Reduced Functional Measure of Cardiovascular Reserve Predicts Admission to Critical Care Unit following Kidney Transplantation

Abstract

BackgroundThere is currently no effective preoperative assessment for patients undergoing kidney transplantation that is able to identify those at high perioperative risk requiring admission to critical care unit (CCU). We sought to determine if functional measures of cardiovascular reserve, in particular the anaerobic threshold (VO2AT) could identify these patients.MethodsAdult patients were assessed within 4 weeks prior to kidney transplantation in a University hospital with a 37-bed CCU, between April 2010 and June 2012. Cardiopulmonary exercise testing (CPET), echocardiography and arterial applanation tonometry were performed.ResultsThere were 70 participants (age 41.7±14.5 years, 60% male, 91.4% living donor kidney recipients, 23.4% were desensitized). 14 patients (20%) required escalation of care from the ward to CCU following transplantation. Reduced anaerobic threshold (VO2AT) was the most significant predictor, independently (OR = 0.43; 95% CI 0.27–0.68; p<0.001) and in the multivariate logistic regression analysis (adjusted OR = 0.26; 95% CI 0.12–0.59; p = 0.001). The area under the receiver-operating-characteristic curve was 0.93, based on a risk prediction model that incorporated VO2AT, body mass index and desensitization status. Neither echocardiographic nor measures of aortic compliance were significantly associated with CCU admission.ConclusionsTo our knowledge, this is the first prospective observational study to demonstrate the usefulness of CPET as a preoperative risk stratification tool for patients undergoing kidney transplantation. The study suggests that VO2AT has the potential to predict perioperative morbidity in kidney transplant recipients.

Pre-operative Functional Cardiovascular Reserve Is Associated with Acute Kidney Injury after Intervention

“…A study involving 10,518 patients undergoing surgery suggested that long-term survival was worse those with AKI, even after complete eGFR recovery (43). We have previously shown a strong association between AKI after endovascular intervention, vascular surgery, renal transplantation or coronary angiography and subsequent short and longterm cardiovascular events and all-cause morbidity, in multiple cohort studies as well as a metaanalysis (4,26,28,29). A recent review from NICE suggests that AKI has a major impact on safety and healthcare-cost (44); a patient with AKI after intervention spends an average of 4.7 extra nights hospitalised with an additional £3,691 for medical-treatment (5,44).…”

“…The corresponding AT was derived using the V-slope method (35). An AT level of 11 ml/min/kg has traditionally been used as a threshold of sufficient CVR in various surgical and other clinical settings (27,29,36). Patients with an AT<11 ml/min/kg are not offered open surgical AAA repair in the institutions involved but will be considered for EVAR.…”

“…The latter (CPET) is now being used frequently prior to major surgery (20)(21)(22)(23)(24). It provides an accurate estimate of CVR by measuring AT, a validated objective and reproducible marker of CVR, independent patient effort (25)(26)(27)(28)(29).…”

Functional Cardiovascular Reserve Predicts Survival Pre-Kidney and Post-Kidney Transplantation

“…On the contrary, quantification of cardiovascular reserve through graded exercise has been shown to be powerful given its unique ability to predict the capacity to survive pathologic stresses in various chronic conditions such as heart failure and chronic lung disease 4,[7][8][9] as well as in perioperative demands of major surgeries. [10][11][12] During exercise, alveolar oxygen uptake (VO 2 ) provides the arterial oxygen for delivery to contracting muscles reflecting the coupling of pulmonary gas exchange to cellular respiration by the circulation. 13 Above a certain work rate, exercise sustainability through the aerobic regeneration of ATP is supplemented by anaerobic glycolysis resulting in production of lactic acid.…”

Screening for cardiovascular disease before kidney transplantation

“…Failure to achieve the target heart rate impairs the capture of sufficient diagnostic information [29] , and ambiguity in correlating ECG findings to territorial ischemia will lead to a decision to pursue additional forms of stress testing in most cases. Testing for functional cardiovascular reserve [30,31] instead may be superior for prognostication although these tests have not been widely adapted. Nonetheless, exercise stress testing is reasonable to pursue in young, otherwise apparently healthy transplant candidates by serving as a positive reinforcement to them.…”