Pregnancy Induced Hypertension

1. Pregnancy Induced Hypertension Jack Lin, M.D. Albert Woo, M.D. Advisor: Marissa Lazor, M.D. Boston University Medical Center Dept. of Anesthesiology

2. Hypertension • Most common medical problem encountered during pregnancy • 8% of pregnancies • 4 categories: • Chronic Hypertension • Pregnancy Induced hypertension • Preeclampsia-eclampsia • Preeclampsia superimposed on chronic HTN *Hypertensive disorder in pregnancy may cause an increase in maternal and fetal morbidity and remains a leading source of maternal mortality*

3. Hypertension • Third leading cause of maternal mortality, after thromboembolism and non-obstetric injuries • Maternal DBP > 110 is associated with ↑ risk of placental abruption and fetal growth restriction • Superimposed preeclampsia cause most of the morbidity

4. Pregnancy Induced Hypertension • HTN • Usually mild and later in pregnancy • No renal or other systemic involvement • Resolves 12 wks postpartum • May become preeclampsia

5. Preeclampsia • New onset HTN • After 20 weeks of gestation, or • Early post-partum, previously normotensive • Resolves within 48 hrs postpartum • With the following (Renal or other systemic) • Proteinuria > 300 mg/24hr • Oliguria or Serum-plasma creatinine ratio > 0.09 mmol/L • Headaches with hyperreflexia, eclampsia, clonus or visual disturbances • ↑ LFTs, glutathione-S-Transferase alpha 1-1, alanine aminotransferase or right abdominal pain • Thrombocytopenia, ↑ LDH, hemolysis, DIC • 10% in primigravid • 20-25% with history of chronic HTN

6. Maternal Risk Factors • First pregnancy • Age younger than 18 or older than 35 • Prior h/o preeclampsia • Black race • Medical risk factors for preeclampsia - chronic HTN, renal disease, diabetes, anti-phospholipid syndrome • Twins • Family history

7. Mild vs. Severe Preeclampsia

8. Etiology Exact mechanism not known • Immunologic • Genetic • Placental ischemia • Endothelial cell dysfunction • Vasospasm • Hyper-responsive response to vasoactive hormones (e.g. angiotensin II & epinephrine)

9. Symptoms of preeclampsia • Visual disturbances • Headache • Epigastric pain • Rapidly increasing or nondependent edema - may be a signal of developing preeclampsia • Rapid weight gain - result of edema due to capillary leak as well as renal Na and fluid retention

10. Pathophysiology

11. Pathophysiology • Airway edema • Cardiac • Renal • Hepatic • Uterine

12. Upper airway edema • Upper airway edema • Laryngeal edema • Airway obstruction • Potential for airway compromise or difficulty in intubation

13. Cardiac/Pulmonary • Increased CO & SVR • CVP normal or slightly increased • Plasma volume reduced • Pulmonary edema • Decrease oncotic/collid pressure • Capillary/endothelial damage  leak • Vasoconstriction •  increase PWP and CVP • Occurs 3 % of preeclamptic patients

14. Hepatic • Usually mild • Severe PIH or preeclampsia complicated by HELLP  periportal hemorrhages ischemic lesion generalized swelling hepatic swelling  epigastric pain

15. Renal • Adversely affected  proteinuria • GFR and CrCl  decrease • BUN increase, may correlate w/ severity • RBF compromised • ARF w/ oliguria – PIH, esp. w/ abruption, DIC, HELLP *Oliguria + renal failure may occur in the absence of hypovolemia. Be careful w/ hydration  pulmonary edema*

16. Uterine • Activity increased • Hyperactive/hypersensitive to oxytocin • Preterm labor – frequent • Uterine/placental blood flow – decreased by 50-70% • Abruption – incidence increased

17. Morbidity / Mortality Maternal complications: • Leading cause of maternal death in PIH is intracranial hemorrhage • Seizures • Pulmonary edema • ARF • Proteinuria • Hepatic swelling with or without liver dysfunction • DIC (usually associated with placental abruption and is uncommon as a primary manifestation of preeclampsia)

18. Morbidity / Mortality Fetal complications: • Abruptio placentae • IUGR • Premature delivery • Intrauterine fetal death

19. HELLP Syndrome • Hemolysis • Elevated Liver enzymes • Low Platelets • < 36 wks • Malaise (90%), epigastric pain (90%), N/V (50%) • Self-limiting • Multi-system failure

20. HELLP Syndrome • Hemostasis is not problematic unless PLT < 40,000 • Rate of fall in PLT count is important • Regional anesthesia - contraindicated  fall is sudden • PLT count  normal within 72 hrs of delivery • Thrombocytopenia may persist for longer periods. • Definitive cure is delivery

21. Treatment • Management of maternal hemodynamics & prevention of eclampsia are key to a favorable outcome • MgSO4 - Rx of choice for preeclampsia. • Does not significantly reduce systemic BP at the serum concentration that are efficacious in treating preeclampsia • Goals • Control BP • Prevent seizures • Deliver the fetus

22. Controlling the HTN • Hydralazine • Labetalol • Nitroglycerin • Nifedipine • Esmolol • Na Nitroprusside – risk of cyanide toxicity in the fetus

23. Preventing Seizures • MgSO4 - Drug of choice. Narrow therapeutic index • Reduce > 50% w/o any serious maternal morbidity • 4g IV Bolus over 10 minutes, then infusion @ 1g/hr • Renal failure - rate of infusion  by serum Mg levels • Plasma Level should be between 4-6 mmol/L • Monitor clinical signs for toxicity • Toxic:10 ml of 10% Ca Gluconate IV slowly

24. MgSO4 Toxicity • 5-10 mEq/L – Prolonged PR, widened QRS • 11-14 mEq/L – Depressed tendon reflexes • 15-24 mEq/L – SA, AV node block, respiratory paralysis • >25 mEq/L - Cardiac arrest

25. Anesthetic Considerations • Detailed preanesthetic assessment • Focuses on airway, fluid status, and BP control • Lab: CBC, BUN/Cr, LFTs • Routine coagulation is NOT recommended unless there is clinical suspicion • PLT count - if neuraxial techniques are considered

26. Regional Anesthesia • Labor epidural - advantage of a gradual onset of sympathetic blockade  provides cardiovascular stability & avoids neonatal depression. • Epidurals may reduce vasospasm and HTN – may improve uteroplacental blood flow • Reduce risk of airway complications and avoid hemodynamic alterations associated with intubation

27. Regional (part 2) • Neuraxial anesthesia in preeclamptic pt - still controversial • Many studies  this is the best option • National High blood Pressure Education Program Working Group • “Neuraxial, epidural, spinal and combined spinal-epidural (CSE), techniques offer many advantages for labor analgesia and can be safely administered to the parturient with preeclampsia. Dilute epidural infusions of local anesthetic plus opioid produce adequate sensory block without motor block or clinically significant sympathectomy. “

28. Regional (part 3) • Possibility of extensive sympatholysis with profound hypotension •  decrease CO & uteroplacental perfusion • Single shot spinal technique  controversial • Recent analysis suggest that it can be used safety in pt with severe preeclampsia undergoing C-section. BP decline similar to epidural. Hypotension can be avoided by meticulous attention to anesthetic technique and careful volume expansion

29. General Anesthetic Techniques • Laryngeal response  blunted by pre-treatment with hydralazine, nitroglycerin or labetalol • Airway edema  increased risk of difficult airway situation • Neuraxial techniques  preferred method, contraindicated in the presence of coaguloapthy • In pt receiving MgSO4, SUX activity potentiated • Enhancedsensitivity to non-depolarizing muscle relaxants • MgSO4blunts response to vasconstrictors and inhibits catecholamine release after sympathetic stimulation

30. Thank You!