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Anesthesiology. 2005 Aug;103(2):258-68.

S-ketamine anesthesia increases cerebral blood flow in excess of the metabolic needs in humans.

Author information

1
Turku PET Centre, University of Turku, Turku, Finland. jaakko.langsjo@utu.fi

Abstract

BACKGROUND:

Animal studies have demonstrated neuroprotective properties of S-ketamine, but its effects on cerebral blood flow (CBF), metabolic rate of oxygen (CMRO2), and glucose metabolic rate (GMR) have not been comprehensively studied in humans.

METHODS:

Positron emission tomography was used to quantify CBF and CMRO2 in eight healthy male volunteers awake and during S-ketamine infusion targeted to subanesthetic (150 ng/ml) and anesthetic (1,500-2,000 ng/ml) concentrations. In addition, subjects' GMRs were assessed awake and during anesthesia. Whole brain estimates for cerebral blood volume were obtained using kinetic modeling.

RESULTS:

The mean +/- SD serum S-ketamine concentration was 159 +/- 21 ng/ml at the subanesthetic and 1,959 +/- 442 ng/ml at the anesthetic levels. The total S-ketamine dose was 10.4 mg/kg. S-ketamine increased heart rate (maximally by 43.5%) and mean blood pressure (maximally by 27.0%) in a concentration-dependent manner (P = 0.001 for both). Subanesthetic S-ketamine increased whole brain CBF by 13.7% (P = 0.035). The greatest regional CBF increase was detected in the anterior cingulate (31.6%; P = 0.010). No changes were detected in CMRO2. Anesthetic S-ketamine increased whole brain CBF by 36.4% (P = 0.006) but had no effect on whole brain CMRO2 or GMR. Regionally, CBF was increased in nearly all brain structures studied (greatest increase in the insula 86.5%; P < 0.001), whereas CMRO2 increased only in the frontal cortex (by 15.7%; P = 0.007) and GMR increased only in the thalamus (by 11.7%; P = 0.010). Cerebral blood volume was increased by 51.9% (P = 0.011) during anesthesia.

CONCLUSIONS:

S-ketamine-induced CBF increases exceeded the minor changes in CMRO2 and GMR during anesthesia.

PMID:
16052107
[Indexed for MEDLINE]

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