Critical Care in Obstetrics: An Innovative and Integrated Model for Learning the Essentials

Critical Care in Obstetrics: An Innovative and Integrated Model for Learning the Essentials

Respiratory Distress Syndrome and Pulmonary Edema Sonya S. Abdel-Razeq, MD Maternal-Fetal Medicine Surgical Critical Care Assistant Professor Yale School of Medicine New Haven, CT

Disclosure I have no conflicts of interest to disclose

Evidence Outline Learning objectives ARDS Background Diagnosis & Treatment Pulmonary edema Background Diagnosis & Treatment Summary

Learning Objectives Define Acute Respiratory Distress Syndrome (ARDS) Identify causes of ARDS and pulmonary edema Understand diagnostic evaluation and treatment options

ARDS: Background

Case Scenario

35yo G1P0 IVF twin gestation EGA 26w admitted for worsening PNA. Increasing O2 requirement despite appropriate culture guided antibiotic therapy. BMI 38 kg/ m2. What must you be suspicious of? Drug resistant organism Poor med compliance Undiagnosed infection ARDS

ARDS: Background Berlin Definition (2012 task force): Respiratory failure not explained by cardiac failure or fluid overload Occurs within one week of known insult or new/ worsening respiratory symptoms Unexplained bilateral opacities (CXR or CT) Three severity categories based on PaO2/ FIO2 ratio

ARDS: Background 60-day mortality rate: 22% ARDS Network trials: NIH Heart, Lung and Blood Institute Responsible for up to 19% obstetric ICU admissions

ARDS: Pathophysiology Alveolar lung injury causes diffuse alveolar damage Release of pro-inflammatory cytokines Tumor necrosis factor (TNF), interleukin (IL)-1, IL-6, IL-8 Neutrophil recruitment Subsequent damage to capillary endothelium and alveolar epithelium

ARDS: Pathophysiology Protein escapes from vascular space, then oncotic gradient is lost, then air spaces contain proteinaceous fluid and debris Loss of surfactant ARDS effects Impairment of gas exchange Decreased lung compliance Increased pulmonary arterial pressure

What was/were her risk factor(s)? Multiple gestation AMA Pneumonia IVF Obesity

ARDS: Causes More than 60 attributable causes identified Sepsis most common etiology Aspiration One-third of hospitalized that have aspirated Pneumonia Community-acquired pneumonia most common cause outside of hospital Massive transfusion, >15 units red cells Transfusion-related acute lung injury Severe trauma Other: obesity, pancreatitis, contrast, drugs

ARDS: Causes Unique to pregnancy Preeclampsia/ eclampsia Tocolytic-induced pulmonary edema Chorioamnionitis Amniotic fluid embolism Placental abruption Obstetric hemorrhage and resuscitation Endometritis Retained products of conception Septic abortion

ARDS: Stages Exudative stage Day 1 to day 7-10 Alveolar damage http://www.medindia.net/patients/patientinfo/respiratory-distress-syndrome.htm http://commons.wikimedia.org/wiki/file:ards.jpg

ARDS: Stages Proliferative phase Resolution of pulmonary edema Proliferation of type II alveolar cells Fibrotic stage Obliteration of normal lung architecture Diffuse fibrosis Cyst formation

ARDS: Diagnosis & Treatment

ARDS: Diagnosis Hypoxemia appears within 6 to 72 hours of inciting event Dyspnea, cyanosis, and diffuse crackles Rapid progression Diagnosis ARDS versus cardiogenic pulmonary edema Physical exam Brain natriuretic peptide (BNP), < 100 pg/ml Echocardiogram may be helpful

ARDS Chest X-ray

35yo G1P0 IVF twin gestation EGA 26w admitted for worsening PNA. Increasing O2 requirement despite appropriate culture guided antibiotic therapy. BMI 38 kg/ m2. Nonproductive cough. T 99F HR 120 RR 32 BP 110/60 90% (4L) What is your next intervention? Broaden antibiotic coverage and wait for response Oxygen supplementation via nonrebreather facemask Rapid Response Team activation Transfer to ICU and intubate

ARDS: Treatment Supplemental oxygen High flow oxygen, 70% via facemask ARDS usually requires higher concentration Mechanical ventilation

ARDS: Treatment Mechanical Ventilation Low tidal volume ventilation V T 4 to 6 ml/kg predicted body weight (PBW) Plateau pressure < 30 cmh 2 O RR titrated to maintain ph Appropriate fraction of inspired (F IO2 ) and positive endexpiratory pressure (PEEP) No published studies in pregnant women Pre-ARDSnet data suggesting more barotrauma with higher V T

She is now in the ICU. Her mental status has declined and she is unable to protect her airway. Intubation occurs without difficulty. The RT asks for vent parameters. The intensivist, nurse, and RT all look over at you What parameters will you need to specify? Mode of ventilation Respiratory rate FIO2 PEEP All of the above

Key Points: Gravid Patient Respiratory changes in pregnancy 20% increase in O 2 consumption 15% increase in metabolic rate V E increases, RR stable VT increase by 40% over baseline ABG: respiratory alkalosis compensated by metabolic acidosis Stable ph PaCO2: 28 to 32 mmhg

Helpful Definitions Minute Ventilation (V E ) Amount of gas that moves in or out of lung in one minute V T x rate = V E Tidal Volume (V T ) Amount of gas that moves in or out of lung in one breath

Endotracheal Intubation Indicated with inability to maintain airway or adequate oxygenation or ventilation Respiratory rate (RR) > 30/min Inability to maintain arterial O 2 saturation > 90% with FIO2 > 0.60 PCO2 > 50 mmhg with ph < 7.25

Goals Ventilator Settings V E adjusted to maintain PaCO 2 30 to 32 mmhg ph 7.40 to 7.47 PaCO 2 < 30 mmhg may decrease uterine blood flow due to significant respiratory alkalosis

Other Considerations Gravid Patient Permissive hypercapnia Does not appear to adversely affect fetus (CO 2 level 60 mmhg) Positive End-Expiratory Pressure (PEEP) Added to mitigate end-expiratory alveolar collapse, usually 5 cm H 2 O Higher levels may be required in thirdtrimester

Other Considerations Most medications for analgesia, sedation, paralysis reach fetal circulation Analgesia Opioids acceptable, avoid NSAIDs

ARDS: Treatment Permissive hypercapnia (PaCO 2 >60 mmhg) Results from lower V T and minute ventilation Causes vasodilation, tachycardia, hypotension Does not appear to adversely affect fetus Increases uterine vascular resistance No human data regarding permissive hypercapnia in pregnancy

She is now intubated and respiratory status critical but stable. What other interventions are indicated at this time? Bicarbonate therapy PEEP of 2 cm H 2 O Prone positioning Fluid conservative management Corticosteroids

ARDS: Treatment Bicarbonate solution Advocated by some to correct acidosis Placental transfer not well studied Positive End-Expiratory Pressure (PEEP) Mitigate end-expiratory alveolar collapse, usually 5 cm H 2 O May need higher levels in third-trimester Increased intra-thoracic pressure and decreased venous return

ARDS: Treatment Prone positioning Data supports this in refractory hypoxemia to improve oxygenation Not shown to improve overall mortality In pregnancy, meticulous positioning and fetal monitoring required

ARDS: Treatment Appropriate treatment of precipitating event Fluid and hemodynamic management Lowest intravascular volume to maintain adequate tissue perfusion Urine output, acid-base status, CVP monitoring Vasopressors/ inotropes as needed Nutrition Enteral route preferred Corticosteroids Controversial benefit

Fetal Monitoring Best judgement

Pulmonary Edema

Pulmonary Edema: Background Occurs in 0.08% of normal pregnancies Occurs in 3.4% of preeclamptic pregnancies Occurs in 5% preterm labor situations In all affected pregnancies Tocolytic therapy or cardiac disease: 50% Preeclampsia (PEC) or iatrogenic volume overload: 50%

Pulmonary Edema: Risk Factors CATEGORY Prepregnancy conditions Pregnancy-specific diseases Pharmacological agents Iatrogenic volume overload Fetal conditions SPECIFIC RISK FACTORS Cardiovascular diseases Obesity Increased maternal age Endocrine disorders PEC Cardiomyopathy Sepsis Preterm labor Amniotic fluid embolism Pulmonary embolism Beta-agonists Corticosteroids Magnesium sulfate Illicit drugs Multiple gestation

Pulmonary Edema: Presentation Clinical presentation Tachypnea Dyspnea Hypoxemia Tachycardia Diffuse crackles Imaging findings

Pulmonary Edema: Tocolytic Therapy Tocolytic therapy Beta-2 agonists Calcium channel blockers Magnesium sulfate Contributing factors Multiple gestation, maternal infection Simultaneous administration of multiple medications Fluid overload Cardiac dysfunction Capillary permeability

Pulmonary Edema: Tocolytic Therapy No definitive diagnostic tests Diagnosis of exclusion in those receiving tocolytic therapy

Pulmonary Edema: Tocolytic Therapy Treatment Discontinuation of offending agent Supplemental oxygen Fluid restriction Diuresis Mechanical ventilation as necessary

Pulmonary Edema: Cardiogenic 23 per 1,000 deliveries during delivery 11 per 1,000 deliveries during postpartum Due to preexisting or new cardiac disease

Pulmonary Edema: Preeclampsia Uncommon complication Risk factors Older Multigravid In presence of additional organ system dysfunction

Pulmonary Edema: Preeclampsia Multifactorial Etiology Volume overload Decreased plasma oncotic pressure Increased capillary permeability Increased pulmonary capillary hydrostatic pressure

Pulmonary Edema: Diagnosis & Treatment

Pulmonary Edema: Diagnosis Physical exam CXR Blood studies Electrolytes, creatinine, protein Urinalysis Arterial blood gas (ABG)

Pulmonary Edema: Diagnosis EKG Echocardiogram Myocardial, valvular, structural pathologies

40yo G1P0 EGA 34w admitted for superimposed PEC evaluation in the setting of new onset dyspnea, cough and office BP 152/90 mmhg. Bilateral crackles on PE. P 115 BP RR 20 What is your next step? Obtain CXR Expanded history and exam Administer furosemide 40 mg IV Prepare for delivery in light of PEC

Pulmonary Edema http://www.histopathology-india.net/puled.htm Image courtesy Sherif R. Zaki, MD, Ph.D. www.cdc.gov

Pulmonary Edema Chest X-ray (CXR) CT Chest, coronal

Pulmonary Edema: Treatment Treatment Discontinuation of offending agent Treatment of underlying condition Supplemental oxygen Fluid restriction Diuresis Mechanical ventilation as necessary

Summary

Summary Respiratory failure in pregnancy is rare ARDS is a type of respiratory failure, with acute onset of bilateral infiltrates and hypoxemia ARDS causes impaired gas exchange, decreased compliance, increased pulmonary arterial pressure More than 60 possible causes of ARDS have been identified Mechanical ventilation with low V T strategy is standard management

Summary Permissive hypercapnia and increased PEEP may be considered. Pulmonary edema is most often secondary to tocolytic therapy, cardiac failure, severe preeclampsia, or eclampsia. Treatment of respiratory failure involves treatment of the underlying cause, oxygenation/ ventilatory support, sedation, analgesia, volume management, hemodynamic support, nutritional support, DVT prophylaxis.

Summary Acute respiratory failure requiring endotracheal intubation is notable for: respiratory rate (RR) > 30/min inability to maintain arterial O 2 saturation > 90% with FIO 2 > 0.60 (PaO 2 <55 mmhg) PaCO 2 > 50 mmhg with ph < 7.25

Summary Multiple modes of ventilation may be used in pregnancy Ventilator goals for the gravid patient: V E adjusted to maintain PaCO 2 30 to 32 mmhg ph 7.40 to 7.47

Thank You for Your Attention! Planning Committee Mike Foley, Director Shad Deering, co-director Helen Feltovich, co-director Bill Goodnight, co-director Loralei Thornburg, Content co-chair Deirdre Lyell, Content co-chair Suneet Chauhan, Testing Chair Mary d Alton Daniel O Keeffe Andrew Satin Barbara Shaw