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Surgical Intensive Care. Board certified in Anesthesiology Board certified in Critical Care Medicine Board certified in Transesophageal Echocardiography. JUNYI LI, MD. March 31, 2009. lijunyiutmb@yahoo.com. Subspecialty ICU. Medical Intensive Care Unit (MICU) Coronary Care Unit (CCU)
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Surgical Intensive Care Board certified in Anesthesiology Board certified in Critical Care Medicine Board certified in Transesophageal Echocardiography JUNYI LI, MD March 31, 2009 lijunyiutmb@yahoo.com
Subspecialty ICU • Medical Intensive Care Unit (MICU) • Coronary Care Unit (CCU) • Surgical Intensive Care Unit (SICU) • Neurological Intensive Care Unit (NICU) • Cardiovascular Intensive Care Unit (CVICU) • Pediatric Intensive Care Unit (PICU) • Neonatal Intensive Care Unit (NICU)
SICU Admission Criteria • Preoperative status Major trauma Surgical Procedure Pt’s preexisting disease • Intraoperative event Large volume shift Unexpected surgical complication Unexpected anesthesia complication • Postoperative status Unexpected postop complication Pt’s status
Who need to be admitted to SICU ? • 18 y/o health male presented for right inguinal hernia repair under spinal anesthesia and uneventful intraop and postop. • 50 y/o female with controlled HTN and DM for lumbar laminectomy under general anesthesia with EBL 500 ml. • 75 y/o male with stable angina, COPD required home oxygen for TURP under spinal anesthesia • 60 y/o male presented for AAA repair • 54 y/o female with esophageal cancer presented for esophagectomy • 95 y/o female presented for right hip arthroplasty
SICU Management • Respiratory care • Hemodynamic monitoring and management Noninvasive Invasive • Infection in SICU • Acid-base disorders • Fluid and electrolyte disorders • Blood component therapy • Nutrition support
Respiratory care – basic monitor • Respiratory rate • Chest movement • Breath sound • Color
Respiratory care – lung volume • Tidal volume (VT) • Minute ventilation (Vm) • Functional residual capacity (FRC) • Vital capacity (VC)
Respiratory care - ventilation • Ventilation-perfusion (V/Q) ratio: normal V/Q=4L/5L=0.8 • Dead space ventilation: V/Q>1 anatomic dead space & physiologic dead space • Intrapulmonary shunt: V/Q<0.8 true shunt (V/Q=0) and venous admixture
Ventilation-perfusionQuantitative determinations • Dead space (Vd/Vt) = (PACO2 – PECO2)/PACO2 • Shunt fraction (Qs/Qt) = (CCO2 – CAO2)/(CCO2 –CVO2) • A-a gradient (PAO2 – PaO2) PAO2 = PIO2 – (Paco2/RQ) PAO2 = FIO2(PB –PH2O) – (PaCO2/RQ) PAO2 = 0.21(760 – 47) – (40 /0.8) = 100 mmHg • PAO2/FIO2<200, Qs/Qt>20% PAO2/FIO2>200, Qs/Qt<20%
Hypoxemia DisorderA-a PO2PVO2 Hypoventilation Normal Normal Pulmonary disorder Increased Normal DO2/VO2 imbalance Increased Decreased DO2/VO2 – oxygen deliver and uptake ratio A-a PO2 – PO2 difference between alveolar gas and arterial blood PVO2 – Mixed venous PO2
Hypercapnia • Hypercapnia is PACO2>45 mm Hg, due to • Increased CO2 production • Hypoventilation • Increased dead space ventilation
Oximetry • Oximetry detects arterial blood HbO2 and Hb ratio • Ear oximetry • Pulse oximetry • Co-Oximeters can detect Met Hb and CO Hb • Mixed venous oximetry measured O2 sat in PA blood
CO2 detector and capnometry • CO2 detector is a method for determining the success or failure of ET intubation. • Clinical application of capnometry in ICU: - Cardiac output monitor - Ventilator-related mishap detection - Early detection of nosocomial disorders - Ventilator weaning - Controlled hyperventilation
Acute respiratory distress syndrome (ARDS) • A leading cause of acute respiratory failure with high mortality • A diffuse inflammatory injury in the lung • Not an accumulation of watery edema fluid • Not a primary disease, but a complication
Diagnostic criteria for ALI and ARDS • Acute onset • Presence of predisposing condition • PaO2/FiO2 < 200 mm Hg for ARDS, < 300 mm Hg for ALI • CXR – bilateral infiltrates • PAOP < 18 mm Hg or no clinical evidence of high LA pressure
Management of ARDS • No real treatment for ARDS, only supportive • Mechanical ventilation: low-volume ventilation permissive hypercapnia positive end-expiratory pressure • Fluid management – reducing extravascular lung water • Pharmacotherapy – uncertain effect
Respiratory therapy • Oxygen inhalation therapy • Chest physical therapy • Respiratory pharmacotherapy • Mechanical ventilation
Oxygen inhalation therapy • Arterial hypoxemia: PaO2 < 60 mm Hg (SaO2 < 90 %) • Tissue hypoxia: blood lactate > 4 mmHg • Endpoint of O2 therapy is tissue oxygenation • Tissue hypoxia may not consistent with arterial hypoxemia
Effect of Oxygen on blood flow • Oxygen tends to reduce systemic blood flow due to: 1. vasoconstrction in all vascular bed except the pulmonary circulation 2. decrease in cardiac output 3. negative inotropic effect
Method of oxygen inhalation • Low-flow oxygen delivery system with variable FiO2 • High-flow oxygen delivery system with constant FiO2
Low-flow oxygen delivery systems Device Reservoir Oxygen flow FiO2 capacity (L/min) Nasal cannula 50 ml 1 0.21-0.24 2 0.24-0.28 3 0.28-0.34 4 0.34-0.38 5 0.38-0.42 6 0.42-0.46 Oxygen face mask 150-250 ml 5-10 0.40-0.60 Mask-reservoir bag 750-1250 ml Partial rebreather 5-7 0.35-0.75 Nonrebreather 5-10 0.40-1.0 FiO2 = 20 + 4 X oxygen flow (L/ml)
Respiratory pharmacotherapy • Bronchodilators • Corticosteroids • Mucokinetic therapy
Mechanical ventilation • Mechanical ventilation is positive pressure ventilation • Indications of mechanical ventilation Rate ABG: hypoxia and hypercapnia Mechanical parameter: MV, VC and NIP Dead space and shunt • Contraindication of mechanical ventilation
Effect of positive pressure ventilation Noncompliant lung Normal lung
Respiratory parameter • Rate: 10 – 20/min • VT: 6 – 10/kg • FiO2: 40 – 100% • PEEP: 5 – 10 cm H2O • PS: 5 – 10 cm H2O • I:E ratio: 1:2
Patterns of mechanical ventilation • Control mode ventilation • Assist-control ventilation
Pattern of mechanical ventilation • Volume-controlled ventilation ACV (assist control ventilation) IMV (intermittent mandatory ventilation) SIMV (synchronized IMV) • Pressure-controlled ventilation • Pressure support ventilation • Special pattern:
Functional mode of ventilator • PEEP (positive end expiratory pressure) • PS (pressure support) • I:E reversal ratio
Discontinuing mechanical ventilation • Ventilator required for brainstem respiratory depression (e.g.,GA in OR or drug overdose) is easy to discontinue • Ventilator required for cardiopulmonary insufficiency is weaning in gradual process
Discontinuing mechanical ventilation Clinical evaluation: Awake Spontaneous breathing Ability of airway protection Stable hemodynamics
Discontinuing mechanical ventilation Sequence of weaning: FiO2 to 50% or less PEEP to 5 cm H2O or less PS to 10 cm H2O or less
Discontinuing mechanical ventilation Bedside weaning parameters: Parameter Normal range Threshold for weaning PaO2/FiO2 >400 200 VT 5-7 ml/kg 5 ml/kg Rate 10-20/min <40/min VC 65-75 ml/kg 10 ml/kg VE 5-7 L/min <10 L/min Pi max >-90 cm H2O (F) -24 cm H2O >-120 cm H2O (M) Rate/VT <50/min/L <100/min/L
Discontinuing mechanical ventilation Methods of weaning: T-piece weaning IMV weaning CPAP weaning
Hemodynamic monitoringNoninvasive • ECG: heart rate, rhythm, ischemia (ST-T) • Noninvasive BP • Echocardiography: TTE, TEE, color-doppler Contractility Volume status EF Ischemia (RWMA) • Noninvasive cardiac output (through A-line)