Toward a new approach for the detection of pain in adult patients undergoing cardiac surgery: near-infrared spectroscopy--a pilot study.
OBJECTIVE
This pilot study examined the discriminant validity and criterion validity of regional cerebral oxygenation measurement (rSO₂), using the near-infrared spectroscopy (NIRS) technique (INVOS-4100 system, Somanetics, Troy, MI) for measuring pain during nociceptive procedures in adults undergoing cardiac surgery.


METHODS
A repeated-measures, within-subjects design was used, and 40 adult patients participated. Data collection was completed during 2 test periods: (1) while patients were awake, before the induction of anesthesia (first test period); and (2) after the induction of anesthesia, while patients remained under the effects of anesthesia (second test period). Each test period included a baseline, a tactile stimulus (skin disinfection), nociceptive stimuli (e.g., intravenous and arterial line insertions, sternal bone incision and thorax opening), and a postprocedure evaluation.


RESULTS
Increased rSO₂ values (P < .001) were acquired during nociceptive procedures in both test periods. No significant associations were evident between rSO₂, pain behaviors, and the patient's self-report of pain intensity, but this may be attributable to a low range of variability.


CONCLUSIONS
Although further research is needed in critically ill adult patients undergoing more painful procedures, the NIRS may become a promising technique for assessing pain.