What factors are associated with hyperlactatemia after cardiac surgery characterized by well-maintained oxygen delivery and a normal postoperative course? A retrospective study

Nomogram Models to Predict Postoperative Hyperlactatemia in Patients Undergoing Elective Cardiac Surgery

Objectives: Postoperative hyperlactatemia (POHL) is common in patients undergoing cardiac surgery and is associated with poor outcomes. The purpose of this study was to develop and validate two predictive models for POHL in patients undergoing elective cardiac surgery (ECS).

Methods: We conducted a multicenter retrospective study enrolling 13,454 adult patients who underwent ECS. All patients involved in the analysis were randomly assigned to a training set and a validation set. Univariate and multivariate analyses were performed to identify risk factors for POHL in the training cohort. Based on these independent predictors, the nomograms were constructed to predict the probability of POHL and were validated in the validation cohort.

Results: A total of 1,430 patients (10.6%) developed POHL after ECS. Age, preoperative left ventricular ejection fraction, renal insufficiency, cardiac surgery history, intraoperative red blood cell transfusion, and cardiopulmonary bypass time were independent predictors and were used to construct a full nomogram. The second nomogram was constructed comprising only the preoperative factors. Both models showed good predictive ability, calibration, and clinical utility. According to the predicted probabilities, four risk groups were defined as very low risk (<0.05), low risk (0.05–0.1), medium risk (0.1–0.3), and high risk groups (>0.3), corresponding to scores of ≤ 180 points, 181–202 points, 203–239 points, and >239 points on the full nomogram, respectively.

Conclusions: We developed and validated two nomogram models to predict POHL in patients undergoing ECS. The nomograms may have clinical utility in risk estimation, risk stratification, and targeted interventions.

Development and validation of a nomogram model for early postoperative hyperlactatemia in patients undergoing cardiac surgery

Background

Postoperative hyperlactatemia (POHL) is common in patients undergoing cardiac surgery, associated with adverse outcomes. The aim of this study was to identify predictors for POHL after cardiac surgery and to develop and validate a predictive model.

Methods

Adult patients who underwent open heart surgery at our institution between 2016 and 2019 were retrospectively included. The patients were randomly divided into training and validation groups at a 2:1 ratio. Multivariate logistic regression was performed to identify independent predictors for POHL in the training set. A nomogram was then constructed and was validated in the validation set.

Results

POHL developed in 713 of the 5,323 patients (13.4%). The mortality rate was higher in patients with POHL compared with patients without that (9.5% vs. 2.1%, P<0.001). Age, white blood cell (WBC) count, left ventricular ejection fraction, renal insufficiency, cardiac surgery history, red blood cell (RBC) transfusion, and cardiopulmonary bypass (CPB) time were identified as independent risk factors. The nomogram based on these predictors indicated good discrimination in both the training (c-index: 0.787) and validation (c-index: 0.820) sets. The calibration was reasonable by both visual inspection and goodness-of-fit test. The decision and clinical impact curves demonstrated good clinical utility.

Conclusions

We identified 7 independent risk factors and derived a prediction model for POHL in patients undergoing cardiac surgery. The model may contribute significantly to early risk assessment and clinical intervention.

Risk factors and in-hospital mortality of postoperative hyperlactatemia in patients after acute type A aortic dissection surgery

Background

Hyperlactatemia may be caused by increased production due to tissue hypoxia or non-hypoxia. The aim of this study was first to identify risk factors for postoperative hyperlactatemia (POHL) after Stanford type A acute aortic dissection surgery (AADS) and construct a predictive model, and second to evaluate the impact of POHL on prognosis.

Methods

This retrospective study involved patients undergoing AADS from January 2016 to December 2019 in Wuhan Union Hospital. Multivariate logistic regression analysis was performed to identify independent risk factors for POHL. A nomogram predicting POHL was established based on these factors and was validated in the original dataset. The receiver operating characteristic curve was drawn to assess the ability of postoperative lactate levels to predict the in-hospital mortality.

Results

A total of 188 patients developed POHL after AADS (38.6%). Male gender, surgery history, red blood cell transfusion and cardiopulmonary bypass time were identified as independent predictors. The C-index of the prediction model for POHL was 0.72, indicating reasonable discrimination. The model was well calibrated by visual inspection and goodness-of-fit test (Hosmer–Lemeshow χ² = 10.25, P = 0.25). Decision and clinical impact curves of the model showed good clinical utility. The overall in-hospital mortality rate was 10.1%. Postoperative lactate levels showed a moderate predictive power for postoperative in-hospital mortality (C-index: 0.72).

Conclusion

We developed and validated a prediction model for POHL in patients undergoing AADS, which may have clinical utility in personal risk evaluation and preventive interventions. The POHL could be a good predictor for in-hospital mortality.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-021-02244-7.

Hyperlactatemia of dialysis-dependent patients after cardiac surgery impacts on in-hospital mortality: a two-center retrospective study

Background

Lactate is a well-known marker to estimate prognosis after cardiac surgery and critically ill patients. The liver and kidney have a major role in lactate metabolism; however, there was less characterized about the change of lactate and threshold to predict in-hospital mortality in dialysis-dependent patients undertaking cardiac surgery. We conducted this retrospective observational study to characterize when and how lactate values after cardiac surgery affected in-hospital mortality.

Methods

This two-center retrospective study included dialysis-dependent patients who underwent cardiac surgery with a cardiopulmonary bypass from January 2014 to December 2018. Lactate values were collected at three points: at ICU admission (T1), the maximum level of lactate within 24 h postoperatively (T2), and 24 h after ICU admission (T3). We determined hyperlactatemia as more than 2 mmol/L following previous studies.

Results

We enrolled 122 dialysis-dependent patients. The mean age was 73 ± 8 years and hyperlactatemia was observed in 100 patients (81.9%). In-hospital mortality was 11.4%. Univariate analysis and area under curve in ROC suggested that T2 lactate was the most significantly associated with in-hospital mortality (AUC = 0.845). Multivariate logistic analysis showed a significant association between in-hospital mortality when patients showed early peak lactate levels of > 4.5 mmol/L after ICU admission (adjusted OR 8.35; 95% CI: 1.44–57.13).

Conclusions

In dialysis-dependent patients after cardiac surgery, the early-onset of a maximum arterial lactate concentration of > 4.5 mmol/L was significantly associated with in-hospital mortality.

Base excess is superior to lactate-levels in prediction of ICU mortality after cardiac surgery

Introduction

Cardiac surgery with the use of cardiopulmonary bypass is known to induce distinct metabolic changes. Respective changes in acid-base status including increased systemic lactate levels were previously related to clinical outcomes, but data remain controversial. Therefore, we aim to investigate the relevance of lactate and base excess (BE) levels on ICU-mortality in patients admitted to the ICU after cardiac surgery.

Materials and methods

Perioperative data of patients treated in a tertiary care academic center admitted to the ICU after on-pump surgery were analyzed in a retrospective fashion. Receiver operation characteristic (ROC) curves were constructed for admission lactate-levels and BE with calculation of optimal cut-off values to predict ICU mortality. Univariate followed by multivariate regression models were constructed to identify potential outcome-relevant indices.

Results

Data from 1,058 patients were included in the analysis. Area under the curves for prediction of ICU mortality were 0.79 for lactate levels at ICU admission (sensitivity 61.9%/ specificity 87.5%; optimal cut-off level 3.9mmol/l), and 0.7 for BE (sensitivity 52.4%/ specificity 93.8%, optimal cut-off level -6.7), respectively. Multivariate regression identified BE < -6.7 as the single metabolic predictor of ICU-mortality (HR 4.78, 95%-CI 1.4–16.33, p = 0.01). Explorative subgroup analyses revealed that the combination of lactate ≤3.9mmol/l and BE ≤ -6.7 has stronger impact on mortality than a combination of lactate of >3.9mmol/l and BE > -6.7 (HR 2.56, 95%-CI 0.18–37.17).

Conclusions

At ICU-admission, severely reduced BE appears superior to hyperlactatemia with regard to prediction of ICU-mortality in patients after cardiac surgery.

Factors affecting on serum lactate after cardiac surgery

BACKGROUND

The relation between elevated blood lactate level and mortality and morbidity rates after coronary bypass surgery is a proven subject. One of the factors that seems to affect directly the blood lactate level is the storage duration of packed red blood cells.

OBJECTIVES

This study aimed to evaluate the effect of storage duration of transfused blood on serum lactate during cardiac surgery and up to 24 hours after that in the ICU.

PATIENTS AND METHODS

In a cross-sectional study, 228 patients referred to three hospitals of Mashhad University of Medical Sciences for open cardiac surgery, was enrolled using systematic random sampling method. Immediately after accessing arterial line, the first sample of arterial blood gas (ABG) was obtained. For evaluation of lactate levels, the next samples were obtained at the end of surgery and after 24 hours of staying ICU.

RESULTS

Among 5 factors which affected lactate level during surgery, diabetes and higher ejection fraction (EF) reduced changes of the lactate level. On the other hand, the number of infused blood units, duration of on-pump time, and the mean storage duration of blood units were associated with elevated serum lactate during surgery. A significant relationship was found between blood storage duration and serum lactate levels 24 hours after surgery.

CONCLUSIONS

Comparing the serum lactate level before operation and 24 hours after the operation showed that the number of received blood units had a significant effect on serum lactate. We found no significant effect for blood storage duration; however, the number of given blood units was more significant.

Changes in myocardial lactate, pyruvate and lactate-pyruvate ratio during cardiopulmonary bypass for elective adult cardiac surgery: Early indicator of morbidity

BACKGROUND

Myocardial lactate assays have been established as a standard method to compare various myocardial protection strategies. This study was designed to test whether coronary sinus (CS) lactates, pyruvate and lactate-pyruvate (LP) ratio correlates with myocardial dysfunction and predict postoperative outcomes.

MATERIALS AND METHODS

This prospective observational study was conducted on 40 adult patients undergoing elective cardiac surgery with the aid of cardiopulmonary bypass (CPB). CS blood sampling was done for estimation of myocardial lactate (ML), pyruvate (MP) and lactate-pyruvate ratio (MLPR) namely: pre-CPB (T(1)), after removal of aortic cross clamp (T(2)) and 30 minutes post-CPB (T(3)).

RESULTS

Baseline myocardial LPR strongly correlated with Troponin-I at T1 (σ: 0.6). Patients were sub grouped according to the median value of myocardial lactate (2.9) at baseline T1 into low myocardial lactate (LML) group, mean (2.39±0.4 mmol/l), n=19 and a high myocardial lactate (HML) group, mean (3.65±0.9 mmol/l), n = 21. A significant increase in PL, ML, MLPR and TropI occurred in both groups as compared to baseline. Patients in HML group had significant longer period of ICU stay. Patients with higher inotrope score had significantly higher ML (T2, T3). ML with a baseline value of 2.9 mmol/l had 70.83% sensitivity and 62.5% specificity (ROC area: 0.7109 Std error: 0.09) while myocardial pyruvate with a baseline value of 0.07 mmol/l has 79.17% sensitivity and 68.75% specificity (ROC area: 0.7852, Std error: 0.0765) for predicting inotrope requirement after CPB.

CONCLUSION

CS lactate, pyruvate and LP ratio correlate with myocardial function and can predict postoperative outcome.

Lactate clearance time and concentration linked to morbidity and death in cardiac surgical patients

BACKGROUND

Early predictors of morbidity after cardiac operations are lacking. Elevated lactate concentrations in the immediate postoperative period reflect unmet metabolic demand and may be associated with outcome. This study examined the association between early plasma lactate concentrations and outcome after cardiac operations.

METHODS

As a retrospective cohort investigation, patient information was obtained from the Cardiovascular Information and the Anesthesiology Institute's patient registries. Inclusion criteria were all adult cardiac surgical patients undergoing isolated coronary artery bypass grafting or valve procedures, or coronary artery bypass grafting with a valve procedure, from January 1, 2008, to August 7, 2008 (arterial lactate values were added to the patient registry beginning January 1, 2008).

RESULTS

Lactate concentrations during the initial 12 postoperative hours of a patient's stay in the cardiovascular intensive care unit were averaged (mean lactate concentration), and linear regression concentrations over time were used to predict when the lactate concentration would reach 1.5 mmol/L in individual patients (predicted lactate clearance time). We also considered the product of the mean and clearance (product value). Predicted lactate clearance time, mean lactate concentration, and product value were associated with any type of reoperation, death, and a set of composite outcomes (p < 0.001 for each). The accuracy of these indices was moderate to good, with the highest C statistic (for product value) being 0.82.

CONCLUSIONS

Predicted lactate clearance time, mean lactate concentration, and product value are each associated with death, any type of reoperation, and a set of composite outcomes in patients undergoing coronary artery bypass grafting or valve operations, or both. Product value provided the best early prognostic guidance in individual patients.

A bootstrap approach for assessing the uncertainty of outcome probabilities when using a scoring system

Background

Scoring systems are a very attractive family of clinical predictive models, because the patient score can be calculated without using any data processing system. Their weakness lies in the difficulty of associating a reliable prognostic probability with each score. In this study a bootstrap approach for estimating confidence intervals of outcome probabilities is described and applied to design and optimize the performance of a scoring system for morbidity in intensive care units after heart surgery.

Methods

The bias-corrected and accelerated bootstrap method was used to estimate the 95% confidence intervals of outcome probabilities associated with a scoring system. These confidence intervals were calculated for each score and each step of the scoring-system design by means of one thousand bootstrapped samples. 1090 consecutive adult patients who underwent coronary artery bypass graft were assigned at random to two groups of equal size, so as to define random training and testing sets with equal percentage morbidities. A collection of 78 preoperative, intraoperative and postoperative variables were considered as likely morbidity predictors.

Results

Several competing scoring systems were compared on the basis of discrimination, generalization and uncertainty associated with the prognostic probabilities. The results showed that confidence intervals corresponding to different scores often overlapped, making it convenient to unite and thus reduce the score classes. After uniting two adjacent classes, a model with six score groups not only gave a satisfactory trade-off between discrimination and generalization, but also enabled patients to be allocated to classes, most of which were characterized by well separated confidence intervals of prognostic probabilities.

Conclusions

Scoring systems are often designed solely on the basis of discrimination and generalization characteristics, to the detriment of prediction of a trustworthy outcome probability. The present example demonstrates that using a bootstrap method for the estimation of outcome-probability confidence intervals provides useful additional information about score-class statistics, guiding physicians towards the most convenient model for predicting morbidity outcomes in their clinical context.

Type B lactic acidosis and insulin-resistant hyperglycemia in an adolescent following cardiac surgery

OBJECTIVE

To report the presence of type B lactic acidosis and insulin-resistant hyperglycemia following cardiopulmonary bypass in a pediatric patient.

DESIGN

Case report.

SETTING

Tertiary referral children's hospital pediatric intensive care unit.

PATIENT

Fourteen-year-old child with hyperlactatemia and hyperglycemia following cardiac surgery.

INTERVENTIONS AND RESULTS

We report a patient who following cardiopulmonary bypass for repair of his congenital heart disease developed type B lactic acidosis and hyperglycemia resistant to insulin therapy. Resolution of his hyperlactatemia and hyperglycemia occurred approximately 24 hrs postoperatively without apparent ill effect.

CONCLUSIONS

Type B lactic acidosis is a phenomenon that may occur in the pediatric population in conjunction with insulin-resistant hyperglycemia. We observed that its resolution corresponded to improvement in the patient's hyperglycemia.

Too much lactate or too little liver?

We describe a 67-year-old woman with cholangiocarcinoma who was scheduled for cholecystectomy, trisegmentectomy, bile duct resection, and regional lymphadenectomy. Her case was complicated by hyperlactatemia, sepsis, and multiorgan failure. The discussion reviews the possible causes of the hyperlactatemia and reviews measures that could be used to reduce this risk.

Clinical review: splanchnic ischaemia

Inadequate splanchnic perfusion is associated with increased morbidity and mortality, particularly if liver dysfunction coexists. Heart failure, increased intra-abdominal pressure, haemodialysis and the presence of obstructive sleep apnoea are among the multiple clinical conditions that are associated with impaired splanchnic perfusion in critically ill patients. Total liver blood flow is believed to be relatively protected when gut blood flow decreases, because hepatic arterial flow increases when portal venous flow decreases (the hepatic arterial buffer response [HABR]). However, there is evidence that the HABR is diminished or even abolished during endotoxaemia and when gut blood flow becomes very low. Unfortunately, no drugs are yet available that increase total hepato-splanchnic blood flow selectively and to a clinically relevant extent. The present review discusses old and new concepts of splanchnic vasoregulation from both experimental and clinical viewpoints. Recently published trials in this field are discussed.