RBC Transfusion Induced ST Segment Variability Following the Norwood Procedure

Factors associated with renal oxygen extraction in mechanically ventilated children after the Norwood operation: insights from high fidelity haemodynamic data

BACKGROUND

Maintaining the adequacy of systemic oxygen delivery is of utmost importance, particularly in critically ill children. Renal oxygen extraction can be utilised as metric of the balance between systemic oxygen delivery and oxygen consumption. The primary aim of this study was to determine what clinical factors are associated with renal oxygen extraction in children after Norwood procedure.

METHODS

Mechanically ventilated children who underwent Norwood procedure from 1 September, 2022 to 1 March, 2023 were identified as these patients had data collected and stored with high fidelity by the T3 software. Data regarding haemodynamic values, fluid balance, and airway pressure were collected and analysed using Bayesian regression to determine the association of the individual metrics with renal oxygen extraction.

RESULTS

A total of 27,270 datapoints were included in the final analyses. The resulting top two models explained had nearly 80% probability of being true and explained over 90% of the variance in renal oxygen extraction. The coefficients for each variable retained in the best were -1.70 for milrinone, -19.05 for epinephrine, 0.129 for mean airway pressure, -0.063 for mean arterial pressure, 0.111 for central venous pressure, 0.093 for arterial saturation, 0.006 for heart rate, -0.025 for respiratory rate, 0.366 for systemic vascular resistance, and -0.032 for systemic blood flow.

CONCLUSION

Increased milrinone, epinephrine, mean arterial pressure, and systemic blood flow were associated with decreased (improved) renal oxygen extraction, while increased mean airway pressure, central venous pressure, arterial saturation, and systemic vascular resistance were associated with increased (worsened) renal oxygen extraction.

Analysis of haemodynamics surrounding blood transfusions after the arterial switch operation: a pilot study utilising real-time telemetry high-frequency data capture

BACKGROUND

Packed red blood cell transfusions occur frequently after congenital heart surgery to augment haemodynamics, with limited understanding of efficacy. The goal of this study was to analyse the hemodynamic response to packed red blood cell transfusions in a single cohort, as "proof-of-concept" utilising high-frequency data capture of real-time telemetry monitoring.

METHODS

Retrospective review of patients after the arterial switch operation receiving packed red blood cell transfusions from 15 July 2020 to 15 July 2021. Hemodynamic parameters were collected from a high-frequency data capture system (SickbayTM) continuously recording vital signs from bedside monitors and analysed in 5-minute intervals up to 6 hours before, 4 hours during, and 6 hours after packed red blood cell transfusions-up to 57,600 vital signs per packed red blood cell transfusions. Variables related to oxygen balance included blood gas co-oximetry, lactate levels, near-infrared spectroscopy, and ventilator settings. Analgesic, sedative, and vasoactive infusions were also collected.

RESULTS

Six patients, at 8.5[IQR:5-22] days old and weighing 3.1[IQR:2.8-3.2]kg, received transfusions following the arterial switch operation. There were 10 packed red blood cell transfusions administered with a median dose of 10[IQR:10-15]mL/kg over 169[IQR:110-190]min; at median post-operative hour 36[IQR:10-40]. Significant increases in systolic and mean arterial blood pressures by 5-12.5% at 3 hours after packed red blood cell transfusions were observed, while renal near-infrared spectroscopy increased by 6.2% post-transfusion. No significant changes in ventilation, vasoactive support, or laboratory values related to oxygen balance were observed.

CONCLUSIONS

Packed red blood cell transfusions given after the arterial switch operation increased arterial blood pressure by 5-12.5% for 3 hours and renal near-infrared spectroscopy by 6.2%. High-frequency data capture systems can be leveraged to provide novel insights into the hemodynamic response to commonly used therapies such as packed red blood cell transfusions after paediatric cardiac surgery.

Risk Assessment of Red Cell Transfusion in Congenital Heart Disease

Background  The storage time of packed red blood cells (pRBC) is an indicator of change in the product's pH, potassium, and lactate levels. Blood–gas analysis is a readily available bedside tool on every intensive care ward to measure these factors prior to application, thus facilitating a calculated decision on a transfusion's quantity and duration.

Our first goal is to assess the impact of storage time on pH, potassium, and lactate levels in pRBC. The influence of those parameters in the transfused children will then be evaluated.

Methods  In this retrospective study, we conducted blood–gas analyses of pRBC units before they were administered over 4 hours to neonates, infants, and children in our pediatric cardiac intensive care ward. All patients underwent regular blood–gas analyses themselves, before and after transfusion.

Results  We observed a highly significant correlation between the storage time of pRBC units and a drop in pH, as well as an increase in potassium and lactate of stored red cells ( p < 0.0001). Median age of recipients with a complete blood–gas dataset was 0.1 (interquartile range [IQR] = 0.0–0.7) years; median pRBC storage duration was 6 (IQR = 5–8) days. Further analyses showed no statistically significant effect on children's blood gases within 4 hours after transfusion, even after stratifying for pRBC storage time ≤7 days and >7 days.

Conclusion  Stored red blood cells show a rapid decrease in pH and increase in potassium and lactate. Slow transfusion of these units had no adverse effects on the recipients' pH, potassium, and lactate levels.

Association of Immediate Postoperative Hemodynamic and Laboratory Values in Predicting Norwood Admission Outcomes

The primary objective of this study was to determine whether or not hemodynamic parameters and laboratory values at the time of admission to the pediatric cardiac intensive care unit after the Norwood operation were associated with a composite outcome of either need for extracorporeal membrane oxygenation or inpatient mortality. This was a single-center retrospective study of infants with functionally univentricular hearts admitted to intensive care after the Norwood procedure from January 2011 to January 2020. Data were obtained at a single point (after a Norwood procedure) and then compared between two subsets of patients based on the presence or not of the composite outcome of interest. In univariate and multiple regression analyses, a series of receiver operator curves were generated to assess the relationship between the variables of interest and the composite outcome. Eight (7.6%) experienced the composite outcome out of a total of 104 patients. Those who experienced the composite endpoint had significantly higher oxygen extraction ratio (0.43 vs. 0.31, p = 0.01), lower systemic blood flow (2.5 L/min versus 3.1 L/min, p = 0.01), and higher systemic vascular resistance (20.2 indexed woods units versus 14.8 indexed woods units, p = 0.01). Those with systemic blood flow of less than 2.5 L/min/m2 had a 17% risk of experiencing the composite endpoint AUC = 0.79. Those with systemic vascular resistance of greater than 19 indexed woods units had a 22% risk of experiencing the composite endpoint AUC 0.80. Systemic blood flow and systemic vascular resistance are independently associated with this composite outcome.

The Acute Effect of Packed Red Blood Cell Transfusion in Mechanically Ventilated Children after the Norwood Operation

Packed red blood cell (PRBC) transfusions are commonly administered in pediatric patients following the Norwood operation. This study was conducted to determine the effect of PRBC transfusions on hemodynamic parameters in pediatric patients with single-ventricle physiology and parallel circulation. A single-center, retrospective chart review was conducted. Pediatric patients admitted to the cardiac intensive care unit after Norwood operation between 2017 and 2018 were identified. Hemodynamic parameters were collected within a four-hour period before and after a PRBC transfusion. Univariate analyses using paired t tests were conducted to compare blood gas values before and after PRBC transfusion. Next, multivariate regression analyses were conducted to model the impact of transfusion volume, change in hemoglobin levels, and change in FiO2 on the change in PaO2 and PaCO2. These analyses included data from 33 eligible patients who received a PRBC transfusion following a Norwood operation. The hemoglobin levels (p < 0.01) and the PaO2/FiO2 ratio (p = 0.04) were significantly increased, while arterial lactate levels (p = 0.03) were significantly decreased following the transfusion. Transfusion for a pre-transfusion hemoglobin of 12.4 g/dL appears to provide greatest reduction in lactate, used as a surrogate marker for systemic oxygen delivery. No significant changes were found in arterial pH, PaO2, and PaCO2. PRBC transfusions following the Norwood operation may be a useful intervention to increase systemic oxygen delivery, improving PaO2/FiO2 ratio and improving serum lactate. The benefits of PRBC transfusions must be weighed against previously identified risks on a patient-specific basis. Further studies are warranted to further delineate the effects of such transfusions in this population.