Measures to Lower the Stress Response in Pediatric Cardiac Surgery

Stress Response in Children Undergoing Cardiac Surgery: a Prospective Randomized Comparison Between Low Dose Fentanyl (LDF), Low Dose Fentanyl Plus Dexmedetomidine (LDF + Dex) and High Dose Fentanyl (HDF).

Cardiac surgery induces a measurable stress response in patients which leads to increased morbidity and mortality post-operatively. Through clinical observation, anesthesiologists have determined that varying the combinations of anesthesia drugs used during surgery and just after reduces the stress response, and by extension, morbidity and mortality. However, only a few studies have explored this phenomenon scientifically.

In this study, we aim to demonstrate comparatively that use of dexmedetomidine in addition to low dose narcotics reduces the stress response in cardiac surgical patients and results in less morbidity and mortality. Additionally, dexmedetomidine (Dex) should facilitate safe early extubation in pediatric cardiac patients, which results in decreased ventilator associated co-morbidities. Patients will be randomly assigned to three groups; one group will receive low dose fentanyl (LDF), one will receive low dose fentanyl with dexmedetomidine (LDF + Dex), and one will receive high dose fentanyl (HDF). Blood samples will be collected post-induction, post-sternotomy, after going on cardiopulmonary bypass, at the completion of surgery, and post-operatively to determine the patients' stress hormone levels. The patients will receive standard post-operative care, and clinical data collected as part of this care will be used to determine the incidence of morbidity and mortality. The results of the blood tests will be correlated with the incidence of morbidity and mortality to demonstrate the relative effectiveness of the different anesthesia methods. Blood samples will be analyzed for the presence of the stress hormones cortisol, epinephrine, norepinephrine, adrenocorticotropic hormone (ACTH), Interleukin 8 (IL-8), TNF-alpha (Tumor Necrosis Factor), and nitrated albumin. Arterial blood gas, glucose and lactate levels, heart rate, blood pressure, use of vasoactive support, length of ventilator use, post-operative mortality, post-operative morbidity, length of Intensive Care Unit (ICU) stay, and length of hospital stay will be recorded. Children previously enrolled in the surgery study will complete assessments of their cognitive ability, developmental status, and emotional and behavioral adjustment. For the neuro-developmental outcome follow up, Children's cognitive ability will be assessed using the Stanford-Binet Intelligence Scales, 5th Edition (SB5). The SB5 is a widely-used measure of intellectual functioning that is normed for ages 2 and up. The test takes 30-50 minutes to administer to young children, and provides an overall Intelligence Quotient (IQ) score, as well as scores for five primary factors of cognitive ability: Fluid Reasoning, Knowledge, Quantitative Reasoning, Visual-Spatial Processing; and Working Memory. The SB5 has demonstrated excellent reliability and validity.

This arm will receive a total of 25 mcg/kg of Fentanyl (High Dose) in two divided doses. First half-dose given at induction and second half-dose given before incision.

This arm will receive a total of 10 mcg/kg of Fentanyl (Low Dose). First half-dose will be given at induction and second half -dose given before incision.

This arm will receive10 mcg/kg of Fentanyl (Low Dose) -2 divided doses. Dexmedetomidine (Dex) loading dose-1 mcg/kg over 10 min, then Dex infusion at 0.5mcg/kg/hr.

Fentanyl (High Dose) 25 mcg/kg in two divided doses. Half-dose will be given at induction and the second half-dose given prior to incision.

Fentanyl (Low Dose) 10 mcg/kg in two divided doses. Half-dose will be given at induction and the second half-dose given prior to incision.

Fentanyl (Low Dose) + Dexmedetomidine. Dexmedetomidine at 1mcg/kg loading dose over 10 minutes, followed by an infusion at a rate of 0.5mcg/kg/hr. In addition, this group will receive a total of 10 mcg/kg Fentanyl (Low Dose). Half the dose will be given at induction and the second half before incision.

N = 48 n = 16 (LDF); n = 17 (HDF); n = 15 (LDF + Dex) ACTH assayed by enzyme-linked immunosorbent assay (ELISA); Cytokine levels in plasma were measured using the Immulite automated chemiluminometer. Measured cytokines include interleukin (IL)-6, IL-8, IL-10, and tumor necrosis factor-α.

Blood draws to measure cytokines levels within one hour of draw: after induction; after sternotomy; after starting cardiopulmonary bypass; at the end of the procedure; and 24 hours after the procedure.

Comparisons Between Groups for Narcotic and/or Dexmedetomidine Intervention Influence on Length of CTICU Stay.

Comparisons Between Groups for Narcotic and/or Dexmedetomidine Intervention Influence on Time on Ventilator.

The Stanford-Binet test evaluates the overall IQ score from the assessment of cognitive ability. The test consists of 15 subtests, grouped into the four area scores. Six subtests are administered to all age levels. The subtests are: Vocabulary, Comprehension, Pattern Analysis, Quantitative, Bead Memory, and Memory for Sentences. Number of tests administered and test difficulty are based on the test taker's age and performance on subtest measuring word knowledge. The word knowledge subtest is given to all test takers and is the first subtest administered. A score of 100 is in the normal or average range. Higher scores suggest a higher level of functioning related to each category. (University of Cincinnati, 2003) Raw scores for each subtest within the overall test are converted to scaled scores using a table within each test manual to look up equivalents. Scaled scores are then converted to standard scores (range=50-150).

Blood draws to measure stress hormone levels within one hour of draw: after induction; after sternotomy; after starting cardiopulmonary bypass; at the end of the procedure; and 24 hours after the procedure.

The Stanford-Binet Intelligence Scale is now in its fifth edition (SB5) and was released in 2003. It is a cognitive ability and intelligence test that is used to diagnose developmental or intellectual deficiencies in young children. The test measures five weighted factors and consists of both verbal and nonverbal subtests. The five factors being tested are knowledge, quantitative reasoning, visual-spatial processing, working memory, and fluid reasoning. Raw scores for each subtest within the overall test are converted to scaled scores using a table within each test manual to look up equivalents. Scaled scores are then converted to standard scores (range=50-150). Higher scores suggest a higher level of functioning related to each category.

The ABAS-II is designed to evaluate whether an individual displays various functional skills necessary for daily living without the assistance of others. Thus, this instrument focuses on independent behaviors and measures what an individual actually does, in addition to measuring what he or she may be able to do. In addition, the ABAS-II focuses on behaviors an individual displays on his or her own, without assistance from others. The Parent/Primary Caregiver Form is a comprehensive, diagnostic measure of the adaptive skills that have primary relevance for the functioning of infants, toddlers, and preschoolers in the home and other settings, and can be completed by parents or other primary care providers. Each composite or domain score is determined by summing the appropriate scaled scores and then determining its equivalent composite or domain score by looking it up in a table located in the manual.The range for all scores is 50-150, with a higher score equaling a better outcome.

Inclusion Criteria: Childrens with the diagnosis of tetralogy of fallot, ventricular septal defect and atrioventricular septal defect who are under one year of age. Exclusion Criteria: Patients who are having reoperation. Patients with comorbidities, such as heart failure. Patients receiving digoxin preoperatively.

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