Critical Care of Patients With Respiratory Emergencies Flashcards

Pulmonary Embolism (PE)

• Definition: Any substance that enters the venous circulation and causes a blockage in the pulmonary vasculature.

• Commonality: A blood clot is the most common type of blockage found in PE.

• Risk Link: Deep Vein Thrombosis (DVT) increases the risk of PE by $50\%$.

• Pathophysiology (Mechanism of Movement):

  • The clot breaks off from the vessel wall.

  • It travels through the bloodstream to the right side of the heart.

  • It lodges in the pulmonary artery or one of its branches.

Risk Factors for Pulmonary Embolism

• Physical and Lifestyle Factors:

  • Prolonged immobility.

  • Obesity.

  • Advancing age.

  • Smoking.

  • Recent travel.

• Medical Procedures and History:

  • Central Venous Catheters.

  • Surgery in the last $3\,\text{months}$.

  • History of thromboembolism.

  • Trauma.

  • Hip or knee replacements.

• Conditions and Medications:

  • Pregnancy (and up to $3\,\text{months}$ postpartum).

  • General and genetic conditions that increase blood clotting.

  • Infection, specifically including Covid 19 Infection.

  • Estrogen therapy.

  • Heart failure.

  • Stroke.

  • Cancer/chemotherapy.

  • Heparin-induced thrombocytopenia.

Virchow’s Triad

• Injury to the vessel wall: Any endothelial damage.

• Abnormal blood flow: Factors promoting venous stasis.

• Hypercoagulability: Conditions that increase the inherent tendency of the blood to clot.

Case Study: Margaret Chen

• Patient Profile: 68-year-old female, postoperative day 2 following total knee replacement surgery.

• Current Symptoms: Reports right calf pain and tenderness; right leg appears slightly more swollen than the left; patient is reluctant to move due to pain.

• Vital Signs:

  • $BP$: $138/82\,mmHg$

  • $HR$: $94\,bpm$

  • $RR$: $18\,bpm$

  • $Temp$: $38.1\,°C$ ($100.6\,°F$)

  • $SpO_2$: $94\%$ on room air

• Medical History: Type 2 diabetes, hypertension, obesity ($BMI\,34$).

• Status: Primarily in bed since surgery; ambulated once to chair yesterday with significant difficulty.

• Classification of Risk factors in Margaret's case:

  • Venous Stasis: Immobility post-surgery, obesity, limited ambulation, and knee surgery.

  • Endothelial Injury: Total knee replacement (major orthopedic surgery).

  • Hypercoagulability: Fever, dehydration risk, and surgical stress response.

Considerations for Older Adults

• Age and Risk: Risk increases significantly with age; $60\%$ of clots occur in individuals over $70\,\text{years}$ old.

• Anticoagulation Considerations:

  • Nonadherence to medication regimens.

  • Risk of falls.

  • Chronic Kidney Disease ($CKD$).

  • Polypharmacy.

Prevention Strategies

• Lifestyle Changes: Stop smoking and stop IV drug use. Reduce weight and increase physical activity.

• Mobility Guidelines: During travel or recovery, change positions often, avoid crossing legs, and get up to walk every $2-3\,\text{hours}$.

• Hydration: Push fluids.

• Pharmacology: Anticoagulants for known risk factors can provide a $50-80\%$ reduction in PE occurrence.

Assessment and Clinical Manifestations

• General Presentation: Signs and symptoms ($S/S$) are often vague or manifest as nonspecific discomfort. PE may be life-threatening.

• Classic Signs and Symptoms:

  • Sudden onset of dyspnea and hypoxemia.

  • Chest pain described as sharp and stabbing.

  • Feeling of impending doom.

  • Cough.

  • Abnormal breath sounds.

• Cardiac Manifestations: Tachycardia, Jugular Venous Distention ($JVD$), syncope, cyanosis, and hypotension.

Saddle Pulmonary Embolism

• Definition: A large embolus that straddles the bifurcation of the main pulmonary artery.

• Impact: Simultaneously blocks both the right and left pulmonary arteries.

• Urgency: This is a life-threatening emergency. Without immediate treatment, it can lead to cardiac arrest and death.

• Presentation: Typically presents with severe dyspnea, respiratory distress, chest pain, hypotension, and shock.

Labs and Diagnostics for PE

• Arterial Blood Gas ($ABG$): Initially shows alkalosis because the patient typically hyperventilates in response to hypoxia.

• Blood Tests: $BNP$, troponin, and $D-dimer$.

• Imaging:

  • CTPA (Computed tomography pulmonary angiography): Designated as the gold standard for diagnosis.

  • Lung Scintigraphy: Also known as Ventilation/Perfusion scan or $V/Q$ scan.

  • Chest X-Ray.

  • Doppler.

  • Transthoracic Echocardiogram ($TTE$).

Management of Pulmonary Embolism

• Nonsurgical Management:

  • Oxygen therapy.

  • Anticoagulation or fibrinolytic therapy: Includes Heparin, Low molecular weight heparin ($LMWH/enoxaparin$), Fondaparinux ($Arixtra$), Alteplase, and $DOACs$ versus warfarin.

  • Monitoring responses to interventions and providing psychosocial support.

• Surgical Management:

  • Surgical Embolectomy.

  • Percutaneous catheter-directed therapy.

  • Inferior vena cava ($IVC$) filter placement to catch blood clots.

Drug Therapy for Hypotension in Respiratory Emergencies

• Vasopressors: Used when hypotension persists despite fluid resuscitation.

  • Norepinephrine.

  • Epinephrine.

  • Dopamine.

• Positive Inotropic Agents: Increase myocardial contractility.

  • Milrinone.

  • Dobutamine.

• Vasodilators: To decrease pulmonary artery pressure.

  • Nitroprusside.

Acute Respiratory Failure (ARF)

• Classifications:

  • Hypoxemic/Oxygenation Failure (Type I ARF): PaO_2 < 60\,mmHg with normal or low $PaCO_2$. Airflow is normal but lung blood flow is decreased or diffusion is impaired.

  • Hypercapnia/Ventilatory Failure (Type II ARF): PaCO_2 > 50\,mmHg with pH < 7.35. Problem in $O_2$ intake; airflow is inadequate while blood flow remains normal.

  • Combination: PaO_2 < 60\,mmHg and PaCO_2 > 50\,mmHg with pH < 7.35.

• Causes of Oxygenation Failure: Impaired diffusion of $O_2$ to alveoli, right-to-left shunting of blood in pulmonary vessels.

• Symptoms: Poor respiratory function, low pulse oximetry, confusion, tachycardia or bradycardia, and headache.

• Interventions:

  • Oxygen therapy keeping PaO_2 > 60\,mmHg.

  • Mechanical ventilation if needed.

  • Pharmacology: Bronchodilators, Corticosteroids, Analgesics, and Neuromuscular blockade drugs (for ventilated patients).

  • Non-pharmacological: Position for comfort, relaxation, diversion, guided imagery, and energy conservation.

Acute Respiratory Distress Syndrome (ARDS)

• Key Features:

  • Refractory Hypoxemia: Hypoxemia that persists even when $100\%$ $FiO_2$ is administered.

  • Decreased pulmonary compliance.

  • Dyspnea.

  • Imaging: Non-cardiac associated bilateral pulmonary edema; Dense pulmonary infiltrates on x-ray (ground glass opacities/"white out").

• Pathophysiology:

  • Cytokine storm causes reduced surfactant activity, leading to atelectasis.

  • Edema forms around terminal airways, compressing lymph channels and causing more fluid collection.

  • Can lead to Multiple organ dysfunction syndrome ($MODS$).

  • Onset: Fast; usually occur in hospitalized patients with other conditions (Pneumonia, $COPD$, infections).

• Causes:

  • Direct (Damage from lung): Pneumonia, aspiration, inhalation injury, PE, near drowning.

  • Indirect (Source not from lung): Pancreatitis, Sepsis (major cause), burns, overdose ($OD$), and Multiple blood transfusions ($TRALI$).

• Phases of ARDS:

  • Exudative Phase.

  • Fibrosing Alveolitis Phase.

  • Resolution Phase.

• Treatment:

  • Oxygenation: PaO_2 > 60\,mmHg and O_2\,sat > 90\%.

  • Mechanical ventilation with $PEEP$ ($10-20\,cmH_2O$) and low tidal volumes.

  • Prone positioning and conservative fluid therapy.

Severe Covid 19

• Characteristics: Hypoxemia (oxygen < 94\% on room air) and need for oxygen or ventilatory support.

• Risk Factors: Increased age, male gender, comorbidities ($DM$, cancer, $CVA$, organ disease, mental health disorders, recent pregnancy).

• Severity Progression: Can progress to Critical Covid-19 involving respiratory failure, septic shock, and multiorgan failure.

• Treatment:

  • High flow nasal cannula ($HFNC$) is preferred over Non-invasive positive pressure ventilation ($NPPV$) unless hypercapnia is present.

  • Drugs: Glucocorticoids, Remdesivir (reduces recovery time/mortality), and Thromboprophylaxis.

  • Aerosolization prevention: Intubation in negative pressure rooms, use of $MDIs$ instead of nebulizers.

Prone Positioning

• Definition: Positioning a patient on their front side to improve oxygenation.

• Practice: Recommended for at least $12\,\text{hours}$ per day. Awake patients can self-prone ($6-8\,\text{hours/day}$).

• Risks: Dislodgment of lines/tubes, airway obstruction, pressure injuries, facial trauma/edema, hypotension, arrhythmias, and brachial plexus injuries.

• Contraindications: Inability to tolerate position, facial fractures, unstable spine/femur/pelvis/chest wall, acute bleeding, or elevated intracranial pressure ($ICP$).

Endotracheal Tube (ETT) and Tracheostomy

• ETT Placement Verification: End-tidal carbon dioxide levels, chest x-ray ($CXR$), bilateral breath sounds, symmetrical chest movement.

• Nurse Role: Identifying air/vent problems, preparing equipment ($IV$, suction), pushing drugs, and starting sedation.

• Surgical Airways:

  • Cricothyroidotomy: Surgical incision into the cricothyroid membrane.

  • Tracheotomy: Surgical incision into the trachea.

  • Tracheostomy: The resulting tracheal stoma.

• Tracheostomy Dislodgement Emergency:

  • First $72\,\text{hours}$: Critical as the tract has not matured. Reinsertion is difficult and can cause a "false passage" into soft tissue.

  • After $72\,\text{hours}$: Extend neck, open tissues with Kelly Clamp, insert tube with obturator, then remove obturator.

Mechanical Ventilation

• Modes: Assist-control ($AC$), Synchronized intermittent mandatory ventilation ($SIMV$), Pressure support ventilation, $CPAP$, and $BiPAP$.

• Settings: Tidal volume ($V_T$), Rate ($f$), Fraction of inspired oxygen ($FiO_2$), Peak airway inspiratory pressure ($PIP$), and Positive end-expiratory pressure ($PEEP$).

• PEEP Complications: Increased intrathoracic pressure leading to decreased Cardiac Output ($CO$), hypotension, lung hyperinflation, pneumothorax, and subcutaneous emphysema.

• Ventilator-Associated Lung Injury ($VILI$): Includes barotrauma, volutrauma, atelectrauma, and biotrauma.

• Weaning/Extubation: Use spontaneous breathing trials and "sedation vacations." During extubation, hyperoxygenate, suction, deflate cuff, remove on exhalation, and have patient cough immediately.

Chest Trauma

• Pulmonary Contusion: Potentially lethal injury from rapid deceleration (e.g., $MVA$); results in decreased breath sounds and respiratory failure.

• Rib Fracture: Focus is on pain management to prevent chest splinting.

• Flail Chest: Results from multiple rib fractures in two or more locations. Characterized by paradoxical chest movement (sucking in on inspiration, puffing out on expiration).

• Pneumothorax: Air in the pleural space causing lung collapse.

• Tension Pneumothorax: Air enters but cannot exit. Leads to mediastinal shift, tracheal deviation, and hemodynamic instability.

  • Treatment: Immediate needle decompression ($2\text{nd}$ intercostal space, midclavicular line) followed by chest tube placement.