Plasma norepinephrine concentrations ([NE]) when raised in patients with sepsis are thought to indicate increased activity of the sympathetic nervous system (SNS). However, increased SNS activity may occur without a concomitant rise in plasma [NE]. Measurement of NE kinetics (clearance and spillover) is a more accurate and direct assessment of SNS activity. In the present study plasma [NE] and NE kinetics were measured in six patients with intra-abdominal sepsis (septic) using tritiated NE infused to achieve a plateau plasma concentration. The measurements were repeated in the same patients after they had recovered (nonseptic). NE clearance and spillover were both significantly higher (P < 0.05) in the septic compared with the nonseptic state. However, there was no statistically significant difference in plasma [NE] between the two conditions. Plasma [NE] indicates no alteration in SNS activity during the septic state, whereas NE kinetics indicate increased activity of the SNS during sepsis. The results suggest that plasma [NE] is a poor indicator of SNS activity during septic illness.

Serum carnitine levels have been measured in 178 samples from 75 normal volunteers. We report a wide range of values (10-70 mumol/liter and 8-74 mumol/liter for free and acetylated carnitine, respectively) and a distinct difference between the ranges for males and females (p less than 0.001). There is also substantial, seemingly random fluctuation in any one individual's levels, when measured serially over several weeks.

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