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The present study investigates stop signals and their effects on the pain and distress of patients undergoing a stressful medical procedure. Thirty-six chronic pain patients (17 men, 19 women) attending an out-patient operating theatre for diagnostic nerve blocks/local anaesthetic injections were allocated to one of two conditions (experimental and control). All patients received a standard information leaflet concerning the forthcoming injections. Additional information was given to those in the experimental group on four occasions (three orally, one written) before the injections which stated that they could halt the procedure at any time by saying 'stop'. Subjective measures of anxiety, pain, distress, sense of control over the procedure as well as observer ratings of patient distress and pain behaviour were obtained before, during and after the injections. After initial differences in pre-injection pain were controlled for the experimental group, patients rated themselves as less distressed during the injections and recorded lower state anxiety following treatment. In view of various methodological limitations of the present study its findings may only be accorded 'pilot study' status. These limitations are explored in the discussion along with their implications for a more robust replication study. Nevertheless the present findings provide tentative support for the hypothesis that the use of stop signals can reduce the stressful nature of diagnostic nerve blocks.

Patients with chronic pain often present with complex multidimensional problems. Satisfactory management requires attention to the various components of the pain as well as to the resulting disability and the psychosocial dimensions of the problem.

Summary A case of transient sympathetic block of the arm following percutaneous intercostal nerve injections is described and the possible aetiology discussed.

The spread of solution after a standardized paravertebral injection was studied to determine the precision and predictability of paravertebral spread. The spread of 5 ml of a solution of radiological contrast medium (sodium iothalamate) and local anesthetic mixture after 45 (34 thoracic, 11 lumbar) paravertebral injections was studied in 31 patients by radiography and computed tomography and correlated with the clinical effects. Spread confined to the paravertebral area occurred after only eight (18%) injections. Spread was epidural after 31 (70%) injections and exclusively so in 14 (31%) injections. Mean sensory loss was greater after epidural spread, but a wide range of sensation loss was observed with all patterns of spread. Intrapleural spread occurred after three injections, as did spread into the psoas muscle. In addition, measurements were made of 114 paravertebral spaces in 20 patients by means of computed tomography. Dimensional factors identified as possibly leading to complications of a paravertebral injection included narrow width of the thoracic transverse processes (mean, 3.18 cm; range, 2.1-4.2 cm) and the wide range in paravertebral dimensions. The distance from bony landmarks to pleura frequently fell outside the limits recommended by many standard texts. We conclude that the spread of a small volume of solution after paravertebral injection is imprecise and unpredictable. Neurolytic and diagnostic paravertebral injections performed without the aid of radiological imaging and contrast media should be regarded as hazardous and interpreted with extreme caution.