Renal lithium clearance is hypothesized to be a useful indicator of renal tubular function.

In this study lithium clearance will be monitored in patients with sepsis associated acute kidney injury and in healthy controls.

Lithium is almost completely reabsorbed in the proximal tubule in parallel with sodium and water. What is not reabsorbed here is assumed to be fully excreted in urine, giving a reasonably accurate measurement of sodium reabsorption in the proximal tubule. Endogenous lithium clearance will be measured by inductively coupled plasma mass spectrometry (ICP-MS). The Gomez equations will be applied to calculate efferent arteriolar resistance, afferent arteriolar resistance, glomerular hydrostatic pressure, glomerular filtration pressure, and glomerular oncotic pressure. N-acetyl-β-D glucosaminidase (NAG) and NGAL, markers of tubular injury, will be measured by a spectrophotometric method using a commercially available kit. Routine blood and urine analyses will be performed at the Diagnostic Clinic Laboratory, University Hospital of North Norway, Tromsø.

Inclusion criteria sepsis associated acute kidney injury:

• Sepsis diagnosed or suspected
• Age >18 years

Inclusion Criteria healthy controls:

• Previously healthy individuals
• Age >18 years

Exclusion Criteria:

Oliguria or renal impairment due to other causes than sepsis. Pregnancy or breast-feeding.

Intensive care patients and healthy controls