Burst suppression during propofol anaesthesia recorded from scalp and subthalamic electrodes: report of three cases.

BACKGROUND: Measurement of slow EEG activity and burst suppression are the main tasks in monitoring the effects of anaesthestics with EEG, which is often done with commercial univariate indexes such as BIS. The aim of this study was to describe the characteristics of burst suppression EEG during propofol anaesthesia using scalp electrodes and depth electrodes in the subthalamic nucleus. Specifically, we describe the electrical fields of the three EEG patterns we have previously described: the sharp wave, the burst and the spindle. METHODS: We recorded the EEG of three Parkinson patients during propofol anaesthesia from the scalp electrodes and the depth electrode implanted in the subthalamic nucleus for treating parkinsonism. RESULTS: (1) The slow waves of bursts recorded from all surface electrodes on scalp or neck with depth electrode reference are positive and have the highest amplitude in frontal electrodes, suggesting synchronous generation in the whole cerebral cortex. (2) The sharp wave and spindles have the highest amplitude at vertex. They are opposite in polarity in vertex and depth electrodes when referred to the neck electrode, suggesting generation in the sensorimotor cortex. CONCLUSIONS: Recording simultaneously EEG from the depth and scalp electrodes shows that bursts and their slow wave oscillations are synchronous in the whole cortex while spindles and sharp waves are produced by the sensorimotor cortex. The amplitude of slow waves recorded with surface electrodes is equal to the difference of the wave at two electrodes and therefore only a small part of that generated by the cortex.

Neurophysiological and technical considerations for the design of an implantable phrenic nerve stimulator.

Sequential stimulation during one muscle contraction of several compartments of a motor nerve, using multiple-electrodes, allows individual nerve-muscle compartments to be stimulated at fairly low frequencies. This provides time for recovery even during muscle contraction. However, the whole muscle is stimulated at near to its optimum fusion frequency, which provides smooth muscle contraction. This stimulation system imitates the natural activation of skeletal muscle. The new phrenic nerve stimulator described utilises the principle of sequential motor nerve stimulation. It also incorporates a sigh function. The sigh current recruits additional axons at certain intervals and thus creates and keeps available a reserve of conditioned muscle. Clinical advantages result: the conditioning phase after the beginning of long-term phrenic nerve stimulation for electroventilation is shortened and muscle fatigue is delayed. A need of increase of gas exchange can be answered by increasing tidal volume instead of respiration rate alone.

Potency of propofol, thiopentone and ketamine at various endpoints in New Zealand White rabbits.

Effective plasma concentrations of propofol, thiopentone and ketamine were determined at different endpoints in a study with randomized, crossover design in nine New Zealand White rabbits. A continuous infusion was used (30 ml/h) with concentrations of 10 mg/ml for propofol, 25 mg/ml for thiopentone and 20 mg/ml for ketamine. The endpoints were loss of the righting reflex, loss of purposeful reactions to tail clamping (as an example of a peripheral pain stimulus) or to intranostril insufflation of ammonia vapour (as an example of a central reflex stimulus), and the recovery of these reflexes and reactions. According to the ED50 values the potency ratios of propofol, thiopentone and ketamine were at the loss of righting reflex 1:1.8:1.2, at the loss of reaction to ammonia vapour 1:1.5:1.6, and at the loss of reaction to tail clamping 1:1.5:3.9, respectively. Recovery was significantly faster after propofol than after thiopentone and ketamine. Measuring the effective plasma concentrations of intravenous anaesthetics provides a method of relating dose to effect, but there still remains a variable gap between plasma concentration and effect.

Edrophonium is better than neostigmine to antagonize residual vecuronium induced neuromuscular block.

Edrophonium (EDR) has the advantages of a quick onset of action and reduced cholinergic effects compared to neostigmine (NST) when they are used to antagonize neuromuscular block (NMB). There are few studies about antagonism of very weak residual NMB. Therefore we compared hemodynamic stability, train-of-four (TOF) characteristics and reversal time (time from administration of antagonists to train-of-four-ratio (TR) at least 0.70) of EDR 0.5 mg kg-1 + atropine (ATR) 0.007 mg kg-1 to NST 0.04 mg kg-1 + glycopyrrolate (GLY) 0.008 mg kg-1 when they were used to antagonize a residual vecuronium (VEC)-induced NMB (T1 25-75%). The NMB was monitored in 64 patients using the evoked electromyogram of the hypothenar muscle of the hand. An adequate antagonism was defined as a TR of 0.70 or higher. Heart rate was significantly higher in NST+GLY group 2 min after administration of the antagonists in comparison with the EDR+ATR group. The advantages of EDR (higher T1, TR and percentage of patients with an adequate recovery) were obvious during the first 5 min of reversal time. Therefore we conclude, that under the conditions described in the present study, EDR antagonizes residual VEC induced NMB faster than NST.

Mechanical ventilation or phrenic nerve stimulation for treatment of spinal cord injury-induced respiratory insufficiency.

STUDY DESIGN: Prospective clinical study of two treatments. OBJECTIVE: To compare mechanical ventilation (MV) with phrenic nerve stimulation (PNS) for treatment of respiratory device-dependent (RDD) spinal cord-injured (SCI) patients. SETTING: Department for spinal cord-injured patients of an insurance-company-run trauma hospital in Hamburg, Germany. METHODS: Prospective data collection of treatment-related data over 20 years. RESULTS: In total, 64 SCI-RDD patients were treated during the study period. Of these, 32 of the patients with functioning phrenic nerves and diaphragm muscles were treated with PNS and 32 patients with destroyed phrenic nerves were mechanically ventilated. Incidence of respiratory infections (RIs per 100 days) prior to use of final respiratory device was equal in both groups, that is (median (interquartile range)) 1.43 (0.05-3.92) with PNS and 1.33 (0.89-2.21) with MV (P=0.888); with final device in our institution it was 0 (0-0.92) with PNS and 2.07 (1.49-4.19) with MV (P<0.001); at final location it was 0 (0-0.02) with PNS and 0.14 (0-0.31) with MV (P<0.001). Thus, compared to MV, respiratory treatment with PNS significantly reduces frequency of RI. Quality of speech is significantly better with PNS. Nine patients with PNS, but only two with MV, were employed or learned after rehabilitation (P=0.093). The primary investment in the respiratory device is higher with PNS, but it can be paid off in our setting within 1 year because of the reduced amount of single use equipment, easier nursing and fewer RIs compared to MV. CONCLUSIONS: PNS instead of MV for treatment of SCI-RDD reduces RIs, running costs of respiratory treatment and obviously improves patients' quality of life.

Requirements of propofol at different end-points without adjuvant and during two different steady infusions of remifentanil.

BACKGROUND: Some reports show no interaction between propofol and opioids, whereas others state such interactions. We evaluated the influence of remifentanil on propofol requirements at certain anesthesia end-points. METHODS: Elective surgical patients were randomly assigned to three groups of 15 patients each. Premedication was with oral diazepam 0.1 mg kg(-1). Patients were blindly given equal volumes of saline or remifentanil (7.5 or 30 microg kg(-1). h(-1)) 1 min before induction of anesthesia with infusion of propofol, 30 mg kg(-1). h(-1). We recorded times to, propofol requirements, and bispectral index at loss of counting (LC), loss of verbal command (LVC), loss of reaction to tetanic stimulation (LRT), and onset of burst suppression pattern (BSP) of electroencephalography. RESULTS: In the remifentanil groups end-points were attained significantly faster and with lower doses of propofol than in the saline group. BIS-values were significantly different at LRT and BSP end-points. CONCLUSIONS: We conclude that remifentanil infusion started before induction of propofol anesthesia significantly reduces propofol requirements at all end-points. The results suggest that remifentanil accelerates the hypnotic onset of propofol.

Laryngeal muscle recovery after suxamethonium. Detection during intratracheal jet ventilation by pressure curve monitoring.

Complications due to intratracheal jet ventilation are often caused by the unrecognized recovery of laryngeal muscles. The rate of rise of pressure in a main bronchus alters with changes of the glottic aperture during jet ventilation. The special pressure curve monitor sets off an alarm when the steepness of the rising curve changes. During recovery these alarms, as well as the onset of phonation, coughing, spontaneous breathing and forearm muscle activity are recorded simultaneously. Forearm muscle activity always appears later than the alarm, and often later than the other recorded phenomena. Pressure curve monitoring provides advance warning of returning muscle activity in the larynx, but conventional muscle activity monitoring in the forearm does not.

[Effect of various tracheal diameter forms on airway pressure in experimental intratracheal injector ventilation]. / Die Wirkung verschiedener Tracheaquerschnittsformen auf den Atemwegsdruck bei experimenteller intratrachealer Injektorventilation.

Experimental catheter jet ventilation was performed on tracheal models of four sizes and six different shapes. Three coaxial jet positions were tested: centrally, adjacent to the wall and in a corner of the model. Driving gas pressure and size of the jet were kept constant. Airway pressure declines as the models increase in size. In the corner position, airway pressure is always less than in the centre position. In models with equal cross-section areas, airway pressure differs in all other shapes from that of the cylindrical shape. With this equipment, airway pressures between 9 and 14 cm H2O were achieved in cylindrically-shaped tracheas of a diameter of 15 resp. 20 mm. With the same transverse diameters, but with clinically relevant different tracheal shapes and jet positions, however, the values may vary from 18 cm H2O to less than 5 cm H2O.

[Working conditions and complications during laryngomicroscopies under endotracheal ventilation via intubation tubes or injection ventilation]. / Arbeitsbedingungen und Komplikationen bei Laryngomikroskopien, intratracheal ventiliert durch Intubationstuben oder mit Injektor-Ventilation.

During a period of 7 years 693 laryngomicroscopies (LAR) were performed on 490 patients. General anaesthesia was given by 21 anaesthesists: 5 applied ventilation only through a conventional intubation tube. Of the remaining 16 anaesthesists, 8 constantly prefered, 4 used occasionally jet ventilation (JET), and 4 applied both methods alternatively. No rationale was found for this choice. Laryngomicroscopies were performed by 14 ENT surgeons. One case of subcutaneous emphysema and two of pneumothorax were obtained with JET, obviously because of inexperience and neglect of precautions. Two epidermoid carcinomas in the left posterior commissure escaped the primary LAR, most probably because of poor vision due to the intubation tube, and were found during subsequent procedures with JET. In spite of the risk of complications (mostly avoidable with care and increasing experience), the main advantage of JET is the better chance of revealing of carcinoma in an earlier phase, when it is more amenable to curative therapy. Therefore, we no longer recommend ventilation through an intubation tube for laryngomicroscopies, but prefer intratracheal jet-ventilation for this purpose.

Neuromuscular blocking characteristics of vecuronium after tubocurarine-induced "fade". An experimental double-blind clinical study.

OBJECTIVE: The fade in train-of-four (TOF) monitoring is considered to be due to blocking of the prejunctional nicotinic acetylcholine receptors (AchRs). During onset of the neuromuscular block (NMB) tubocurarine (TC) causes more fade in the TOF responses than vecuronium (VEC). Therefore we wanted to investigate whether onset or duration of action of VEC or TC would be improved with a priming dose of an agent with different prejunctional activity. METHODS: The rates of NMB were measured following priming doses of 0.15 mg x kg(-1) of TC and 0.015 mg x kg(-1) of VEC with 6 min priming time. The individual time course of action of 0.6 mg x kg(-1) of TC (1.13 x ED 95) and 0.1-0.2 mg x kg(-1) of VEC (1.75-3.5 x ED95) were examined with a priming dose of the same agent or the other agent, by measurement of changes in the evoked compound EMG from the hypothenar muscle. RESULTS: Priming doses of TC decreased mean TOF ratio to 67% [95% confidence interval (CI) = 56-78] during priming time, which was significantly lower than after priming with VEC 87% (76-97; P < 0.001). Despite the higher TOF ratio, the priming dose of VEC accelerated the onset time of intubation dose of TC more than the priming dose of TC (P = 0.0018). Priming with TC prolonged the duration of VEC-induced NMB by 35-70 min compared with priming with VEC, which means that a small priming dose of TC changes VEC from a muscle relaxant with intermediate action to a long-acting agent. CONCLUSION: Priming with TC caused a lower TOF ratio; however, priming with TC did not accelerate the onset time of either agent as much as priming with VEC. It appears that potentiation of NMB after combination of VEC and TC is not dependent on "fade" receptors.

End-tidal oxygen concentration and pulse oximetry for monitoring oxygenation during intratracheal jet ventilation.

OBJECTIVE: In this study, we evaluated the usefulness of end-tidal oxygen monitoring during intratracheal jet ventilation (ITJV) for endolaryngeal laser surgery. METHODS: A total of 20 consecutive patients of both genders scheduled for endolaryngeal procedures under general anesthesia were studied. Inspiratory oxygen concentration and respiratory rate were varied, with patients serving as their own controls. Readings of pulse oximetry, airway oxygen, and carbon dioxide concentrations were recorded, and arterial blood samples for blood gas analysis were taken. RESULTS: At jet cycle rates of 20 cycles/min, end-tidal oxygen (ETO2) concentration indicated alveolar hypoxia 30 to 60 sec before hypoxemia was detected by pulse oximetry. Jet mixing of inspiratory and expiratory gas caused a larger difference between end-tidal and arterial gas concentrations than normally seen with conventional ventilation. Correlations between ETO2 concentrations, oxygen saturations, and arterial oxygen levels depended on respiratory rate and inspiratory oxygen concentration; correlations were stronger at low than at high inspiratory oxygen concentrations and stronger at low than at high respiratory rates. CONCLUSIONS: ETO2 concentration should be maintained well over 21% during ITJV to prevent alveolar and arterial hypoxia. Monitoring of respiratory oxygen concentrations at jet cycle rates of 20 cycles/min and less verifies safe oxygen levels during laser surgery, and confirms adequate alveolar oxygenation.

Antifibrinolytic therapy for prevention of hemorrhage during surgery of the thyroid gland.

The amount of fibrinolytic activity in the thyroid gland equals that of the prostate. In order to examine the effect of the antifibrinolytic drug tranexemic acid on perioperative bleeding saline or tranexemic acid were given randomized double blind to 76 consecutive patients who came for scheduled thyroid surgery. No significant differences were found in perioperative bleeding between patients in the treatment group (n = 39) and control group (n = 37).

Morphologic study of the adult trachea at the 7th and 12th ring. A study on specimens from 205 autopsies.

During 205 autopsies in Finland, the seventh and twelfth tracheal ring were collected and their cross-sectional shapes and measurements were recorded. Six already known cross-sectional shapes were found, appearing with frequencies which differ from previous studies. New finding: the shape of the seventh ring was different from that of the twelfth in 46% of the male and in 60% of the female cases.

Epileptic EEG discharges during burst suppression.

Barbiturate anaesthesia is used in the treatment of status epilepticus and severe epilepsy of children. EEG is then used as a measure of the depth of anaesthesia, burst suppression being an easily identified EEG pattern. In this case report we describe epileptiform discharges during EEG suppression in two children undergoing barbiturate anaesthesia for treatment of intractable seizures. One of them had focal, rhythmic discharges of negative spikes on the positive suppression level. Bursts were readily produced by visual stimuli with flashes of red light but this did not increase the frequency of focal spike discharges after bursts. The other patient had generalised, high amplitude spike-wave complexes, which were easy to distinguish from the bursts. We emphasise that it is important to make a distinction between electrocerebral silence, or isoelectric EEG as it was previously called, from EEG suppression. It is also important to distinguish epileptiform discharges from bursts, if the intention is to keep the anaesthesia at EEG burst suppression level.

The effect of diclofenac and ketoprofen on halothane MAC in rabbit.

Non-steroidal anti-inflammatory drugs obviously act also on the central nervous system. We, therefore, studied the effect of diclofenac 3 mg/kg and ketoprofen 4 mg/kg on the minimum alveolar concentration (MAC) of halothane in 10 New Zealand White rabbits. After determination of halothane MAC, total doses of NSAIDs were administered intravenously as three subdoses: 12.5%, 37.5% and 50% of the total dose. Depth of anaesthesia did not increase significantly after the first two doses with either drug. With ketoprofen, halothane MAC increased after subdose 3 from 1.52 (SD 0.42) vol% to 1.9 (SD 0.36) vol% (p < 0.01). With diclofenac, halothane MAC increased after subdose 3 from 1.44 (SD 0.18) vol% to 1.60 (SD 0.39) vol% (ns). With both drugs, large interindividual differences of MAC appeared after full doses of NSAIDs.

A pressure curve monitor for intratracheal jet ventilation.

Most of the complications during intratracheal jet ventilation for laryngomicroscopy are due to the unnoticed wearing off of laryngeal muscle relaxation. Recovering laryngeal muscle function will, by slightly narrowing the size of the glottis, influence the slope of the quickly rising part of the pressure curve, when influences on maximum airway pressure are still not detectable. An electronic device incorporating the window comparator technique monitors the pressure curve and sets off an alarm before changes in maximum airway pressure or recovery of muscle strength in the forearm are detectable. The pressure curve monitor could be useful also with intratracheal jet ventilation for treating adult respiratory deficiency and with conventional ventilators during anaesthesia to detect the wearing off of muscle relaxation.

Diclofenac versus indomethacin given as intravenous infusions: their effect on haemodynamics and bleeding time, and side-effects in healthy subjects.

Given as an intravenous infusion during a 1-hour period, 32.5 mg diclofenac and 25 mg indomethacin did not cause significant changes in blood pressure or pulse rate in 31 healthy subjects. One hour after the end of the infusion, the bleeding time was significantly prolonged with both drugs; however, the mean values were within the normal range. There was no difference in the type of side-effects recorded in this study when compared to previous reports, except for a centrally stimulating effect of diclofenac, which appeared in 11 subjects. Diclofenac and indomethacin thus seem suitable for a patient study of pre-, intra- and postoperative treatment of pain.

Efficacy and safety of premedication with oral ketamine for day-case adenoidectomy compared with rectal diazepam/diclofenac and EMLA.

BACKGROUND: Because of its pain-attenuating and sedative properties oral ketamine has been used as premedication in children and adults. We wanted to compare in children scheduled for adenoidectomy safety and efficacy of oral ketamine with a premedication that causes similar preoperative sedation and relief of pain at the venepuncture site. We also evaluated the effect of i.v. glycopyrrolate added to these combinations. METHODS: One hundred children between 10 and 15 kg of body weight scheduled for day-case adenoidectomy were randomly assigned to one of four groups: groups DG and DS received diclofenac 12.5 mg and diazepam 0.5 mg/kg rectally, EMLA cream at the venepuncture site, and placebo orally; groups KG and KS received ketamine 6.0 mg/kg orally, placebo cream at the puncture site, and placebo rectally; additionally, groups DG and KG received glycopyrrolate 5 microg/kg, and groups DS and KS received placebo intravenously. We recorded perioperatively scores (open scale 1-9) for stridor, sedation, bleeding, nausea, pain, heart rate, the need for analgesics and registered psychotomimesis and well-being at home. RESULTS: The children of the K-groups became more tearful during separation from their parents (P=0.0072). No other differences were found between the ketamine and diazepam/diclofenac groups before and after premedication until induction of anaesthesia. Oral ketamine produced unpleasant psychotomimesis in four out of 59 children. During the first 10 min postoperatively, the score for stridor was significantly higher in group KS than in the D-groups; stridor scores > or = 6 were seen in one child of the D-groups (DS) and in six children of the K-groups (n.s.), of whom three developed laryngospasm (one reintubation). Glycopyrrolate diminished salivation in all groups, but had no effect on stridor scores. Additionally, glycopyrrolate delayed the onset of eating at home. CONCLUSION: Premedication with racemic oral ketamine 6 mg/kg does not seem to be suitable for upper airway procedures. Addition of i.v. glycopyrrolate before the induction of anaesthesia significantly reduced the scores for salivation.