Physiological Changes During Pregnancy PDF

Physiological changes during pregnancy AWAD MOHAMMED ALQAHTANI BSc of Anesthesia Technology King Khalid University, Muhayil Asir  Pregnancy the state of carrying and developing fetus within the female body. Divide into three trimesters : 1- (The first tr...

Physiological changes during pregnancy AWAD MOHAMMED ALQAHTANI BSc of Anesthesia Technology King Khalid University, Muhayil Asir  Pregnancy the state of carrying and developing fetus within the female body. Divide into three trimesters : 1- (The first trimester ): is the first three months. 2- (The second trimester ): is the second three months of pregnancy. 3- (The third trimester ) is the last three months.  Pregnancy affects most organs system. Manyof these physiological changes appear to be adaptive and useful to the mother in tolerating the stresses of pregnancy, labor, and delivery.  Average maximum physiological changes associated with pregnancy  CNS Theminimum alveolar concentration (MAC) decrease during pregnancy- at term, by as much as 40%. Pregnant patients enhanced sensitivity to local anesthesia during regional anesthesia and analgesia.  Respiratory system Oxygen consumption and minute ventilation increase during pregnancy. Tidalvolume, respiratory rate and inspiratory reserve volume also increase. PaCo2 decreases to 28 – 32 mmHg.  Respiratory system Thoracic breathing is favored over abdominal breathing. Functional residual capacity (FRC) decreases up to 20% at term. The combination of decreased of FRC and increased in O2 consumption promotes rapid oxygen desaturation during period of apnea.  Respiratory system Significantrespiratory alkalosis is prevented by a compensatory decrease in plasma bicarbonate concentration. Hyperventilation may increase Pao2 slightly. Elevationof the diaphragm is compensated by an increase in the anteropsterior diameter of chest.  Cardiovascular System Cardiacoutput and blood volume increase to meet maternal and fetal metabolic demand. Anincrease (55%) in plasma volume in excess of increase red cell mass (45%) produce dilutional anemia and reduce blood viscosity.  Cardiovascular System Hemoglobin concentration usually remains greater than 11g/dL.  Cardiovascular System AT TERM : Blood volume has increased by 1000 – 1500 mL in most women. Total body volume reaches 90ml/kg.  Cardiovascular System Average blood loss during vaginal delivery is 400 – 500 mL, compared with 800 – 1000 mL for a cesarean section. Blood volume does not return to normal until 1 – 2 weeks after delivery.  Cardiovascular System Theincrease in cardiac output (40% at term) is due to increases in heart rate (20%) and stroke volume (30%). Cardiac chambers enlarge and myocardial hypertrophy is often noted echocardiography.  Cardiovascular System Approximately5% of women at term develop the supine hypotension syndrome. The cause of this syndrome appears to be complete or near-complete of the inferior vena cava by the gravid uterus. Renal & Gastrointestinal system Renal plasma flow and glomerular filtration rate increase during pregnancy. Creatinine and blood urea nitrogen may decrease. Plasma osmolality decrease by 8 -10 mOsm/kg. Renal & Gastrointestinal system Gastroesophageal reflex and esophagitis are common during pregnancy. Opioidand anticholinergic drugs reduce lower esophageal sphincter pressure, may facilitate gastroesophageal reflex and delay of gastric emptying.  Hepatic system Overall hepatic function and blood flow unchanged. A 20 – 30% decrease in serum pseducholinesterase activity at term.  Hematological system Pregnancyis associated with hypercoagulable state. Fibrinogen and concentrations of factors VII, VIII, IX, X, XII all increase. Questions are welcome Thank You 15  Reference Clinical Anesthesiology 6th edition 2018 the Author ; G.Morgan. Maged Mikhail and Michael Murray, chapter 40, page : 825 – 829.