Diffuse optical signals in response to peripheral nerve stimulation reflect skeletal muscle kinematics

Previously we have reported a near-infrared optical response in the region occupied by a peripheral nerve that is distal to the site of electrical stimulation of that peripheral nerve. This “intermediate” signal is vascular in nature but its biological origin not been elucidated. In the present study, an animal model of the signal has been created and our human studies expanded to directly investigate the contribution of non-artifactual vascular motion induced by muscle contraction to the biological origin of this signal. Under non-invasive conditions during stimulation of the exposed sciatic nerve of the Sprague-Dawley rat, optical responses are robust. These signals can be abolished both pharmacologically and surgically using methods that eliminate muscle motion while leaving the electrophysiological health of the nerve intact. In human studies, signals that are elicited on stimulation of nerves containing motor axons, both within and outside the predicted imaging volume of the spectrometer, have similar temporal characteristics of those previously observed. Moreover, stimulation of sensory nerves alone does not elicit an optical response. These results strongly suggest that the intermediate signals are derived from stimulus-induced muscle contraction (whether via an innervating nerve or by direct stimulation) causing translational vascular motion within the optically interrogated region

Dexmedetomidine sedation in ICU

Dexmedetomidine (DEX), a highly selective α2-adrenergic receptor agonist, is the newest agent introduced for sedation in intensive care unit (ICU). The sedation strategy for critically ill patients has stressed light sedation with daily awakening and assessment for neurologic, cognitive, and respiratory functions, since Society of Critical Care Medicine (SCCM) guidelines were presented in 2002. The traditional GABAergic agents, including benzodiazepines and propofol, have some limitations for safe sedatives in this setting, due to an unfavorable pharmacokinetic profile and to detrimental adverse effects (such as lorazepam associated propylene glycol intoxication and propofol infusion syndrome). DEX produces it's sedative, analgesic and cardiovascular effects through α2 receptors on the locus ceruleus (LC). Activities of LC, the tuberomammillary nucleus (TMN) are depressed and activity of the ventrolateral preoptic nucleus (VLPO) is increased during DEX sedation, which is similar in features to normal non-REM (NREM) sleep. At the same time, perifornical orexinergic activity is maintained, which might be associated with attention. This mechanism of action produces a normal sleep-like, cooperative sedation. The characteristic feature of sedation, together with a concomitant opioid sparing effect, may decrease the length of time spent on a ventilator, length of stay in ICU, and prevalence and duration of delirium, as the evidence shown from several comparative studies. In addition, DEX has an excellent safety profile. In conclusion, DEX is considered as a promising agent optimized for sedation in ICU

EPHEDRINE ENHANCES ANALGESIC EFFECT OF MORPHINE

Morphine-ephedrine interaction on analgesia was studied in mice (n = 240) and in post-operative patients (n = 32). It was found that combining morphine and ephedrine enhances analgesia which is not significantly different from the effect of morphine given alone at double dose

Postoperative shivering in children and causative factors.

Background: The aim of this study is to investigate the incidence of shivering in children and to reveal the causative factors as well as any possible clinical implications

Middle Cerebral Artery Infarction Associated with Sildenafil Citrate (Viagra) Use

Introduction: Sildenafil is a phosphodiesterase 5 enzyme inhibitor used in the treatment of erectile dysfunction and pulmonary hypertension. The use of sildenafil with nitrates is well known to cause myocardial ischemia. However, patients with a history of hypotension, arrhythmia, previous myocardial infarction, or stroke should be given sildenafil carefully. A few cases have been reported in the literature related to ischemic stroke and transient ischemic attack due to sildenafil use