Complications of an uncovered metallic tracheal stent managed by veno-venous extracorporeal membrane oxygenation: a case report.

Airway stents are primarily inserted for the management of airway obstruction associated with an inoperable malignancy and are rarely indicated in benign disease. We outline the complications associated with tracheal stents and describe the use of veno-venous extracorporeal membrane oxygenation (V-V ECMO) to facilitate open tracheal surgery in an apnoeic patient who had an uncovered metallic tracheal stent left in place for an inappropriately long period. Computerised tomography imaging of the neck and thorax provided information for operative planning and described of the stent in addition to the extensive granulation tissue at the distal end of the stent. Veno-venous extracorporeal membrane oxygenation was used to facilitate open tracheal surgery, removal of the tracheal stent and formation of a surgical tracheostomy. Prolonged use of an uncovered metallic airway stent in younger patients with benign disease may lead to the stent being difficult to remove. There may be an accumulation of granulation tissue with the risk of airway obstruction.

Ultrasound guidance for ilioinguinal/iliohypogastric nerve block: a pilot study.

BACKGROUND: Ilioinguinal/iliohypogastric nerve block combined with general anaesthesia facilitates inguinal herniorrhaphy in an ambulatory setting by improving analgesia and reducing opioid requirements. Case reports in children indicate the possibility of colonic puncture and associated morbidity with blind ilioinguinal and iliohypogastric blockade. AIMS: To investigate the feasibility of ultrasound guided ilioinguinal/iliohypogastric nerve block. METHODS: Pilot study of four patients where ultrasound imaging was used to identify the ASIS, anterior abdominal muscle layers, the peritoneum and to guide local anaesthetic infiltration in patients undergoing inguinal hernia surgery and appendicectomy. RESULTS: All patients had successful blocks, without complications. Mean visual analogue scores were 2/10 in the post anaesthesia care unit. Mean opioid consumption was 10 mg of intramuscular morphine in the first 24 h. CONCLUSIONS: Ultrasound guidance for ilioinguinal and iliohypogastric nerve block in the inguinal region is both feasible and a promising technique.

Fentanyl and clonidine as adjunctive analgesics with levobupivacaine in paravertebral analgesia for breast surgery.

The addition of fentanyl or clonidine to levobupivacaine was evaluated in patients undergoing breast surgery under general anaesthesia with intra- and postoperative paravertebral analgesia. Patients were randomly allocated to four groups: Group L received 19 ml bolus levobupivacaine 0.25% plus 1 ml saline followed by an infusion of levobupivacaine 0.1%; Group LF received 19 ml bolus levobupivacaine 0.25% plus fentanyl 50 microg followed by an infusion of levobupivacaine 0.05% with fentanyl 4 microg x ml(-1); Group LC received 19 ml bolus levobupivacaine 0.25% plus clonidine 150 microg followed by an infusion of levobupivacaine 0.05% with clonidine 3 microg x ml(-1); Group C (control) received general anaesthesia without paravertebral analgesia. All groups received postoperative i.v. morphine patient controlled analgesia (PCA). Although mean (SD) postoperative PCA morphine consumption was decreased in LF [7.9 (4.1) mg] and LC [5.9 (3.5) mg]vs L [27.7 (8.6) mg] or C patients [21.7 (5.5) mg], p < 0.01, paravertebral fentanyl and clonidine were associated with significantly increased vomiting and hypotension, respectively.

A comparison of the effects on bispectral index of mild vs. moderate hypothermia during cardiopulmonary bypass.

BACKGROUND AND OBJECTIVE: Bispectral Index correlates with depth of hypnosis in adult patients. Bispectral index monitoring has been separately examined and validated during both mild and moderate hypothermic cardiopulmonary bypass. However, the effect on bispectral index of these two differing cardiopulmonary bypass temperature regimes has not previously been compared, particularly with the use of volatile anaesthetic agents. METHODS: Following Institutional Ethics Committee approval and informed consent, 30 patients undergoing coronary artery bypass grafting had additional bispectral index monitoring. Sixteen patients had mild hypothermic bypass (32-34 degrees C), and 14 had moderate hypothermic bypass (28-30 degrees C). Anaesthesia was standardized, and was maintained with enflurane throughout surgery. Scores were recorded at 14 specific event-related time points during surgery. RESULTS: This study has demonstrated that in this adult population, a relationship exists between bispectral index score and temperature throughout the duration of cardiac surgery, which included mild or moderate hypothermic cardiopulmonary bypass. It also demonstrated that patients which were categorized as having received moderately hypothermic cardiopulmonary bypass had lower bispectral index scores than those patients who received mild hypothermic cardiopulmonary bypass, at time points corresponding approximately with median steady-state bypass temperature, pre-re-warming and early re-warming periods. CONCLUSIONS: Moderate hypothermic cardiopulmonary bypass has lower bispectral index scores when compared to mild hypothermic cardiopulmonary bypass, at a steady state of inspired enflurane. This may reflect an actual increase in the depth of hypnosis. However, as this study did not address the physico-chemical changes of the volatile agent or the accuracy of the bispectral index algorithm at lower temperatures, we would not advocate a change in practice based solely on this report.

The effects of intracuff lidocaine on endotracheal-tube-induced emergence phenomena after general anesthesia.

UNLABELLED: Coughing during emergence from general anesthesia is a common clinical problem. We sought to determine whether inflating the endotracheal tube cuff with lidocaine would create a reservoir of local anesthetic, which might diffuse across the cuff membrane to anesthetize the mucosa, thus attenuating stimulation during extubation of the trachea. A total of 63 patients undergoing elective surgery were enrolled in a prospective, randomized, double-blinded study. After intubation of the trachea with an endotracheal tube, the cuff of the tube was inflated with either lidocaine 4%, saline, or air. After extubation, a blinded observer noted heart rate, blood pressure, oxygen saturation, end-tidal isoflurane concentration, and the incidence of coughing. Data were analyzed by using analysis of variance, Student's t-test, and the chi(2) test for multiple variables. The groups were demographically comparable. There was no difference in hemodynamic or oxygen saturation data between either group. The incidence of coughing was decreased in the lidocaine group for the time period of 4-8 min postextubation (P < 0.05). We conclude that inflation of the cuff of the endotracheal tube can reduce the incidence of coughing in the initial postextubation period, a finding that may benefit certain patient groups in which this is particularly desirable. IMPLICATIONS: Tracheal intubation with an endotracheal tube is often necessary during anesthesia. After intubation, inflating a cuff around the endotracheal tube maintains a seal. This can result in coughing during emergence from anesthesia. Our study shows that inflating the cuff of an endotracheal tube with lidocaine rather than air can reduce the incidence of postextubation coughing.

Effects of the combination of halothane and serotonin uptake blockers on synaptic transmission in the rat dentate gyrus in vitro.

Although the exact basis of their action remains unknown, volatile agents affect noradrenergic and serotoninergic systems. Imipramine and fluoxetine have documented effects on these neurotransmitter transmission systems. Given the common sites of action of these antidepressants and halothane, we examined their individual and combined effects on tonic excitatory post-synaptic potentials (EPSPs) and frequency dependent blockade in the rat dentate gyrus in vitro. Extracellular recordings of field EPSPs were maintained from the dentate gyrus, in the presence of picrotoxin (100 microM). Stimulation at 30 Hz (200 ms) allowed investigation of frequency dependent blockade. Once a stable equilibrium was established, halothane, imipramine and fluoxetine were administered via the perfusate and recordings were made. Halothane produced a dose dependent reduction in EPSP amplitude (EC50 0.28 mM; n = 12). Imipramine (1-10 microM) potentiated the EPSP amplitude (148.2 +/- 8.2%; imipramine 1 microM; n = 6). Fluoxetine (0.5-10 microM) reduced EPSP amplitude to 83.7 +/- 22.1% of control (n = 6). In the presence of halothane 0.2 mM, imipramine reduced the EPSP amplitude to 56.5 +/- 9.9% of control (imipramine 10 microM; n = 6; p < 0.05 compared with imipramine alone). Halothane (0.2 mM) demonstrated frequency dependent blockade. However, neither imipramine nor fluoxetine showed use dependent inhibition at the doses investigated. When combined with halothane 0.2 mM, fluoxetine 10 microM demonstrated frequency dependent blockade at the sixth pulse in the train compared with controls (13.8 +/- 4.7% vs 38.1 +/- 8.3%; n = 6; p < 0.05). The halothane-imipramine combination did not exhibit use dependent blockade greater than controls. The reversal of imipramine-induced EPSP potentiation by the preapplication of halothane has not been previously reported. It may be due to modulation of noradrenergic transmission by halothane. The frequency dependent blockade produced by the combination of fluoxetine 10 microM and halothane may be mediated by a nonspecific membrane effect on 5-HT uptake. These differing effects underline the broad action of volatile agents on synaptic mechanisms.

Effects of halothane on the membrane potential in skeletal muscle of the frog.

Halothane has many effects on the resting membrane potential (V(m)) of excitable cells and exerts numerous effects on skeletal muscle one of which is the enhancement of Ca(2+) release by the sarcoplasmic reticulum (SR) resulting in a sustained contracture. The aim of this study was to analyse the effects of clinical doses of halothane on V(m), recorded using intracellular microelectrodes on cleaned and non stimulated sartorius muscle which was freshly isolated from the leg of the frog Rana esculenta. We assessed the mechanism of effects of superfused halothane on V(m) by the administration of selective antagonists of membrane bound Na(+), K(+) and Cl(-) channels and by inhibition of SR Ca(2+) release. Halothane (3%) induced an early and transient depolarization (4.5 mV within 7 min) and a delayed and sustained hyperpolarization (about 11 mV within 15 min) of V(m). The halothane-induced transient depolarization was sensitive to ryanodine (10 microM) and to 4-acetamido-4'-isothiocyanatostilbene 2,2' disulphonic acid (SITS, 1 mM). The hyperpolarization of V(m) induced by halothane (0.1 - 3%) was dose-dependent and reversible. It was insensitive to SITS (1 mM), tetrodotoxin (0.6 microM), and tetraethylammonium (10 mM) but was blocked and/or prevented by ryanodine (10 microM), charybdotoxin (CTX, 1 microM), and glibenclamide (10 nM). Our observations revealed that the effects of halothane on V(m) may be related to the increase in intracellular Ca(2+) concentration produced by the ryanodine-sensitive Ca(2+) release from the SR induced by the anaesthetic. The depolarization may be attributed to the activation of Ca(2+)-dependent Cl(-) (blocked by SITS) channels and the hyperpolarization to the activation of large conductance Ca(2+)-dependent K(+) channels, blocked by CTX, and to the opening of ATP-sensitive K(+) channels, inhibited by glibenclamide.

The combined effects of halothane and lamotrigine on excitatory postsynaptic potentials and use-dependent block in the rat dentate gyrus in vitro.

UNLABELLED: Halothane affects synaptic transmission in the rat hippocampus with a 50% effective dose (ED50) correlating with clinical figures for minimum alveolar anesthetic concentration (MAC). Halothane dose-dependently suppresses glutamate receptor-mediated excitatory postsynaptic potentials (EPSPs) in the rat hippocampus. It also inhibits voltage-gated Na+ channels. The anticonvulsant lamotrigine acts as a Na+ channel antagonist and inhibits glutamate release after Na+ channel activation. Given their known similar sites of action, the combination of halothane and lamotrigine may alter the inhibition produced by either drug alone. Extracellular recordings of field EPSPs were obtained from the dentate gyrus in the presence of 100 microM picrotoxin (to block GABAA receptors). Stimulation at 30 Hz (200 ms, pulse duration 0.1 ms, six pulses) allowed us to investigate use-dependent block (UDB). Once a stable equilibrium was established, halothane and lamotrigine were administered via the perfusate, and recordings were collected. Both halothane (n = 12) and lamotrigine (n = 6) exhibited reversible inhibition of the EPSP (ED50 0.28 mM [1.2%] and 100 microM, respectively) at low-frequency stimulation. Slices (n = 6) exposed to halothane 0.2 mM (0.75%), then to lamotrigine, showed reduced sensitivity compared with lamotrigine alone. Halothane 0.2 mM potentiated the control UDB (Pulse 6:31% +/- 11% control versus 20.5% +/- 2.5% halothane 0.75%; P < 0.05; n = 6). Lamotrigine had no effect on control UDB. The combination (n = 6) did not alter UDB effects compared with controls or lamotrigine alone. Halothane may reduce the effect of lamotrigine on glutamate release, either at the receptor or via effects at the inactivated Na+ channel. The site of interaction requires further examination. IMPLICATIONS: The general and local anesthetic drugs halothane and lamotrigine act at both the glutamate receptor and the Na+ channels and, in our experiments, independently inhibited synaptic transmission at low-frequency stimulation. Although halothane potentiated control use-dependent block, lamotrigine had no effect. Halothane attenuated the inhibitory dose-dependent effects of lamotrigine on synaptic transmission at a low frequency. The clinical importance of this interaction in patients presenting for anesthesia remains unanswered.

Technical note: the humeral canal approach to the brachial plexus.

Many variations to the axillary approach to the brachial plexus have been described. However, the success rate varies depending on the approach used and on the definition of success. Recent work describes a new approach to regional anaesthesia of the upper limb at the humeral/brachial canal using selective stimulation of the major nerves. This report outlines initial experience with this block, describing the technique and results in 50 patients undergoing hand and forearm surgery. All patients were assessed for completeness of motor and sensory block. The overall success rate was 90 percent. Motor block was present in 80 percent of patients. Completion of the block was necessary in 5 patients. Two patients required general anaesthesia. The preponderance of ulnar deficiencies agrees with previously published data on this technique. No complications were described. Initial experience confirms the high success rate described using the Dupré technique. This technically straightforward approach with minimal complications can be recommended for regional anaesthesia of the upper limb.

A comparison of propofol with a propofol-ketamine combination for sedation during spinal anesthesia.

Propofol (P) is increasingly used as a sedative during regional anesthesia. Providing titratable sedation and rapid recovery, it can compromise hemodynamic stability. However, in combination with ketamine (K), it provides stable hemodynamics during total intravenous anesthesia, avoiding emergence phenomena. We compared the efficacy, respiratory and hemodynamic profiles, and side effects of these two sedative regimes in patients undergoing spinal anesthesia. Forty patients, ASA physical status I and II, undergoing urologic or orthopedic procedures were randomly assigned to one of two groups (n = 20 each). Group 1 (P + K) received initial doses of 0.4 mg/kg P, 0.1 mg/kg K, followed by an intravenous infusion of 1.2 mg x kg(-1) x h(-1) and 0.3 mg x kg(-1) x h(-1), respectively. Group 2 (P) received bolus 0.5 mg/kg and infusion 1.5 mg x kg(-1) x h(-1). Subsequent infusion rates were titrated to a predetermined sedation level using a 5-point score. Heart rate, arterial pressure, respiratory rate, oxygen saturation end-tidal CO2, and oxygen requirements were recorded. Sedation scores were similar for both groups. There was no difference in total propofol requirements between Group 1 (146 +/- 94 mg) and Group 2 (137 +/- 52 mg) (mean +/- SD). Mean arterial pressure was significantly higher in the P + K group, e.g., 91 mm Hg (86-94) vs 75 mm Hg (69-83) at 30 min (mean +/- SD). Administration of vasopressors and fluids as well as recovery and emergence phenomena were similar between groups. Although the described additive effect of propofol and ketamine was not confirmed, the combination conferred hemodynamic stability during spinal anesthesia.

The effect of passive smoking on the incidence of airway complications in children undergoing general anaesthesia.

The aim of this study was to assess whether passive smoking affected the frequency of airway complications in children undergoing general anaesthesia. One hundred and twenty-five children undergoing general anaesthesia for elective daycase surgery were monitored for adverse respiratory events and desaturation during induction, intra-operatively and in the recovery room. Oxygen saturation was monitored throughout and a venous sample was taken for estimation of carboxyhaemoglobin levels. Parents were asked to fill in a questionnaire detailing their smoking habits. Sixty-three of the children were passive smokers with a potential daily exposure varying from 5-130 cigarettes. There was no difference in the frequency of respiratory events between passive smokers and those not exposed to cigarette smoke at induction or intra-operatively. However, in the recovery room, desaturation was significantly more common in passive smokers (p < 0.02). This was related to the cumulative number of cigarettes smoked by individuals to whom the child was exposed (p < 0.05). Neither carboxyhaemoglobin levels nor domiciliary address were predictive of desaturation. This study suggests that passive smoking contributes to postoperative arterial oxygen desaturation following general anaesthesia in children.

Intrathecal narcotics in cancer pain--a case report.

A 61 year old female patient presented with metastatic bone pain three years post mastectomy. Standard oral analgesics and epidural morphine were ineffective in achieving pain control. Her pain was eventually controlled with morphine sulphate 48 mg daily via a self administered intrathecal pump. These devices are being used with increasing frequency and this case report highlights some of the problems encountered in this patient's management.