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Causes: HF Permeability edema Both
Most obstetric APE are due to noncardiogenic causes
=5% of ICU admissions =0.5% of deliveries
Study: HF Preeclampsia Fluid overload Tocolytics Infection RF – HF
Tocolytics = 5% of obstetric causes
Commonly associated with: Preeclampsia 28% PTL 24% Fetal surgery 17% Infection 14%
If iatrogenic causes are excluded ,most cases are:
Old
Obese Chronic HTN + superimposed
preeclampsiaPrecipitation factors:
Operative delivery acute blood loss Anemia Infection
Some causes of RF: -Pneumonia - Drug abuse
-Sepsis - Arsenic poisoning
-Hemorrhage - Pancreatitis -Preeclampsia - CT disease
-Embolism - Pheochromocytoma
-Irritant inhalation - Burns
ACUTE RESPIRATORY DISTRESS SYNDROME
=Worst form of RFMortality:
Nonpregnant = 40 – 50% ( ↑ to 90% if + infection ) Pregnant women = 25%
Pathophysiological diagnosis include:
Alveolar epithelial injuries Endothelial injuries
Chemokines neutrophils recruitment ↑ cytokines tissue injury ↑ pulmonary capillary permeability ↓ lung volume ↑ arterial hypoxemia Criteria of diagnosis differ from:
Mild pulmonary insufficiency toTotal mechanical ventilation
Diagnosis: X - ray diffuse infiltrates PaO2 : FiO2 < 200 – 250 No evidence of HF
Most common cause: Nonpregnant = sepsis Pregnant = sepsis 40%
= preeclampsia = hemorrhage
7% of cases are combination of: -Sepsis - Trauma
-Shock - Fluid overloadClinical coarse depend on:
Magnitude of insult Ability to compensate Stage of disease
Very early: Hyperventilation Accentuation of pregnancy metabolic
alkalosis + arterial O2 normalLater on:
X - ray and auscultatory evidence of lung disease ↓ lung compliance
↑ Intrapulmonary blood shunting Progressive alveolar and
interstitial edema Extravagation of WBCs and RBCs
If not diagnosed RF: Marked dyspnea Marked tachypnea Marked hypoxemia
With further ↓ of lung volume: ↓↓ lung capacity ↑↑ intrapulmonary blood
shuntingX–ray and chest auscultation
Bilateral diffuse infiltrationsLethal if not treated with
+ ve airway pressure
Final phase: ↑↑ intrapulmonary shunts ≥ 30% Severe hypoxemia ↑↑ dead space 60% of tidal volume Hypercapnia ( = ↑ CO2 ) Metabolic and respiratory acidosis Myocardial irritability HF
Histology of end stage: Intra-alveolar fibrosis Fibroblastic infiltration Massive tissue plates
Management: O2
Fluids/blood Empirical antibiotics
Points: O2 α CO Increasing PaO2 to 100 – 200 mmHg minimal ↑ of O2 delivery Correction of anemia ↑↑ O2 delivery ( Each 1 gm of Hb carries 1.25 mL O2 when 90% saturated ) Delivery does not improve hypoxia
Goals: PaO2 = 60 mmHg Or 90% oxyhemoglobin
saturation At an inspired O2 content of <
50% With PEEP of < 15 mmHg
Oxygen dissociation curve: Describes the propensity of Hb
molecule to release O2
ODC is divided into: Upper ODC represents alveolar - capillary environment
Low O2 affinity high tissue capillary O2 exchange Lower ODC represents tissue - capillary environment
High O2 affinityPaO2 in maternal alveoli > tissue PaO2
With higher PaO2 in alveoli maternal Hb is maximally saturated
Causes of right ODC shift: Hypercapnia Acidosis ↓ temp ↑ 2,3, diphosphglycerate level ( ↑ 30% during pregnancy ↑ O2
delivery to the mother and fetus )
Fetal Hb is characterized by: ↑ O2 affinity Left shift Constantly in tissue portion of ODC
-At any given PaO2 F Hb carries more O2 # M Hb
-At high altitude maternal PaO2 = 60 mmHg while fetal PaO2 is at sea level
Mechanical ventilation: In early stages O2 mask In immanent RF intubation and artificial ventilation
Adjustment of volume/cycle: PaO2 ≥ 60 mmHg PaCO2 35 – 45 mmHg Hemoglobin saturation 90%
Positive-end-diastolic pressure:For severe pulmonary injury
+high intrapulmonary shunting Filling of collapsed alveoli
5 – 15 mmHg no need for cardiovascular monitoring
15 mmHg ↓ VR ↓ CO ↓ uteroplacental circulation
Close PEEP during measuring PCWP higher results
Other causes of high PCWP: Overdistended alveoli ↓ Compliance Barotrauma
Fluid therapy:Fluid overload worsen lung condition
Daily record: Fluid intake/output Body weight
Mechanical ventilation add 1 L/day ↑Permeability ↑ interstitial fluid
Aim: Lowest PCWP possible + no ↓ CO
Pregnancy changes: ↑ risk of lung injury from fluid therapy
Colloid oncotic pressure ( COP ): Early during pregnancy = 28 mmHg At term = 23 mmHg During puerperium = 17 mmHg Preeclampsia at term = 16 mmHg During puerperium = 14 mmHg COP/PCWP gradient = >8 mmHg COP/PCWP gradient = ≤4 mmHg
↑ risk of pulmonary edema
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