The nurse is assessing a client who is in shock. Which of the following findings would indicate to the nurse that the client is entering an irreversible stage?

A. PaCO₂ of 45 mm Hg is incorrect because 45 mm Hg is at the upper limit of normal (normal 35–45 mm Hg). In early shock, clients often hyperventilate, causing a decreased PaCO₂. A value of 45 mm Hg alone does not specifically indicate irreversible shock. B. Respirations 30/min is incorrect because tachypnea is a compensatory mechanism seen in the early (compensatory) stage of shock. The body attempts to improve oxygen delivery by increasing respiratory rate. This finding alone does not indicate irreversible shock. C. Urine output 15 mL/hr is correct because severely decreased urine output indicates significant renal hypoperfusion and possible acute kidney injury. In the irreversible (refractory) stage of shock, prolonged tissue hypoxia leads to organ failure. Oliguria (less than 30 mL/hr in adults) is a critical sign of worsening shock, and 15 mL/hr reflects severe compromise and progression toward multi-organ failure. D. Blood pressure of 100 mm Hg systolic is incorrect because although this may be slightly low depending on baseline, it does not necessarily indicate irreversible shock. In early shock, blood pressure may remain near normal due to compensatory vasoconstriction. Profound, persistent hypotension despite interventions is more consistent with the irreversible stage.