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Respiratory Changes

Respiratory Changes. Oxygen consumption increase 25-35%  100% in labor Minute ventilation ↑ in excess of CO2 mainly due to increased TV not RR tachypnea is considered abnormal sign Increased incidence of atelectaisis. ABG Changes. Causes of Acute Hypoxia.

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Respiratory Changes

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  1. Respiratory Changes • Oxygen consumption increase 25-35% 100% in labor • Minute ventilation ↑ in excess of CO2 mainly due to increased TV not RR tachypnea is considered abnormal sign • Increased incidence of atelectaisis

  2. ABG Changes

  3. Causes of Acute Hypoxia • Preeclampsia / Eclampsia & HELLP • Hemorrhage with massive transfusion • Amniotic fluid & Air embolism • Pneumonia • Pulmonary edema ( cardiogenic + tocolytic )

  4. Anticipated Intubation Risks • Airway  edema & hyperemia potential need of small ETT • Aspiration  delayed gastric emptying &relaxed GE sphincter • Limited reserve  High VO2 & decreased FRC

  5. Asthma & Pregnancy • Variable course 33% no change 35% worsening 28% improvement. • Interpretation of PaCO2 in light of physiologic changes  pre existing respiratory alkalosis • CXR with shielded abdomen is safe when needed • Poorly controlled asthma during pregnancy has adverse outcome on fetus

  6. Asthma & Pregnancy • Treatment strategy is the same for non pregnant • Inhaled bronchodilator systemic steroid • Theophyline should be reduced in 2nd & 3rd TM  lower protein binding and higher free drug • In prolonged systemic steroid use  stress dose should be given peripartum

  7. NIPPV In Pregnancy • 4 patients with acute chest syndrome (complication of sickle cell anemia) • Acute Hypoxemia PaO2/FIO2 < 200 • Received PSV in addition to standard Rx of Acute chest syndrome • None required intubation , ICU stay was shorter than matched cases who were intubated Al Ansari Annals of Thoracic Medicine 2007

  8. ARDS & Mechanical Ventilation • Low tidal volume ventilation study excluded pregnant Hypercapnia harm on fetus • Airway pressure might be high due to the compression of gravid uterus & not necessarily related to lung disease

  9. VTE & Pregnancy • Incidence 0.5-1% • Highest cause of mortality 1-30% • 2 risk factors Hypercoagulopathy hormonal mediated Stasis ( compressive effect of gravid uterus) • Most common site Lt Ileo-femoral vein  US a less sensitive test than in non pregnant • Radiation dose of venography is <500 mcGY (very small risk in case of high clinical suspicion)

  10. VTE & Pregnancy • D-dimer can be high up to four fold in normal pregnancy  can not be used Morse Thromb Haemost 2004 • Fetal radiation exposure of CXR + V/Q & CTA  <5000 mcGy This is 100 to 200 times < dose thought to produce a significant risk of fetal anomalies.

  11. Utility Of VQ Scan • 113 pregnant with suspected PE had VQ scan 73% had normal scan 24% non diagnostic test VQ utility is much higher than non pregnant • No Rx given for both groups • No evidence of VTE in follow up of 20 months even in the non diagnostic • No evidence of radiation effect on fetal outcome Chan Archive of Int Med 2002

  12. VTE RX • During pregnancy either UFH IV for few days then replace by LMWH or start with LMWH • May need larger bolus of UFH • IF LMWH to be used monitoring with level of anti Xa • Comadin can be used between GA 13 w till mid 3rd TM The 7th ACCP Guidelines 2004

  13. Risk Of Stroke & Venous Thrombosis • Retrospective review of Us delivery registry • 1 500 000 chart reviewed • Estimated stroke risk 13.1/100 000 • IC venous thrombosis11.6 /100 000 • Predisposing factors  C section HTN electrolytes & Acid base disturbances Odds Ratio >3 Lanska Stroke 2000

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