Consequences of metabolic acidosis

This topic has never come up in the CICM fellowship exam. Likely, it is reserved for the primaries.

Consequences of Metabolic Acidosis

Respiratory consequences:

• Increased respiratory stimulus
• Increased work of breathing
• Right shift of the oxyhaemoglobin dissociation curve (i.e. a decreased affinity of haemoglobin for oxygen)

Cardiovascular consequences:

• Decreased cardiac output
• Increased propensity to arrhythmias
• Decreased systemic vascular tone and arterial vasodilation
• Decreased responsiveness to catecholamines
• Pulmonary vasoconstricition

Neurological consequences:

• Cerebral vasodilation, thus increased intracranial pressure

Electrolyte changes

• Hyperkalemia
• Hypercalcemia

Effects on renal function and fluid balance

• Increased renal ammonia production
• Increased renal tubular ammonia secretion
• Thus, increased renal oxygen demand
• Diuresis (eg. due to osmotic effect of "gap" anions)

Gastrointestinal consequences

• Decreased stomach emptying
• Nausea and vomiting
• Decreased splanchnic perfusion

Haematological consequences

• Coagulopathy (due to impaired clotting factor function) -
• Impaired platelet aggregation (due to effects of hyperchloraemia)
• (More on this in the chapter on the haemostatic resuscitation of massive haemorrhage in trauma)