Pregnancy Induced Hypertension

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Pregnancy Induced Hypertension

• Jack Lin, M.D.
• Albert Woo, M.D.
• Advisor Marissa Lazor, M.D.
• Boston University Medical Center
• Dept. of Anesthesiology

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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

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Hypertension

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

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Pregnancy Induced Hypertension

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

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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 gt 300 mg/24hr
• Oliguria or Serum-plasma creatinine ratio gt 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

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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

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Mild vs. Severe Preeclampsia
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Etiology

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

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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

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Pathophysiology
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Pathophysiology

• Airway edema
• Cardiac
• Renal
• Hepatic
• Uterine

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Upper airway edema

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

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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

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Hepatic

• Usually mild
• Severe PIH or preeclampsia complicated by HELLP
• ? periportal hemorrhages
• ?ischemic lesion
• ?generalized swelling
• ?hepatic swelling ? epigastric pain

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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

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Uterine

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

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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)

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Morbidity / Mortality

• Fetal complications
• Abruptio placentae
• IUGR
• Premature delivery
• Intrauterine fetal death

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HELLP Syndrome

• Hemolysis
• Elevated Liver enzymes
• Low Platelets
• lt 36 wks
• Malaise (90), epigastric pain (90), N/V (50)
• Self-limiting
• Multi-system failure

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HELLP Syndrome

• Hemostasis is not problematic unless PLT lt 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

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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

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Controlling the HTN

• Hydralazine
• Labetalol
• Nitroglycerin
• Nifedipine
• Esmolol
• Na Nitroprusside risk of cyanide toxicity in
  the fetus

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Preventing Seizures

• MgSO4 - Drug of choice. Narrow therapeutic index
• Reduce gt 50 w/o any serious maternal morbidity
• 4g IV Bolus over 10 minutes, then infusion _at_
  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

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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
• gt25 mEq/L - Cardiac arrest

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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

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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

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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.

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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

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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
  
• Enhanced sensitivity to non-depolarizing muscle
  relaxants
• MgSO4 blunts response to vasconstrictors and
  inhibits catecholamine release after sympathetic
  stimulation

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Thank You!