A client with severe head trauma sustained in a car accident is admitted to the intensive care unit. Thirty-six hours later, the client’s urine output suddenly rises above 200 ml/hour, leading the nurse to suspect diabetes insipidus. Which laboratory findings support the nurse’s suspicion of arginine vasopressin deficiency?

Reasoning:

Choice A reason: A blood pressure of 150/90 mm Hg is not an absolute contraindication for thrombolytic therapy. While hypertension must be controlled (below 185/110 mm Hg) before thrombolytics, it is manageable with medication, unlike hemorrhagic stroke, which poses an immediate and absolute risk of worsening bleeding.

Choice B reason: Previous thrombolytic therapy within 12 months is not an absolute contraindication. Guidelines restrict thrombolytics within a shorter timeframe (e.g., recent major surgery), but prior therapy alone does not preclude use. Hemorrhagic stroke is a definitive contraindication due to the risk of catastrophic bleeding.

Choice C reason: Evidence of hemorrhagic stroke is an absolute contraindication for thrombolytic therapy, as thrombolytics like tPA dissolve clots, increasing bleeding in an already hemorrhagic brain. This risks worsening intracranial hemorrhage, leading to neurological deterioration or death, making it a critical exclusion criterion.

Choice D reason: Evidence of stroke evolution, such as progressing symptoms, is not an absolute contraindication. It may influence timing or eligibility, but thrombolytics can still be used within the time window if ischemic. Hemorrhagic stroke is a definitive barrier due to bleeding risk.

Reasoning:

Choice A reason: Above-normal urine osmolality and below-normal serum osmolality are not consistent with diabetes insipidus. High urine osmolality suggests concentrated urine, typical in syndrome of inappropriate antidiuretic hormone (SIADH), where ADH is excessive. Low serum osmolality also aligns with SIADH due to water retention, not the water loss seen in diabetes insipidus.

Choice B reason: Above-normal urine and serum osmolality levels do not reflect diabetes insipidus. High urine osmolality indicates concentrated urine, which contradicts the dilute urine output of diabetes insipidus. High serum osmolality could occur with dehydration, but the combination with high urine osmolality suggests another condition, not ADH deficiency.

Choice C reason: Below-normal urine osmolality and above-normal serum osmolality are classic findings in diabetes insipidus. Arginine vasopressin (ADH) deficiency impairs water reabsorption, leading to dilute urine (low osmolality). The resulting water loss increases serum osmolality as the body becomes dehydrated, supporting the diagnosis of diabetes insipidus.

Choice D reason: Below-normal urine and serum osmolality levels are inconsistent with diabetes insipidus. Low urine osmolality occurs due to ADH deficiency, but low serum osmolality suggests water retention, as in SIADH. Diabetes insipidus causes dehydration, elevating serum osmolality, not lowering it, making this combination unlikely in this condition.