Conditioned pain modulation and situational pain catastrophizing as preoperative predictors of pain following chest wall surgery: a prospective observational cohort study

Abstract

Background: Variability in patients' postoperative pain experience and response to treatment challenges effective pain management. Variability in pain reflects individual differences in inhibitory pain modulation and psychological sensitivity, which in turn may be clinically relevant for the disposition to acquire pain. The aim of this study was to investigate the effects of conditioned pain modulation and situational pain catastrophizing on postoperative pain and pain persistency.

Methods: Preoperatively, 42 healthy males undergoing funnel chest surgery completed the Spielberger's State-Trait Anxiety Inventory and Beck's Depression Inventory before undergoing a sequential conditioned pain modulation paradigm. Subsequently, the Pain Catastrophizing Scale was introduced and patients were instructed to reference the conditioning pain while answering. Ratings of movement-evoked pain and consumption of morphine equivalents were obtained during postoperative days 2-5. Pain was reevaluated at six months postoperatively.

Results: Patients reporting persistent pain at six months follow-up (n = 15) were not significantly different from pain-free patients (n = 16) concerning preoperative conditioned pain modulation response (Z = 1.0, P = 0.3) or level of catastrophizing (Z = 0.4, P = 1.0). In the acute postoperative phase, situational pain catastrophizing predicted movement-evoked pain, independently of anxiety and depression (β = 1.0, P = 0.007) whereas conditioned pain modulation predicted morphine consumption (β = -0.005, P = 0.001).

Conclusions: Preoperative conditioned pain modulation and situational pain catastrophizing were not associated with the development of persistent postoperative pain following funnel chest repair. Secondary outcome analyses indicated that conditioned pain modulation predicted morphine consumption and situational pain catastrophizing predicted movement-evoked pain intensity in the acute postoperative phase. These findings may have important implications for developing strategies to treat or prevent acute postoperative pain in selected patients. Pain may be predicted and the malfunctioning pain inhibition mechanism as tested with CPM may be treated with suitable drugs augmenting descending inhibition.

Figure 1. Schematic illustration of the study protocol.

(A) The day before scheduled surgery patients completed the Spielberger's State-Trait Anxiety Inventory (STAI) and Beck's Depression Inventory (BDI); (B) Then patients underwent a conditioned pain modulation paradigm in which a baseline pressure pain threshold was measured at the quadriceps muscle followed by a conditioning painful stimulus induced by a cold pressor test (CPT) (i.e., hand immersion in an ice water bath for 120 seconds). After 120 seconds of hand immersion (or upon spontaneous hand removal) the pressure pain threshold at the quadriceps muscle was reassessed. The Situational Pain Catastrophizing Scale (S-PCS) was re-administered within five minutes after cold pressor test and patients were instructed to reference the cold pressor pain while answering; (C) From postoperative days 2–5 pain-related outcomes were assessed, including postoperative movement-evoked pain intensity, morphine consumption, and an integrated analgesic assessment score based on the aforementioned; (D) Persistent postoperative pain was assessed according to responses to the Brief Pain Inventory – Short Form (BPI) at six months.

Figure 2. Flow chart.

Illustration of the patient selection process, reasons for exclusion and number of patients analyzed for the primary and secondary outcomes.

Figure 3. Preoperative situational pain catastrophizing and postoperative movement-evoked pain.

Adjusted means (filled circles) with 95% confidence intervals (continuous solid lines) of the patient's postoperative movement-evoked pain intensity (NRS 0–10) given different log-transformed values of preoperative situational pain catastrophizing (log[S-PCS]), adjusted for anxiety and depression by averaging across the values of the state part of the Spielberger's State-Trait Anxiety Inventory (STAI) and Beck's Depression Inventory (BDI) (average marginal values). The hollow circles represent overlaid scatterplots of log[S-PCS] versus postoperative movement-evoked pain intensity.

Figure 4. Preoperative conditioned pain modulation and postoperative morphine consumption.

Adjusted means (filled circles) with 95% confidence intervals (continuous solid lines) of the patient's postoperative morphine consumption given different values of preoperative conditioned pain modulation (CPM %). The hollow circles represent overlaid scatterplots of CPM % versus postoperative morphine consumption.