NCC Review Cardiac 8/22/12. Intrauterine Blood Flow. Topics

Transcription

1 NCC Review Cardiac Tracey Buckley MSN,RNC, NNP-BC Cape Fear Valley Health System Topics Transition to Extrauterine Life Cyanosis Congenital Heart Disease (CHD) Clinical Manifestations of CHD Therapeutic agents in cardiac disease Intrauterine Blood Flow Key Points Umbilical Cord = 1 vein and 2 arteries Umbilical Vein (UV) - O2 blood from placenta to fetus Umbilical Arteries (UA) - O2 blood from fetus to placenta Right ventricle - main pumping chamber Systemic vascular resistance (SVR) - LOW Pulmonary vascular resistance (PVR) - HIGH 1

2 Fetal Shunts Ductus venosus allows for blood to bypass the liver and enter the IVC Foramen Ovale allows blood to bypass the pulmonary system Ductus arteriosus allows blood to bypass the pulmonary system IVC/SVC PV s BODY RA DA LA LUNGS RV LV PLACENTA DA PA s Fetal Circulation Picture by T. Buckley NNP_BC Blood Gas Parameters of Umbilical Vessels Vessel ph pco2 po2 % O2 UA % UV % Normal blood gas parameters in term Newborn (ABG) ph pco2 po2 HCO3 >

3 How does the fetus survive??? Fetus tolerates lower po2 because Fetal hemoglobin (Hgb F) has a higher affinity for oxygen Increased Hgb in fetus = increased oxygen carrying capacity Increased ability to utilize glucose by anaerobic metabolism Hemodynamic Changes at Birth IVC/SVC PV s RA DA LA BODY LUNGS RV LV PLACENTA DA PA s AfterDelivery Picture by T. Buckley NNP_BC Normal Circulation after birth Courtesy of Microsoft Office. images/ 3

4 Hemodynamic Changes at Birth After delivery Gas exchange occurs in lungs (not placenta) Lungs expand with air PVR pulmonary blood flow LA pressure (now > RA pressure) FO closes SVR increases Ductus venosus closes (no more blood flow) PDA closes Cardiac Output Cardiac Output = Heart Rate x Stroke Volume Factors affecting cardiac output Preload Afterload Contractility Heart Rate Stroke Volume: Amount of blood ejected from the LV with each heartbeat Incidence of CHD 8 in 1000 live births 2 in 1000 presenting <1 year of age 2-5% recurrence if a previous child has CHD 6-7% if mother has CHD 1.5-3% if father has CHD 4

5 Incidence of specific defects VSD 16% Pulmonary stenosis with intact ventricular septum % TOF 8-10% ASD 10% TGA 5-10% PDA 4-10% (full-term infants) Coarctation of Aorta 5-8% HLHS 1.5% Incidence of specific defects VSD most common CHD TOF most common CHD beyond infancy TGA most common CHD in 1 st week of life HLHS 2 nd most common CHD in 1 st week of life and MOST common cause of mortality in 1 st week of life It is only after the maternal circulation is eliminated and the cardiovascular system of the infant becomes independent that the input of the anatomical and hemodynamic abnormalities become apparent 5

6 Clinical Manifestations of CHD Cyanosis***** Respiratory Distress****** Congestive Heart Failure and diminished cardiac output Abnormal rhythm murmurs Central Cyanosis Definition: the absolute amount of reduced hemoglobin Observed when Hgb is reduced by 3-5g/dl Anemia decreases clinical appearance Polycythemia increases clinical appearance Six components of oxygen delivery CNS Musculoskeletal Airways Gas exchange interference in the lungs Hemoglobin CV System 6

7 Central Cyanosis versus Peripheral Cyanosis Peripheral cyanosis Due to poor blood flow to the skin (acrocyanosis) Central cyanosis Generally due to R to L shunting Desaturated venous blood mixes with saturated blood Decreased blood to the lungs Left to Right Shunts SVR and PVR Blood takes the path of least resistance Blood shunts from the oxygenated side to the deoxygenated side (returns to lungs) Via ASD, VSD, PDA Left to Right Shunts IVC/SVC PV s RA LA BODY ASD/PFO LUNGS RV SVR VSD PVR LV PA s 7

8 Right to Left Shunts Blood shunts from the deoxygenated side to the oxygenated side (skips the lungs) Examples Pulmonary atresia: from RV thru PDA to aorta Tricuspid atresia: from RA thru ASD to LA Hypoplastic right heart: from RA thru ASD to LA Usually PATHOLOGIC!!! Right to Left Shunts IVC/SVC PV s RA LA BODY LUNGS SVR PVR RV LV PA s Pre-ductal R radial Arterial Sampling Sites Post-ductal L radial Umbilical Lower extremities 8

9 Cardiac versus Pulmonary Cyanosis Hyperoxia Test 1 ABG from right arm in room air 2 100% hood for 5-10 minutes 3 Repeat ABG 4 PaO2 >150mmHg = Respiratory 5 PaO2 unchanged = CHD Clinical Pearls GET A CENTRAL HEMATOCRIT r/o polycythemia as a cause of cyanosis cyanosis with crying = respiratory disease cyansis with crying = CHD Be sure you hear a split S 2 on cardiac exam Respirations Hyperpnea = hypoxia Tachypnea = pulmonary edema Classification of Cardiac Defects Lesions which increase pulmonary blood flow Lesions which decrease pulmonary blood flow Lesions which decrease systemic blood flow 9

10 Cyanotic versus Acyanotic Cardiac Defects Cyanotic Results in decreased oxygen in blood Right to left shunt Acyanotic Defect that does not lower blood oxygenation Left to right shunts Heart sounds Murmurs Pulse Pressure Blood Pressure Physical Exam Heart Sounds IVC/SVC PV s RA LA BODY S1 Tricuspid/Mitral Valves Closes RV S2 Pulmonic/Aortic Valves close LV PA s LUNGS 10

11 Murmurs ULSB ICS 1st URSB 2nd 3rd Nipple Line LLSB APEX 4th 5th Clipart courtesy of Microsoft Office. Labels by T. Buckley NNP-BC Pulse Pressure Difference between the SBP and DBP Widened pulse pressure Most common: PDA, truncus arteriosus Narrow Pulse Pressure Most Common: Pericardial tamponade, AS Blood Pressure Varies with gestational age Mean ~ gestational age Cuff selection is very important Small cuffs give falsely high values Hypertensive Infant Term SBP >95 Preterm SBP>80 Most common cardiac cause of hypertension - Coarctation 11

12 Shock Acute failure of circulatory function Characterized by inadequate tissue and organ perfusion Early compensated shock Blood flow preserved to heart, lung, brain, and kidneys Late Decompensated shock Tissue ischemia and metabolic acidosis S/S: UOP, HR, BP CHF Inability if the heart to meet the metabolic requirements of the body Etiology of CHF: Volume overload Pressure overload Cardiomyopathy Dysrhythmias Radiographic Findings of CHD Boot shaped heart TOF Egg on a string d-tga Snowman TAPVR 12

13 Congenital Heart Disease Cyanotic Heart Disease Left to Right Shunts Left and right sided obstructive lesions Valvular Disease Other abnormalities Cyanotic Heart Lesions TGA TOF PA (with intact ventricular septum) Truncus Arteriosus Tricuspid Atresia Ebstein s Anomaly Single Ventricle TAPVR Double Outlet Right Ventricle VSD ASD PDA Complete AV canal Partial APVR Left to Right Shunts 13

14 Left and Right Sided Obstructive Lesions Coarctation of the Aorta (CoA) Valvular Diseases Aortic Valve Regurgitation (AR) Mitral Valve Regurgitation (MR) Tricuspid Valve Regurgitation (TR) Other Diseases Hypoplastic Left heart syndrome (HLHS) Cardiomyopathy Eisenmenger s Complex Cor Pulmonale Pericardial Effusion 14

15 Prostaglandins Maintains patency of the ductus arteriosus in utero Administered to maintain blood flow through the DA TA, PA, severe PS, AS, coarctation or interrupted aortic arch Dosage: mcg/kg/min IV Adverse effects APNEA Vasodilation, hypotension,thrombocytopenia Cardiac Tamponade Blood, serous fluid, or air, under tension, fills the pericardial sack, Causes life-threatening compromise of venous return and decreased stroke volume Classic signs (Beck s Triad): Hypotension Pulsus paradoxus (acute drop in SBP) Jugular venous distention Muffled heart sounds Often associated with Central Lines in neonates Basic Principles of EKG P wave: Atrial depolarization QRS complex : ventricular depolarization T wave: ventricular repolarization U wave: late phase of repolarization 15

16 ECG Waves Courtesy of: Anthony Atkielski, public domain. Cardiac Conduction Patrick J. Lynch, medical illustrator; C. Carl Jaffe, MD, cardiologist. creativecommons.org/licenses/by/2.5/ ECG Interpretation 1. Measurements 2. Rhythm analysis 3. Conduction analysis 4. Waveform description 5. ECG interpretation 6. Comparison with previous ECG (if available) 16

17 Practice Questions References Fetal Circulation flash videos. Permission granted by Valerie O Loughlin, Associate Professor, Indiana State University. Verklan, M. & Walden. M. (2010). Core curriculum for neonatal intensive care nursing. Saunders/Elsevier. Brodsky, D. & Martin, C. (2003). Neonatology review. Hanley & Belfus. Merenstein, G & Gardner, S. (2002). Mosby. Ribcage clipart & Heart Clipart. Courtesy of Microsoft Office (public). References Image: Heart anterior view coronal section. Patrick J. Lynch, medical illustrator; C. Carl Jaffe, MD, cardiologist. Permission: Creative Commons Attribution 2.5 License (http ://creativecommons.org/licenses/by/2.5/ ). en.wikipedia.org/wiki/file:rls_12blauleg. Schematic diagram of normal sinus rhythm for a human heart as seen on ECG. (2007). Agateller (Anthony Atkielski). Permission: Public Domain. File:SinusRhythmLabels.svg 17