Sylvie Lafrenaye

Preterm births: Can neonatal pain alter the development of endogenous gating systems?

Prematurity is known to affect the development of various neurophysiological systems, including the maturation of pain and cardiac circuits. The purpose of this study was to see if numerous painful interventions, experienced soon after birth, affect counterirritation‐induced analgesia (triggered using the cold pressor test) later in life. A total of 26 children, between the ages of 7 and 11 participated in the study. Children were divided into three groups, according to their birth status (i.e., term‐born, born preterm and exposed to numerous painful interventions, or born preterm and exposed to few painful interventions). Primary outcome measures were heat pain thresholds, heat sensitivity scores, and cardiac reactivity. Results showed that preterm children and term‐born children had comparable pain thresholds. Exposure to conditioning cold stimulation significantly increased heart rate and significantly decreased the thermal pain sensitivity of term‐born children. These physiological reactions were also observed among preterm children who were only exposed to a few painful interventions at birth. Changes in heart rate and pain sensitivity in response to conditioning cold stimulation were not observed in preterm children that had been exposed to numerous painful procedures during the neonatal period. These results suggest that early pain does not lead to enhanced pain sensitivity when premature babies become children, but that their endogenous pain modulatory mechanisms are not as well developed as those of children not exposed to noxious insult at birth. Greater frequency of painful procedures also dampened the rise in heart rate normally observed when experimental pain is experienced.

Respiratory effects on experimental heat pain and cardiac activity.

OBJECTIVE Slow deep breathing has been proposed as an effective method to decrease pain. However, experimental studies conducted to validate this claim have not been carried out. DESIGN We measured thermal pain threshold and tolerance scores from 20 healthy adults during five different conditions, namely, during natural breathing (baseline), slow deep breathing (6 breaths/minute), rapid breathing (16 breaths/minute), distraction (video game), and heart rate (HR) biofeedback. We measured respiration (rate and depth) and HR variability from the electrocardiogram (ECG) output and analyzed the effects of respiration on pain and HR variability using time and frequency domain measures of the ECG. RESULTS Compared with baseline, thermal pain threshold was significantly higher during slow deep breathing (P = 0.002), HR biofeedback (P < 0.001), and distraction (P = 0.006), whereas thermal pain tolerance was significantly higher during slow deep breathing (P = 0.003) and HR biofeedback (P < 0.001). Compared with baseline, only slow deep breathing and HR biofeedback conditions had an effect on cardiac activity. These conditions increased the amplitude of vagal cardiac markers (peak-to-valley, P < 0.001) as well as low frequency power (P < 0.001). CONCLUSION Slow deep breathing and HR biofeedback had analgesic effects and increased vagal cardiac activity. Distraction also produced analgesia; however, these effects were not accompanied by concomitant changes in cardiac activity. This suggests that the neurobiology underlying respiratory-induced analgesia and distraction are different. Clinical implications are discussed, as are the possible cardiorespiratory processes responsible for mediating breathing-induced analgesia.

Comparing pain modulation and autonomic responses in fibromyalgia and irritable bowel syndrome patients.

Objectives:Past studies confirm that patients with fibromyalgia (FM) and irritable bowel syndrome (IBS) show similar pain processing dysfunctions, such as reduced pain inhibition and aberrant autonomic nervous system (ANS) responses. However, patients with FM and IBS have rarely been investigated in the same study. The aim of the present study, therefore, was to compare descending pain inhibition, pain sensitivity, and ANS reactivity to pain in FM, IBS, and healthy controls (HC). Methods:Female patients with FM (n=10), IBS (n=13), and HCs (n=10) were exposed to multiple cold water (12°C) immersions to study pain sensitivity and descending pain inhibition. Heart rate variability was also assessed during immersions. Results:Pain intensity scores were highest in FM, intermediate in IBS, and smallest in HCs. In contrast, pain inhibition was absent in FM, intermediate in IBS, and strongest in HCs. Importantly, controlling for differences in pain inhibition abolished group differences in pain sensitivity. Heart rate variability analyses confirmed that, in response to mild levels of pain, patients with FM showed greater sympathetic activity whereas HCs showed greater parasympathetic activity. Patients with IBS showed intermediate ANS responses. Discussion:Our results confirm the presence of graded levels of somatic hyperalgesia across patients with IBS and FM. A similar pattern of result was observed for pain inhibitory dysfunctions. These pain processing changes were accompanied by abnormal autonomic responses, which maintained patients (principally patients with FM) in a state of sympathetic hyperactivity. Results suggest that patients with IBS and FM may present common, but graded, pain processing and autonomic dysfunctions.

The role of cardiovascular activity in fibromyalgia and conditioned pain modulation.

Summary Reduced blood pressure responses to pain during a conditioning stimulus could be involved in diminished conditioned pain modulation effectiveness in fibromyalgia. ABSTRACT Fibromyalgia (FM) is a chronic widespread pain condition of unknown origin. Reduced endogenous pain inhibition could be related to high pain sensitivity in FM. Associations between conditioned pain modulation (CPM) and cardiovascular responses to pain have been observed in healthy subjects (HS). Because reduced cardiovascular reactivity to various stressors has been reported in FM patients, we investigated relationships between CPM and cardiovascular response to the cold pressor test (CPT) in 22 FM patients and 25 HS. CPM was evaluated by comparing pain intensity produced by a 120‐second heat test stimulus (HTS) before and after a CPT (2 minutes, 12°C). The CPT, used to activate CPM, produced greater pain intensity in FM patients. Patients with FM had higher heart rates than HS at baseline and during CPT. Higher heart rate was related with higher pain intensity during the CPT. Blood pressure increments during CPT were weaker in the FM group. CPM was less effective in FM patients than in HS. Importantly, systolic blood pressure responses during CPT were positively related to CPM effectiveness, suggesting that reduced blood pressure response during the conditioning stimulus could be involved in CPM dysfunction in the FM group. Higher heart rate could be implicated in the greater sensitivity to cold pain in FM. Patients with FM have reduced blood pressure response to a painful CPT. Reduced cardiovascular reactivity to pain could have important involvement in diminished endogenous pain inhibition efficacy and FM pathophysiology.

Cardiovascular influences on conditioned pain modulation.

&NA; A relationship between the increase in blood pressure induced by the cold‐pressor test and conditioned pain modulation was found in healthy subjects. &NA; Conditioned pain modulation (CPM) (ie, diffuse noxious inhibitory controls) is characterized by reduced perception of pain caused by intense pain in a remote body area. The conditioning stimuli used to trigger CPM causes pain, but also important cardiovascular responses. Higher blood pressure has been associated with reduced pain sensitivity. Descending pain inhibitory mechanisms such as CPM could be involved in this relationship. We investigated the associations between CPM and cardiovascular responses during the cold‐pressor test (CPT). Heat pain threshold and tolerance were evaluated in 26 (13 men, 13 women) healthy subjects. CPM was evaluated by comparing pain intensity produced by a 120‐second heat stimulation before and after a CPT (5 minutes, 7°C). Heart rate, blood pressure, and baroreflex sensitivity were monitored at rest and during CPT to evaluate cardiovascular responses. We observed a positive relationship between resting blood pressure and heat pain tolerance. The CPT caused important heart rate and blood pressure increases. CPT also reduced pain intensity during the subsequent heat pain‐stimulus, indicating effective CPM. A significant positive association was observed between CPM magnitude and the increase in blood pressure during the CPT. These results show that resting blood pressure values are related to acute pain tolerance, while descending pain inhibition is associated with increases in blood pressure. The rise in blood pressure caused by the conditioning stimulus is an important factor predicting the extent of endogenous pain inhibition in healthy subjects.

Randomized placebo-controlled cross-over designs in clinical trials: a gold standard to be reassessed

Abstract Placebo effects are well-known phenomena in medicine and biology. In fact, placebos are used as control conditions in randomized cross-over clinical trials to validate new treatments. Only recently, however, has it become apparent that the conditioning and/or expectation effects provided by the experience of placebos can influence the results of clinical trials. It seems that combining shams and sequences has prejudiced the conclusions provided by cross-over designs. Frighteningly, this bias is always in the same direction, namely to increase the risk of rejecting potentially valid treatments. New models for clinical trials should be encouraged if we wish to market new and truly valid treatments.

Long-Term Persistency of Abnormal Heart Rate Variability following Long NICU Stay and Surgery at Birth.

Preterm birth is associated with painful procedures during the neonatal intensive care unit (NICU) stay. Full-term newborns can also experience pain, following surgery. These procedures can have long-lasting consequences. It has been shown that children born preterm show pain responses and cardiac alterations. This study aimed to explore the heart rate reactivity to pain in 107 subjects born either preterm or full-term who were between 7 and 25 years old at testing. We also evaluated the effect of pain experienced at birth, as represented by a longer NICU stay, time under ventilation, and surgery at birth. Participants were asked to immerse their right forearm in 10°C water for 2 minutes. Electrocardiograms were recorded at baseline and during the immersion procedure. Full-term subjects showed a stable increase in heart rate throughout the procedure, whereas preterm ones showed a strong increase at the beginning, which decreased over time. Also, preterm and full-term subjects who experienced pain at birth showed higher resting heart rate, stronger sympathetic activity, and lower cardiac vagal activity. Our study demonstrated a long-term impact of a long NICU stay and surgery at birth on cardiac autonomic activity. This could lead to impaired reactions to pain or stress in later life.

Procedural Pediatric Sedation by Nurses: Available, Competent, and Safe

Sedation and/or analgesia are standard of care for pediatric patients during painful intervention or medical imaging requiring immobility. Physician availability is frequently insufficient to allow for all procedural sedation. A nurse-led sedation program was created at the Centre Hospitalier Universitaire de Sherbrooke (CHUS) to address this problem. Objective. To evaluate the effectiveness and the safety of our program. Methods. A retrospective study of all the procedural sedations done over one year was performed. Complications were separated in four categories: (1) major complications (call for help; unexpected admission, aspiration, and code); (2) reportable sedation events (oxygen saturation <90%, bradycardia (more than 2 SD below normal for the age of the child), and hypotension (more than 2 SD below normal for the age of the child); (3) difficult sedation (agitation, inadequate sedation, and failure to perform the procedure), (4) minor complications. Results. 448 patients, 249 boys and 199 girls; received sedation for 555 procedures. Overall, 78% (432) of interventions were successfully accomplished: 0% of major complications, 8% of reportable sedation events; 5% of difficult sedation; 9% of minor complications. Conclusion. Our nurse-led sedation program compares favorably to other similar systems.

Assessing Patient-Centred Care for Chronic Pain: Validation of a New Research Paradigm

The use of patient-centred care appears to be a promising avenue for chronic pain management. The aim of this study was to validate an observation scale for the assessment of patient-centred care in nurses and physicians using standardized videos of real patients with chronic pain.

Reduced endogenous pain inhibition in adolescent girls with chronic pain

Abstract Background and aims Chronic pain is affecting a growing number of individuals including adolescents. Different endogenous pain inhibitory systems could confer protection against development of chronic pain. Decreased pain perception can be observed following intense pain (i.e. conditioned pain modulation – CPM) or after physical exercise (i.e. exercise-induced analgesia – EIA). Reduced effectiveness of pain inhibitory mechanisms have been reported in several chronic pain conditions. However, the extent of these dysfunctions has not been thoroughly investigated in adolescents suffering from chronic pain. Our hypothesis was that adolescents suffering from chronic pain have less effective CPM and EIA than pain-free teenagers. Methods Twenty-five healthy adolescent girls and 16 teenage girls with chronic pain participated in this study. Only girls were included in this investigation, since chronic pain is more prevalent in females. The effectiveness of CPM was assessed by comparing heat pain stimulations (individually adapted to induce mild pain intensity) performed with a thermode before and after a cold pressor test (CPT; 2 min, 10 °C). EIA was evaluated by comparing pain intensity produced by an ice cube placed on the forearm before and after a graded exercise test on a cycle ergometer. Results Pain intensity produced by heat pain stimulations decreased following CPT in healthy (p<0.05), but not in chronic pain adolescent girls (p=0.4). Pain intensity induced by the ice cube was reduced after exercise in healthy (p<0.05), but not in chronic pain adolescents (p=0.9). The effectiveness of CPM and EIA was inferior in teenage girls suffering from chronic pain compared to healthy participants (p<0.05). Conclusions Endogenous pain inhibitory mechanisms triggered by intense pain or by physical exercise are effective in healthy adolescent girls. Teenage girls living with chronic pain do not show diminished pain perception after a CPT or a graded exercise test. These results suggest that pain inhibitory mechanisms such as CPM and EIA are ineffective in adolescent girls suffering from chronic pain. Implications In a wider context, the findings of the present research could help understand better the mechanisms involved in the development of chronic pain. Improved comprehension of this subject might help prevent chronic pain conditions and thus, reduce the negative impacts of this burden.