The effect of posture and anaesthetic technique on the surgical pleth index.
The surgical pleth index has been shown to correlate with surrogate variables of nociception during general anaesthesia, and it has been suggested to be of use as a depth of anaesthesia monitor. However, little is known about confounding factors. As the main determining variables are based on both central and peripheral autonomic regulatory mechanisms, we hypothesised that changing a patient`s posture may produce a marked effect. We studied the effects of posture change in 45 patients who were randomly assigned to receive general (n = 15) or spinal anaesthesia with (n = 15) or without sedation (n = 15), as well as 15 awake volunteers. Mean (SD) values of the surgical pleth index after adoption of the lithotomy position were reduced from 57 (22) to 21 (6) under general anaesthesia, 63 (15) to 31 (9) under spinal anaesthesia alone, and 52 (14) to 22 (8) under spinal anaesthesia with sedation (all p < 0.01). In healthy volunteers, the surgical pleth index increased from 37 (13) to 57 (11) (p < 0.01) after 30° head-up tilt and was reduced from 35 (11) to 25 (11) after head-down tilt (p < 0.05). Change in posture has a marked effect on the surgical pleth index which lasts for at least 45 min, and this must be considered when interpreting the displayed values.
 Staff Anaesthetist.
C
C
Ilies
 Medical Student, Christian-Albrechts-University, Kiel, Germany.
J
J
Ludwigs
 Staff Anaesthetist.
M
M
Gruenewald
 Staff Anaesthetist.
C
C
Thee
 Medical Student, Christian-Albrechts-University, Kiel, Germany.
J
J
Hanf
 Professor of Anaesthesia.
R
R
Hanss
 Professor of Anaesthesia and Chair, Department of Anaesthesia and Intensive Care Medicine, University-Hospital Schleswig-Holstein, Campus Kiel, Germany.
M
M
Steinfath
 Professor of Anaesthesia.
B
B
Bein
D000328:Adult; D000368:Aged; D000768:Anesthesia, General; D000775:Anesthesia, Spinal; D000779:Anesthetics, Local; D002045:Bupivacaine; D005260:Female; D006339:Heart Rate; D006801:Humans; D006993:Hypnotics and Sedatives; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D059225:Nociception; D010880:Piperidines; D011187:Posture; D015742:Propofol; D000077208:Remifentanil; D013312:Stress, Physiological; D013997:Time Factors; D014851:Wakefulness
D000779:Anesthetics, Local; D006993:Hypnotics and Sedatives; D010880:Piperidines; D000077208:Remifentanil; D002045:Bupivacaine; D015742:Propofol