Physiological changes in Pregnancy & its Anaesthetic implications <ul><li>Dr. Shailendra.V.L. MBBS, DA, MD. </li></ul><ul>...
Introduction <ul><li>Rapidly growing  fetus </li></ul><ul><li>Rising levels of  progesterone,  oestrogen, prostaglandin & ...
Changes in the pregnant patient   <ul><li>Changes due to uterine enlargement </li></ul><ul><li>Changes to support the foet...
Changes in the systems <ul><li>Cardiovascular System </li></ul><ul><li>Respiratory System </li></ul><ul><li>Haemopoietic S...
Changes in uterus <ul><li>Uterine blood flow increases from 50 ml/  min to 700 – 800 ml /min  </li></ul><ul><li>Uterine we...
Uterine blood flow <ul><li>Uterine Blood Flow - UBF: </li></ul><ul><ul><li>Uteroplacental vascular bed is passive capacita...
Cardiovascular system <ul><li>Changes in the cardiovascular system: </li></ul><ul><li>Intravascular fluid volume:  +  35% ...
 
Cardiovascular system <ul><li>Mean arterial pressure: MAP: </li></ul><ul><ul><li>-Inspite of increase of cardiac output, M...
Cardiovascular system <ul><li>Compression of Inferior Venacava: IVC: </li></ul><ul><ul><li>In supine position the gravid u...
Cardiovascular system <ul><li>8 to 15% of pregnant women have Overt Caval Compression (supine hypotensive syndrome) </li><...
Cardiovascular system <ul><li>Poseiro Effect: </li></ul><ul><li>Uterine artery is compressed  during  </li></ul><ul><li>ut...
Cardiovascular system <ul><li>Physiological Anaemia in Pregnancy: </li></ul><ul><li>Total red cell mass increase by 30% (2...
Cardiovascular system <ul><li>Heart rate: increases by about 15 beats /min </li></ul><ul><li>Arterial pressure: minimal ch...
Respiratory system <ul><li>Changes in the respiratory system: </li></ul><ul><li>Minute volume:  + 50% </li></ul><ul><li>Ti...
 
Respiratory system <ul><li>Edematous mucosa of upper resp tract: </li></ul><ul><ul><li>Smaller Et tubes </li></ul></ul><ul...
 
Haemopoietic system <ul><li>Physiological anemia of pregnancy </li></ul><ul><li>Fibrinogen, factors VII, VIII and X increa...
 
Gastro-intestinal system <ul><li>Decrease in lower oesophageal tone </li></ul><ul><li>Delay in gastric emptying: </li></ul...
Hepatic system <ul><li>No alterations in the liver function </li></ul><ul><li>Serum cholinesterase activity   </li></ul><...
Renal system <ul><li>Renal plasma flow  ↑ </li></ul><ul><li>Glowmerular filtration rate  ↑ </li></ul><ul><li>Tubular reabs...
 
Metabolism & Nutrition <ul><li>Basal metabolic rate:  ↑  by 15 to 20% </li></ul><ul><li>Weight gain upto 11 kgs </li></ul>...
Nervous system <ul><li>↓  in minimum alveolar concentrations </li></ul><ul><li>exaggerated lumbar lardosis contribute to  ...
Placental functions <ul><li>Metabolism </li></ul><ul><li>Endocrine secretion </li></ul><ul><ul><li>Human chorionic gonadot...
Placental blood flow <ul><li>Placental Blood Flow = 500-700ml/min </li></ul><ul><li>( approximately 10% of the Cardiac out...
Placental drug transfer <ul><li>Passive-diffusion is the mechanism </li></ul><ul><li>Q/t = {k x A x (Cm-Cf)}  / D </li></u...
Placental transfer of drugs <ul><li>Diffusion Coefficient depends on: </li></ul><ul><ul><li>molecular weight </li></ul></u...
Anaesthetic implications <ul><li>Pre-anaesthetic considerations: </li></ul><ul><ul><li>Starvation </li></ul></ul><ul><ul><...
Anaesthetic implications <ul><li>General Anaesthesia: </li></ul><ul><ul><li>Posture </li></ul></ul><ul><ul><li>Tracheal In...
Anaesthetic implications <ul><li>Regional Anaesthesia: </li></ul><ul><ul><li>Posture </li></ul></ul><ul><ul><li>Technique ...
Summary <ul><li>Cardiovascular changes </li></ul><ul><li>Respiratory changes </li></ul><ul><li>Gastro-intestinal changes <...
Bibliography <ul><li>Anaesthesia & Co-existing diseases-Stoelting </li></ul><ul><li>Short Practice of Anaesthesia – Church...
<ul><li>Thank  you </li></ul>
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Physiological Changes In Pregnancy

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Describes the various physicilogical changes in pregnancy

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Physiological Changes In Pregnancy

  1. 1. Physiological changes in Pregnancy & its Anaesthetic implications <ul><li>Dr. Shailendra.V.L. MBBS, DA, MD. </li></ul><ul><li>Specialist in Anaesthesia, </li></ul><ul><li>Bukariya General Hospital. </li></ul>
  2. 2. Introduction <ul><li>Rapidly growing fetus </li></ul><ul><li>Rising levels of progesterone, oestrogen, prostaglandin & HCG </li></ul><ul><li>Increasing size of uterus </li></ul><ul><li>All systems undergo changes </li></ul><ul><li>Placenta </li></ul>
  3. 3. Changes in the pregnant patient <ul><li>Changes due to uterine enlargement </li></ul><ul><li>Changes to support the foetus </li></ul>
  4. 4. Changes in the systems <ul><li>Cardiovascular System </li></ul><ul><li>Respiratory System </li></ul><ul><li>Haemopoietic System </li></ul><ul><li>Hepatic System </li></ul><ul><li>Renal System </li></ul><ul><li>Gastro-intestinal System </li></ul><ul><li>Metabolism & Nutrition </li></ul><ul><li>Central Nervous System </li></ul>
  5. 5. Changes in uterus <ul><li>Uterine blood flow increases from 50 ml/ min to 700 – 800 ml /min </li></ul><ul><li>Uterine weight increases from 30-60 g to 1000 g </li></ul>
  6. 6. Uterine blood flow <ul><li>Uterine Blood Flow - UBF: </li></ul><ul><ul><li>Uteroplacental vascular bed is passive capacitance bed </li></ul></ul><ul><ul><li>Intervillous blood flow exhibits no auto regulation </li></ul></ul><ul><ul><li>UBF dependent on mean arterial pressure, aorto-caval compression & cardiac output </li></ul></ul>
  7. 7. Cardiovascular system <ul><li>Changes in the cardiovascular system: </li></ul><ul><li>Intravascular fluid volume: + 35% </li></ul><ul><li>Plasma volume: + 45% </li></ul><ul><li>Erythrocyte volume: + 20% </li></ul><ul><li>Cardiac Output: + 40% </li></ul><ul><li>Stroke volume: + 30% </li></ul><ul><li>Heart rate: + 15% </li></ul><ul><li>Peripheral Circulation: </li></ul><ul><li>Systolic BP: no change </li></ul><ul><li>Diastolic BP: - 15% </li></ul><ul><li>Systemic Vascular Resistance: - 15% </li></ul><ul><li>Femoral venous pressure: + 15% </li></ul>
  8. 9. Cardiovascular system <ul><li>Mean arterial pressure: MAP: </li></ul><ul><ul><li>-Inspite of increase of cardiac output, MAP is maintained due to concomitant decrease in peripheral resistance </li></ul></ul>
  9. 10. Cardiovascular system <ul><li>Compression of Inferior Venacava: IVC: </li></ul><ul><ul><li>In supine position the gravid uterus compresses the IVC and decreases the CO without fall in the blood pressure called as Concealed caval compression. </li></ul></ul><ul><ul><li>Reasons for no fall in blood pressure are: </li></ul></ul><ul><ul><ul><li>Reflex vaso constriction </li></ul></ul></ul><ul><ul><ul><li>Diversion of blood through paravertebral venous plexus </li></ul></ul></ul>
  10. 11. Cardiovascular system <ul><li>8 to 15% of pregnant women have Overt Caval Compression (supine hypotensive syndrome) </li></ul><ul><ul><li>Hypotension </li></ul></ul><ul><ul><li>Sweating </li></ul></ul><ul><ul><li>Bradycardia </li></ul></ul><ul><ul><li>Pallor </li></ul></ul><ul><ul><li>Nausea </li></ul></ul><ul><ul><li>Vomiting </li></ul></ul><ul><li>Prevention of SHS: (aim is to displace the uterus) </li></ul><ul><ul><li>Providing left lateral tilt 15 degrees </li></ul></ul><ul><ul><li>Placing wedge under the right buttock </li></ul></ul>
  11. 12. Cardiovascular system <ul><li>Poseiro Effect: </li></ul><ul><li>Uterine artery is compressed during </li></ul><ul><li>uterine contractions & by the presenting </li></ul><ul><li>part of the fetus reducing the UBF </li></ul>
  12. 13. Cardiovascular system <ul><li>Physiological Anaemia in Pregnancy: </li></ul><ul><li>Total red cell mass increase by 30% (250-450ml) </li></ul><ul><li>Plasma volume increase by 50% (about 1250ml) </li></ul><ul><li>Overall increase of 40% blood volume with fall in haematocrit </li></ul>
  13. 14. Cardiovascular system <ul><li>Heart rate: increases by about 15 beats /min </li></ul><ul><li>Arterial pressure: minimal change noted </li></ul><ul><li>Heart Size: Gravid uterus pushes the diaphragm cepahalad & displaces the heart. </li></ul><ul><ul><li>ECG shows false left axis deviation </li></ul></ul><ul><ul><li>Chest X ray shows (false) cardiac dilatation </li></ul></ul>
  14. 15. Respiratory system <ul><li>Changes in the respiratory system: </li></ul><ul><li>Minute volume: + 50% </li></ul><ul><li>Tidal volume: + 40% </li></ul><ul><li>Breathing rate: + 10% </li></ul><ul><li>FRC: - 20% </li></ul><ul><li>Expiratory reserve volume: - 20% </li></ul><ul><li>Residual volume: - 20% </li></ul><ul><li>Oxygen consumption: + 20% </li></ul>
  15. 17. Respiratory system <ul><li>Edematous mucosa of upper resp tract: </li></ul><ul><ul><li>Smaller Et tubes </li></ul></ul><ul><ul><li>Gentle suctioning & larngoscopy </li></ul></ul><ul><li>Decreased FRC, ERV,RV: </li></ul><ul><li>Increased O2 consumption: </li></ul><ul><ul><li>Pre-oxygenation prior to induced apnea </li></ul></ul><ul><li>Rate of fall in PaO2 per minute of apnea is 159mm hg in pregnant and 59 mm hg in non-pregnant state </li></ul>
  16. 19. Haemopoietic system <ul><li>Physiological anemia of pregnancy </li></ul><ul><li>Fibrinogen, factors VII, VIII and X increased </li></ul><ul><li>Makes the blood hypercoaguable & increases the risk of thromboembolism </li></ul><ul><li>This hypercoaguability along with uterine inversion helps in reducing blood loss after delivery </li></ul>
  17. 21. Gastro-intestinal system <ul><li>Decrease in lower oesophageal tone </li></ul><ul><li>Delay in gastric emptying: </li></ul><ul><ul><li>Pylorus is pushed upwards & forwards making it non-dependent </li></ul></ul><ul><ul><li>Relaxant effect on gastric smooth muscle </li></ul></ul><ul><li>Increased intragastric pressure </li></ul>
  18. 22. Hepatic system <ul><li>No alterations in the liver function </li></ul><ul><li>Serum cholinesterase activity  </li></ul><ul><li>Does not interfere with the suxamethonium (Scoline) R metabolism </li></ul>
  19. 23. Renal system <ul><li>Renal plasma flow ↑ </li></ul><ul><li>Glowmerular filtration rate ↑ </li></ul><ul><li>Tubular reabsorbtion rate ↑ </li></ul><ul><li>Blood Urea Nitrogen 40%  </li></ul>
  20. 25. Metabolism & Nutrition <ul><li>Basal metabolic rate: ↑ by 15 to 20% </li></ul><ul><li>Weight gain upto 11 kgs </li></ul><ul><li>Serum protein concentration ↓ </li></ul><ul><li>Albumin concentration ↓ </li></ul><ul><li>Drugs are less bound to serum proteins thereby increasing the free drug availability </li></ul>
  21. 26. Nervous system <ul><li>↓ in minimum alveolar concentrations </li></ul><ul><li>exaggerated lumbar lardosis contribute to cephalad spread of the local anaesthetic </li></ul><ul><li>engorged epidural plexus of veins will decrease the amount of the local anaesthetic in epidural blocks </li></ul><ul><li>engorged epidural veins will block the inter-vertebral foramina and prevent the escape of the local anaesthetic </li></ul>
  22. 27. Placental functions <ul><li>Metabolism </li></ul><ul><li>Endocrine secretion </li></ul><ul><ul><li>Human chorionic gonadotrophin </li></ul></ul><ul><ul><li>Human chorionic somatotrophin </li></ul></ul><ul><ul><li>Progesterone </li></ul></ul><ul><ul><li>Estrogen </li></ul></ul><ul><li>Molecular transfer </li></ul>
  23. 28. Placental blood flow <ul><li>Placental Blood Flow = 500-700ml/min </li></ul><ul><li>( approximately 10% of the Cardiac output) </li></ul><ul><li>Maternal blood pressure </li></ul><ul><li>Maternal cardiac output </li></ul><ul><li>Vasomotor tone of the uterine vessels </li></ul><ul><li>Pathological changes of the placenta </li></ul><ul><li>State of uterine contraction </li></ul>
  24. 29. Placental drug transfer <ul><li>Passive-diffusion is the mechanism </li></ul><ul><li>Q/t = {k x A x (Cm-Cf)} / D </li></ul><ul><li>Q: quantity of free drug (non ionized & non protein bound) crossing to placenta </li></ul><ul><li>t : per unit of time </li></ul><ul><li>k: diffusional coefficient of the drug </li></ul><ul><li>A: total area available for transfer </li></ul><ul><li>Cm-Cf: difference between maternal & fetal drug concentrations </li></ul><ul><li>D: distance across the membrane </li></ul>
  25. 30. Placental transfer of drugs <ul><li>Diffusion Coefficient depends on: </li></ul><ul><ul><li>molecular weight </li></ul></ul><ul><ul><li>spatial configuration </li></ul></ul><ul><ul><li>degree of ionization </li></ul></ul><ul><ul><li>lipid solubility </li></ul></ul><ul><li>Most anaesthesia drugs cross the placental barrier except the muscle relaxants because of their large size molecule (quaternary ammonia compounds) </li></ul>
  26. 31. Anaesthetic implications <ul><li>Pre-anaesthetic considerations: </li></ul><ul><ul><li>Starvation </li></ul></ul><ul><ul><li>Respiratory infection </li></ul></ul><ul><ul><li>Prophylaxis against pulmonary aspiration </li></ul></ul>
  27. 32. Anaesthetic implications <ul><li>General Anaesthesia: </li></ul><ul><ul><li>Posture </li></ul></ul><ul><ul><li>Tracheal Intubation </li></ul></ul><ul><ul><li>Placental transfer of drugs </li></ul></ul><ul><ul><li>Pre oxygenation </li></ul></ul>
  28. 33. Anaesthetic implications <ul><li>Regional Anaesthesia: </li></ul><ul><ul><li>Posture </li></ul></ul><ul><ul><li>Technique </li></ul></ul><ul><ul><li>Vasopressors </li></ul></ul><ul><ul><li>Oxygen supplementation </li></ul></ul>
  29. 34. Summary <ul><li>Cardiovascular changes </li></ul><ul><li>Respiratory changes </li></ul><ul><li>Gastro-intestinal changes </li></ul><ul><li>Haemopoietic changes </li></ul><ul><li>Placental transfer of drugs </li></ul>
  30. 35. Bibliography <ul><li>Anaesthesia & Co-existing diseases-Stoelting </li></ul><ul><li>Short Practice of Anaesthesia – Churchill Davidson </li></ul><ul><li>Refresher Course Lectures, Manipal, ISA 1989 </li></ul>
  31. 36. <ul><li>Thank you </li></ul>
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