft on the aorta and the inflow conduit in the left ventricular apex.
Dislodgement could lead to fatal hemorrhage. It is necessary to use clinical judgment
when deciding whether to perform external chest compressions in these cases.
Management of the VAD patients for noncardiac surgery
These patients can be very ill, and surgery can be contemplated early after VAD
implantation. After weeks or months after implantation, patients may safely undergo noncardiac surgical procedures, with attention on several details. Anesthetic
induction with sedative–hypnotic drugs, which increase venous capacitance (thiopental, propofol), or rapid administration of other vasoactive drugs, which produce
selective dilation of the venous circulation, may produce acute hemodynamic decompensation in the LVAD patient, because the pump blood-flow decreases during
these conditions. As a result, hypertension should be specifically avoided, because
the emptying of the LVAD is reduced by increases in the arterial pressure. Incomplete LVAD ejection does not only decrease the forward flow, but rather promotes
the blood stasis within the device and increases the risk of thrombus formation,
even in the presence of systemic anticoagulation. Acute increases in the sympathetic
nervous system activity and its consequent effects on the arteriolar tone, produced
by laryngoscopy, intubation, or surgical stimulation, represent an important goal in
the perioperative management of these patients. These may be avoided by the assurance of adequate anesthetic depth, using volatile anesthetics in combination with
an opioid or by the judicious administration of arterial vasodilators to treat increases in the arterial pressure. In the absence of hypertension, most cases of low LVAD
flow can be corrected by volume expansion, though RV dysfunction must also be
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N. Bradić: Postoperative management of patients after VAD implementation
considered. The management of anticoagulant therapy is another major issue that
requires attention in the perioperative care of the LVAD patient. Patients with a Novacor or thoratec device, chronically treated with warfarin, should be converted
to intravenous heparin therapy before elective surgery, similar to patients with a
mechanical prosthetic valve. The heparin should be discontinued during the immediate preoperative period and resumed when the risk of postoperative bleeding diminishes. During emergency circumstances, the withdrawal of oral anticoagulants
may not be accomplished before surgery, and the transfusion of fresh frozen plasma
is required. Patients with HeartMate device are generally maintained with chronic
aspirin therapy alone, and excess perioperative bleeding may require platelet transfusion to obtain adequate hemostasis.
References
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heart failure. In: Kaplan JA (ed) Essentials of cardiac anesthesia. Saunders Philadelphia 2008; pp 492-510.
[3] Nicolosi AC, Pagel PS. Perioperative Considerations in the Patient with a Left
Ventricular Assist Device. Anesthesiology 2003; 98:565–570.
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[6] John R, Kamdar F, Liao K, Colvin-Adams M, Miller L, Joyce L, Boyle A. low thromboembolic risk for patients with the Heartmate II left ventricular assist device.
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[7] Haft J, Armstrong W, Dyke DB, Aaronson KD, Koelling TM, Farrar DJ, Pagani FD.
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[8] Matthews JC, Koelling TM, Pagani FD, Aaronson KD. the right ventricular failure risk score-a Pre-operative tool for assessing the risk of right ventricular
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Sažetak
Postoperacijsko liječenje bolesnika s mehaničkom potporom srca
u jedinici intenzivnog liječenja
Nakon ugradnje lijevostrane srčane potpore (LSP), bolesnici se zaprimaju u jedinicu intenzivne medicine. Tijekom ovog razdoblja od nekoliko dana, osnovni cilj poslijeoperacijskog liječenja je stabilizacija bolesnikove hemodinamike. Praćenje kontinuiranog minutnog volumena,
tlakova punjenja i sustavne rezistencije je neophodno za ispravno funkcioniranje LSP-a. Uporaba
plućnog arterijskog katetera s kontinuiranim mjerenjem minutnog volumena te transezofagijska
ehokardiografija su primarni postupci. Za vrijeme rada LSP, praćenje funkcije desne klijetke te
rano uočavanje njene disfunkcije od krucijalnog su značaja za dobar ishod bolesnika. Daljnje
moguće komplikacije u ovih bolesnika su povećani rizik od krvarenja, kao i od nastanka tromboembolija. Incidencija infekcija u ovih bolesnika je visoka, i kreće se do 40%, osobito infekcije
kanila. U slučaju zastoja rada srca, primjenjuju se posebni postupci oživljavanja, koji se razlikuju
od uobičajenih algoritama. Na kraju, prikazane su i specifičnosti anesteziološkog postupka u
ovih bolesnika ukoliko postoji potreba za nekardijalnom operacijom.
Ključne riječi: LVAD; hemodinamika; TEE, LVAD i nekardijalne operacije
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