Summary Six patients undergoing paravertebral blocks for chronically painful conditions Key wordsEquipment; thermal imaging. Anaesthetic techniques, regional; paravertebral block.Paravertebral analgesia is advocated for surgical procedures of the abdomen wherever the afferent input is predominantly unilateral e.g. nephrectomy, cholecystectomy, but it is particularly effective when used to treat the pain of posterolateral thoractomy [ 11. However, despite numerous studies showing the clinical safety and efficacy of this block [ 1-51, there appear to be some reservations which have been voiced in vague terms by some [6, 71 and more specifically by others [8]. The former include the suggestion that the technique is hazardous and ineffective and the latter that paravertebral spread rarely exceeds two dermatomes with evidence of sympathetic blockade being seen in fewer than 5% of patients. Rather than simply add further anatomical data, we undertook an objective physiological assessment of the extent of the somatic and sympathetic blockade achievable with a single percutaneous paravertebral injection. Patients and MethodsThe study was approved by the hospital ethics committee and informed consent was 'obtained from all patients. Percutaneous paravertebral blocks were perfonned in six patients presenting for treatment of chronically painful chest wall conditions (post-thoracotomy neuralgia, intercostal neuralgia and postherpetic neuralgia). Each patient underwent pre-operative automated cardiovascular data collection consisting of noninvasive pulse and blood pressures in the sitting and supine positions (Datascope 22001). Anterior, posterior and lateral thermographic control views of the naked trunk and limbs were obtained pre-operatively with a Starsight thermal imaging camera (Insight Vision Systems, Malver). Pre-operative pinprick testing was normal in all patients. The blocks were performed by a single operator experienced in this technique (J.R.) and the method used was that of Eason and Wyatt [2] supplemented with radiographic screening and the use of radio-opaque contrast medium. Following negative aspiration, 15 ml of 0.5% bupivacaine was injected over 60 s as a single bolus (with multiple aspirations) at a mean dermatomal level of T,,, with a range of T,-, to T,,,, . Postinjection data collection was undertaken by two observers (D.I. and S.P.S.C.) and consisted of pinprick mapping of the extent of the block, repeated thermographic imaging at 5min intervals until a stable image was obtained, 5min sitting and lying cardiovascular parameters and documentation of any side effects.

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Fluctuations in female sex hormones may be responsible for the high prevalence of Raynaud's phenomenon (RP) observed in premenopausal women. These hormones are known to act on central and peripheral thermoreceptors. In an attempt to establish whether cold sensitivity is altered during the menstrual cycle 50 premenopausal women were investigated. Of these, 26 had primary RP and 24 acted as controls. Each subject was exposed to environmental heating and cooling at three stages of the menstrual cycle to coincide with peaks and troughs in hormone levels. These stages were menstruation, periovulation, and during the midluteal phase. Finger hemodynamics was assessed by means of venous occlusion strain gauge plethysmography and fingertip temperature. Core temperature was assessed with an oral thermocouple. The results show that cold sensitivity was altered during the menstrual cycle in both groups with the fastest finger rewarming pattern during menstruation. Moreover, a significant difference was observed in core temperature between the two groups during the midluteal phase. As a group, subjects with RP failed to show a significant rise in core temperature following ovulation. The authors conclude that the menstrual cycle is associated with changes in the effect of cold on digital blood flow.

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Vasomotor changes occur in the arm after hemiplegic stroke. Previous studies have provided conflicting results, with most showing an increase in skin temperature of the hemiplegic arm. However, a number of patients complain of distressing coldness of the hemiplegic arm. Eleven patients with symptomatic coldness and 10 patients with hemiplegia but no coldness were recruited. The severity of the symptom of coldness was compared by questionnaire with other common symptoms after stroke. A thermographic camera was used to record the finger skin temperature response to cold stress. Blood flow to both hands was also measured simultaneously by means of two plethysmographs. In all patients there were no symptoms in the unaffected arm, and this was used as a control. The symptom of coldness rated highly compared with other symptoms. In the symptomatic group the finger temperature on the hemiplegic side was lower at rest (median difference at rest, 0.65 degrees C; P < .0001) and at all times after cold stress. In the asymptomatic group the fingers on the hemiplegic side were colder at rest and after initial cooling (median temperature difference, 0.2 degrees C) but at no other time. Hand blood flow on the hemiplegic side was also decreased in the symptomatic group by 35%. This was not seen in the asymptomatic group. Coldness of the hand may be a severe and distressing symptom in some patients after hemiplegia. Symptomatic patients have lower finger skin temperatures at rest and after standard cold stress. These symptomatic patients also had reduced blood flow to the hemiplegic hand.