Pathophysiology of Obstetric Disorders Flashcards
How is chronic hypertension defined in the obstetric patient?
Occurs before 20 weeks gestation
Does not return to normal after delivery
What is gestational hypertension?
Develops after 20 weeks gestation
Proteinuria does not occur
Return to normotensive state after delivery
What is preeclampsia?
Hypertension that develops after 20 weeks gestation
Proteinuria typically present
If proteinuria is not present, any of the following conditions are indicative of preeclampsia:
Persistent RUQ or epigastric pain
Persistent CNS or visual symptoms
Fetal growth restriction
Thrombocytopenia
Elevated serum liver enzymes
What is eclampsia?
The mother with preeclampsia develops seizures
How does healthy placental implantation compare to that of a preeclamptic patient?
Healthy placenta produces equal amounts of thromboxane and prostacyclin
Preeclamptic patient’s placenta produces up to seven times more thromboxane than prostacyclin. It also produces a variety of cytokines.
How do increased levels of thromboxane affect the placenta?
Thromboxane increases:
Platelet aggregation
Vasoconstriction
Uterine activity
and decreases:
Uteroplacental bloodflow
What are major potential consequences of preeclampsia?
Proteinuria
DIC
Intracranial hemorrhage/ cerebral edema
Heart failure/ pulmonary edema
What are the blood pressure parameters for mild preeclampsia?
<160/ <110 mmHg
What are the blood pressure parameters for severe preeclampsia?
> = 160/ >= 110 mmHg
What causes the hypertension seen in preeclampsia?
Vasoconstriction due to thromboxane
What systemic symptoms may be present in severe preeclampsia that are not present in mild preeclampsia?
Decreased urine output
Pulmonary edema
Cyanosis
Headache
Visual impairment
Epigastric pain
HELLP syndrome
What role does thromboxane play in preeclampsia?
Increases vasoconstriction = increases blood pressure
How may preeclampsia affect renal function?
Glomerular capillary endothelial destruction and renal edema may result in proteinuria and decreased urine output
What is the pathophysiology of the generalized edema that may be present in preeclampsia and the pulmonary edema that may occur in severe preeclampsia?
Decreased oncotic pressure
Increased vascular permeability
What is the definitive treatment of preeclampsia and eclampsia?
Delivery of the fetus and placent
At what blood pressure should the preeclamptic parturient receive pharmacologic treatment?
160/110 mmHg
What is the primary reason for treating blood pressure in preeclampsia?
Prevent cerebrovascular accident, myocardial ischemia, and placental abruption
What is the pharmacologic treatment for acute hypertension in pregnancy?
Labetalol 20 mg IV then 40-80 mg q 10 min up to a max dose of 220 mg
Hydralazine 5mg IV q 20 min up to a max dose of 20 mg
Nifedipine 10 mg PO q 20 min up to a max dose of 50 mg
Nicardipine infusion started at 5 mg/hr and titrated by 2.5 mg/hr q 5 min up to a max of 15 mg/hr
How long is the patient at risk for complication related to severe preeclampsia?
Up to 4 weeks into the postpartum period
When is the patient at highest risk for pulmonary hypertension and stroke?
In the postpartum period
How does neuraxial anesthesia impact the preeclamptic patient?
Assists with blood pressure control > better uteroplacental perfusion
What are some anesthetic considerations for the preeclamptic patient?
Rule out thrombocytopenia prior to a neuraxial block
More likely to be a difficult intubation d/t airway swelling
Beta blockers, remifentanil, and Mg++ blunt the hemodynamic response to laryngoscopy
Exaggerated response to sympathomimetics and methergine
What are anesthetic considerations in the preeclamptic patient receiving Mg++?
Increased sensitivity to neuromuscular blockers
Increased risk for postpartum hemorrhage
What is the seizure prophylaxis regimen for eclamptic patients?
Mg++:
Loading dose of 4 g over 10 minutes
Infusion 1-2 g/hr
What is the treatment for Mg++ toxicity?
10 mL of 10% calcium gluconate IV
What does HELLP stand for?
Hemolysis, Elevated Liver enzymes, and Low Platelet count
What are the symptoms of HELLP syndrome?
Epigastric pain
Upper abdominal tenderness
What is the definitive treatment for HELLP syndrome?
Delivery of the fetus
What are risks associated with HELLP syndrome?
DIC
Intra-abdominal bleeding from the liver
When is the patient at risk for developing HELLP syndrome?
Throughout pregnancy, but may present for the first time in the postpartum period
How does cocaine abuse impact the cardiovascular system?
Tachycardia
Dysrhythmias
Coronary vasoconstriciton
Myocardial ischemia
How does cocaine abuse impact the CNS?
Cerebral vasoconstriction
Ischemia
Seizures
Stroke
How does cocaine use affect MAC?
Acute intoxication increase MAC
Chronic use decreases MAC
What are obstetric risks associated with cocaine abuse?
Spontaneous abortion
Premature labor
Placental abruption
Low APGAR scores
How can beta blockade affect the patient acutely under the influence of cocaine?
If SVR is significantly elevated:
Beta-1 blockade (myocardia depressions + Beta-2 blockade (impaired vasodilation in muscular beds) = heart failure
What is the best treatment for hypotension in the patient who is a chronic cocaine abuser?
Phenylephrine- ephedrine may be ineffective d/t catecholamine depletion
What are the best treatment options for a cocaine abuser who is hypertensive?
Labetalol- also blocks alpha-mediated vasoconstriction
Vasodilators- but may cause tachycardia
How might chronic cocaine abuse affect coagulation?
Association with thrombocytopenia = check plt count prior to neuraxial anesthesia
Placenta accreta
Placenta attaches to the surface of the myometrium
Placenta increta
Placenta invades the myometrium
Placenta percreta
Placenta implantation extends beyond the uterus
What is the preferred approach to anesthesia in the setting of abnormal placental implantation?
General anesthesia preferred (although neuraxial anesthesia is considered safe)
What patient history is associated with abnormal placental implantation?
Placenta previa
Prior c-section(s)
Placenta previa
Placenta attaches to the lower uterine segment. It partially or completely covers the cervical os.
What is a sign of placental previa?
Painless vaginal bleeding
What is a complication of placenta previa?
Hemorrhage
What are risk factors of placenta previa?
Previous c-section
History of multiple births
Placental abruption
Partial or complete separation of the placenta from the uterine wall before delivery
Risk factors for placental abruption
Factors that increase the driving pressure to the placenta:
Pregnancy induced hypertension
Preeclampsia
Chronic hypertension
Cocaine use
Smoking
Excessive alcohol use
What are signs of placental abruption?
Painful vaginal bleeding
What are potential complications of placental abruption?
Fetal hypoxia
Amniotic fluid embolism
DIC
What are anesthesia considerations for placental abruption?
Vaginal delivery is possible if the fetus is stable
Obtain large-bore IV access and have blood products available
Prepare for c-section
What is the most common cause of postpartum hemorrhage?
Uterine atony
What are risk factors for postpartum uterine atony?
Multiparity
Multiple gestations
Polyhdraminos
Prolonged oxytocin infusion before surgery
What are causes of obstetric bleeding?
Uterine atony
Retained placenta/ placental fragments
Uterine inversion
Coagulopathy
Placenta previa
Placental abruption
Abnormal placental implantation
What medication should the anesthesia provider anticipate administering for the patient with retained placental fragments?
IV nitroglycerine- provides uterine relaxation for placental extraction
What is the medical management for postpartum hemorrhage?
Uterine massage
Ergot alkaloids
Manual massage
Intrauterine balloon (when other approaches are ineffective)
What conditions are associated with obstetric DIC?
Amniotic fluid embolism
Placenta abruption
Intrauterine fetal demise
