Pain assessment in the critically ill mechanically ventilated adult patients: Comparison between skin conductance algesimeter index and physiologic indicators :Puneet Khanna, Chandralekha Chandralekha, Ravinder Kumar Pandey, Ankur Sharma, Saudi Journal of Anaesthesia

ORIGINAL ARTICLE
Year : 2018 | Volume : 12 | Issue : 2 | Page : 204--208

Pain assessment in the critically ill mechanically ventilated adult patients: Comparison between skin conductance algesimeter index and physiologic indicators

Puneet Khanna¹, Chandralekha Chandralekha¹, Ravinder Kumar Pandey¹, Ankur Sharma²,
¹ Department of Anaesthesiology, Pain Medicine and Critical Care, All India Institute of Medical Sciences, New Delhi, India
² Department of Anaesthesiology and Critical Care, All India Institute of Medical Sciences, Jodhpur, India

Correspondence Address:
Dr. Ravinder Kumar Pandey
Department of Anaesthesiology, Pain Medicine and Critical Care, Room No. 5013, 5^th Floor Teaching Block, All India Institute of Medical Sciences, Ansari Nagar, New Delhi - 110 029
India

Abstract

Background and Objectives: Critically ill patients are unable to communicate effectively, so it is difficult to assess their pain and analgesic requirement. Skin conductance algesimeter (SCA) index is a device that primarily measures changes in skin conductance real time to assess pain. Methods: We planned this quantitative prospective observational study to assess pain in the critically ill mechanically ventilated patients in comparison to physiologic indicators such as blood pressure and heart rate. A repeated measures design was chosen, and a sample size of 180 was taken from 60 patients with sepsis, acute exacerbations of chronic obstructive pulmonary disease, community-acquired pneumonia, and postsurgical patients in the Intensive Care Unit (ICU). The two painful procedures chosen were tracheal suction and patient positioning. The data were collected at rest, at tracheal suctioning, 20 min later at positioning of the patient, and final reading 20 min later. Three testing periods, each including 4 assessments for a total of 12 pain assessments with sixty patients, were completed during each patient's ICU course. A total of six assessments were done with the patient at rest and three each with pain stimulus of tracheal suctioning and patient positioning. Results: There was a significant increase in both hemodynamic variables during painful procedures except for the heart rate during positioning. The correlation between the SCA index and Ramsay scale was negative and significant. Conclusions: This instrument might prove useful to measure pain in uncommunicative critically ill patients and to evaluate the effectiveness of analgesic treatment and adapt it.

How to cite this article:
Khanna P, Chandralekha C, Pandey RK, Sharma A. Pain assessment in the critically ill mechanically ventilated adult patients: Comparison between skin conductance algesimeter index and physiologic indicators.Saudi J Anaesth 2018;12:204-208

How to cite this URL:
Khanna P, Chandralekha C, Pandey RK, Sharma A. Pain assessment in the critically ill mechanically ventilated adult patients: Comparison between skin conductance algesimeter index and physiologic indicators. Saudi J Anaesth [serial online] 2018 [cited 2023 Mar 29 ];12:204-208
Available from: https://www.saudija.org/text.asp?2018/12/2/204/226992

Full Text

Introduction

Pain assessment for critically ill patients, especially for nonverbal patients, continues to present a challenge for clinicians and researchers.[1],[2],[3],[4] Critically ill patients are unable to communicate effectively due to tracheal intubation, reduced level of consciousness, sedation, and administration of neuromuscular blocking drugs.[5],[6],[7] When patients cannot verbally communicate the pain, as is the case for infants, patients in general anesthesia, and patients in Intensive Care Unit (ICU), there exists no gold standard for pain assessment. A fast-reacting, objective, sensitive, specific, continuous, and online method to monitor pain individually is therefore needed.

Emotional sweating is activated through skin sympathetic nerves and is not influenced by environmental temperatures within normal range, but from the cerebral cortex. Each time the skin sympathetic nervous system is activated, the palmer and plantar sweat glands are filled up. The skin resistance is reduced, and skin conductance increases before the sweat is reabsorbed and skin conductance again decreases. This creates a skin conductance peak, and the size of the peak depends on how forcefully the skin sympathetic nerve is firing.[8],[9] The skin conductance peak is specific for the stimulus, which induces the response and is evident within 1–2 s after stimulation.[10] The skin sympathetic nerves release acetylcholine that acts on muscarine receptors and is therefore not influenced by neuromuscular blockade, adrenergic receptor active agents, or changes in blood volume. Med-Storm's skin conductance algesimeter (SCA) is used to measure pain by analyzing changes in skin conductance.[10] The SCA is a device that primarily measures changes in skin conductance real time to assess pain in the patient. A skin conductance peak is defined as a minimum followed by a maximum in conductance values (mS). From the skin conductance peak, peaks per se cond and the relative area under the curve can be calculated online and used for pain assessment, typically analyzed in a sliding 15 s windows updated each second. The measurement is performed using three self-adhesive electrodes, denoted C (current), R (reference), and M (measurement) attached to palmar or plantar skin. The measurement unit uses the C and R electrodes in a feedback configuration to apply an exact and constant alternating voltage between the R and M electrodes. The return current from the M electrode is recorded, as its value provides direct information on the skin conductance. The recorded alternating current signal is subjected to advanced filtering which removes noise and interference before the signal is sent onto the display computer.[10]

We hypothesized that skin conductance algesimeter index (SCAI) may have sufficient accuracy to assess pain in the critically ill mechanically ventilated patients in comparison to physiologic indicators such as blood pressure (BP) and heart rate (HR) and has the potential to significantly improve pain treatment practices. To test this hypothesis, we compared pain assessment from the SCA with those derived and analyzed from physiologic parameters. We hypothesized that if the SCAI really measures pain, the SCAI should be much higher during painful procedures than while the patient is at rest.

Methods

A repeated measures design was chosen for this quantitative prospective observational study. A sample size of 180 from 60 patients in the ICU at AIIMS, New Delhi, was recruited for the study after Institutional Ethics Committee approval.

In the ICU, patients of more than 16 years of age of both sexes requiring tracheal intubation and mechanical ventilation were included in the study. If patients were shifted to ICU without a tracheal intubation, they were not considered eligible for the study. However, if they required tracheal intubation and mechanical intubation in the first 48 h of admission of ICU, they were recruited for the study. Patients were excluded if they were quadriplegic, receiving neuromuscular blocking medications, or had a peripheral neuropathy, pregnancy, morbid obesity, received medical treatment for chronic pain, an ejection fraction <25%, preexisting psychiatric or neurological problems, dependence on alcohol or drugs, received neuromuscular blockers following surgery, or had complications after surgery such as hemorrhage and delirium. The study was explained to eligible patient's relatives, and informed consent was obtained. The assessments of the study parameters were done in the first 48 h after tracheal intubation or if they were received in the ICU with tracheal tube in situ.

In addition to the SCAI (Med-Storm's SCA, Medstorm Innovation As, Gimle Terassi 4-0264OSLO, Norway.), invasive arterial BP and HR (from electrocardiography) were also collected, using multimodal monitors. For each patient, the SCAI and the two physiological variables were collected three times (morning, afternoon, and night). Evaluation of the SCAI and the physiological variables was made at rest and during painful procedures to appreciate the SCAI responsiveness. The two painful procedures chosen were tracheal suction and patient positioning (defined as movement during shifting of the patient in bed). The data were collected at rest, at tracheal suctioning, 20 min later at positioning of the patient, and final reading 20 min later. They were selected because their painful characters had been demonstrated in several previous studies and because they were part of the routine care that was normally planned for the patients.[11],[12],[13] The patients would be grouped in four based on number of fluctuations. The number of fluctuations of skin conductance per se cond was different between patients with no (0.07) (Group 1), mild (0.16) (Group 2), moderate (0.28) (Group 3), and severe pain (0.33) (Group 4).[14]

The patient received sedation as per institutional protocol using morphine and midazolam infusions. The patients' sedation levels were assessed using the Ramsay scale.[12] The Ramsay scale rates sedation level on a scale from 1 to 6. The level of sedation was kept as Ramsay sedation score of >3.

This was pilot study of sixty patients to assess the relationship between SCIA and physiological parameters in response to painful activity. There is no published literature to assess for formal sample size, and hence, sample size of sixty was considered as sample of convenience. The statistical test was applied to the observed parameters. The data are summarized as mean ± standard deviation. The correlations between the studied parameters were analyzed using Pearson correlation coefficient. P < 0.05 was considered statistically significant.

Results

Three testing periods, each including 4 assessments for a total of 12 pain assessments with sixty patients, were completed during each patient's ICU course. A total of six assessments were done with the patient at rest, and three each with pain stimulus of tracheal suctioning and patient positioning. The patient population included a variety from those in sepsis, with acute exacerbations of chronic obstructive pulmonary disease, community-acquired pneumonia, postsurgical, and other cases [Table 1].{Table 1}

There was a significant increase in both hemodynamic variables during painful procedures except for the heart rate during positioning [Table 2] and [Table 3].{Table 2}{Table 3}

The correlation between the SCAI and Ramsay scale was negative and significant [Figure 1]. The logical direction of the association is the higher the sedation level, the lower the ability to express painful behaviors [Table 4] and [Table 5].{Figure 1}{Table 4}{Table 5}

Discussion

Pain is one of the complaints of the patients admitted in ICU. The pain intensity varies with associated disease and also related to invasive procedures being performed over them in ICU. It has been reported that 29% of patients remembered pain in ICU, especially after invasive procedures.[15] Another study reported an occurrence of severe pain in 63% of the surgical patients.[16] All ICU patients require optimal pain medication. However, the correct dose of analgesics and sedative agents are essential. The high doses of analgesics and sedatives for the treatment of pain and anxiety have been associated to delirium, a predictor for death and prolonged need for ventilation. Some patients who recover from critical illness may suffer from long-term psychological disturbance such as posttraumatic stress disorder, anxiety, or depression. Various assessment tools have been used for assessment of pain and sedation in ICU. Acute pain assessment scores based on behavioral state and physiological responses in critically ill ICU patients are influenced by sedatives and neuromuscular blockade.

We used hemodynamic parameters of BP and HR as a marker of pain. We have chosen these two hemodynamic variables as previous studies had shown that increased heart rate and increased arterial BP are the most frequently used physiological indicators for pain assessment.[11] In hemodynamically unstable patients, the rationale for using hemodynamic measures to monitor noxious stimuli is questionable. However, it is agreed that these physiological indicators lack specificity in the ICU and can be influenced by many medications (vasopressors, adrenergic blockers, anti-arrhythmics, and sedative drugs) and pathological conditions (sepsis, shock, hypoxia, and fear).[17] Moreover, no significant correlation was found among the SCAI index and the two physiological variables in our study.

The SCA index has low interindividual variability, reacts immediately, and gives objective and continuous online reading specifically linked to the individual. Studies have demonstrated high sensitivity and specificity in detecting pain and nociceptive stimulation. The SCA monitors directly the emotional part of the sympathetic nervous system and is not influenced by hemodynamic changes, adrenergic-acting agents, or by neuromuscular blockade. The SCA may be an important tool for tailoring the use of analgesics administration to reduce pain in ICU as well as its complication.

The SCAI is more sensitive and specifically linked to pain and noxious stimuli because there is no influence by circulatory changes, cardioactive or vasoactive drugs, and neuromuscular blockade. The SCAI reacts within seconds and is specific for the individual, continuous, objective, and more sensitive and specific for assessing pain than other currently available methods during emergence from anesthesia, and the SCA reacts similarly to the EEG monitors, bispectral index, and state entropy.[17] The number of fluctuations of skin conductance per se cond was different between patients with no (0.07) (Group 1), mild (0.16) (Group 2), moderate (0.28) (Group 3), and severe pain (0.33) (Group 4); this was adapted from the previous study.[14]

It has been reported that SCA index could detect the noxious stimulation from tracheal suctioning in artificially ventilated children better than invasive arterial BP and HR when the COMFORT sedation score was used in hemodynamically stable patients.[10] The SCA might, therefore, be a more sensitive and specific tool to measure noxious stimuli in critically ill patients than other available methods.

Conclusions

The present study provides evidence that the SCA has good properties for detecting pain. This instrument might prove useful to measure pain in uncommunicative, critically ill patients and to evaluate the effectiveness of analgesic treatment and adapt it. Further studies are required to determine whether the use of this SCAI can really improve management of pain in the critical care setting.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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