Recruitment and inclusion procedures as "pain killers" in clinical trials?

Background

Recruitment and inclusion procedures in clinical trials are time critical. This holds particularly true for studies investigating patients with fluctuating symptom patterns, like those with chronic neck pain. In a feasibility study on neck pain, we found a clinically relevant decrease in pain ratings within the recruitment period. This paper analyses the phenomenon and gives recommendations for recruitment procedures in clinical trials on pain.

Methods

Changes in pain intensity scores of 44 chronic neck pain patients (6 males and 36 females; mean age: 45.3±13.2 years) between the first telephone contact and baseline assessment were analyzed. Inclusion criterion was a mean pain intensity of ≥40 on a 0-100 numerical rating scale during the last three months. Statistical analyses were performed using ANOVA and parametric/non-parametric correlation coefficients.

Results

Average pain intensity score decreased significantly from 60.3±13.3 at telephone interview to 38.1±21.7 at baseline assessment. This represents a relative change of 36.8%. A weak but significant negative correlation was found between number of days between assessments and pain rating differences. There was a positive correlation between change of pain intensity and the pain level at the first contact, indicating that the decreased pain ratings over time were also dependent on the initial pain rating.

Conclusions

The clinically significant changes in pain intensity were weakly related to waiting time and moderately dependent on initial pain intensity, suggesting regression to the mean. The natural course of the disease and the Hawthorne effect are also discussed as contributing factors.

Pain-relieving effectiveness, quality of life and tolerability of repeated capsaicin 8% patch treatment of peripheral neuropathic pain in Scandinavian clinical practice

Context

Clinical trials have demonstrated the efficacy and safety of the capsaicin 8% patch in patients with peripheral neuropathic pain (PNP); however, few studies have assessed this treatment in a clinical practice.

Objective

To determine whether treatment and re‐treatment with the capsaicin 8% patch reduce PNP intensity in clinical practice.

Methods

Three non‐interventional, observational studies were concurrently conducted in Denmark, Norway and Sweden. Patients with probable or definite PNP received one or two treatments with the capsaicin 8% patch according to usual clinical practice. All analyses were performed on combined data.

Results

Overall, 382 and 181 patients received treatment and re‐treatment, respectively, with the capsaicin 8% patch. At the group level, a significant reduction in mean level of ‘usual pain’ intensity (Numerical Pain Rating Scale) over the last 24 h’ score was observed from baseline to Weeks 2 through 8 [−1.05 (95% confidence interval: −1.27, 0.82); p < 0.001] with 28% and 31% of patients reporting a ≥30% reduction in pain after first treatment and re‐treatment, respectively. Improvements in health‐related quality of life (EQ‐5D‐3L index) and overall health status (Patient Global Impression of Change) were observed early (Week 1) and throughout the treatment periods. Most application site reactions subsided within a week after treatment. Following treatment and re‐treatment, 57% and 71% of patients, respectively, were willing to undergo further treatment with the capsaicin 8% patch.

Conclusion

In Scandinavian clinical practice, capsaicin 8% patch treatment was associated with significant reductions in pain intensity and was well tolerated with over half of patients willing to undergo re‐treatment.

Trait-anxiety and pain intensity predict symptoms related to dysfunctional breathing (DB) in patients with chronic pain

Aims

The purpose of this cross-sectional study was to inves-tigate the occurrence of symptoms related to dysfunctional breathing (DB) in chronic pain patients and to examine factors associated with these symptoms.

Methods

A questionnaire was sent to 527 adults referred to out-patient pain clinics at Oslo university hospital. The questionnaire provided demographic data, Brief Pain Inventory, Spielberger state- trait anxiety inventory, and Nijmegen questionnaire (NQ). Multiple regression analyses were performed using SPSS.

Results

A total of 108 patients (20%) responded to the questionnaire and was included. Mean age was 49 years and two third of the participants were female. More than four out of ten had a NQ score ≥ 23 (a conservative cutoff value for DB). The median NQ score in the sample was 19. Trait-anxiety (Beta = .412, p < 0.001) and maximal pain intensity during the past week (Beta = .264, p = 0.004) predicted symptoms related to DB even when controlling for age and gender.

Conclusions

The study shows that a large portion of patients with chronic pain experiences symptoms that have been associated with hyperventilation and DB and at a higher level than previously reported. Although trait-anxiety is a strong predictor for symptoms related to DB, we find it interesting that maximal pain intensity during the last week also was associated with these symptoms. The cross-sectional design, low response rate, and lack of diagnoses limit our ability to draw conclusions about causal relationship and extrapolate to a larger populations of patients with chronic pain.

Assessment of pain

Valid and reliable assessment of pain is essential for both clinical trials and effective pain management. The nature of pain makes objective measurement impossible. Acute pain can be reliably assessed, both at rest (important for comfort) and during movement (important for function and risk of postoperative complications), with one-dimensional tools such as numeric rating scales or visual analogue scales. Both these are more powerful in detecting changes in pain intensity than a verbal categorical rating scale. In acute pain trials, assessment of baseline pain must ensure sufficient pain intensity for the trial to detect meaningful treatment effects. Chronic pain assessment and its impact on physical, emotional, and social functions require multidimensional qualitative tools and health-related quality of life instruments. Several disease- and patient-specific functional scales are useful, such as the Western Ontario and MacMaster Universities for osteoarthritis, and several neuropathic pain screening tools. The Initiative on

METHODS

Measurement, and Pain Assessment in Clinical Trials recommendations for outcome measurements of chronic pain trials are also useful for routine assessment. Cancer pain assessment is complicated by a number of other bodily and mental symptoms such as fatigue and depression, all affecting quality of life. It is noteworthy that quality of life reported by chronic pain patients can be as much affected as that of terminal cancer patients. Any assessment of pain must take into account other factors, such as cognitive impairment or dementia, and assessment tools validated in the specific patient groups being studied.

Postoperative pain and convalescence in living kidney donors-laparoscopic versus open donor nephrectomy: a randomized study

The aim of the present study was to compare postoperative pain and convalescence in patients randomized to laparoscopic or open donor surgery in a prospective, controlled trial. The donors were randomly assigned to undergo laparoscopic (n = 63) or open (n = 59) donor nephrectomy. Our end points were amount of administered analgesics in the recovery period, postoperative pain on the second postoperative day and at one month after surgery and duration of sick leave. There was a significant difference in favor of the laparoscopic group regarding administered analgesics on day of surgery (p < 0. 02). No difference was observed between groups regarding self-reported pain on the second postoperative day. One month post donation, significantly fewer donors in the laparoscopic group reported pain (p < 0. 02) or had used analgesics (p < 0.05). The duration of sick leave was significantly shorter in the laparoscopic group (p = 0.01). The laparoscopic group experienced a more rapid convalescence and a shorter period of sick leave. Although immediate postoperative pain can be managed efficiently regardless of procedure, a lower consumption of opioids and incidence of pain in the convalescent period suggest a clinically relevant patient-experienced benefit from a successful laparoscopic procedure.

Detection of organ ischemia during hemorrhagic shock

BACKGROUND

In a porcine hemorrhagic shock model we aimed to determine: (a) whether blood flow to the intestine and kidney was more reduced than cardiac output; (b) whether parameters of anaerobic metabolism correlated with regional blood flow; and (c) whether metabolic parameters in intestine, kidney and skeletal muscles detected a compromised metabolic state at an earlier stage than did systemic parameters.

METHODS

In an animal research laboratory at a university hospital six domestic pigs were subjected to volume-controlled hemorrhage. Every 30 min samples of blood were withdrawn. Systemic and regional hemodynamic parameters and tissue levels of PCO2 were monitored. Whole body and organ-specific oxygen consumption (VO2) and veno-arterial (VA) differences of lactate, glucose, potassium (K+), PCO2, H+ and base excess (BE) were calculated every 30 min.

RESULTS

With progressive hemorrhage, intestinal blood flow decreased to the same extent as cardiac output, whereas the reduction in renal blood flow was more pronounced. We found a concomitant reduction in VO2 (onset of supply dependent metabolism) in intestine, kidney and skeletal muscles. In muscular tissue PCO2 increased to levels three times higher than baseline, while renal and intestinal PCO2 increased eightfold. Supply dependency was associated with a concomitant increase in VA CO2 and VA H+. Also, VA lactate increased, mostly in intestine and least in skeletal muscle. Intestinal and renal VA K+ increased, while muscular VA K+ decreased. Arterial lactate and H+ increased considerably, whereas arterial BE decreased.

CONCLUSION

With progressive hemorrhage, renal blood flow, but not intestinal and skeletal muscle blood flow, was reduced more than cardiac output. Supply dependent oxygen metabolism (VO2) and organ acidosis occurred simultaneously in the three organs, despite differences in blood flow reductions. Organ ischemia coincided with a pronounced change in arterial lactate and systemic acid base parameters.

MRI-guided celiac plexus block

Celiac plexus block is used as a palliative procedure in cases of severe upper abdominal pain caused by pancreatitis or tumors of the pancreas. It can be guided by bony landmarks, fluoroscopy, ultrasound (US), or computed tomography (CT). To avoid severe complications, methods visualizing soft tissue, like CT and magnetic resonance (MR) imaging, are preferable. We describe celiac plexus blocks carried out in an open MR scanner, offering needle guidance with an optical tracking system and near real-time image acquisition. Eight patients with severe chronic abdominal pain were included. In these, 14 celiac blocks were carried out. Good or total pain relief was achieved in 8 of the 14 blocks (57%), a moderate effect in 5 blocks (36%), and no effect in 1 block (7%). The placement of the needle was easily guided with MR in all cases. The MR technique ensures good visualization of soft tissue, direct monitoring of needle movement and avoids exposure to ionizing radiation. Celiac plexus block can safely be carried out in an open MR scanner.

Gas supersaturation in the cecal wall of mice due to bacterial CO2 production

PCO2 in the lumen and serosa of cecum and jejunum was measured in mice. The anesthetic used was a fentanyl-fluanisone-midazolam mixture. PCO2 was recorded in vivo and postmortem. PCO2 was 409 +/- 32 Torr (55 +/- 4 kPa) in the cecal lumen and 199 +/- 22 Torr (27 +/- 3 kPa) on the serosa in normal mice. Irrigation of the cecum resulted in serosal and luminal PCO2 levels of 65-75 Torr. Cecal PCO2 was significantly lower in germ-free mice (65 +/- 5 Torr). Cecal PCO2 increased significantly after introduction of normal bacterial flora into germ-free mice. Introduction of bacterial monocultures into germ-free mice had no effect. After the deaths of the mice, cecal PCO2 increased rapidly in normal mice. The intestinal bacteria produced the majority of the cecal PCO2, and the use of tonometry in intestinal segments with a high bacterial activity should be interpreted with caution. We propose that serosal PCO2 levels >150-190 Torr (20-25 kPa) in the cecum of mice with a normal circulation may represent a state of gas supersaturation in the cecal wall.

[CO2 pressure used in the diagnosis of ischemia]

Under ischemic conditions O2 delivery is insufficient, and the cells convert to anaerobic metabolism with production of lactic acid. The protons formed in this process are to a large extent rapidly buffered inside the cell by proteins and HCO3-. Protons buffered by HCO3- form CO2 in the tissue. Since the blood supply during ischemia is minimal, CO2 is not transported away from the tissue and will reach tensions far above pCO2 found under aerobic conditions. Thus, measuring pCO2 can be used to detect ischemia in an organ. Gastrointestinal tonometry is based on the concept of CO2 accumulation during anaerobiosis. It has been customary to calculate so-called interstitial pH (pHi) by incorporating the measured pCO2 in the tonometer and the HCO3- in an arterial blood gas in the Henderson-Hasselbalch equation. However, this method has several weaknesses, and we recommend using the measured pCO2, or rather the difference between gastrointestinal and arterial pCO2. Experimental studies have shown that pCO2 electrodes sensitively detect the onset of ischemia also in solid organs. The accumulation of pCO2 coincides with the shift from supply-independent to supply-dependent oxygen consumption and correlates with other markers of ischemia. pCO2 measurement at organ level is a promising tool in the monitoring of organ ischemia.

PCO2 electrodes at the surface of the kidney detect ischaemia

BACKGROUND

Under ischaemic (anaerobic) conditions there will be an accumulation of CO2 in the tissue secondary to a build up of protons that is buffered by HCO3. We reasoned that CO2 could be measured at the surface of the kidney by PCO2 electrodes to detect ischaemic conditions.

METHODS

Anaesthetized, mechanically ventilated pigs (25-30 kg) were investigated. Two acute porcine models, one of haemorrhagic shock and one of renal artery stenosis were used. Renal blood flow was gradually decreased, either by successive episodes of bleeding through the arterial cannula or by successive snaring of the renal artery.

RESULTS

In both models we found that with decreased blood flow but maintained aerobic metabolism (supply independence) PCO2 both at the surface of the kidney and in the renal vein increased by 2-3 kPa. Thus, the tissue-venous PCO2 difference did not change much. At DO2crit, i.e., at the transition to supply-dependent O2 consumption, the tissue PCO2 started to increase rapidly, as did the tissue-venous PCO2 difference. This is compatible with the notion that a hallmark of ischaemia is decreased ability of the blood to transport away waste products because the contact between large parts of tissue and blood is virtually non-existent. In the renal artery stenosis model kidney surface PCO2 values rose from a baseline of 6.6 +/- 0.6 kPa (mean +/- SEM) to a value near DO2crit of 10.6 +/- 0.8 kPa, reaching a final value of 29.9 +/- 3.5 kPa at no flow. PCO2 in the renal vein, however, reached a maximum of only 8.2 +/- 0.6 kPa. Numbers very similar to these were also found in the haemorrhagic model. The urine production decreased before the onset of ischaemia. When surface PCO2 values increased sharply indicating ischaemia, the urine production was zero. Lactate production by the kidney correlated very well with increasing tissue PCO2 values further corroborating that anaerobic metabolism was detected with the electrodes.

CONCLUSION

We conclude that PCO2 electrodes placed at the surface of the kidney detect renal cortical ischaemia.

The duration of acute respiratory tract infections in children

In a rural district in Western Norway with 400 children under 16 years, we recorded all children with acute respiratory infections who attended their general practitioner during a period of four months. 90 cases were recorded, giving an incidence of 5.6% per month. Half of the patients contacted the doctor within four days from the initial symptom, every sixth waited more than two weeks. Their symptoms were monitored by the parents. Low fever, nasal discharge and cough were the most long-standing symptoms. After three weeks less than 50% of the patients were completely recovered. The children under one year of age recovered more quickly than the rest. No serious complications or sequelae were recorded.