[Hemodynamic effects of a ventriculo-cisternal perfusion of bupivacaine]

OBJECTIVES

The cardiotoxic properties of bupivacain have been well documented under in-vitro, as well as under in-vivo conditions. A further mechanism of cardiovascular impairment by bupivacaine via the central nervous system gained investigational interest in animal studies. The aim of our study was to demonstrate the effect of a ventriculocisternal perfusion of bupivacain on systemic hemodynamic variables and their reversibility by wash-out with mock-CSF.

METHODS

After obtaining animal investional committee consent, nine anaesthetized and relaxed pigs were prepared for a ventriculocisternal perfusion (VCP). Hemodynamic data were obtained by invasive blood pressure measurements in the high and low pressure system as well as cardiac output (thermodilution technique), intracranial pressure and electrocardiogram. Systemic vascular resistance and stroke volume were calculated using standard formulas. A second group of three animals were exposed to an intravenous infusion of the same dose of bupivacain over the same period of time to rule out direct cardiac effects. After instrumentation baseline data were obtained (K0 1) under VCP with mock-CSF for 30 minutes. The mock-CSF was replaced by 0.05% bupivacaine in mock-CSF and VCP was continued with 3 ml.h-1 for 20 minutes. After administration of 500 micrograms bupivacaine data were collected (BU). The bupivacaine solution was replaced by mock-CSF and after twenty minutes hemodynamic measurement were repeated (K02).

RESULTS

The intravenous administration of 500 micrograms bupivacaine had no effect on all measured variables. VCP of the same dose resulted in significant increase in heart rate, systolic, diastolic and mean arterial blood pressures. Left and right heart filling pressures as well as systemic vascular resistance were not affected while the stroke volume decreased. After continuation of VCP with mock-CSF hemodynamic changes were reversed.

DISCUSSION

Our results demonstrate that bupivacaine initiates an indirect cardiovascular stimulating effect of a VCP with 500 micrograms of bupivacaine via the central nervous system. The intravenous administration of the same dose had no effect. The centrally mediated cardiovascular effect of bupivacaine was reversed by wash-out with mock-CSF. The cardiovascular stimulation observed in this animal experiment may be of clinical relevance as a potential sign of toxic effects of bupivacaine on the CNS.

Local brain surface temperature compared to temperatures measured at standard extracranial monitoring sites during posterior fossa surgery

Mild hypothermia is assumed to protect against secondary brain injury. However, the accuracy of brain temperature estimation remains debatable if direct measurement in the target area is to be avoided or is impossible. Furthermore, intracerebral temperature gradients exist, especially under intraoperative conditions. We aimed to establish how brain surface temperatures (TBrain) relate to temperatures taken at standard sites in posterior fossa surgery. Ten patients undergoing cerebellopontine angle tumor removal were monitored for TBrain, esophageal temperature (TEso), bladder temperature (TBlad), ipsi- and contralateral tympanic membrane (TTymp-I, TTymp-C), and scalp temperatures (TScalp). During monitoring, TEso increased from 35.3+/-0.2 degrees C to 36.0+/-0.3 degrees C. After dura opening, TBrain was -0.14+/-0.1 degrees C below TEso. At the end of tumor removal, this difference increased to -0.43+/-0.31 degrees C (P < 0.05). TTymp-C was -0.29+/-0.18 degrees C below TBrain at dura opening. TTymp-C reflected the behavior of TEso adequately (r = 0.938), however, with a mean difference of -0.39+/-0.04 degrees C. In contrast, TTymp-I readings closely followed temperature changes in the area of surgery. TBlad reflected TEso except in periods of rapid temperature changes. In posterior fossa (PF) surgery, local TBrain is most accurately reflected by TEso. For clinical use TBlad and TTymp-C are also sufficient to assess brain surface temperature in the PF. Intraoperative surface cooling of the brainstem is less than the previously described cooling rate of exposed cerebral cortex.

[Regional distribution of predisposition to maligant hyperthermia in Germany: tate in 1997]

Malignant hyperthermia (MH) is a rare autosomally dominantly hereditary and potentially life-threatening disease. The prevalence of the genetic MH predisposition is estimated as 1:10,000 to 1:20,000. In Germany no data on the regional distribution are available. Therefore, the purpose of this investigation is to summarise and present the epidemiological data of all German MH laboratories. Nine German hospitals offer the specific in vitro contracture test to diagnose the MH predisposition. All German MH laboratories carry out the examination in accordance with the standardised protocol of the European Malignant Hyperthermia Group. The laboratories were asked to provide the number of all patients investigated, excluding those suffering from other neuromuscular diseases, separated according to diagnostic groups and their places of residence, the number of the identified MH-families as well as the number of the clinically suspected and investigated MH cases with their places of residence. Eight MH laboratories provided the requested data. Until September 1997 a total of 2620 patients were investigated. In 865 patients (34%) MH suspicion was confirmed (diagnosis: MHS). 1494 patients (56%) were released by investigation from MH-suspicion (diagnosis: MHN). In 261 patients (10%) the MH-predisposition remained unsolved (diagnosis: MHE). 580 MH families were identified. Among 2620 patients 757 were clinically suspected MH cases. 35% of these suspected MH cases were classified as MHS, 10% as MHE and 55% as MHN. The documentation of the patients places of residence classified as MHS and MHE into a map of Germany demonstrates an exhaustive distribution with an increased regional prevalence in the areas of the MH laboratories. This concentration in the area of the MH laboratories becomes even more evident, when the places of residence of the MH suspected cases are demonstrated. In conclusion, the distribution of the MH predisposition is uniform and exhaustive in Germany. The presented regional concentration of clinically suspected MH cases among the MH laboratories is mainly interpreted as an expression of effective regional education and information. Considering the overall incidence of the MH predisposition as described above only 15-20% of the MH patients have so far been identified. The MH laboratories have already released about 10,000 patients from the suspicion of MH predisposition. A preliminary prevalence of at least 1:60,000 to 1:80,000 in Germany can be estimated according to the presented data.

[Cerebral neuroprotection and ketamine]

Ketamine is said to increase intracranial pressure (ICP), cerebral blood flow (CBF) and cerebral metabolic rate for oxygen (CMRO2) and hence to be unsuitable for neuroanaesthesia. This may require reconsideration in the light of the neuroprotective properties mediated by the interaction of ketamine with the N-methyl-D-aspartate receptor (NMDA). Meta-analysis of published experimental rodent studies yields contradictory conclusions. Ketamine does not provide neuroprotection against hypoxic hypoxaemia or focal cerebral ischaemia. During complete forebrain ischaemia of 10 min duration, ketamine offers some degree of protection only if administered before (i.e. prophylactically) and after (i.e. therapeutically) a transient ischaemic episode. In experimental head injury, ketamine may be protective if administered therapeutically within 2 h after the trauma. In the case of incomplete forebrain ischaemia, ketamine provides neuroprotection if administered both before and during ischaemia. Clinical or primate studies are not available; extrapolation of results derived from rodent studies requires caution and has limitations. With respect to the pharmacodynamic action providing neuroprotection, NMDA-receptor antagonism may be just one of several mechanisms; others include scavenging of free radicals, a central sympatholytic effect and augmentation of dopamine metabolism in the caudate. The suitability of ketamine for neuroanaesthesia, which must also take account of its effects on ICP, CBF and CMRO2, is--for the time being--questionable.

Effects of fenoldopam on intracranial pressure and hemodynamic variables at normal and elevated intracranial pressure in anesthetized pigs

Fenoldopam (FE), a dopamine DA1-receptor agonist, has been introduced for treatment of arterial hypertension and heart failure and for preservation of renal function. Vasodilators are generally assumed to affect all vascular beds including the cerebral circulation. We have evaluated effects of FE-induced (4 micrograms.kg-1.min-1) arterial hypotension on intracranial pressure (ICP) and intraocular pressure (IOP) under conditions of normal and increased intracranial elastance. ICP and IOP responses to hypertension were tested by infusion of angiotensin II (15 micrograms.kg-1.min-1), and the response to hypercapnia was tested by elimination and reintegration of soda lime canisters in the breathing circuit. Intracranial elastance was increased by infusing mock cerebrospinal fluid (CSF) into the lateral ventricle (20 +/- 3 ml.h-1). Arterial hypotension induced with FE did not increase ICP. With increased intracranial elastance, the infusion rate of mock CSF had to be reduced while administering FE to avoid a rise in ICP (p < 0.05 compared with preinfusion value); this indicates a shift on the volume-pressure curve to the right. There were no indicators that cerebral autoregulation or CO2 reactivity of the cerebral vasculature were affected by FE in this anesthetized porcine model, as speculated from analysis of the time course of delta ICP. There are, however, indicators of increased intracranial elastance, most likely caused by vasodilation. Caution should hence be exercised when FE is administered to patients with increased intracranial elastance.

Heated breathing tubes affect humidity output of circle absorber systems

STUDY OBJECTIVE

To verify whether the airway climate in circle systems can be improved with heated breathing tubes.

DESIGN

Randomized, controlled, prospective clinical study.

SETTING

Operating theater of the Department of Maxillofacial Surgery.

PATIENTS

26 adult patients undergoing prolonged anesthesia.

INTERVENTIONS

A total of 26 prolonged anesthetics were conducted in adult patients using a minimal fresh gas flow rate (0.6 L/min) and silicon breathing tubes (16 mm internal diameter) containing a heated coil. Group 1 (n = 10 patients) was the control group; breathing tubes were unheated. In Group 2 (n = 10 patients), breathing tubes were heated to 30 degrees C. In Group 3 (n = 6 patients), breathing tubes were heated to 36 degrees C.

MEASUREMENTS AND MAIN RESULTS

Humidity and temperature were measured at the Y-piece. Inspiratory temperature on Group 2 was significantly higher than in Group 1. In Group 3, both inspiratory temperature and absolute humidity were significantly higher than in Group 1. After 5 minutes of ventilation, water content and temperature of inspiratory gases were significantly higher in Group 3 than in Group 1.

CONCLUSION

Low-flow systems need at least 120 minutes to achieve a satisfactory airway climate. Heated breathing tubes effectively reduce this delay.

[Securing the airway in children with the Morquio-Brailsford syndrome]

Mucopolysaccharidosis IVA (Morquio-Brailsford syndrome) results from an inborn deficiency of n-acetyl-galactosamine-6-sulphate sulphatase. Clinical features include skeletal deformities with hypoplasia or absence of the odontoid process of the axis. The resulting atlanto-axial subluxation compresses the spinal cord, resulting in cervical myelopathy. Without treatment, quadriplegia ensues sooner or later; consequently, surgical decompression and dorsal fusion of the cervical vertebrae is recommended, either prophylactically or therapeutically. Anaesthesiological management must focus on protection of the airway without compromising integrity of the cervical spinal cord; quadriplegia subsequent to positioning of the head under anaesthesia has been reported. We have performed fiberendoscopic nasotracheal intubation in a 23-month-old child presenting for neurosurgical treatment of cervical myelopathy resulting from Morquio-Brailsford syndrome. CASE REPORT. A 23-month-old girl (84 cm, 11 kg) with Morquio-Brailsford syndrome presented for surgical decompression and dorsal fusion of the cervical spine. Pre-anaesthetic examination revealed enamel defects, chronic bronchitis, and splenomegaly; the neck was immobilised with a collar. Radiological examinations (X-ray and NMR) revealed narrowing of the atlanto-occipital and atlanto-axial spaces (Fig. 1) and compression of the cervical spinal cord (Figs. 2 and 3). Pre-anaesthetic medication consisted of midazolam juice (4 mg). After establishing intravenous access, atropine (0.5 mg), midazolam (1 mg), and ketamine (10 mg) were administered. A 22 Fr nasopharyngeal airway (Wendl) was lubricated with local anaesthetic gel and introduced into the right nostril; oxygen was administered through a probe to the left nostril. The Wendl-airway was then removed, another 5 mg ketamine was administered, and a 3.5-mm flexible fiberendoscope--over which a 20 Fr armored tube was slipped--was introduced through the right nostril. With the child spontaneously breathing, the glottis was visualised and the fiberscope introduced into the trachea (Fig. 4); 1 mg midazolam and 35 mg ketamine was administered and the endotracheal tube was advanced through the nose into the trachea, utilizing the fiberscope as a guide. The distance between endotracheal tube and carina was assessed endoscopically, the fiberscope withdrawn, and the tube connected to the breathing system. Pulse oxymetric readings were 98% during induction of anaesthesia including endotracheal intubation. Anaesthesia was continued with enflurane, alfentanil, midazolam, and atracurium; 315 min after induction the trachea was extubated and the child discharged to the paediatric intensive care unit. The postsurgical course was uneventful, and the child resumed co-ordinated gait. DISCUSSION. Airway management in patients with mucopolysaccharidoses may be extremely difficult. Recommended methods such as blind nasal intubation are not feasible in small children. Anaesthetic management in children younger than 2 years with Morquio-Brailsford syndrome presenting for cervical spine surgery has not yet been described. Fiberoptically guided nasotracheal intubation is a means of airway management that does not require repositioning of the head and may be performed with the stabilising collar left in place (Fig. 4); preservation of cervical spinal cord integrity may hence be assumed. Analgosedation with ketamine and midazolam allows sufficient spontaneous breathing and--to some extent--maintenance of protective laryngeal reflexes. In conclusion, anaesthetic management of patients with Morquio-Brailsford syndrome is a challenge that is further increased by extending indications for surgical intervention to include infants. With respect to protecting the airway, fiberoptic nasotracheal intubation of the spontaneously breathing child is our method of choice.

[Fiberoptic intubation of neurosurgical patients]

Patients with cervical spine injury presenting with respiratory distress require airway management that does not compromise integrity of the atlanto-occipital joint. Endotracheal intubation by means of direct laryngoscopy is not suitable. The method of choice is nasotracheal intubation of the awake patient, using a flexible fibre bronchoscope. If anatomy or surgical access render the nasal approach impossible, fibre optic intubation can be performed orotracheally, utilising specific technical aids. Flexible fibrescopes are available in different sizes (length and diameter): selection is base on the patient's anatomical requirements. Aids to orotracheal intubation are constructed with a bore wide enough to accommodate an endotracheal tube, and a face mask equipped with an extra intubation port allowing introduction of an endotracheal tube, slipped over a fibrescope. Premedication of the patients consists of an orally administered benzodiazepine. Topical anaesthesia and vasoconstriction of the nasal passages are achieved by cocaine (5-10%), or a local anaesthetic, combined with a vasoconstrictor. The selected nostril is prepared by means of introducing a nasopharyngeal airway, which--lubricated with xylocaine gel and left in place for few minutes--widens the nostril and facilitates passage of the endotracheal tube. Through the other nostril, oxygen is administered. Systemic analgo-sedation is strictly limited to fentanyl, 0.1 mg i.v. Topical anaesthesia of the larynx and cranial trachea is achieved by xylocaine, 2%, administered under direct vision through the instrumentation channel of the fibrescope.(ABSTRACT TRUNCATED AT 250 WORDS)

Deliberate arterial hypotension does not reduce intraocular pressure in pigs

Among the accepted advantages of general anesthesia in ophthalmic surgery is improved control of intraocular pressure (IOP). Although standard textbooks advocate deliberate arterial hypotension to facilitate intraocular surgery by reducing IOP, scientific proof of such an effect is lacking. The authors investigated effects of induced arterial hypotension on IOP in an anesthetized porcine model. Forty-two piglets were anesthetized with piritramide, were placed in the prone position, and had the anterior chamber of one eye punctured with a small Teflon cannula to measure IOP. Six pigs were used in a pilot study to establish dose-response relationships for the hypotensive agents; 36 pigs were randomly allocated to one of three groups (n = 12) to receive nitroprusside, adenosine, or isoflurane to reduce mean arterial pressure (MAP) by 50%. Measurements were made after initial stabilization of hemodynamic variables and IOP (control), when a stable MAP of 0.5x control was maintained for 10 min or longer, and after return of MAP to a posthypotensive steady state. The median of differences between time intervals was analyzed statistically for all variables. Nitroprusside and adenosine produced hyperdynamic hypotension (cardiac index increased); isoflurane-induced hypotension was hypodynamic. Control IOPs were 12.9, 12.5, and 11.1 mmHg in the nitroprusside, adenosine, and isoflurane groups, respectively. Median change in IOP during hypotension was -1.5, +1.5, and 0 mmHg in the nitroprusside, adenosine, and isoflurane groups, respectively. The IOP during adenosine-induced hypotension was significantly higher than that during either nitroprusside- or isoflurane-induced hypotension. Return of MAP to control levels was frequently associated with intraocular rebound hypertension when arterial hypotension had been induced with adenosine or nitroprusside.(ABSTRACT TRUNCATED AT 250 WORDS)

[A myoclonic seizure during propofol-alfentanil anesthesia?]

Total intravenous anaesthesia with propofol and alfentanil is an established alternative to inhalation anaesthesia for intracranial neurosurgical procedures. Its usefulness has been somewhat overshadowed by reports of seizure-like movements, both during anaesthesia and in the recovery period. These can be related to the use of either anaesthetic agent, but true epileptogenic properties still remain to be demonstrated in man. Opioid-induced rigidity is a well known phenomenon and must not be mistaken for an epileptic seizure. Myoclonic motor activity can be observed even under physiological conditions, e.g. sleep. Almost all anaesthetic agents have been found to produce "epileptic" EEG changes (spikes, polyspikes, spike-wave complexes), but in man these have never been correlated to motor reactions. Propofol's pro- or anticonvulsive action is unclear. While some groups found shortened convulsing times in patients undergoing electroconvulsive therapy with propofol instead of methohexitone, others have reported activation of epileptogenic foci in the EEGs of known epileptic patients. A synergistic effect of propofol and alfentanil in the generation of seizure-like movements cannot be excluded. Whether seizure-like movements indicate a true "epileptogenic potency" of the anaesthetic drugs or are related to other phenomena remains to be studied. Electro-encephalographic monitoring during anaesthesia as well as careful observation and documentation of motor reactions may contribute to elucidation of the problem. We report a case of seizure-like movements during propofol-alfentanil anaesthesia for an elective craniotomy. A 52-year-old patient presented with a history of headaches of increasing frequency. A CT brain scan demonstrated a tumor in the left occipital region.(ABSTRACT TRUNCATED AT 250 WORDS)

[A fatal intraoperative cerebral ischemia following kinking of the internal carotid artery?]

Postoperative neurological deficit may result from ischaemic or hypoxic hypoxaemia. Postural cerebral hypoperfusion may ensue when a pre-existing asymptomatic vascular anomaly in combination with rotation of the head for surgical positioning compromises cerebral blood flow. CASE REPORT. A 30-year-old man was referred for recraniotomy for glioblastoma. Following uneventful induction of anaesthesia, increased diuresis and progressive hypothermia were observed. The postoperative period was complicated by a seizure, followed by apnoea requiring reintubation of the trachea. A CAT scan revealed global cerebral oedema with subtotal compression of the third ventricle. Intracranial pressure was 60 mm Hg as measured by an epidural probe. On the 1st postoperative day clinical and electroneurophysical signs of brain death were observed; the patient underwent organ explantation the next day. PATHOLOGY. Pathological examination revealed pronounced global hypoxaemic lesions and an S-shaped internal carotid artery with intimal proliferation (Fig. 1). The diagnostic conclusion was cerebral ischaemia following carotid occlusion caused by carotid kinking and completed by surgical positioning (rotation of the head). CONCLUSION. Carotid kinking is a rare abnormality, and patients at risk may not be identified preoperatively. Though it is questionable whether this disaster could have been prevented at all, electroneurophysiological monitoring would have been the only early monitoring system capable of detecting diminishing cerebral blood flow. Although a request for routine intraoperative neurophysiological monitoring seems unrealistic at present, it has to be acknowledged that only such monitoring could have provided the information needed to save this patient.

[The seated position in patent foramen ovale?]

Anesthetic management of patients presenting for posterior cranial fossa surgery in the seated position includes detection and treatment of venous air embolism. Atrial positioning of a central venous (cv) line may be verified by either X-ray or an atrial ECG tracing. We report a case where a chest X-ray film proved superior. A 26-year-old white female was scheduled for posterior cranial fossa exploration. A cv line was inserted via the left antecubital vein; the chest X-ray film documented correct positioning of the catheter tip within the atrium but an aberrant course of the superior vena cava. Echocardiography was performed in the induction room and indicated a patent foramen ovale. In view of the risk of paradoxical air embolism, surgery was postponed. Subsequent cardiologic and radiologic examinations revealed a patent foramen ovale and a persisting left superior vena cava draining into a dilated coronary sinus. Surgery was rescheduled and carried out uneventfully in the prone position. This case demonstrates: 1) an advantage of a thoracic-X-ray film compared to atrial ECG tracing as not only the catheter tip position, but also the course of the catheter can be identified; and 2) the usefulness of preoperative screening for a patent foramen ovale in patients scheduled for surgery in the seated position.

[Rectal administration of drugs. Fundamentals and applications in anesthesia]

Rectal administration of drugs has become a standard procedure in clinical anesthesia, most notably for anorectal induction in children. Limitations of this method include low bioavailability, a wide scatter of pharmacokinetic and pharmacological results, and poor predictability of the clinical effect in any particular patient. Historically, the rectal route has been used for the administration of smoke ("fumigation") for resuscitation and various other purposes. An ether boiler for rectal application was developed by Pirogoff as early as 1847. The pharmacokinetics of rectally administered drugs are determined by the anatomical properties of the rectum and, owing to interindividual variance, this adds to the inconsistency of absorption. Aspects that can be better controlled include the drug preparation and the vehicle, with hydrophilic solutions resulting in improved absorption. Larger volumes such as are associated with lower concentrations increase the bioavailability by enlarging the mucosal surface in contact with the drug. In contrast to the hypothetical assumption that hepatic circulation may be circumvented--thus avoiding first-pass metabolism--by direct venous drainage from the rectum into the systemic circulation via the vena cava, it has been shown that hepatic clearance is the main factor affecting bioavailability. This may be due to blood flow through anastomoses interconnecting the superior, medium and inferior rectal venous systems. Resorption from the rectum is also determined by physicochemical properties of drugs. According to the pH-partition hypothesis, only the non-ionized moiety of a compound will be available for transmucosal diffusion. The degree of ionization is a function of the local (or microclimate) milieu pH and pKa of the drug; the former is close to neutral in adults but alkaline in most children. Adsorption of feces, intraluminal degradation by microorganisms, metabolism within the mucosal cell, and lymphatic drainage do not significantly affect the fate of rectally administered drugs. In clinical practice, the rectal administration of methohexital and midazolam is an established method of premedication or induction of anesthesia in children; so far, midazolam appears to be associated with fewer complications. Ketamine has been shown to be as effective and as quick-acting as methohexital, but at least in one study its use as sole induction agent was associated with respiratory distress in some cases. However, painful diagnostic or therapeutic procedures in children may be indications for the rectal administration of ketamine. Early trials with rectally administered etomidate have been abandoned since its implication in suppression of cortisol synthesis. Narcotic analgesics in a hydrogel vehicle are effective in adult pain management.(ABSTRACT TRUNCATED AT 400 WORDS)

[Anaphylactoid reaction to a non-ionic roentgen contrast medium in general anesthesia]

The occurrence of adverse reactions is decreasing since the introduction of non-ionic contrast media. Anaphylactoid reactions during general anaesthesia are rare and hitherto only documented with the administration of ionic compounds. We report an episode of hypotension, tachycardia, bronchospasm and urticaria following application of a non-ionic contrast medium (Iopamidol) during isoflurane anaesthesia. We conclude that a combinent use of anaesthesia and non-ionic contrast media does not guaranty protection from anaphylactoid reactions to iodinated radiopaque compounds.

[The effect of fresh gas flow on the minute volume of anesthesia ventilators with a gas reservoir]

The tidal volume (TV) delivered by conventional anesthesia ventilators is dependent on fresh gas flow rate (FGF). When FGF is reduced, the TV declines; this must be corrected by increasing the ventilator bellows excursion. In addition, the falling bellows produce a negative pressure during the expiratory phase, which may result in positive negative pressure ventilation (PNPV). We have measured the performance of three ventilators: AV 1 (Dräger), VIVOLEC (Hoyer), and ELSA (Engström) that are equipped with a reservoir bag supplied with fresh gas and from which the bellows is filled. METHOD. Two breathing bags with a corrugated tube of 1 m length were connected to a Y-piece to simulate clinical conditions. Starting from 10 l/min, FGF was decreased by 1 l at a time down to 1.0 l/min. Measurements were made at each level of FGF and also at 0.5, 0.3, and 0.2 l/min using a constant inspiration: expiration ratio of 1:2, displacement of the bellows of 700 ml/breath, and a rate of 10/min. Measurements of peak pressure, positive end-expiratory pressure (PEEP), and delivered TV were made at each FGF setting. RESULTS. The course of TV-dependence on FGF is shown in Fig. 1, that of peak inflation pressure and PEEP in Table 1. Reducing FGF had no effect on TV and inflation pressure with ELSA. VIVOLEC lost 17% of the initial TV when FGF was reduced to 0.2 l/min. By closing the relief valve, the loss of TV could be reduced to 4.5%. AV 1 lost about 10% of the initial TV when FGF was reduced to 0.5 l/min. Peak pressure and PEEP were lower with minimal flow. The reservoir bag collapsed when the plateau pressure exceeded 18-20 mbar. CONCLUSIONS. The TV delivered by the ventilators studied was found to reflect closely what had been preset on the bellows displacement scale, within a range of less than or equal to 17%, irrespective of FGF. Hence, the problem of FGF-dependence of TV is largely negated in anesthesia ventilators equipped with a reservoir bag. With ELSA, there was no loss of TV even under minimal flow conditions. VI-VOLEC (with the relief valve closed) and AV 1 had a loss of less than 10% of the initial TV. Adding a reservoir bag to anesthesia ventilators is an effective method of guaranteeing a TV independent of FGF. The three ventilators tested here proved suitable for minimal-flow anesthesia.

[Surgical accidents during repair of intracranial aneurysms]

The need to discuss incidents encountered during cerebral aneurysm surgery--as well as techniques and results--is increasingly accepted. Single incidents, however, do not allow for general conclusions; we wish to present 5 cases, analysis of which, we believe, is likely to elucidate the trouble of diagnosis and intraoperative decision making.

[A universally applicable mask attachment for fiberoptic intubation. The Mainz Universal Adapter]

The problems associated with "difficult airways" have almost subsided since the introduction of flexible fiberoptic bronchoscopes for tracheal intubation. Limitations of this technique persist with uncooperative patients, children and infants. We describe an universally applicable connector for fiberoptic intubation during mask ventilation, which fits all masks with a 22-mm connector, including the Rendell-Baker-Soucek type. This technique is of utmost value when a "difficult airway" is encountered only subsequent to induction of anesthesia, especially if nondepolarizing muscle relaxants have been administered. The device makes intubation possible with all sizes of fiberoptic bronchoscopes. The prerequisites for application of this technique include an airway that will be maintained by mask ventilation.

Rectal pH in children

In an attempt to establish normal values for rectal pH in children, we have measured pH in 100 paediatric patients. Measurement of rectal pH was performed in 25 infants and 75 children (27 girls and 73 boys) using a monocrystalline antimony electrode. Rectal pH was 9.6 +/- 0.9 (mean +/- SD, range 7.2 to 12.1) and was independent of sex, age and nutrition. This wide range of rectal pH values offers a possible explanation for the widely scattered bioavailability of drugs administered by the rectal route. Mean rectal pH was considerably higher than that reported for adults; this unexpected alkalinity should be taken into account, when drug formulations are considered for rectal administration in children.

[Cannulation of the internal jugular vein using 2 ultrasonic technics. A comparative controlled study]

The internal jugular vein (IJV) is a common access route to the central venous system. Anatomical landmarks (group I) are normally used for localization of the IJV. We have compared this method with two other methods based on ultrasonic waves to identify the IJV and the carotid artery (CA) (even in atypical positions). We employed an ultrasound Doppler device in group II and a real-time ultrasonograph in group III. Central venous catheters were placed into the right IJV by the Seldinger technique. The IJV could be located in all patients with both ultrasound methods, but the course of the IJV could only be identified by ultrasonography. For this reason, the direction of the IJV was classified as "typical" in 80% of group I, in 85% of group II, but in only 45% of group III. No intergroup differences were found with respect to the number of punctures (mean value 1.6 +/- 0.83) and the incidence of complications. The time required to locate the site and direction of puncture increased with technical sophistication. There was, however, no difference in the total time for catheter placement, because puncture was performed faster when aided by sonography. In four patients in groups I and II, in whom attempts to puncture the IJV had not been successful, this could subsequently be achieved with ultrasonographic aid. One patient (group I) displayed a hematoma following inadvertent puncture of the CA. In one patient in group II the IJV and CA could not be distinguished as one was overlying the other. The echocamera provided improved localization of the IJV and the CA in comparison with the Doppler ultrasound.(ABSTRACT TRUNCATED AT 250 WORDS)

[An activated charcoal filter for eliminating volatile anesthetics. A contribution to the management of malignant hyperthermia]

Anesthesia machines may not be contaminated with anesthetic vapors when a patient susceptible to malignant hyperthermia (MHS) is to be anesthetized. A clean machine may not always be available, and recommended protocols for preparing a contaminated machine are cumbersome and time-consuming. We suggest the use of an activated charcoal filter that is easily assembled from spare parts available in many anesthesiology departments (Fig. 2). It consists of an HME container (Servo-Humidifier 150, Siemens-Elema), a sieve set from an anesthesia circuit (7a/8-ISO, Dräger, Lübeck), and grained activated charcoal (2.5 mm, Merck, Darmstadt). All parts are autoclavable. The filter adsorbs anesthetic vapors quantitatively (Fig. 3) without affecting humidity, nitrous oxide concentration, or circuit resistance. Storage of such a filter may obviate the need to keep a clean anesthesia machine available for MHS patients.

[The washout behavior of isoflurane following balanced anesthesia and its effect on postoperative oxygen supply]

Few studies have described the pharmacokinetics and pharmacodynamics of isoflurane (I) during the postoperative recovery room stay. In this study the influence of balanced anesthesia with I on the postoperative course was investigated by studying pulmonary washout of I and its effect on arterial oxygen saturation. METHODS. Following institutional approval and informed consent, 50 patients (ASA I and II) scheduled for lateral fenestration for intervertebral disc herniation participated; all had no previous record of cardiopulmonary problems. Induction of anesthesia was achieved with intravenous alcuronium 0.03 mg/kg, fentanyl 0.003 mg/kg, thiopental 5 mg/kg, and succinylcholine 1.5 mg/kg followed by alcuronium 0.09 mg/kg before changing to the prone position. Anesthesia was maintained with controlled ventilation in a rebreathing system (fresh gas flow FGF) = 3.01/min, FIO2 = 0.3 in N2O, plus 0.8 Vol.-% cIet = 1.3 MAC). Near the end of surgery I was discontinued and IGI was increased to 61/min O2 for 10 min. Patients then returned to breathing ambient air. Extubation was carried out as soon as a minimum tidal volume of 400 ml was obtained. End tidal I concentration (cIet; Vol.-%) was measured by infrared absorption (Normac, Datex) and O2 saturation by pulse oximetry (Biox III, Ohmeda). Datum point of the pulmonary I-washout curve was the mean end-tidal I concentration obtained 15 min before terminating I (cIAW). Effects of duration of anesthesia, Broca index, and amount of I administered (tidal volume x inspiratory I concentration x min; ml) on I-washout were assessed. A pulse-oximetric O2 saturation of less than 90% was regarded as hypoxygenation. RESULTS. Mean duration of anesthesia for both males and females was 85 +/- 25 min, mean Broca index 102 +/- 13. The amount of I administered with the inspiratory volume was 5.661 +/- 2.194 1 I (1.0 +/- 0.4 Vol.-%). Mean I-regression (Fig. 3) was 236 x 10(-5) Vol.-%/min (Figs. 1 and 3). Mean I-washout 60 min after extubation was 44.6 +/- 15.2% of the administered amount. Adequate spontaneous breathing began a mean of 17 min after the end of I exposure, corresponding to 20% cIet of washout. All patients were extubated after a mean of 22 min at a mean etI of 17% of washout. After extubation, pulse oximetry indicated hypoxygenation in 18 patients (= 36%) during 2 periods (Fig. 4): (1) at a mean cIet of 0.1 Vol.-% (= 15% of washout) after a mean of 8 min; and (2) at a mean cIet of 0.08 Vol.-% (= 12% of washout) a mean of 19 min following extubation. Further episodes of hypoxygenation occurred as much as 40 min post-extubation. (ABSTRACT TRUNCATED AT 400 WORDS)

Cardiovascular effects of vecuronium, atracurium, pancuronium, metocurine and RGH-4201 in dogs

The effect on the cardiovascular haemodynamic status of five neuromuscular blocking drugs, RGH-4201, vecuronium, atracurium, pancuronium and metocurine, was studied in five conditioned foxhounds anaesthetised with fentanyl. Changes in heart rate, mean arterial blood pressure, central venous pressure, mean pulmonary artery pressure, pulmonary capillary wedge pressure, and cardiac output were recorded at 2, 5, 10, 20 and 30 min after administration of the drugs. From these, stroke volume, systemic vascular resistance and pulmonary vascular resistance were calculated. Administration of RGH-4201 was followed by a pronounced increase in heart rate, accompanied by an increase in cardiac output and a decrease in systemic and pulmonary vascular resistance. Metocurine and pancuronium resulted in a decrease of right and left filling pressures and systemic-/pulmonary vascular resistance. Changes after atracurium, vecuronium and metocurine were minimal. It is concluded that RGH-4201 causes major alterations in the cardiovascular haemodynamic status in dogs anaesthetised with fentanyl when compared to vecuronium, atracurium, metocurine and pancuronium. With respect to cardiovascular stability, atracurium and vecuronium offer advantages.

[Anesthesia and intraocular pressure]

General anesthesia has been in use for ophthalmic surgery since 1847. The subsequent predominance of local anesthetic techniques made ophthalmic anesthesia the "Cinderella of anesthesia services" until its clinical and scientific rehabilitation in the second half of this century. Precise control of intraocular tension is an accepted advantage of general anesthesia. The exercise of such control requires understanding of intraocular physiology and the effects exerted by anesthetic techniques. Hence, the impact of anesthetic drugs on intraocular pressure (IOP) must be considered when ophthalmic surgery is to be carried out under general anesthesia. Intravenous anesthetics and volatile agents reduce IOP, with the possible exception of ketamine. Underlying mechanisms include a direct effect on cerebral IOP control centers and indirect effects mediated through the balance between production and drainage of aqueous humor, general circulation and ocular muscle tone. IOP is likely to be elevated during induction and recovery. Currently suggested measures to prevent the increase in IOP associated with laryngoscopic tracheal intubation facilitated by succinylcholine include oral premedication with clonidine, intravenous administration of lidocaine 3 min prior to laryngoscopy, and anesthetic induction with propofol or narcotics. Non depolarizing neuromuscular blocking drugs either do not affect IOP or produce a slight decrease; depolarizing muscle relaxants increase IOP. It remains controversial whether this effect, which is pronounced with succinylcholine, may be reliably abolished by any concomitant medication. The new competitive relaxants atracurium and vecuronium provide stable conditions with respect to IOP and systemic circulation, combined with a rapid onset and intermediate duration of action.

[Risks of premedication with benzodiazepines exemplified by a case of asphyxia caused by flunitrazepam]

Oral premedication with benzodiazepines is well established in clinical anaesthesia. Appreciation of the specific pharmacodynamic profile of available drugs suggest individual prescription for certain groups of patients. We report a case of severe respiratory depression following oral premedication with flunitrazepam 1 mg in a patient with intracranial neoplasma. With respect to this complication and a review of the literature we suggest administration of short acting benzodiazepines with pronounced anxiolytic and moderate sedative properties (lormetazepam type) for neurosurgical patients.

[Undesirable effects following the local injection of ornipressin during general anesthesia: can the risk be lessened? A prospective study]

Complications associated with local infiltration of ornithine-8-vasopressin (O-8-V) during general anesthesia (GA) are documented. Severe and extremely severe complications range around 20%; fatalities have been reported. The incidence of complications is associated with age, pre-existing cardiovascular or pulmorespiratory disease, and dosage administered. In a prospective study, we investigated 169 patients following a standardized protocol. Maximum dosage was 2 IU, diluted to 0.25 IU/ml in 0.9% saline. Patients with cardiovascular or respiratory disease and those below 1 or above 50 years of age were excluded. GA consisted of tracheal intubation and controlled ventilation with enflurane in N2O/O2 and intravenous fentanyl. Cardiovascular monitoring was by ECG with arrhythmia detection, plethysmography, and oscillometric - in some patients intraarterial - blood pressure measurement. Ventilatory monitoring included respiratory rate, tidal volume, inspiratory and expiratory O2 concentrations, capnometry, and end-tidal enflurane concentration. Local infiltration of the oral soft tissues with O-8-V was performed after a steady-state of anesthesia was achieved and 20 min before commencement of surgery. No severe or extremely severe complications or arrhythmias were observed. A moderate increase in blood pressure was seen in 43% of patients; in 10% this increase was 30-70 mmHg (systolic and/or diastolic). For data analysis, patients were allocated to 4 groups according to the dosage of O-8-V administered. Systolic and diastolic pressures increased to above control in all groups; however, no inter-group differences were found for blood pressure or heart rate. It is concluded that the risks associated with local infiltration of soft tissues with O-8-V during GA can be attenuated by a protocol such as the one established for this prospective study.(ABSTRACT TRUNCATED AT 250 WORDS)

[Effect of muscle relaxants on intraocular pressure]

Since general anesthesia is being used increasingly in ophthalmic surgery, the effects of anesthetic drugs on intraocular pressure (IOP) have to be considered. Competitive neuromuscular blocking drugs either do not affect IOP or produce a slight decrease. Depolarizing muscle relaxants increase IOP. This effect, which is pronounced with succinylcholine, cannot be reliably prevented by any concomitant medication. The new competitive relaxants atracurium and vecuronium provide stable conditions with respect to IOP and systemic circulation, combined with fast onset and intermediate duration of action.

'Anestheticography': on-line monitoring and documentation of inhalational anesthesia

The safe practice of inhalational anesthesia requires control over the amount of volatile anesthetic delivered to the patient. With minimal fresh gas flow this is facilitated by continuous monitoring and recording of the agent's concentration ('Anestheticography'). Alterations brought about by routine clinical maneuvers become visible. We recorded the course of the inspiratory and expiratory concentration of volatile anesthetic (Isoflurane) by infrared absorption and a trend recorder. Changing the carrier gas composition during high flow from 75% to 25% nitrous oxide in oxygen resulted in a 10% increase of the inspiratory isoflurane concentration. Activating the oxygen bypass or exchanging the soda lime canisters was followed by a prolonged disturbance of concentrations, most pronounced with minimal flow. Initiating emergence by closing the vaporizer during minimal flow led to a slow decrease in concentration whilst at a flow of 61/min the inspiratory isoflurane concentration rapidly decreased to subanesthetic levels. Insertion of a charcoal filter into the inspiratory limb of the breathing circuit immediately dropped the inspiratory concentration to undetectable levels. 'Anestheticography' is a useful means of monitoring and documentation of inhalational anesthetic. With the use of a charcoal filter all advantages of minimal flow anesthesia can be realized throughout the entire anesthetic, including emergence.

Prolonged anaesthesia with isoflurane and halothane. Effects on hepatic function

Hepatic function was assessed pre-operatively and on the first and sixth postoperative days in 40 healthy patients who underwent prolonged maxillofacial surgery with isoflurane or halothane anaesthesia. No major changes were observed in hepatic enzymes or bilirubin. One-stage prothrombin time and Factor VII concentrations decreased on the first postoperative day and this change was more pronounced in the halothane group. The results support the use of isoflurane rather than halothane for prolonged anaesthesia in respect of the synthesising function of the liver.