Anesthesia and the Preeclamptic Patient clb 09-09-09.pptx

Anesthesia and pre eclamptic patient

1. Anesthesia and the Preeclamptic Patient Curtis L. Baysinger, MD Vanderbilt University School of Medicine

2. Introduction Affects 4% of US births: 10% (?) in Africa Rates are rising: 47% ↑ in US from 1990 – 2005 Smaller increase in Latin America, Africa 3 rd Leading cause of maternal mortality in US Fetal complications: IUGR, Preterm birth Uniquely human: Research limited by lack of animal model

3. Definitions Recent widespread international acceptance: Gestational hypertension (↑BP > 20 wks; resolves 12 wk) Preeclampsia (new BP > 140/90 and proteinuria > 20 wk) Mild Severe Chronic hypertension (prepartum BP≥140/90 that persists) Chronic hypertension with super imposed preeclampsia Proteinuria = 300mg/24 h; 1+ on dipstick

4. Definitions Severe preeclampsia: End organ damage present BP ≥ 160/110 mmHg Proteinuria > 5gm/24h; oliguria: ↑ serum creatinine CNS symptoms (headache, visual changes) HELLP syndrome( H emolysis; El v L FT’s: L ow P latelets) Epigastric, RUQ pain Eclampsia: Etiology: Vasoconstriction/vasogenic edema → ischemia Primarily pre/intrapartum; <40% occur post partum

5. Risk Factors Disease of nulliparas Prior history # 1 risk factor Limited maternal exposure to sperm antigens Men with 1 preeclamptic pregnancy, 2x ↑ likely for another Age, family hx , placental abruption, IUGR, African Obesity, metabolic syndrome, diabetes, thrombophilia Cigarette smoking (↓ relative risk to 0.68 in one review) Multiple gestation, increased trophoblastic mass

6. Pathogenesis Maternal syndrome w or w/o fetal syndrome Divide syndrome into 2 broad groups 75% cases are mild (Type II: onset > 34 wk) Placental interaction with women predisposed to disease Women with HBP, obesity, diabetes Type I: onset < 34 wk High rate of recurrence Clear genetic component Begins early with abnormal placental implantation Multiple diseases with differing mechanisms

7. Pathogenesis Platelet factors Platelet activation→ ↓prostacyclin and ↑ thromboxane Activates renin-angiotensis-aldosterone: ↑ BP Platelet deposition →organ ischemia, coagulopathy, endothelial damage Final common pathway Endothelial damage → HBP, glomerular damage, ischemia

8. Pathogenesis

9. Prophylaxis All trials of prophylactic therapy have failed Low dose aspirin trial (CLASP) to alter prostacyclin/thromboxane activity Calcium supplementation Antioxidant supplementation (Vitamin C & E)

10. Pathophysiology What physiologic changes should we worry about? Airway edema (oropharyngeal and subglottic): More difficult mask airway, small ET’s More diffcult intubation; small endotracheal tubes Exaggerated responses to sympathetic stimulus Endotracheal intubation hazardous Response to vasopressors accentuated

11. Pathophysiology Reduction in plasma oncotic pressure Pulmonary edema Decreased intravascular plasma volume (up to 40% ↓) Hemoconcentration Ongoing consumptive coagulopathy Decreased platelet count (30%) and function Coagulation factor decrease sign of advanced disease

12. Pathophysiology Untreated preeclampsia is a hyperdynamic state LV function is ↑, SVR ↑, cardiac pressures (CFP) ↔ Progression over time for LV fxn to ↓; CFP ↑ Signs of LV failure portends great maternal risk Increased vascular permeability Excess fluid administration is not well tolerated Decreased uteroplacental perfusion Fetal environment less likely to tolerate hemodynamic change

13. Obstetric Management Delivery is the only definitive therapy Principles of management Mild: Surveillance as outpat. w/o seizure prophylaxis Severe Close maternal/fetal monitoring in hospital (Doppler studies) Treat ment of hypertension Seizure prophylaxis Plan for delivery Corticosteroids for fetal lung maturation

14. Obstetric Management Seizure prevention Magnesium superior to phenytoin, nimodipine MAGPIE trial (2002) Mg 2+ markedly ↓ seizures ↑postpartum hemorrhage, ↑ resp. depression, no ∆ neonate How Mg prevents seizures is unknown BP Control Hydralazine, labetelol both safe and effective Nifedipine: Watch for interactions with Mg 2+ Esmolol: Fetal bradycardia reported

15. Obstetric Management Treatment techniques vary Khedun et. al. S Afr Med J 90: 156, 2000 Seizure Prevention/Treatment IM Mg 2+ (89% of respondents) IV Diazepam to Rx eclampsia (60% of respondents) 10% of respondents: No anti-seizure prophylaxis HBP Treatment Mild: PO methyldopa Severe: IV dihydralazine (64%), methydopa (23%)

16. Anesthetic Management Pre anesthesia evaluation Airway examination Cardiac or pulmonary compromise? Intravscular volume status (urine output) Labs: LFT’s, creatinine, platelet count Invasive monitoring: infrequently indicated in US CVP measurements do not correlate to cardiac dynamics PA catheters do not improve outcome Insertion is not a benign procedure

17. Anesthetic Management Neuraxial analgesia Associated with good outcomes Improves utero-placental blood flow Blood pressure response to pain attenuated Stress related hormones decrease General anesthesia for C-section avoided

18. Anesthetic Managment Analgesia management similar to normal except for: Coagulation status: Thrombocytopenia PC ≥ 75,000 adequate: < 50,000 contraindicated There is a platelet defect: significance ? Review of epidural hematoma cases reasssuring Most with heparin use; Only one case of epidural hematoma 66% of cases associated with catheter removal Intravenous hydration Severe preeclampsia: More careful titration of vasopressor Epinephrine use?

19. Anesthetic Management CNS bleed leading cause of death: 2003-5 CEMACH Epidural anesthesia historically optimal technique Hodgkinson et. al. Can Anaesth Soc J 27: 389, 1980

20. Anesthetic Management Spinal anesthesia is safe and appropriate Severely preeclamptic women had less hypotension than healthy women (17% vs. 53%) Aya et. al. A&A 97: 867, 2003 Preeclamptics had less hypotension (RR 0.6) compared to preterm pregnancies Aya et. al. A&A 101: 869, 2005

21. Anesthetic Management Beware the side effects of Mg 2+ Increases potency, duration of non-depolarizers Does not appear to significantly affect 1 dose sux. Expect that oxytocin will be less effective (carboprost?) Hemorrhage may be increased Can have significant interactions with Ca 2+ blockers

22. Anesthetic Management Use general anesthesia for: Coagulopathy Pulmonary edema Severe fetal stress with a reassuring airway exam Make a plan in case of failed intubation Attenuate blood pressure responses to laryngoscopy Labetelol probably the drug of choice Esmolol, nitroglycerine, nitroprusside, remifentanil have all been trialed