Management of special populations during cardiac surgery with cardiopulmonary bypass

INTRODUCTION — Cardiopulmonary bypass (CPB) is a form of extracorporeal circulation in which the patient's blood is diverted from the heart and lungs and rerouted outside of the body during cardiac surgery. The normal physiologic functions of the heart and lungs, including circulation of blood, oxygenation, and ventilation, are temporarily taken over by the CPB machine. In most cases, the heart is also separated from the circulation via aortic cross-clamping and cardioplegia solution is administered to protect the nonperfused myocardium. This allows the surgeon to operate on a nonbeating heart in a field largely devoid of blood, while other organs remain adequately oxygenated and perfused.

This topic will discuss strategies for patients with conditions that affect management of CPB including:

●Previous sternotomy

●Aortic regurgitation

●Cerebrovascular disease

●Chronic kidney disease

Hematologic issues that affect management of CPB are discussed separately:

●(See "Management of heparin-induced thrombocytopenia (HIT) during cardiac or vascular surgery".)

●(See "Blood management and anticoagulation for cardiopulmonary bypass", section on 'Heparin resistance'.)

●(See "Cardiac surgery with cardiopulmonary bypass in patients with cold agglutinin disease".)

Routine initiation and management of CPB, and weaning from CPB, are discussed in separate topics:

●(See "Initiation of cardiopulmonary bypass".)

●(See "Management of cardiopulmonary bypass".)

●(See "Weaning from cardiopulmonary bypass".)

Anesthetic management of CPB with a period of hypothermic circulatory arrest for surgical procedures that require temporary interruption of cerebral and systemic blood flow is discussed separately. (See "Anesthesia for aortic surgery with hypothermia and elective circulatory arrest in adult patients", section on 'Cardiopulmonary bypass with DHCA'.)

SURGICAL ISSUES

Previous median sternotomy — An increasing number of patients who had a previous operation performed through a median sternotomy require a repeat or "redo" sternotomy for cardiac surgical access. Common examples include the need for additional revascularization (ie, redo coronary artery bypass grafting [CABG] surgery), replacement of a previously implanted bioprosthetic valve due to structural degeneration, and transplant or circulatory assist device placement for end-stage heart disease previously treated with cardiac surgery.

Anatomic distortion and scarring from the previous sternotomy and cardiac operations add risk of injury to the heart, great vessels, or internal mammary and aorto-coronary grafts during re-entry into the mediastinum. Although surgical approaches attempt to avoid vascular injury, the surgery, anesthesiology, and perfusion teams must be prepared to manage the consequences immediately if such injury occurs. Perioperative planning and decision-making involving these teams includes:

●Developing a preoperative understanding of the individual patient's anatomy and risks for injury during sternal re-entry.

●Preparing for and implementing intraoperative strategies to avoid or mitigate vascular or myocardial injury.

●Readiness for immediate management of complications such as hemorrhage or myocardial ischemia and/or related arrhythmias during sternal re-entry, including emergency initiation of cardiopulmonary bypass (CPB).

Preoperative considerations — Certain aspects in the patient's history and findings noted on the chest radiograph and computed tomography (CT) scans are critically important for preoperative planning.

●Patient history – Details regarding the previous cardiac surgical procedure that are important to note include:

•For patients with previous CABG, the coronary vessels that were previously bypassed, particularly the anatomic location of patent grafts that are vulnerable to injury during sternal re-entry.

•For patients with a thoracic aortic graft or those who developed an aortic pseudoaneurysm, close proximity or adherence of any portion of the aorta and/or graft to the posterior surface of the sternum increases risk for rupture and exsanguination during sternal re-entry.

•For patients with previous open ablation for atrial fibrillation (eg, Maze procedure), difficulties with access via a mediastinal approach to the right atrium (RA), superior vena cava (SVC), or inferior vena cava (IVC) to accomplish venous cannulation should be anticipated.

●Chest radiograph and CT scanning – The relationship between the sternum and the ascending aorta, RA, or right ventricular (RV) free wall is noted on the preoperative chest radiograph lateral view (image 1). Scar adherence of these structures to the posterior table of the sternum may cause life-threatening hemorrhage if myocardial or vascular injury occurs during sternotomy. Many centers now obtain routine chest CT scans in patients undergoing redo sternotomy to assess specific anatomic risks for injury (image 2). CT angiography provides an even more detailed image of mediastinal cardiovascular anatomy and proximity of each structure to the back of the sternum. In addition, a CT scan provides important information regarding the location and patency of other vascular structures that may be considered to achieve vascular access (eg, internal jugular veins, innominate vein, or femoral veins). (See "Preoperative evaluation for anesthesia for cardiac surgery", section on 'Chest radiograph and computed tomography imaging'.)

The patency of coronary arterial grafts and their anatomic course within the mediastinum is assessed with preoperative coronary angiography. Notably, a patent left internal mammary to left anterior descending artery graft may be vulnerable to injury as it passes underneath the sternum.

●Planning the surgical procedure – An alternative procedure that does not involve redo sternotomy may be considered. Examples include a minimally invasive CABG or valve procedure accomplished via thoracotomy incision(s), or a percutaneous approach for transcatheter cardiac valve replacement or repair. (See "Off-pump and minimally invasive direct coronary artery bypass graft surgery: Clinical use" and "Anesthesia for percutaneous cardiac valve interventions" and "Minimally invasive aortic and mitral valve surgery".)

However, repeat sternotomy is necessary for many cardiac surgical operations that cannot be accomplished via alternative techniques. In some cases, decompression of the heart using initiation of CPB through peripherally accessed arterial (eg, right axillary artery) and venous (eg, femoral vein) vessels may facilitate safer redo sternotomy.

Intraoperative strategies — During preparations for sternotomy and initiation of CPB, strategies are employed by the anesthesiology, surgery, and perfusion teams to avoid or mitigate the potential for bleeding or myocardial ischemia due to injury or compression of the heart, great vessels, or coronary grafts.

●Anesthetic management strategies include:

•Applying transcutaneous defibrillator pads before surgical prepping and draping, and ensuring immediate availability (in the operating room) of an external defibrillator with pacing capability. Since it may not be possible for the surgeon to gain immediate direct access to the heart during redo sternotomy, these external defibrillator pads permit rapid treatment of ventricular tachycardia, ventricular fibrillation, or other hemodynamically unstable arrhythmias.

•Establishing intravenous (IV) access sufficient to treat rapid blood loss. When possible, IV access is on the patient's right side because injury to the left brachiocephalic vein during sternal re-entry will disrupt continuity of left-sided IV catheters to the central vasculature. Either left or right femoral venous access may be valuable if such injury occurs, although this should be discussed with the surgical team to determine if their plan is to use these femoral sites for cannulation in preparation for CPB.

•Ensuring immediate availability (in the operating room) of prechecked red blood cell (RBC) units, typically four units.

•Preparing vasopressor agents to treat hypotension and maintain hemodynamic stability until IV volume can be restored during massive hemorrhage. Inotropic agents are also prepared in case treatment of RV or left ventricular (LV) failure becomes necessary.

•Preparing a precalculated IV heparin dose appropriate for the individual patient in case emergency initiation of CPB is necessary.

•Planning use of intraoperative transesophageal echocardiography (TEE) to:

-Detect distension of the RV. Risk of injury to the RV or venous structures during sternal re-entry is increased when the RV (or RA) is distended, or if central venous pressure (CVP) is elevated.

-Detect RV or LV dysfunction as a consequence of myocardial ischemia, which can occur if previous coronary arterial grafts are injured during sternal sawing or compressed during surgical dissection to gain exposure to the heart and great vessels. Early detection of ischemia may prevent irreversible injury to coronary grafts and/or myocardium.

-Assist with placement of guidewires and cannulae during percutaneous arterial and venous cannulation if these are inserted before sternotomy for initiation of CPB, or to treat hemorrhage or myocardial ischemia.

-Visualize the presence of the arterial guidewire in the lumen of the descending thoracic aorta during percutaneous aortic cannulation (with verification that the wire is in the true lumen in patients with aortic dissection). Subsequently, a venous guidewire can be directed from the femoral vein through the intrahepatic IVC into the RA and then into the SVC during percutaneous femoral venous cannulation, while ensuring that placement in the atrial appendage or through a patent foramen ovale is avoided. The venous catheter that will be used during CPB is then imaged as it enters the RA through the IVC with its tip positioned near the superior caval-atrial junction.

●Surgical management strategies include:

•Using a sagittal oscillating saw for sternotomy, which allows the anterior and posterior tables of the sternum to be opened sequentially. This allows more control compared with use of a traditional saw, thereby reducing risk of injury to underlying vascular structures.

•Using an alternative approach to cannulation for CPB such as percutaneous cannulation of a peripheral artery (eg, femoral or right axillary artery) and percutaneous cannulation of a femoral vein. In some cases, small bore catheters are used to establish femoral arterial and venous access before the surgical incision such that exchange over guidewires for larger bore cannulation can facilitate rapid vascular access for initiation of emergent CPB.

The right femoral vein is typically accessed because it provides the most direct and straight route to the RA. This approach allows immediate initiation of CPB in case injury to the RA, RV, aorta, a previous coronary graft, or other vascular or myocardial structure occurs during sternotomy [1]. In patients with extreme risk for hemorrhage or myocardial injury, percutaneous cannulation, initiation of CPB, and patient cooling may be accomplished before attempting to enter the sternum. This strategy allows for chamber decompression to decrease risk of RV injury during sternal re-entry.

If the surgical procedure involves the aortic arch, then arterial cannulation of the right axillary artery (or via a graft anastomosed to this artery) is typically selected. This site also allows for innominate artery clamping and selective antegrade cerebral perfusion during episodes of deep hypothermia and elective circulatory arrest to maintain cerebral cooling. (See "Anesthesia for aortic surgery with hypothermia and elective circulatory arrest in adult patients".)

•Deliberate cooling with deep hypothermia and elective circulatory arrest to allow repair of an RV injury. (See "Anesthesia for aortic surgery with hypothermia and elective circulatory arrest in adult patients", section on 'Cooling strategies'.)

●Perfusion management strategies include:

•Priming the CPB circuit prior to skin incision.

•Preparing a precalculated IV heparin dose for direct administration into the CPB circuit upon emergency initiation of CPB (in addition to the systemic dose administered by the anesthesiologist).

•Ensuring immediate availability of arterial and venous cannulae for percutaneous cannulation to initiate CPB.

•Ensuring immediate availability of red blood cells (RBCs) to prime the CPB circuit in the event of massive hemorrhage.

•Preparing the CPB heater cooler unit in case immediate cooling or deep deliberate hypothermia becomes necessary.

•Preparing a blood salvage apparatus for salvaging shed blood.

Management of myocardial or vascular injury — Despite meticulous planning and preparation, injury to the RA, RV, a patent coronary graft, or entry into the aorta occasionally occurs during redo sternotomy, resulting in uncontrolled hemorrhage. Emergency management strategies may include:

●Adding crystalloid into the venous reservoir of the CPB circuit, as well as RBCs and Fresh Frozen Plasma (FFP) if hemorrhage is significant or ongoing. Transfusion through the venous or arterial cannula can be accomplished as soon as either or both cannulae have been inserted.

●Rapidly initiating CPB if bleeding cannot be immediately controlled or if myocardial injury or ischemia are severe. Once the decision is made to initiate CPB, systemic anticoagulation must be immediately established. We administer IV heparin (300 to 400 units/kg) directly into blood (assured by aspiration prior to and after injection) via a central venous catheter (CVC). Typically, additional heparin (usually 20,000 units) is administered directly into the CPB circuit since some of the heparin administered via the CVC may be lost into the mediastinum via wounds in the heart or great vessels. Arterial and venous cannulae are inserted, and CPB is rapidly established even if adequacy of anticoagulation has not yet been confirmed with an activated clotting time (ACT) test or point-of-care (POC) heparin-protamine titration assay (see "Blood management and anticoagulation for cardiopulmonary bypass", section on 'Heparin administration and monitoring'). Often, adequate flow on CPB can be temporarily maintained by collecting shed blood from the mediastinum via the cardiotomy suction into the venous reservoir of the CPB circuit (termed "sucker bypass") while venous cannulation is rapidly completed. Alternatively, any shed blood collected into the venous reservoir via the cardiotomy sucker can be processed using a cell saver device, then reinfused as needed.

●In rare circumstances, the aorta or cardiac structures cannot be easily repaired by initiating CPB, applying an aortic cross-clamp, and administering cardioplegia after initiating CPB. A strategy of cooling the patient to a deep hypothermic temperature (eg, 18°C) and establishing elective circulatory arrest is employed. Management of deep hypothermia and subsequent rewarming strategies, as well as consequences of using this technique are described separately. (See "Anesthesia for aortic surgery with hypothermia and elective circulatory arrest in adult patients".)

Aortic regurgitation — The presence and severity of aortic regurgitation (AR) is typically documented in the preoperative workup, and confirmed by intraoperative TEE examination during the prebypass period (movie 1 and image 3 and image 4 and image 5). (See "Clinical manifestations and diagnosis of chronic aortic regurgitation in adults", section on 'Diagnosis and evaluation' and "Acute aortic regurgitation in adults", section on 'Diagnosis'.)

Problems before and during CPB

Left ventricular distension — In patients with significant AR (image 6 and image 7), ventricular fibrillation will result in rapid LV distension because the LV is no longer ejecting the regurgitant volume. LV distension can lead to impairment of myocardial perfusion and consequent LV injury in addition to severe mitral regurgitation with severe, hydrostatic pulmonary edema.

Strategies to manage LV distension before CPB and after initiation of CPB until the aortic cross-clamp can be applied include:

●If ventricular fibrillation occurs, defibrillate immediately using internal paddles applied directly to the heart to deliver 10 to 20 joules of electricity. However, defibrillation is more likely to be successful if the heart is empty (nondistended).

●If ventricular distension is noted after CPB has been initiated, shut off or temporarily reduce CPB flow rate to allow the surgeon to decompress and empty the heart by manually massaging the LV, and then defibrillate the heart before resuming standard CPB flow. Subsequently, arterial flow is carefully adjusted to avoid acute increases in aortic pressure while providing adequate systemic perfusion with sufficient venous drainage. Hypotension is treated primarily by increasing CPB flow rather than by administering vasopressors. If a vasopressor is necessary to increase mean arterial pressure (MAP), small incremental doses are administered to avoid marked increases in aortic pressure.

●If ventricular arrhythmias occur prior to aortic cross-clamping, IV administration of antiarrhythmic agents such as lidocaine or amiodarone, epicardial pacing, or defibrillation or cardioversion may be necessary to maintain a stable cardiac rhythm, preserve ventricular ejection, and prevent LV distension.

●If severe bradycardia with LV distension is detected, rapidly establish CPB. Subsequently, if bradycardia develops during CPB (eg, during cooling) prior to aortic cross-clamping, administer a chronotropic agent (typically epinephrine) and/or use epicardial pacing to maintain a faster heart rate to minimize LV distension.

●If LV distension occurs despite these measures to control heart rhythm and rate, insert an LV vent to decompress this chamber. This is typically achieved by inserting a catheter into the LV via the right upper pulmonary vein before cooling begins. (See "Initiation of cardiopulmonary bypass", section on 'Left ventricular vent placement'.)

Detecting and guiding treatment of LV distension includes:

●TEE monitoring to:

•Detect LV distension using serial assessments of LV size, typically obtained using the transgastric short-axis view. Notably, in patients with baseline dilated cardiomyopathy, qualitative assessments to distinguish further LV dilation may be challenging.

•Note incomplete LV ejection during systole, and retrograde filling of the LV from the aorta during diastole.

•Note distension of the mitral annulus with mitral regurgitation occurring in both systole and diastole is an indication of severe LV dilation.

•Verify position of the LV vent after placement into the right upper pulmonary vein, across the mitral valve, and within the LV cavity but not against the LV apex (figure 1). If the vent tip is too close to the LV apex, a ventricular contraction could cause the LV vent cannula to rupture through the LV wall.

•Frequently assess the LV for distension since the LV vent cannula can become dislodged, obstructed, or unable to completely decompress the LV.

●Pulmonary artery catheter (PAC) monitoring to note increases in pulmonary artery pressure (PAP) as the LV dilates. A mean PAP ≥20 mmHg indicates LV distension. In some institutions, the same pressure transducer that is used to measure PAP is also used to monitor coronary sinus pressure during CPB. To ensure that increasing PAP is detected, the anesthesiologist can intermittently toggle the three-way stopcock on the pressure transducer between the PAP and coronary sinus pressure (image 8).

Provision of adequate cardioplegia

●Antegrade cardioplegia – Antegrade cardioplegia solution is typically administered into the aortic root after application of the ascending aortic cross-clamp (figure 1). However, if significant AR is present, the cardioplegia solution regurgitates retrograde into the LV cavity via the incompetent aortic valve rather than entering the coronary arteries. Typically, initial cardiac standstill may be achieved using brief antegrade cardioplegia solution delivery, then alternative strategies to effectively achieve cardioplegia delivery, provide adequate myocardial protection, and avoid LV distension are necessary, as described below. (See "Initiation of cardiopulmonary bypass", section on 'Aortic cross-clamping and antegrade cardioplegia administration'.)

●Retrograde cardioplegia – After brief initial administration of antegrade cardioplegia solution, intermittent low pressure retrograde cardioplegia is typically delivered. A balloon-tipped retrograde cardioplegia cannula is inserted through the wall of the RA with its tip positioned just within the opening of the coronary sinus. The final position of the retrograde cannula is confirmed with TEE using the midesophageal (ME) four-chamber view, with the TEE probe retroflexed until the coronary sinus comes into view (image 9). Alternatively, the TEE ME bicaval view can be used (obtained with slight probe rotation until the coronary sinus comes into view).

Coronary sinus pressure must be monitored and maintained <40 mmHg during delivery of retrograde cardioplegia to avoid myocardial edema. Ideally, the coronary sinus catheter is not inserted too far into the coronary sinus, so that venous branches from the right ventricle are not occluded by the catheter balloon and are adequately perfused with cardioplegia. (See "Initiation of cardiopulmonary bypass", section on 'Retrograde cardioplegia administration'.)

●Direct infusion of cardioplegia into left and right coronary ostia – An additional option often used to supplement antegrade and regrade cardioplegia, particularly when aortotomy is part of the surgical procedure (eg, aortic valve replacement), is direct delivery of cardioplegia solution into the left and right coronary ostia openings in the ascending aorta or aortic root.

Problems during weaning from CPB — Patients with clinically significant chronic AR (mild to moderate or ≥2+ severity) often have preexisting eccentric LV hypertrophy and reduced systolic function. Thus, inotropic agents are often necessary during weaning from CPB and the early postoperative period. Patients with acute AR who had no time to adapt to the sudden increase in LV volume may suffer rapid and severe LV distension with consequent LV injury. Such patients are even more likely to require inotropic support during weaning from CPB than those with chronic AR. (See "Weaning from cardiopulmonary bypass" and "Intraoperative problems after cardiopulmonary bypass", section on 'Left ventricular dysfunction'.)

MEDICAL ISSUES

Cerebrovascular disease

Preoperative management

●Identification of significant carotid stenosis – Significant carotid stenosis (ie, >80 percent) is present in 4 to 10 percent of patients undergoing coronary artery bypass grafting (CABG) surgery [2], and is a risk factor for perioperative stroke [3]. Some centers screen for carotid disease in all patients scheduled for CABG (eg, with carotid sonography), while others screen only those at high risk (age >65 years; left main coronary stenosis; peripheral arterial disease; history of transient ischemic attack or stroke, hypertension, tobacco use, or diabetes mellitus) [4-7]. However, traditional methods that identify large vessel cerebrovascular disease such as carotid Doppler may not identify patients at highest risk for stroke or other neurologic complications after cardiopulmonary bypass (CPB). One study noted that preoperative magnetic resonance imaging (MRI) identified large cerebral vessel disease in 25 percent of 346 patients scheduled for cardiac surgery, but small vessel disease was found in 35 percent [8].

Discussions regarding preoperative screening and medical management of patients with suspected or documented cerebrovascular disease before CABG surgery are found in a separate topic. (See "Coronary artery bypass grafting in patients with cerebrovascular disease", section on 'Risk factors' and "Coronary artery bypass grafting in patients with cerebrovascular disease", section on 'Screening for carotid disease'.)

●Preoperative decision-making and communication – Patients with a very high stroke risk may be scheduled for carotid endarterectomy (CEA) prior to or concurrently with their cardiac operation. Timing of revascularization (eg, combined carotid revascularization and CABG, staged carotid revascularization followed by CABG, or staged CABG prior to carotid revascularization) is determined preoperatively. If CEA is to be performed concomitantly with cardiac surgery, the central venous catheter (CVC) should be placed on the side contralateral to the carotid occlusion. Details regarding surgical treatment options for patients with known severe cerebrovascular disease are discussed separately. (See "Coronary artery bypass grafting in patients with cerebrovascular disease", section on 'Carotid treatment options'.)

Management before and during CPB — Management of most aspects of CPB including oxygenation, ventilation, pump flow, mixed venous oxygen saturation, maintenance of anticoagulation, anesthesia, and hemoglobin as well as control of blood glucose and electrolytes, does not differ from management for other patients undergoing cardiac surgical procedures. (See "Management of cardiopulmonary bypass".)

Particular attention is paid to the following aspects of CPB:

●Use of monitoring modalities – (See "Management of cardiopulmonary bypass", section on 'Monitoring'.)

•Transesophageal and/or epiaortic echocardiography guidance of surgical management – Since cerebrovascular disease is frequently associated with aortic atherosclerosis [9,10], transesophageal echocardiography (TEE) or epiaortic ultrasound imaging is typically used to guide selection of sites for aortic cannulation, cardioplegia administration, aortic cross-clamping, or placement of the "side-biter" clamp to complete proximal anastomoses during CABG (image 10). Avoiding surgical manipulation of aortic areas with known calcification or atherosclerotic plaque may reduce risk for cerebral embolism and postoperative stroke. (See "Anesthesia for cardiac surgery: General principles", section on 'Prebypass transesophageal echocardiography'.)

•Intraoperative neurophysiologic monitoring – Some centers routinely use one or more neuromonitoring modalities or reserve use for patients at high risk due to patient-related factors such as significant cerebrovascular disease. These may include cerebral oximetry monitoring using near-infrared spectrophotometry (NIRS), with planned interventions to treat decreases in regional oxygen saturation index (rSO₂) that are >20 percent below baseline (algorithm 1). In some centers, transcranial Doppler (TCD), electroencephalography (EEG), or somatosensory evoked potentials (SEP) are employed to detect cerebral embolism or imbalances in cerebral autoregulation. (See "Management of cardiopulmonary bypass", section on 'Neuromonitoring modalities'.)

●Cerebral protection

•Avoid hyperthermia – We avoid hyperthermia (body temperature >37°C) during and after CPB, since hyperthermia may increase risk or worsen severity of any brain injury sustained due to hypoperfusion or cerebral embolism in a patient with known cerebrovascular disease [11-13]. (See "Management of cardiopulmonary bypass", section on 'Temperature'.)

•Blood pressure management – Although mean arterial pressure (MAP) is generally targeted between 50 and 80 mmHg (or ≥65 mmHg) during CPB (table 1), a slightly higher MAP is often maintained in patients with known cerebrovascular disease [14-18]. However, data regarding the optimal target for MAP during CPB are inconsistent, probably due to interindividual differences in cerebral autoregulation among patients with or without known cerebrovascular disease [19]. Notably, cerebral autoregulation during CPB may be more impaired in patients with cerebral small vessel disease during CPB compared with those with large vessel disease [8]. (See "Management of cardiopulmonary bypass".)

•Use of pharmacologic agents – Although several pharmacologic agents that may have cerebroprotective properties have been studied (eg, antiinflammatory drugs, barbiturates, propofol, lidocaine), none were noted to be effective in reducing incidence or severity of postoperative stroke after cardiac surgery [20,21].

Chronic kidney disease and renal risk mitigation

Dialysis-dependent end-stage kidney disease — Patients with dialysis-dependent end-stage kidney disease (ESKD) typically undergo routine scheduled dialysis the day prior to elective scheduled cardiac surgery. For emergency surgery, or if additional fluid removal is needed, continuous ultrafiltration (CUF) with hemoconcentration can be accomplished during CPB. Zero-balance ultrafiltration can be used when toxin, electrolyte, or drug removal is necessary [22-28]. Additional information is available in separate topics. (See "Medical management of the dialysis patient undergoing surgery" and "Anesthesia for dialysis patients".)

Preexisting chronic kidney disease — Factors associated with increased risk for acute kidney injury (AKI) superimposed upon chronic kidney disease (CKD) after cardiac surgery with CPB include [29]:

●Patient-associated risk factors – High body mass index, advanced age, African American race, male sex, preexisting hypertension, active congestive heart failure, pulmonary disease, insulin-dependent diabetes mellitus, and peripheral vascular disease.

●Surgery-associated factors – Prolonged aortic cross-clamp duration (ie, complex surgery), generation of micro- and macroemboli, prolonged hypotension, low pump flow with inadequate oxygen delivery to the kidneys, and/or inflammatory or oxidative insult during CPB.

We agree with professional society recommendations to avoid or minimize AKI, particularly in patients with preexisting CKD [30]:

●Avoid hyperthermia – We avoid hyperthermia (body temperature >37°C) during and after CPB to avoid exacerbation of AKI and injury to other vital organs [31-33]. In a multicenter study with 8407 patients, duration of hyperthermic CPB rewarming (defined as pump oxygenator arterial outlet temperature >37°C) was directly associated with AKI risk (odds ratio [OR] 1.52, 95% CI 1.09-1.97) [33]. (See "Management of cardiopulmonary bypass", section on 'Temperature'.)

●Maintain oxygen delivery with adequate pump flow – Although pump flow rates between 2.2 and 2.4 L/minute/m² are adequate for most patients during CPB (table 1), some evidence suggests that higher flow rates provide optimal perfusion of the kidneys in some patients [34-39]. We monitor oxygen delivery to determine adequacy of CPB perfusion (table 2). In a randomized trial in 300 patients, the incidence of AKI was lower with use of pump flows that maintained estimated oxygen delivery index (DO₂i) at a high threshold index >300 mL/minute/m² (relative risk [RR] 0.48, 95% CI 0.30-0.77), compared with conventional pump flow rates that are not increased when hemoglobin levels decrease [40]. DO₂i estimates are estimates of real-time indexed oxygen delivery calculated using actual pump flow, hematocrit, and oxygen saturation. Retrospective studies have noted that risk of AKI increased in a stepwise fashion with increasing cumulative degree/duration of reduced oxygen delivery <300 mL/minute/m² [41]. Similarly, increased risk for AKI has been noted with exposure to DO₂i flow rates <270 mL/minute/m² lasting ≥30 minutes [42].

As a practical matter, pump flow rates on bypass are normally guided by providing the above noted standard flow rates based on body surface area (BSA), since DO₂i will not fall below the threshold index of 300 mL/minute/m² until the hemoglobin falls below 9 g/dL. However, at lower hemoglobin levels, calculation of DO₂i and adjustment of pump flow rates are appropriate measures to reduce risk of renal injury.

Other considerations include:

●Careful planning of vascular access – Patients with CKD may present additional challenges with vascular access due to existing or prior tunneled catheters and scarred cannulation sites. In patients with CKD who are not currently on dialysis but at risk for developing AKI, it may be wise to place large bore catheters that can be used for continuous renal replacement therapy (CRRT)/hemodialysis if needed in the immediate postoperative period.

●Ensure leukoreduction of red blood cells (RBCs) – Prestorage leukoreduction of RBCs, as is standard practice in the United States and Europe, was shown to reduce the incidence of worsening postoperative kidney function from 7.5 to 1.1 percent in a 2014 meta-analysis (OR 0.18, 95% CI 0.05-0.64; six trials; 374 cardiac surgical participants) [43]. (See "Intraoperative transfusion and administration of clotting factors", section on 'Use of filters'.)

●Avoid nephrotoxic fluids and drugs [44]:

•Avoid administration of hydroxyethyl starch solutions, which have been associated with AKI [29,45-47]. Also, risk of bleeding may be increased when hydroxyethyl starch is used in pump prime and/or intraoperative fluid therapy, compared with use of balanced salt solutions [47-49]. However, we do not consistently avoid administration of albumin-containing colloid, which may mitigate risk of hypoalbuminemia in this setting, which has been identified as a risk factor for AKI [50].

•Avoid administration of large volumes of normal saline, which may cause hyperchloremia that has been associated with increased mortality and risk of kidney injury after noncardiac surgery [29,51,52]. However, we do not avoid use of balanced salt solution such as lactated Ringer's, Normosol-R, or Plasma-Lyte A in the pump prime in patients with CKD or ESKD since the amount of potassium in these balanced salt solutions is unlikely to contribute to hyperkalemia.

•Avoid or minimize administration of potentially nephrotoxic pharmacologic agents. Examples include major classes of drugs that can contribute or worsen AKI such as aminoglycoside antibiotics, angiotensin-converting enzyme (ACE) inhibitors, and nonsteroidal antiinflammatory drugs (NSAIDs). Furthermore, we appropriately adjust dosing and timing for administration of drugs eliminated by the kidneys (eg, vancomycin, cephalosporins, tacrolimus, cyclosporin, gabapentin) when administration is necessary in patients CKD.

●Consider use of minimally invasive extracorporeal circulation (MiECC) – If equipment and expertise are available, use of technical interventions such as MiECC is reasonable in patients with CKD [30]. Such MiECC technology includes a miniaturized closed system circuit with reduced priming volume, a biologically inert circuit coating, a centrifugal pump, and a venous bubble trap and air removal device.

●Other management considerations – Hemofiltration strategies such as CUF are sometimes used to manage fluid overload in patients with CKD. In support of CUF, a 2006 meta-analysis noted reduction in transfusion [53], and subsequently published small randomized trials indicate that CUF effectively increases hematocrit [53-56]. However, we try to avoid high-volume CUF (>35 mL/kg) to treat anemia as this has been associated with AKI after cardiac surgery [57,58].

Administration of a dopamine infusion or the diuretic mannitol is not recommended to reduce risk of AKI, as studies have demonstrated lack of efficacy of these agents for renoprotection [30]. However, some centers administer the dopamine receptor D1 agonist fenoldopam because of limited evidence supporting its use to reduce the incidence of AKI, although data are inconsistent [30]. Importantly, since fenoldopam is a vasodilator, it is critically important to avoid hypotension during its administration. Although other pharmacologic agents that may reduce inflammation or ischemia-reperfusion injury have been studied (eg, steroids, statins, cyclosporine), none were noted to be effective in reducing incidence or severity of postoperative AKI [18,43,45,59-62].

Importantly, for patients with moderately to severely reduced kidney function, we select epsilon-aminocaproic acid for antifibrinolytic prophylaxis during CPB, or we administer lower doses when tranexamic acid is used due to increased seizure risk associated with use of tranexamic acid in patients with moderately to severely reduced kidney function [63]. (See "Blood management and anticoagulation for cardiopulmonary bypass", section on 'Antifibrinolytic administration'.)

Management of other aspects of CPB does not differ from management for other patients undergoing cardiac surgical procedures (eg, maintenance of oxygenation, ventilation, pump flow, mixed venous oxygen saturation, anticoagulation, control of blood glucose and electrolytes, and management of anemia and transfusion therapy) [30]. Notably, anemia with hemoglobin ≤7.5 g/dL (or hematocrit ≤22 percent) has been associated with AKI after cardiac surgery [29,64-70], but transfusion of RBCs to avoid or treat anemia has also been associated with AKI [67,70,71] (see "Management of cardiopulmonary bypass"). Although some management guidelines specifically addressing AKI prevention in cardiac surgery are available (eg, KDIGO), so far these have not been widely adopted, nor is the evidence compelling that AKI reduction is achieved with their use [72].

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Management of cardiopulmonary bypass".)

SUMMARY AND RECOMMENDATIONS

●Previous sternotomy – Anatomic pathology and scarring increase risk for injury to the heart or great vessels. Risk management includes (see 'Previous median sternotomy' above):

•Understanding the patient's anatomy and risks for injury

•Implementing strategies to avoid injury

•Readiness for immediate management of complications (hemorrhage, myocardial ischemia), including emergency initiation of cardiopulmonary bypass (CPB)

●Aortic regurgitation – Aortic regurgitation may cause left ventricular (LV) distension and/or limit effective delivery of antegrade cardioplegia during CPB. Continuous monitoring of transesophageal echocardiography (TEE) views and pulmonary artery pressure can detect LV distension. Surgical technical modifications may include insertion of a vent to decompress the LV, or delivery of cardioplegia via a retrograde approach into the coronary sinus, or directly into the coronary ostia. Inotropic support of the LV is typically necessary during weaning from CPB. (See 'Aortic regurgitation' above.)

●Cerebrovascular disease – Considerations for patients with known cerebrovascular disease include avoiding hyperthermia >37°C, maintaining a slightly higher mean arterial pressure (MAP), and considering use of epiaortic or TEE to guide insertion of the aortic cannula since cerebrovascular disease is frequently associated with aortic atherosclerosis. (See 'Cerebrovascular disease' above and "Coronary artery bypass grafting in patients with cerebrovascular disease".)

●Chronic kidney disease

•Preexisting chronic kidney disease – Considerations include (see 'Preexisting chronic kidney disease' above):

-Avoid hyperthermia >37°C

-We suggest maintaining the oxygen delivery index (DO₂i) at a high threshold index >300 mL/minute/m² to ensure optimal renal perfusion (Grade 2C)

-Avoid nephrotoxic fluids and drugs

•Patients on dialysis – Patients typically undergo routine scheduled dialysis before elective cardiac surgery. For emergency surgery or if additional fluid removal is needed, hemoconcentration by continuous ultrafiltration (CUF) may be performed during CPB, or zero-balance ultrafiltration may be employed for removal of toxins or drugs. (See 'Dialysis-dependent end-stage kidney disease' above.)