Case 55 - pre-eclampsia

Question 1

What is classified as HTN during pregnancy? what is the difference betewen chronic htn, pre-eclampsia, eclampsia, gestational htn?

Answer 1

HTN

• systolic BP > 140
• diastolic BP > 90

chronic htn

• htn before 20 weeks

gestational htn

• htn manifests after 20 weeks with NO symptoms

pre-eclampsia

• htn manifests after 20 weeks + proteinuria
• mild vs severe pre-eclampsia

elcampsia

• pre-eclampsia + seizures

Question 2

what is the difference between mild vs severe pre-eclampsia?

Answer 2

Mild pre-eclampsia

• systolic > 140 or diastolic > 90
• protienuria > 0.3 mg over 24 hours

severe pre-eclampsia

• systolic > 160 or diastolic > 110
• proteinuria > 5 g over 24 hours
• headache
• epigastric pain
• HELLP
• renal failure
• visual distubances

Question 3

what is the pathophysiology behind pre-eclampsia?

Answer 3

• abnormal implantation of placenta
• leads to poor perfusion of uterus and placenta (uteroplacenta ischemia)
• uteroplacenta ischemia results in inappropriate release of vasoactive mediators
• imbalance between thromboxane and prostacyclin balance
  
  • increase thromobxane leads to vasoconstriction, platelet aggregration, and decrease uterine blood flow

Question 4

what systemic changes occur with pre-eclampsia?

Answer 4

Overall

• pre-eclampsia assoc with systemic vasospasm
• assoc with inc aldosterone
  
  • sodium and water retention -> generalized edema

CNS

• cerebral edema, cerebral vasospasm
• seizures, blindness, n/v
• cerebral hemorrhage - leading cause of death in pre-eclamptic pts

Pulm

• difficult intubation 2/2 laryngeal and upper airway edema
• pulm edema -> pulm capillary leak -> A-a gradient

CVS

• HTN
• LVH - > diastolic dysfunction
• 3rd spacing -> relative hypovolemia

Renal

• decrease RBF and GFR

Hepatic System

• subscapsular hemorrhage
• vasospasm of hepatic A -> decrease liver flow -> abnormal LFTs

Heme

• HELLP
• thrombocytopenia
• DIC

uterolplacental

• IUGR
• placental abruption
• premature labor

Question 5

what is managemnt of pre-eclampsia?

Answer 5

control disease, prevent progression to eclampsia

• bed rest
• Left uterine displacement
• coag studies, LFTs, Renal studies
• constant monitor of fetal and materal well being
• admin MgSo4
  
  • helps prevent eclampsia
  • therapeutic 4-8 mEq/L
• definitive tx = delivery of fetus
  
  • do if fetal distress
  • do if mom becomes eclamptic or worsening pre-eclampsia

Question 6

Why is MgSo4 used in pre-eclampsia, what are other properties seen with MgSo4?

Answer 6

MgSo4

• first line therapy for prevention of eclampsia

Properties

• CNS depressant
• anticonvulsant
• Muscle relaxation via NMJ
  
  • potentiates NMBDs
  • inhibit AcH releaes
  • decrease AcH receptor sensitivity at NMJ
• vasodilator -> hypotension
• uterine relaxation
• crosses placenta -> neonatal depression, apnea, dec muscle tone
• toxicity treated with Calcium

Question 7

how much mgso4 do you give as loading dose, what infusion rate do you run, when do you see loss of DTR, resp arrest, cardiac arrest?

Answer 7

MgSo4 admin

• loading dose 2-4g over 15 min
• mainteance 1-3g /hr
• monitor signs of toxicity:
  
  • EKG changes (widened QRS, prolong PR)
  • loss of DTR

Mg plasma levels and systemic effects (meq/l)

• therapeutic = 4-8
• EKG changes = 5-10
• Loss of DTR = 10
• Resp arrest = 15
• cardiac arrest = 25

Question 8

why is it important to control HTN in pre-eclamptic patients? What is your BP goal? what agents will you use?

Answer 8

Cerebral Hemorrhage

• leading cause of death in pre-eclamptic pts
• CONTROL BP to prevent this

BP goal

• do not acutely decrease BP
  
  • may decrease uteroplacental flow
  • cerebral ischemia 2/2 right shift of autoreg curve
• tx to w/i 20% of baseline

Agents (acute vs non-acute control)

Non-acute control

• hydralazine - Most commonly used
• labetolol
  
  • do not use in reactive airway dz

Acute Control

• SNP -
  
  • risk of cyanide toxicity in neonate (SNP crosses placenta)
• NTG - minimal effects on fetus

Question 9

what benefits will an epidural provide for pre-eclamptic patients? Prior to placing an epidural, what important things do you need to look for, specifically for pre-eclamptic patients?

Answer 9

epidural benefits for pre-eclamptic patients

• pain control
  
  • reduce hyperventilation -> better uteroplacental blood flow
  • decreaes catecholamine release -> better uteroplacental blood flow
• avoid need for general anesthesia
  
  • avoid difficult intubation
  • avoid risk of maternal aspiratoin

considerations for epidural placement & pre-eclampsia

assess following before epidural placement:

1) diastolic < 110 mm Hg

2) intravascular repeltion

• pre-eclamptic pts typically fluid-depleted (3rd spacing, proteinuria)

3) COAG STUDIES

• risk for DIC
• thrombocytopenia
• HELLP

Question 10

what would be your anesthetic plan for a pre-eclamptic patient undergoing elective c/s and emergent c/s?

Answer 10

Elective C/S

• assuming coag studies normal & BP under control, neuraxial anesthesia = safest option
  
  • avoid difficult intubation
  • avoid maternal aspiratoin
  • avoid BP increase with laryngoscopy -> risk of cerebral hemorrhage

Emergent C/S

• dose pre-existing epidural to surgical anes
• no epidural, then General Anesthesia
  
  • less prepartory time

General Anes

• Control BP before induction even if emergent c/s
  
  • decrease symp stim with laryngoscopy -> risk of cerebral hemorrhage
• anes machine set up with emergent drugs, emergent airway equip, suction, various blades, handles, ETTs
• GET HELP!
• RSI&I
  
  • pre-oxygentate
  • glidescope, suction, emergent meds on stand by
  • cricoid pressure

Question 11

do you stop MgSo4 after delivery of fetus to help with uterine relaxation, do you stop after completion of c/s?

Answer 11

MGSo4 should be continued for at least 24 hrs after surgery

patient still at risk for eclampsia post-partum