Perceived Pain Intensity Research Articles

Routine procedures in NICUs: factors influencing pain assessment and ranking by pain intensity.

Pain associated with routine procedures in NICUs is often inadequately managed. Barriers to more appropriate pain management are nurses' and physicians' knowledge and the challenges of collaborative decision-making. Few studies describe the differing perceptions of procedural pain intensity among nurses and physicians in NICUs which could complicate common decision-making. This study set out to explore the factors influencing pain intensity assessment and to gain insight into a possible pain intensity classification of routine procedures in the NICU. A survey was conducted among 431 neonatal health care professionals from 4 tertiary level NICUs. Each routine procedure was assessed on a 10-point visual analogue scale (VAS) assuming absence of analgesia. Multiple ANCOVA models showed that nurses rated 19 of the 27 procedures as significantly more painful than did physicians (p<0.05). We found no differences in pain assessment based on professional experience, gender or age. Of the 27 procedures listed, 70% were rated as painful and 44% were judged very painful. Ranking and classification of the pain intensity of routine procedures were drawn up. The general ranking of the median across all procedures shows that "insertion of a thoracic drain" is assessed as the most painful procedure. The majority of routine procedures in an NICU are considered to be painful. Nurses generally rate procedures as more painful than do physicians. This difference in assessment deserves exploration in regard to its impact on collaborative decision-making in neonate pain management.

Routine procedures in NICUs: factors influencing pain assessment and ranking by pain intensity.

Pain associated with routine procedures in NICUs is often inadequately managed. Barriers to more appropriate pain management are nurses' and physicians' knowledge and the challenges of collaborative decision-making. Few studies describe the differing perceptions of procedural pain intensity among nurses and physicians in NICUs which could complicate common decision-making. This study set out to explore the factors influencing pain intensity assessment and to gain insight into a possible pain intensity classification of routine procedures in the NICU. A survey was conducted among 431 neonatal health care professionals from 4 tertiary level NICUs. Each routine procedure was assessed on a 10-point visual analogue scale (VAS) assuming absence of analgesia. Multiple ANCOVA models showed that nurses rated 19 of the 27 procedures as significantly more painful than did physicians (p<0.05). We found no differences in pain assessment based on professional experience, gender or age. Of the 27 procedures listed, 70% were rated as painful and 44% were judged very painful. Ranking and classification of the pain intensity of routine procedures were drawn up. The general ranking of the median across all procedures shows that "insertion of a thoracic drain" is assessed as the most painful procedure. The majority of routine procedures in an NICU are considered to be painful. Nurses generally rate procedures as more painful than do physicians. This difference in assessment deserves exploration in regard to its impact on collaborative decision-making in neonate pain management.

Reducing pain in patients undergoing cardiac surgery after implementation of a quality improvement postoperative pain treatment program

Purpose The aim of this study was to test the effectiveness of a quality improvement postoperative pain treatment program after cardiac surgery. Materials and Methods This was a prospective, quasiexperimental study using nonequivalent groups comprising 3 periods: baseline (group baseline), implementation of the algorithm for acute pain management, and reassessment (group reassessment). Inclusion of 133 patients after elective cardiac surgery at an 18-bed surgical intensive care unit (SICU) at a Swiss university hospital. The algorithm was implemented by training, pocket guidelines, regular audits, and feedback. The implementation period was completed when the adherence to 2 of 3 process indicators attained at least 70% over 2 months. Visual analog scales (VAS) for pain, morphine consumption, pain perception, and sleep quality were assessed during stay in SICU and after 1 month and 6 months. Results The assessment included 79 patients at baseline and 54 in the reassessment periods. Pain intensity at rest decreased from 2.7 ± 1.4 to 2.2 ± 1.4 cm (VAS; P = .008). Retrospective perception of pain intensity at rest decreased from 3.8 ± 2.2 to 2.6 ± 1.8 ( P = .004). The proportion of patients with no pain or often without pain increased from 11% to 37% ( P = .005). The number of patients with sleep disturbances decreased from 68% to 35% ( P = .012). No differences were observed at 1 and 6 months postoperatively. Conclusions After algorithm implementation in the SICU, pain intensity at rest decreased and quality of sleep improved.

Experimentally Induced Mood Changes Preferentially Affect Pain Unpleasantness

Our group previously demonstrated that changes in mood induced by pleasant or unpleasant odors affect the perceived unpleasantness of painful heat stimuli, without significantly altering perceived pain intensity. In the present study, we examined whether changing mood by viewing emotionally laden visual stimuli also preferentially alters pain unpleasantness. Twelve female subjects immersed their right hand in hot water while observing a video showing a person experiencing the same type of pain (ie, model condition), unpleasant scenes not involving people (ie, disasters condition), or a cityscape video (ie, cityscape condition). Subjects were asked to rate pain intensity, pain unpleasantness, mood, anxiety/calmness, and video unpleasantness, and their skin conductance was measured throughout the experiment. Pain unpleasantness (but not intensity) ratings were higher during the disasters condition, which was associated with the worst mood, than during the cityscape condition; neither mood nor pain unpleasantness was altered in the model video compared with the cityscape video. Moreover, mood was significantly correlated with pain unpleasantness but not with pain intensity. Because these results are similar to those observed when odors were used to alter mood, we conclude that the effects of mood on the affective components of pain are independent of mood induction technique used. This article provides new evidence that changes in mood affect the pain experience by preferentially modulating pain unpleasantness. This finding could potentially help health professionals to treat pain symptoms in patients with altered mood, suggesting methods of pain management aimed at easing the affective, along with the sensory, components of pain.

Determinants of laser-evoked EEG responses: pain perception or stimulus saliency?

Although laser-evoked electroencephalographic (EEG) responses are increasingly used to investigate nociceptive pathways, their functional significance remains unclear. The reproducible observation of a robust correlation between the intensity of pain perception and the magnitude of the laser-evoked N1, N2, and P2 responses has led some investigators to consider these responses a direct correlate of the neural activity responsible for pain intensity coding in the human cortex. Here, we provide compelling evidence to the contrary. By delivering trains of three identical laser pulses at four different energies, we explored the modulation exerted by the temporal expectancy of the stimulus on the relationship between intensity of pain perception and magnitude of the following laser-evoked brain responses: the phase-locked N1, N2, and P2 waves, and the non-phase-locked laser-induced synchronization (ERS) and desynchronization (ERD). We showed that increasing the temporal expectancy of the stimulus through stimulus repetition at a constant interstimulus interval 1) significantly reduces the magnitudes of the laser-evoked N1, N2, P2, and ERS; and 2) disrupts the relationship between the intensity of pain perception and the magnitude of these responses. Taken together, our results indicate that laser-evoked EEG responses are not determined by the perception of pain per se, but are mainly determined by the saliency of the eliciting nociceptive stimulus (i.e., its ability to capture attention). Therefore laser-evoked EEG responses represent an indirect readout of the function of the nociceptive system.

Preoperative Psychologic and Demographic Predictors of Pain Perception and Tramadol Consumption Using Intravenous Patient-controlled Analgesia

Postoperative pain is characterized by a wide variability of patients' pain perception and analgesic requirement. The study investigated the extent to which demographic and psychologic variables may influence postoperative pain intensity and tramadol consumption using patient-controlled analgesia (PCA) after cholecystectomy. Eighty patients, aged 18 to 70 years, with an American Society of Anesthesiologists physical status I or II and a body mass index between 18.5 and 24.9, undergoing laparoscopic cholecystectomy were enrolled. Self-rating anxiety scale (SAS) and self-rating questionnaire for depression (SRQ-D) were used--1 day before surgery--to assess patients' psychologic status. General anesthesia was standardized. PCA pump with intravenous tramadol was used for a 24-hour postoperative analgesia. Visual analog scale at rest (VASr) and after coughing (VASi) and tramadol consumption were registered. Pearson's and point biserial correlations, analysis of variance, and step-wise regression were used for statistical analysis. Pearson r showed positive correlations between anxiety, depression, and pain indicators (P<0.05). Moreover, female patients had higher pain indicators (P<0.05). Analysis of variance showed that anxious (P<0.05) and depressed (P<0.001) patients had higher pain indicators, which significantly decreased during the postoperative 24 hours (P<0.00001). Regression analysis revealed that tramadol consumption was predicted by preoperative depression (P<0.001). VASr was predicted by sex and SRQ-D (P<0.05). VASi was predicted by sex and SAS (P<0.05). Pain perception intensity was primarily predicted by sex with an additional role of depression and anxiety in determining VASr and VASi, respectively. Patients with high depression levels required a larger amount of tramadol.

Effects of NGF-induced muscle sensitization on proprioception and nociception

Temporomandibular disorders (TMDs) are associated with perturbation of proprioceptive and nociceptive function. Recent studies have shown that injection of the neurotrophic protein nerve growth factor (NGF) into the masseter muscle causes sensitization to mechanical pressure stimuli; however, it is not clear if vibration sense and jaw stretch reflexes as measures of proprioceptive function as well as glutamate-evoked pain are also altered. We tested the hypothesis that NGF-induced mechanical sensitization would be associated with changes in vibration sense and stretch reflex sensitivity as well as facilitation of glutamate-evoked pain responses. A double-blind, randomized and placebo-controlled study was conducted on 14 healthy men. In one session subjects received an injection of NGF (5 microg in 0.2 ml) into the masseter muscle and in a control session an injection of buffered isotonic saline (0.9%, 0.2 ml). Subjects assessed their pain intensity on a 0-10 cm visual analogue scale (VAS) for 15 min after the injections. Pressure pain thresholds (PPT), vibration sense and jaw stretch reflexes were recorded at baseline and 1, 2, 3 and 24 h post-injection. The sensitivity to injections of glutamate into the masseter muscle (1 M, 0.2 ml) was assessed after 24 h. ANOVAs were used to assess significant differences. NGF did not cause more pain than isotonic saline, but significantly reduced PPTs 1, 2, 3 and 24 h post-injection (P < 0.001) whereas isotonic saline had no effects on PPTs (P = 0.583). The injection of glutamate after 24 h was associated with reduced PPTs in both sessions, but the PPTs remained lower in the NGF pretreated masseter than in the control masseter (P < 0.001). Ratings of vibratory stimuli and the normalized amplitude of the jaw stretch reflex were not affected by the NGF-induced sensitization; however, after glutamate injection a significant increase in the stretch reflex was observed in the injected masseter muscle in both sessions (P = 0.002). There were no significant differences in the perceived pain intensity of the glutamate injection between the masseter muscle pretreated with NGF or control (P > 0.414), although the glutamate-evoked pain drawing areas were larger for the NGF-pretreated masseter muscle (P = 0.009). In conclusion, this study confirms that masseter muscle injection of NGF is associated with a distinct and prolonged sensitization to mechanical stimuli, but without an effect on large-diameter mechanoreceptive and the muscle spindle afferents. Additional challenge of the NGF pretreated muscle with glutamate did not indicate a conspicuous sensitization to noxious chemical stimuli. These findings are discussed in terms of the concept of "proprioceptive allodynia".

Anger management style and emotional reactivity to noxious stimuli among chronic pain patients and healthy controls: The role of endogenous opioids.

Previous work suggests that elevated trait anger-out exacerbates pain responses in part through endogenous opioid dysfunction. The authors examined whether this opioid dysfunction affects not only perceived pain intensity, but also emotional responses to being hurt. 79 chronic low back pain (LBP) patients and 46 healthy controls received opioid blockade (8 mg naloxone i.v.) and placebo in randomized, counterbalanced order in separate sessions. During each session, participants sequentially experienced finger pressure pain and ischemic forearm pain tasks, with emotional state assessed at baseline and postpain. Blockade effects indexing opioid modulation of emotional reactivity were derived by subtracting placebo from blockade condition emotional reactivity. Significant Participant Type x Anger-Out interactions on blockade effects indicated that in LBP participants but not in controls, greater anger-out was associated with deficient opioid modulation of anxiety, anger, and fear reactivity to noxious stimulation. Across participant types, greater anger-in was associated with impaired opioid modulation of anxiety and fear reactivity. Anger-in opioid effects were partially due to overlap with general negative affect. Opioid dysfunction associated with trait anger-out may affect not only perceived pain intensity, but also pain-related suffering in individuals with chronic pain conditions. Implications for understanding the health effects of anger management styles are discussed.

Effectiveness of acupressure to reduce pain in intramuscular injections

Summary Background Acupressure is a massage technique which can induce relaxation. The effectiveness of acupressure to reduce pain in intramuscular injection was studied in this research. Methods It was a crossover single blind experimental design. The patients who were prescribed penicillin for at least two daily doses were included in the study. Each subject received an injection with acupressure applied to one buttock and an injection without acupressure to the other buttock or vice versa. The two conditions were randomly allocated. The perception of pain was measured on a visual analogue scale. Results Sixty-four patients were recruited into the study. Thirty-two (50%) were female. The mean age was 28 ± 9.9 years old. Fifty patients were injected with penicillin 6.3.3 (78%) and 14 patients received penicillin G plus procaine (22%). The mean score for perceived pain intensity for the acupressure injection was 3 ± 2 and the mean score for the injection without acupressure was 5 ± 2. The result showed that the perceived pain intensity was at average 2.5 lower in the acupressure group comparing to ordinary injection (P Conclusions According to findings the acupressure can reduce the pain of intramuscular injection.

Social Connectedness and Patient Recovery after Major Operations

Social connectedness is thought to play an important role in overall health and well being. We hypothesized that social network size and other measures of social connectedness would predict perceived pain intensity, unpleasantness, and anxiety in veterans recovering after major thoracic or abdominal operations and influence postoperative complications and length of stay. Six hundred five patients from two Veterans Affairs' medical centers who participated in a randomized controlled trial of massage as adjuvant treatment for postoperative pain were the subjects of this study. Subjects' social networks were assessed by the numbers of friends or relatives an individual had and how frequently contact was made with members of their social network. Subjective outcomes were rated with visual analogue scales for 5 postoperative days. Daily opiate use, postoperative complications, and length of stay were also recorded. Mean (+/-SD) age was 63.8 years (+/-10.2 years) and 98.5% of participants were men. Those reporting a greater social network were older and had lower preoperative pain intensity, unpleasantness, and state and trait anxiety (p < 0.001). Considerably less pain intensity, unpleasantness, and opiate use were associated with increasing social network size during the first 5 postoperative days. After adjusting for preoperative values of pain and anxiety, these relationships were no longer statistically significant. Smaller social network size was associated with the likelihood of length of stay >or= 7 days (p = 0.03). These findings suggest that the effect of social networks on surgical outcomes can be mediated by their effect on levels of preoperative pain and anxiety. Patients should be screened preoperatively for pain and anxiety because these are strong predictors of a more difficult postoperative recovery.

Effect of needle gauge on perception of pain intensity among infants receiving D.P.T.Vacacination

Effect of needle gauge on perception of pain intensity among infants receiving D.P.T.Vacacination

Effect of needle gauge on perception of pain intensity among infants receving D.P.T vaccination

Effect of needle gauge on perception of pain intensity among infants receving D.P.T vaccination

Assessment of the clinical relevance of quantitative sensory testing with Von Frey monofilaments in patients with allodynia and neuropathic pain. A pilot study

Allodynia is a common and disabling symptom in many patients with neuropathic pain. Whereas quantification of pain mostly depends on subjective pain reports, allodynia can also be measured objectively with quantitative sensory testing. In this pilot study, we investigated the clinical relevance of quantitative sensory testing with Von Frey monofilaments in patients with allodynia as a consequence of a neuropathic pain syndrome, by means of correlating subjective pain scores with pain thresholds obtained with quantitative sensory testing. During a 4-week trial, we administered a cannabis extract to 17 patients with allodynia. We quantified the severity of the allodynia with Von Frey monofilaments before, during and after the patients finished the trial. We also asked the patients to rate their pain on a numeric rating scale at these three moments. We found that most of the effect of the cannabis occurred in the last 2 weeks of the trial. In this phase, we observed that the pain thresholds, as measured with Von Frey monofilaments, were inversely correlated with a decrease of the perceived pain intensity. These preliminary findings indicate clinical relevance of quantitative sensory testing with Von Frey monofilaments in the quantification of allodynia in patients with neuropathic pain, although confirmation of our data is still required in further studies to position this method of quantitative sensory testing as a valuable tool, for example, in the evaluation of therapeutic interventions for neuropathic pain.

Pain sensations to the cold pressor test in normally menstruating women: comparison with men and relation to menstrual phase and serum sex steroid levels

The role of gonadal hormones on pain sensations was investigated in normally menstruating women (n = 16) using the cold pressor test. Tolerance time, pain threshold, and pain intensity were examined once a week during a 4-wk period, and serum concentrations of 17beta-estradiol and progesterone were determined at each test session, which were classified into the early follicular phase, late follicular phase, early luteal phase, and late luteal phase, as determined by the first day of menses and the actual hormone levels recorded. A group of men (n = 10) of the same age interval was examined for comparison. The data show that pain threshold was reduced during the late luteal phase compared with the late follicular phase, and hormone analyses showed significant positive correlation between the progesterone concentration and lowered pain threshold and increasing pain intensity. Hormone analysis also showed an interaction between S-estradiol and S-progesterone on pain intensity, demonstrating that the increased perceived pain intensity that was associated with high progesterone concentrations was significantly reduced with increasing levels of estradiol. While no statistically significant sex differences in pain measurements were found, women displayed much more pronounced, and statistically significant, session-to-session effects than men, with increased pain threshold and decreased pain intensity with each test session. Hence, these data suggest that the changes in the serum concentration of gonadal hormones that occur during the menstrual cycle influence pain sensations elicited by noxious tonic cold stimulation and show that adaptation to the cold pressor test may be sex dependent.

Transient decrease of sensory perception after thermoalgesic stimuli for quantitative sensory testing

Transient decrease in the excitability of a reflex circuit following its activation by appropriate stimuli is a well-recognized phenomenon, but it is unclear how this applies to thermoalgesic stimuli during quantitative sensory testing (QST). We examined the effects induced by a thermoalgesic (conditioning) stimulus on the response to a subsequent (test) stimulus of the same characteristics. All tests were done using a Peltier thermode with a surface area of 12.5 cm(2) using ramp rates of 2 degrees C/s and variable interstimulus intervals (ISIs) ranging from 10 to 60 s. Perception was measured with an electronic visual analog scale. No changes were observed in latency of pain perception. However, latency of warm perception was significantly delayed and pain perception intensity was significantly reduced with respect to conditioning stimuli at ISIs below 60 s. Our results indicate a transient saturation of warm and heat pain perception systems after a thermoalgesic stimulus. We therefore recommend that time intervals of >1 min be used between two consecutive thermoalgesic stimuli when examining QST.

Attentional modulation of visceral and somatic pain

A better understanding of the cortical processes underlying attentional modulation of visceral and somatic pain in health are essential for interpretation of future imaging studies of hypervigilance towards bodily sensations which is considered to be an aetiologically important factor in the heightened pain reported by patients with irritable bowel syndrome and fibromyalgia. Twelve healthy subjects were recruited for this study. Simultaneous trains of electrical pulses (delivered to either the rectum or lower abdomen) and auditory tones lasting 6 s were delivered to the subjects during a whole-brain functional scan acquisition. Subjects were instructed to attend to the auditory tones (distracter task) or electrical pulses (pain task). Pain intensity ratings were significantly lower during the distraction task compared with the pain task (P < 0.01) in both sensory modalities. The left primary somatosensory cortex increased in activity with increasing pain report, during attention to visceral pain. Bilateral anterior insula (aIns) cortex activity increased with increasing somatic pain report independent of the direction of attention. Conversely, the primary and secondary auditory cortices significantly increased in activation with decreased pain report. These results suggest that pain intensity perception during attentional modulation is reflected in the primary somatosensory cortex (visceral pain) and aIns cortex activity (somatic pain).

Changes in self-perceived role identity modulate pain perception

Pain is an experience including physiological and psychological factors. We assume that emotions may be elicited and increased through self-perceived role identity and that change of role identity alters quality and intensity of pain perception. We used role-play strategies to assess whether pain can be better tolerated whenever, in an unavoidable and unpleasant context, role identity confers pain a meaningful and thus suitable character. We induced antithetic roles in 21 actors who received heat stimuli on their arms before and after role-play conditions. Pain tolerance, skin conductance and voice signals were measured. Pain tolerance increased for heroes/heroines and decreased for faint-hearts. Men showed higher pain tolerance. Heroes/heroines evaluated heat stimuli as more intense. Faint-hearts found pain stimuli more affectively loaded at lower temperatures. Women showed higher pain ratings. Hence, self-perception influences pain perception. Role-play strategies may be of value for new pain management strategies.

Determinants of Walking Exercise Among Individuals With Intermittent Claudication

This study examined psychosocial determinants of walking exercise among individuals with intermittent claudication and explored perceived pain intensity as a moderator of the intention-behavior relationship. Ninety-four participants (n = 61 m/33 f, 70.05 +/- 9.02 years) were recruited from a medical facility and completed baseline measures of attitudes (ie, positive or negative evaluation of walking exercise), subjective norms (ie, perceived social pressure regarding walking exercise), perceived behavioral control (ie, ease or difficulty for engaging in walking exercise), and intentions regarding walking exercise in the upcoming 4 weeks. Participants were contacted weekly by telephone for 4 weeks and asked to recall their walking exercise and associated perceived pain intensity for the preceding 7-day period. Outcome measures were participants' baseline intentions to walk and their reported walking exercise for 4 weeks. Attitudes, subjective norms, and perceived behavioral control contributed to a multiple regression model predicting 67% of the variance in walking intentions. Intentions and perceived behavioral control explained 34% of the variance in walking exercise. Perceived pain intensity was not associated with walking exercise and failed to moderate the intention-behavior relationship. Findings support the theory of planned behavior for predicting walking intentions and exercise among individuals with intermittent claudication and suggest that pain cognitions as measured in this study do not play a role in determining walking.

Diurnal time course of pain perception in healthy humans

Rapid skin heating by infrared lasers can be used to investigate the integrity of the nociceptive system by activating A-delta and C fibers. The aim of our study was to analyze if healthy humans exhibit any clinically relevant diurnal variations in their heat pain sensitivity. Circadian A-delta fiber function was analyzed by studying N2 and P2 components of laser-evoked potentials (LEP) and pain thresholds evoked by laser stimulation of the foot every 2 h from 8 a.m. to 10 p.m. in 15 healthy subjects. Heat stimuli were generated by an infrared Tm-YAG laser and were delivered to an area of 4 cm × 4.5 cm on the dorsum of the right or left foot in 3 runs of incremental and decremental intensities. After each stimulus subjects were asked to classify the intensity of pain with a numeric rating scale (NRS). LEPs were recorded with fixed stimulus intensities that were 1.5× of the pain threshold. Data were collected with the SynAmps System (Neuroscan, El Paso, USA) and averaged across 35–40 trials. Laser-induced heat pain thresholds and circadian latencies of LEP did not significantly vary during the day. Our results correspond with previous studies that did not detect any consistent significant diurnal variations in perception of heat pain perception using contact thermodes. The intensity of pain perception did not demonstrate any correlation with mood or sleep parameters as measured with the Beck Depression Inventory (BDI), the subjective sleep scales Pittsburgh Sleep Quality Index (PSQI) and Epworth Sleepiness Scale (ESS).

Mapping the spinal and supraspinal pathways of dynamic mechanical allodynia in the human trigeminal system using cardiac-gated fMRI

Following injury and inflammation, pain to light stroking (dynamic mechanical allodynia) might develop at the damaged site (primary area) or in adjacent normal tissue (secondary area).Using fMRI we mapped changes in the spinal trigeminal nucleus (spV), and supraspinal brainstem nuclei following heat/capsaicin-induced primary and secondary dynamic mechanical allodynia in the human trigeminal system. The role of these structures in dynamic mechanical allodynia has not been clarified yet in humans. During the control session we applied the same mechanical stimuli to the same untreated trigeminal area.Primary and secondary mechanical allodynia showed equal levels of perceived pain intensity, and compared to control mechanical stimulation exhibited similar responses in the ipsilateral spV and contralateral ventrolateral periaqueductal gray (vlPAG). Activity in the spV was significantly higher during both conditions versus the control mechanical stimulation, indicating that central sensitization of second-order neurons is similar for primary and secondary mechanical allodynia. The vlPAG showed decreased activity that inversely correlated with pain ratings during primary allodynia, i.e. the more deactivated the vlPAG the higher the pain intensity (p<0.05, Pearson's correlation).Primary and secondary dynamic mechanical allodynia were also characterized by significant differences involving distinct supraspinal structures mainly involved in pain modulation and including the rostroventromedial medulla, pons reticular formation, dorsolateral PAG, all more active during primary versus secondary allodynia, and the medial reticular formation of the caudal medulla that was more active during secondary versus primary allodynia. These results indicate that the pain modulatory system is involved to a different extent during primary versus secondary mechanical allodynia.