A Preliminary Study on the Effects of Self-Reported Dietary Caffeine on Pain Experience and Postoperative Analgesia

Abstract

Background: Caffeine reduces the amount of analgesic medications necessary to provide postoperative pain (POP) relief and augments treatments for headaches and dental pain. Despite considerable evidence of its beneficial effects, little is understood about the role of dietary caffeine consumption on baseline pain sensitivity or POP following oral surgery.

Method: Baseline experimental pain testing (quantitative sensory testing [QST]) using four stimulus modalities was conducted on 30 healthy adults (53% females) before surgical extraction of four third molars. Self-reported caffeine ingestion was reported before QST, and on the day of surgery, preoperative and postoperative caffeine plasma concentrations (CPC) were measured by mass spectrometry. POP ratings were obtained at timed intervals.

Results: In QST, compared to subjects who self-reported no caffeine intake, those who self-reported caffeine ingestion demonstrated a higher pain sensitivity, particularly, on ramp and hold sustained heat at 44°C and 46°C, as well as a lower heat pain threshold and tolerance (p=0.05). Differences approached significance (p=0.06) in POP between subjects with CPC above 300 ng/mL and those with CPC below 300 ng/mL. Specifically, those with >300 ng/mL CPC had a slightly lower POP (mean 2.43, range 0-5) compared to those with <300 ng/mL CPC whose POP ratings were slightly higher (mean 2.89) with a greater variability (range 0-9.5).

Conclusions: Self-reported, dietary caffeine intake was associated with higher QST ratings with lower threshold and tolerance particularly on heat pain modalities. External factors (i.e., analgesic dosage) may have played a role in the analgesic effects of caffeine on POP in oral surgery, especially in individuals with CPC exceeding 300 ng/mL who reported lower pain.

FIG. 1.

Timeline for baseline quantitative sensory testing and same-day surgery assessments. The top box (A) indicates the timing and protocol procedures for the baseline experimental testing session and related procedures, which were conducted 2–9 days before the day of surgery. The numbers below the line represent approximate time in minutes for the various components of the testing. The bidirectional arrow pointing to thermal pain and pressure pain indicate that these pain tasks were counter balanced. The bottom box (B) indicates an approximate timeline and protocol procedures conducted on the day of surgery.

FIG. 2.

Group differences in baseline experimental heat pain threshold and tolerance between participants with self-reported caffeine versus without self-reported caffeine. *p<0.05; **p<0.01. HPTh, heat pain threshold; HPTO, heat pain tolerance. Self-report was based on ingestion of caffeine within 4 hours before baseline experimental testing. With self-reported caffeine (n=5; 16.67%); without self-reported caffeine (n=25; 83.33%).

FIG. 3.

Group differences in baseline experimental pain modalities and ratings between participants with self-reported caffeine versus without self-reported caffeine. *p<0.05. Experimental pain modalities: RH, “ramp and hold” (sustained heat) at 44°C, 46°C, 48°C; TS, temporal summation at 49°C and 52°C; CP_INT, cold pressor intensity; CP_UNPL, cold pressor unpleasantness. Caffeine ingested and self-reported within 4 hours before baseline experimental testing. With self-reported caffeine (n=5; 16.67%); without self-reported caffeine (n=25; 83.33%).

FIG. 4.

Individual postoperative caffeine plasma concentrations and postoperative pain levels 6 hours after Surgery. ♦ represents 1 subject rating. ■ represents 2 subjects' ratings. ● represents 3 subjects' ratings. R²=0.505; p=0.064.