Flashcards in Hypertension in Pregnancy Deck (65)
What are the CV adaptations to pregnancy?
-Inc in CO
-Inc in PR
-Decrease in TPR
Alterations in BP
What causes the decrease in TPR during pregnancy?
-Increased production of vasodilatory substances (e.g. prostacyclin)
-Decreased sensitivity to vasopressors e.g. angiotensin II
How does BP change throughout pregnancy?
Mid gestation fall in BP with BP returning to early pregnancy levels by the end of gestation
What are appropriate positions for BP measurement during pregnancy? Why?
Compression of IVC or aorta by gravid uterus leading to artifactually high or low readings.
Why is it suggested dBP be recorded at Korotkoff IV (muffling) rather than V (cessation) during pregnancy?
Hyperdynamic circulation means pulsations may sometimes be heard down to 0mmHg. Most people still recommend K5.
What is HTN in pregnancy defined as?
Greater than or equal to 140/90mmHg or an increase over the pre/early pregnancy baseline reading of 25/15mmHg +.
Why is 170/11mmHg a significant BP level?
Irreversible vascular damage (e.g. CVA) by BP of this level. Anything above this needs prompt anti-hypertensive therapy.
What are the two broad categories of hypertenion in pregnancy?
-Pregnancy induced HTN (PIH) / pre eclampsia
-Pregnancy associated HTN
What are examples of pregnancy associated hypertension?
-HTN renal disease
-Coarctation of the aorta
What is the pattern of pregnancy induced hypertension?
Appears in latter half of gestation, resolves following delivery
What is pre-eclampsia?
-Proteinuria (greater than 300mg per 24h)
What is the incidence of pre-eclampsia?
5-10% of pregnancies
What is the incidence of severe pre eclampsia and how is it defined?
1% of pregnanacies:
What is the hypothesised mechanisms for pre eclampsia?
Postulated genetic defect suggests dysfunction in normal maternal immunological adaptation to present of foreign antigenic load; leads to immunologically mediated dysfunction (possible too few "blocking" antibodies to foetus) so conceptus exposed to mother's immune material.
How is pre eclampsia represented in placental histology?
Deficient placentation with
-failure of trophoblast invasion of maternal placental bed spiral arteries and
-placental bed vascular artherosis
Leads to impaired placental flow and release of disordered factors leading to maternal endothelial cell dysfunction
How does the balance of vasodilator/constrictor substances change in pre eclampsia?
What is the hypothesised mechanism of proteinuria?
Postulated immunodysfunction leading to cross reacting autoantibody formation impacting on sites like the renal glomerulus producing proteinuria
What causes oedema of PE?
Increased capillary permeability
What are the clinical manifestations of organ and system dysfunctions?
-Fetal intrauterine growth retardation
-Grand mal convulsions
What are the causes of serious morbidity and mortality resulting from PE?
What are the histological lesions of PE?
-Spiral artery atherosis in placental bed
-Glomerular endotheliosis on renal biopsy (pathognomonic)
Which conditions increase incidence of PE?
Conditions increasing antigenic load:
-hydrops foetalis complicated pregnancies
What are the RFx for PE?
-Extremes of reproductive age
-New paternity in previously uncomplicated pregnancy Hx
-PHx chronic HTN
-Chronic renal disease
-auto antibody d/os (SLE, APA)
What are the maternal investigations for PE?
-MSU (proteinuria often due to contamination)
-24h urine protein
-Creatinine clearance estimation
-serum urate concentration
-FBE (haemolysis, coagulopathy)
-LFTs (HELLP syndrome)
May need to exclude other causes e.g. phaeo
How does uric acid relate to pre eclampsia and renal function?
Decrease in renal uric acid clearance with consequent increase in serum levels is an early sign of renal dysfunction in PE
Foetal investigations in PE?
-Umbilical arterial blood flow waveform analysis by Doppler
-US for growth
-Admit (day to HDU depending on severity): rest, observation, further assessment
- q4h BP, urinalysis
-Anti HTN BP>140/90
-If severe, CVC for CVP monitoring and fluid / Rx titration
what is the only PE cure?
Emptying uterus of foetus, placenta and membranes
What are the anti-HTN of choice in PE?
-PO methyl dopa ongoing
-IV hydrazine when prompt reduction required
Other inc labetolol, nifedipine, diazoxide