Altered central pain processing after pancreatic surgery for chronic pancreatitis

BACKGROUND

Chronic abdominal pain is common in chronic pancreatitis (CP) and may involve altered central pain processing. This study evaluated the relationship between pain processing and pain outcome after pancreatic duct decompression and/or pancreatic resection in patients with CP.

METHODS

Patients with CP underwent quantitative sensory testing. Pain processing was measured via electrical pain detection (ePDT) and electrical pain tolerance (ePTT) thresholds in dermatomes C5 and L4. Inhibitory descending pain control mechanisms were assessed using the conditioned pain modulation (CPM) paradigm. Healthy controls and patients with CP were compared, and patients with CP and a poor pain outcome (visual analogue scale (VAS) score greater than 30) were compared with those with a good pain outcome (VAS score 30 or less).

RESULTS

Forty-eight patients with CP had lower ePDT, ePTT and CPM responses compared with values in 15 healthy controls (P < 0·030). The sum of ePDT values was lower in patients with a poor pain outcome than in those with a good outcome (median 7·1 versus 11·2 mA; P = 0·008). There was a correlation with the VAS score and the sum of ePDT values (rs  = -0·45, P = 0·016) and ePTT values (rs  = -0·46, P = 0·011), and CPM response (rs  = -0·43, P = 0·006) in patients with CP.

CONCLUSION

After pain-relieving pancreatic surgery, patients with CP exhibit altered central pain processing compared with that in healthy controls. Poor pain outcomes are associated with more central sensitization and more pronociceptive descending pain modulation, and this should be considered when managing persistent pain after pain-relieving surgery for CP.

Role of induced negative and positive emotions in sensitivity to itch and pain in women

BACKGROUND

Itch and pain are common symptoms in skin disease. It has been suggested that negative emotions may play a role in itch and pain. To date, however, the role of emotions has only been studied for pain in experimental studies, not yet for itch.

OBJECTIVES

To investigate the effects of negative and positive emotions on the sensitivity to itch and pain.

METHODS

Film fragments were used to induce a negative or positive emotional state in healthy women. Itch and pain were induced using the following somatosensory stimuli: electrical stimulation, histamine iontophoresis and the cold pressor test.

RESULTS

Results showed that the scores for itch and pain evoked by histamine and the cold pressor test, respectively, were significantly higher in the negative than in the positive emotion condition, whereas tolerance thresholds to electrical stimulation and the cold pressor test, and stimulus unpleasantness scores did not differ between the two conditions.

CONCLUSIONS

These findings for the first time indicate in an experimental design that emotions play a role in sensitivity to somatosensory sensations of both itch and pain.

Generalized and symptom-specific sensitization of chronic itch and pain

BACKGROUND

Physicians are frequently confronted with patients reporting severe itch and pain. Particularly in patients suffering from persistent itch and pain, central and peripheral sensitization processes are assumed to be involved in the long-term maintenance and aggravation of the symptoms. The present study explores generalized and symptom-specific sensitization processes in patients suffering from persistent itch and pain. Specifically, it examines whether patients with chronic itch and pain are more sensitive to somatosensory stimuli (generalized sensitization) and simultaneously perceive somatosensory stimuli as a symptom of their main physical complaint, e.g. pain in chronic pain patients (symptom-specific sensitization).

METHODS

Thresholds for different mechanical and electrical sensory stimuli of Quantitative Sensory Testing were determined in 15 female patients suffering from chronic itch associated with atopic dermatitis, 15 female chronic pain patients diagnosed with fibromyalgia, and 19 female healthy controls. Intensities of itch and pain sensations were rated on a visual analogue scale.

RESULTS

As expected, the patient groups had significantly lower tolerance thresholds for the somatosensory stimuli applied than the healthy controls, supporting generalized sensitization. Moreover, patients with chronic itch consistently reported more itch, while patients with chronic pain partly reported more pain in response to analogous somatosensory stimuli than the healthy controls and the other patient group, indicating symptom-specific sensitization.

CONCLUSION

The present study provides preliminary support that both generalized and symptom-specific sensitization processes play a role in the regulation and processing of somatosensory stimulation of patients with chronic itch and pain.

The management of chronic pain in Switzerland: a comparative survey of Swiss medical specialists treating chronic pain

Chronic pain management by Swiss specialist physicians with the primary hypothesis that pain clinic practitioners conform better to good practice (interdisciplinarity, diagnostic/therapeutic routines, quality control, education) than other specialists treating chronic pain was surveyed. Management of all types of chronic pain by pain clinic practitioners and rheumatologists, oncologists or neurologists was compared via a mailed questionnaire survey (n=125/group). Two hundred and twenty-nine (46%) of 500 mailed questionnaires were returned with similar group return rates. Eighty-six percent of responders find chronic pain therapy very difficult/difficult; they estimate only 45% of these patients achieve good outcomes. Twenty-three per cent of responders belong to an interdisciplinary pain centre, but 72% of chronic pain patients are treated by responders alone. Fifty-nine percent never/only occasionally use therapeutic algorithms, 38% use formal pain diagnostic procedures, 20% have a pain quality control programme. Fifty-one percent lack past pain education, 37% do not attend continuing pain education, 69% agree that pain education is their greatest need. Pain clinic practitioners are more interdisciplinary and use more pain diagnostics than other specialists. They are matched by oncologists in education and success in therapeutic escalation, and bettered by them in algorithm use. Pain clinic practitioners and oncologists bring particular-differing-skills to chronic pain management compared to rheumatologists and neurologists. Chronic pain management diversity may result from differences in malignant and benign pain, and its generally being provided by the speciality treating the underlying cause. This survey identifies targets for improvement in areas fundamental to good chronic pain practice: interdisciplinarity, diagnostic/therapeutic tools, quality management and education.

Changes in sensory processing after surgical nociception

Nociception results in peripheral and central changes in sensory processing. These changes are considered to significantly contribute to postoperative pain and its outcome. Objective measures of changes in sensory processing are now being studied in humans after surgery. Surgical nociception leads to both central excitation (eg, spinal sensitization) and central inhibition (eg, descending inhibition), with inhibition being the dominant response during the first day or so after surgery. Analgesia commenced before surgery (preemptive analgesia) depresses central sensitization and enhances central inhibition. Patients operated on under nonanalgesic anesthesia may exhibit rebound central sensitization for up to 5 days postoperatively after the cessation of postoperative opioid analgesia. There is only a weak relationship between the described objective changes in sensory processing after surgical nociception and subjective clinical pain measures such as pain intensity scales or postoperative analgesic consumption.

Midazolam premedication reduces propofol dose requirements for multiple anesthetic endpoints

PURPOSE

This study investigates the interactions between midazolam premedication and propofol infusion induction of anesthesia for multiple anesthetic endpoints including: loss of verbal contact (LVC; hypnotic), dropping an infusion flex (DF; motor), loss of reaction to painful stimulation (LRP; antinociceptive) and attainment of electroencephalographic burst suppression (BUR; EEG).

METHODS

In a double blind, controlled, randomized and prospective study, 24 ASA I-II patients received either midazolam 0.05 mg x kg(-1) (PM; n = 13) or saline placebo (PO; n = 11) i.v. as premedication. Twenty minutes later, anesthesia was induced by propofol infusion at 30 mg x kg(-1) x hr(-1). ED50, ED95 and group medians for times and doses were determined and compared at multiple anesthetic endpoints.

RESULTS

At the hypnotic, motor and EEG endpoints, midazolam premedication significantly and similarly reduced propofol ED50 (reduction: 18%, 13% and 20% respectively; P <0.05 vs unpremedicated patients) and ED95 (reduction: 20%, 11% and 20% respectively; P <0.05 vs unpremedicated patients). For antinociception (LRP), dose reduction by premedication was greater for propofol ED95 (reduction: 41%; P <0.05 vs unpremedicated patients) than ED50 (reduction: 18%; P <0.05 vs unpremedicated patients). Hemodynamic values were similar in both groups at the various endpoints.

CONCLUSIONS

Midazolam premedication 20 min prior to induction of anesthesia reduces the propofol doses necessary to attain the multiple anesthetic endpoints studied without affecting hemodynamics in this otherwise healthy population. The interaction differs for different anesthetic endpoints (e.g., antinociception vs hypnosis) and propofol doses (e.g., ED50 vs ED95).

Analgesic action of i.v. morphine-6-glucuronide in healthy volunteers

The pharmacodynamics of morphine-6-glucuronide (M-6-G) i.v. were assessed in 12 healthy male volunteers in an open study. After a single bolus dose of M-6-G 5 mg i.v., we measured antinociceptive effects, using electrical and cold pain tests, and plasma concentrations of M-6-G, morphine-3-glucuronide (M-3-G) and morphine. Pain intensities during electrical stimulation (at 30, 60 and 90 min after injection) and ice water immersion (at 60 min) decreased significantly (P < 0.005) compared with baseline. Mean plasma peak concentrations of M-6-G were 139.3 (SD 38.9) ng ml-1, measured at 15 min. Our data demonstrate that M-6-G has significant analgesic activity.

Midazolam premedication and thiopental induction of anaesthesia: interactions at multiple end-points

We have studied the effects of midazolam premedication on multiple anaesthetic end-points (hypnotic, loss of verbal contact (LVC); motor, dropping an infusion flex or bag (DF); analgesic, loss of reaction to painful stimulation (LRP); and EEG, attainment of burst suppression (BUR)) during induction by slow thiopental infusion at a rate of 55 mg kg-1 h-1. Patients received midazolam 0.05 mg kg-1 i.v. (group TM, n = 12) or no midazolam (group T0, n = 13). ED50 and ED95 values and group medians for times and doses at the end-points were measured. Midazolam premedication reduced significantly thiopental ED50 and ED95 values at all end-points (exception for ED95 for BUR). Potentiation was greatest for the motor end-point (dropping the infusion bag (DF)) (ED95 +52%, ED50 +23%, median +39%), and smallest for painful stimulation (LRP) (median +18%; ED50 +13%). For LRP and DF, premedication was associated with significant, non-parallel increases in the slope of the thiopental dose-response curves, resulting in marked potency ratio changes from ED50 to ED95 (LRP +31%, DF +29%). There were no such increases for LVC or BUR. The interaction between midazolam and thiopental varied with the anaesthetic end-point and may also depend on the dose of thiopental. Our data suggest that the mechanism of interaction between midazolam premedication and thiopental was different for motor effects or analgesia (DF, LRP) compared with hypnotic effects or cortical depression (LVC, BUR), in agreement with the different central nervous system substrates underlying these distinct anaesthetic end-points.

Slow EEG-power spectra correlate with haemodynamic changes during laryngoscopy and intubation following induction with fentanyl or sufentanil

We studied nociception-associated arousal following laryngoscopy and intubation in patients scheduled for elective open heart surgery, using EEG power spectra and hemodynamics. Either fentanyl (7 micrograms/kg; n = 30) or sufentanil (1 microgram/kg; n = 30) were given in a randomized fashion to induce anesthesia in heavily premedicated patients, followed by pancuronium bromide (100 micrograms/kg). EEG-power spectra (delta, theta, alpha, beta) as well as mean arterial blood pressure (MAP) and heart rate (HF) were measured at the following end-points: before the induction of anesthesia (control), 1 and 10 minutes after laryngoscopy and intubation (L & I). Linear regression analysis was computed to determine which of the EEG power spectra was most sensitive to detect insufficient blockade of nociceptive-related arousal when correlated with haemodynamics. In the fentanyl group the change in HF closely correlated with the decrease of power in the slow delta- and theta-domain (r2 = 0.98 and r2 = 0.89 respectively) of the EEG. The change in MAP also closely correlated with a decrease in the slow delta- and theta-domain (r2 = 0.97 and r2 = 0.99 respectively). There was little correlation in regard to spectral edge frequency (SEF) and HF and MAP changes (r2 = 0.36 and r2 = 0.12 respectively). In the sufentanil group the change in HF correlated closely with an increase of power in the fast alpha and a decrease in the slow theta-domain (r2 = 0.91 and r2 = 0.98 respectively) of the EEG. The changes in MAP closely correlated with an increase in the fast alpha-band a decrease in the slow theta-domain (r2 = 0.98 and r2 = 0.73 respectively). Also there was little correlation of SEF with HF and MAP changes (r2 = 0.09 and r2 = 0.02 respectively). Among the EEG-spectra, reduction of power in the slow delta- and theta-bands are the most sensitive parameters to determine insufficient antinociception of opioids commonly used for the induction in cardiac anesthesia. Increase of power in the alpha-band seems to be closely correlated with cortical reactivation and reduction of hypnosis, while a reduction of power especially in the deltabut more so in the theta-band of the EEG reflects nociception related arousal.

No inhibition of gastro-intestinal propulsion after propofol- or propofol/ketamine-N2O/O2 anaesthesia. A comparison of gastro-caecal transit after isoflurane anaesthesia

BACKGROUND

Gastrointestinal motility may be considerably reduced by anaesthesia and or surgery resulting in postoperative ileus. Inhibition of propulsive gut motility is especially marked after an opioid-based technique. Little, however, is known of the gastrointestinal effects of the hypnotic propofol when given continuously over a longer period of time, which is the case in total intravenous anaesthesia (TIVA) and in intensive care sedation. We therefore set out to study the effects of a propofol-based nitrous oxide/oxygen anaesthesia (group PO) on gastro-caecal transit time. The results were compared with a propofol-ketamine technique (group PK) and an isoflurane-based anaesthesia (group I; each group n = 20).

METHODS

Gastro-caecal transit was determined by measurement of endexpiratory hydrogen concentration (ppm). Following gastral installation of lactulose at the end of the operation, the disaccharide was degraded by bacteria in the caecum, resulting in the liberation of hydrogen which was expired. A 100% increase in endexpiratory hydrogen concentration compared to the preinduction period was considered the end-point of gastro-caecal transit.

RESULTS

There was no significant difference with regard to gastro-caecal transit in the three groups of patients. In the propofol group mean gastro-caecal transit was 119 (+/- 50.6 SD) min, in the propofol-ketamine group it was 147 (+/- 57.4 SD) min, and in the isoflurane group transit time was 122 (+/- 48.6 SD) min.

CONCLUSION

The data suggest that propofol, even when given as a continuous infusion, does not alter gastrointestinal tract motility more than a standard isoflurane anaesthesia. The data may be particularly relevant to patients who are likely to develop postoperative ileus. They also suggest that in an ICU setting propofol does not alter gut motility more than a sedation technique with the analgesic ketamine.

Preoperative adjuvant epidural tramadol: the effect of different doses on postoperative analgesia and pain processing

BACKGROUND

Tramadol is an analgesic with combined opioid agonist and monoamine reuptake blocker properties, which may be useful as a perioperative analgesic and antinociceptive adjuvant.

METHODS

The dose-dependent effects of adjuvant preoperative epidural tramadol on postoperative analgesia (pain scores and patient-controlled analgesia (PCA) use) and pain processing (heat pain thresholds) were prospectively studied in a double-blind, randomised, placebo-controlled 5-day trial. Forty patients undergoing knee or hip surgery received anaesthesia with epidural lidocaine and epidural tramadol 20, 50 or 100 mg or placebo as a preoperative adjuvant. Postoperative analgesia was by intravenous PCA tramadol in all patients.

RESULTS

Postoperative pain scores were similar in all groups. The time to first PCA use was shorter, the total dose and duration of PCA use greater, and side-effects more common with 20 mg tramadol than with 100 mg or placebo (P < 0.05). There were no differences in PCA doses required or side-effects between the tramadol 100 mg and placebo treatment groups. Heat pain tolerance thresholds were increased with 100 mg tramadol at 48 h postoperatively compared to baseline and placebo (P = 0.01).

CONCLUSIONS

Preoperative adjuvant epidural tramadol does not improve postoperative analgesia after lidocaine epidural anaesthesia compared to placebo. Tramadol 20 mg results in anti-analgesia and increased side-effects. While tramadol 100 mg depresses postoperative pain-processing, as measured by heat pain tolerance thresholds, this is not reflected in improved clinical pain measures.

Sensory changes and pain after abdominal hysterectomy: a comparison of anesthetic supplementation with fentanyl versus magnesium or ketamine

Drugs interacting with opioid or N-methyl-D-aspartate (NMDA) receptors may have differing effects on post-surgical sensory changes, such as central inhibition or spinal excitation. We compared the effect of supplementing isoflurane/N2O/O2 anesthesia with an opioid agonist (fentanyl [n = 15]) or two drugs inhibiting the NMDA system differently (magnesium, ketamine [n = 15 in each group]) on sensory changes after abdominal hysterectomy. Electric sensation, pain detection, and pain tolerance thresholds were determined (preoperatively and 1, 4, 24 h, and 5 days postoperatively) in arm, thoracic, incision, and leg dermatomes together with pain scores and cumulative morphine consumption. Thresholds relative to the arm were derived to unmask segmental sensory changes hidden by generalized changes. Absolute thresholds were increased 1-24 h, returning to baseline on Day 5, without overall differences among drugs. Fentanyl thresholds were lower 1 h and higher 5 days postoperatively compared with magnesium and ketamine; thresholds were lower at 24 h for magnesium versus ketamine. Relative thresholds increased compared with baseline only with fentanyl (1-4 h); none decreased. Pain scores and morphine consumption were similar. Thus, all adjuvants suppressed spinal sensitization after surgery. Fentanyl showed the most, and magnesium the least, central sensory inhibition up to 5 days postoperatively, with different patterns of inhibition directly postsurgery versus later. Differences in sensory processing were not reflected in clinical measures.

IMPLICATIONS

We studied the effects on postsurgical sensory processing of general anesthesia supplemented by drugs affecting opioid or N-methyl-D-aspartate receptors using sensory thresholds. Generalized central sensory inhibition, differently affected by the drugs, predominated after surgery. All drugs suppressed spinal excitation. Clinical pain measures did not reflect sensory change.

Perioperative magnesium infusion and postoperative pain

BACKGROUND

NMDA receptor activation is considered one of the mechanisms involved in postoperative pain and hypersensitivity. Magnesium is the physiological blocker of the NMDA-receptor-complex-associated calcium ionophore. The aim of this study was to determine if a pre-, intra- and postoperative infusion of magnesium would reduce postoperative pain.

METHODS

In a prospective, randomised, double-blinded and placebo-controlled study, 24 patients undergoing elective hysterectomy in standardised general anaesthesia received a 5 h infusion of either placebo or magnesium laevulinate (initial bolus 8 mmol: then 8 mmol/h) starting with induction of anaesthesia. Postoperative analgesia was by PCA morphine for the first 48 h and patients were followed for 5 d with regular assessment of pain and side-effect scores.

RESULTS

Overall, pain scores were similar with magnesium and placebo infusion, although patients in the magnesium group experienced more episodes of severe or unbearable pain (placebo = 6%, magnesium = 16%, P = 0.02). Median pain scores were higher in the magnesium group only at 3 h postoperatively (P = 0.04): afterwards there were no significant differences. Except for the first postoperative hour (placebo = 12.8 +/- 4.7 mg, magnesium = 9.3 +/- 3.2 mg, P = 0.04), cumulative morphine consumption was similar. Gastrointestinal complication rates and patient satisfaction were similar in both groups.

CONCLUSIONS

Perioperative magnesium infusion does not improve postoperative analgesia. At the doses used in this study, the use of magnesium is associated with short-term decreases in postoperative analgesia.

Postoperative nausea and vomiting: a comparative survey of the attitudes, perceptions, and practice of Swiss anesthesiologists and surgeons

Managing postoperative nausea and vomiting (PONV) depends on awareness of the problem, the therapeutic measures available, and effective implementation control systems. We mailed 616 PONV questionnaires to all 129 Swiss hospitals with anesthesiological and surgical departments. The responses [192 (31%) completed questionnaires from 87 (67%) hospitals] are representative of Swiss hospital anesthesiologists and surgeons. Anesthesiologists' perceptions of PONV are closer to those found in the literature than surgeons'. More than three quarters of anesthesiologists and less than half of surgeons practice PONV prophylaxis. Half of the respondents are dissatisfied with present antiemetics. Anesthesiologists worry about the cost of PONV prophylaxis, and surgeons are concerned about their lack of theoretical knowledge. Formal PONV policies are rare, with little consensus on treatment responsibilities. Sixty percent of respondents document PONV occurrence, and less than 20% perform any formal PONV audit. This survey identifies factors amenable to improvement regarding PONV management in Swiss hospitals. PONV education is a necessity, particularly for surgeons. Cost needs to be addressed with anesthesiologists. The limited therapeutic efficacy of antiemetics is a concern. PONV management needs standardization, organization, consensus, and research. Better audits and visibility in patients' charts could further improve the quality of PONV management.

Jugular venous bulb oxygen saturation monitoring in arteriovenous malformation surgery

We describe a case in which jugular venous bulb oxygen saturation (SjvO2) monitoring proved useful during the surgical resection of an intracranial arteriovenous malformation (AVM). Surgical resection of large intracranial AVMs may be followed by normal perfusion pressure breakthrough with brain swelling, hyperemia, and subsequent problems in achieving hemostasis. SjvO2 monitoring during AVM embolization by interventional radiology has been shown to help in deciding whether embolization is sufficient to avoid such postresection hyperemia, but its use during surgical resection has not been described. In the case discussed, SjvO2 monitoring enabled assessment of the risk of postresection hyperemia preoperatively and permitted the degree and completeness of surgical AVM resection to be followed intraoperatively. During the normal perfusion pressure breakthrough bleeding which followed complete AVM resection, SjvO2 monitoring helped with safe management of the controlled hypotension that finally permitted hemostasis to be achieved.

Surgical pain is followed not only by spinal sensitization but also by supraspinal antinociception

Nociception can produce segmental spinal sensitization or descending supraspinal antinociception. We assessed both types of sensory change after surgery during isoflurane-nitrous oxide anaesthesia with or without fentanyl before nociception. Patients undergoing back surgery received fentanyl 3 micrograms kg-1 (n = 15) or placebo (n = 15) before anaesthesia in a prospective, randomized, blinded study. Sensation, pain detection and tolerance thresholds to electrical stimulation were measured before operation at the arm, incision and herniated disc dermatomes (HDD) and 1, 2, 4, 6, 24 h and 5 days after operation, together with pain scores and patient-controlled morphine consumption (duration 24 h). For segmental effects, thresholds were normalized to the thresholds at a distant dermatome (arm). Raw pain thresholds were increased after operation (fentanyl > placebo) and were maximal at 4 h (pain tolerance in HDD: fentanyl +5.2 mA (+62.7%), placebo, +3.8 mA (+44.2%); P < 0.05 vs baseline for both). Normalized sensation thresholds decreased for placebo only (HDD/4 h: placebo, -1.8 (-44.8%), P < 0.05; fentanyl, +0.1 (+5.5%) ns). All changes returned to baseline by 24 h except for the placebo group normalized HDD sensation (d5: placebo, -2.4 (-59.7)%, P < 0.05; fentanyl -0.1 (-5.5%) ns). Pain scores and morphine consumption were similar. The study demonstrated both supraspinal analgesia and spinal sensitization after surgery. Fentanyl administration before operation augmented the former while decreasing the latter, and hence sensitization, especially if neuropathic, may particularly benefit from pre-emptive analgesia.

Doxacurium pharmacodynamics in children during volatile and opioid-based anaesthesia

The interaction between doxacurium and halothane, isoflurane or alfentanil has not been studied in children. Using the cumulative dose-response technique and electromyography, we determined ED50 and ED90 of doxacurium during halothane (n = 9), isoflurane (n = 12) or alfentanil (n = 9) based anaesthesia in children aged 2-10 years. Both isoflurane and halothane potentiated the effects of doxacurium compared to alfentanil. The ED50 for doxacurium/halothane was 23.9 micrograms.kg-1 compared to 32.7 micrograms.kg-1 for doxacurium/alfentanil. The ED90 for doxacurium/isoflurane was 32.7 micrograms.kg-1 compared to 48.2 micrograms.kg-1 doxacurium/alfentanil (p < 0.05). There were no significant time course differences between the groups. When equipotent doses of doxacurium were used to provide muscle relaxation the duration of the neuromuscular block was similar in children who received aflentanil, halothane or isoflurane supplementation of N2O/O2 anaesthesia.

[Pre-emptive analgesia]

Pre-emptive analgesia is based on the idea that analgesia initiated before a nociceptive event will be more effective than analgesia commenced afterwards, and that its effects will outlast the pharmacological duration of action of the analgesic used. The idea of pre-emptive analgesia is based upon experimental neurophysiological work demonstrating that afferent nociceptive impulses result in alterations of central nervous system function. These changes, most easily elicited by C-fibre afferents, particularly affect the spinal dorsal horn. Termed central sensitisation, they are reflected by reduced pain thresholds (allodynia), increased responses to pain (hyperalgesia), after-discharging or spontaneous activity of dorsal horn neurons (wind-up), and extension of hypersensitivity to unaffected tissues (secondary hyperalgesia). Their biochemical basis is now being unravelled, with excitatory amino acid (e.g. NMDA) and neuropeptide (e.g. substance P) neurotransmitters playing prominent roles. Blockade of these receptors has recently been shown to depress the central sensitisation associated with nociception. Ketamine, a non-competitive NMDA receptor blocker, for example, has been shown modulate postoperative pain in a positive way. Although the existence of central sensitisation is now being clinically demonstrated, studies of pre-emptive analgesia in the surgical context have not revealed clinically significant effects. This is probably because surgical nociception is much longer-lasting, multimodal and intense than its experimental counterparts. Clinical studies have so far only used short-term analgesia. To permit extrapolation from the experimental to the clinical situation, pre-emption in the surgical context must correspond adequately to the duration and extent of the nociception involved. Studies of pre-emptive analgesia in a clinically relevant form, i.e. where nociception and analgesia are correctly matched, are called for.

EEG arousal during laryngoscopy and intubation: comparison of thiopentone or propofol supplemented with nitrous oxide

We studied EEG arousal after laryngoscopy and intubation with standardized bolus induction of anaesthesia. Twenty patients were prospectively allocated randomly to induction with propofol 3 mg kg-1 (n = 10) or thiopentone (6 mg kg-1 (n = 10) and 50% nitrous oxide in oxygen. Neuromuscular block was produced with vecuronium 0.2 mg kg-1 given 30 s after induction. Three minutes after induction, laryngoscopy was performed for 60 s, with intubation at 3 min 30 s, and study end at 5 min. Nociception to laryngoscopy and intubation was followed by loss of low (relative delta activity change: thiopentone -30%, propofol -7%; P < 0.05) and a shift to higher frequency EEG activity (beta activity change: thiopentone +647%, propofol +61%; P < 0.05). This EEG arousal was greater in the thiopentone group, despite the fact that EEG depression was similar to that produced by propofol before laryngoscopy and intubation. Propofol and thiopentone in combination with nitrous oxide had similar cortical depressant effects, but propofol appeared to depress subcortical nociceptive processing more than thiopentone. While the degree of cortical EEG depression seems less useful for predicting reaction to subsequent nociception, EEG arousal reactions may prove suitable for monitoring intra-anaesthetic nociception and its modulation.

Pharmacokinetics of pipecuronium in infants, children and adults

In order to explain the reported shorter clinical duration of action of cumulative ED95 of pipecuronium in infants as compared to children or adults, the pharmacokinetic profiles of pipecuronium were compared in infants (n = 6; mean age 6.8 months; mean weight 7.3 kg) in children (n = 6; mean age 4.6 years; mean weight 19.2 kg) and in adults (n = 7; mean age 42 years; mean weight 58.2 kg). Equipotent doses (2 x ED95) of pipecuronium were injected i.v. as single bolus and arterial blood was sampled for 4-5 h. Pipecuronium was quantified by complex formation with [125I]-labelled rose bengal. Pharmacokinetic parameters were calculated using a two-compartment open model. The median for the distribution half-life of pipecuronium was 2.54 min (interquartile range: 1.0-2.5 min) in infants and 2.04 min (0.26-2.04 min) in children; both were significantly shorter than in adults (5.75 [3.7-9.7] min). The plasma clearance of pipecuronium was significantly decreased in infants (1.50 [0.6-1.5] ml.min-1.kg-1; P < 0.05) as compared to children and adults (2.27 [0.88-2.27] and 2.45 [1.7-3.2] ml.min-1.kg-1, respectively). The total volume of distribution was similar in all three groups. We conclude that the pharmacokinetic features of pipecuronium are age-dependent: differences as compared to adults consisted of a faster distribution in both infants and children and a slower elimination in infants. The pharmacokinetic profile of pipecuronium does not explain the faster recovery from neuromuscular blockade in infants as compared to children. Because of the low total plasma clearance in infants, pipecuronium dosage should be carefully monitored to avoid accumulation and prolonged paralysis.

Interaction of magnesium sulphate with vecuronium-induced neuromuscular block

We have investigated the interaction between magnesium sulphate 40 mg kg-1 i.v. and vecuronium. First, we determined the effect of pretreatment with magnesium on the potency of vecuronium using a single bolus dose-response technique. In addition, we compared the time course of vecuronium-induced neuromuscular block (vecuronium 100 micrograms kg-1) with and without magnesium pretreatment. For both parts, neuromuscular block was assessed by electromyography. In addition, the effect of magnesium pretreatment on vecuronium-induced neuromuscular block was investigated in the context of rapid sequence induction of anaesthesia. We found that the neuromuscular potency of vecuronium was increased by pretreatment with magnesium sulphate. The ED50 and ED90 of vecuronium with MgSO4 were 25% lower than without MgSO4 (ED50: 21.3 vs 26.9 micrograms kg-1; ED90: 34.2 vs 45.7 micrograms kg-1; P < 0.05 for both). Mean onset time was 147.3 (SD 22.2) s in the MgSO4-vecuronium group vs 297.3 (122) s for controls (P < 0.05). Clinical duration was prolonged (MgSO4-vecuronium 43.3 (9) min vs 25.2 (5.1) min for controls; P < 0.05). This was also true for the recovery index (20.1 (6.6) min vs 10.6 (3.4) min; P < 0.05) and duration to 75% recovery (63.4 (9.9) min vs 35.8 (6.9) min; P < 0.05). In the context of rapid sequence induction, pretreatment with MgSO4 improved the intubating score of vecuronium compared with vecuronium without MgSO4, reaching the same quality as that with suxamethonium 1 mg kg-1. We conclude that magnesium pretreatment increased the neuromuscular potency of vecuronium, in addition to modifying the time course of its neuromuscular block.

Sedation with intravenous infusions of propofol or thiopentone. Effects on pain perception

The aim of this study was to investigate pain perception during thiopentone or propofol infusions for sedation. Thirty ASA 1 or 2 patients received a two step infusion of either thiopentone (step 1: 1.25 mg.kg-1 followed by 2.5 mg.kg-1.h-1; step 2: 1.25 mg.kg-1 and 12.5 mg.kg-1.h-1; n = 15) or propofol (step 1: 0.5 mg.kg-1, 1 mg.kg-1.h-1; step 2: 0.5 mg.kg-1, 5 mg.kg-1.h-1; n = 15) for sedation. At control and 10 min after the start of each infusion dosage, reaction times and thermal pain detection thresholds were determined. We found no clinically or statistically significant depression of thermal pain detection thresholds during propofol or thiopentone infusions and these are, therefore, unlikely to be associated with clinically relevant hyperalgesia.

Total intravenous anesthesia is best for neurological surgery

We believe that today balanced TIVA represents the best anesthetic technique for neurological surgery. Freely acknowledging that this point of view is unproven (36) with regard to the hard criterion of patient outcome on leaving the hospital, we submit that the intermediate or surrogate criteria discussed make a convincing case for preferring TIVA to volatile-based anesthetic techniques. Until a study demonstrating hard outcome differences between the two techniques is achieved, we will continue to encourage the use of TIVA in neuroanesthesia, based on its practical (anesthetic depth, neuromonitoring, surgical field) and theoretical (homeostasis, metabolism, antinociception, neuroprotection) advantages.

Epidural droperidol reduces the side effects and duration of analgesia of epidural sufentanil

The postoperative combination of epidural sufentanil and epidural droperidol was assessed in 40 patients with hip or knee arthroplasties. Patients were given a single intravenous (i.v.) bolus of sufentanil 50 micrograms with either droperidol 2.5 mg or placebo (0.9% NaCl) epidurally in a double-blind, randomized design at the first request for postoperative analgesia. Pain scores, side effects, and sufentanil plasma concentrations were regularly assessed for 5 h after injection. Heat pain thresholds were measured pre- and postoperatively. The incidence of nausea, emesis, and pruritus associated with epidural sufentanil was decreased by epidural droperidol (P < 0.01, P < 0.001, P < 0.05, respectively). More patients were sedated with epidural droperidol than with placebo (P < 0.02). The initial reduction in pain scores was similarly profound, but the duration of analgesia after sufentanil and droperidol was significantly shorter than after sufentanil and placebo (P < 0.02). Phasic and tonic heat pain thresholds were increased postoperatively 1 h after sufentanil and placebo (P < 0.01 and P < 0.0005, respectively). Only the tonic heat pain thresholds were increased 1 h after sufentanil and droperidol (P < 0.002). The addition of epidural droperidol significantly reduced the excitatory side effects of epidural sufentanil while diminishing the duration of analgesia. These interactions may be of clinical significance in reducing the toxicity of opioids, but the effect on duration of analgesia must be considered when repeated doses of opioids are prescribed.

Epidural-morphine-induced pruritus: propofol versus naloxone

In a prospective, randomized, double-blind clinical trial, we compared the efficacy of propofol and naloxone for the treatment of spinal-morphine-induced pruritus. Forty patients presenting with severe pruritus within 24 h of epidural morphine administration were allocated to receive either propofol 10 mg intravenously (i.v.) or naloxone 2 micrograms/kg. In the absence of a positive response, a second dose of the same treatment was given 5 min later. Pruritus and the level of post-operative pain were assessed every 5 min up to the end of the study period (45 min) using a verbal rating scale. The overall success rate in treating pruritus was similar in the two groups (80%). The rate of success after the first injection of the treatment drug was also similar (55%). The level of postoperative pain decreased after drug treatment in six patients (30%) in the propofol group versus none in the naloxone group (P < 0.05). Forty-five percent of the patients in the naloxone group had an increase in the level of postoperative pain versus none in the propofol group (P < 0.05). In conclusion, these results suggest that propofol and naloxone are equally effective in treating spinal-morphine-induced pruritus. However, the level of postoperative pain is significantly less in the propofol group.

[Pruritus associated with liver disease: propofol, a new therapeutic approach?]

Pruritus is a severe and troublesome symptom in patients with cholestasis and is often difficult to treat. Propofol was recently shown to be efficient in the treatment of pruritus secondary to spinal morphine administration. In a prospective, randomized, double-blind, cross-over and placebo controlled study, 20 patients received 1 dose of propofol (15 mg) and 1 dose of Intralipid (1.5 mg) during a 2-day study period. Pruritus was assessed by a visual analogue scale from 0 (no pruritus) to 10 (most severe pruritus imaginable). Treatment success was defined as a decrease in pruritus of at least 4 points on the scale in 80% of the patients receiving propofol and in 15% of those receiving intralipid (p < 0.05). Discomfort on injection was observed in 15% under propofol treatment. In conclusion this study shows that subhypnotic doses of propofol are effective for the short-term symptomatic relief of pruritus associated with liver disease. At the dose administered, side effects were rare and minor.

Propofol in the management of refractory status epilepticus: a case report

Status epilepticus is one of the most frequent neurological emergencies in the intensive care unit. Standard treatment includes intravenous barbiturates, benzodiazepines and phenytoin. However, drug coma is sometimes necessary to control refractory status epilepticus. We report such a case, successfully treated by intravenous propofol coma to EEG burst suppression.

Propofol improves patient comfort during cisplatin chemotherapy. A pilot study

20 consecutive patients with nausea and vomiting secondary to cisplatin chemotherapy uncontrolled by serotonin-antagonist and corticosteroid prophylaxis during their first cycle received adjuvant propofol. This new anesthetic agent was added at subhypnotic doses, i.e. 1 mg/kg/h, as a continuous intravenous infusion during the two subsequent chemotherapy cycles. In 85 and 90% of patients, nausea and vomiting were prevented in the first 24 h following the first and second propofol-supplemented chemotherapy cycles respectively. 24-72 h postchemotherapy, this side effect remained suppressed in 75 and 70% of patients, respectively. Patients' comfort and appetite were improved. All 20 subjects preferred the propofol-containing regimen.

Urinary serotonin metabolite excretion during cisplatin chemotherapy

BACKGROUND

Nausea and vomiting associated with cisplatin chemotherapy is a source of major morbidity that remains difficult to control. Acute phase (0-24 hours after induction of chemotherapy) nausea and vomiting parallels plasma serotonin release, which explains the effectiveness of 5HT3 antagonists; serotonin release in the delayed phase (24-48 hours after induction), during which consistent antiemetic control remains elusive, has not been investigated. The effect of propofol, a recent addition to the antiemetic armamentarium, on this serotonin release has not been studied.

METHODS

Ten women with nausea and vomiting refractory to ondansetron and dexamethasone prophylaxis in their first cisplatin chemotherapy cycle were studied. Serial urinary 5-hydroxyindoleacetic acid (5-HIAA) levels were determined during a 48-hour period in 30 subsequent cycles, conducted under ondansetron/dexamethasone prophylaxis together with a propofol infusion.

RESULTS

There was a significant urinary 5-HIAA peak 6 hours after induction of chemotherapy, with no peaks thereafter. Propofol did not inhibit serotonin release.

CONCLUSIONS

Cisplatin chemotherapy is associated with serotonin release in the acute phase. There is no serotonin release during the delayed phase. Thus the use of 5HT3 antagonists for delayed-phase nausea and vomiting would appear questionable.

Spontaneous excitatory movements during recovery from propofol anaesthesia in an infant: EEG evaluation

Spontaneous excitatory movements have been observed during recovery from propofol anaesthesia in children. Epilepsy has been postulated as a possible mechanism to explain these movements. We report the first case in which these spontaneous excitatory movements were studied using simultaneous multichannel EEG recordings.

Subhypnotic doses of propofol relieve pruritus associated with liver disease

BACKGROUND

Pruritus is a severe and troublesome symptom in patients with cholestasis and is often difficult to treat. Propofol was recently shown to be efficient in relieving pruritus secondary to spinal morphine administration. The efficacy of propofol was therefore investigated in patients with pruritus associated with liver disease.

METHODS

In a prospective, randomized, double-blind, crossover, placebo-controlled study, 10 patients received 2 doses of propofol (1.5 mL = 15 mg) and 2 doses of placebo (1.5 mL of Intralipid, Kabi-Pharm., Helsinki, Finland) during a 4-day study period. Pruritus was assessed by a verbal rating score from 0 (no pruritus) to 10 (most severe pruritus imaginable). Treatment success was defined as a decrease of pruritus of at least 4 points in the verbal rating score.

RESULTS

Treatment success was achieved in 85% of the patients receiving propofol and in 10% of those receiving Intralipid (P < 0.01). Discomfort on injection (15%) and slight dizziness (10%) were observed with propofol treatment.

CONCLUSIONS

This study shows that subhypnotic doses of propofol are effective for the short-term symptomatic relief of pruritus associated with liver disease. At the dose used, side effects were rare and minor.

Subhypnotic doses of propofol possess direct antiemetic properties

Propofol is associated with a low incidence of postoperative nausea and vomiting. In a prospective, randomized, double-blind, placebo-controlled study, we investigated the possible direct antiemetic properties of a subhypnotic dose of propofol. Fifty-two ASA physical status I or II patients, aged 15-60 yr with nausea and vomiting after minor gynecologic, orthopedic, or digestive tract surgery, were included in the study and received either propofol (10 mg = 1 mL) or placebo (1 mL Intralipid) intravenously in the postanesthesia care unit. Patients treated with propofol experienced a larger reduction in nausea and vomiting than patients treated with placebo (81% vs 35% success rate; P less than 0.05). Patients successfully treated had a similar incidence of relapse (propofol 28%; placebo 22%) within the first 30 min after therapy. Thirty-three percent of the propofol-treated patients and 44% of the placebo-treated patients showed a minor increase in sedation. The level of postoperative pain did not change in either group. Hemodynamic values remained unchanged in both groups. Pain on injection (7.6%) or dizziness (3.6%) only occurred in the propofol group. We conclude that propofol has significant direct antiemetic properties.

Subhypnotic doses of propofol relieve pruritus induced by epidural and intrathecal morphine

We investigated the efficacy of subhypnotic doses of propofol for spinal morphine-induced pruritus in a prospective, randomized, double-blind, placebo-controlled study. Fifty patients, ASA physical status 1-3, with spinal morphine-induced pruritus were allocated to receive either 1 ml propofol (10 mg) or 1 ml placebo (Intralipid) intravenously after gynecologic, orthopedic, thoracic, or gastrointestinal surgery. In the absence of a positive response, a second drug treatment was given 5 min later. The persistence of pruritus 5 min after the second treatment dose was considered a treatment failure. All failures then received, in an open fashion, a supplementary dose of propofol (10 mg) and were reevaluated 5 min later. Both groups were well matched. The success rate was significantly greater in the propofol group (84%) than in the placebo (16%) group (P less than 0.05). Ninety percent of the treatment failures in the placebo group were successfully treated by a supplementary dose of 10 mg propofol. Eight percent of the patients (4% in each group) were resistant to all treatments, including naloxone 0.08 mg intravenously. Three patients had a slight increase in sedation in the propofol group versus none in control (not significant). The beneficial effect of treatment was longer than 60 min in 85% of patients in the propofol group and in 100% of the controls (not significant). These results suggest that propofol in a subhypnotic dose is an efficient drug treatment for spinal morphine-induced pruritus. At the dose administered (10 mg), side effects were rare and minor.

Echocardiographic assessment of the haemodynamic effects of propofol: a comparison with etomidate and thiopentone

The haemodynamic effects of propofol (2 mg/kg), etomidate (0.2 mg/kg) and thiopentone (4 mg/kg) were studied in 30 ASA 1 and 2 patients in whom anaesthesia had been induced with midazolam 0.1 mg/kg, fentanyl 5 micrograms/kg, vecuronium 0.1 mg/kg and atropine 10 micrograms/kg, and maintained with nitrous oxide in oxygen. Arterial pressure was measured directly and left ventricular diameters were determined by transoesophageal echocardiography. Systolic blood pressure after propofol and thiopentone and the end-systolic quotient (systolic pressure/end-systolic diameter), a measure of inotropy, decreased. Fractional shortening (end-diastolic-end-systolic diameter/end-diastolic diameter) decreased only in the thiopentone group. Diastolic blood pressure and end-diastolic diameter (a measure of preload) did not change in any of the groups, and the etomidate group showed no changes in the haemodynamic variables measured. Propofol shows simultaneous negative inotropy and afterload reduction, while thiopentone is exclusively negatively inotropic.