Cardiovascular Changes in Pregnancy
How is CVP effected?
No change to CVP - Dilated sytemmic & pulmonary circulation
When does increases in intravascular fluid volume begin?
THe 1st trimester
↑ CO primarily due to ↑ SV (preload) and HR: 10th week? 3rd trimester? During labor? During contraction?
10th week ~ 10% aove norm 3rd trimester - 40% above norm Labor 30% above norm During contraction 45% above norm
Average expansion of vol. at term?
1500 ml
What must SBP be kept at to maintain maternal perfusion pressure to the vasculature and meet fetal demands?
>100mmHg
Hemoglobin parameter at term gestation? Blood vol. Plasma vol. RBC vol.
Blood vol. +45% Plasma vol +55% RBC vol. +30%
Cardiovascular changes during pregnancy: ICREAASES
Inteavacual vol. ↑ 35% Plasma vol. ↑ 45% RBC vol. ↑ 20% CO. ↑ 40-50% SV. ↑ 30% HR. ↑15-25% Femoral ven press. ↑ 15%
What happens to the mothers oxyhemoglobin dissociation curve at term?
Shift to the Rt. P50 shifts Rt (26.7 - 30.2) at term. Remember Rt shift = O2 is more easily released to the tissue.
↑ intravascular fluid vol. off sets blood loss with delivery. Vaginal delivery EBL? C-sec delivery EBL?
Vaginal 500-600 ml avg. C-section 800-1000 ml avg.
During pregnancy SVE does what?
↓ ~20%
During pregnancy Peripheral vascular resistance does what?
↓ ~34% Offsets the ↑ in CO & intravasc. fluid vol.
What cardiovascular parameter does not change during pregnancy?
CVP = no change
How much does uterine BF increase by term?
Uterine BF increases from 50ml/min to 700-900ml/min by term.
Autotransfusion and 24 ven. return is associated with?
Uterine involution→ ven return of blood. (returning to its pore-pregnant size & state)
How much does erythrocyte (RBC) volume increase?
~20-30%
How much does plasma volume increase?
~45%
4 other cardiovascular changes inpregnancy?
↑ HR ↑ CO ↑ heart size ↑ peripheral ciurculation
Increased CO is do to what?
↑ SV (preload) ↑ HR
# 1 cardiovascular change in pregnancy?
↑ intravascular volume
How does the hear ↑ in size?
↑ volume, ↑ stretch and force of contraction & ↑ ize of myocytes.
Why does SVR and PVR ↓ during pregnancy?
↓ in vessel tone d/t Alpha and Beta receptor down regulation & proticyclin changes → ↑ renal, uterine, & extremity BF.
What causes vessel tone to ↓ during pregnancy?
Alpha & Beta receptor down regulation and prostocyclin changes that result in ↑ renal, uterine, and extremity BF. = CVP no change
Net effects of ↑ CO, ↓SVR & ↓ PVR?
Art. BP remains normal or slt. ↓ during uncomplicated preg (DBP ~10-20 mmHg)
Why does the parturient have hemodilution?
Blood vol. increases more then RBCs increase.
When is CO greatest?
Emmidiately after delivery. As mus as 80% above prelabour val. -d/t autotransfusion & ↑ ven. return returns to normal slowly over 14 days
How does anemia result with an increased RBCs?
Hemodilution Anemia results from: ↑ in plasma vol : ↑ RBC vol.
What does an ECHO reveal about the ↑ heart during pregnancy?
LVH by 12 weeks with 50% ↑ mass by term. 94% at term exhibit tricuspid and pulmonic regurge 27% MR
Is O2 transport ↑ or ↓ during pregnancy?
Lower HCT ↓ O2 carrying capacity (19.5 to 16 vol/100ml) but.. COmpensated by ↓ ventililation (avg. O2 tension is 103torr) ↑ CO Vasodilation of uterus and kidneys Vasodilation = ↑ BF to target organs
Cardiovascular changes during pregnancy: DECREASES
MAP. ↓15 mmHg SBP. ↓ 0-15 mmHg DBP. ↓ 10-20 mmHg SVR. ↓ 20% PVR. ↓ 35%
