Toxicity of topical lidocaine applied to the breasts to reduce discomfort during screening mammography

tDCS peripheral nerve stimulation: a neglected mode of action?

Transcranial direct current stimulation (tDCS) is a noninvasive neuromodulation method widely used by neuroscientists and clinicians for research and therapeutic purposes. tDCS is currently under investigation as a treatment for a range of psychiatric disorders. Despite its popularity, a full understanding of tDCS's underlying neurophysiological mechanisms is still lacking. tDCS creates a weak electric field in the cerebral cortex which is generally assumed to cause the observed effects. Interestingly, as tDCS is applied directly on the skin, localized peripheral nerve endings are exposed to much higher electric field strengths than the underlying cortices. Yet, the potential contribution of peripheral mechanisms in causing tDCS's effects has never been systemically investigated. We hypothesize that tDCS induces arousal and vigilance through peripheral mechanisms. We suggest that this may involve peripherally-evoked activation of the ascending reticular activating system, in which norepinephrine is distributed throughout the brain by the locus coeruleus. Finally, we provide suggestions to improve tDCS experimental design beyond the standard sham control, such as topical anesthetics to block peripheral nerves and active controls to stimulate non-target areas. Broad adoption of these measures in all tDCS experiments could help disambiguate peripheral from true transcranial tDCS mechanisms.

Influence of Discomfort Tolerance of Women who Undergo Mammography on the Perceived Pain Intensity Due to the Procedure

Objective

This study aims to determine the capacity to tolerate discomfort by women who undergo mammography.

Materials and Methods

The data were obtained using the face-to-face interview method immediately after the procedure with women who undergo mammography (n=132). Demographic data collection form and the Discomfort Intolerance Scale was used for data collection.

Results

Among the women, 78.8% experienced pain during mammography and the pain intensity was determined as 3.55 (standard deviation=3.00) on the 0-10 Visual Analogue Scale. Women who were not on pain relievers and nonsmokers have high discomfort tolerance. Women who were consuming substances containing methylxanthine (eg. chocolate) tend to avoid discomfort. Women with a history of breast mass and abnormal test results did not avoid discomfort as much as women who undergo regular checkup mammograms. Most of the women experience pain during mammography, and avoidance from discomfort increases as the perceived pain during the procedure increases.

Conclusion

Conducting different studies using the same scale can be useful in evaluating the discomfort experienced during mammography and its contribution to reducing pain.

Investigation of the Inhibitory Effect of Simvastatin on the Metabolism of Lidocaine Both in vitro and in vivo

Background

Lidocaine has cardiovascular and neurologic toxicity, which is dose-dependent. Due to CYP3A4-involved metabolism, lidocaine may be prone to drug-drug interactions.

Materials and Methods

Given statins have the possibility of combination with lidocaine in the clinic, we established in vitro models to assess the effect of statins on the metabolism of lidocaine. Further pharmacokinetic alterations of lidocaine and its main metabolite, monoethylglycinexylidide in rats influenced by simvastatin, were investigated.

Results

In vitro study revealed that simvastatin, among the statins, had the most significant inhibitory effect on lidocaine metabolism with IC₅₀ of 39.31 µM, 50 µM and 15.77 µM for RLM, HLM and CYP3A4.1, respectively. Consistent with in vitro results, lidocaine concomitantly used with simvastatin in rats was associated with 1.2-fold AUC_(0-t), 1.2-fold AUC_(0-∞), and 20%-decreased clearance for lidocaine, and 1.4-fold C_max for MEGX compared with lidocaine alone.

Conclusion

Collectively, these results implied that simvastatin could evidently inhibit the metabolism of lidocaine both in vivo and in vitro. Accordingly, more attention and necessary therapeutic drug monitoring should be paid to patients with the concomitant coadministration of lidocaine and simvastatin so as to avoid unexpected toxicity.

Takotsubo Cardiomyopathy Induced by Epinephrine Infiltration for Liposuction: Broken Heart Syndrome

Broken heart syndrome, more commonly known as Takotsubo cardiomyopathy (TCM), is an acute cardiac condition. It is characterized by regional cardiac wall motion abnormalities triggered by physical or emotional stress or administration of catecholamines such as epinephrine. The initial clinical presentation is similar to an acute coronary syndrome and must be ruled out. Visualization of the characteristic wall motion will trigger the diagnosis of TCM. In this case report, we present a 50-year-old woman with additional liposuction and fat grafting after autologous breast reconstruction. Shortly after infiltration with a solution containing epinephrine to achieve vasoconstriction, hypotension and bradycardia was noticed. This escalated into full asystole for which cardiac resuscitation was required. ST-elevations and a decrease in systolic function were clear indicators for urgent coronarography and ventriculography. These confirmed the diagnosis of TCM. Infiltration with epinephrine-containing products to achieve local vasoconstriction is used routinely. Medical professionals should be aware that this can trigger a TCM with an estimated mortality rate of 5%. No evidence of a specific preventive measure currently exists. We know that women with a neurologic or psychiatric comorbidity and high levels of stress are more at risk. Reducing stress and anxiolytic medication prior to surgery could be useful. We also know that the cardiac wall motion abnormality is mainly related to β-adrenoreceptors. The use of a selective α-adrenoreceptor agonist could be considered. Further research in the pathophysiology and incidence of TCM could improve identification of patients at risk and lead to more effective prevention and treatment.

LEVEL OF EVIDENCE: 5

Painful Reality: Inappropriate Provider Management of Pain as a Determinant of Health Care Avoidance

Although pain is often characterized as a subjective, highly individualized phenomenon, in fact, numerous elements which are simply biological in nature underlie interpersonal differences in pain experience that influence the effectiveness of provider pain management. Elements acting at the level of tissues and cells include signal-transmitting molecules in pain pathways; elements acting at the level of the whole person comprise entire brain networks and anatomic elements fostering pain vulnerability. However, knowledge of these elements and translation of such knowledge into practical means for relieving patient pain is dismayingly sparse across the total spectrum of health care professionals. A serious consequence of this knowledge and action gap is that isolated, or worse yet, repeated, pain experiences may lead to profound mistrust of the health care system and its providers and to health care avoidance (e.g., mammography). This article outlines a biologic knowledge base and proposed remedies to improve pain management across the entire domain of health care. Key components of this approach include enhanced education for providers and informational outreach to health care consumers, clarifying pain mechanisms to both constituencies. Moreover, increased accountability within the health care system is needed, both in knowing and applying well-established biomedical knowledge and in best using technical and interpersonal skills necessary for effective pain management.