Symptoms of Lactic Acidosis
Lactic acidosis presents with nonspecific symptoms that often include gastrointestinal complaints (nausea, vomiting, abdominal pain), respiratory distress (tachypnea, dyspnea), and neurological changes (weakness, confusion, altered mental status), along with signs of tissue hypoperfusion such as hypotension and oliguria. 1, 2
Clinical Presentation
Early/Subtle Symptoms
The initial presentation is often subtle and nonspecific, which can delay diagnosis 1, 3:
- Gastrointestinal symptoms: Nausea, vomiting, abdominal pain, distension, diarrhea, and anorexia 1, 4
- Generalized weakness and myalgias (muscle pain) 1, 3
- Malaise (general feeling of being unwell) 3
- Increased somnolence (unusual sleepiness or drowsiness) 3
Respiratory Symptoms
As acidosis progresses, compensatory respiratory changes occur 1, 2:
- Tachypnea (rapid breathing) 1, 2
- Dyspnea (shortness of breath) 1, 4
- Hyperventilation (deep, rapid breathing as the body attempts to blow off CO₂) 3
Neurological Symptoms
Central nervous system manifestations include 1, 2:
- Confusion and altered mental status 5, 1, 2
- Weakness (generalized or ascending neuromuscular weakness) 1, 4
- Paresthesias (abnormal sensations) 4
Cardiovascular Signs
In severe cases, cardiovascular compromise develops 3:
- Hypotension (low blood pressure) 5, 3
- Resistant bradyarrhythmias (slow or irregular heartbeat that doesn't respond to treatment) 3
- Feeling cold in hands or feet 3
- Dizziness or lightheadedness 3
Signs of Tissue Hypoperfusion
These indicate organ dysfunction and are particularly concerning 5:
- Oliguria (decreased urine output) 5
- Acute alteration of mental status 5
- Hypoperfusion signs indicating ongoing organ failure 5
Critical Pitfalls to Avoid
Do not dismiss early nonspecific symptoms, especially in high-risk patients (those on metformin, with renal impairment, elderly patients, or those with sepsis) 1, 3. The FDA explicitly warns that metformin-associated lactic acidosis has a "subtle onset" with nonspecific symptoms that can progress to severe acidosis with cardiovascular collapse 3.
The presence of these symptoms in patients taking metformin, NRTIs, or with conditions predisposing to lactic acidosis (sepsis, shock, liver disease, renal impairment) should prompt immediate lactate measurement and discontinuation of offending medications 1, 3.
In the context of intra-abdominal infections or acute abdomen, the combination of abdominal pain with lactic acidosis and elevated urea should raise immediate concern for mesenteric ischemia, which requires emergent imaging and possible surgical intervention 1.