PHYSIOLOGIC CHANGES OF PHYSIOLOGIC CHANGES OF PREGNANCYPREGNANCY

John G. Gianopoulos, M.D.John G. Gianopoulos, M.D.

IntroductionIntroduction

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

CardiovascularCardiovascular

Cardiac Output-is Cardiac Output-is during pregnancy during pregnancy 1.51/min. 1.51/min.Cardiac Output = heart rate x stroke volume.Cardiac Output = heart rate x stroke volume.

CO = HR x SVCO = HR x SVOutput can be measured using direct Fick Output can be measured using direct Fick

method, i.e.:method, i.e.:Output of L. ventricle = Output of L. ventricle = 002 2 consumption (ml/min)consumption (ml/min)

A A02 02 – V– V0202

Pulse rate Pulse rate from 70 from 70 85 85Heart rate Heart rate by catecholamines by catecholamines

ChromotropicChromotropicInotropicInotropic

Stroke volume increases Stroke volume increases 10%. 10%. Regulated by 2 mechanisms. Regulated by 2 mechanisms.

HeterometricHeterometricHomometricHomometric

CO, by CO, by SV = SV = heart size heart size

Mean arterial pressure - average pressure Mean arterial pressure - average pressure throughout cardiac cycle – decreased.throughout cardiac cycle – decreased.

Total peripheral resistance – dependent upon Total peripheral resistance – dependent upon arteriole diameter – ie., small changes in arteriole diameter – ie., small changes in caliber = large changes in TRP.caliber = large changes in TRP.

R = R = 8hL8hL rr44

During pregnancy TPR is reduced.During pregnancy TPR is reduced.

Increased blood flow – distribution.Increased blood flow – distribution.Uterus*Uterus*KidneyKidneySkinSkinBreastsBreasts

Pulmonary Pressure – same as non-pregnant Pulmonary Pressure – same as non-pregnant levels, due to:levels, due to:

resistance to flow – vascular dilation resistance to flow – vascular dilation volume – capacitance volume – capacitanceRadiographic appearance – increased Radiographic appearance – increased

vascularity, enlarged pulmonary vessels.vascularity, enlarged pulmonary vessels.

Venous Pressure - Venous Pressure - in femoral pressure: in femoral pressure:Weight of uterus of iliac veins, inf. Vena Weight of uterus of iliac veins, inf. Vena cava.cava.Hydrodynamic obstruction – due to Hydrodynamic obstruction – due to

uterine outflow.uterine outflow.Supine Hypotensive syndrome.Supine Hypotensive syndrome.

ECG Changes-elevation of diaphragm heart ECG Changes-elevation of diaphragm heart moved upwards and rotated forward, + moved upwards and rotated forward, + enlarged. Therefore, one would predict enlarged. Therefore, one would predict change in the electrical axis of the heart. change in the electrical axis of the heart. Deviation to the left in the electrical axis (15-Deviation to the left in the electrical axis (15-2828).).

Volume and Composition of Blood.Volume and Composition of Blood.Plasma volume 40-50%Plasma volume 40-50%RBC – 25-30%RBC – 25-30%HematocritHematocritFibrinogenFibrinogenSedimentation rateSedimentation rateClotting Factors (VII, VIII, IX, X)Clotting Factors (VII, VIII, IX, X)Serum alkaline phosphataseSerum alkaline phosphatase

RESPIRATIONRESPIRATIONDefinitionsDefinitionsTital volume (TV) - amount of air moving Tital volume (TV) - amount of air moving

into lungs with each inspiration.into lungs with each inspiration.Inspiratory Reserve Volume (IRV) – airInspiratory Reserve Volume (IRV) – airinspired with maximal inspiratory effort ininspired with maximal inspiratory effort inexcess of tidal volume.excess of tidal volume.Expiratory Reserve Volume (ERV) - Expiratory Reserve Volume (ERV) -

volume expelled by active expiratory effort volume expelled by active expiratory effort after after passive expiration.passive expiration.

Residual Volume (RV) – air left in lungs Residual Volume (RV) – air left in lungs after maximal expiratory effort.after maximal expiratory effort.

Vital Capacity – greater amount of air Vital Capacity – greater amount of air that can be expired after maximal that can be expired after maximal inspiratory effort. (timed vital capacity)inspiratory effort. (timed vital capacity)

Respiratory Minute Volume (RMV) – Respiratory Minute Volume (RMV) – amount of air inspired/minute.amount of air inspired/minute.

Maximal Voluntary Ventilation – Maximal Voluntary Ventilation – maximal amount of air that maximal amount of air that can be can be moved moved into and out of the lungs in one into and out of the lungs in one minute by minute by voluntary effort.voluntary effort.

During Pregnancy the following occurs:During Pregnancy the following occurs: TV TV RMV – 40 % RMV – 40 %

HyperventilationHyperventilationRespiratory alkalosis – compensatedRespiratory alkalosis – compensated Alveolar CO Alveolar CO2 2 40mm Hg 40mm Hg 30mm Hg 30mm Hg

sensitivity of brain stem respiratory sensitivity of brain stem respiratory centers to pCOcenters to pCO22 – progesterone. – progesterone.

RENALRENAL

PHYSIOLOGIC CHANGES:PHYSIOLOGIC CHANGES:Renal Plasma Flow (RPF) - equals the amount of a Renal Plasma Flow (RPF) - equals the amount of a substance excreted/unit of time divided by renal substance excreted/unit of time divided by renal arteriovenous difference. (PAH,DIODRAST)arteriovenous difference. (PAH,DIODRAST)

RPF = RPF = U [x] V U [x] V

P [x]P [x]

Renal blood flow – RPF x Renal blood flow – RPF x 1________1________

1-hematocrit1-hematocrit

RPF is raised throughout pregnancy by 200-250 ml/1-minRPF is raised throughout pregnancy by 200-250 ml/1-min ..

Glomerular Filtration Rate (GRF) - of plasma Glomerular Filtration Rate (GRF) - of plasma perfusing the glomeruli-about 20% reaches the perfusing the glomeruli-about 20% reaches the tubular system of the kidney as an ultrafiltrate-i.e., tubular system of the kidney as an ultrafiltrate-i.e., GFR.GFR.

GFR = U [x] V = ClearanceGFR = U [x] V = Clearance

P [X]P [X]

↑↑ creatinine clearancecreatinine clearance

↑ ↑ urea clearanceurea clearance

↑↑ uric acid clearanceuric acid clearance

Tubular Function:Tubular Function:Na+Excretion-progesterone inhibits reabsorption, however, Na+Excretion-progesterone inhibits reabsorption, however, increasing aldosterone levels counteract this effect.increasing aldosterone levels counteract this effect.

HH220=although plasma osmolality is 0=although plasma osmolality is ↓ and ECF ↑,↓ and ECF ↑,

urine volumes are similar to nonpregnant volumes.urine volumes are similar to nonpregnant volumes.

Hypothalamic resetting of osmoreceptors. Hypothalamic resetting of osmoreceptors.

Glycosuria-normal in pregnancy.Glycosuria-normal in pregnancy.

Aminoaciduria-due to high circulating levels of cortisol?Aminoaciduria-due to high circulating levels of cortisol?

↑↑ activity of renin-angiotensin-activity of renin-angiotensin- dissociation between pressor and dissociation between pressor and

renal effects. renal effects.

↑ ↑ aldosteronealdosterone

↑ ↑ erythropoietinerythropoietin

GASTROINTESTINAL GASTROINTESTINAL

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

ENDOCRINEENDOCRINE STEROIDS:STEROIDS:

Progesterone-corpus luteum, fetal-placental unit.Progesterone-corpus luteum, fetal-placental unit.

hyperpolarization of smooth muscle membrane hyperpolarization of smooth muscle membrane

potential- tone.potential- tone.

↑ ↑ temperaturetemperature

↑ ↑ respiratory raterespiratory rate

combined actionscombined actions

breast developmentbreast development

Estrogens-ovarian, fetal-lacental unitEstrogens-ovarian, fetal-lacental unit

combined actions with progesteronecombined actions with progesterone

connective tissue effectsconnective tissue effects

liver-binding globulins liver-binding globulins ↑, serum enzymes ↑. ↑, serum enzymes ↑.

PROTEIN HORMONES:PROTEIN HORMONES:

HCG-human chorionic gonadotrophin-syncytial trophoblastHCG-human chorionic gonadotrophin-syncytial trophoblast

corpus luteumcorpus luteum

diagnosis of pregnancydiagnosis of pregnancy

fetal adrenalfetal adrenal

hPL-human placental lactogen-syncytiumhPL-human placental lactogen-syncytium

GH like activity GH like activity

diabetogenicdiabetogenic

HCT-chorionic thyrotropin TSH like activityHCT-chorionic thyrotropin TSH like activity

PITUITARY HORMONES:PITUITARY HORMONES:

Anterior LobeAnterior Lobe ADH, Oxytocin ADH, Oxytocin

ADRENAL HORMONESADRENAL HORMONES::

Cortisol-increasesCortisol-increases Aldosterone-increasesAldosterone-increases

PANCREASPANCREAS - - ↑/s cell function, placental insulinase↑/s cell function, placental insulinase