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Biomedical subjects

Asbjørn Mohr Drewes

Publications and source records attributed to Asbjørn Mohr Drewes.

At least 19 recordsLinked to original sources
PubMed2006

Ultrasound-determined geometric and biomechanical properties of the human duodenum.

Methods based on cross-sectional ultrasound imaging may be valuable for assessment of biomechanical parameters in the duodenum in health and disease. In 12 healthy volunteers a specially designed duodenal bag containing a high-frequency ultrasound probe was inflated until the perception of moderate pain. The ultrasound images and bag pressures were recorded before and after administration of butylscopolamine. The duodenum approached a circular shape as the load was increased (P = 0.01). The tension-strain relations were exponential and the curve fitting constant alpha (stiffness) was 1.72+/-0.81 before and 1.13+/-0.22 after administration of butylscopolamine (P=0.5). In three subjects construction of stress-strain diagrams was possible. The wall thickness decreased after administration of butylscopolamine (P < 0.001). The wall thickness was nonhomogeneously distributed along the duodenal circumference, being thickest at high curvatures. In the future this may be useful for assessing the geometry, stiffness, remodeling, and mechanosensory properties in the duodenum and small intestine in health and disease.

Adult↗
PubMed2006

[The physiology of pain].

This article reviews the basic anatomy and physiology of the normal pain system. During recent years, our knowledge of the pain system has been expanded, with increasing insight into the peripheral and central mechanisms underlying both acute and chronic pain. Several differences in the pain system exist for superficial and deep pain. Descending control mechanisms seem to be important in controlling pain, and neuroplastic changes with central reorganisation are frequently seen in patients suffering from pain. This new knowledge will help in understanding and treating patients with chronic pain syndromes.

Acute Disease↗
PubMed2006

[Abdominal pain].

Abdominal and pelvic pain are the most common causes of referral to a gastroenterologist or gynaecologist, and the understanding of visceral pain mechanisms may contribute to a better diagnosis and treatment. Visceral pain is often perceived as a deep, dull and vague sensation with referral to somatic and other visceral structures, but when the peritoneum is involved the pain is more distinct and localised. Long duration or recurrence of the pain may produce permanent changes in the central nervous system, resulting in an increased sensitivity to external stimuli. These changes often involve other organs and somatic structures in the referred pain area. Finally, options for treating visceral pain are described.

Abdominal Pain↗
PubMed2006

Experimental human pain models in gastro-esophageal reflux disease and unexplained chest pain.

Methods related to experimental human pain research aim at activating different nociceptors, evoke pain from different organs and activate specific pathways and mechanisms. The different possibilities for using mechanical, electrical, thermal and chemical methods in visceral pain research are discussed with emphasis of combinations (e.g., the multimodal approach). The methods have been used widely in assessment of pain mechanisms in the esophagus and have contributed to our understanding of the symptoms reported in these patients. Hence abnormal activation and plastic changes of central pain pathways seem to play a major role in the symptoms in some patients with gastro-esophageal reflux disease and in patients with functional chest pain of esophageal origin. These findings may lead to an alternative approach for treatment in patients that does not respond to conventional medical or surgical therapy.

Central Nervous System↗
PubMed2006

Evaluation of the biliary tract in patients with functional biliary symptoms.

The aim of this paper was to describe functional biliary syndromes and methods for evaluation of the biliary tract in these patients. Functional biliary symptoms can be defined as biliary symptoms without demonstrable organic substrate. Two main syndromes exist: Gallbladder dysfunction and sphincter of Oddi dysfunction. The most important investigative tools are cholescintigraphy and endoscopic sphincter of Oddi manometry. In gallbladder dysfunction a scintigraphic gallbladder ejection fraction below 35% can select patients who will benefit from cholecystectomy. Endoscopic sphincter of Oddi manometry is considered the gold standard in sphincter of Oddi dysfunction but recent development in scintigraphic methods is about to change this. Thus, calculation of hilum-to-duodenum transit time and duodenal appearance time on cholescintigraphy have proven useful in these patients. In conclusion, ambient methods can diagnose functional biliary syndromes. However, there are still a number of issues where further knowledge is needed. Probably the next step forward will be in the area of sensory testing and impedance planimetric methods.

Biliary Dyskinesia↗
PubMed2006

Upper gastrointestinal sensory-motor dysfunction in diabetes mellitus.

Gastrointestinal (GI) sensory-motor abnormalities are common in patients with diabetes mellitus and may involve any part of the GI tract. Abnormalities are frequently sub-clinical, and fortunately only rarely do severe and life-threatening problems occur. The pathogenesis of abnormal upper GI sensory-motor function in diabetes is incompletely understood and is most likely multi-factorial of origin. Diabetic autonomic neuropathy as well as acute suboptimal control of diabetes has been shown to impair GI motor and sensory function. Morphological and biomechanical remodeling of the GI wall develops during the duration of diabetes, and may contribute to motor and sensory dysfunction. In this review sensory and motility disorders of the upper GI tract in diabetes is discussed; and the morphological changes and biomechanical remodeling related to the sensory-motor dysfunction is also addressed.

Autonomic Nervous System↗
PubMed2006

The "human visceral homunculus" to pain evoked in the oesophagus, stomach, duodenum and sigmoid colon.

The oesophagus, stomach, duodenum and sigmoid colon were electrically stimulated in 12 healthy volunteers with a thin nasal endoscope. The painful cortical evoked potentials (EPs) were recorded from 64 surface electrodes. The early EPs with latencies < 200 ms were studied and the corresponding dipole sources were calculated. The electrical current intensities needed to evoke pain were highest in the stomach and duodenum, compared to the other segments (F = 7.8; P < 0.001; post hoc analysis P < 0.05). The EP latencies after stimulation of the stomach and sigmoid colon were shorter compared with those to stimulation of the oesophagus and duodenum (all P values < 0.001). The EP amplitudes were higher to oesophagus stimulation (all P values < 0.001 except for the early positivity). The potential fields obtained after stimulation of the most distal segments (duodenum and sigmoid colon) were in general distributed more posteriorly compared to those recorded in the more proximal regions. The EP topographies to stimulation of all gut tracts were explained by a bilateral source in the second somatosensory (SII) area, by a dipole in the anterior cingulate cortex (ACC), and by a bilateral generator in the insular cortex. However, the position of the sources significantly changed depending on the stimulated gut tract. Moreover, while the SII and ACC sources were initially activated to oesophagus and stomach stimulation, the ACC and insular activities were the earliest ones after stimulation of the lower gut segments. The findings reflect differences in pathways and brain processing of visceral nociceptive inputs coming from either upper or lower gut and may improve our understanding of the brain-gut axis in health and disease.

Adult↗
PubMed2006

A comparative study of oxycodone and morphine in a multi-modal, tissue-differentiated experimental pain model.

Visceral pain can be difficult to treat with classical mu-opioid agonists and it has been suggested to use opioids with distinct pharmacological profiles. In animal experiments, oxycodone has shown different effects compared to morphine, and clinical observations have shown that oxycodone may occasionally be superior to, e.g., morphine in the treatment of visceral pain. In the current study, we randomised 24 healthy subjects to treatment with either morphine (30 mg), oxycodone (15 mg) or placebo in a crossover study. The experimental pain model involved multi-modal (mechanical, thermal and electrical) pain tests in the skin, muscles and viscera. The pain tests were carried out at baseline and 30, 60 and 90 min after oral administration of the drugs. The model showed effect of the two opioids compared to placebo on all stimulus modalities in all three types of tissues (all P values <0.001). Both opioids attenuated the sensory response mainly to painful stimulations. Morphine and oxycodone were equipotent in pain modulation of the skin and muscles, but oxycodone had superior analgesic effect to both morphine and placebo on the mechanical (P<0.001) and thermal (P<0.001) stimulations of the oesophagus. In conclusion, the multi-modal and tissue-differentiated pain model could link findings from animal experiments to clinical findings. A different pharmacological profile of oxycodone compared to that of morphine was shown, and thus oxycodone may be a useful alternative to morphine in the treatment of visceral pain syndromes.

Adult↗
PubMed2006

Central sensitization in patients with non-cardiac chest pain: a clinical experimental study.

OBJECTIVE: Patients with non-cardiac chest pain (NNCP) suffer from unexplained and often intractable pain which can pose a major clinical problem. The aim of this study was to investigate nociceptive processing in NNCP patients and their response to experimentally acid-induced oesophageal hyperalgesia using a multimodal stimulation protocol. MATERIAL AND METHODS: Ten highly selected patients with NCCP (mean age 43 years, 1 M) were compared with an age- and gender-matched group of 20 healthy subjects. After preconditioning, the distal oesophagus was painfully distended with a balloon using "impedance planimetry". This method assesses the luminal cross-sectional area of the oesophagus based on the electrical impedance of the fluid inside the balloon. The baseline distensions were done before and after pharmacological relaxation of the smooth muscle with 20 mg butylscopolamine. After baseline distensions, a series of up to 10 mechanical stimuli was performed (temporal summation). The stimulations were repeated after sensitization of the oesophagus induced by acid perfusion. The sensory intensities were assessed during the stimulations and the referred pain area was mapped. RESULTS: At baseline distensions, no differences were seen between patients and controls before and after relaxation of the smooth muscles. The patients tolerated fewer repeated distensions than controls (4.8+/-0.5 versus 9.1+/-0.9; p=0.04) and had an increased size of the referred pain areas to the mechanical stimulations (32.9+/-6.2 versus 64.9+/-18.3 cm2; p=0.01). After sensitization with acid, the patients developed hyperalgesia (p<0.001), whereas no significant changes were seen in controls. CONCLUSIONS: NCCP patients showed facilitated central pain mechanisms (temporal summation and visceral hyperalgesia after sensitization). This could be used in the diagnosis and understanding of the symptoms in these patients.

Acids↗
PubMed2006

Somatosensory changes in the referred pain area before and after cholecystectomy in patients with uncomplicated gallstone disease.

OBJECTIVE: It is estimated that 25-40% of patients have continuing symptoms after cholecystectomy and that 5-10% have pain. The pain may be related to central neuroplastic changes of sensory pathways induced by the gallstone disease. Such neuronal hyperexcitability can be reflected in the somatic referred pain area sharing central pathways with the gallbladder. The aim of this study was to examine somatosensory changes in the referred pain area evoked by painful gallstone attacks before and after cholecystectomy in patients with uncomplicated gallstone disease. MATERIAL AND METHODS: Thirty-seven patients with uncomplicated gallstone disease were included in the study. The sensations and pain thresholds to pinprick, pinching, pressure, thermal and electrical stimulation were studied before and 4-12 weeks after surgery in the area where the pain was referred to during the previous gallstone attacks. An area on the contralateral side of the abdomen served as the control. RESULTS: Somatosensory hyperalgesia in the referred pain area was observed in 84% of the patients before surgery. After elective cholecystectomy, none of the patients had pain complaints, and the sensibility in the referred area was normalized. CONCLUSIONS: Uncomplicated gallstone disease leads to significant hyperalgesia in the somatic referred pain area. At the time of the postoperative investigation none of the patients suffered from pain, which was reflected in the normal sensory findings in the previous referred pain area.

Adult↗
PubMed2006

Pain and mechanical properties of the rectum in patients with active ulcerative colitis.

BACKGROUND: The pain, urgency, and incontinence in ulcerative colitis may be related to changes in viscoelastic properties of the gut wall or to alterations of the sensory pathways. In the present study, we used an advanced rectal probe to study the mechanosensory and smooth muscle properties in patients with active disease. METHODS: Nine patients with ulcerative colitis (mean age 39.5 years) with exacerbation limited to the rectum and sigmoid colon and 17 age-matched healthy subjects were included. The rectum was distended before and after pharmacological relaxation of the smooth muscle until moderate pain was reported, and the cross-sectional area, volume, pressure, tension, and strain were computed. To investigate central integration of a tonic stimulus, the bag was finally distended to the pain threshold; then, the cross-sectional area was held constant for 2 min. RESULTS: The patients were hypersensitive to mechanical stimuli as assessed by the cross-sectional area (F = 21.7; P < 0.001). There were no differences in compliance or stiffness between the 2 groups, but the hypersensitivity was abolished after muscle relaxation. Together with the muscle analysis, this finding demonstrated that the smooth muscles were tonically contracted in the inflamed rectum, resulting in a decreased rectal circumference. The tonic distensions did not evoke central integration of the pain response, indicating that hyperalgesia is more likely related to peripheral factors. CONCLUSIONS: Patients with active ulcerative colitis have hypersensitivity and increased tone of the smooth muscles, which may explain the symptoms. Drugs that affect smooth muscle contraction may be helpful in difficult cases.

Adult↗
PubMed2006

Multi-modal and tissue-differentiated experimental pain assessment: reproducibility of a new concept for assessment of analgesics.

Experimental pain models for assessment of analgesic effect needs to be reproducible, valid and responding in a uniform way to changes in pain level. The pain system differs in various tissue types and analgesics may have different effects in different tissues. This study assessed the reproducibility of an experimental model using mechanical, thermal and electrical stimulations. Pain was evoked in three tissues: Skin, muscle and viscera. Pain was evoked and assessed in 24 healthy volunteers. The experiment was repeated three times with 30 min. intervals and twice with a weekly interval. Systematic bias, intra-class correlation (ICC) and coefficient of variation (CV) and valid sample sizes for analgesic testing were assessed. The model proved to be feasible. Most tests were unbiased, showing stable means except for the mechanical and thermal stimulation in viscera, which showed decreasing pain thresholds when the tests were repeated with 30 min. intervals. Generally the pain tests showed relatively high CV (mean 71%, range 8-145%). The pain tests showed high ICC's (>0.80) when repeated on the same day. When the tests were repeated with an interval of one week, ICC was smaller (mean 0.79 range 0.49-0.96). This means that these tests are useful for analgesic testing recruiting useful sample sizes in a crossover (mean 31 range 2-84) and a parallel study (mean 59 range 3-164) design. Application of this experimental pain model in a cross-over study design with appropriate base-line recordings offers a unique opportunity of revealing analgesic effects on pain arising from different tissues.

Adult↗
PubMed2005

An experimental study of viscero-visceral hyperalgesia using an ultrasound-based multimodal sensory testing approach.

Widespread visceral hypersensitivity and the overlap of symptom complexes observed in functional gastrointestinal disorders may be related to central sensitization and neuroplastic changes. A multimodal and multi-segmental model was developed to evaluate viscero-visceral hyperalgesia induced by experimental esophageal sensitization in healthy volunteers. Twelve healthy subjects were studied using a double-blinded, placebo-controlled design. The sensitivity to mechanical and heat stimulations was assessed in the proximal esophagus, duodenum and rectum before and after perfusion of the distal esophagus with acid or saline. A special-designed probe was used allowing cross-sectional ultrasound imaging during mechanical and heat stimulation of the esophagus and duodenum. Another probe was used for mechanical stimulation of the rectum. The referred somatic pain areas to gut pain stimulations were also assessed. Following acid perfusion 11 of 12 volunteers showed increased sensitivity to one or more stimulation modalities. An overall increased sensitivity to mechanical stretch in the three gut segments was seen (P=0.0001). Posthoc analysis showed that this was mainly due to increased sensitivity in the rectum (P<0.001). No changes were seen to thermal stimulations (all P-values>0.4). The somatic referred pain area to duodenal stimulations increased (P=0.04), while it was unaffected to esophageal and rectal stimulations (P>0.3). The present method demonstrated a new approach to assess multimodal sensitivity to experimental sensitization of the esophagus and related viscero-visceral hyperalgesia. Central mechanisms can explain the remote hyperalgesia to mechanical visceral stimulation and the increase in referred pain areas. The present method may be used to explore pathophysiology and pharmacological interventions in patients with visceral hypersensitivity.

Abdominal Pain↗
PubMed2005

[What is gallstone pain?].

This paper reviews our current understanding of the clinical symptoms and pain mechanisms in patients with gallstone disease. Although most patients have classical pain attacks, the pain localisation can be atypical due to convergence phenomena between somatic and visceral afferents. Furthermore, central neuroplastic changes induced by the recurrent pain attacks are probably of major importance for our understanding of the clinical symptoms. Finally, recommendations for pharmacological treatment of the pain are provided.

Abdominal Pain↗
PubMed2005

Gender differences in pain and biomechanical responses after acid sensitization of the human esophagus.

Our aims were to investigate gender differences to multimodal stimulations of the esophagus after experimentally induced sensitization. Thirty healthy age-matched subjects, 13 males and 17 females, were included. Pain evoked by mechanical and thermal stimuli was assessed before and after perfusion of the lower esophagus with 0.1 N hydrochloric acid. Males were more sensitive to the baseline mechanical stimuli (P < 0.01) and tolerated a lower volume of acid (P = 0.04). After acid perfusion, males were more sensitive than females to distensions (cross-sectional area P = 0.001 and volume P = 0.001). Acid perfusion sensitized both males (P = 0.03) and females (P = 0.04) to heat stimulation but not to cold stimulation (males, P = 0.09; females, P = 0.8). The referral areas for pain evoked by mechanical and thermal stimuli were larger in females compared with males both before and after acid perfusion (P = 0.002). In females only the referred pain area increased to heat stimulations (P = 0.02). Acid infusion resulted in a more hyperreactive esophagus (P = 0.03) but the hyperreactivity was not gender-dependent. In conclusion, males were more sensitive to mechanical and chemical esophageal stimuli and showed acid-evoked mechanical hyperalgesia. Females had significantly larger referred pain areas to the stimulations. The differentiated response to peripheral and central pain mechanisms may explain the gender-related differences seen in several gastrointestinal disorders.

Adult↗
PubMed2005

Statistical modeling of the response characteristics of mechanosensitive stimuli in the human esophagus.

UNLABELLED: It is believed that mechanical stimuli of the human gut activate afferents responding to either noxious or normal, physiologic stimuli. They might be able to sensitize without relation to the contractile state of the smooth muscle. The current study aimed to verify the above characteristics by using a statistical model based on correlation analysis. The esophagus was distended with a bag in 32 healthy subjects by using an inflation rate of 25 mL/min. The luminal cross-sectional areas and sensory ratings were determined during the distentions. The stimuli were repeated after relaxation of the smooth muscle with butylscopolamine and after sensitization with hydrochloride acid. A positive correlation between the sensory responses to distention was found in the non-painful and painful ranges, respectively, but correlations between non-painful and painful ratings were nonsignificant. Relaxation of the smooth muscle did not influence the correlations, and sensitization resulted in inter-individual differences and disappearance of the above clustering into painful and non-painful correlations. In conclusion, afferent nerves encoding high-threshold and low-threshold mechanical stimuli of the human esophagus are not correlated and thus probably represent different populations. The response characteristics have no physiologic relationship to the contractile state of the smooth muscle, and sensitization affects all types of afferents. PERSPECTIVES: The article adds information about sensory processing of mechanical gut stimuli in human beings. This might increase our understanding of visceral pain in health and disease and guide the statistical analysis of experimental data obtained in the gastrointestinal tract.

Action Potentials↗
PubMed2005

Somatosensory changes in the referred pain area in patients with cholecystolithiasis.

BACKGROUND AND AIMS: Patients with abdominal pain provoked by acute cholecystitis increase the somatic sensitivity in the referred somatic pain area. Our aim in the present paper was to examine somatosensory changes in the referred pain area (previously evoked by painful attacks) in patients with uncomplicated gallstone disease and to evaluate the possible relation between referred pain patterns and clinical findings. Somatosensory changes in these areas may be important in the persistent pain after treatment and may help to develop treatment strategies for abdominal pain in the post-cholecystectomy syndrome. SUBJECTS: Forty-two patients with symptomatic cholecystolithiasis, confirmed ultrasonographically, were studied in the pain-free period. METHODS: Sensitivity and pain thresholds for standardized experimental sensory testing including different modalities: pinprick, pinching, heat, cold, pressure, and single and repeated electrical stimulation were studied in the area where the pain was referred to during the acute attacks, and in a control area on the contralateral side of the abdomen. RESULTS: Patients with verified cholecystolithiasis showed hyperalgesia to pinprick (26% of subjects, P < 0.05) and cold stimuli (21% of subjects, P < 0.05) in the referred pain area. There was also a significant reduction in sensation/pain thresholds (indicating hyperalgesia) in the referred pain area to single (P = 0.007/P = 0.002) and repeated electrical (P = 0.017/P = 0.043) stimuli, as well as in pain threshold to pinching and mechanical stimuli (P = 0.049/P < 0.001). There were no significant relations between the hyperalgesia and the clinical findings. CONCLUSION: Cholecystolithiasis leads to significant hyperalgesia in the somatic area, where pain was referred to during the acute attacks. This is explained by viscero-somatic convergence mechanisms in the central nervous system. Therefore, central neuroplastic changes may be significant in diseases related to the gallbladder such as the post-cholecystectomy syndrome.

Acute Disease↗