Perioperative hemoglobin area under the curve is an independent predictor of renal failure after cardiac surgery. Results from a Spanish multicenter retrospective cohort study

Development and Validation of a Risk Model for Predicting Contrast-Associated Acute Kidney Injury in Patients With Cancer: Evaluation in Over 46,000 CT Examinations

BACKGROUND. Patients with cancer undergo frequent CT examinations with iodinated contrast media and may be uniquely predisposed to contrast-associated acute kidney injury (CA-AKI). OBJECTIVE. The purpose of this study was to develop and validate a model for predicting the risk of CA-AKI after contrast-enhanced CT in patients with cancer. METHODS. This retrospective study included 25,184 adult patients (12,153 men, 13,031 women; mean age, 62.3 ± 13.7 [SD] years) with cancer who underwent 46,593 contrast-enhanced CT examinations between January 1, 2016, and June 20, 2020, at one of three academic medical centers. Information was recorded regarding demographics, malignancy type, medication use, baseline laboratory values, and comorbid conditions. CA-AKI was defined as a 0.3-mg/dL or greater increase in serum creatinine level from baseline within 48 hours after CT or a 1.5-fold or greater increase in the peak measurement within 14 days after CT. Multivariable models accounting for correlated data were used to identify risk factors for CA-AKI. A risk score for predicting CA-AKI was generated in a development set (n = 30,926) and tested in a validation set (n = 15,667). RESULTS. CA-AKI occurred after 5.8% (2682/46,593) of CT examinations. The final multivariable model for predicting CA-AKI included hematologic malignancy, diuretic use, angiotensin-converting enzyme inhibitor or angiotensin receptor blocker use, chronic kidney disease (CKD) stage 3a, CKD stage 3b, CKD stage 4 or 5, serum albumin level less than 3.0 g/dL, platelet count less than 150 × 103/μL, 1+ or greater proteinuria on baseline urinalysis, diabetes mellitus, heart failure, and contrast medium volume 100 mL or greater. A risk score (range, 0-53 points) was generated with these variables. The most points (13) were for CKD stage 4 or 5 and for albumin level less than 3 g/dL. The frequency of CA-AKI progressively increased in higher risk categories. For example, in the validation set, CA-AKI occurred after 2.2% of CT examinations in the lowest risk category (score ≤ 4) and after 32.7% of CT examinations in the highest risk category (score ≥ 30). The Hosmer-Lemeshow test result indicated that the risk score was a good fit (p = .40). CONCLUSION. A risk model in which readily available clinical data are used to predict the likelihood of CA-AKI after contrast-enhanced CT in patients with cancer was developed and validated. CLINICAL IMPACT. The model may help facilitate appropriate implementation of preventive measures in the care of patients at high risk of CA-AKI.

The effect of anemia on the severity and prognosis of patients with acute pancreatitis: A single-center retrospective study

Anemia was a risk factor for a worse prognosis of many diseases. This study aims to investigate the relationship between anemia and the severity and prognosis of acute pancreatitis (AP). Inpatients hospitalized at the First Affiliated Hospital of Guangdong Pharmaceutical University with a primary diagnosis of AP between 1st July 2016 to 31st December 2020 were enrolled. Subsequently, disease severity, the incidence of complications, and the prognosis of patients with AP were compared between the anemic group and the non-anemic group. A total of 282 patients with acute pancreatitis were enrolled; 68.43% of them were also diagnosed with anemia. Notably, these patients had more severe disease (higher RANSON, acute physiologic assessment and chronic health evaluation-II, bedside index for severity in acute pancreatitis, and multiple organ dysfunction syndrome scores); higher incidence of organ failure (acute kidney injury [AKI] and acute heart failure); worse prognosis (higher incidence of vasoactive and diuretic agent use, longer hospital stays, and higher hospital costs) compared to that of patients without anemia (all P < .05). After adjusting for potential confounders, acute physiologic assessment and chronic health evaluation-II, bedside index for severity in acute pancreatitis, multiple organ dysfunction syndrome scores, hospital stay, and hospital costs in anemic patients were higher than those in non-anemic patients; besides, the incidence of AKI and using a diuretic agent in anemic patients was 6.645 and 4.053 times that of non-anemic patients in AP, respectively (all P < .05). Acute pancreatitis patients with anemia have more disease severity, higher incidence of AKI, and worse prognosis compared to those without anemia.

Perioperative Management of the Patient at High-Risk for Cardiac Surgery-Associated Acute Kidney Injury

Acute kidney injury (AKI) is one of the most common major complications of cardiac surgery, and is associated with increased morbidity and mortality. Cardiac surgery-associated AKI has a complex, multifactorial etiology, including numerous factors such as primary cardiac dysfunction, hemodynamic derangements of cardiac surgery and cardiopulmonary bypass, and the possibility of a large volume of blood transfusion. There are no truly effective pharmacologic therapies for the management of AKI, and, therefore, anesthesiologists, intensivists, and cardiac surgeons must remain vigilant and attempt to minimize the risk of developing renal dysfunction. This narrative review describes the current state of the scientific literature concerning the specific aspects of cardiac surgery-associated AKI, and presents it in a chronological fashion to aid the perioperative clinician in their approach to this high-risk patient group. The evidence was considered for risk prediction models, preoperative optimization, and the intraoperative and postoperative management of cardiac surgery patients to improve renal outcomes.

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.

Association between transfusion of blood products and acute kidney injury following cardiac surgery

BACKGROUND

Acute kidney injury (AKI) is a serious complication following cardiac surgery associated with increased mortality. Red blood cell transfusion enhances the risk of developing AKI. However, the impact of other blood products on AKI is virtually unexplored. The aim of this study was to explore if transfusion of red blood cells, fresh frozen plasma and platelets alone or in combination were associated with postoperative AKI.

METHODS

Patients undergoing elective on-pump cardiac surgery were included (n = 1960) between 2012 to 2014. Transfusion data were collected intraoperatively and until the first postoperative day. AKI was classified according to the KDIGO criteria. Data were analysed using univariate and stepwise multiple logistic regression with adjustment for clinical risk factors and complementary blood products.

RESULTS

AKI was observed in 542 patients (27.7%). In univariate analysis and following adjustment for clinical risk factors, administration of red blood cells, freshfrozen plasma and platelets were all independently associated with KDIGO stage 2-3. Following additional adjustment for complementary blood products, only red blood cell transfusion remained significantly associated with AKI. A dose-dependent association between volume of red blood cells and degree of AKI severity was observed.

CONCLUSION

Transfusion of all blood products in a dose-dependent manner increased the risk for AKI. However, in multivariate analysis combining all blood products, only red blood cell transfusion remained significantly associated with AKI development.

Strategies to Reduce Perioperative Nephrotoxicity

Postoperative acute kidney injury (AKI) is a common complication of surgery that is associated with significant adverse outcomes, including increased morbidity and mortality. The perioperative burden of AKI risk factors is complex and potentially large, including high-risk nephrotoxic medications, hypotension, hypovolemia, radiologic contrast, anemia, and surgery-specific factors. Understanding the pathogenesis, risk factors, and potential cumulative impact of perioperative nephrotoxic exposures is particularly important in the prevention and reduction of perioperative AKI. This review outlines the possible strategies to reduce perioperative nephrotoxicity and the development of postoperative AKI.

Complete blood count in acute kidney injury prediction: a narrative review

Acute kidney injury (AKI) is a complex syndrome defined by a decrease in renal function. The incidence of AKI has raised in the past decades, and it is associated with negative impact in patient outcomes in the short and long term. Considering the impact of AKI on patient prognosis, research has focused on methods to assess patients at risk for developing AKI, diagnose subclinical AKI, and on prevention and treatment strategies, for which it is crucial an understanding of pathophysiology the of AKI. In this review, we discuss the use of easily available parameters found in a complete blood count to detect patients at risk for developing AKI, to provide an early diagnosis of AKI, and to predict associated patient outcomes.

Novel method for estimating the total blood volume: the importance of adjustment using the ideal body weight and age for the accurate prediction of haemodilution during cardiopulmonary bypass

OBJECTIVES

Although total blood volume (TBV) is central to the estimation of the haemodilution rate during cardiopulmonary bypass (CPB), conventional formulas lack sufficient accuracy. The aim of this study was to establish a new formula using ideal body weight (BW) with adjustment for gender or age to estimate TBV for a more accurate prediction of the haemodilution rate during CPB.

METHODS

A total of 214 consecutive patients who underwent cardiac surgery with CPB were included in this study. TBV was retrospectively estimated using the following formulae: (1) Conventional TBV = actual BW × fixed 70 ml/kg, (2) gender-based modified TBV = ideal BW × 75 ml/kg (male) or 65 ml/kg (female) and (3) age-based modified TBV = ideal BW × 70 ml/kg (<65 years old) or 60 ml/kg (≥65 years old). The relationship between actual and predicted haemodilution rates calculated by these formulas was examined.

RESULTS

The actual haemodilution rate based on the haematocrit value was 24.4 ± 4.4%. There was no significant correlation between the actual and predicted haemodilution rates obtained by the conventional formula, whereas both modified formulae with the ideal BW showed a significant correlation. Furthermore, the age-based modified formula showed the highest correlation level (r = 0.45, P < 0.001) as well as a strong correlation between the actual and predicted postdilution haematocrit values (y = 0.903x + 3.385, R2 = 0.892).

CONCLUSIONS

The conventional formula is unable to predict the actual haemodilution rate accurately. Our new formula with a combination of the ideal BW and adjustment for age was shown to be useful for the accurate prediction of the haemodilution rate during CPB.

Acute kidney injury after cardiac surgery: prevalence, impact and management challenges

Acute kidney injury (AKI) is a major medical problem that is of particular concern after cardiac surgery. Perioperative AKI is independently associated with an increase in short-term morbidity, costs of treatment, and long-term mortality. In this review, we explore the definition of cardiac surgery-associated acute kidney injury (CSA-AKI) and identify diverse mechanisms and risk factors contributing to the renal insult. Current theories of the pathophysiology of CSA-AKI and description of its clinical course will be addressed in this review. Data on the most promising renal protective strategies in cardiac surgery, from well-designed studies, will be scrutinized. Furthermore, diagnostic tools such as novel biomarkers of AKI and their potential utility will be discussed.

Biomarkers of Acute Kidney Injury after Cardiac Surgery: A Narrative Review

Cardiac surgery-associated acute kidney injury (CSA-AKI) is a major and serious complication in patients undergoing cardiac surgery and is independently associated with perioperative mortality and mortality. Therapeutic intervention aiming at reversing kidney dysfunction seems disappointing across multiple settings. Consequently, attention has shifted from treatment to prevention and early detection. The Kidney Disease: Improving Global Outcomes (KDIGO) guidelines have unified diagnostic standards mainly based on the serum creatinine (Scr) level or urine output, but neither marker is kidney specific. Efforts have been made to identify novel biomarkers with high sensitivity and specificity. The diagnostic capabilities of neutrophil gelatinase-associated lipocalin (NGAL) and G1 cell cycle arrest biomarker as biomarkers have been confirmed in a large number of clinical trials. The utility of biomarkers of cardiac function and inflammation has been validated in clinical studies. Aiming to offer valuable information for further research, we summarize the progress in defining current markers relevant to CSA-AKI in the last three years.

Preventing complications by persistence with iron replacement therapy: a comprehensive literature review

OBJECTIVE

Iron deficiency and particularly iron deficiency anemia (IDA) can lead to negative health consequences. This review describes the importance of adherence and persistence (adhering to treatment for the recommended duration) with iron replacement therapy in the prevention of complications, particularly regarding its recommended dosing schedule.

METHODS

Comprehensive literature searches were performed of Medline and the Cochrane library from 2000 to 2018. Keywords included iron deficiency or IDA, compliance or adherence, persistence, health beliefs, risk factor, complications, dosing cycles, oral iron replacement therapy and recommendations for duration, ferrous compounds, iron supplementation, dietary iron, and delayed-action/slow-release preparations.

RESULTS

Identified articles focused on IDA as a risk factor (particularly for worsened comorbidities or surgical outcomes), guidelines, adherence and persistence, and differences between iron formulations. Current guidelines and expert opinion continue to support oral iron supplementation as first-line therapy. While it is recommended to take iron therapy for 2 months to normalize hemoglobin, then 2-3 months to build up iron stores, many patients face difficulties in adhering to and persisting with the full iron treatment regimen. Patient education and understanding, social support, simple dosing, perceived efficacy including reduced symptoms and tolerability were factors noted to promote medication adherence and persistence. Adherence to iron therapies appears to be facilitated by using ferrous sulfate due to its optimal absorption, and particularly extended-release forms due to their improved tolerability for iron deficiency.

CONCLUSIONS

Proper adherence and persistence with iron supplementation may prevent or reduce the risk of complications of iron deficiency and IDA.

Predictors of Extended Length of Hospital Stay Following Surgical Repair of Congenital Heart Diseases

The purpose of this study is to evaluate post-operative length of stay (LOS) following surgical repair of congenital heart defects (CHD) and to investigate baseline pre-operative factors and predictors of post-operative LOS (pLOS). Retrospective chart review of all cases of corrective surgery for CHD performed at the Pediatric Cardiology Unit, King Abdulaziz University Hospital, Jeddah during January 2013-December 2016. Baseline demographics, clinical factors, pre-operative, intra-operative, post-operative cardiac and extra-cardiac complications were analyzed as independent factors of pLOS using stepwise linear regression. Kaplan-Meier (KM) survival analysis was used to analyze the correlation of pLOS (in days) with the independent variables and estimate the probability to exceeding a given pLOS. A total 191 patients (52.4% male, 49.7% aged ≤ 1 year) were included with a median [range] LOS = 10 [3, 158] days. Several baseline clinical factors were associated with longer pLOS such as complex CHD types (tetralogy of Fallot, transposition of great arteries, etc.), high-risk RACHS categories and low weight at surgery. Independent risk factors of pLOS included pre-operative hemoglobin level (unstandardized regression coefficient: B = 2.96, p = 0.036) as the only pre-operative predictor of LOS, besides intra-operative complications (B = 11.72, p = 0.009) and posto-perative factors including MV duration (B = 9.39, p < 0.001), diet/feeding problems (B = 10.27, p = 0.001) and drain tube stay (B = 3.82, p = 0.003). KM survival curves confirmed that these factors increased the probability for longer LOS. Post-operative LOS was associated with several baseline and peri-operative factors; however, it was independently predicted by abnormal baseline hemoglobin level, the occurrence of intra-operative complications, besides post-operative feeding problems, chest drain stay, and MV duration.

Acute kidney injury in trauma patients

PURPOSE OF REVIEW

To review epidemiology and pathophysiology of acute kidney injury (AKI) in trauma patients and propose strategies that aim at preventing AKI after trauma.

RECENT FINDINGS

AKI in trauma patients has been reported to be as frequent as 50% with an association to a prolonged length of stay and a raise in mortality. Among the specific risk factors encountered in trauma patients, hemorrhagic shock, rhabdomyolysis severity, age, and comorbidities are independently associated with AKI occurrence. Resuscitation with balanced solutes seems to have beneficial effects on renal outcome compared with NaCl 0.9%, particularly in the context of rhabdomyolysis. However, randomized clinical studies are needed to confirm this signal. Abdominal compartment syndrome (ACS) is rare but has to be diagnosed to initiate a dedicated therapy.

SUMMARY

The high incidence of AKI in trauma patients should lead to early identification of those at risk of AKI to establish a resuscitation strategy that aims at preventing AKI.

Effects of restrictive red blood cell transfusion on the prognoses of adult patients undergoing cardiac surgery: a meta-analysis of randomized controlled trials

PURPOSE

Restrictive red blood cell transfusion strategies remain controversial in patients undergoing cardiac surgery. We performed a meta-analysis to assess the prognostic benefits of restrictive red blood cell transfusion strategies in patients undergoing cardiac surgery.

METHODS

We identified randomized clinical trials through the 9th of December 2017 that investigated a restrictive red blood cell transfusion strategy versus a liberal transfusion strategy in patients undergoing cardiac surgery. Individual patient data from each study were collected. Meta-analyses were performed for the primary and secondary outcomes. The risk of bias was assessed using the Cochrane Risk of Bias Tool. A trial sequential analysis (TSA)-adjusted random-effects model was used to pool the results from the included studies for the primary outcomes.

RESULTS

Seven trials involving a total of 8886 patients were included. The TSA evaluations suggested that this meta-analysis could draw firm negative results, and the data were sufficient. There was no evidence that the risk of 30-day mortality differed between the patients assigned to a restrictive blood cell transfusion strategy and a liberal transfusion strategy (odds ratio (OR) 0.98; 95% confidence interval (CI) 0.77 to 1.24; p = 0.87). Furthermore, the study suggested that the restrictive transfusion strategy was not associated with significant increases in pulmonary morbidity (OR 1.09; 95% CI 0.88 to 1.34; p = 0.44), postoperative infection (OR 1.11; 95% CI 0.95 to 1.3; p = 0.58), acute kidney injury (OR 1.03; 95% CI 0.92 to 1.14; p = 0.71), acute myocardial infarction (OR 1.01; 95% CI 0.80 to 1.27; p = 0.78), or cerebrovascular accidents (OR 0.97; 95% CI 0.72 to 1.30; p = 0.66).

CONCLUSIONS

Our meta-analysis demonstrates that the restrictive red blood cell transfusion strategy was not inferior to the liberal strategy with respect to 30-day mortality, pulmonary morbidity, postoperative infection, cerebrovascular accidents, acute kidney injury, or acute myocardial infarction, and fewer red blood cells were transfused.

Effects of restrictive red blood cell transfusion on the prognoses of adult patients undergoing cardiac surgery: a meta-analysis of randomized controlled trials

PURPOSE

Restrictive red blood cell transfusion strategies remain controversial in patients undergoing cardiac surgery. We performed a meta-analysis to assess the prognostic benefits of restrictive red blood cell transfusion strategies in patients undergoing cardiac surgery.

METHODS

We identified randomized clinical trials through the 9th of December 2017 that investigated a restrictive red blood cell transfusion strategy versus a liberal transfusion strategy in patients undergoing cardiac surgery. Individual patient data from each study were collected. Meta-analyses were performed for the primary and secondary outcomes. The risk of bias was assessed using the Cochrane Risk of Bias Tool. A trial sequential analysis (TSA)-adjusted random-effects model was used to pool the results from the included studies for the primary outcomes.

RESULTS

Seven trials involving a total of 8886 patients were included. The TSA evaluations suggested that this meta-analysis could draw firm negative results, and the data were sufficient. There was no evidence that the risk of 30-day mortality differed between the patients assigned to a restrictive blood cell transfusion strategy and a liberal transfusion strategy (odds ratio (OR) 0.98; 95% confidence interval (CI) 0.77 to 1.24; p = 0.87). Furthermore, the study suggested that the restrictive transfusion strategy was not associated with significant increases in pulmonary morbidity (OR 1.09; 95% CI 0.88 to 1.34; p = 0.44), postoperative infection (OR 1.11; 95% CI 0.95 to 1.3; p = 0.58), acute kidney injury (OR 1.03; 95% CI 0.92 to 1.14; p = 0.71), acute myocardial infarction (OR 1.01; 95% CI 0.80 to 1.27; p = 0.78), or cerebrovascular accidents (OR 0.97; 95% CI 0.72 to 1.30; p = 0.66).

CONCLUSIONS

Our meta-analysis demonstrates that the restrictive red blood cell transfusion strategy was not inferior to the liberal strategy with respect to 30-day mortality, pulmonary morbidity, postoperative infection, cerebrovascular accidents, acute kidney injury, or acute myocardial infarction, and fewer red blood cells were transfused.

Red blood cell antibody-induced anemia causes differential degrees of tissue hypoxia in kidney and brain

Moderate anemia is associated with increased mortality and morbidity, including acute kidney injury (AKI), in surgical patients. A red blood cell (RBC)-specific antibody model was utilized to determine whether moderate subacute anemia could result in tissue hypoxia as a potential mechanism of injury. Cardiovascular and hypoxic cellular responses were measured in transgenic mice capable of expressing hypoxia-inducible factor-1α (HIF-1α)/luciferase activity in vivo. Antibody-mediated anemia was associated with mild intravascular hemolysis (6 h) and splenic RBC sequestration ( day 4), resulting in a nadir hemoglobin concentration of 89 ± 13 g/l on day 4. At this time point, renal tissue oxygen tension (P_tO₂) was decreased in anemic mice relative to controls (13.1 ± 4.3 vs. 20.8 ± 3.7 mmHg, P < 0.001). Renal tissue hypoxia was associated with an increase in HIF/luciferase expression in vivo ( P = 0.04) and a 20-fold relative increase in renal erythropoietin mRNA transcription ( P < 0.001) but no increase in renal blood flow ( P = 0.67). By contrast, brain P_tO₂ was maintained in anemic mice relative to controls (22.7 ± 5.2 vs. 23.4 ± 9.8 mmHg, P = 0.59) in part because of an increase in internal carotid artery blood flow (80%, P < 0.001) and preserved cerebrovascular reactivity. Despite these adaptive changes, an increase in brain HIF-dependent mRNA levels was observed (erythropoietin: P < 0.001; heme oxygenase-1: P = 0.01), providing evidence for subtle cerebral tissue hypoxia in anemic mice. These data demonstrate that moderate subacute anemia causes significant renal tissue hypoxia, whereas adaptive cerebrovascular responses limit the degree of cerebral tissue hypoxia. Further studies are required to assess whether hypoxia is a mechanism for acute kidney injury associated with anemia.