Phase 1 · Understand the Body — Why the disease behaves the way it does.
The One-Line Truth
The whole disease in one chain
Everything on this page exists to explain this line.
For every blood gas, ask: which way is pH moving, is the main problem CO₂ or bicarbonate, is the body fixing it the right amount, does anion gap show hidden acids, then fix what broke—not the number itself.
Three teams balancing a seesaw
Your blood is like a seesaw that must stay perfectly level (pH 7.35–7.45) or the rider (your brain and heart) gets hurt. Three teams work the seesaw: buffers are like shock absorbers that instantly soften the bump when someone jumps on (H⁺ ions land on them instead of moving pH). Lungs are like a pump that removes weight from one side by exhaling CO₂ (acid in disguise), or adds weight by holding CO₂ if the seesaw tipped the other way. Kidneys are like workers who slowly move sand (bicarbonate, the base) from one bucket to the other over hours to days, fine-tuning balance. When the upstream problem breaks—a heavy box (lactate from shock, ketones from uncontrolled diabetes, toxins from poison) gets dumped on one side, or one team stops working (lungs too weak to pump, kidneys can't move sand anymore)—the seesaw tips. The body's compensation is the other two teams working overtime to level it again, but if the load is too heavy or stays too long, the seesaw tips past recovery and the rider falls.
ADA Standards of Care in Diabetes 2024 · Surviving Sepsis Campaign 2021 · Berend K et al. N Engl J Med 2014;371:1434 · UpToDate: Approach to the adult with metabolic acidosis, 2024 · reviewed 2026-07-07