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PHYSIOLOGIC CHANGES OF PREGNANCY

PHYSIOLOGIC CHANGES OF PREGNANCY. John G. Gianopoulos, M.D. Introduction.

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PHYSIOLOGIC CHANGES OF PREGNANCY

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  1. PHYSIOLOGIC CHANGES OF PREGNANCY John G. Gianopoulos, M.D.

  2. Introduction “During pregnancy, multiple physiologic adjustments are made to maintain maternal hemostasis. In a non-pregnant patient, many of these alterations would be considered pathologic rather than physiologic. This lecture will present the adjustments and alterations in maternal physiology.”

  3. CardiovascularCardiac Output-is  during pregnancy  1.51/min. Cardiac Output = heart rate x stroke volume. CO = HR x SV Output can be measured using direct Fick method, i.e.: Output of L. ventricle = 02 consumption (ml/min) A02 – V02

  4. Pulse rate  from 70  85 Heart rate  by catecholamines Chromotropic Inotropic Stroke volume increases  10%. Regulated by 2 mechanisms. Heterometric Homometric  CO, by  SV =  heart size

  5. Mean arterial pressure - average pressure throughout cardiac cycle – decreased.Total peripheral resistance – dependent upon arteriole diameter – ie., small changes in caliber = large changes in TRP. R = 8hLr4During pregnancy TPR is reduced.

  6. Increased blood flow – distribution. Uterus* Kidney Skin BreastsPulmonary Pressure – same as non-pregnant levels, due to: resistance to flow – vascular dilation  volume – capacitance Radiographic appearance – increased vascularity, enlarged pulmonary vessels.

  7. Venous Pressure -  in femoral pressure: Weight of uterus of iliac veins, inf. Vena cava. Hydrodynamic obstruction – due to  uterine outflow. Supine Hypotensive syndrome.

  8. ECG Changes-elevation of diaphragm heart moved upwards and rotated forward, + enlarged. Therefore, one would predict change in the electrical axis of the heart. Deviation to the left in the electrical axis (15-28).

  9. Volume and Composition of Blood.Plasma volume 40-50% RBC – 25-30% Hematocrit Fibrinogen Sedimentation rate Clotting Factors (VII, VIII, IX, X) Serum alkaline phosphatase

  10. RESPIRATIONDefinitionsTital volume (TV) - amount of air moving into lungs with each inspiration. Inspiratory Reserve Volume (IRV) – air inspired with maximal inspiratory effort in excess of tidal volume. Expiratory Reserve Volume (ERV) - volume expelled by active expiratory effort after passive expiration. Residual Volume (RV) – air left in lungs after maximal expiratory effort.

  11. Vital Capacity – greater amount of air that can be expired after maximal inspiratory effort. (timed vital capacity) Respiratory Minute Volume (RMV) – amount of air inspired/minute. Maximal Voluntary Ventilation – maximal amount of air that can be moved into and out of the lungs in one minute by voluntary effort.

  12. During Pregnancy the following occurs: TV  RMV – 40 %Hyperventilation Respiratory alkalosis – compensated  Alveolar CO2 40mm Hg  30mm Hg sensitivity of brain stem respiratory centers to pCO2 – progesterone.

  13. RENALPHYSIOLOGIC CHANGES: Renal Plasma Flow (RPF) - equals the amount of a substance excreted/unit of time divided by renal arteriovenous difference. (PAH,DIODRAST) RPF = U [x] V P [x] Renal blood flow – RPF x 1________ 1-hematocrit RPF is raised throughout pregnancy by 200-250 ml/1-min.

  14. Glomerular Filtration Rate (GRF) - of plasma perfusing the glomeruli-about 20% reaches the tubular system of the kidney as an ultrafiltrate-i.e., GFR. GFR = U [x] V = Clearance P [X] ↑ creatinine clearance ↑ urea clearance ↑ uric acid clearance

  15. Tubular Function: Na+Excretion-progesterone inhibits reabsorption, however, increasing aldosterone levels counteract this effect. H20=although plasma osmolality is ↓ and ECF ↑, urine volumes are similar to nonpregnant volumes. Hypothalamic resetting of osmoreceptors. Glycosuria-normal in pregnancy. Aminoaciduria-due to high circulating levels of cortisol?

  16. ↑ activity of renin-angiotensin- dissociation between pressor and renal effects. ↑ aldosterone ↑ erythropoietin

  17. GASTROINTESTINAL Decreased motility, delayed absorption ↓ gastric secretion, ↓ tone of cardiac sphincter (reflex esophagitis)

  18. ENDOCRINE STEROIDS: Progesterone-corpus luteum, fetal-placental unit. hyperpolarization of smooth muscle membrane potential- tone. ↑ temperature ↑ respiratory rate combined actions breast development

  19. Estrogens-ovarian, fetal-lacental unit combined actions with progesterone connective tissue effects liver-binding globulins ↑, serum enzymes ↑.

  20. PROTEIN HORMONES: HCG-human chorionic gonadotrophin-syncytial trophoblast corpus luteum diagnosis of pregnancy fetal adrenal hPL-human placental lactogen-syncytium GH like activity diabetogenic HCT-chorionic thyrotropin TSH like activity

  21. PITUITARY HORMONES:Anterior Lobe ADH, Oxytocin ADRENAL HORMONES: Cortisol-increases Aldosterone-increases PANCREAS - ↑/s cell function, placental insulinase

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