The Cushing Reflex: Oliguria as a Reflection of an Elevated Intracranial Pressure

Abstract

Oliguria is one of the clinical hallmarks of renal failure. The broad differential diagnosis is well known, but a rare cause of oliguria is intracranial hypertension (ICH). The actual knowledge to explain this relationship is scarce. Almost all literature is about animals where authors describe the Cushing reflex in response to ICH. We hypothesize that the Cushing reflex is translated towards the sympathetic nervous system and renin-angiotensin-aldosterone system with a subsequent reduction in medullary blood flow and oliguria. Recently, we were confronted with a patient who had complicated pituitary surgery and displayed multiple times an oliguria while he developed ICH.

Figure 1

Oliguria during intracranial hypertension. (a) Head CT scan, during the first episode of oliguria, shows an obstructive hydrocephalus. (b) Head CT scan, during the second episode of oliguria, shows a hydrocephalus due to obstructed VP-shunt due to intraventricular bleeding. (c) ECG with sinus bradycardia (30 bpm) observed during the second episode of oliguria. (d) This graphic displays the patient's serum sodium levels (mmol/L) in comparison with diuresis and pulse. We notice two times a significant oliguric phase on 11-Oct and 19-Oct. These were the days that intracranial hypertension was present and surgery for decompression was executed. We see a significant decrease in diuresis on 15-16-Oct; this was due to excessive high doses of desmopressin (8 µg iv).