Flow diagram detailing pre-transplant cardiac workup in renal recipients
All renal recipients must have a preoperative ECG during their workup. Abnormal results warrant additional cardiac evaluation. The type of noninvasive cardiac testing (dobutamine stress echocardiography versus myocardial perfusion scintigraphy) is left at the discretion of the perioperative evaluator. There is no evidence for or against surveillance by repeated periodic left ventricular function testing after listing for kidney transplantation as concluded in the 2012 ACC/AHA/AST/AKF consensus report .
Echocardiography must be obtained in those with suspected valvular disease or congestive heart failure . More frequent echocardiographic monitoring is also recommended in ESRD patients with moderate aortic stenosis as suggested by Lentine et al. since they usually are “rapid progressors.” Patients who show signs of significant pulmonary hypertension during echocardiography require cardiac catheterization. If right-heart catheterization confirms the presence of significant pulmonary arterial hypertension in the absence of an identified secondary cause (e.g., obstructive sleep apnea, left heart disease), referral to a consultant with expertise in pulmonary arterial hypertension management and advanced vasodilator therapies is recommended.
Coronary artery bypass graft (CABG) to improve survival and/or to relieve angina despite optimal medical therapy may be reasonable for patients with ESRD with significant (>50 %) left main stenosis or significant (≥70 %) stenosis in three major vessels or in the proximal left anterior descending artery plus one other major vessel, regardless of left ventricular systolic function. CABG is recommended in preference to PCI to improve survival in patients with multivessel CAD and diabetes mellitus .
NPO (Nothing per Mouth) Guidelines and Preoperative Medications
All patients receiving an elective surgery must abstain from solids or foods by mouth for at least 6 h prior to surgery. Diabetics or those with other medical conditions that impair gastric emptying should have at least 8-h NPO time. Gastric emptying largely depends on vagus nerve function, which can be severely disrupted in patients with DM. The major clinical features of diabetic gastroparesis are early satiety, anorexia, nausea, vomiting, epigastric discomfort, and bloating .
Patients should take their scheduled medications with a sip of water or clear juice. In general, the patients should take all of the scheduled medications with the exception of angiotensin system inhibitors and oral hypoglycemic drugs. Angiotensin inhibitors administered immediately before surgery have been associated with a higher incidence of hypotension on induction of general anesthesia . Oral hypoglycemic drugs are withheld on the day of surgery for drugs with a short half-life and up to 48 h preoperatively for long-acting drugs such as chlorpropamide. This is done to avoid reactive hypoglycemia, particularly with sulfonylurea compounds, and associated drug-induced toxicities and interactions .
Among patients already taking beta-adrenergic blockers before renal transplantation, continuing these drugs perioperatively is recommended to prevent rebound hypertension and tachycardia. Initiating beta-blocker therapy in beta-blocker-naïve patients the night before and/or the morning of noncardiac surgery is not recommended .
Hypertension and Diabetes Mellitus
Patients with CKD have a high prevalence of hypertension and/or diabetes mellitus. Hypertension has been reported to occur in 85–95 % of patients with CKD . Hypertension can be a cause or a consequence of CKD. Approximately one of three adults with diabetes has CKD per 2014 National Chronic Kidney Disease Fact Sheet .
In type 2 diabetic patients, modest blood pressure control may be more important than chronic glycemic control . Current recommendations are to target a blood pressure of <130/80 mmHg in hypertensive diabetics. In all diabetics with ESRD, the type of diabetic disease (type 1 or type 2), method of home monitoring, and usual metabolic control must be studied. It is important to know antidiabetic therapy, such as diet, anti-hyperglycemic agents, or insulin therapy. Serum glucose levels and the glycosylated HbA1c test are useful in evaluating the efficacy of therapeutic control of the diabetic state. HbA1c is not affected by short-term changes in blood glucose levels but, instead, reflects long-term changes in blood glucose levels. Elevated HbA1c is predictive of the presence of microvascular and macrovascular complications associated with DM .
The chronic effects of DM can be divided into microvascular (including diabetic retinopathy and nephropathy), neuropathic (autonomic and peripheral), and macrovascular complications (atherosclerotic disease). Perioperative cardiovascular morbidity and mortality are increased two- to threefold in patients with diabetes .
There are several items of concern to the anesthesiologist taking care of kidney transplant recipients. Diabetic patients have a list of comorbidities along with their ESRD. These comorbidities will influence anesthetic approach because of gastroparesis, autonomic neuropathy, peripheral neuropathy, cardiovascular disease, and peripheral vascular disease . The major clinical manifestations of diabetic autonomic neuropathy include resting tachycardia, exercise intolerance, orthostatic hypotension, constipation, gastroparesis, pseudo-motor dysfunction, impaired neurovascular function, and hypoglycemic autonomic failure. Determination of the presence of diabetic autonomic neuropathy is based on a battery of autonomic function tests. These include R–R interval variation in the ECG, Valsalva maneuver effects, and postural blood pressure tests to help define the presence of cardiovascular autonomic dysfunction.
Fluid Status and Electrolytes
The immediate preoperative assessment includes identification of disturbances in acid–base balance and electrolytes, as well as an estimation of fluid status, which can range from severe hypovolemic to pronounced hypervolemia in patients undergoing renal transplant surgery. The patient’s volume status can be estimated by the frequency of dialysis and when it was last performed. Although further studies are needed, the routine use of hemodialysis immediately prior to surgery cannot be recommended, but should be considered in patients with high serum potassium levels which may be accentuated during graft reperfusion when a significant amount of potassium is released [17, 18].
Most patients have a dialysis shunt in place, which requires special care during positioning for surgery. Its cannulation is reserved for absolute emergencies such as when resuscitation is required but no other vascular access is available. Metabolic acidosis is a common problem in patients with end-stage renal disease. Careful correction of acidosis during surgery is recommended for two reasons. First, adjustment of acid–base balance with bicarbonate helps to reduce the commonly elevated levels of serum potassium. Second, the function of the transplanted kidney is supported, particularly in terms of maintaining a balanced acid–base state . Other CKD-related comorbid conditions include hypocalcemia, hypophosphatemia, and hyperparathyroidism .
There is an increased prevalence of several prothrombotic factors in renal transplant candidates, and thrombophilic patients are at a higher risk for early graft loss. All transplant candidates should have routine coagulation studies performed. Patients who have had a history of thrombosis, including recurrent thrombosis of arteriovenous grafts and fistulas, should have a more extensive coagulation profile performed. This should include screening for activated protein C (APC) resistance, factor V and prothrombin gene mutations, anticardiolipin antibody, lupus anticoagulant, proteins C and S, antithrombin III, and homocystine levels. About 6 % of Caucasians have APC resistance, usually as a result of heterozygosity for the factor V Leiden mutation. They are prone to thrombotic complications and graft loss. All renal transplant candidates with systemic lupus erythematosus should have antiphospholipid antibodies measured. This helps to define the severity of the disease.
Thrombophilia is rarely a contraindication to transplantation, although its recognition should initiate preventive strategies. Therapeutic decisions for long-term anticoagulation need to be individualized with respect to the agent used and the length of treatment. Chronic anticoagulation of dialysis patients with recurrent access thrombosis but without an underlying coagulopathy is often ineffective and should be avoided. Long-standing warfarin administration has been associated with accelerated vascular calcification.