From the Center for Pain and the Brain, Harvard Medical School, Boston, Massachusetts; the Department of Neuroscience, Research Center of the University of Montreal Hospital Center, University of Montreal, Montreal, Quebec, Canada.
From the Center for Pain and the Brain, Harvard Medical School, Boston, Massachusetts.
Anesthesiology. 2021 Nov 1;135(5):877-892. doi: 10.1097/ALN.0000000000003986.
Patients undergoing surgical procedures are vulnerable to repetitive evoked or ongoing nociceptive barrage. Using functional near infrared spectroscopy, the authors aimed to evaluate the cortical hemodynamic signal power changes during ongoing nociception in healthy awake volunteers and in surgical patients under general anesthesia. The authors hypothesized that ongoing nociception to heat or surgical trauma would induce reductions in the power of cortical low-frequency hemodynamic oscillations in a similar manner as previously reported using functional magnetic resonance imaging for ongoing pain.
Cortical hemodynamic signals during noxious stimuli from the fontopolar cortex were evaluated in two groups: group 1, a healthy/conscious group (n = 15, all males) where ongoing noxious and innocuous heat stimulus was induced by a contact thermode to the dorsum of left hand; and group 2, a patient/unconscious group (n = 13, 3 males) receiving general anesthesia undergoing knee surgery. The fractional power of low-frequency hemodynamic signals was compared across stimulation conditions in the healthy awake group, and between patients who received standard anesthesia and those who received standard anesthesia with additional regional nerve block.
A reduction of the total fractional power in both groups-specifically, a decrease in the slow-5 frequency band (0.01 to 0.027 Hz) of oxygenated hemoglobin concentration changes over the frontopolar cortex-was observed during ongoing noxious stimuli in the healthy awake group (paired t test, P = 0.017; effect size, 0.70), and during invasive procedures in the surgery group (paired t test, P = 0.003; effect size, 2.16). The reduction was partially reversed in patients who received a regional nerve block that likely diminished afferent nociceptive activity (two-sample t test, P = 0.002; effect size, 2.34).
These results suggest common power changes in slow-wave cortical hemodynamic oscillations during ongoing nociceptive processing in conscious and unconscious states. The observed signal may potentially promote future development of a surrogate signal to assess ongoing nociception under general anesthesia.
接受手术的患者易受到重复诱发或持续传入伤害性刺激的影响。作者使用功能近红外光谱技术，旨在评估健康清醒志愿者和全身麻醉下接受手术的患者在持续伤害性感受时皮质血流动力学信号功率的变化。作者假设，与之前使用功能磁共振成像评估持续性疼痛时所报道的情况类似，持续的热或手术创伤会导致皮质低频血流动力学振荡的功率降低。
在两组患者中评估额极皮质有害刺激时的皮质血流动力学信号：第 1 组为健康/清醒组（n = 15，均为男性），通过接触式热刺激器刺激左手背部来产生持续的有害和无害热刺激；第 2 组为患者/无意识组（n = 13，3 名男性），接受全身麻醉并进行膝关节手术。在健康清醒组中比较了不同刺激条件下低频血流动力学信号的分数功率，并比较了接受标准麻醉的患者与接受标准麻醉加区域神经阻滞的患者之间的差异。
在健康清醒组中，观察到在持续有害刺激时，两组的总分数功率均降低（特别是额极皮质区含氧血红蛋白浓度变化的慢-5 频带（0.01 至 0.027 Hz）降低）（配对 t 检验，P = 0.017；效应量，0.70），在手术组中，在侵袭性操作过程中也观察到这种情况（配对 t 检验，P = 0.003；效应量，2.16）。在接受区域神经阻滞的患者中，这种降低部分逆转，这可能减弱了传入伤害性活动（两样本 t 检验，P = 0.002；效应量，2.34）。
这些结果表明，在有意识和无意识状态下持续伤害性感受处理过程中，慢波皮质血流动力学振荡的功率存在共同变化。观察到的信号可能有助于未来开发替代信号，以评估全身麻醉下的持续伤害感受。
