Comparison of the Skin Conductance Values and Patient Pain Scores During Minor Procedures in the ICU

Although pain must be assessed to be treated, it has been challenging to obtain consistent, objective, and quantifiable measurements. The best methods currently available are subjective scales communicated by the patient such as standardized sentences, visual analog scales (VAS), or plain numeric scales.

When a patient is unable to communicate, methods used to monitor pain are inadequate. A device that provides an objective assessment of pain in these patients would alert the patient's caregivers that the patient may be in pain and analgesic treatment is indicated.

Various methods (Evans et al, 2013; Kantor, 2014; Isnardon, 2013) have been proposed to monitor patients' reactions to nociceptive stimulation such as:

• changes in heart rate or blood pressure
• changes in microcirculation
• pupillometry
• EEG
• Auditory or somatosensory evoked potentials

All of these methods have been found lacking, mostly due to a lack of specificity for pain. Pupillometry is not suitable for long periods of measurement and is sensitive to concomitant treatment (e.g. opioids).

Galvanometry has the potential to provide specific information related to pain in patients who are unable to communicate.

Since sweat glands are the only organs controlled solely by the sympathetic nervous system, there is a reasonable chance that the use of galvanometry can provide a reliable means of assessing pain. There are numerous papers on this topic; searching in PUBmed on the key words "pain" and "skin conductance" results in more than 250 papers (selected references are included in the list below). The PainMonitor system uses galvanometry to monitor changes in skin conductance responses per sec mirroring the number of bursts in the skin sympathetic nerves. This creates a warning for caregivers to assess the potential that the patient is in pain.

Inclusion criteria

• Patients between the ages of 18-89 years (inclusive), in an adult ICU
• Patients admitted to the ICU who are able to communicate their pain and anxiety using a VAS
• Patients must be cooperative and not agitated.
• Planned to have a potentially painful procedure

Exclusion criteria

• Diagnosed neuropathic disease
• Use of neostigmine within the past 3 hours
• Use of regional anesthesia at the extremity where the device electrodes are placed