Transcript Slide 1
Leanna R. Miller, RN, MN, CCRN-CMC, PCCN-CSC, CEN, CNRN, Education Specialist LRM Consulting Nashville, TN CMSRN, NP Objectives Identify the 5 criteria for the diagnosis of ARDS. Discuss the common etiologies that lead to ARDS. Describe the priorities in the management of patients with ARDS. diffuse lung injury resulting in noncardiogenic pulmonary edema due to increase in capillary permeability • • • • • refractory hypoxemia diminished compliance diffuse infiltrates on chest x-ray normal PAOP PaO2 / FiO2 ratio < 200 • Etiology – shock – trauma – infections – inhaled toxins • Etiology – aspiration – near-drowning – massive blood transfusions – fat or amniotic fluid emboli – pancreatitis • Phase I & II – subclinical respiratory distress – ABGs (respiratory alkalosis) – hyperventilating • Phase III – established respiratory distress – pulmonary shunt > 10% above baseline – chest x-ray shows infiltrates – crackles in lung bases • Phase IV – severe respiratory failure – rising pCO2 – rising physiologic shunt – white-out on chest x-ray • Diagnosis – history – signs/symptoms – labs (ABGs) – x-ray – hemodynamics • Treatment – establish patent airway – restore arterial O2 level • Mechanical Ventilation – conventional with PEEP – PC / IRV – HFJV – APRV • Goals of mechanical ventilation in ARDS are to: – maintain oxygenation – avoiding oxygen toxicity and the complications of mechanical ventilation • maintain oxygen saturation in the range of 85-90% • aim of reducing the fraction of inspired oxygen (FIO2) to less than 60% within the first 24-48 hours • usually requires the use of moderate-to-high levels of PEEP • experimental studies have shown that mechanical ventilation may promote a type of acute lung injury (ALI) termed ventilatorassociated lung injury • protective ventilation strategies using low tidal volumes and limited plateau pressures improves survival when compared with conventional tidal volumes and pressures • ARDS Network study – patients with ALI and ARDS were randomized to mechanical ventilation • tidal volume of 12 mL/kg of predicted body weight and an inspiratory pressure of 50 cm water or less • tidal volume of 6 mL/kg and an inspiratory pressure of 30 cm water or less • the study was stopped early after interim analysis of 861 patients demonstrated that subjects in the low-tidal-volume group had a significantly lower mortality rate (31% versus 39.8%) • mechanical ventilation with a tidal volume of 6 mL/kg predicted body weight is recommended, with adjustment of the tidal volume to as low as 4 mL/kg if needed to limit the inspiratory plateau pressure to 30 cm water or less • increase the ventilator rate and administer bicarbonate as needed to maintain the pH at a near normal level (7.3) • High-frequency ventilation uses low tidal volumes and high respiratory rates. • diminishes alveolar distention • compared to conventional ventilation in adults demonstrates early improvement in oxygenation but no improvement in survival. • Fluid Management – maintain adequate perfusion – isotonic solutions – fluid restriction – consider diuretics • primary ARDS due to aspiration, pneumonia, or inhalational injury treated with fluid restriction • secondary ARDS due to remote infection or inflammation requires initial fluid and potential vasoactive drug therapy • essential in directing initial treatments to stabilize the patient • Improve systemic O2Delivery – modest volume expansion – vasopressors/vasodilators • Sedation – control anxiety & physical activity – may require addition of neuromuscular blocker – suggestions: • propofol • versed • Positioning – “good lung” in dependent position – both lungs are equally injured – beneficial positions include: • prone • right lung down • 60-75% of patients with ARDS have significantly improved oxygenation when turned from the supine to the prone position • improvement in oxygenation is rapid and often substantial enough to allow reductions in FiO2 or level of CPAP • Possible mechanisms for improvement are: – recruitment of dependent lung zones – increased functional residual capacity (FRC) – improved diaphragmatic excursion – increased cardiac output – improved ventilation-perfusion matching • despite improved oxygenation with the prone position, randomized controlled trials of the prone position in ARDS have not demonstrated improved survival • Pharmacologic Therapy – corticosteroids – antimicrobials – non - steroidal anti inflammatory agents – anti – pyretic – “Star – Trek Meds” • No drug has proved beneficial in the prevention or management of acute respiratory distress syndrome (ARDS). • Hemoglobin – 12 to 15 gm / dL – factors decreasing offloading: • hypophosphatemia • alkalosis • hypothermia • Nutritional Support – often overlooked in ARDS – ingredients required: • stress amino acid • trace elements • omega 3 / omega 6 – Oxepa or Impact • patients who required mechanical ventilation within 48 hours of developing acute lung injury received either trophic or full enteral feeding for the first 6 days • Initial lower-volume trophic enteral feeding did not improve – ventilator-free days – 60-day mortality – infectious complications – it was associated with less gastrointestinal intolerance • Other Therapeutics – nitric oxide – surfactant – ECMO – partial liquid ventilation Extracorporeal Membrane Oxygenation (ECMO) • Description – type of cardiopulmonary bypass – CO2 removal; O2 replacement – ventilated (lower VT, FiO2, & PEEP) Extracorporeal Membrane Oxygenation (ECMO) • Complications – technical difficulties – cannula malposition – hemorrhage – sepsis • ECMO appeared to improve survival in patients with H1N1-associated ARDS who could not be oxygenated with conventional mechanical ventilation • randomized controlled trial that compared partial liquid with conventional mechanical ventilation – partial liquid ventilation resulted in increased morbidity • pneumothoraces • hypotension • hypoxemic episodes – trend toward higher mortality Case Study 48 - year old alcoholic with GI bleed & pancreatitis severe epigastric pain, acute abdomen ultrasound confirms enlarged, edematous pancreas hemodynamically unstable refractory hypoxemia Case Study HR 130 BP 80 / 50 / 62 Case Study HR 130 BP 80 / 50 / 62 CI 2.2 PAP 15 / 8 / 10 PAOP / CVP 2 / 1 Case Study PVRI 290 SVRI 2218 SVI 28 LVSWI/RVSWI 22.8 / 2.6 Case Study ABGs (.70 FiO2) pH 7.38 pCO2 45 pO2 50 SaO2 .83 HCO3 27 SvO2 60% Case Study PaO2 / FiO2 Ratio (P/F) • 50 / .70 • 71 Normal = > 300 ALI = < 250 ARDS = < 200 Case Study Laboratory Values Na 150 Cl 96 Hgb / Hct 12.1 / 36.3 CO2 26 Case Study Anion Gap • Na – (CO2 + Cl) • 150 – (96 + 26) • 28 (Normal = 12 – 15) PEEP can DOI2 WOB VOI2 triggers inflammatory response maldistributed blood flow VOI2 ideal Hgb is 12 DOI2 until VOI2 plateaus Case Study DOI2 = CI ( 1.38 x Hgb x SaO2) 10 2.2 X 1.38 X 12.1 X 0.83 x 10 305 mL/min/m2 (normal = 360 - 600 mL/min/m2) Case Study VOI2 = CI X 1.38 X Hgb X (SaO2 - SvO2) X 10 2.2 x 1.38 x 12.1 x (.83 - .60) x 10 84 mL/min/m2 (Normal 220 - 290 mL/min/m2) In Summary • 6 P’s of ARDS Management – – – – – – Pathophysiology Prevention Positive Pressure Ventilation Perfusion Pharmacology Positioning