Jean-Louis Scholtes

Intravenous or epidural clonidine for intra- and postoperative analgesia.

Background:Intravenous and epidural clonidine both produce postoperative analgesia. Several experimental reports demonstrate a spinal site of action for the analgesic effects of this α2-adrenoceptor agonist. Therefore, the authors evaluated the clinical analgesic benefits of using clonidine, both intra- and postoperatively, by the epidural or the intravenous route. Methods:Using a randomized prospective double-blind study design, 40 patients, between 18 and 50 yr of age, undergoing intestinal surgery under general propofol/nitrous oxide anesthesia, were enrolled. Before anesthesia, an epidural catheter was inserted at the L1-L2 interspace. At induction, a clonidine infusion was started at the doses of 4 µg/kg in 10 ml during 20 min, followed by 2 µg · kg−1 · h−1 (5 ml/h) during 12 h, either by the epidural (group 1) or by the intravenous (group 2) route. Intraoperatively, increased blood pressure and heart rate not responding to additional propofol bolus (0.5 mg/kg) was treated with a bolus of alfentanil (7 µg/kg). Postoperatively, morphine boluses (1.5 mg) were given through a PCA device according to the patients need. Intraoperative analgesia was assessed by the alfentanil requirements. Postoperative analgesia was assessed by recording the morphine requirements, the visual analogue scale (VAS) at rest and after mobilization, and the patients analgesia scale at 0, 3, 6, 12, 18, 24, and 36 postoperative hours. Sedation analogue scale and side effects were also recorded. Heart rate and blood pressure were particularly detailed during the first 2 h of the clonidine infusion. Plasma clonidine concentrations were measured after 20 min and 6, 12, and 24 h. Results:Epidural clonidine significantly reduced the intraoperative alfentanil requirements (0.93 ± 1.2 in group 1 vs. 2.4 ± 1.8 mg in group 2). The postoperative morphine requirements were also reduced during the first 6 h (8.3 ± 5.8 in group 1 vs. 17.8 ± 13.4 mg in group 2). The VAS were comparable in both groups, despite the better patients analgesia score reported in the epidural group during the first 12 h. There was no difference in sedation score at any time interval considered. Epidural and intravenous clonidine reduced heart rate and blood pressure to the same extent. The plasma clonidine concentrations were less in the epidural group only after the loading doses. Conclusions:Epidural clonidine reduces the intra- and early postoperative analgesic requirements when compared with the same dose given by the intravenous route. The side effects were similar with the two routes of administration.

Epidural clonidine used as the sole analgesic agent during and after abdominal surgery : A dose-response study

BACKGROUND: Many studies have shown the beneficial effect of epidural clonidine in postoperative pain management. In these studies, the patients received local anesthetics, opioids, or both in combination with clonidine. Due to the interactive potentiation of those drugs, the importance of the intrinsic analgesic properties of the alpha 2-adrenoceptor agonist is difficult to establish. The authors investigated the analgesic potency of epidural clonidine when used as the sole analgesic agent during and after major abdominal surgery. METHODS: Fifty young adult patients undergoing intestinal surgery under general anesthesia with propofol were studied. At induction, the patients received epidurally either an initial dose of 2 micrograms/kg clonidine followed by an infusion of 0.5 microgram.kg-1.h-1 (group 1, n = 10) or 4 micrograms/kg followed by 1 microgram.kg-1.h-1 (group 2, n = 20) or 8 micrograms.kg-1.h-1 followed by an infusion of 2 micrograms.kg-1.h-1 (group 3, n = 20). During the operation, increases in arterial blood pressure or heart rate that did not respond to a propofol bolus (0.5 mg/kg) were treated with a bolus of intravenous lidocaine (1 mg/kg). Three successive injections were allowed. When baseline values were not restored, opioids were added and the patient was removed from the study. After operation, the clonidine infusions were maintained for 12 h. During this period and at every 30 min, sedation scores and visual analog scale values at rest and at cough were noted. In case of subjective scores up to 5 cm at rest or up to 8 cm at cough, the patients were given access to a patient-controlled analgesia device that delivered epidural bupivacaine. The end point of the study was reached once the patient activated the analgesic delivery button. RESULTS: During surgery, 60% of patients in group 1 compared with 33% of patients in group 2 and only 5% of patients in group 3 were removed from the study protocol because of inadequate anesthesia (P < 0.05). After operation, epidural clonidine provided complete analgesia lasting 30 +/- 21 min in group 1 compared with 251 +/- 237 min in group 2 or 369 +/- 256 min in group 3 (P < 0.05 for group 1 vs. groups 2 and 3 and group 2 vs. group 3). CONCLUSIONS: Epidural clonidine used as the sole analgesic agent provided dose-dependent control of the hemodynamic changes associated with surgical stimulation. It also produced dose-dependent postoperative analgesia without major side effects.

Central Effects of Epidural and Intravenous Clonidine in Patients Anesthetized with Enflurane/Nitrous Oxide An Electroencephalographic Analysis

Epidural clonidine produces regional anesthesia as well as sedation and a decrease in anesthetic requirements. To assess these effects, the electroencephalogram (EEG) was recorded after epidural or intravenous (iv) injection of clonidine during enflurane/N2O anesthesia. Eighteen ASA physical status 1 women undergoing vaginal hysterectomy were allocated randomly to receive epidural clonidine (8 micrograms.kg-1 in 4 ml over 2 min) and iv saline (10 ml over 14 min); or epidural saline (4 ml over 2 min) and iv clonidine (8 micrograms.kg-1 in 10 ml over 14 min); or epidural saline (4 ml over 2 min) and iv saline (10 ml over 14 min). The level of anesthesia was kept constant beginning 10 min before and until 44 min after epidural injection. EEG power spectral analysis was performed throughout the study period using a 2-min average of 8-9-s epochs. Clonidine significantly reduced EEG total power only after epidural administration (P less than 0.05). Relative power increased in the delta band in both the epidural and iv clonidine groups (P less than 0.001). The depression of the total EEG power after epidural injection could be explained neither by systemic absorption alone nor by hemodynamic variations. It may represent the contribution of the direct spinal action of this alpha 2-adrenergic agonist to general anesthesia.

Clonidine pretreatment reduces the systemic toxicity of intravenous bupivacaine in rats.

Backgrounds:Clonidine prolongs the duration of sensory and motor block induced by bupivacaine, and this association, in constant infusion by the epidural route, is used for postoperative analgesia. After a near-fatal intravenous bolus of bupivacaine in dogs, clonidine improves ventricular electrophysiologic parameters, but probably worsens bupivacaine induced bradycardia and depression of the myocardial contractility. The current study, using a rodent animal model, evaluated the influence of clonidine pretreatment on the systemic toxic effects of bupivacaine overdose induced by a constant intravenous infusion. Methods:Twenty Wistar male rats were anesthetized with thiopental, and controlled ventilation was started with an equal mixture of O2 and N2O. Electrocardiogram (ECG), electroencephalogram (EEG), and invasive arterial blood pressure were continuously recorded. Clonidine (5 µg/kg) or saline was injected intravenously in a randomized fashion. After 15 min, an intravenous infusion of bupivacaine was started at 2 mg · kg−1 · min−1. The time of occurrence of the bupivacaine-induced toxic events was recorded and the doses were calculated. Ten (five in each group) additional rats, pretreated according to the same protocol, were killed at the time of the first dysrhythmia, for blood sampling and plasma bupivacaine concentration measurement. Results:Clonidine reduced heart rate and arterial blood pressure before bupivacaine infusion (P < 0.05). The threshold doses at the first QRS modification (11.3 ± 5.6 vs. 2.1 ± 0.9 mg/kg) and the first dysrhythmia (40.6 ± 15.3 vs. 8.48 ± 3.7 mg/kg), the increase In EEG total spectral power (33.3 ± 21.9 vs. 8.2 ± 5.1 mg/kg), the 25 and 50% reduction in baseline mean arterial pressure and heart rate, the isoelectric EEG (58.6 ± 14 vs. 22 ± 6.6 mg/kg), and the final systole (99 ± 16 vs. 51.8 ± 14.5 mg/kg) were significantly greater in the clonidine group than in the saline group (P < 0.01). The time between the first dysrhthymia and 50% reduction of baseline mean arterial blood pressure was not different between the groups. In the additional series, the first dysrhythmia occurred later (10.9 ±4.5 vs. 3.2 + 1.0 min, P < 0.01) and plasma bupivacaine levels were greater (18.7 ± 8.0 vs. 7.8 ± 3.2 µg/ml, P < 0.01) in the clonidine group than in the saline group. Conclusions:In this model, clonidine given prophylactically delays the toxic manifestations of bupivacaine overdose and does not accentuate the subsequent hypotension.

Insertion of a nasogastric tube under direct vision: an even smoother approach

1. Eipe N. Modified allens test performed with a pulse oximeter – back to the future. Acta Anaesthesiol Scand 2007; 51: 648–9. 2. Morgan GE, Mikhail MS, Murray MJ. Textbook of clinical anesthesiology, 4th edn. McGraw Publishers , 2006, p. 124. 3. Foo JYA, Wilson SJ, Dakin C et al. Variability in time delay between two models of pulse oximeters for deriving the photoplethysmographic signals. Physiol Meas 2005; 26: 531–44. 4. Severinghaus JW, Naifeh KH, Koh SO. J Clin Monit Comput 1989; 5 (2):72–81.

Feasibility of the Video-Assisted Thyroid Surgery Under Hypnosis Associated to local Anesthesia

Background: Video-assisted thyroidectomy (VAT) is feasible and safe compared to conventional surgery. Thyroidectomy under hypnosis associated to local anesthesia (HYLA) as an alternative to general anesthesia (GA) has been shown to be effective. However, its combination with VAT has not yet been reported. The aim of the study is to describe the feasibility of VAT under HYLA as a complete minimally invasive approach and evaluate its safety. Methods: Out of 130 consecutive patients referred for thyroidectomy and selected for VAT, 50 patients opted voluntarily for HYLA. Safety and feasibility were considered primary endpoints. Results: Twenty eight patients benefited from a total thyroidectomy (56%). The remaining patients underwent thyroid lobectomy. Median operating time was 102.5minutes (range 70-177) and 92.5minutes (range 51-143) for total thyroidectomy and lobectomy, respectively. Median time in operating room was 146.5minutes (range101-222) and 133minutes (range 96-178) for total thyroidectomy and lobectomy, respectively. Conversion from VAT to a conventional surgical approach occurred in 4 patients (8%). No conversion to GA was required. Hemodynamic parameter measurements were stable during surgery. No permanent hypocalcemia or vocal cord palsy were observed. Ninety eight percent of the patients required just one overnight stay in hospital. Conclusion: The current brief report demonstrates that the combination of VAT and HYLA is feasible without the risk of additional surgical morbidity.

Anaphylaxis to levobupivacaine? Maybe...

We read with great interest the case report by Gupta et al. [1]. One of the positive elements of the paper is the documentation of an anaphylactic mechanism through demonstration of sequentially raised serum tryptase levels, but we feel two other elements of the report appear to provide weaker evidence. Firstly, the skin tests were prick tests; these are less sensitive than intradermal tests [1]. Moreover, the diameter of the positive control wheal was just 3 mm with a negative control of 0 mm. This makes interpretation of wheals £ 3 mm difficult because in order to have a positive reaction, the tested drug must provoke a wheal at least 3 mm more than the control. In addition, the drug concentrations used in the prick tests were not mentioned. Secondly, the IgE dose of penicillin G and V is insufficient to exclude an IgE-mediated sensitisation to penicillins or cephalosporins [2]. The sensitivity of specific IgE to penicillins varies between 15 and 25% depending on the observed clinical manifestations. These in vitro tests are not sufficient to study the cross-reactivity between penicillins and cephalosporins. We believe this report would have been more persuasive if the authors had demonstrated a strongly positive intradermal reaction to a 1:10 000 or even a 1:1000 dilution of levobupivacaine. The interpretation of the MediShield gel (Medtronic UK Ltd., Watford, UK) prick test is not significant (1–2 mm wheals). We would conclude that an allergy to levobupivacaine cannot be excluded but it is far from proven. A sensitisation to another substance was not excluded because the authors did not perform intradermal testing. If intradermal testing with levobupivacaine had been done and had been negative, a provocation test would have been necessary to implicate it positively as the cause of anaphylaxis.

Successful ventilation through a Rüsch intubation guide catheter in severe laryngotracheal stenosis

BackgroundProviding adequate ventilation may remain complex in patients with severe proximal laryngotracheal stenosis, especially when the airway is shared with the surgeon during tracheal resection surgery. We describe an effective alternative to standard endotracheal intubation using a Rüsch flexible intubation guide catheter.MethodsIn two patients undergoing tracheal repair surgery, we failed to insert a 5.0 inner diameter endotracheal tube (6.9xa0mm outer diameter) or a 6.0xa0mm outer diameter endoscope through the laryngotracheal stenosis. However, using indirect laryngoscopy, a 6.0 outer diameter Rüsch flexible intubation guide catheter was passed successfully through the vocal cords and then through the stenosis. Controlled ventilation was achieved by means of the Rüsch guide, provided with its two large Murphy’s eyes. When the trachea was opened, the Rüsch guide was removed just enough for the surgeons to place a Montandon tracheal tube, at that point taking over ventilation. A 7.0 inner diameter endotracheal cuffed tube had been inserted onto the Rüsch guide and left pending upstream from the vocal cords. Once the posterior tracheal wall was sutured, this endotracheal cuffed tube was slid along the Rüsch guide through the vocal cords with the cuff placed beyond the tracheal sutures.ResultsControlled ventilation through the Rüsch flexible intubation guide catheter showed satisfying and stable ventilatory parameters in both patients. Inspiratory pressures of 25–30xa0mmHg were enough to reach adequate tidal volumes around 450xa0ml. End tidal CO2 was kept between 35 and 40xa0mmHg (PaCO2 showed similar values). Standard endotracheal intubation at the end of the tracheal resection was easy and safe thanks to the Rüsch guide still in place between the vocal cords.ConclusionsWe suggest an effective and reliable method using a Rüsch flexible intubation guide catheter for airway management in patients suffering from laryngotracheal stenosis in the setting of tracheal repair surgery.

Epidural Clonidine Used as the Sole-Analgesic Agent During and After Abdominal Surgery: A Dose-Response Study

Background Many studies have shown the beneficial effect of epidural clonidine in postoperative pain management. In these studies, the patients received local anesthetics, opioids, or both in combination with clonidine. Due to the interactive potentiation of those drugs, the importance of the intrinsic analgesic properties of the alpha2 ‐adrenoceptor agonist is difficult to establish. The authors investigated the analgesic potency of epidural clonidine when used as the sole analgesic agent during and after major abdominal surgery. Methods Fifty young adult patients undergoing intestinal surgery under general anesthesia with propofol were studied. At induction, the patients received epidurally either an initial dose of 2 micro gram/kg clonidine followed by an infusion of 0.5 micro gram [center dot] kg‐1 [center dot] h‐1 (group 1, n = 10) or 4 micro gram/kg followed by 1 micro gram [center dot] kg‐1 [center dot] h‐1 (group 2, n = 20) or 8 micro gram [center dot] kg‐1 [center dot] h‐1 followed by an infusion of 2 micro gram [center dot] kg‐1 [center dot] h‐1 (group 3, n = 20). During the operation, increases in arterial blood pressure or heart rate that did not respond to a propofol bolus (0.5 mg/kg) were treated with a bolus of intravenous lidocaine (1 mg/kg). Three successive injections were allowed. When baseline values were not restored, opioids were added and the patient was removed from the study. After operation, the clonidine infusions were maintained for 12 h. During this period and at every 30 min, sedation scores and visual analog scale values at rest and at cough were noted. In case of subjective scores up to 5 cm at rest or up to 8 cm at cough, the patients were given access to a patient‐controlled analgesia device that delivered epidural bupivacaine. The end point of the study was reached once the patient activated the analgesic delivery button. Results During surgery, 60% of patients in group 1 compared with 33% of patients in group 2 and only 5% of patients in group 3 were removed from the study protocol because of inadequate anesthesia (P < 0.05). After operation, epidural clonidine provided complete analgesia lasting 30 +/‐ 21 min in group 1 compared with 251 + 237 min in group 2 or 369 +/‐ 256 min in group 3 (P < 0.05 for group 1 vs. groups 2 and 3 and group 2 vs. group 3). Conclusions Epidural clonidine used as the sole analgesic agent provided dose‐dependent control of the hemodynamic changes associated with surgical stimulation. It also produced dose‐dependent postoperative analgesia without major side effects.