How to manage a patient with chronic obstructive pulmonary disease (COPD) and flail chest presenting with metabolic acidosis, as indicated by a low bicarbonate level of 14?

Management of Metabolic Acidosis in a COPD Patient with Flail Chest

A patient with COPD and flail chest presenting with a bicarbonate level of 14 requires immediate assessment of acid-base status with arterial blood gas analysis, controlled oxygen therapy, and consideration of ventilatory support if pH is below 7.26. 1

Initial Assessment and Management

• Obtain arterial blood gas (ABG) measurement immediately to determine pH, PaCO2, and PaO2, noting the inspired oxygen concentration (FiO2) 1
• Check for signs of infection (pyrexia, purulent sputum), severe airways obstruction (audible wheeze, tachypnoea, use of accessory muscles), peripheral edema, cyanosis, and confusion 1
• Obtain chest radiograph to assess the extent of flail chest and rule out pneumonia or other complications 1
• Complete blood count, urea and electrolytes, and ECG should be performed within the first 24 hours 1

Oxygen Therapy

• Start with controlled oxygen therapy - no more than 28% via Venturi mask or 2 L/min via nasal cannulae until arterial blood gases are known 1
• Check blood gases within 60 minutes of starting oxygen and after any change in inspired oxygen concentration 1
• If PaO2 improves without pH deterioration, gradually increase oxygen concentration until PaO2 is above 7.5 kPa 1
• If pH falls below 7.26 (due to rising PaCO2), consider alternative strategies 1
• For nebulized medications, use compressed air rather than oxygen if respiratory acidosis is present 1

Management of Metabolic Acidosis

• A bicarbonate level of 14 indicates significant metabolic acidosis, which may be due to tissue hypoperfusion, renal dysfunction, or other causes 2
• Determine the anion gap to differentiate between anion gap and non-gap metabolic acidosis 2
• Identify and treat the underlying cause of metabolic acidosis (e.g., sepsis, shock, renal failure) 2
• Ensure adequate fluid resuscitation to improve tissue perfusion and renal function 2
• Consider the possibility of lactic acidosis, especially if the patient has signs of shock or hypoperfusion 2

Respiratory Support

• If pH is below 7.26 with rising PaCO2 despite controlled oxygen therapy, consider ventilatory support 1
• Non-invasive positive pressure ventilation (NIPPV) should be considered first, as it has been shown to reduce the need for intubation and length of hospital stay 1
• Intravenous doxapram (respiratory stimulant) may be considered in patients with acidosis (pH <7.26) to tide over for 24-36 hours until the underlying cause is controlled 1
• If NIPPV fails or is contraindicated, consider invasive mechanical ventilation (IPPV) 1

Factors Favoring Ventilatory Support

• Identifiable and reversible cause for deterioration (e.g., pneumonia, drug overdose) 1
• First episode of respiratory failure 1
• Acceptable quality of life or habitual level of activity 1

Factors Against Ventilatory Support

• Previously documented severe COPD unresponsive to therapy 1
• Poor quality of life despite maximal therapy 1
• Severe comorbidities 1

Additional Treatments

• Nebulized bronchodilators (β-agonist and/or anticholinergic) should be administered on arrival and at 4-6 hourly intervals 1
• Consider systemic corticosteroids (prednisolone 30 mg/day or 100 mg hydrocortisone if oral route not possible) 1
• Appropriate antibiotics if infection is suspected 1
• Consider diuretics if peripheral edema and raised jugular venous pressure are present 1
• Prophylactic subcutaneous heparin for patients with acute-on-chronic respiratory failure 1

Monitoring and Follow-up

• Repeat ABG measurements if clinical situation deteriorates 1
• Monitor oxygen saturation continuously 1
• Record peak flow twice daily until clinically stable 1
• Before discharge, check arterial blood gas tensions on air to assess need for long-term oxygen therapy 1

Pitfalls and Caveats

• Do not give high-concentration oxygen without monitoring blood gases, as this may worsen respiratory acidosis in COPD patients 1
• A pH below 7.26 is predictive of poor outcome and requires aggressive management 1
• Neither age alone nor PaCO2 are good guides to the outcome of assisted ventilation; pH >7.26 is a better predictor of survival 1
• Misconceptions about difficulty weaning from ventilators should not preclude intubation when indicated 1
• The presence of metabolic acidosis in a COPD patient may indicate a serious underlying condition requiring prompt investigation and treatment 2, 3