Physiology and Pathology of Uterine Contractions

1. Physiology and Pathology of Uterine Contractions Michael G. Halaška, M.D. Department of Obstetrics and Gynaecology of 2nd Medical Faculty

2. Physiology • myometrium – smooth muscle • enlargment of the muscle cells • basal tonus • first contractions from 20thweek of gravidity • Braxton-Hick contractions

3. Physiology

4. Montevid Units • Montevid Units – addition of amlitudes of contractions in 10 minutes • pacemaker – contraction wave – 2cm/s • amplitude of an contraction • 1st stage – 40-60 mm Hg • 2nd stage – 80 mm Hg • closure of blood-vessels • veins : 20 mm Hg • artery: 60 mm Hg

5. Physiology • basal tonus 10 mm Hg • 1. stage of labour 30-40 mm Hg - 120 MU • 2. stage of labour 50-60 mm Hg - 250 MU • resting time >30 s

6. Physiology • Proper shape of the contractions • 1. stage • 2. stage • 3. stage

7. Physiology – starting factors • mechanical - ↑ pressure, ↓ volume • endocrine • estrogen - ↑ number of estro receptors, ↓ membrane potential, ↑ ATP in myocytes • oxytocine - ↓ membrane potential, ↑ PG • prostaglandins – preparing of cervix, contract. • neurogen • Fergusson reflex • Parasympaticus reflex

8. Recording the contractions • absolute – intrauterine - intrauterine catheter • relative – external - using piesoelectric effect

9. Indications and contraindications

10. Pathology • hypertonus • hyperactivity • hypoactivity • dystokia • failure of the abdominal muscle

11. Pathology • hypertonus • hyperactivity • hypoactivity • dystokia • failure of the abdominal muscle

12. Pathology - hypertonus • etiology: macrosomy, multiple pregnancy, premature separation of placenta • pathophysiology: ↑ basal tonus - ↑blood in veins– hypoxy • clinics: palpable, changes on CTG • treatment: tocolysis

13. Pathology • hypertonus • hyperactivity • hypoactivity • dystokia • failure of the abdominal muscle

14. Pathology - hyperactivity • > 390 MU, >7 contrac/min, resting time <30 s • etiology: hypersensitivity, overstimulation of the uterus • clinics: CTG changes • therapy: less oxytocine, tocolysis

15. Pathology • hypertonus • hyperactivity • hypoactivity • dystokia • failure of the abdominal muscle

16. Pathology - hypoactivity • < 100 MU, < 30 mm Hg, < 2 contract/min • type: primary – from the beginning secondary – during the labour • etiology: primary: hypoplasia of U., dystokia secondary: prolonged labour, overstimulation by oxytocine, exhaustion of the mother • clinics: CTG, no postup of the labour • therapy: oxytocine, tocolysis, rest

17. Pathology • hypertonus • hyperactivity • hypoactivity • dystokia • failure of the abdominal muscle

18. Pathology - dystokia • etiology: hypertonus of the cervix, failure of pacemakers, exhaustion of uterus • clinics: CTG, no postup of the labour • therapy: tocolysis, S.C.

19. Pathology • hypertonus • hyperactivity • hypoactivity • dystokia • failure of the abdominal muscle

20. Pathology - failure of abd. muscle • etiology: • disease of the muscle or inervation • disease which unables higher activity ( heart, eyes .. ) • epidural anesthesia • exhaustion of the mother • obesity • not cooperating mother • therapy: forceps, VEX, S.C.