Pituitary-adrenal, hormonal changes during induced hypotension with labetol or isoflurane for middle-ear surgery.
BACKGROUND
Pituitary-adrenal secretion during induced hypotension for middle-ear surgery has received little attention. Previous work failed to differentiate the effects of induced hypotension from surgical stimulation. We have undertaken a preliminary study examining the effects of hypotension, achieved with labetalol or isoflurane, on pituitary-adrenal secretion before, during and after middle-ear surgery.


METHODS
Twenty-four patients were allocated randomly to 3 groups. The control group were anaesthetised with isoflurane, and normotension maintained for 30 min before hypotension was induced with isoflurane and surgery started. In the labetalol group, this drug was given i.v. to obtain a mean arterial pressure (MAP) of 60 mm Hg for 30 min before surgery and hypotension maintained with labetalol during the operation. In the isoflurane group, hypotension was induced to a MAP of 60 mm Hg for 30 min before surgery and continued throughout the procedure. All 3 groups received metoprolol i.v. before hypotension was established. Blood samples were collected before induction of anaesthesia, during anaesthesia alone (normotensive or hypotensive), surgery with hypotension, and recovery. They were analysed for adrenocorticotropic hormone (ACTH), arginine vasopressin (AVP), cortisol and aldosterone.


RESULTS
Induced hypotension before surgery failed to stimulate release of ACTH, AVP and cortisol. No significant increase in these hormones occurred until the postoperative period. Aldosterone concentrations increased significantly during anaesthesia and hypotension in the labetalol and isoflurane groups (P<0.05) and continued to rise significantly in all 3 groups during surgery. However, there was no significant difference in aldosterone concentration before surgery between the control and the 2 hypotensive groups.


CONCLUSIONS
ACTH, AVP and cortisol secretion were not stimulated by induced hypotension to MAP of 60 mm Hg before surgery. Increased aldosterone secretion occurred and a further study with a larger sample size is needed.
Matson
A M
AM
Department of Anaesthesia, Northwick Park Hospital, Harrow, UK.
Shaw
M
M
Loughnan
B A
BA
Burrin
J M
JM
Hall
G M
GM
D000305:Adrenal Cortex Hormones / Q000097:blood / Q000378:metabolism*; D018674:Adrenergic Antagonists / Q000008:administration & dosage / Q000627:therapeutic use*; D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage / Q000627:therapeutic use; D000324:Adrenocorticotropic Hormone / Q000097:blood / Q000378:metabolism; D000328:Adult; D000450:Aldosterone / Q000097:blood / Q000378:metabolism; D000704:Analysis of Variance; D018685:Anesthetics, Inhalation / Q000008:administration & dosage*; D000959:Antihypertensive Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D001127:Arginine Vasopressin / Q000097:blood / Q000378:metabolism; D001794:Blood Pressure / Q000187:drug effects; D004432:Ear, Middle / Q000601:surgery*; D005500:Follow-Up Studies; D006801:Humans; D006854:Hydrocortisone / Q000097:blood / Q000378:metabolism; D007023:Hypotension, Controlled; D007275:Injections, Intravenous; D007530:Isoflurane / Q000008:administration & dosage*; D007741:Labetalol / Q000008:administration & dosage / Q000627:therapeutic use*; D008790:Metoprolol / Q000008:administration & dosage / Q000627:therapeutic use; D010100:Oxygen / Q000097:blood; D010907:Pituitary Hormones / Q000097:blood / Q000378:metabolism*; D010913:Pituitary-Adrenal System / Q000187:drug effects* / Q000378:metabolism; D018401:Sample Size
D000305:Adrenal Cortex Hormones; D018674:Adrenergic Antagonists; D000319:Adrenergic beta-Antagonists; D018685:Anesthetics, Inhalation; D000959:Antihypertensive Agents; D010907:Pituitary Hormones; D001127:Arginine Vasopressin; D000450:Aldosterone; D000324:Adrenocorticotropic Hormone; D007530:Isoflurane; D008790:Metoprolol; D007741:Labetalol; D010100:Oxygen; D006854:Hydrocortisone