Satsumae et al. Anesth Analg 2001; 92:1286-9

Reviewed by: R. Prasad, MD

Summary:

• 85 ASA I-II pts, 14-68yo for knee surgery with tourniquet under GA. 9 excluded because tourniquet time <60min; not listed in table below.
• Premed diazapan, ranitidine. Thiamylal induction, vecuronium, sevo 1.5-2.5%, 66% N2O
• Sevo adjusted to keep BP and HR within 20% baseline
• Ketamine given, anesthesiologist blinded to dose (see below). 10 or more minutes later, tourniquet inflated (300 mmHg) and incision made.

• Variables measured:
• BP, HR q10min x 60min.
• POD#1: psychological sx (hallucinations, nightmares)
• Results:
• Large, Small
• SBP, DBP unchanged
• % pts with HTN (SBP inc more than 30%): ~5%
• no psych sx
• Control
• SBP inc at 40, 50, 60 min
• DBP inc at 50, 60 min
• % pts with HTN (SBP inc more than 30%): ~40%
• Discussion: study limitations
• Cannot prove causal relationship btwn tourniquet-pain and tourniquet-HTN, since study done under GA.
• Did not measure BIS or other EEG - do not know if depth of anesthesia similar across groups
• Comments:
• As authors suggest in discussion, it would be nice to try this in awake patients to see if incidence of tourniquet-pain is decreased without causing psychiatric symptoms. Probably would need larger n, however.
• Depth not monitored. It is not clear when ketamine was given, in relation to anesthesia induction and subsequent titration of sevo levels to get to within 20% of baseline HR and BP. If ketamine was given early, it could have caused an elevation in BP. In that case, sevo would have been titrated to higher levels. This would mean that the study groups were at a deeper level of anesthesia, and the comparison is between unequal groups.