Phase 1 (started in July 2019):
Central Sensitization Inventory (CSI), Fear-Avoidance Components Scale (FACS), pain-pressure threshold are factors associated with chronic post-hysterectomy pain (CPHP), but a complete understanding on the development of CPHP is lacking. The study aims to identify clinically-relevant factors for CPHP that can be reliably assessed preoperatively.
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Phase 2 (anticipated start May 2022):
In addition to above factors, the association between heart rate variability (HRV) parameters, anxiety level, anticipated pain, and anticipated analgesia requirement with significant postoperative pain and CPHP will be investigated.
Age 21 to 80 years old
American Society of Anesthesiologists Physical Scale (ASA) I to III
Benign gynaecological indications for hysterectomy
Elective abdominal or laparoscopic hysterectomy
Vaginal hysterectomy
Uterine prolapse, endometriosis, malignant disease, or pelvic pain as main indication for surgery
History of drug dependence or recreational drug use
History of chronic pain syndrome
Women scheduled for elective abdominal or laparoscopic hysterectomy at KK Women's and Children's Hospital, Singapore.
Cohort
Prospective
Pain-Pressure Threshold
Diagnostic testPerformed on bilateral trapezius muscles. Pressure will be applied at 90 degrees downward with an algometer, with the speed of pressure increase approximately 1kgf/s. Upon the sensation of pain, the patient will vocalize or raise her hand to terminate the test, and the highest reading will be recorded (up to maximum 6kgf). If two values are recorded within 0.2kgf of each other, the mean value will be recorded. If two values are greater than 0.2kgf of each other, a third test will be performed and the mean obtained.
Mechanical Temporal Summation
Diagnostic testPinprick hyperalgesia will be evoked using a Von Frey filament, applied to the volar aspect of the dominant forearm. Participants will report using the numerical rating scale the intensity of pain from the first stimulus. Subsequently, ten repetitive stimuli one second apart will be applied with the same filament within an area of 1cm diameter of the same forearm. Subjects will report the rate the pain intensity of the tenth stimulus. The magnitude of MTS is calculated as the difference between the last to the first pain scores. The investigators will classify the participants according to "evoked MTS" if the last stimulus is rated higher than the first, or "no MTS" if the last stimulus is rated equal or lower than the first. The research team administering the test will follow a set script.
Hospital Anxiety and Depression Scale
Diagnostic testStandardized questionnaire to determine the level of anxiety and depression.
Pain Catastrophizing Scale
Diagnostic testStandardized questionnaire to determine the level of pain catastrophizing.
Central Sensitization Inventory
Diagnostic testStandardized questionnaire to determine the level of central sensitization.
Fear-Avoidance Component Score
Diagnostic testStandardized questionnaire to determine the level of fear and avoidance.
EQ-5D
Diagnostic testStandardized questionnaire to assess generic health-related quality of life.
heart rate variability
Diagnostic testHeart rate variability will be determined from the R-to-R intervals obtained from a 5-minute ECG recording.
Anxiety, anticipated pain, anticipated analgesia
Diagnostic testPreoperative anxiety (0 to 100), anticipated pain (0 to 100), and anticipated analgesia requirement (0 to 5).
State-trait anxiety inventory
Diagnostic testStandardized questionnaire to assess anxiety.
Beck's Depression Inventory
Diagnostic testStandardized questionnaire to assess depressive symptoms.
Chronic Post-Hysterectomy Pain at 4 months
The primary outcome measure is the development of chronic post-hysterectomy pain, which is defined as pain that lasts for at least 3 months around the surgical site, lower abdominal, or pelvic region. This will be determined by phone or online assessment at 4 months after surgery, based on the protocol used by Brandsborg et al and the investigators' previous study.
Significant postoperative pain at 24 hours
Numerical pain score (0: no pain; 100: worst pain imaginable) will be assessed at 24 hours after hysterectomy with patient moving from supine to sitting position.
Central Sensitization Inventory (CSI)
Assessment via the validated Central Sensitization Inventory (CSI) questionnaire prior to hysterectomy. Central sensitization is defined as an increased responsiveness of nociceptive neurons in the central nervous system to normal or sub-threshold afferent stimuli. The CSI a 25-item questionnaire, with each item rated 0 to 4. A higher value indicates greater central sensitization, and a threshold score of 40 was shown to be associated with increased risk of chronic pain.
Fear Avoidance Components Scale (FACS)
Assessment via the validated Fear Avoidance Components Scale (FACS) questionnaire prior to hysterectomy. Fear-avoidance is defined as the negative emotional perception of pain as terrorizing, which can generate catastrophic thoughts and vigilance. Pain fear-avoidance behavior can be assessed with the FACS, a 20-item questionnaire, with each item rated 0 to 5.
Hospital Anxiety and Depression Scale (HADS)
Assessment via the validated Hospital Anxiety and Depression Scale (HADS) questionnaire prior to hysterectomy. Anxiety and depression are known risk factors associated with CPHP. HADS is a combination test for both anxiety and depression, is a 14-item questionnaire, with each item rated 0 to 3. HADS \> 8 has been associated specifically with increased CPHP.
Pain Catastrophizing Scale (PCS)
Assessment via the validated Pain Catastrophizing Scale (PCS) questionnaire prior to hysterectomy. Pain catastrophizing refers to the negative thought processes patients have when they are exposed to pain or painful experiences. The PCS is a 13-item scale, with each item rated on a 5-point scale: 0 (Not at all) to 4 (all the time). It is broken into three subscales being magnification (0-12), rumination (0-16), and helplessness (0-24). A higher value in each subscale indicates a higher tendency to that subscale (worse outcome).
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