Neonatal Physiology Tulane Pediatric Surgery

Topics  Fluids and Electrolytes  Cardiopulmonary  Temperature Regulation  Jaundice  Host Defenses  Surgical Stress Response

Fluids and Electrolytes  Glucose –Placental –Glycogen Storage –Gluconeogenesis –Hypoglycemia  SGA  Surgical Pts –Hyperglycemia

Fluids and Electrolytes  Calcium –Placental Diffusion  75% third trimester –Limited Stores –Renal Immaturity –Hypoparathyroidism –Citrate can bind and decrease Ca

Fluids and Electrolytes  Magnesium –Associated with Calcium –Growth Retardation –Maternal Diabetes –Exchange Transfusions

Fluids and Electrolytes  Blood Volume –Highest – Delivery  Cord Clamping –Polycythemia  Hct>65  Diabetes  Toxemia  SGA  Partial Exchange

Fluids and Electrolytes  Hemolytic Anemia –Maternal Antibodies –Direct Coombs –Rh most common –Congenital Infections –SS Dz

Fluids and Electrolytes  Anemia –Premature Infants –Erythropoeitin

Fluids and Electrolytes  Hemoglobin –80% Fetal –Erythropoeisis 2-3 months –P50 Adult Hgb – 27 mmHg –P50 Fetal Hgb – 8 mmHg

Jaundice  Hemolysis  Glucoronyl Transferase  Unconjugated Hyperbilirubinemia  Peaks 3 rd Day – 6-7mg/dl  Resolves Day 10

Jaundice  Non Physiologic –Breast Feeding –Hemolytic Disease –Hypothyroid –Pyloric Stenosis –Crigler-Najar –Extravascular Blood –Biliary Atresia –Hepatitis

Jaundice  Non-Physiologic –Conjugated > 2mg/dl –Rises > 5mg/dl/day –Born Jaundiced –Doesn’t Resolve

Temperature Regulation  Evaporation  Conduction  Convection  Radiation

Temperature Regulation  Humidified Environments –Incubator –Ventilator Circuits  Radiant Warmers –Dry Heat –Increased insensible losses  Clothes/Blankets

Temperature Regulation  Hypothermia –Hypoglycemia –Vasoconstriction –Coagulopathy –Emergence from Anesthesia

Renal Function  Low GFR  Better at 2 weeks  Normal at 1-2 years  Decreased Concentrating Ability –600mOsm  Insensitive to ADH

Cardiopulmonary  Fetal Circulation –Right to Left Shunts  Foramen Ovale  Ductus Arteriosus –Hypoxemia –Hypercarbia –Acidosis

Cardiopulmonary  Persistent Fetal Circulation –Sepsis –Meconium Aspiration –Congenital Diaphragmatic Hernia –Idiopathic –Treatment  Ventilation  Pharmacology  ECMO

Cardiopulmonary  Surfactant Deficiency –Premature –Alveolar Stability –Exogenous Administration

Host Defenses  Cellular Immunity –WBCs  Phagocytosis  Adherence  Killing  Decreased Stores  Poor Stem Cell Production

Host Defenses  Immunoglobulins –IgG crosses the placenta –Poor Response to Antigen Challenge  IgA and IgM  No type specific Antibodies –Decreased Complement System Function –Increased Mortality with Pyogenic Bacterial Infections

Surgical Stress Response  Initially Poorly Understood –Crude Monitoring –Few Outcome Studies  Myths –Anesthetics – Unsafe/Not Approved –Pain –Could Anesthesia Blunt Surgical Stress Response?

Surgical Stress Response  Measured Catecholamines, Insulin, Cortisol.  Adult Physiology  Levels Decreased when Anesthesia Administered