Spinal anaesthesia inhibits central temporal summation

Abstract

SummaryIn a previous investigation we found that extradural anaesthesia did not adequately inhibit temporal summation of repeated electrical stimuli: pain to repeated stimuli was blocked in only one of 10 patients, and pain thresholds to repeated stimuli were significantly lower than pain thresholds to a single stimulus. In this study we have investigated in 10 patients the effect of spinal anaesthesia on temporal summation, assessed by repeated electrical stimulation of the sural nerve. Plain 0.5% bupivacaine 18 mg was injected at L2-3. The pain threshold to a single electrical stimulus, summation threshold (increase in perception during repeated electrical stimuli with five impulses of the same intensity at 2 Hz), pinprick and cold sensation were assessed. After spinal anaesthesia, pain to both single and repeated stimulation, and pinprick and cold sensation, disappeared in all patients. We conclude that spinal anaesthesia inhibits temporal summation elicited by repeated electrical stimulation. (Br. J. Anaesth. 1997; 78: 88-89) Key words Anaesthetic techniques, subarachnoid. Pain, experimental. Pain, threshold.Repetition of a peripheral stimulus can cause increased pain perception (temporal summation). Increased and prolonged firing of dorsal horn neurones after repeated stimulation 1 (central sensitization) is probably the mechanism explaining temporal summation.Repeated cutaneous stimulation can be used to investigate temporal summation in humans.2 Nociceptive reflex and subjective pain thresholds after repeated stimulation have been found to be increased slightly by isoflurane concentrations used for surgical analgesia, 3 ketamine 4 and alfentanil, 5 although none of these drugs adequately blocked temporal summation. In a previous investigation, 6 we found that even extradural anaesthesia did not completely block temporal summation of repeated electrical stimuli: pain to repeated stimuli was blocked in only one of 10 patients, and pain thresholds to repeated stimuli were significantly lower than pain thresholds to a single stimulus.The aim of this study was to assess the effect of spinal anaesthesia on temporal summation, assessed by repeated electrical stimulation. Methods and resultsWe studied 10 ASA I-II patients (five male), median age 43 (range 18-54) yr, median body weight 71 (54-85) kg and median height 170 (157-182) cm, undergoing spinal anaesthesia for elective surgery. Exclusion criteria were: age less than 18 or more than 65 yr, heart disease, pregnancy, opioid intake during the last 2 weeks, intake of other analgesics during the last 24 h, alcohol abuse and use of psychotropic drugs. The study was approved by the local Ethics Committee and informed consent was obtained from all patients. Patients were not premedicated. Spinal anaesthesia was performed in the sitting position, at L2-3, with a 27-gauge Quincke needle, by the midline approach. Plain 0.5% bupivacaine 18 mg was injected over 40-45 s, with the bevel of the needle pointing cranially. Cerebrospinal fluid (0.2 ml) was aspirated and r...

Intrathecal drug spread

“…pinprick, cold) may be blocked, but spinal cord mechanisms may result in repeated stimuli (temporal summation) or stimuli from adjacent regions (spatial summation), evoking pain and revealing a 'failed block'. Intrathecal block is better than epidural at inhibiting spatial summation, 31 and this partly explains the more profound block produced. In addition, demonstration of the segmental extent of block of one modality does not enable accurate prediction of any other.…”

Effects of spinal anaesthesia versus epidural anaesthesia for caesarean section on postoperative analgesic consumption and postoperative pain

“…Different sites of action of local anaesthetics (and opiates) with differences in blocking central sensitization may contribute to a preemptive effect. In a clinical model, it was shown that spinal anaesthesia was able to suppress temporal summation, whereas EDA had only partial effects [10,11]; however, results of clinical studies regarding the value of preemptive analgesia are controversial [12].…”

Epidural bolus injection with alkalinized lidocaine improves blockade of the first sacral segment — a brief report

“…13 Our results suggest that epidural anesthesia with alkalinized 2% lidocaine and epinephrine may inhibit temporal summation also. Protection of sensory neurons against central sensitization may offer FIGURE 1 Changes in pain threshold (A, B).…”