Negative Pressure Pulmonary Edema Laryngospasm and Negative Pressure Pulmonary Edema พญ.สุดารัตน์ ศุภกิจเจริญ หน่วยงานวิสัญญี โรงพยาบาลกำแพงเพชร

Laryngospasm is a form of airway obstruction. Laryngospasm is usually easily detected and managed, but may present atypically and/or be precipitated by factors which are not immediately recognized. If poorly managed, it has the potential to cause morbidity and mortality such as severe hypoxaemia, pulmonary aspiration, and post-obstructive pulmonary edema.

SIGNS Inspiratory stridor/airway obstruction Increased inspiratory efforts/tracheal tug Paradoxical chest/abdominal movements Desaturation Bradycardia esp.in children Central cyanosis

THINK OF Airway irritation and/or obstruction Blood/secretions in the airway Regurgitation and aspiration Excessive stimulation/“light” anaesthesia

MANAGEMENT Recognise Laryngospasm Apply CPAP c 100% O2 c airway maneuver Assess O2 entry Bag movement No Some Complete laryngospasm Partial laryngospasm

Complete laryngospasm Partial laryngospasm Consider specialized Maneuver to convert to partial laryngospasm Eliminate stimulus ex.secretion Deepen anesthesia c volatile or porpofol not improvement Reassess O2 entry No iv assess iv assess Improvement suxa 1-2 mg/kg iv +/- atropine 0.02mg/kg iv suxa 3-4 mg/kg im +/- atroine 0.02 mg/kg im CPAP ventilate c 100%O2 Attempt intubation as appropriate Improvement Stabilise and resume anesthesia +/- NG tube Not improved CPR + ACLS as indicated

Specialised maneuver Pressure in laryngospasm notch Pull mandible forward = forcible jaw thrust

Negative Pressure Pulmonary Edema

Mechanism of Edema Formation Two theories on the edema fluid formation One of the theory suggests significant fluid shifts due to changes in intrathoracic pressure and hydrostatic transpulmonary gradient due to increased blood flow in pulmonary vessel. The second proposed mechanism involves the disruption of the alveolar epithelial and pulmonary microvascular membranes from severe mechanical stress which leads to increased pulmonary capillary permeability and protein-rich pulmonary edema.

Negative Pressure Pulmonary Edema Inspiratory efforts against a closed glottis (modified Mueller maneuver) may result in pleural pressures (> - 100 cm H2O) Hypoxic pulmonary vasoconstriction These changes result in: Increased transmural pressure Fluid filtration into the lung Development of pulmonary edema and capillary failure.

Development of NPPE

Mechanism of Negative Pressure Pulmonary Edema 10 Pulmonary edema remains 1 An upper airway obstruction occurs 9 2 Airway obstruction is relieved The patient continues trying to inhale against the obstruction 8 3 Fluid from the interstitial space floods into the alveoli A high degree of negative intra-thoracic pressure develops 7 A disruption in the alveolar membrane junction occurs 4 Venous return to the heart increases 6 5 Pressure in the pulmonary capillary bed increases Cardiac output decreases

Normal Respiration -1cm H2O +1cm H2O

Normal Pressure - Oncotic Pressure (25mmHg) - Osmotic Pressure (15mmHg)

Airway Obstruction -1cm H2O

Altered pressure

Alveolar Membrane

Risk assessment Laryngospasm Obesity, OSA Young male athlets Epiglotitis Croup Partial trachial obstruction by FB Upper airway pathology ex .laryngomalacia, vocal cord paralysis Obstructed ETT or LMA Difficult intubation, nasal, oral or pharyngeal Surgical site ex. Oropharynx,neck,urogenital Extubation during light planes of anesthesia Secretions falling on the vocal cords.

Signs and Symptoms Frothy pink pulmonary secretions : Hallmark sign Tachycardia,hypertension Diaphoresis Auscultation : Rales,Occasionally wheezing Hypoxemia on pulse oximetry or ABG Bilateral, alveolar infiltrates on chest x-ray

CXR

Differential diagnosis ARDS Intravascular volume excess Cardiac abnormalities Pulmonary emboli

Treatment Early diagnosis Reestablishment of the airway Adequate oxygenation Application of positive airway pressure Via face mask or LMA Endotracheal intubation with vent support Although NPPE does not result from fluid overload, most authors recommend gentle diuresis using low-dose furosemide(1mg/kg).

Prevention Early recognition Avoid potential obstruction Ensure adequate depth of anesthesia during use of facemask or LMA Consider the use of Bite block to ensure patency of artificial airway during emergence from anesthesia Perform trachial extubation in fully awake Pt.