Hormonal responses and pharmacokinetics after intradural (spinal) morphineand general anaesthesia for abdominal aortic surgery

Objective: The purpose of this clinical study was to record the hormonal re sponses to abdominal aortic surgery, under intradural morphine combined wit h general anaesthesia. Methods: Twelve patients, scheduled for elective abdominal aortic surgery r eceived, before surgery, 0.05 mg/kg morphine intradurally combined with gen eral anaesthesia. Preanaesthetic plasma concentrations of adrenocorticotrop hic hormone (ACTH), beta-endorphin (beta-END), cortisol, thyroid stimulatin g hormone (TSH), human growth hormone (HGH), epinephrine (E) and norepineph rine (NE), CSF concentrations of ACTH and beta-END, acid-base balance, plas ma potassium, lactate and blood glucose were compared with the values recor ded after tracheal intubation, peritoneal incision, aortic cross-clamping, revascularisation and 6 hours after surgery. Results: Tracheal intubation produced no significant changes in plasma conc entrations of ACTH and beta-END, TSH, HGH and norepinephrine and CSF concen trations of ACTH and beta-END. Plasma concentrations of cortisol and epinep hrine decreased. Peritoneal incision produced a significant increase in pla sma concentrations of ACTH, beta-END, HGH and NE, while the CSF concentrati ons of beta-END decreased. After aortic-cross clamping, the plasma concentr ations of ACTH, beta-END and norepinephrine were significantly higher than the preanaesthetic values. After revascularisation, plasma concentrations o f beta-END and norepinephrine were significantly higher than the baseline v alues. Postoperative values showed an increased plasma concentration of nor epinephrine only. Analgesia lasted 19 hours (6 to 48 hours). Conclusions: Preoperative intradural injection of 0.05 mg/kg morphine combi ned with general anaesthesia, produced sufficient protection of hormonal re sponses to tracheal intubation. This technique of anaesthesia did not prote ct the patient against peritoneal incision, aortic dissection and aortic cr oss-clamping by the increase in ACTH, beta-END, HGH and NE, despite a decre ase in CSF beta-END. However, no significant increase in cortisol and epine phrine plasma concentrations were found during the whole study. The hormona l responses to revascularisation were less intense than the previous two su rgical periods. At 6 hours postoperatively, no significant hormonal change were found in comparison with the baseline values, Sympathetic activity was moderately increased after peritoneal incision until the end of the study. This can be considered a favourable factor in maintaining stable haemodyna mics during elective abdominal aortic surgery. Profound spinal and supraspi nal morphine analgesia produced by the lone presence of morphine in the CSF by a very low clearance, offers stable haemodynamics during surgery and a favourable postoperative clinical condition by blocking the peripheral noci ceptive stimuli.