Preemptive analgesia

[Does a means exist for prevention of postoperative pain?]

Postoperative pain can be prevented through pharmacological and non pharmacological means. The influence of the interval between therapy and surgical stimulus, which corresponds to "pre-emptive analgesia" in English-speaking countries (comparison of preoperative administration with pre- and postoperative administration of the same analgesic) has been assessed by numerous studies of good methodological quality. In spite of the initial promising results, most of the results published at present are negative. In an enlarged concept of postoperative pain prevention, various trials have demonstrated the benefits of the choice of the surgical approach, as well as the psychological preparation of the patient for surgery.

Characteristics of temporal summation of second pain sensations elicited by brief contact of glabrous skin by a preheated thermode

Temporal summation of sensory intensity was investigated in normal subjects using novel methods of thermal stimulation. A Peltier thermode was heated and then applied in a series of brief (700 ms) contacts to different sites on the glabrous skin of either hand. Repetitive contacts on the thenar or hypothenar eminence, at interstimulus intervals (ISIs) of 3 s, progressively increased the perceived intensity of a thermal sensation that followed each contact at an onset latency > 2 s. Temporal summation of these delayed (late) sensations was proportional to thermode temperature over a range of 45-53 degrees C, progressing from a nonpainful level (warmth) to painful sensations that could be rated as very strong after 10 contacts. Short-latency pain sensations rarely were evoked by such stimuli and never attained levels substantially above pain threshold for the sequences and temperatures presented. Temporal summation produced by brief contacts was greater in rate and amount than increases in sensory intensity resulting from repetitive ramping to the same temperature by a thermode in constant contact with the skin. Variation of the interval between contacts revealed a dependence of sensory intensity on interstimulus interval that is similar to physiological demonstrations of windup, where increasing frequencies of spike train activity are evoked from spinal neurons by repetitive activation of unmyelinated nociceptors. However, substantial summation at repetition rates of > or = 0.33 Hz was observed for temperatures that produced only late sensations of warmth when presented at frequencies < 0.16 Hz. Measurements of subepidermal skin temperature from anesthetized monkeys revealed different time courses for storage and dissipation of heat by the skin than for temporal summation and decay of sensory intensity for the human subjects. For example, negligible heat loss occurred during a 6-s interval between two trials of 10 contacts at 0.33 Hz, but ratings of sensory magnitude decreased from very strong levels of pain to sensations of warmth during the same interval. Evidence that temporal summation of sensory intensity during series of brief contacts relies on central integration, rather than a sensitization of peripheral receptors, was obtained using two approaches. In the first, a moderate degree of temporal summation was observed during alternating stimulation of adjacent but nonoverlapping skin sites at 0.33 Hz. Second, temporal summation was significantly attenuated by prior administration of dextromethorphan, a N-methyl-D-aspartate receptor antagonist.

A comparative study of thoracoscopic vs open removal of benign neurogenic mediastinal tumors

STUDY OBJECTIVE

To assess the relative benefit of thoracoscopy vs open thoracotomy in the removal of benign neurogenic, mediastinal tumors (BNMTs).

DESIGN

Retrospective comparative study of thoracoscopy and open thoracotomy.

SETTING

Patients underwent surgery at the thoracic surgical services of two institutions from 1988 to 1994. Patients who underwent thoracoscopy were operated on more recently, 1992 to 1994. Patients who had thoracotomies underwent resection from 1988 to 1992.

PATIENTS

All adult patients undergoing isolated removal of BNMTs at both institutions were included. Eleven patients underwent removal by posterolateral thoracotomy while six patients underwent thoracoscopic removal.

INTERVENTIONS

BNMTs were removed by standard posterolateral thoracotomy or by three-hole thoracoscopic techniques with extension of incisions and conversion to an open procedure as necessary.

MEASUREMENTS AND RESULTS

Larger tumors were more difficult to remove thoracoscopically. Two cases of transient postoperative ptosis were noted among the patients who underwent thoracoscopy. Operative time was longer in the thoracoscopy group (171 vs 112 min; p<0.05). Postoperative stay was significantly shorter (2.6 vs 4.5 days; p<0.02) and return to work tended to be more rapid (4.3 vs 7.7 weeks; p=0.13) among patients who underwent thoracoscopy.

CONCLUSIONS

Thoracoscopic resection of BNMTs can be achieved safely and effectively with more rapid postoperative recovery when compared with an open thoracotomy approach to these mediastinal tumors.