Lactate and Perfusion Trending

Lactate is a useful alarm signal, not a direct perfusion gauge. A raised value means that lactate production, clearance, or both are abnormal; it does not by itself prove that tissues are receiving too little oxygen. The clinically useful question is not simply, “What is the lactate?” It is, “Is the patient improving, and does the trend fit the bedside picture?” Pair each result with blood pressure and MAP, heart rate, work of breathing, oxygenation, capillary refill, skin temperature and colour, pulse quality, mental status, and urine output. Blood lactate is roughly 0.5–2.0 mmol/L in health. Values above 2 mmol/L are conventionally called hyperlactatemia, but a value that is only mildly raised—or even at the upper end of the reference range—should not be dismissed when the patient has signs of shock. Conversely, a high result after perfusion has improved may reflect catecholamine-driven production or delayed hepatic clearance rather than treatment failure. Trending means repeating the measurement after an appropriate interval and interpreting the direction alongside the response to treatment. It does not mean drawing lactate repeatedly while giving fluid until...