Renal dysfunction after cardiac surgery with normothermic cardiopulmonary bypass: incidence, risk factors, and effect on clinical outcome

Cardiopulmonary Bypass Blood Flow Rates and Major Adverse Kidney Events in Cardiac Surgery: A Propensity Score-adjusted Before-After Study

OBJECTIVES

Cardiac surgery associated-acute kidney injury is a common and serious postoperative complication of cardiac surgery, which is associated with increased postoperative morbidity and mortality. This study aimed to explore the association between cardiopulmonary bypass (CPB) blood flow rate (BFR), and major adverse kidney events (MAKEs) at day 30.

DESIGN

Retrospective single-center before-after observational study. Patients were divided in 2 groups according to CPB flow rates: a first group with an institutional protocol targeting a CPB-BFR of >2.2 L/min/m² (low CPB-BFR group), and a second group with a modified institutional protocol targeting a CPB-BFR of >2.4 L/min/m² (high CPB-BFR group). The primary outcome was MAKE at 30 days, defined as the composite of death, renal replacement therapy or persistent renal dysfunction.

SETTING

The data were collected from clinical routines in university hospital.

PARTICIPANTS

Adult patients who underwent elective and urgent cardiac surgery without severe chronic renal failure, for whom CPB duration was ≥90 minutes.

INTERVENTIONS

We included 533 patients (low CPB-BFR group, n = 270; high CPB-BFR group, n = 263).

MEASUREMENTS AND MAIN RESULTS

A significant decrease in MAKE at 30 days was observed in the high CPB-BFR group (3% v 8%; odds ratio [OR], 0.779; 95% confidence interval [CI], 0.661-0.919; p < 0.001) mainly mediated by a lower 30-day mortality in the high CPB-BFR group (1% v 5%; OR, 0.697; 95% CI, 0.595-0.817; p = 0.001), as was renal replacement therapy (1% v 4%; OR, 0.739; 95% CI, 0.604-0.904; p = 0.016).

CONCLUSIONS

In patients undergoing cardiac surgery, increased CPB-BFR was associated with a decrease in MAKE at 30 days including mortality and renal replacement therapy.

Frequency of Renal Dysfunction and its effects on outcomes after open heart surgery

Objectives:

In this study we determined the frequency of renal dysfunction and its outcomes in terms of morbidity and mortality in patients who underwent open heart surgery at the Aga Khan University Hospital, Karachi, Pakistan.

Methods:

A total of 175 patients aged between 15-80 years having open heart Surgery(OHS) were included. Preoperative and postoperative serum creatinine (SCr) was noted and the glomerular filtration rate (GFR) calculated by Cockcroft-Gault equation. Their hospital course was charted and followed-up for 30-day.

Results:

The mean age and mean BMI were 58.1±12.6 years and 26.4±4.3 kg/m2 respectively. Females were 18.3%, out of which 51.4% hypertensive, 46.9% diabetics, 45.1% had dyslipidemia, 2.9% had preoperative renal dysfunction and 40% had moderate ejection fraction. On follow up, 30.3% developed postoperative renal dysfunction within 30-days after OHS with mean SCr and GFR as 1.6±0.7 and 56.9±24.5, respectively. In RD group more patients showed positive outcomes i.e. prolonged inotropic requirement (75.5% vs. 18%, p-value <0.005), diuretic infusion usage (47.2% vs. 3.3%, p-value <0.005), dialysis/renal replacement therapy (17% vs. 0%, p-value <0.005), requirement for prolonged ventilation (35.8% vs. 6.6%, p-value <0.005), prolonged ICU and hospital stay (15.4% vs. 1.6%, p-value <0.005 and 41.5% vs. 17.2%, p-value <0.005), sepsis (20.8% vs. 1.6%, p-value <0.005) and death (9.4% vs. 2.5%, p-value 0.05).

Conclusion:

Timely recognition of renal dysfunction, early renal replacement therapy, diuretics or dialysis and proper nutritional and inotropic support to maintain adequate hemostasis shows survival benefits.

Evaluation of acute kidney injury with oxidative stress biomarkers and Renal Resistive Index after cardiac surgery

BACKGROUND

We investigated whether cardiopulmonary bypass (CPB) related oxidative stress mediated glycocalyx degradation can cause an increase in renal resistive index (RRI) or postoperative AKI. Additionally, to evaluate whether RRI and early postoperative serum cystatin C levels could improve the prediction sensitivity of acute kidney injury (AKI).

METHODS

Forty-two patients undergoing cardiac surgery were included in this prospective observational study. RRI was measured pre-operatively and in the cardiac intensive care unit. Blood samples were collected for analyzing of cellular injury biomarkers at preoperative and postoperative second hours. We determined areas under the receiver operating characteristic curve (AUC) and odds ratios for postoperative biomarkers and RRI to predict AKI.

RESULTS

While postoperative cystatin C level (AUC: 0.902, 95% CI = 0.79-1.00, p < .001) and RRI (AUC: 0.748, 95% CI = 0.56-0.93, p = .023) have diagnostic and predictive value in the prediction of AKI, we could not identify any relation between products of oxidative stress and the glycocalyx degradation and AKI.

CONCLUSION

These data suggest that CPB leads to structural and oxidative changes at the protein level and the integrity of glycocalyx is disturbing, but these changes are not specific to kidney injury. Our data suggest that serum cystatin C level and RRI could be used as an early biomarker for postoperative AKI after cardiac surgery.

Intraoperative hyperglycemia in patients with an elevated preoperative C-reactive protein level may increase the risk of acute kidney injury after cardiac surgery

PURPOSE

The effect of hyperglycemia on acute kidney injury (AKI) in patients undergoing cardiac surgery is unclear and may involve as yet unexplored factors. We hypothesized differential effects of intraoperative hyperglycemia on AKI after cardiac surgery depending on baseline inflammatory status, as reflected by the C-reactive protein (CRP) level.

METHODS

This retrospective study included patients who underwent cardiac surgery seen at our hospital from 2008 to 2018. Patients were classified into four groups according to their preoperative CRP level (≥ 1 or < 1 mg/dl) and their intraoperative time-weighted average glucose concentration (> 140 or ≤ 140 mg/dl): low CRP and normoglycemia, low CRP and hyperglycemia, high CRP and normoglycemia, and high CRP and hyperglycemia. The data were analyzed by multivariable logistic regression analysis.

RESULTS

The data of 3625 patients were analyzed. The logistic regression showed that patients in the high CRP and hyperglycemia group had a significantly higher risk of AKI than patients in the low CRP and normoglycemia group [odds ratio (OR), 1.58; 95% confidence interval (CI) 1.10-2.27], low CRP with hyperglycemia group (OR, 1.69; 95% CI 1.16-2.47) and high CRP with normoglycemia group (OR, 1.50; 95% CI 1.01-2.23).

CONCLUSIONS

Intraoperative hyperglycemia in patients with an elevated preoperative CRP level was significantly related to an increased risk of AKI after cardiac surgery. Individualized perioperative glycemic control may therefore be necessary in these patients.

A Better Predictor of Acute Kidney Injury After Cardiac Surgery: The Largest Area Under the Curve Below the Oxygen Delivery Threshold During Cardiopulmonary Bypass

Background

The aim of this study was to compare the predictive accuracy of acute kidney injury (AKI) after cardiac surgery using cardiopulmonary bypass for the largest area under the curve (AUC) below the oxygen delivery (DO₂) threshold and the cumulative AUC below the DO₂ threshold.

Methods and Results

From March 2017 to October 2019, 202 patients who had undergone cardiac surgery with cardiopulmonary bypass were enrolled. The perfusion parameters were recorded every 20 seconds, and the DO₂ (10×pump flow index [L/min per m²]×[hemoglobin (g/dL)×1.36×arterial oxygen saturation (%)+partial pressure of arterial oxygen (mm Hg)×0.003]) threshold of 300 mL/min per m² was considered to define sufficient DO₂. The nadir DO₂, the cumulative AUC below the DO2300, and the largest AUC below the DO2300 were used to predict the incidence of AKI. Postoperative AKI was observed in 12.4% of patients (25/202). By multivariable analysis, the largest AUC below the DO2300 ≥880 (odds ratio [OR], 4.9; 95% CI, 1.2–21.5 [P=0.022]), preoperative hemoglobin concentration ≤11.6 g/dL (OR, 7.6; 95% CI, 2.0–32.3 [P=0.004]), and red blood cell transfusions during cardiopulmonary bypass ≥2 U (OR, 3.3; 95% CI, 1.0–11.1 [P=0.041]) were detected as independent risk factors for AKI. Receiver operating curve analysis revealed that the largest AUC below the DO2300 was more accurate to predict postoperative AKI compared with the nadir DO₂ and the cumulative AUC below the DO2300 (differences between areas, 0.0691 [P=0.006] and 0.0395 [P=0.001]).

Conclusions

These data suggest that a high AUC below the DO2300 is an important independent risk factor for AKI after cardiopulmonary bypass, which could be considered for risk prediction models of AKI.

Sarcopenia assessed by the quantity and quality of skeletal muscle is a prognostic factor for patients undergoing cardiac surgery

PURPOSE

Sarcopenia was assessed as a prognostic factor for patients undergoing cardiac surgery by evaluating the quantity and quality of skeletal muscle.

METHODS

Sarcopenia was assessed by perioperative abdominal computed tomography using the total psoas muscle index (TPI) and intra-muscular adipose tissue content (IMAC). Patients were classified into high- (HT, n = 143) and low- (LT, n = 63) TPI groups and low- (LI, n = 122) and high- (HI, n = 84) IMAC groups.

RESULTS

There were significantly more complications in the LT and HI groups than in the HT and LI groups. (HT 15.4% vs. LT 30.2%, P = 0.014) (LI 11.5% vs. HI 31.1%, P < 0.001). There were more respiratory complications in the LT group (HT 0% vs. LT 6.3%, P = 0.002) and more surgical site infections in the HI group than in the LI group (LI 0.8% vs. HI 7.1%, P = 0.014). A multivariable analysis showed that low TPI and high IMAC significantly predicted more major complications than other combinations (odds ratio [OR] 2.375; 95% confidence interval [CI] 1.152-5.783; P = 0.036, OR 3.973; 95% CI 1.737-9.088; P = 0.001).

CONCLUSIONS

Sarcopenia is a risk factor for complications. The quantity and quality of muscle must be assessed to predict operative outcomes.

CLINICAL TRIAL REGISTRATION NUMBER

UMIN000027077.

Morbidity After cardiac surgery under cardiopulmonary bypass and associated factors: A retrospective observational study

Background

The present study aimed to assess the morbidity after cardiac surgery and identify the preoperative and intraoperative factors associated with postoperative morbidity.

Methods

A retrospective observational study was conducted including 362 adult patients aged 18–75 years who underwent open-heart surgery under cardiopulmonary bypass at Sri Jayadeva Institute of Cardiovascular Sciences and Research, Bengaluru, India, during the period from June 2016 to May 2017. Using a structured schedule, preoperative and intraoperative data were collected from the hospital's cardiac surgery database, whereas the postoperative data were collected from the intensive care unit (ICU) database and the hospital's clinical information system database.

Results

Of 362 patients, 254 (70.2%) had at least one major complication, and the most frequently occurring complication was low cardiac output state (29.8%). The ICU length of stay (LOS) was for > 2 days in 23.2% of patients, and the hospital LOS was for > 7 days in almost 60% of the patients. Multivariate logistic regression analyses revealed that gender, type of surgery, body weight, blood lactate level at ICU admission, and 12-h blood lactate level were significant predictors of complications; gender and 24-h blood lactate level were significantly associated with the prolonged ICU LOS, whereas type of surgery and 24-h blood lactate level were significantly associated with prolonged hospital LOS.

Conclusion

The appropriate patient management strategy can be tailored based on the personal attributes, surgery type, and blood lactate level for individual patients undergoing cardiac surgery to reduce the likelihood of postoperative complications, ICU LOS, and hospital LOS.

Comparison of Causal and Non-causal Strategies for the Assessment of Baroreflex Sensitivity in Predicting Acute Kidney Dysfunction After Coronary Artery Bypass Grafting

Coronary artery bypass graft (CABG) surgery may lead to postoperative complications such as the acute kidney dysfunction (AKD), identified as any post-intervention increase of serum creatinine level. Cardiovascular control reflexes like the baroreflex can play a role in the AKD development. The aim of this study is to test whether baroreflex sensitivity (BRS) estimates derived from non-causal and causal approaches applied to spontaneous systolic arterial pressure (SAP) and heart period (HP) fluctuations can help in identifying subjects at risk of developing AKD after CABG and which BRS estimates provide the best performance. Electrocardiogram and invasive arterial pressure were acquired from 129 subjects (67 ± 10 years, 112 males) before (PRE) and after (POST) general anesthesia induction with propofol and remifentanil. Subjects were divided into AKDs (n = 29) or no AKDs (noAKDs, n = 100) according to the AKD development after CABG. The non-causal approach assesses the transfer function from the HP-SAP cross-spectrum in the low frequency (LF, 0.04–0.15 Hz) band. BRS was estimated according to three strategies: (i) sampling of the transfer function gain at the maximum of the HP-SAP squared coherence in the LF band; (ii) averaging of the transfer function gain in the LF band; (iii) sampling of the transfer function gain at the weighted central frequency of the spectral components of the SAP series dropping in the LF band. The causal approach separated the two arms of cardiovascular control (i.e., from SAP to HP and vice versa) and accounted for the confounding influences of respiration via system identification and modeling techniques. The causal approach provided a direct estimate of the gain from SAP to HP by observing the HP response to a simulated SAP rise from the identified model structure. Results show that BRS was significantly lower in AKDs than noAKDs during POST regardless of the strategy adopted for its computation. Moreover, all the BRS estimates during POST remained associated with AKD even after correction for demographic and clinical factors. Non-causal and causal BRS estimates exhibited similar performances. Baroreflex impairment is associated with post-CABG AKD and both non-causal and causal methods can be exploited to improve risk stratification of AKD after CABG.

Impact of occult renal disease on the outcomes of off-pump and on-pump coronary artery bypass grafting

Purpose

Occult renal disease (ORD) is a clinical condition in which glomerular filtration rate (GFR) is less than 60 ml/min/1.73 m², while serum creatinine is ≤ 1.3 mg/dl. The aim of the study was to compare the incidence of postoperative stage I acute kidney injury (AKI) according to Acute Kidney Injury Network (AKIN) classification in patients with ORD undergoing either off-pump or on-pump coronary artery bypass grafting.

Methods

A single center prospective randomized study was conducted from March 2011 through January 2014. A total of 120 coronary artery disease (CAD) patients with ORD undergoing coronary artery bypass grafting (CABG) were randomized to either off-pump (group1, n = 62) or on-pump (group2, n = 58) CABG in 1:1 ratio by computer-generated random number table. The GFR and serum creatinine levels were measured preoperatively and postoperatively on day 1 and day 5. The primary outcome (postoperative AKI (stage I)) and secondary outcomes (AKI (stage III) requiring renal replacement therapy (RRT) death, myocardial infarction (MI), cerebrovascular accident, atrial fibrillation (AF), and re-exploration for bleeding) at 30 days were analyzed between the groups.

Results

There is no significant difference in baseline characteristics of patients between off-pump and on-pump group. The incidence of postoperative AKI (stage I) was similar between on-pump (20.69%) and off-pump (16.13%) groups (p = 0.51). There was no significant difference in mortality (p = 0.33), postoperative MI (p = 0.34), cerebrovascular accident (p = 1.00), re-exploration (p = 0.96), and AF (p = 0.50). The number of patients of stage III AKI requiring RRT was higher in the off-pump group (3 patients, 4.8%) and none in the on-pump group (p = 0.08).

Conclusions

This study demonstrated that on-pump CABG is associated with significantly lower GFR and significantly higher serum creatinine on postoperative day 1 which return to baseline by postoperative day 5. In patients with ORD undergoing CABG, the incidence of postoperative AKI and major adverse cardiac and cerebrovascular events were similar between off-pump or on-pump CABG patients.

Vitamin C to Improve Organ Dysfunction in Cardiac Surgery Patients-Review and Pragmatic Approach

The pleiotropic biochemical and antioxidant functions of vitamin C have sparked recent interest in its application in intensive care. Vitamin C protects important organ systems (cardiovascular, neurologic and renal systems) during inflammation and oxidative stress. It also influences coagulation and inflammation; its application might prevent organ damage. The current evidence of vitamin C's effect on pathophysiological reactions during various acute stress events (such as sepsis, shock, trauma, burn and ischemia-reperfusion injury) questions whether the application of vitamin C might be especially beneficial for cardiac surgery patients who are routinely exposed to ischemia/reperfusion and subsequent inflammation, systematically affecting different organ systems. This review covers current knowledge about the role of vitamin C in cardiac surgery patients with focus on its influence on organ dysfunctions. The relationships between vitamin C and clinical health outcomes are reviewed with special emphasis on its application in cardiac surgery. Additionally, this review pragmatically discusses evidence on the administration of vitamin C in every day clinical practice, tackling the issues of safety, monitoring, dosage, and appropriate application strategy.

Prevention of Cardiac Surgery-Associated Acute Kidney Injury

Numerous strategies have been evaluated to prevent early CSA-AKI. Although correction of hemodynamic problems is paramount, there are no clinical studies that compare different hemodynamic management or monitoring strategies with regard to their effect on kidney function. Pharmacologic strategies including diuretics, different classes of vasodilators and drugs with anti-inflammatory effects such as N-acetyl-cysteine, do not appear to be effective. Most of the studies are underpowered and use physiological rather than clinical endpoints. Further trials are warranted with fenoldopam and nesiritide (rhBNP). Observational and underpowered randomized studies show beneficial renal effects of off-pump technique and avoidance of aortic manipulation. There is very limited evidence for preoperative fluid loading and preemptive RRT. Potentially nephrotoxic agents should be used with caution in patients at risk of CSA-AKI. Tranexamic acid or aminocaproic acid should be preferred over aprotinin. No pharmacologic intervention has been adequately tested in the prevention of late CSA-AKI. A single-center study, including a predominance of patients after cardiac surgery, showed a decrease of kidney injury with tight glycemic control.

Can Renal Resistive Index Predict Acute Kidney Injury After Acute Type A Aortic Dissection Repair?

BACKGROUND

This study sought to determine whether assessment of the renal resistive index (RRI) can predict the short-term reversibility of acute kidney injury (AKI) after repair of acute type A aortic dissection (TAAD).

METHODS

This prospective study included 62 patients undergoing repair of acute TAAD. Doppler-based RRIs were obtained preoperatively, immediately after the surgical procedure, and 6, 24, and 48 hours postoperatively. The occurrence of AKI was evaluated daily according to Acute Kidney Injury Network criteria. Persistent AKI was defined as AKI lasting longer than 3 days. The association between the maximum RRI level at different time points and persistent AKI was analyzed by the receiver-operating characteristic curve.

RESULTS

Of the 62 patients, 22 (35.5%) had no AKI, 21 (33.9%) had transient AKI, and 19 (30.6%) had persistent AKI. The maximum RRI was 0.67 ± 0.03 (0.62 to 0.71), 0.71 ± 0.05 (0.59 to 0.79), and 0.78 ± 0.05 (0.70 to 0.92) in the no AKI, transient AKI, and persistent AKI groups, respectively. The maximum level of RRI was significantly correlated with that of SCr during the first 48 hours postoperatively (rho = 0.606; p < 0.001). RRI could predict persistent AKI with an area under the receiver-operating characteristic curve of 0.918 (95% confidence interval, 0.850 to 0.986; p < 0.001). A postoperative RRI of 0.725 or higher was a marker for early detection of persistent AKI with high sensitivity and specificity (94.7% and 72.1%, respectively).

CONCLUSIONS

An elevated maximum RRI may be a predictor of persistent AKI after repair of acute TAAD. This is helpful for management decision making and improving the prognosis of patients with AKI.

Extracardiac Imaging of Infective Endocarditis

PURPOSE OF REVIEW

This review analyzes recent studies evaluating the diagnostic and therapeutic impacts of systematic extracardiac imaging techniques in patients with suspected or proven infective endocarditis.

RECENT FINDINGS

Extracardiac imaging techniques are more and more frequently used to establish infective endocarditis (IE) diagnosis in doubtful situations. They also help in evaluating the risk-benefit balance of therapeutic strategies and particularly valvular surgery which is performed in approximately 50% of patients. Latest research underlines the high frequency of asymptomatic lesions found, and a different advantage-disadvantage profile for each of these techniques. Extracardiac imaging techniques are helpful in doubtful situations and may be considered in other situations. Their interest for improving patients' prognosis remains to be established.

Baroreflex sensitivity and outcomes following coronary surgery

Postoperative atrial fibrillation, acute kidney dysfunction and low cardiac output following coronary surgery are associated with morbidity and mortality. The purpose of this study is to determine if the preoperative autonomic control is a determinant of these postoperative complications. This is a prospective cohort study on 150 adult patients undergoing surgical coronary revascularization with cardiopulmonary bypass. The patients received an autonomic control assessment after the induction of anesthesia. Baroreflex sensitivity was computed by spectral analysis and expressed as BRSαHF and BRSαLF for measure respectively in the high and low frequency domains. Atrial fibrillation was adjudicated at any postoperative time during the hospital stay. Acute kidney dysfunction was defined as any increase of serum creatinine levels from preoperative values within the first 48 hours after surgery, and acute kidney injury was adjudicated at a 50% increase. Low cardiac ouput syndrome was defined as the need for inotropic support > 48 hours. Thirty-eight (26.4%) patients experienced postoperative atrial fibrillation; 32 (22.2%) had acute kidney dysfunction and 5 (3.5%) acute kidney injury; 14(10%) had a low cardiac output state. No indices of baroreflex sensitivity were associated with atrial fibrillation or acute kidney injury. A low value of BRSαLF was associated with acute kidney dysfunction and low cardiac output state. A BRSαLF < 3 msec/mmHg was an independent risk factor for acute kidney dysfunction (odds ratio 3.0, 95% confidence interval 1.02–8.8, P = 0.045) and of low cardiac output state (odds ratio 17.0, 95% confidence interval 2.9–99, P = 0.002). Preoperative baroreflex sensitivity is linked to postoperative complications through a number of possible mechanisms, including an autonomic nervous system-mediated vasoconstriction, a poor response to hypotension, and an increased inflammatory reaction.

A pilot goal-directed perfusion initiative is associated with less acute kidney injury after cardiac surgery

BACKGROUND

We sought to determine whether a pilot goal-directed perfusion initiative could reduce the incidence of acute kidney injury after cardiac surgery.

METHODS

On the basis of the available literature, we identified goals to achieve during cardiopulmonary bypass (including maintenance of oxygen delivery >300 mL O2/min/m² and reduction in vasopressor use) that were combined into a goal-directed perfusion initiative and implemented as a quality improvement measure in patients undergoing cardiac surgery at Johns Hopkins during 2015. Goal-directed perfusion initiative patients were matched to controls who underwent cardiac surgery between 2010 and 2015 using propensity scoring across 15 variables. The primary and secondary outcomes were the incidence of acute kidney injury and the mean increase in serum creatinine within the first 72 hours after cardiac surgery.

RESULTS

We used the goal-directed perfusion initiative in 88 patients and matched these to 88 control patients who were similar across all variables, including mean age (61 years in controls vs 64 years in goal-directed perfusion initiative patients, P = .12) and preoperative glomerular filtration rate (90 vs 83 mL/min, P = .34). Controls received more phenylephrine on cardiopulmonary bypass (mean 2.1 vs 1.4 mg, P < .001) and had lower nadir oxygen delivery (mean 241 vs 301 mL O2/min/m², P < .001). Acute kidney injury incidence was 23.9% in controls and 9.1% in goal-directed perfusion initiative patients (P = .008); incidences of acute kidney injury stage 1, 2, and 3 were 19.3%, 3.4%, and 1.1% in controls, and 5.7%, 3.4%, and 0% in goal-directed perfusion initiative patients, respectively. Control patients exhibited a larger median percent increase in creatinine from baseline (27% vs 10%, P < .001).

CONCLUSIONS

The goal-directed perfusion initiative was associated with reduced acute kidney injury incidence after cardiac surgery in this pilot study.

The role of age and comorbidities in postoperative outcome of mitral valve repair: A propensity-matched study

The average age of patients undergoing mitral valve repair is increasing each year. This retrospective study aimed to compare postoperative complications of mitral valve repair (known to be especially high-risk) between 2 age groups: under and over the age of 80.Patients who underwent mitral valve repair were divided into 2 groups: group 1 (<80 years old) and group 2 (≥80 years old). Baseline characteristics, pre- and postoperative hemodynamic data, surgical characteristics, and postoperative follow-up data until hospital discharge were collected.A total of 308 patients were included: 264 in group 1 (age 63 ± 13 years) and 44 in group 2 (age 83 ± 2 years). Older patients had more comorbidities (atrial fibrillation, history of cardiac decompensation, systemic hypertension, pulmonary hypertension, and chronic kidney disease) and they presented more postoperative complications (50.0% vs 33.7%; P = 0.043), with a longer hospital stay (8.9 ± 6.9 vs 6.6 ± 4.6 days; P = 0.005). To assess the burden of age, a propensity score was awarded to postoperative complications. Active smoking, chronic pulmonary disease, chronic kidney disease, associated ischemic heart disease, obesity, and cardio pulmonary by-pass duration were described as independent risk factors. When matched on this propensity score, there was no difference in morbidity or mortality between group 1 and group 2.Older patients suffered more postoperative complications, which were related to their comorbidities and not only to their age.

Right ventricular systolic dysfunction and vena cava dilatation precede alteration of renal function in adult patients undergoing cardiac surgery: An observational study

BACKGROUND

Several authors have suggested that right ventricular dysfunction (RVd) may contribute to renal dysfunction in nonsurgical patients.

OBJECTIVES

We tested the hypothesis that RVd diagnosed immediately after cardiac surgery may be associated with subsequent development of renal dysfunction and tried to identify the possible mechanisms.

DESIGN

A single-centre, prospective observational study.

SETTING

Amiens University Hospital, France.

PATIENTS

All adult patients undergoing cardiac surgery were considered eligible for participation. Patients who had undergone pulmonary or tricuspid valve surgery, repeat surgery or who underwent immediate postoperative renal replacement therapy were excluded. Data from 74 patients were analysed.

MAIN OUTCOME MEASURES

Left ventricular and right ventricular function were assessed before surgery and on admission to ICU by transthoracic echocardiography (TTE): left ventricular and right ventricular ejection fractions (LVEF/RVEF), tricuspid annular plane systolic excursion (TAPSE), tricuspid annular systolic velocity (Sr(t)) and right ventricular dilatation. RVd was defined as values in the lowest quartile of at least two echocardiographic variables. Renal dysfunction was defined as an increase in serum creatinine concentration (sCr) on postoperative day 1.

RESULTS

All right ventricular TTE variables decreased (P < 0.05) after surgery: RVEF from 50% (49 to 60) to 40% (35 to 50); TAPSE from 22.3 mm (19.4 to 25.3) to 12.2 mm (8.8 to 14.8); and Sr(t) from 15.0 cm s(-1) (12.0 to 18.0) to 8.1 cm s(-1) (6.3 to 9.2). Fourteen (19%) patients had right ventricular dilatation and RVd was present in 23 (31%) patients. Forty patients had a positive variation in sCr. In multivariate analysis, patients with RVd had an odds ratio (OR) of 12.7 [95% confidence interval (95% CI) 2.6 to 63.4, P = 0.02] for development of renal dysfunction. Renal dysfunction was associated with increased central venous pressure but was not associated with cardiac index (CI).

CONCLUSION

These results suggest that early postoperative RVd is associated with a subsequent increase of sCr and that the mechanism involved is congestion (vena cava dilatation/elevated CVP) rather than decreased CI.

The pharmacological protection of renal function in patients undergoing cardiac surgery

Objectives:

To compare the effects of different routes and timings of administration of dopamine and mannitol used to alleviate the adverse effects of prolonged cardiopulmonary bypass (CPB) on renal functions in coronary artery surgery.

Methods:

Group I (n: 25 patients): Mannitol 1 g/kg was added into the priming solution for CPB. Group II (n: 25 patients): IV dopamine was administered at a dose of 2 μg/kg/min during the time period between anesthesia induction and end of surgery. Group III (n: 25 patients): IV dopamine was administered at a dose of 2 μg/kg/min during the time period between anesthesia induction and end of surgery and mannitol 1 g/kg was added into the priming solution for CPB. Group IV (n: 25 patients) (Controls): Furosemide was given when the urine output was low.

Results:

There was a significant increase in post operative urine microalbumin/creatinine ratio in all groups (p < 0.05), even increase of cystatin-c in Groups I, II and III (p < 0.01).

Conclusions:

We believe that concurrent use of dopamine infusion (2 μg/kg/min) with mannitol (1 g/kg) during CPB may represent a more effective strategy for the prevention of the untoward effects of CPB on renal functions.

The OPVI trial - perioperative hemodynamic optimization using the plethysmographic variability index in orthopedic surgery: study protocol for a multicenter randomized controlled trial

Background

Hemodynamic optimization during surgery is of major importance to decrease postoperative morbidity and length of hospital stay. However, conventional cardiac output monitoring is rarely used at the bedside. Recently, the plethysmographic variability index (PVI) was described as a simplified alternative, using plug-and-play noninvasive technology, but its clinical utility remains to be established.

Methods/design

The hemodynamic optimization using the PVI (OPVI) trial is a multicenter randomized controlled two-arm trial, randomizing 440 patients at intermediate risk of postoperative complications after orthopedic surgery. Hemodynamic optimization was conducted using either the PVI (PVI group) or conventional mean arterial pressure (control group). The anesthesiologist performed the randomization the day before surgery using an interactive web response system, available 24 hours a day, 7 days a week. The randomization sequence was generated using permutated blocks and stratified by center and type of surgery (knee or hip arthoplasty). Patients and surgeons, but not anesthesiology staff, were blinded to the allocation group. The primary outcome measure is the length of hospital stay following surgery. The attending surgeon, who was blinded to group assessment, determined hospital discharge. Secondary outcome measures are theoretical length of hospital stay, determined using a dedicated discharge-from-hospital checklist, postoperative arterial lactate level in the recovery room, postoperative troponin level, presence of serious postoperative cardiac complications, and postoperative acute kidney insufficiency.

Discussion

The OPVI trial is the first multicenter randomized controlled study to investigate whether perioperative hemodynamic optimization using PVI during orthopedic surgery could decrease the length of hospital stay and postoperative morbidity.

Trial registration

ClinicalTrials.gov NCT02207296.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-015-1020-7) contains supplementary material, which is available to authorized users.

Nadir Oxygen Delivery on Bypass and Hypotension Increase Acute Kidney Injury Risk After Cardiac Operations

BACKGROUND

Acute kidney injury (AKI) continues to complicate cardiac operations. We sought to determine whether nadir oxygen delivery (DO2) on cardiopulmonary bypass (CPB) was a risk factor for AKI while also accounting for other postoperative factors.

METHODS

Using propensity scoring, we matched 85 patients who developed AKI after cardiac operations on CPB with 85 control patients who did not. We analyzed the following variables through midnight on postoperative day 1 (POD1): DO2, antibiotics, blood products and vasopressors (intraoperatively and postoperatively), and hemodynamic variables.

RESULTS

Univariable analysis revealed AKI patients had lower nadir DO2 on CPB (208 vs 230 mL O2/min/m(2) body surface area, p = 0.03), lower intensive care unit admission blood pressure gradient across the kidney (mean arterial pressure minus central venous pressure; 60 vs 68 mm Hg; p < 0.001), a greater proportion of patients with mean arterial pressure of less than 60 mm Hg for more than 15 minutes in the postoperative period (70% vs 42%, p < 0.001), a greater chance of having a cardiac index of less than 2.2 (74% vs 49%, p = 0.02), and greater total vasopressor use through the end of POD1 (5.2 vs 2.3 mg, p = 0.002). On multivariable analysis, predictors of AKI were a DO2 on CPB of less than 225 mL O2/min/m(2) (odds ratio, 2.46; 95% confidence interval, 1.21 to 5.03; p = 0.01) and postoperative mean arterial pressure of less than 60 mm Hg for more than 15 minutes (odds ratio, 3.96; 95% confidence interval, 1.92 to 8.20; p < 0.001). An average postoperative pressor dose greater than 0.03 μg/kg/min did not reach significance (odds ratio, 1.98; 95% confidence interval, 0.95 to 4.11; p = 0.07).

CONCLUSIONS

Postoperative hypotension on POD0 or POD1 and low DO2 on CPB both independently increase the AKI risk in cardiac surgical patients.

Pre- and/or Intra-Operative Prescription of Diuretics, but Not Renin-Angiotensin-System Inhibitors, Is Significantly Associated with Acute Kidney Injury after Non-Cardiac Surgery: A Retrospective Cohort Study

Background and Objectives

Pre- and/or intra-operative use of diuretics, angiotensin-converting enzyme inhibitors (ACE-I) or angiotensin II receptor blockers (ARB) constitutes a potentially modifiable risk factor for postoperative acute kidney injury (AKI). It has been studied whether use of these drugs predicts AKI after cardiac surgery. The objective of this study was to examine whether administration of these agents was independently associated with AKI after non-cardiac surgery.

Design, Setting, Participants, and Measurements

This was a retrospective observational study. Inclusion criteria were adult patients (age ≥ 18) who underwent non-cardiac surgery under general anesthesia from 2007 to 2009 at Kyoto Katsura Hospital. Exclusion criteria were urological surgery, missing creatinine values, and preoperative dialysis. The exposures of interest were pre- and/or intra-operative use of diuretics or ACE-I/ARB. Outcome variables were postoperative AKI as defined by the AKI Network (increase in creatinine ≥ 0.3 mg/dL or 150% within 48 hours, or urine output < 0.5 ml/kg/hour for > 6 hours). Multivariable logistic regression analyses were conducted and adjusted for potential confounders. Propensity scores (PS) for receiving diuretics or ACE-I/ARB therapy were estimated and PS adjustment, PS matching, and inverse probability weighting were performed.

Results

There were 137 AKI cases (5.0%) among 2,725 subjects. After statistical adjustment for patient and surgical characteristics, odds (95% CI) of postoperative AKI were 2.07 (1.10-3.89) (p = 0.02) and 0.89 (0.56-1.42) (p = 0.63) in users of diuretics and ACE-I/ARB, respectively, compared with non-users. PS adjustment, PS matching, and inverse probability weighting yielded similar results. The effect size of diuretics was significantly greater in the patients with lower propensity for diuretic use (p for interaction < 0.1).

Conclusions

Prescription of diuretics, but not ACE-I/ARB, was independently associated with postoperative AKI after non-cardiac surgery, especially in patients with low propensity for diuretic use. It might be reasonable to withhold preoperative diuretics in these patients.

Acute Kidney Injury and Hemodilution During Cardiopulmonary Bypass: A Changing Scenario

BACKGROUND

Severe hemodilution during cardiopulmonary bypass (CPB) is a risk factor for acute kidney injury (AKI) after heart operations. Many improvements to CPB technology have been proposed during the past decade to limit the hemodilution-related AKI risk. The present study is a retrospective analysis of the relationship between hemodilution during CPB and AKI in cardiac operations in the setting of different interventions applied over 14 years.

METHODS

We retrospectively analyzed 16,790 consecutive patients undergoing heart operations from 2000 to 2013. Various risk factors for AKI were collected and analyzed, together with a number of interventions as possible modifiers of the relationship between a nadir hematocrit (HCT) value during CPB and AKI.

RESULTS

The relationship between the nadir HCT value during CPB and AKI was confirmed in a multivariable analysis, with the relative risk of AKI increasing by 7% per percentage point of decrease of the nadir HCT value during CPB. The relative risk of AKI decreased by 8% per year of observation (p = 0.001) despite a significantly increased risk of AKI (p = 0.001). A sensitivity analysis based on differences before and after different interventions demonstrated a beneficial effect of the application of goal-directed perfusion (aimed at preserving oxygen delivery during CPB), with a reduction in the AKI rate from 5.8% to 3.1% (p = 0.001). A policy restricting angiographic examination on the day of operation was also useful (reduction of AKI rate from 4.8% to 3.7%; p = 0.029).

CONCLUSIONS

A bundle of interventions mainly aimed at limiting the renal impact of hemodilution during CPB is effective in reducing the AKI rate.

Preoperative renin-angiotensin system inhibitors use linked to reduced acute kidney injury: a systematic review and meta-analysis

BACKGROUND

Previous trials of interventions to prevent acute kidney injury (AKI) have been unsuccessful and additional interventions are needed. Existing reviews of preoperative renin-angiotensin system (RAS) inhibitors have suggested harm. We included more recent studies and conducted this meta-analysis to evaluate the risk of postoperative AKI in patients who received preoperative RAS inhibitors.

METHODS

A literature search was performed using MEDLINE, EMBASE and Cochrane Database of Systematic Reviews from inception through October, 2014. Studies that reported relative risks, odds ratios or hazard ratios comparing the AKI risk in patients who received preoperative RAS inhibitors versus those who did not were included. We performed the prespecified sensitivity analysis including only propensity score-based studies. Mortality risk was evaluated among the studies that reported AKI outcome. Pooled risk ratios (RR) and 95% confidence interval (CI) were calculated using a random-effect, generic inverse variance method.

RESULTS

Twenty-four studies (1 randomized controlled trial and 23 cohort studies) with 102 675 patients were included in the analysis to assess the risk of postoperative AKI and preoperative RAS inhibitors use. The pooled RR of AKI in patients receiving RAS inhibitors was 1.05 (95% CI: 0.92-1.20). The meta-analysis of the RCT and 11 studies with propensity score analysis demonstrated the pooled RR of AKI in patients receiving RAS inhibitors of 0.92 (95% CI: 0.85-0.99). Within the selected studies, preoperative RAS inhibitor therapy was not associated with a significant increase or decrease in mortality (RR: 0.93; 95% CI: 0.80-1.09).

CONCLUSIONS

Our meta-analysis demonstrates an association between preoperative RAS inhibitor treatment and lower incidence of AKI.

AKI associated with cardiac surgery

Approximately 18% of patients undergoing cardiac surgery experience AKI (on the basis of modern standardized definitions of AKI), and approximately 2%-6% will require hemodialysis. The development of AKI after cardiac surgery portends poor short- and long-term prognoses, with those developing RIFLE failure or AKI Network stage III having an almost 2-fold increase in the risk of death. AKI is caused by a variety of factors, including nephrotoxins, hypoxia, mechanical trauma, inflammation, cardiopulmonary bypass, and hemodynamic instability, and it may be affected by the clinician's choice of fluids and vasoactive agents as well as the transfusion strategy used. The risk of AKI may be ameliorated by avoidance of nephrotoxins, achievement of adequate glucose control preoperatively, and use of goal-directed therapy hemodynamic strategies. Remote ischemic preconditioning is an exciting future strategy, but more work is needed before widespread implementation. Unfortunately, there are no pharmacologic agents known to reduce the risk of AKI or treat established AKI.

Ultrasonographic evaluation of abdominal organs after cardiac surgery

BACKGROUND

Disturbances of the hepatosplanchnic region may occur after cardiac operations. Experimental studies have implicated impairment of splanchnic blood supply in major abdominal organ dysfunction after cardiopulmonary bypass (CPB). We investigated the impact of the cardiac operation and CPB on liver, kidney, and renal perfusion and function by means of ultrasonography and biochemical indices in a selected group of cardiac surgery patients.

MATERIALS AND METHODS

Seventy five patients scheduled for a major cardiac operation were prospectively included in the study. Criteria for selection were moderate or good left ventricular ejection fraction and absence of previous hepatic or renal impairment. Ultrasound examination of the hepatic and renal vasculature and examination of biochemical parameters were performed on the day preceding the operation (T0), on the first postoperative day (T1), and on the seventh postoperative day (T2).

RESULTS

Portal vein velocity and flow volume increased significantly, whereas hepatic artery velocity and flow volume decreased at T1 in comparison with T0. Hepatic vein indices remained unaffected throughout the observation period. Renal artery velocity and flow decreased, whereas renal pulsatility index and renal resistive index increased at T1 as compared with T0. Aspartate aminotransferase and alanine aminotransferase values were increased as compared with baseline values 24 h postoperatively. All parameters displayed a trend to approach preoperative levels at T2. Strong negative correlations between alanine aminotransferase values at T1 and hepatic artery velocity and flow volume at the same time point were also demonstrated (R = 0.638, P < 0.001 and r = 0.662, P < 0.001, respectively).

CONCLUSIONS

The increase in portal vein flow and velocity and the decrease in hepatic artery flow and velocity in the period after CPB might be attributed to the hypothermic bypass technique and the hepatic arterial buffer response, respectively. The decrease in renal blood flow and velocity and the parallel increase in Doppler renal pulsatility index and renal resistive index could be considered as markers of kidney hypoperfusion and intrarenal vasoconstriction. Maintaining a high index of suspicion for the early diagnosis of noncardiac complications in the period after CPB and institution of supportive care in case of compromised splanchnic perfusion are warranted.

Decline in serum hemoglobin in the 7 days after cardiac catheterization

OBJECTIVES

Bleeding is an established complication following cardiac catheterization and lower preoperative hemoglobin concentration is a potentially modifiable risk factor for adverse outcomes after cardiac surgery. However, typical changes in serum hemoglobin concentration after cardiac catheterization are poorly defined. The authors sought to identify the pattern of change in serum hemoglobin concentration within 7 days after cardiovascular catheterization, factors associated with this change and any association with adverse outcomes.

DESIGN

Retrospective observational study over a 1-year period.

SETTING

U.S. academic medical institution.

PARTICIPANTS

Participants were 284 adult patients with baseline hemoglobin concentration≥12 g/dL undergoing nonemergent cardiac surgery after cardiovascular catheterization via the femoral arterial route.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Lowest daily hemoglobin concentration was recorded where available for up to 7 days after catheterization and before surgery. Generalized estimating equations identified the pattern of change in serum hemoglobin while regression models identified factors associated with hemoglobin decline. Following cardiovascular catheterization average serum hemoglobin declined over time, reaching a nadir 1.4 g/dL (95% CI 1.0-1.8) below baseline 6 days after catheterization. A higher baseline hemoglobin concentration and lower body mass index were associated with greater maximal decline in hemoglobin concentration after catheterization. Acute preoperative hemoglobin decline was not associated with acute kidney injury (AKI) or a composite adverse outcome that may reflect organ ischemia.

CONCLUSIONS

In a cohort of patients before cardiac surgery serum hemoglobin declines during the week after cardiac catheterization, with maximal average decline observed 5 to 7 days after catheterization.

Increasing mean arterial pressure during cardiac surgery does not reduce the rate of postoperative acute kidney injury

Introduction:

We hypothesized that the optimization of renal haemodynamics by maintaining a high level of mean arterial blood pressure (MAP) during cardiopulmonary bypass (CPB) could reduce the rate of acute kidney injury (AKI) in high-risk patients.

Methods:

In this randomized, controlled study, we enrolled 300 patients scheduled for elective cardiac surgery under cardiopulmonary bypass. All had known risk factors of AKI: serum creatinine clearance between 30 and 60 ml/min for 1.73m2 or two factors among the following: age >60 years, diabetes mellitus, diffuse atherosclerosis. After a standardized fluid loading, the MAP was maintained between 75-85 mmHg during CPB with norepinephrine (High Pressure, n=147) versus 50-60 mmHg in the Control (n=145). AKI was defined by a 30% increased of serum creatinine (sCr). We further tested others definitions for AKI: RIFLE classification, 50% rise of sCr and the need for haemodialysis.

Results:

The pressure endpoints were achieved in both the High Pressure (79 ± 6 mmHg) and the Control groups (60 ± 6 mmHg; p<0.001). The rate of AKI did not differ by group (17% vs. 17%; p=1), whatever the criteria used for AKI. The length of stay in hospital (9.5 days [7.9-11.2] vs. 8.2 [7.1-9.4]) and the rate of death at day 28 (2.1% vs. 3.4%) and at six months (3.4% vs. 4.8%) did not differ between the groups.

Conclusion:

Maintaining a high level of MAP (on average) during normothermic CPB does not reduce the risk of postoperative AKI. It does not alter the length of hospital stay or the mortality rate.

An update on acute kidney injury after cardiac surgery

Renal dysfunction following cardiac surgery is well recognised and mainly is of ischaemic origin. The spectrum varies from subclinical injuryto established renal failure requiring renal replacement therapy. Depending on definitions, acute kidney injury (AKI) may occur in up to 30% of post cardiac surgery patients. A new grading system for renal dysfunction, based on three levels of plasma creatinine and urine output, as well as the use of biomarkers may help the early identification of patients at risk and thereby hopefully improve outcome. Despite therapeutic advances, the morbidity and mortality associated with AKI have not changed markedly in the last decade.

Relation between the interval from coronary angiography to selective off-pump coronary artery bypass grafting and postoperative acute kidney injury

The aim of this study was to investigate whether there are effects of intervals between elective off-pump coronary artery bypass grafting (OPCABG) and coronary angiography (CAG) on postoperative acute kidney injury (AKI). The clinical data of patients undergoing OPCABG and CAG from June 2010 to December 2011 in Beijing Anzhen Hospital were retrospectively analyzed. All the patients were divided into AKI and non-AKI groups. Univariate analysis was performed to find possible factors associated with AKI. Multivariate logistic regression analysis was used to identify whether the short interval was one of the independent risk factors of AKI after adjusting for potential confounding variables. Of 1,513 patients, 529 patients (34.9%) developed AKI. The mortality rate in AKI group (4.9%) was >5× higher than that in non-AKI group (0.9%). The incidence of AKI was highest (56.1%) in patients in whom OPCABG was performed ≤24 hours after CAG. Multivariate logistic regression analysis showed that the interval of ≤24 hours between OPCABG and CAG did increase the risk of AKI (odds ratio 2.15, 95% confidence interval 1.10 to 4.20) after adjusting for the following confounding variables: diabetes mellitus, New York Heart Association heart function class III and IV, lower estimated glomerular filtration rate, numbers of coronary artery bypass grafts ≥3, intraoperative or postoperative intra-aortic balloon pump, intraoperative and postoperative red blood cells transfusion of >3 units, postoperative hypotension, dosage of furosemide of >100 mg/day. In conclusion, it was one of the independent risk factors of postoperative AKI that the OPCABG was performed ≤24 hours after CAG.

Renal function changes and seasonal temperature in patients undergoing cardiac surgery

Some observations in humans and other mammalians suggest that serum creatinine (SC) and estimated glomerular filtration rate (eGFR) may change during the warm season. The objective of this study is to determine if temperature-dependent seasonal changes in levels of SC and eGFR are detectable in cardiac surgery patients, with associated changes in postoperative acute kidney injury (AKI) incidence. This is a single-center retrospective study based on the institutional database of cardiac surgery in the period 2000-2012. Sixteen-thousand and twenty-three consecutive adult patients undergoing cardiac surgery comprised the study population. Baseline and postoperative SC and eGFR values, and AKI rate according to the month when surgery was performed were measured. The month-related changes SC and eGFR, and AKI rate, were assessed in crude and adjusted models, and their association with the correspondent meteorological data registered at the time of surgery was tested. Patients operated in the six warmest months (May through October) had a significant (p < 0.001) higher value of baseline SC (1.17 ± 0.7 mg/dL) versus the six coldest months (1.12 ± 0.6 mg/dL), and a significantly (p = 0.031) higher value of peak postoperative SC (1.31 ± 0.85 mg/dL) versus the 6 coldest months (1.28 ± 0.89), with maximum values between July and August. A similar behaviour was found for eGFR. After adjustment for other confounders, the AKI rate was not significantly different in the warmest months, even if a trend towards a higher rate in August was observed (odds ratio 1.287, 95% confidence interval 0.96-1.74, p = 0.097). Baseline (p < 0.001) and peak postoperative (p = 0.0054) serum creatinine levels were significantly higher for increasing mean ambient temperature. Humidity and wind speed were negatively associated with pre- and postoperative eGFR. In conclusion, patients operated during the warmest season, have higher levels of SC and lower levels of eGFR, without a correspondent increase in the AKI rate. Different hypotheses underlying this pattern are generated by this study, including a dehydration status, concomitant anemia, and a higher transfusion rate.

Implementation of an intraoperative glycemic control protocol for cardiac surgery in a high-acuity academic medical center: an observational study

STUDY OBJECTIVE

To examine the effect on morbidity and mortality of an established intraoperative insulin protocol in cardiac surgical patients.

DESIGN

Retrospective observational study.

SETTING

Single-center, 782 bed, metropolitan academic hospital.

PATIENTS

1,616 adult patients undergoing cardiac surgical procedures with cardiopulmonary bypass (CPB).

INTERVENTIONS

An intraoperative, intravenous (IV) insulin protocol designed to maintain blood glucose values less than 150 mg/dL was implemented.

MEASUREMENTS

Blood glucose was evaluated on entry to the operating room, every 30 minutes during CPB, and at least once after discontinuation of CPB. Blood glucose values were followed postoperatively, as dictated by institutional policy.

MAIN RESULTS

Intraoperative predictors of 30-day mortality using multivariate logistic regression included hyperglycemia on initiation of CPB (OR 1.0, P = 0.05). The strongest predictor of 30-day mortality was the development of postoperative renal failure requiring hemodialysis (OR 3.26, P = 0.001).

CONCLUSIONS

Implementation of an intraoperative IV insulin protocol, while associated with improved glycemic control, was not associated with improved outcomes. While improved glycemic control on initiating CPB was associated with decreased 30-day mortality, the effect was small. Implementation of our insulin protocol was highly associated with decreased renal failure postoperatively. Further prospective studies are warranted to better establish causality.

Acute kidney injury after cardiac surgery: does the time interval from contrast administration to surgery matter?

OBJECTIVE

The authors sought to evaluate the association between the time interval from contrast administration to cardiac surgery and postoperative acute kidney injury (AKI).

DESIGN

A retrospective observational study over a 1-year period.

SETTING

A US academic medical institution.

PARTICIPANTS

Six hundred forty-four adult patients undergoing nonemergent cardiac surgery.

INTERVENTIONS

No interventions were performed as part of the study.

MEASUREMENTS AND MAIN RESULTS

AKI was defined as an increase in serum creatinine by ≥0.3 mg/dL or ≥50% above baseline within the first 2 postoperative days or the commencement of renal replacement therapy within the same period. Using a contrast-to-surgery time interval >7 days as the baseline, multivariable logistic regression analysis determined the association between a contrast-to-surgery time interval ≤1 day or 2 to 7 days and postoperative AKI adjusting for potential confounding variables. The incidence of AKI within the study cohort was 21.9%. After adjusting for other covariates, there was no association between the contrast-to-surgery time and AKI (odds ratio [OR] ≤1 day = 0.93; 95% confidence interval [CI], 0.52-1.66; p = 0.81; OR = 2-7 days = 1.28; 95% CI, 0.78-2.11; p = 0.34).

CONCLUSIONS

In an appropriately selected population, cardiac surgery can be performed within 1 day of cardiovascular catheterization and contrast administration without an increase in the incidence of postoperative AKI. Recommendations to delay cardiac surgery for a specified period after contrast administration to reduce the risk of postoperative AKI are premature. Additional evidence is required before making recommendations on optimal surgical timing after contrast exposure.

The influence of mean arterial blood pressure during cardiopulmonary bypass on postoperative renal dysfunction in elderly patients

The aim of the study was to find out if there is an optimal mean arterial blood pressure (MABP) during cardiopulmonary bypass (CPB) for renal function in elderly patients during the early postoperative period. We analysed the data of 122 patients >70 years of age with normal preoperative renal function who had been subjected to coronary artery bypass grafting (CABG) procedures on CPB. Patients were divided into 3 groups, according to MABP during CPB: group MP (n=50) included patients whose MABP was maintained between 60-70 mmHg; group LP (n=36), the MABP was <60 mmHg; and group HP (n=36) where the MABP was >70 mmHg. The patients' clinical data were evaluated during the first three postoperative days. The rate of renal impairment (urine output <50ml/h) in the early postoperative period after cardiac surgery did not differ among the groups. Oliguria developed in 3 patients (6%) of the MP group, in 2 patients (5.6%) in the LP group and in 6 patients (16.7%) in the HP group (χ(2)=3.6, df=2, p=0.161). Evaluation of MABP on renal excretion showed that there was no difference in urine output among the groups. Serum creatinine levels at the end of the first postoperative day in groups MP, LP and HP were 102.7±20.1, 116.4±58.6 and 113.2±39.8 µmol/L, respectively (F=0.5, df=2, p=0.640). There were no significant differences among the groups at the end of the second and the third day either. Volume balance at the end of surgery and during the early postoperative period was similar in all groups. The need for diuretics did not differ among the groups. The length of postoperative hospital stay was not significantly different among the groups. Our study did not reveal any relationship between a MABP of 48-80 and postoperative renal dysfunction in elderly patients after CABG surgery.

Which method of estimating renal function is the best predictor of mortality after coronary artery bypass grafting?

OBJECTIVES

Definitions of renal function in patients undergoing coronary artery bypass graft surgery (CABG) vary in the literature. We sought to investigate which method of estimating renal function is the best predictor of mortality after CABG.

METHODS

We analysed the preoperative and postoperative renal function data from all patients undergoing isolated CABG from January 1998 through December 2007. Preoperative and postoperative renal function was estimated using serum creatinine (SeCr) levels, creatinine clearance (CrCl) determined by the Cockcroft-Gault formula and the glomerular filtration rate (e-GFR) estimated by the Modification of Diet in Renal Disease (MDRD) formula. Receiver operator characteristic (ROC) curves and area under the ROC curves were calculated.

RESULTS

In 9987 patients, CrCl had the best discriminatory power to predict early as well as late mortality, followed by e-GFR and finally SeCr. The odds ratios for preoperative parameters for early mortality were closer to 1 than those of the postoperative parameters.

CONCLUSIONS

Renal function determined by the Cockcroft-Gault formula is the best predictor of early and late mortality after CABG. The relationship between renal function and mortality is non-linear. Renal function as a variable in risk scoring systems such as the EuroSCORE needs to be reconsidered.

Association between postoperative acute kidney injury and duration of cardiopulmonary bypass: a meta-analysis

OBJECTIVE

This meta-analysis examined the association between cardiopulmonary bypass (CPB) time and acute kidney injury (AKI).

DESIGN

Meta-analysis of previously published studies.

SETTING

Each single-center study was conducted in a surgical intensive care unit and/or academic or university hospital.

PARTICIPANTS

Adult patients undergoing heart surgery with CPB.

INTERVENTIONS

A systematic literature review was conducted using PubMed, EMBASE, and Cochrane Library databases and Google Scholar from January 1980 through September 2009. Initial search results were refined to include human subjects, age >18 years, randomized controlled trials, and prospective and retrospective cohort studies, meet the Acute Kidney Injury Network definition of renal failure, and report times on CPB.

MEASUREMENTS AND MAIN RESULTS

The length of time on CPB has been implicated as an independent risk factor for development of AKI after CPB (AKI-CPB). The 9 independent studies included in the final meta-analysis had 12,466 patients who underwent CPB. Out of these, 756 patients (6.06%) developed AKI-CPB. In 7 of the 9 studies, the mean CPB times were statistically longer in the AKI-CPB cohort compared with the control group (cohort without AKI). The absolute mean differences in CPB time between the 2 groups were 25.65 minutes with the fixed-effects model and 23.18 minutes with the random-effects model.

CONCLUSIONS

Longer CPB times are associated with a higher risk of developing AKI-CPB, which, in turn, has a significant effect on overall mortality as reported by the individual studies.

O2 delivery and CO2 production during cardiopulmonary bypass as determinants of acute kidney injury: time for a goal-directed perfusion management?

INTRODUCTION

Acute kidney injury (AKI) is common after cardiac operations. There are different risk factors or determinants of AKI, and some are related to cardiopulmonary bypass (CPB). In this study, we explored the association between metabolic parameters (oxygen delivery (DO2) and carbon dioxide production (VCO2)) during CPB with postoperative AKI.

METHODS

We conducted a retrospective analysis of prospectively collected data at two different institutions. The study population included 359 adult patients. The DO2 and VCO2 levels of each patient were monitored during CPB. Outcome variables were related to kidney function (peak postoperative serum creatinine increase and AKI stage 1 or 2). The experimental hypothesis was that nadir DO2 values and nadir DO2/VCO2 ratios during CPB would be independent predictors of AKI. Multivariable logistic regression models were built to detect the independent predictors of AKI and any kind of kidney function damage.

RESULTS

A nadir DO2 level < 262 mL/minute/m2 and a nadir DO2/VCO2 ratio < 5.3 were independently associated with AKI within a model including EuroSCORE and CPB duration. Patients with nadir DO2 levels and nadir DO2/VCO2 ratios below the identified cutoff values during CPB had a significantly higher rate of AKI stage 2 (odds ratios 3.1 and 2.9, respectively). The negative predictive power of both variables exceeded 90%. The most accurate predictor of AKI stage 2 postoperative status was the nadir DO2 level.

CONCLUSIONS

The nadir DO2 level during CPB is independently associated with postoperative AKI. The measurement of VCO2-related variables does not add accuracy to the AKI prediction. Since DO2 during CPB is a modifiable factor (through pump flow adjustments), this study generates the hypothesis that goal-directed perfusion management aimed at maintaining the DO2 level above the identified critical value might limit the incidence of postoperative AKI.