What is the treatment for a patient with arterial blood gas results showing acidosis (pH 7.32), normocapnia (pCO2 39), hypoxemia (pO2 27), base excess (-5), low bicarbonate (HCO3 20), and low oxygen saturation (O2 sat 46%)?

From the Guidelines

The patient requires immediate oxygen therapy to correct the severe hypoxemia, with a target oxygen saturation of 94-98% as per the BTS guideline for oxygen use in adults in healthcare and emergency settings 1. The patient's arterial blood gas results indicate hypoxemic respiratory failure with mild metabolic acidosis, as evidenced by a pH of 7.32, pCO2 of 39, pO2 of 27, base excess of -5, and low bicarbonate (HCO3 20) and oxygen saturation (O2 sat 46%) levels. Key considerations in managing this patient include:

• Providing supplemental oxygen to achieve a target saturation range of 94-98% as recommended by the BTS guideline 1
• Monitoring the patient's response to oxygen therapy with repeat arterial blood gas measurements within 30-60 minutes 1
• Evaluating the patient for underlying causes of hypoxemic respiratory failure, such as pneumonia, pulmonary embolism, or acute respiratory distress syndrome (ARDS)
• Considering non-invasive positive pressure ventilation (NIPPV) or intubation and mechanical ventilation if the patient's oxygenation does not improve with supplemental oxygen or if they show signs of respiratory fatigue, as recommended by the ESC guidelines for the diagnosis and treatment of acute and chronic heart failure 1 The BTS guideline recommends targeting a saturation range of 94-98% for most patients, unless they have a history of COPD or other risk factors for hypercapnic respiratory failure, in which case a lower target saturation range may be appropriate 1. In this case, since the patient has a critically low pO2 and oxygen saturation, initiation of high-flow oxygen therapy via a non-rebreather mask at 15 L/min or NIPPV with settings of IPAP 12-14 cmH2O and EPAP 5-6 cmH2O is essential to prevent tissue hypoxia and potential organ damage. After stabilizing oxygenation, further workup should include chest imaging, complete blood count, and evaluation for underlying causes of hypoxemic respiratory failure. The mild metabolic acidosis should improve with treatment of the underlying condition, but may require monitoring and possible intervention if it worsens. Arterial blood gases should be repeated within 30-60 minutes after initiating oxygen therapy to assess response, as recommended by the BTS guideline 1.

From the FDA Drug Label

CLINICAL PHARMACOLOGY Intravenous sodium bicarbonate therapy increases plasma bicarbonate, buffers excess hydrogen ion concentration, raises blood pH and reverses the clinical manifestations of acidosis. The patient's arterial blood gas results show acidosis (pH 7.32), low bicarbonate (HCO3 20), and base excess (-5), indicating a need to increase plasma bicarbonate and buffer excess hydrogen ion concentration.

• The patient's condition is consistent with the use of sodium bicarbonate (IV) to treat acidosis, as it increases plasma bicarbonate and raises blood pH.
• However, the patient also has hypoxemia (pO2 27) and low oxygen saturation (O2 sat 46%), which are not directly addressed by sodium bicarbonate therapy.
• The use of sodium bicarbonate should be considered as part of a broader treatment plan that also addresses the patient's hypoxemia and low oxygen saturation. 2

From the Research

Treatment Approach

The patient's arterial blood gas results show acidosis (pH 7.32), normocapnia (pCO2 39), hypoxemia (pO2 27), base excess (-5), low bicarbonate (HCO3 20), and low oxygen saturation (O2 sat 46%) 3.

Acid-Base Management

According to 4, acid-base disorders should be considered a process with the goal being to treat the patient and the underlying condition, not the numbers.

Hypoxemia Management

For severe hypoxemia, possible adjuvant therapies can be considered, including noninvasive ventilatory support, mechanical ventilation, neuromuscular blocking agents, prone positioning, and extracorporeal membrane oxygenation (ECMO) 5.

Sodium Bicarbonate Therapy

There is a lack of clinical evidence that administration of sodium bicarbonate for respiratory acidosis has a net benefit; in fact, there are potential risks associated with it 6. However, early sodium bicarbonate may be beneficial in patients with vasopressor dependency and metabolic acidosis 7.

Key Considerations

• Tailoring mechanical ventilation to the individual patient is fundamental to reduce the risk of ventilation-induced lung injury (VILI) 5.
• Targeting oxygenation of 88-92 % and tolerating a moderate level of hypercapnia are a safe choice 5.
• The use of ECMO in severe ARDS is increasing worldwide, but because of a lack of randomized trials is still considered a rescue therapy 5.