2019

Modified Lung Ultrasound Examinations in Assessment and Monitoring of Positive End-Expiratory Pressure-Induced Lung Reaeration in Young Children With Congenital Heart Disease Under General Anesthesia.

Wu L, Hou Q, Bai J, Zhang J, Sun L, Tan R, Zhang M, Zheng J. Pediatr Crit Care Med. 2019 May;20(5):442-449. doi: 10.1097/PCC.0000000000001865. PMID:  31058784 Similar articles   Take Home Points: The most prevalent region of post-intubation atelectasis in pediatric patients (3 months to 3 years old) undergoing pediatric cardiac surgery under general anesthesia is the posterior inferior region of the lung. Lung ultrasound (LUS) along the posterior axillary line at the intercostal fifth, sixth, and seventh spaces showed an incidence of atelectasis of 60-62.5%, 57.5-60% and 37.5% respectively, whereas LUS in the anterior or lateral regions rarely presented atelectasis (0-7.5%). Post-intubation addition of 5 cm H2O positive end-expiratory pressure (PEEP) in pressure-controlled ventilated pediatric patients under general anesthesia significantly reduced the incidence of atelectasis in high prevalence areas of the lung (posterior and inferior). This simple beneficial intervention can improve lung aeration and decreases the incidence of postoperative atelectasis. In addition, this low level PEEP was not associated with hemodynamic compromise in pediatric cardiac patients.   Commentary by Pablo Motta, MD a pediatric cardiac anesthesiologist at Texas Children’s Hospital in Houston Texas / Baylor College of Medicine:  Lung ultrasound (LUS) is a radiation-free tool used to diagnose pulmonary disease in the perioperative setting. Common diagnoses identified by LUS include pulmonary edema, atelectasis, pneumothorax and effusion. LUS has become a preferred alternative to CT in terms of accuracy and reliability and outperforms chest radiography in the critical care setting. Atelectasis is one of the most common complications in pediatric patients undergoing general anesthesia either with an endotracheal tube or laryngeal mask, with an incidence of 68 –100%. Atelectasis compromises gas exchange, worsens lung mechanics and increases the risk of lung inflammation. Usually the effect of atelectasis is self-limited in otherwise healthy pediatric patients but can hinder the recovery of pediatric cardiac surgery patients. Furthermore, this group of patients is at an even higher risk of atelectasis due to surgical manipulation and lung collapse during cardiopulmonary bypass (CPB). Lung recruitment maneuvers have been described in the adult cardiac surgery population but there is little evidence in the pediatric cardiac surgical population.   In this single institution randomized control trial, the authors prospectively studied pediatric congenital heart disease (CHD) patients between the ages of 3 months to 3 years old scheduled for elective cardiac surgery with CPB under general anesthesia. Patients undergoing emergency surgery or who had a previous respiratory infection, pulmonary disease, genetic disorders, thoracic cage anomalies or abnormal lung imaging were excluded. The goals of the study were to: first, define the most useful lung region/s to diagnose atelectasis by LUS; second, compare the effects of pressure-controlled ventilation with and without low-level PEEP on lung aeration.   Forty patients were randomly allocated to either a control or intervention group.  The control group was placed on 0 cm H2O PEEP while the intervention group was placed on 5 cm H2O PEEP just after intubation.  Both groups had a LUS examination performed by the same experienced anesthesiologist 1-minute and 15-minutes post-intubation following induction of general anesthesia. Six areas of the lung were examined bilaterally for a total of twelve scanned areas: anteriorly at clavicular midline region (scans 1 and 2), laterally at the middle axillary catheter region (scan 3), posteriorly at the posterior axillary line at the fifth, sixth, and seventh intercostal spaces (scans 4–6).  The ventilation management was the same pressure control ventilation (PCV) with a peak inspiratory pressure to achieve a tidal volume of 8–10 mL/kg and an end-tidal CO2 of 35–45 mm Hg. The frequency was set at a rate of 16–30 breaths/min depending on the patient’s age and the inspiratory: expiratory ratio of 1:2. Furthermore the intervention group was maintained on 5 cm H2O PEEP after intubation until the second LUS.   The results were as predicted, with the most prevalent area for atelectasis being inferoposterior (Scans 4-6) with an incidence between 37.5 to 62.5%. Almost no atelectasis was visualized in the anterior and lateral regions of the lung. The addition of low-level PEEP of 5 cm H20 decreased the incidence of atelectasis in scans 4, 5, and 6 from 62.5% to 45% (p = 0.02), 60% to 27.5% (p = 0.002), and 35% to 20% (p = 0.035), respectively. No deleterious hemodynamic effects were seen with the level of PEEP used, but atelectasis persisted in a substantial group of patients (~30%). In addition. the authors calculated a lung aeration score and the atelectatic area. PCV with PEEP significantly reduced lung aeration scores from 13 (8.3-17.5) to 8 (3.3-9.8) and the atelectatic areas bilaterally from 128 mm2 (34.5–213.3 mm2) to 49.5 mm2 (5.3–75.5 mm2).   Research shortcomings include being a single center study with a small sample size and having a single non-blinded anesthesiologist interpreting the images with its potential bias. The study population was not homogenous since it had wide age variation (3 month to 3 years), with the consequent size difference, and a mix of CHD (cyanotic and acyanotic). The intervention was brief (only 15 minutes of PEEP) leaving a substantial group of patients with persistent atelectasis (~30%). This poses the question whether higher levels of PEEP are necessary to completely eliminate atelectasis or if low-level PEEP for a longer period of time could resolve it.   Interestingly the study opens up the question if LUS should become a standard of care in the pediatric cardiac operating room to allow early diagnosis of atelectasis. Ultimately, this demands further investigations to determine the optimal level of PEEP required to completely resolve atelectasis without causing hemodynamic compromise.                          Viviane Nasr (Boston) and Rania Abbasi (Indianapolis) – Section Editors

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Positive Airway Pressure Versus High-Flow Nasal Cannula for Prevention of Extubation Failure in Infants After Congenital Heart Surgery.

Richter RP, Alten JA, King RW, Gans AD, Rahman AF, Kalra Y, Borasino S. Pediatr Crit Care Med. 2019 Feb;20(2):149-157. doi: 10.1097/PCC.0000000000001783. PMID:  30407954 Similar articles   Take Home Points: Prevention of post-extubation failure after congenital cardiac surgery in neonates and infants should be a high priority as it is associated with significant morbidity and mortality. The optimal strategy for mitigating post-extubation failure [high flow nasal cannula (HFNC) versus non-invasive positive airway pressure (PAP)ventilation] is not well established. In this retrospective, single institution, propensity score matched cohort study comparing extubation to HFNC versus PAP, there was no difference in post-extubation failure rates. However, extubation to PAP was associated with greater resource utilization, longer times to transition to low-flow nasal cannula and then room air, and longer postsurgical hospital stay.   Commentary from Dr. Sana Ullah, a pediatric cardiac anesthesiologist at UT Southwestern Medical Center in Dallas, Texas:  Extubation failure rate is around 6-9% for children and around 17% for neonates after cardiac surgery, and is associated with increased morbidity and mortality. There is no consensus or evidence-based optimal strategy for preventing extubation failure in this setting. Typically, patients are extubated to nasal cannula (high flow nasal cannula, HFNC, low-flow nasal cannula, LFNC), or some form of non-invasive ventilation (NIV), such as nasal CPAP with or without pressure support. The exact modality is based on clinician choice, with the NIV method being perceived as providing more support for higher risk patients. There is very little prospective evidence-based data to help decision-making. In this single-institution, retrospective, matched cohort study, the authors describe the impact of post-extubation respiratory support on patient outcomes and resource utilization. Patients under 6 months of age admitted to the cardiac  intensive care unit (ICU) at Children’s of Alabama hospital after cardiac surgery using cardiopulmonary bypass were included, with those requiring pre-operative tracheostomy, post-operative extracorporeal membrane oxygenation (ECMO),  limited life-sustaining therapy, and/or post-operative death prior to extubation being excluded. The respiratory modalities were as follows: Positive airway pressure (PAP) included CPAP with or without pressure support or BiPAP. HFNC oxygen support was given at 3 L/min or greater. LFNC was defined as less than 2 L/min of oxygen.  The choice of support was at the discretion of the ICU attending. HFNC was started at 3-6 L/min for neonates and 3-8 L/min for infants, increasing to 8 L/min for neonates and 12 l/min for infants before declaring failure. PAP was initiated with BiPAP, starting with an inspired (iPAP) of 20 cmH2O, expiratory PAP (ePAP) of 10 cmH2O and a rate of 20-30. This was increased to iPAP of 25, ePAP of 15, and rate of 30 before declaring failure. The FiO2 was titrated for all modalities as deemed appropriate by the ICU clinician. Treatment failure was determined by clinical signs (tachypnea, grunting, accessory muscle use, irritability) and evidence of low cardiac output (declining renal NIRS, increasing arteriovenous oxygen and/or CO2 gradient, and/or increasing serum lactate). There was no set protocol for weaning support. HFNC was typically weaned by the bedside nurse, and PAP was weaned based on respiratory assessment by the respiratory therapist and the clinician according to clinical progression. PAP was generally weaned in a step-wise fashion from BiPAP to CPAP, then to HFNC. Extubation failure was defined as need for reintubation within 48 hours of extubation. The results are interesting: Out of 245 patients, overall extubation failure rate was 12%, and in the matched cohort, there was no significant difference between the HFNC and PAP groups. Fifteen of the HFNC patients (31%) required rescue PAP at a median of 10 hours after extubation. Three of the patients who received rescue PAP failed extubation at a median of 28 hours. The PAP group (not surprisingly) took longer to wean to both LFNC and then room air, and feeding was delayed by almost 4 days. Perhaps because of this, the PAP group also had a higher rate of G-tube insertions for feeding. There was also increased post-surgical hospital length of stay. And not surprisingly, the PAP group had greater resource utilization in terms of equipment, personnel, lab draws, and sedation. A major problem with studies like this is selection bias for a particular treatment. In this study, there would be clear selection bias towards clinicians choosing PAP technique in patients they perceived to be at a higher risk of extubation failure. To reduce this bias, the investigators used propensity scores to generate 49 matched pairs where there was no significant difference in patient demographics or treatment factors between the two groups. Based on this study, despite using propensity scores to minimize selection bias, it suggests that extubating to PAP ventilation using non-invasive techniques may be disadvantageous compared with the much simpler HFNC. However, the decision to select a particular strategy for respiratory support after extubation is quite complex. There are objective parameters such as the respiratory and hemodynamic data, but more so, there are many subjective criteria that the ICU clinician will consider in deciding the optimal support strategy. These include the post-surgical progress and the perceived clinical trajectory of the patient, age and complexity of the operation, possible complications that may have an impact on respiratory function such as vocal cord or diaphragm paresis, sedative and analgesic medications, the time of day as far as weaning support (aggressive weaning may be avoided at night), variability between clinicians, and the paucity of objective criteria on when exactly to intervene when extubation is deemed a failure. Once a more aggressive strategy is begun (i.e. PAP), there is a natural tendency to progress more cautiously as far as weaning support. Extubation failure and subsequent reintubation is associated with more complications, and so there is a strong desire to avoid the “one step forward, two steps back” scenario. Ultimately, until more prospective data becomes available, the choice of post-extubation respiratory support strategy will depend mostly on the bedside clinician taking into account the myriad of patient factors that will have an impact on the eventual success or failure of that strategy.                           Viviane Nasr (Boston) and Rania Abbasi (Indianapolis) – Section Editors

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Near-infrared spectroscopy for prediction of extubation success after neonatal cardiac surgery.

Gradidge EA, Grimaldi LM, Cashen K, Gowda KMN, Piggott KD, Wilhelm M, Costello JM, Mastropietro CW. Cardiol Young. 2019 Jun;29(6):787-792. doi: 10.1017/S1047951119000829. Epub 2019 Jun 6. PMID:  1169104 Similar articles   Take Home Points: Extubation failure after neonatal cardiac surgery is high, with more than 1 out of 10 neonates failing extubation. While there is consensus in the literature on the criteria for the need for mechanical ventilation in the critically ill neonate, there is no consensus on the criteria for weaning from mechanical ventilation and extubation readiness of neonates. A secondary analysis on previously collected multi-center prospective observational data in neonates after cardiac surgery evaluated NIRS as a parameter to predict extubation success. An increase in cerebral NIRS of ≥ 5% from baseline at the time of extubation was 98% predictive of extubation success. However, this change was present in only half of the neonates successfully extubated, indicating a low negative predictive value. Changes in renal regional oximetry were not prognostic of extubation outcome.   Commentary from Olga Pawelek, M.D. and Nischal Gautam, M.D., pediatric cardiac anesthesiologists at the McGovern Medical School/ Children’s Memorial Hermann, Houston, Texas:  Over the past decade, great strides have been made in the perioperative care of neonates undergoing cardiac surgery to decrease mortality2. Despite this success, failure to extubate after neonatal cardiac surgery remains a significant complication and is reported anywhere between 6-21%3. Extubation failure and prolonged mechanical ventilation impact hospital length of stay and are associated with increased morbidity and mortality. Both modifiable and non-modifiable risk factors, such as hypoxic insults from birth or during surgery, genetic abnormalities, age, weight, and anatomic variants, heavily influence postoperative outcomes such as extubation success and the need for prolonged intensive care 2. These factors along with the high extubation failure rate after neonatal cardiac surgery suggest that a prognostic factor is needed to help determine the timing or readiness for tracheal extubation. Various measures, including neuromuscular function, oxygenation, and ventilation indices, have been examined as potential extubation readiness tools, however they have not been proven reliable. Gradidge et al.’s results stem from a secondary analysis of prospectively collected cross-sectional data on neonates who underwent cardiac surgery at seven US tertiary children’s hospitals over one year (2015). Baseline or pre-incision cerebral and renal oximetry values using the INVOS oximeter probes were compared to another set in the intensive care unit at a time closest to extubation. Since the analysis was observational, there was not a consistent extubation protocol. Extubation failure was defined as a need for unplanned reintubation within 72 hours of planned extubation.   In this cohort of 159 patients, extubation failure after neonatal cardiac surgery was reported at 9.4%, which is similar to other studies 4. Baseline oximetry values and patient characteristics such as age, weight, duration of cardiopulmonary bypass and cross-clamp times had no impact on extubation outcomes. At the time of extubation, both cerebral and renal oximetry values were higher than baseline in patients extubated successfully and lower than baseline in patients who failed extubation.  An increase in cerebral NIRS of ≥ 5% from baseline at the time of extubation was found to be predictive of extubation success. While this was 92% specific, with a 98% positive predictive value of extubation success, it was only 50% sensitive.  After adjusting for variables, this ≥5% change was independently associated with extubation success (odds ratio of 10.9).  By contrast, an increase in renal NIRS was a poor predictor of extubation success.   What does this mean for us? Staged weaning from mechanical ventilation consists of measuring the potential cushion in the cardiopulmonary reserves to accommodate for the increased oxygen consumption from the work of spontaneous ventilation. In neonates tottering on the margins of critical oxygen delivery when oxygen extraction is at its maximum, especially in the heavily auto-regulated areas of the brain, it is not unusual for the mixed venous oxygen saturation to be lower at the time of extubation. Once the noxious stimulus of the endotracheal tube is removed and considering adequate pain control, it should be expected that the oxygen consumption and extraction decrease and the oxygen supply/consumption ratio is restored above anaerobic or critical levels. Given these assumptions, should a change in regional oximetry from baseline at the time of extubation be predictive of extubation success? The authors confirm that extubation failure after cardiac surgery is indeed high, and that 1 in 10 neonates will fail extubation after cardiac surgery. One of the significant takeaways from Gradidge et al. study is that there potentially exists a feel-good factor for extubation success when a ≥ 5% positive change in cerebral oximetry is observed at the time of extubation. This positive change metric was 98% predictive in determining extubation success. This high level of specificity could add another parameter to the checklist for extubation readiness. However, some major limitations need to be addressed before we consider this metric as a tool for extubation. In this study, more than 50% of the neonates were extubated successfully even when this magnitude of change in oximetry was not present.  Why did the metric fail to predict extubation in these patients?  Similarly, why was the negative predictive value low for this metric? There could be many reasons for these observations. The data analysis was based on a prospective observational study and had many limitations based on the accuracy of the NIRS technology, especially during states of agitation and wakefulness.  The secondary analysis was not adequately powered for this outcome.  The retrospective nature of the study could have led to convenience-based sampling bias. There was no standardized extubation protocol or a re-intubation protocol across the seven centers. This lack of standardization of the weaning process could lead to significant differences in patient management across the centers and therefore result in variable outcomes. Lastly, the authors compare baseline values, when neonates were intubated, deeply sedated, well-oxygenated/ventilated, to values at the time of extubation, when neonates were nearly awake or agitated. In the postoperative period after neonatal cardiac surgery, the cerebral metabolic oxygen consumption rate is increased and can last many days. It is possible that the brain auto-regulates by increasing cerebral oxygen extraction, therefore expected increases in cerebral regional oximetry may not occur even if corrective surgeries increase systemic oxygen saturation. To validate this, a recently published prospective observational study5 analyzed oximetry changes after the correction of cyanotic congenital heart disease. Wong et al., observed that although the systemic oxygen saturation increased significantly to near normal values after correction of cyanotic heart disease, the cerebral and renal oximetry values did not increase but rather decreased compared to baseline at the time of discharge. In conclusion, cerebral NIRS monitoring and change from baseline may be predictive of extubation success and used as one of the factors during assessment of neonates’ readiness to extubate. Future prospective trials powered to study the impact of regional oximetry as a tool for extubation readiness should be encouraged. References: Gradidge EA, Grimaldi LM, Cashen K, Gowda KMN, Piggott KD, Wilhelm M, Costello JM, Mastropietro CW: Near-infrared spectroscopy for prediction of extubation success after neonatal cardiac surgery. Cardiology in the young 2019; 29:787–92 Blinder JJ, Thiagarajan R, Williams K, Nathan M, Mayer J, Kulik TJ: Duration of Mechanical Ventilation and Perioperative Care Quality After Neonatal Cardiac Operations. Ann Thorac Surg 2017; 103:1956–62 Miura S, Hamamoto N, Osaki M, Nakano S, Miyakoshi C: Extubation Failure in Neonates After Cardiac Surgery: Prevalence, Etiology, and Risk Factors. Ann Thorac Surg 2017; 103:1293–8 Mastropietro CW, Cashen K, Grimaldi LM, Narayana Gowda KM, Piggott KD, Wilhelm M, Gradidge E, Moser EAS, Benneyworth BD, Costello JM: Extubation Failure after Neonatal Cardiac Surgery: A Multicenter Analysis. J Pediatr 2017; 182:190–4 Wong JJ-M, Chen CK, Moorakonda RB, Wijeweera O, Tan TYS, Nakao M, Allen JC, Loh TF, Lee JH: Changes in Near-Infrared Spectroscopy After Congenital Cyanotic Heart Surgery. Front Pediatr 2018; 6:97                          Viviane Nasr (Boston) and Rania Abbasi (Indianapolis) – Section Editors

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High-energy nutrition in paediatric cardiac critical care patients: a randomized controlled trial.

Zhang H, Gu Y, Mi Y, Jin Y, Fu W, Latour JM. Nurs Crit Care. 2019 Mar;24(2):97-102. doi: 10.1111/nicc.12400. Epub 2018 Dec 9. PMID:  30548121 Similar articles   Take Home Points: Infants with congenital heart disease are at high risk for malnutrition. The immediate postoperative period can worsen malnutrition and increase mortality in infants and children due to increased energy requirements, inadequate calorie intake, intestinal malabsorption, and fluid restriction. This study was aimed at assessing efficacy and safety of feeding high-energy formula (HF) to infants with congenital heart disease in the early postoperative period after cardiac surgery. The authors found that infants fed HF gained more weight but had higher rates of feeding intolerance. Feeding intolerance was relieved with medication and did not deter feed advancement.   Commentary from Dr. Anne Elisa Cossu, a practicing pediatric cardiac anesthesiologist at Riley Hospital for Children in Indianapolis, IN:  Several clinical studies have been designed to investigate the effects of feeding HF to infants with congenital heart disease (CHD).  The results have shown that HF increases caloric intake, however, there is not clear evidence as to the effect of HF on weight gain and gastrointestinal function.   Studies have suggested a resting energy expenditure of 40-60 kcal/kg/day in CHD patients.  The authors’ aim of the current study was to evaluate safety and efficacy of HF during the early postoperative period after cardiac surgery in infants with CHD. The study was a randomized, controlled trial that divided patients into two groups—an intervention group and a control group.  Inclusion criteria were the following: diagnosis of CHD based on symptoms, ultrasound and imaging; < 1 year of age; and parent agreement to cardiac surgery. Exclusion criteria were the following: diseases that cause nutritional disorders, preoperative gastrointestinal intolerance, use of total parenteral nutrition after surgery, or length of stay in the CICU predicted to be < 5 days. Feeds were begun post-operatively, and patients in the intervention group received HF (51-89 kcal/kg/day) whereas the control group received standard-energy formula (SF) (44-56 kcal/kg/day) for an interval of 7 days. The primary outcome measures were weight gain in grams by the seventh day of feeding and feeding intolerance from the first day to the seventh day after starting enteral feeding. Feeding intolerance was considered to be present when infants had any of the following symptoms: vomiting three or more times per day, abdominal distension (abdominal circumference increased by more than 10%), formula volume decrease or lack of increase for 3 days, gastric residual volume greater than one third of the previous feed, greater than two unscheduled feeding breaks or diarrhea.  Secondary outcomes included the following: prealbumin (mg/L) level within 24 hours of surgery and at 3 and 7 days postop; enteral energy intake during feeding with HF or SF; and duration of mechanical ventilation, CICU length of stay, hospital length of stay and number of participants who developed necrotizing enterocolitis. A total of 59 infants completed the trial (intervention group n=30 and control group n=29).  The two groups did not differ significantly in baseline characteristics. Infants who received HF had less weight loss as compared to the SF group.   The HF group experienced significantly more gastrointestinal intolerance in contrast to the SF group.  Nine infants in the HF group were administered drugs to improve gastrointestinal function versus 6 in the SF group. In terms of secondary outcomes, serum prealbumin levels gradually increased in the HF group but declined in the SF group. Enteral nutrition energy intake of both groups gradually increased, but more rapidly in the HF group.  There were no statistical differences in the other secondary outcomes between the HF and SF groups. Previous studies have established improved clinical outcomes when enteral nutrition is provided in the early postoperative period.  Protocols for early feeding can promote these practices, which was a strength of the current study. Body weight decreased in all study participants, however, began to rebound 4-5 days after intervention due to adequate caloric intake.  The exact dose-response relationship between energy intake and weight gain remains unclear.  Infants in the intervention group (HF) had increased serum albumin levels compared to infants in the control (SF) group who had decreased albumin levels, which may indicate better nutritional status of the infants in the HF group. Limitations of the study included reporting bias in outcome indicators such as abdominal distension, short intervention time of 7 days, and limited time for collecting follow-up data. Additionally, weight gain may not be a reliable indicator of nutritional status as it may only indicate generalized edema. Ultimately, the authors drew the conclusion that HF enteral feeding might increase energy intake, reduce weight loss and improve nutritional status but may also cause gastrointestinal intolerance.  More studies are needed to confirm safety and efficacy of HF.                         Viviane Nasr (Boston) and Rania Abbasi (Indianapolis) – Section Editors

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Correlation Between ROTEM FIBTEM Maximum Clot Firmness and Fibrinogen Levels in Pediatric Cardiac Surgery Patients.

Tirotta CF, Lagueruela RG, Madril D, Salyakina D, Wang W, Taylor T, Ojito J, Kubes K, Lim H, Hannan R, Burke R. Clin Appl Thromb Hemost. 2019 Jan-Dec;25:1076029618816382. doi: 10.1177/1076029618816382. Epub 2018 Dec 5. PMID:  30518238 Free PMC Article Similar articles   Take Home Points: Normal plasma fibrinogen levels as measured by the Clauss method are well defined for pediatric surgical populations, but measurement is not available for point-of-care (POC) testing. The FIBTEM assay of rotational thromboelastometry (ROTEM) is a POC test that provides immediate results for transfusion guidance during pediatric cardiac surgery, but normal values in children have not been widely established. Paired plasma fibrinogen and FIBTEM maximum clot firmness (MCF) levels were used to create an equation to predict plasma fibrinogen concentration for a given MCF, enabling application of POC ROTEM to immediate goal-directed transfusion.   Commentary by Kelly A. Machovec, MD, MPH, Associate Professor of Anesthesiology at Duke University Medical Center:  Rotational thromboelastometry (ROTEM, Instrumentation Laboratory, Bedford, MA, USA) is a viscoelastic test used to monitor bleeding, coagulation and transfusion in the surgical or trauma setting.  The FIBTEM assay of ROTEM assesses the functionality and stability of fibrin polymerization.  The FIBTEM assay is conducted by tissue factor activation of the whole blood sample, followed by addition of cytochalasin D to inhibit the platelet contribution to clot strength, thus isolating the fibrin contribution.  POC ROTEM has been validated against laboratory ROTEM, but ROTEM FIBTEM values have not been validated against plasma fibrinogen concentration as measured by the Clauss method.  The authors of this study aimed to correlate MCF of the FIBTEM with plasma fibrinogen levels by the Clauss method in order to develop an equation to predict plasma fibrinogen levels from FIBTEM MCF results. This single center retrospective chart review examined consecutive patient charts over a 7-month period.  All charts of children 5 years old or less having cardiac surgery with peri-operative fibrinogen and FIBTEM values were included.  Time points of interest were prior to cardiopulmonary bypass (CPB) initiation, during CPB, and post-CPB separation.  Plasma fibrinogen levels were obtained in the laboratory using the Stago STA compact system, which uses a modified Clauss method to determine the fibrinogen concentration of a given blood sample.  The study team reviewed 50 charts, and found 27 patients who had a total of 87 incidences where FIBTEM MCF and plasma fibrinogen levels were obtained at the same time and could therefore be compared. Plasma fibrinogen levels and FIBTEM MCF values were found to be normally distributed by the Kolmogorov-Smirnov test.  Mean plasma fibrinogen was 178.1 mg/dl +/- 76.4.  Mean FIBTEM MCF was 8 mm +/- 4.3.  Linear regression of FIBTEM MCF and plasma fibrinogen showed a positive linear correlation. The authors then moved to the prediction equation.  First, simple linear regression was used to determine if FIBTEM MCF predicts plasma fibrinogen levels.  Then, this information was used to develop a regression equation to predict the plasma fibrinogen level given a FIBTEM MCF value.  Repeated 10-fold cross validation was used to develop, train and test the predictive equation.  The final model suggested the following equation can be used to predict plasma fibrinogen given FIBTEM MCF: Plasma fibrinogenmg/dl = 78.6 + 12.4 (MCFmm)   The finding that plasma fibrinogen level correlates with FIBTEM MCF is consistent with other studies in both pediatric and adult patients.  This study, however, takes this relationship one step further by creating an equation to predict plasma fibrinogen from FIBTEM MCF.  This is clinically important because normal ROTEM values for pediatric populations are not clearly defined, which limits its utility as a POC assay.  In contrast, normal pediatric plasma fibrinogen levels are well defined, but are not readily obtained. The ability to rapidly translate FIBTEM MCF into a plasma fibrinogen level may aid the physician in interpreting this information and making prompt clinical decisions.  Importantly, because the FIBTEM amplitude at 5, 10, and 15 minutes after clotting time correlates with the final MCF, early FIBTEM POC values can be used to support a goal-directed transfusion practice. The authors provide the example of human fibrinogen concentrate: POC ROTEM can be used to estimate plasma fibrinogen level, which can then be used to calculate an accurate dose of human fibrinogen concentrate to raise plasma fibrinogen levels to the desired target level, rather than giving the standard 70 mg/kg dose.  One caveat that the authors acknowledge is that Factor XIII, at low levels in infants and children after CPB, affects FIBTEM results but has no effect on the plasma fibrinogen level as determined by Clauss method. The relationship between ROTEM FIBTEM and plasma fibrinogen level must be further explored, and the proposed predictive equation tested in a larger pediatric population.                           Viviane Nasr (Boston) and Rania Abbasi (Indianapolis) – Section Editors  

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Modified Lung Ultrasound Examinations in Assessment and Monitoring of Positive End-Expiratory Pressure-Induced Lung Reaeration in Young Children With Congenital Heart Disease Under General Anesthesia.

Wu L, Hou Q, Bai J, Zhang J, Sun L, Tan R, Zhang M, Zheng J. Pediatr Crit Care Med. 2019 May;20(5):442-449. doi: 10.1097/PCC.0000000000001865. PMID:  31058784 Similar articles   Take Home Points: The most prevalent region of post-intubation atelectasis in...

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