The analgesic properties of scalp infiltrations with ropivacaine after intracranial tumoral resection.

BACKGROUND: The issue of postoperative pain after neurosurgery is controversial. It has been reported as mild to moderate and its treatment may be inadequate. Infiltration of the surgical site with local anesthetics has provided transient benefit after craniotomy, but its effect on chronic pain has not been evaluated. Accordingly, we designed the present study to test the hypothesis that ropivacaine infiltration of the scalp reduces acute and persistent postoperative pain after intracranial tumor resection. METHODS: This was a prospective, single-blinded study. Inclusion criteria were intracranial tumor resection, age > or = 18 or < or = 80 yr, and ability to understand and use a visual analog scale (VAS). Exclusion criteria were history of craniotomy, chronic drug abuse, and neurologic disorders. All eligible patients were randomly included in Group I (infiltration) or C (control). Postoperative analgesia was IV acetaminophen combined with nalbuphine. At the end of the surgery, Group I received an infiltration of the surgical site with 20 mL of ropivacaine 0.75%. Acute pain was evaluated hourly by VAS during the first 24 h. The analgesic effect of ropivacaine was evaluated based on total consumption of nalbuphine and VAS scores. The incidence of persistent pain and neuropathic pain was assessed at the 2-mo postoperative evaluation. We used the Student's t-test to compare total nalbuphine consumption, repeated measures analysis of variance with post hoc Bonferroni t-test for VAS score and the Fisher's exact test for chronic and neuropathic pain. RESULTS: Fifty-two patients were enrolled, 25 in Group I and 27 in Group C. Demographic and intraoperative data were similar between groups. Group I showed a nonsignificant trend toward reduced nalbuphine consumption during the first postoperative day, 11.2 +/- 9.2 mg vs 16.6 +/- 11.0 mg for Group C (mean +/- SD, P = 0.054). VAS scores were significantly higher in Group C. Two months after surgery, persistent pain was significantly lower in Group I, 2/24 (8%) vs 14/25 (56%), P = 0.0003. One patient (4.1%) in Group I versus six (25%) patients in Group C (P = 0.04) experienced neuropathic pain. CONCLUSIONS: Because pain is moderate after intracranial tumor resection, there is limited interest in scalp infiltrations with ropivacaine in the acute postoperative period. Nevertheless, these infiltrations may be relevant for the rehabilitation of neurosurgical patients and their quality of life by limiting the development of persistent pain and particularly neuropathic pain.

Median effective infusion dose (ED50) of alfentanil for monitored anesthesia care of percutaneous vertebroplasty of osteoporotic fractures.

UNLABELLED: Percutaneous vertebroplasty (PVP) consists of injecting small quantities of orthopedic cement to consolidate pathologic vertebral bodies. The procedure is brief but painful during vertebral puncture and cement injection requiring either general anesthesia or monitored anesthesia care with opioids. The optimal dose of alfentanil in this setting is unknown. Therefore, we sought to determine its median effective dose (ED50, or analgesic efficacy in 50% of patients) during PVP in none intubated, spontaneously breathing patients. After approval and informed consent of the Institutional Review Board, 50 patients (American Society of Anesthesiologists II-III, age 50 to 80, weight: 53 to 82 kg) with osteoporotic vertebral fractures were enrolled. The patients were premedicated with oral hydroxyzine 100 mg and had skin infiltration with 50 mg lidocaine before vertebral puncture. The prone position was adopted and oxygen was provided via a facemask. Noninvasive cardiorespiratory variables were monitored. Pain was evaluated by a numerical pain scale (NPS) where 0 represents no pain and 10 the worst tolerable pain. Alfentanil infusion was started 30 minutes before vertebral puncture. The initial dose was 2.0 mg/h. Thereafter, a 0.05 mg/h decrease or increase was applied to the next patient if analgesia was effective (NPS: 3 or less) or not (NPS>3) according to the Dixon method. The bootstrap resampling technique was used to calculate the ED50 and its 95% confidence limits. The latter was 1.05 mg/h (95% confidence interval, 1.0-1.2). Transient apnea (n=2) and nausea/vomiting (n=3) were observed. Given the median body weight of the patients (65 kg), we conclude that 0.27 microg kg/min of alfentanil provides effective analgesia for PVP under monitored anesthesia care. SUMMARY STATEMENT: PVP consists of injecting small quantities of orthopedic cement to consolidate pathologic vertebral bodies. The median effective dose (ED50) for pain relief during vertebral puncture and cement injection is 1.05 (95% confidence interval, 1.0-1.2) mg/h when infusion is started 30 minutes before the procedure. Given the median body weight of our study population (65 kg), this dose corresponds to 0.27 microg kg/min.

Effects of sevoflurane on carrageenan- and fentanyl-induced pain hypersensitivity in Sprague-Dawley rats.

PURPOSE: Opioids are widely used for anesthesia but paradoxically induce postoperative pain hypersensitivity via N-methyl-D: -aspartate (NMDA) receptor modulation. Sevoflurane effects on opioid-induced hyperalgesia have not been yet evaluated in vivo. Nevertheless, some experimental in vitro studies reported anti-NMDA receptor properties for sevoflurane. The aim of this study was to evaluate sevoflurane effects on fentanyl-induced hyperalgesia in opioid-naive rats and in rats with inflammatory pain. METHODS: Sevoflurane effects on hyperalgesia were evaluated in Sprague-Dawley rats: opioid-naive rats, rats treated with fentanyl (4 x 60 microg kg(-1)) and rats with inflammatory pain (carrageenan) treated with fentanyl (4 x 60 microg kg(-1)). On day zero, subcutaneous fentanyl injections were administered and inflammatory pain was induced with one carrageenan injection in one hind paw. Rats were exposed to low concentrations of sevoflurane (1.0 or 1.5%) on day zero prior to fentanyl injections and inflammatory pain induction, and for the duration of the fentanyl analgesic effect. The nociceptive threshold (Randall-Selitto test) was evaluated daily for 7 days. On day seven, naloxone was injected and the nociceptive threshold was assessed 5 min later. RESULTS: In rats without inflammatory pain but treated with fentanyl on day zero, sevoflurane 1.0% reversed the early (day zero) and long-lasting (day zero to day three) hyperalgesia classically described after high-doses of fentanyl (P < 0.05). This sevoflurane concentration antagonized the hyperalgesia induced by naloxone on day seven (P = 0.33). In a second experiment in rats with inflammatory pain, exposure to low concentrations of sevoflurane (1.0 and 1.5%) did not reduce fentanyl-induced hyperalgesia (P > 0.05), but nevertheless antagonized the naloxone induced hyperalgesia on day seven (P = 0.061). CONCLUSION: Relatively low sevoflurane concentrations (1.0%) reverse fentanyl-induced hyperalgesia in rats without inflammatory pain. Nevertheless, the lack of effect of sevoflurane concentrations of 1.0% and 1.5% to oppose hyperalgesia following high-dose fentanyl and inflammatory pain suggests that sevoflurane anti-hyperalgesic properties are weak.

Audibility of anaesthesia alarms during magnetic resonance imaging: should we be alarmed?

BACKGROUND AND OBJECTIVE: The effects of MRI acoustic noise on anaesthesia safety concerns have not yet been documented. The objectives of this study were to provide subjective and objective evaluations of anaesthesia alarm audibility during MRI and to review the literature to determine whether or not to worry about our results. METHODS: Following Institutional Review Board's approval, we tested the audibility of four anaesthesia equipment alarms and selected one of them. Additionally, we selected the least audible of three MRI sequences (spin echo) for the study. The evaluations were conducted inside and outside the scanning room in a subjective and objective manner. First, 20 normal hearing consenting adult volunteers rated their audibility of the anaesthesia alarm using a 10-point numerical scale (0 = not audible to 10 = maximum audibility). Second, a sound level meter was used to measure the intensity of acoustic noise (A-weighted scale) under the above-mentioned conditions. Data, expressed as median [interquartile range], were analysed using the Wilcoxon test with P less than 0.05 considered as significant. RESULTS: The subjective audibility scores (inside vs. outside the MRI room) were 9.0 [8.5-10.0] vs. 7 [6.5-8.0]. During MRI scanning, the scores were 6.0 [5.5-7.0] vs. 4.0 [3.5-5.0], respectively (P < 0.001). The sound level measurements were 70 [69-71] vs. 55 [54-57] dB (A). During MRI 91 [91-92] dB (A) vs. 68 [65-69] dB (A) (P < 0.001). CONCLUSION: The audibility of the anaesthesia alarm is significantly reduced during MRI, particularly outside the scanning room. Consequently, optical alarms and interactive screens (outside the room) must be available without exception.

Real-time heart rate variability and its correlation with plasma catecholamines during laparoscopic adrenal pheochromocytoma surgery.

BACKGROUND: We studied sympathovagal activity using real-time heart rate variability (HRV) and determined its relationship with plasma catecholamines to characterize short-term cardioregulatory mechanisms during laparoscopic adrenal pheochromocytoma surgery. METHODS: We recruited 20 patients with pheochromocytoma (Group P) and 20 with incidentaloma (Group I). HRV, systolic blood pressure and heart rate were continuously monitored. The low frequency and high frequency spectra denoted, respectively, sympathetic and parasympathetic activity. The low frequency/high frequency (LF/HF) ratio represented sympathovagal balance. Blood samples for epinephrine and norepinephrine assays were collected before, during, and after surgery. After log transformation of the repeated measures, a linear regression model was applied on their mean values. The correlation coefficients among variables were calculated using the Spearman rank test. RESULTS: No significant changes were observed in Group I. In Group P, epinephrine and norepinephrine increased in all patients during peritoneal insufflation and tumor resection. In 16 patients, systolic blood pressure, heart rate, low frequency, and LF/HF ratio increased concurrently. In four patients, low frequency and LF/HF ratio decreased. Three of these patients had normal systolic blood pressure and heart rate, and the fourth patient had hypotension and tachycardia. The high frequency component was enhanced in 15 patients and was stable in five. Low frequency was correlated with norepinephrine (r = 0.68, P < 0.001), systolic blood pressure (r = 0.66, P < 0.01), and heart rate (r = 0.62, P < 0.05). CONCLUSION: This study demonstrated a strong correlation between low frequency HRV, plasma norepinephrine, arterial blood pressure, and heart rate during pheochromocytoma surgery.

Nitrous oxide revisited: evidence for potent antihyperalgesic properties.

BACKGROUND: Although opioids are unsurpassed analgesics for surgery, they also induce an N-methyl-D-aspartate-dependent enhancement of postoperative hyperalgesia. Because nitrous oxide (N2O) has anti-N-methyl-D-aspartate properties, the purpose of this study was to evaluate nitrous oxide ability to prevent such an opioid-induced hyperalgesia in rats. METHODS: First, preventive effects of 50/50% N2O-O2 on the development of delayed hyperalgesia observed after inflammatory pain (hind paw carrageenan injection on D0) were examined for several days. Second, the ability of nitrous oxide (10-40%) to limit opioid-induced hyperalgesia induced by fentanyl was evaluated in nonsuffering rats. Third, antihyperalgesic effects of various nitrous oxide concentrations (20-50%) were assessed in both inflammatory and incisional pain models in fentanyl-treated rats (4 x 100 microg/kg subcutaneously). Finally, the analgesic effect of a single dose of morphine was evaluated 24 h after fentanyl administration and nitrous oxide (D0) to assess its preventive effect on acute morphine tolerance in both nonsuffering and hind paw-incised rats. RESULTS: When applied on D0, nitrous oxide reduced delayed hyperalgesia induced by inflammation. Exposure to nitrous oxide on D0 also reduced opioid-induced hyperalgesia in nonsuffering rats in a dose-dependent manner. In fentanyl-treated rats with inflammatory or incisional pain, nitrous oxide strongly limited both magnitude and duration of hyperalgesia. Moreover, nitrous oxide exposure on D0 opposed development of acute tolerance to analgesic effects of morphine administered on D1 in both nonsuffering and incised fentanyl-treated rats. CONCLUSIONS: Nitrous oxide, an N-methyl-D-aspartate receptor antagonist, prevented the enhancement of pain sensitivity induced by both nociceptive inputs and fentanyl and opposed acute morphine tolerance. Results suggest that perioperative nitrous oxide use reduces exaggerated postoperative pain and morphine consumption.

Remifentanil-induced postoperative hyperalgesia and its prevention with small-dose ketamine.

BACKGROUND: Remifentanil-induced secondary hyperalgesia has been documented experimentally in both animals and healthy human volunteers, but never clinically. This study tested the hypotheses that increased pain sensitivity assessed by periincisional allodynia and hyperalgesia can occur after relatively large-dose intraoperative remifentanil and that small-dose ketamine prevents this hyperalgesia. METHODS: Seventy-five patients undergoing major abdominal surgery were randomly assigned to receive (1) intraoperative remifentanil at 0.05 microg x kg(-1) x min(-1) (small-dose remifentanil); (2) intraoperative remifentanil at 0.40 microg x kg(-1) x min(-1) (large-dose remifentanil); or (3) intraoperative remifentanil at 0.40 microg x kg(-1) x min(-1) and 0.5 mg/kg ketamine just after the induction, followed by an intraoperative infusion of 5 microg x kg(-1) x min(-1) until skin closure and then 2 microg x kg(-1) x min(-1) for 48 h (large-dose remifentanil-ketamine). Pain scores and morphine consumption were recorded for 48 postoperative hours. Quantitative sensory tests, peak expiratory flow measures, and cognitive tests were performed at 24 and 48 h. RESULTS: Hyperalgesia to von Frey hair stimulation adjacent to the surgical wound and morphine requirements were larger (P < 0.05) and allodynia to von Frey hair stimulation was greater (P < 0.01) in the large-dose remifentanil group compared with the other two groups, which were comparable. There were no significant differences in pain, pressure pain detection threshold with an algometer, peak flow, cognitive tests, or side effects. CONCLUSION: A relatively large dose of intraoperative remifentanil triggers postoperative secondary hyperalgesia. Remifentanil-induced hyperalgesia was prevented by small-dose ketamine, implicating an N-methyl-d-aspartate pain-facilitator process.

Clinical assessment of the laryngeal tube in pediatric anesthesia.

BACKGROUND: The aim of this study was to evaluate a new device for airway management in children: the laryngeal tube (LT). METHODS: The LT is available in sizes S0-S3 for pediatric anesthesia. This prospective open study included 70 children ASA 1. The local Ethics Committee approval and parental consent were collected. The primary criterion was the success rate for insertion and ventilation. Secondary criteria were additional maneuvers and incidents elicited from LT use. RESULTS: Seventy children were included: S0 = 5, S1 = 8, S2 = 36, and S3 = 21. Insertion was successful: at the first attempt in 78.6%, second in 17.1%, and third or more in 4.3%. In 12% of cases it was not possible to successfully insert the LT and proceed to adequate ventilation. Failures were explained by: inability to obtain satisfying ventilation (n = 4), hypoxemia (n = 1), gastric insufflation (n = 6), cough (n = 1), and laryngospasm or stridor (n = 2), some with the same child. Minimal additional maneuvers for adequate ventilation were necessary in 35% of cases (all groups), but <20% when considering only sizes 2 and 3. Moreover, after five cases, the anesthesiologists became more proficient at inserting the LT (respectively 73.3% failure before five cases vs 13% afterwards). Gastric insufflation occurred in eight cases (11.4%). Controlled ventilation was used in 30 children and peak inspiratory pressure was 19.2 +/- 4 cmH(2)O. CONCLUSIONS: The LT is not recommended for children <10 kg. Over 10 kg, it provides a clear airway in most children, with a low rate of minimal additional maneuvers for sizes 2 and 3. The failure rate also decreases with the operator's training.

Ketamine improves the management of exaggerated postoperative pain observed in perioperative fentanyl-treated rats.

BACKGROUND: Although opioids are unsurpassed analgesics, experimental and clinical studies suggest that opioids activate N-methyl-d-aspartate pronociceptive systems leading to pain hypersensitivity and short-term tolerance. Because it is difficult in humans to differentiate pain from hyperalgesia during the postoperative period, the authors performed experimental studies with fentanyl using the rat incisional pain model for evaluating relations between hyperalgesia and short-term tolerance. Because N-methyl-d-aspartate receptor antagonists oppose both pain hypersensitivity and tolerance induced by opioids, the authors examined the capability of ketamine for improving exaggerated postoperative pain management. METHODS: During halothane anesthesia, a hind paw plantar incision was performed in rats receiving four fentanyl subcutaneous injections (100 microg/kg per injection, every 15 min). In some groups, three subcutaneous ketamine injections (10 mg/kg per injection, every 5 h) were performed in saline- or fentanyl-treated rats. One day after surgery, the analgesic effect of morphine (2 mg/kg subcutaneous) was tested. Analgesia, mechanical hyperalgesia, tactile allodynia, and pain score were assessed for several days using the paw pressure vocalization test, the von Frey application test, and the postural disequilibrium test. RESULTS: Fentanyl induced analgesia but also produced exaggerated postoperative pain as indicated by the enhancement of hyperalgesia, allodynia, and weight-bearing decrease after hind paw plantar incision. Ketamine pretreatment prevented such a fentanyl-induced enhancement of postoperative pain and improved its management by morphine. CONCLUSIONS: By opposing postoperative pain hypersensitivity and subsequent short-term tolerance induced by perioperative opioid use, ketamine not only improves exaggerated postoperative pain management but also provides better postoperative rehabilitation.

[Autonomic hyperreflexia induced by sacral root stimulation is detected by spectral analysis of the EEG]. / L'hyperréflexie autonome induite par la stimulation des racines sacrées est détectée par l'analyse spectrale de l'ECG.

PURPOSE: To compare spectral analysis of the electrocardiogram (ECG) with mean arterial pressure (MAP) and heart rate (HR) monitoring in the detection of autonomic hyperreflexia (AHR) induced by sacral root stimulation. METHODS: Ten spinal cord injured patients scheduled for implantation of a sacral root stimulator for bladder retention were included. Under target controlled anesthesia with propofol 4 micro g*mL(-1) and remifentanil 4 ng*mL(-1), the patients were placed in the knee chest position. The sacral roots were exposed by laminectomy (L2-S1) and their function assessed by electrostimulation under urodynamic and cardiovascular monitoring. Online power spectrum densities were calculated from the ECG R-R interval by the MemCalc(TM) software using the maximum entropy method. Low frequency (LF: 0.04-0.15 Hz) and high frequency (HF: 0.15-0.4 Hz) spectra were associated with sympathetic and parasympathetic activities respectively. The most extreme value of each variable was noted before and during each stimulation. A difference ( triangle up ) of more than 10% signified AHR. The comparison ( triangle up LF vs triangle up MAP and triangle up HF vs triangle up HR) was done by a concordance test with a kappa coefficient (k): -1 = total discordance to 1 = total concordance. RESULTS: AHR was detected in six patients as an increase in LF and MAP (n = 4); an increase in LF, HF, MAP with a decrease in HR (n = 2). The detection delay was 5.3 +/- 1 sec (LF, HF) and 10.4 +/- 1.2 sec (MAP and HR). Concordance was 85% (LF vs MAP: k = 0.7) and 90% (HF vs HR: k = 0.8). CONCLUSION: AHR induced by sacral root stimulation is detected by spectral analysis of the ECG earlier than MAP and HR. Other studies are needed to confirm these results.

The role of ketamine in preventing fentanyl-induced hyperalgesia and subsequent acute morphine tolerance.

UNLABELLED: Perioperative opioids increase postoperative pain and morphine requirement, suggesting acute opioid tolerance. Furthermore, opioids elicit N-methyl-D-aspartate (NMDA)-dependent pain hypersensitivity. We investigated postfentanyl morphine analgesic effects and the consequences of NMDA-receptor antagonist (ketamine) pretreatment. The rat nociceptive threshold was measured by the paw-pressure vocalization test. Four fentanyl boluses (every 15 min) elicited a dose-dependent (a) increase followed by an immediate decrease of the nociceptive threshold and (b) reduction of the analgesic effect of a subsequent morphine administration (5 mg/kg): -15.8%, -46.6%, -85.1% (4 x 20, 4 x 60, 4 x 100 microg/kg of fentanyl, respectively). Ketamine pretreatment (10 mg/kg) increased the fentanyl analgesic effect (4 x 60 microg/kg), suppressed the immediate hyperalgesic phase, and restored the full effect of a subsequent morphine injection. Fentanyl also elicited a delayed dose-dependent long-lasting decrease of the nociceptive threshold (days) that was prevented by a single ketamine pretreatment before fentanyl. However, a morphine administration at the end of the fentanyl effects restored the long-lasting hyperalgesia. Repeated ketamine administrations were required to obtain a complete preventive effect. Although ketamine had no analgesic effect per se at the dose used herein, our results indicate that sustained NMDA-receptor blocking could be a fruitful therapy for improving postoperative morphine effectiveness. IMPLICATIONS: Fentanyl-induced analgesia is followed by early hyperalgesia (hours), acute tolerance to the analgesic effects of morphine, and long-lasting hyperalgesia (days). All these phenomena are totally prevented by repeated administrations of the NMDA-receptor antagonist, ketamine, simultaneously with fentanyl and morphine administration.

Postoperative pain management after supratentorial craniotomy.

The aim of this study was to compare the analgesic efficacy of three different postoperative treatments after supratentorial craniotomy. Sixty-four patients were allocated prospectively and randomly into three groups: paracetamol (the P group, n = 8), paracetamol and tramadol (the PT group, n = 29), and paracetamol and nalbuphine (the PN group, n = 27). General anesthesia was standardized with propofol and remifentanil using atracurium as the muscle relaxant. One hour before the end of surgery, all patients received 30 mg/kg propacetamol intravenously then 30 mg/kg every 6 hours. Patients in the PT group received 1.5 mg/kg tramadol 1 hour before the end of surgery. For patients in the PN group, 0.15 mg/kg nalbuphine was injected after discontinuation of remifentanil, because of its mu-antagonist effect. Postoperative pain was assessed in the fully awake patient after extubation (hour 0) and at 1, 2, 4, 8, and 24 hours using a visual analog scale (VAS). Additional tramadol (1.5 mg/kg) or 0.15 mg/kg nalbuphine was administered when the VAS score was > or = 30 mm. Analgesia was compared using the Mantha and Kaplan-Meier methods. Adverse effects of the drugs were also measured. The three groups were similar with respect to the total dose of remifentanil received (0.27 +/- 0.1 mircog/kg/min). In all patients, extubation was obtained within 6 +/- 3 minutes after remifentanil administration. Postoperative analgesia was ineffective in the P group; therefore, inclusions in this group were stopped after the eighth patient. Postoperative analgesia was effective in the two remaining groups because VAS scores were similar, except at hour 1, when nalbuphine was more effective (P = .001). Nevertheless, acquiring such a result demanded significantly more tramadol than nalbuphine (P < .05). More cases of nausea and vomiting were observed in the PT group but the difference was not significant (P < .06). In conclusion, pain after supratentorial neurosurgery must be taken into account, and paracetamol alone is insufficient in bringing relief to the patient. Addition of either tramadol or nalbuphine to paracetamol seems necessary to achieve adequate analgesia, with, nevertheless, a larger dose of tramadol to fulfill this objective.

Intraosseous lidocaine provides effective analgesia for percutaneous vertebroplasty of osteoporotic fractures.

PURPOSE: To assess the safety and efficacy of intraosseous lidocaine (IL), in comparison with iv nalbuphine and propacetamol (NP) for analgesia during percutaneous vertebroplasty (PV) in order to avoid general anesthesia in elderly patients. METHODS: Patients (age 68 +/- 13 yr, weight 66 +/- 6 kg) undergoing PV for osteoporotic fractures were randomized prospectively into two groups: NP (n=50) and IL (n=50). All patients were premedicated (oral hydroxyzine 1 mg.kg(-1)) and had skin infiltration with 5 mL of 1% lidocaine prior to vertebral puncture. Thirty minutes before the procedure, Group NP received, in a blinded manner, 50 mL of iv nalbuphine (0.3 mg.kg(-1)) and propacetamol (30 mg.kg(-1)) while Group IL received 50 mL of iv saline. During vertebral puncture, Groups NP and IL received, in a blinded manner, 1 mL.10 kg(-1) of intraosseous saline and 1% lidocaine respectively. Pain was assessed during vertebral puncture and cement injection with a four-point verbal rating scale. Additionally, lidocaine plasma kinetics were obtained in 11 IL patients. RESULTS: Analgesic efficacy was similar in the IL and NP groups (85 vs 84%). Group NP had more side effects. Lidocaine peak recorded concentration was 2.6 +/- 0.1 microg.mL(-1) i.e., about three times less than the reported toxic limits. CONCLUSION: IL is as effective as the association of iv NP for analgesia in PV. However, considering that both protocols were insufficient in about 15% of cases, other modalities are needed to further improve analgesia and avoid general anesthesia during vertebroplasty.