CCAS-CHiP Featured Commentaries

Congenital Heart Anesthesia and Intensive Care Featured Manuscripts January-May 2019

Anesthesia for High-risk Procedures in the Catheterization Laboratory.
Daaboul DG, DiNardo JA, Nasr VG.
Paediatr Anaesth. 2018 Dec 28. doi: 10.1111/pan.13571. [Epub ahead of print]
PMID: 30592354
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Take Home Points:

While reported adverse events in the catheterization lab range between 4-10%, the prevalence of adverse events (4.2%) and all cause-mortality (12%) during the hospital stay is highest for neonates. In addition to the risk of the procedure itself, young age, pulmonary artery hypertension, diastolic dysfunction, low cardiac-output, cyanosis, and low mixed venous saturation may further increase the risk.
Safe induction and maintenance of general anesthesia for high-risk cardiac catheterization require an understanding of the pathophysiology of each disease process, the planned procedure, its impact on the hemodynamics, the impact of the various anesthetic and pharmacologic interventions as well as experienced personnel and good communication between team members.

Commentary by Laura A. Downey, MD, a pediatric cardiac anesthesiologist at Children’s Healthcare of Atlanta/Emory University: Recent advances in technology allow for more complex procedures to be performed in smaller patients in the cardiac catheterization laboratory. Multiple cardiology registries have been created to assess adverse events and assign risk scores to these patients. However, none of the developed scores specifically address anesthetic risk. Therefore, these authors discuss perioperative procedure and anesthetic-related risk assessment as well as the anesthetic approach for the management of neonates undergoing specific high-risk procedures in the cardiac catheterization laboratory.

The authors discuss several registries that cardiologists have used to risk stratify patients presenting to the catheterization lab, including two different risk scores. One such prediction model for high-severity adverse events is The Catheterization for Congenital Heart Disease Adjustment of Risk Method (CHARM), which uses procedure risk category, number of variables of hemodynamic vulnerability, and age <1 year. Incorporating the procedure risk group and hemodynamic variable in CHARM, the large IMPACT dataset was used to create a more generalizable model to predict major adverse events that included: procedure risk group, four hemodynamic vulnerability variables, age, the presence of renal insufficiency, and single ventricle physiology. Concurrent with the development of the CHARM model, the Congenital Cardiac Interventional Study Consortium (CCISC) group developed the Catheterization Risk Score for Pediatrics (CRISP). This scoring system assigns patients into one of five CRISP categories that assigns points based on weight, age, inotropic support/extracorporeal membrane oxygenation (ECMO), systemic illness/organ failure, physiological status, pre-catheterization diagnosis, procedure type, and the procedure performed. The risk of serious adverse events ranges from 1% for CRISP 1 and 36.8% for CRISP 5.

Despite the above models, neither of these developed scores specifically address anesthetic risk. Recently, the C3PO database determined a 1.83% risk of overall sedation/airway related events and only 0.14% category 4 life threatening events and 0.014% category 5 catastrophic events (two cardiac arrests). Low patient weight (<4kg), lowered mixed venous saturation (single ventricles <50%, two ventricles < 60%), and the presence of additional non-cardiac comorbidities were correlated with high severity of sedation or airway anesthesia related complications. In light of these statistics and a paper that demonstrated the involvement of cardiac anesthesiologists lower the incidence of cardiac arrest from 3.5% to 0.7%, a 2016 expert consensus statement recommended that anesthesiologists with advanced skills and understanding of the pathophysiology and expertise in management of patients with CHD provide care for high-risk patients.

The authors discuss the importance of preparing for the unique challenges that anesthesiologists face in the cardiac catheterization laboratory: limited access to patients due to small workspaces and equipment, poor lighting, radiation exposure, offsite location, and potential difficulty in getting help fast. Low ambient temperatures and the frequent flushing of catheters and sheaths may result in hypothermia and volume load, especially in infants. Due to catheters crossing through the heart, risks include dysrhythmias, bleeding from perforation of heart structures or vessels, damage to valves, stroke and risk of air embolism. In order to prepare for a variety of potential complications, the authors recommend adequate IV access, readily available resuscitation drugs and defibrillation pads, easily accessible blood (the authors recommend cross-matched blood, however other institutions may use O-negative blood), and ECMO support if necessary.

Based on factors in the CRISP and CHARM models that predict adverse events, these authors specifically discuss perioperative concerns and anesthesia technique for interventional procedures performed in patients <1 year of age that present the highest risk of adverse events due to procedure and anesthesia-related risks: 1) Closure of a patent ductus arteriosus (PDA); 2) Ductal stent; 3) right ventricular outflow tract (RVOT) stenting; 4) Pulmonary atresia with intact ventricular septum (PA/IVS); 5) Valvotomy in critical aortic stenosis (AS).

Patent Ductus Arteriosus (PDA) Closure
These authors summarize the recent literature regarding PDA device closure, specifically focusing on recent studies that demonstrate up to 88% success of PDA occlusion in preterm and low birth weight infants (mean age 30 days, mean weight 1249g) with very low complication rates. Although relatively safe, important complications include device embolization, ductal spasm, residual shunts, left pulmonary artery obstruction, development of aortic coarctation, and vascular injury. Ductal spasm, occurring in 2.1%-3.7% of closures, may result in failure of the procedure due to undersizing of the device and risk of embolization. For anesthesiologists, device embolization and retrieval may present the most challenging complication of this procedure, including possible hemodynamic instability, valvular damage, vascular injury, or emergent surgical intervention with cardiopulmonary bypass.
Ductal Stenting
Traditionally achieved surgically with a Blalock Taussig (BT) shunt, creating a reliable source of pulmonary blood can now be achieved in the cardiac catheterization laboratory with ductal stenting. When ductal stenting is compared to a BT shunt, patients receiving a ductal stent had lower complication rates, shorter length of stay (LOS) in the intensive care unit (ICU), and more symmetrical pulmonary artery (PA) growth (Glatz et al), while a similar study found shorter mechanical ventilation times, shorter ICU LOS, and less ECMO. Both studies found that ductal stent patients had a higher rate of reintervention, unrelated to cyanosis. Important anesthetic considerations for patients receiving ductal stents, include appropriate discontinuation of prostaglandin E2 to allow the ductus to be small enough to wedge the stent in place, but not so small that pulmonary blood flow (PBF) is compromised. During the procedure, anesthesiologists should be prepared to support hemodynamic changes during complete or partial occlusion of the ductus due to catheter manipulation or ductus spasm. Occasionally, the stent may not be able to be deployed or hypoxemia persists despite stent deployment and surgical intervention to place a shunt may be required.
RVOT Stenting
Advances in the catheterization lab make RVOT stenting and balloon dilation of the pulmonary valve a reasonable alternative for patients with RVOT obstruction (i.e. TOF patients). This approach is most beneficial in premature or low birth weight patients, who have the highest operative morbidity and mortality. When compared to a BT shunt, the RVOT stent group had shorter time to surgical repair (232 days versus 428 days), lower intensive care admission rate (22% versus 100%) and shorter length of stay (median 7 days versus 14 days). Procedure-related complications include perforation of the pulmonary artery or RVOT leading to hemothorax and pericardial effusion, stent embolization, or tricuspid valve regurgitation. Anesthesiologists should be prepared for possible hemorrhage due to RVOT or PA perforation with immediate access to red blood cells and adequate IV access. Transient pulmonary edema may occur during the procedure due to the sudden increase in pulmonary blood flow. Pulmonary edema should be treated with positive end-expiratory pressure (PEEP) and diuretics and admission to the ICU should be considered.
Pulmonary Atresia with Intact Ventricular Septum
Patients with PA/IVS require PGE2 to maintain ductal patency and pulmonary blood flow. These patients are often taken to the catheterization laboratory early to determine if the patient has RV-dependent coronary circulation (RV-DCC). In patients without RV-DCC, the pulmonary valve can be opened with radiofrequency (RF) perforation and stented. RF of the pulmonary valve is contraindicated in patients with RV-DCC who require PDA stent placement, BT shunt placement, or transplantation. Mortality is estimated at 6.69%. As these patients are at risk for sub-endocardial ischemia, RV preload and systemic diastolic pressure must be adequate to maintain coronary perfusion. Common complications are similar to patients undergoing RVOT stenting, including perforation of the PA/RVOT. Atrial and ventricular arrhythmias and heart block are likely related to coronary ischemia. Anesthesiologists must, therefore, be prepared for emergent transfusion or cardioversion in these procedures. In the setting of borderline RV function, pulmonary blood flow may not be sufficient and PGE2 will need to be started.
Critical Aortic Stenosis
Of the 6% of patients with left ventricular outflow obstruction (LVOTO), aortic stenosis accounts for approximately 80% of these cases. Neonates with critical AS usually present with signs of hypoperfusion, cyanosis, and lethargy as the ductus begins to close. Thus, prostaglandins are started in order to maintain ductal patency and systemic perfusion. Balloon valvotomy has been shown to decrease the aortic gradient by 50%, but with a 15% risk of aortic regurgitation (AR). Many of these patients will present for surgical intervention for AR or re-intervention for recurrent stenosis. Procedure risks include arrhythmias and perforation. During balloon dilation, cardiac arrest may occur due to cessation of cardiac output. In addition to preparation for hemorrhage, arrhythmias, or cardiac arrest, the goal of the anesthetic is to maintain coronary perfusion and cardiac output. The authors recommend an opioid-based anesthetic with readily available inotropic support, such as epinephrine.

As demonstrated by the above discussion, safe induction and maintenance of general anesthesia for high-risk cardiac catheterization require an understanding of the pathophysiology of each disease process, the planned procedure, its impact on the hemodynamics, the impact of the various anesthetic and pharmacologic interventions as well as experienced personnel and good communication between team members.

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
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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, MB, ChB, FRCA, 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.

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
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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, MD, 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 seven 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 three 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 three and seven 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 six 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 four to five 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 seven 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.