Chronic Pain in COVID-19 Patients Discharged From Intensive Care Unit

as defined by ICD-11 and the International Association for the Study of Pain (IASP)

Chronic secondary pain is organized into the following six categories:

1. Chronic cancer-related pain (ICD-11 code MG30.1)
2. Chronic postsurgical or post-traumatic pain (ICD-11 code MG30.2)
3. Chronic secondary musculoskeletal pain (ICD-11 code MG30.3)
4. Chronic secondary visceral pain (ICD-11 code MG30.4)
5. Chronic neuropathic pain (ICD-11 code MG30.5)
6. Chronic secondary headache or orofacial pain (ICD-11 code MG30.6)

For each category of detected pain the frequency will be reported.

Pain sensitivity level is tested with a Pain sensitivity questionnaire (PSQ). PSQ contains 17 items assessing pain with 11 level scoring from 0 (not at all painful) to 10 (most severe pain imaginable). Maximal summation score is 170, higher score mean worse outcome.

A Michigan Body Map will be used for pain localization inventory. A Michigan Body Map is a self-report measure to assess body areas where chronic pain is experienced.

A Brief Pain Inventory (BPI) will be used to assess the severity of pain and its impact on functioning. The BPI pain scales defines pain as follows: Worst Pain Score: 1 - 4 = Mild Pain. Worst Pain Score: 5 - 6 = Moderate Pain. Worst Pain Score: 7 - 10 = Severe Pain. BPI Interference Items use 0 (less) to 10 (worth) scoring, the arithmetic mean of the interference items is used as a measure of pain interference, higher score mean worse outcome.

A DN4 scale will be used to detect a neuropathic pain. The DN4 (which stands for Douleur Neuropathique 4) is a clinician-administered questionnaire consisting of 10 items. Seven items related to pain quality (i.e. sensory and pain descriptors) are based on an interview with the patient and 3 items based on the clinical examination. Each item has binary value (yes/no), maximal summation score is 10, and the threshold for neuropathic pain is 4.

Spiegel Sleep Questionnaire is a self-rated questionnaire which assesses the current sleep quality and disturbances. It has six 5 point Likert-like items rated from worst to best value. The total summation score is 30, less score values indicates worth outcome. The threshold of bad sleep is less than 15, and the score 20 indicates a good sleep.

Posttraumatic Stress Disorder Checklist Scale is a 20-item self-report measure that assesses the symptoms of Posttraumatic Stress Disorder. Respondents rate each item from 0 ("not at all") to 4 ("extremely") to indicate the degree to which they have been bothered by that particular symptom over the past month.

A total symptom severity score is obtained by summing the scores for each of the 20 items. The score superior of 31 is indicative of probable Posttraumatic Stress Disorder.

Hospital Anxiety Depression scale will be used, it measures anxiety and depression in a general medical population of patients. The questionnaire comprises seven questions for anxiety and seven questions for depression. Greater score values indicates worth outcome.

For both scales, scores of less than 7 indicate non-cases; 8-10 - mild depression or anxiety; 11-14 - moderate depression or anxiety; and 15-21 - severe depression or anxiety.

Pain Catastrophizing Scale quantifies an individual's pain experience. It has 13 items rated on 5-point Likert-like scales (0 - not at all to 4 - all the time). A total score is yielded (ranging from 0-52), the threshold above 30 is considered clinically relevant. Higher score indicates higher level of catastrophizing and bad outcome.

Perceived Stress Scale (PSS-10) is a self stress assessment instrument. It has 10 items rated on 5-point Likert-like scales (0 - never to 4 - very often). Individual scores on the PSS-10 can range from 0 to 40 with higher scores indicating higher perceived stress.

Mechanical temporal summation will be evoked using methodology described by Weissman-Fogel, 2008, by Von Frey Filaments, using a 180-gr filament that will be applied to the volar aspect of the dominant forearm. Patients will be exposed to a single stimulus and will be asked to rate the level of pinprick pain intensity using 11 items numeric pain scale. This pain score serve as an index for mechanical suprathreshold pain. Subsequently, 1 Hz repetitive stimuli will be applied within an area of 1 cm in diameter, using the same filament, and subjects will be asked to rate the pain intensity of the last stimulus. The magnitude of mechanical temporal summation will be calculated as the difference between the last and the first pain scores. Higher values indicates worth outcome.

A heat pain threshold will be realized using Thermal Stimulator for Sensory testing (SOMEDIC(R)). A thermode (heating stick) of 7 square centimeters will be applied to the volar aspect of the dominant forearm. Patients will be exposed to 3 repetitive gradual increase in temperature from 32° to 52°C. The skin contact will be withdrawn if an individual is not able to tolerate such stimulation, and the temperature threshold of tolerance will be noted. The final reading will be the median of three measurements, higher values indicate better tolerance.