Background: Catecholamine release is a physiological response to stress. The extent to which perioperative stress provokes the central release of catecholamines, which modulate pain perception in the spinal cord, still remains unknown. The perioperative course of catecholamine concentrations in the cerebrospinal fluid (CSF) and plasma was examined.
Methods: A prospective study was performed in 25 patients (ASA III, 60-84 years) undergoing elective hip joint replacement in spinal catheter anesthesia. The concentrations of dopamine, epinephrine and norepinephrine in the CSF and plasma were measured before anesthesia, immediately after surgery, and 6 and 24 h post-operatively.
Results: In most patients, dopamine and epinephrine were not detectable in CSF. CSF-norepinephrine concentrations decreased from median [interquartile-range] 159 [124;216] pre-anesthesia to 116 [79;152] pmol/l immediately post-operatively and were slightly elevated 24 h post-operatively (180 [134;302] pmol/l) (P=0.05). Dopamine plasma concentrations were not detectable or were barely above the detection threshold. Plasma epinephrine increased from 61 [28;77] pmol/l pre-anesthesia to 112 [69;138] pmol/l 6 h post-operatively and returned to baseline 24 h post-operatively (P=0.001). Plasma norepinephrine concentrations increased intra-operatively from 298 [249;422] to 556 [423;649] pmol/l and remained elevated 24 h after surgery (P=0.009). There was no association between changes in CSF or plasma norepinephrine or epinephrine concentrations and changes in heart rate (HR) or mean arterial pressure (MAP).
Conclusion: During spinal anesthesia for elective hip joint replacement, norepinephrine concentrations were greater in plasma than in CSF. CSF dopamine and epinephrine concentrations were essentially undetectable. The changes in CSF-norepinephrine concentrations and the changes of plasma norepinephrine concentrations showed no association with each other; nor were there correlations between clinical stress parameters (HR, MAP) or visual analog scale pain, and the changes in CSF norepinephrine concentrations.