1. Mechanical Ventilation Adjustments in Respiratory Disorders

Precise ventilator management is critical in primary respiratory acid–base disturbances. The primary goals are to ensure adequate oxygenation and ventilation while minimizing ventilator-induced lung injury (VILI). Gradual correction of PaCO₂, adherence to low tidal volumes, and careful titration of PEEP and FiO₂ are essential to prevent complications like barotrauma and cerebral ischemia.

A. Indications and Targets for Ventilator Adjustment

• Indications for Setting Changes:
  • Respiratory Acidosis: pH < 7.30 with PaCO₂ > 50 mm Hg despite current settings.
  • Respiratory Alkalosis: pH > 7.55 with PaCO₂ < 30 mm Hg causing clinical concern.
• Therapeutic Targets:
  • Arterial pH: 7.30–7.45.
  • PaCO₂: Near the patient’s known chronic baseline, when applicable.
  • Oxygenation: SpO₂ 88–95% or PaO₂ 55–80 mm Hg to avoid both hypoxia and hyperoxia.

B. Parameter Titration Strategy

Ventilator adjustments should follow established lung-protective principles, such as those from the ARDSNet protocol.

2. Prevention of ICU-Related Complications

Management of acid-base disorders occurs within the complex ICU environment. Proactive integration of care bundles for infection control, gastrointestinal (GI) prophylaxis, and electrolyte management is essential to reduce overall morbidity and mortality.

A. Vascular Catheter Infection Control

• Use maximal sterile barrier precautions during insertion (cap, mask, sterile gown/gloves, full-body drape).
• Prepare skin with chlorhexidine antisepsis before insertion.
• Consider using antiseptic-impregnated catheters and dressings in high-risk populations.
• Perform daily reviews of all catheter necessities and remove them as soon as they are no longer indicated.

B. Stress Ulcer Prophylaxis (SUP)

C. Electrolyte Repletion

• Potassium: Target 4.0–4.5 mEq/L. For K⁺ < 3.5 mEq/L, administer KCl 20–40 mEq IV over 2–4 hours. Use continuous ECG monitoring for infusions if K⁺ < 3.0 mEq/L.
• Magnesium: Target >2.0 mg/dL. For Mg²⁺ < 1.5 mg/dL, administer MgSO₄ 2 g IV over 2 hours.

3. Management of Iatrogenic Complications

Therapeutic interventions for acid-base disorders, particularly sodium bicarbonate administration, can lead to significant iatrogenic complications. Clinicians must anticipate and mitigate fluid overload and electrolyte disturbances that arise from these treatments.

A. Fluid Overload from Sodium Bicarbonate

Sodium bicarbonate is indicated for severe metabolic acidosis (pH ≤ 7.15) with associated hemodynamic compromise or acute kidney injury. The large sodium load requires careful monitoring.

B. Hypokalemia Secondary to Metabolic Alkalosis

• Mechanism: Alkalosis drives potassium into cells and enhances renal potassium secretion in exchange for hydrogen ions, leading to and perpetuating hypokalemia.
• Replacement: Administer KCl 20 mEq IV over 2 hours for K⁺ 3.0–3.4 mEq/L, and up to 40 mEq for K⁺ < 3.0 mEq/L. Always correct co-existing hypomagnesemia first.

C. Pharmacologic Correction of Severe Metabolic Alkalosis

• Acetazolamide: 500 mg IV once daily can be used to promote renal bicarbonate excretion, typically lowering serum HCO₃⁻ by 2–5 mEq/L in 24 hours.
• Hydrochloric Acid Infusion: Reserved for life-threatening metabolic alkalosis (pH > 7.55) refractory to other measures. Requires central line administration and close monitoring.

4. Multidisciplinary Goals of Care Conversations

Decisions regarding the initiation or continuation of life-sustaining therapies like renal replacement therapy (RRT) and prolonged mechanical ventilation must be grounded in shared decision-making. These conversations should align medical possibilities with the patient’s values and goals.

A. Renal Replacement Therapy (RRT) Initiation

• KDIGO Indications: Consider RRT for life-threatening complications such as refractory hyperkalemia, severe metabolic acidosis (pH < 7.15), diuretic-unresponsive volume overload, or uremic complications (e.g., pericarditis, encephalopathy).
• Holistic Consideration: The decision to start RRT must incorporate the patient’s overall prognosis, personal values, and goals of care.
• Pharmacist Role: The clinical pharmacist is crucial for adjusting drug dosing for RRT clearance and monitoring anticoagulation effects on the patient’s acid-base status.

B. Weaning vs. Prolonged Mechanical Ventilation

• Extubation Readiness Criteria: Assess daily for readiness, including resolved or stable underlying cause, pH > 7.30, FiO₂ ≤ 0.40, PEEP ≤ 8 cm H₂O, and hemodynamic stability.
• Weaning Protocols: Implement protocols that include daily sedation interruptions and spontaneous breathing trials (SBTs) to identify the earliest opportunity for liberation from the ventilator.

C. The Multidisciplinary Care Conference

Convene regular family conferences involving the core ICU team (physician, nurse), clinical pharmacist, respiratory therapist, and palliative care. Discuss realistic outcomes, including the burdens and benefits of continuing organ support, to ensure care remains aligned with the patient’s wishes.