Comparison of heat and mechanical receptive fields of cutaneous C-fiber nociceptors in monkey

1. Receptive-field properties were investigated in cutaneous C-fiber nociceptive afferents (CMH) responsive to mechanical and heat stimuli. Teased-fiber techniques were used to record from 28 CMHs that innervated the hairy skin of upper or lower limb in anesthetized monkeys. 2. The response to mechanical stimuli was studied with the use of calibrated von Frey probes. The response to heat stimuli was studied with the use of a laser thermal stimulator that provided stepped increases in skin temperature with rise times to the desired temperature near 100 ms. The size of the receptive field (RF) for mechanical stimuli was determined by use of a suprathreshold stimulus that consisted of a 0.5-mm-diam probe that exerted a 200-mN force (10 bar). The size of the heat RF was determined by use of a 49 degrees C stimulus applied to a 7.5-mm-diam area for 1 s. 3. Heat thresholds were determined with an ascending series of stimulus intensities and were found to be stable over many hours: they ranged from 37 to 46 degrees C (mean, 41.1 degrees C). Mechanical thresholds ranged from 1.3 to 7.3 bar (mean, 3.3 bar). There was no correlation between mechanical and heat thresholds. Both thresholds extended well below the corresponding psychophysical pain thresholds in the literature. This suggests that spatial and/or temporal summation of C-fiber input are important for pain induced by either stimulus modality. 4. Mechanical RF diameters ranged from 3.3 to 9.6 mm (mean, 4.7 mm); heat RF diameters ranged from punctate (less than 1 mm) to 9.5 mm (mean, 4.3 mm). There was a significant linear correlation between mechanical and heat RF sizes with a slope of one. The distance between the center of the mechanical RF and the center of the heat RF along one axis ranged from 0 to 1.1 mm (mean, 0.4 mm). These data indicate that the heat RFs coincided with the mechanical RFs. 5. Within the mechanical RF determined with the suprathreshold stimuli, all CMHs had one or more punctate areas of maximal mechanical sensitivity where mechanical threshold was lowest. Heat excitability extended greater than 2 mm beyond these mechanically sensitive spots. Because lateral transmission of the heat stimulus is small, this indicates that heat transduction occurs outside the regions of maximal mechanical sensitivity. 6. Both the threshold to heat and the response magnitude at suprathreshold intensities depended on the percentage of the RF area overlapped by the heat stimulus. This indicates that multiple transducer sites probably contribute to the total evoked response.(ABSTRACT TRUNCATED AT 400 WORDS)     

Transcatheter aortic valve implantation in a heart transplant recipient: a case report

Transcatheter aortic valve implantation (TAVI) has evolved into a feasible therapeutic option for the management of selected patients with severe aortic stenosis and high or prohibitive risk for standard surgery. Symptomatic severe aortic stenosis occasionally occurs in the allograft long after heart transplantation. Because of specific characteristics and comorbidities of heart transplant recipients, these patients may be considered candidates for this less invasive approach. We report a first case of successful transapical TAVI in a heart transplant recipient with symptomatic severe calcific aortic valvular disease and relevant comorbidities long after heart transplantation.     

Detection of coronary artery stenoses with multislice helical CT angiography

OBJECTIVES: The authors compared multislice CT angiography and selective angiography for the assessment of coronary artery disease. METHODS: In 28 patients, the presence and degree of coronary artery stenoses were determined in coronary segments prepared with beta-blocker for good image quality with multislice CT. RESULTS: In 187 coronary artery segments, sensitivity, specificity, and negative predictive value for the detection of stenoses >50% with multislice CT angiography were 81%, 90%, and 97%, respectively. The agreement for determining the degree of stenoses with multislice CT angiography and selective coronary angiography was only moderate (kappa = 0.58). CONCLUSIONS: Because of the limited spatial resolution, it is not possible with multislice CT angiography to determine the degree the coronary artery stenoses precisely. However, the high negative predictive value indicates that multislice CT may be a suitable tool to reliably rule out coronary artery disease.     

Value of quantitative sensory testing in neurological and pain disorders: NeuPSIG consensus

Quantitative sensory testing (QST) is a psychophysical method used to quantify somatosensory function in response to controlled stimuli in healthy subjects and patients. Although QST shares similarities with the quantitative assessment of hearing or vision, which is extensively used in clinical practice and research, it has not gained a large acceptance among clinicians for many reasons, and in significant part because of the lack of information about standards for performing QST, its potential utility, and interpretation of results. A consensus meeting was convened by the Neuropathic Pain Special Interest Group of the International Association for the Study of Pain (NeuPSIG) to formulate recommendations for conducting QST in clinical practice and research. Research studies have confirmed the utility of QST for the assessment and monitoring of somatosensory deficits, particularly in diabetic and small fiber neuropathies; the assessment of evoked pains (mechanical and thermal allodynia or hyperalgesia); and the diagnosis of sensory neuropathies. Promising applications include the assessment of evoked pains in large-scale clinical trials and the study of conditioned pain modulation. In clinical practice, we recommend the use QST for screening for small and large fiber neuropathies; monitoring of somatosensory deficits; and monitoring of evoked pains, allodynia, and hyperalgesia. QST is not recommended as a stand-alone test for the diagnosis of neuropathic pain. For the conduct of QST in healthy subjects and in patients, we recommend use of predefined standardized stimuli and instructions, validated algorithms of testing, and reference values corrected for anatomical site, age, and gender. Interpretation of results should always take into account the clinical context, and patients with language and cognitive difficulties, anxiety, or litigation should not be considered eligible for QST. When appropriate standards, as discussed here, are applied, QST can provide important and unique information about the functional status of somatosensory system, which would be complementary to already existing clinical methods.     

Querschnittsbereich 14 Schmerzmedizin

Background

The recent introduction of amendments to the medical licensure laws led to the introduction of the field of pain medicine into the study program “Human Medicine”. The implementation has to be completed by all medical faculties before 2016.

Material and methods

Pain medicine was implemented into the model study course“MaReCuM” at the medical faculty in Manheim as a compulsory subject in the year 2010. It is structured into five sections in a longitudinal manner. The core section is the “pain awareness week” in the fifth academic year of the medical studies. The content and structure is based on the German Pain Society (DGSS) curriculum. For the purpose of this study the examination results and the student evaluation forms from the academic years 2010/2011 and 2011/2012 were analyzed.

Results

The students regarded pain medicine as being highly relevant concerning its impact on the professional activities. The competence to develop a specific and individual therapy was of special interest. A good coordination of the contents of teaching between preclinical and clinical teaching was considered to be of major importance.

Conclusions

The DGSS curriculum is a useful tool for the implementation of pain medicine in a study program. In order to improve access to basic pain medicine in general, a combined teaching program consisting of pain medicine and general medicine could be helpful. Pain medicine could be used as a guide for teaching contents of outpatient medicine.     

Simultaneous transcatheter aortic and mitral valve-in-valve implantation in a patient with degenerated bioprostheses and high surgical risk

Transcatheter valve-in-valve implantation is evolving as a promising alternative to reoperative valve replacement in selected high-risk patients, considering the increasing need for redo surgery due to bioprosthetic degeneration in the future. Reoperative double valve replacements are particularly associated with an elevated surgical risk. The transapical access provides the opportunity to approach the aortic and mitral valves during one intervention. We report the case of a successful transcatheter valve-in-valve implantation in the aortic and mitral position within a single procedure.     

Test-retest and interobserver reliability of quantitative sensory testing according to the protocol of the German Research Network on Neuropathic Pain (DFNS): a multi-centre study

Quantitative sensory testing (QST) is an instrument to assess positive and negative sensory signs, helping to identify mechanisms underlying pathologic pain conditions. In this study, we evaluated the test-retest reliability (TR-R) and the interobserver reliability (IO-R) of QST in patients with sensory disturbances of different etiologies. In 4 centres, 60 patients (37 male and 23 female, 56.4 ± 1.9 years) with lesions or diseases of the somatosensory system were included. QST comprised 13 parameters including detection and pain thresholds for thermal and mechanical stimuli. QST was performed in the clinically most affected test area and a less or unaffected control area in a morning and an afternoon session on 2 consecutive days by examiner pairs (4 QSTs/patient). For both, TR-R and IO-R, there were high correlations (r = 0.80-0.93) at the affected test area, except for wind-up ratio (TR-R: r = 0.67; IO-R: r = 0.56) and paradoxical heat sensations (TR-R: r = 0.35; IO-R: r = 0.44). Mean IO-R (r = 0.83, 31% unexplained variance) was slightly lower than TR-R (r = 0.86, 26% unexplained variance, P < .05); the difference in variance amounted to 5%. There were no differences between study centres. In a subgroup with an unaffected control area (n = 43), reliabilities were significantly better in the test area (TR-R: r = 0.86; IO-R: r = 0.83) than in the control area (TR-R: r = 0.79; IO-R: r = 0.71, each P < .01), suggesting that disease-related systematic variance enhances reliability of QST. We conclude that standardized QST performed by trained examiners is a valuable diagnostic instrument with good test-retest and interobserver reliability within 2 days. With standardized training, observer bias is much lower than random variance.     

Type A aortic dissection during late pregnancy in a patient with Marfan syndrome

Purpose

To report the management of a 38-yr-old patient with known Marfan syndrome who presented with acute Stanford type A dissection of the aorta in the 34^th week of pregnancy.

Clinical features

A Cesarean delivery was performed under deep general anesthesia with high-dose opioid administration to avoid tachycardia and hypertension during tracheal intubation and obstetric surgery. Delivery took place less than five minutes after induction of anesthesia, and tracheal intubation of the newborn was required due to opioid-induced hypoventilation. Subsequently, aortic arch repair was performed in the mother after connection to extracorporal bypass. Despite extensive replacement of coagulation factors, severe vaginal bleeding persisted after weaning from extracorporal bypass, and the bleeding stopped only after a hysterectomy was performed. Postoperatively, after a short period in the intensive care unit, mother and child were discharged from hospital in excellent condition ten days after surgery.

Conclusion

Deep general anesthesia for emergency Cesarean delivery while accepting the risk of respiratory depression in the newborn is a viable option for the anesthetic management of life-threatening events such as Stanford type A dissection.