Sharp Sensation Research Articles

Differential epidural block.

Loss of sensation to pinprick and cold are commonly used to test the extent of epidural anesthesia. To see what difference exists between the level of epidural block determined by various sensory modalities, we performed this study in ten volunteers using epidural anesthesia with plain 3% chloroprocaine hydrochloride. Four injections of chloroprocaine were made via an epidural catheter inserted at L2-3 with increasing larger volumes. Sensory modalities tested were (1) absence of sensation when tested by pinprick (anesthesia), (2) loss of a sharp sensation compared to an unblocked dermatome when tested by pinprick (analgesia), and (3) loss of cold sensation when tested with an alcohol swab compared to an unblocked dermatome. At 20 minutes after each injection the level of anesthesia was found to be most caudad and the level of analgesia most cephalad. The zone of differential block was greater than four dermatomes at the highest level of block tested. The level of loss of cold sensation was found between the other two levels. Differences between the levels of analgesia and cold sensation tended to be greater with more extensive block. Differences between levels of anesthesia and cold sensation did not significantly change as the extent of epidural anesthesia was increased. This study establishes the existence of a differential epidural anesthesia during high thoracic block with chloroprocaine and suggests that the intensity of block diminishes as distance from site of injection increases.

Weighted needle pinprick sensory thresholds: a simple test of sensory function in diabetic peripheral neuropathy.

A simple device is described, consisting of 12 weighted 23 gauge disposable needles (0.2 to 5.2 g), for testing sensation in busy diabetic clinics. The pinprick sensory threshold (PPT) is the lightest weighted needle which consistently elicits a sharp sensation. The subjects were 48 healthy controls (hospital staff), 44 diabetic patients without neuropathic symptoms, and 35 diabetic patients with chronic painful neuropathy. In the controls, the mean PPT from the right hand and foot obtained on two test occasions a week apart did not differ significantly. In diabetic patients without symptomatic neuropathy, the mean PPT in the right hand and right foot were significantly higher than in the controls. The diabetic patients with painful neuropathy had clearly increased mean PPT in the right hand and foot compared with controls. Marstock thermal limen in diabetic patients with painful neuropathy correlated significantly with PPT determinations. PPT and thermal thresholds probably give comparable information on small fibre dysfunction in diabetic patients with symptomatic neuropathy. Compared with thermal threshold determinations however, the weighted needle apparatus is inexpensive, simple, and rapid to use.

AN INVESTIGATION IN MAN INTO THE RELATIVE POTENCY OF LIGNOCAINE, BUPIVACAINE AND ETIDOCAINE

The relative potency of lignocaine, bupivacaine and etidocaine was estimated by forearm skin weals in four volunteers. Potency was estimated as the time to half-recovery of a sharp sensation in response to a needle-prick. The increase in duration of action with increased concentration was greater for bupivacaine and etidocaine as compared with lignocaine. At the same concentrations, bupivacaine had a longer duration of action than etidocaine. However, etidocaine 1% had a longer duration of action than bupivacaine 0.5%.

Perforated ear drum following home permanent wave.

This case is reported because of the widespread use of the advertised home permanent lotions. It may prove to be a unique case. On the other hand, it may stimulate the reporting of other similar experiences. REPORT OF A CASE Twenty-four hours prior to being examined, M. M., a woman, 53, was giving herself a home permanent wave of popular brand, which she had used on previous occasions. Following the directions, she applied the neutralizer to her hair, to arrest the action of the waving lotion. Some of the neutralizer ran into her left ear canal, and immediately she became aware of a sharp burning sensation, which ceased after water was applied in the ear. Several minutes later, she noted a sensation of fulness and crackling in the left ear and some loss of hearing. During the examination, the patient complained of residual fulness and hearing loss in the left

The emergence of a tonal sensation.

Abstract : When the absolute threshold of auditory acuity for pure tones is carefully explored with fine intensity steps, a region called the 'zone of detectability' can be noticed by experienced subjects. In this zone, pure tones can be detected but cannot be said to have a true pure-tone quality. This zone of detectability is defined as the intensity area between a 50% detection threshold and a 50% pure-tone threshold. Two thresholds were simultaneously determined at each of 6 frequencies, 500, 1000, 2000, 4000, 8000, and 14000 cps. Two experienced subjects were used. The zone of detectability varied at random from 2-4 db independent of frequency. It was shown that particularly for the higher frequencies, an experienced subject can select a certain criterion of tonality and maintain it with considerable precision. The subject matched a variable frequency of very low sensation level to a standard frequency of 10 db sensation level. The frequency-match was progressively better as the intensity increased from 0 to 10 db sensation level, and the course of this improvement was taken to symbolize the gradual nature of the emergence of a tonal sensation from an indefinite 'something' to the sharp sensation of a clear pure tone. It was reasoned that the subjective criterion of 'tonality' which a subject can select and maintain is indeed one of pitch rather than of loudness; but it was concluded that the phenomenon depends upon the intensity of the stimulus rather than upon a change in its frequency-composition.