Use of the flexible fiberoptic laryngoscope

The flexible fiberoptic laryngoscope is an excellent instrument for performing tracheal intubation in patients with abnormal upper airway anatomy. In order to prepare to use the fiberscope for the infrequent patient with a "difficult" airway, the anesthesiologist must initially learn and practice the technique in patients with normal anatomy. Orotracheal intubation with the fiberscope in these patients receiving general anesthesia provides the anesthesiologist with abundant opportunities to become skillful.

Evaluation and management of the difficult airway

Even routine airway management requires specific skills that are best acquired in a controlled setting, before "trial by fire" in an emergency situation. Furthermore, recognition of a potential difficult airway and appropriate preparation prior to initiating airway intervention are critical steps in avoiding airway catastrophes in the intensive care or emergency setting. Familiarity with a difficult airway algorithm and various alternate techniques for endotracheal intubation is a mandatory requirement for all practitioners involved in airway management, and should be incorporated in critical care curricula. Critically ill patients, by nature, are at risk for complications during manipulation of the airway, and may have a higher incidence of adverse reactions to anesthesia-inducing drugs and muscle relaxants. In general, "less is more" in the intensive care unit, and techniques that preserve spontaneous ventilation during airway interventions are desirable, particularly in patients with anticipated difficult airways. All intubating sites should have a portable storage unit for equipment for managing difficult airways readily available. Correct ETT placement always should be verified by detection of exhaled CO2, and by chest radiography if prolonged intubation is planned.

A method of costing anaesthetic practice

This paper identifies the main factors involved in the cost of elective general anaesthetic practice. The costs of anaesthesia were divided into overheads and running costs, which are sensitive to the duration of anaesthesia, and fixed costs which are incurred by each patient but are not sensitive to the duration of anaesthesia. The overhead costs consisted of salaries, capital equipment and maintenance costs. The overhead cost of a consultant anaesthetist combined with a technical assistant's salary, monitoring equipment and anaesthetic machine was estimated at 45.05.h-1 pounds (using 1993 salary scales and prices). The fixed costs of pre-operative assessment and nursing care in recovery were the same for all patients, 20.60 pounds per patient. For the majority of anaesthetics the combined cost of the anaesthetist, overheads and postoperative care was about 70% of the total cost, the remainder being the running costs which included drugs, anaesthetic gases, vapours, intravenous fluids, sterile equipment and other disposable items. Four sample anaesthetics were costed in two ways: both methods used the same overhead and fixed cost per patient but one added the cost of all the individual drugs and consumables used, whereas the other grouped these together using a charge sheet which can be computerised and used prospectively to cost anaesthesia. There was close agreement between the costs derived with the two methods. The cost of a 30 min delay in the start of an operating session was 27.30 pounds (anaesthetist, assistant and nurse salary (9.50.h-1 pounds)) which is more than the cost of 2 h of propofol infusion anaesthesia.(ABSTRACT TRUNCATED AT 250 WORDS)

General anesthesia by mask with spontaneous ventilation during brief laparoscopic inspection of the peritoneum in children

We prospectively examined the cardiorespiratory changes seen with general anesthesia by mask with spontaneous ventilation during brief laparoscopic inspection of the peritoneum in children. Anesthesia consisted of isoflurane in 50% oxygen/air and a caudal epidural block. The patient was allowed to ventilate spontaneously without assistance. Baseline measurements of heart rate, systolic/diastolic blood pressure (BP), end-tidal CO2 (PETCO2), tidal volume, respiratory rate, and oxygen saturation were recorded every 1 min for 5 min before the start of laparoscopy and every minute during the laparoscopic procedure. A total of 20 patients were enrolled in the study, ranging in age from 15 to 80 months (mean 40.8 months) and in weight from 10.5 to 27 kg (mean 15.9 kg). The length of the laparoscopy varied from 3 to 18 min (mean 6.9 min). No significant changes (increase or decrease of 20% from baseline) of heart rate or BP occurred. Oxygen saturation remained at 98%-100% throughout the procedure in all patients. The baseline tidal volume before the start of laparoscopy was 6.27 +/- 1.9 mL/kg and increased to 7.3 +/- 2.2 mL/kg during laparoscopy (p = 0.01). The baseline respiratory rate was 27.7 +/- 7.0 breaths/min and increased to 33.5 +/- 7.2 breaths/min during laparoscopy (p = 0.0001). PETCO2 increased from a baseline value of 37.5 +/- 6.5 to 44.6 +/- 6.8 mm Hg (p = 0.0001). The increase in PETCO2 was 10 or greater in 3 patients and exceeded 50 mm Hg in 3 patients, with a maximum value of 66 torr.(ABSTRACT TRUNCATED AT 250 WORDS)

[Prevention of cross contamination, patient to anesthesia apparatus to patient, using filters]

Concern for cross infections from patient to patient via apparatus is particularly relevant today. There are several ways to prevent patient contamination through anesthetic devices. Although there is no clinical evidence for using one alternative over another and each hospital establishes its own hygienic protocols, we have introduced the systematic use of filters with patients undergoing general anesthesia. We describe the features of filters available on the market and our protocol for their use. The efficacy of a filter depends on whether bacteria or viruses are to be controlled. Filters can be classified into three groups or generations based on mesh quality: 1) heat and humidity exchangers (HHE), with large mesh screens that allow water to pass through; 2) bacterial filters (FHHE), with finer mesh that is permeable to droplets of water and 3) folded membrane filters (FHHE) that are hydrophobic, with very fine mesh that stops water. We describe three basic physical tests (passage of water, passage of smoke and increase of resistance when applied to the patient) for filters to be classified. The ideal filter is hydrophobic and does not increase circuit resistance over the amount specified. Four principles are emphasized in the protocol: 1) the filter forms a part of the patient, not the apparatus; 2) proper placement of the filter is between the patient and the circuit's "Y" piece; 3) the main purpose of the filter is to prevent contamination of the apparatus, and 4) if a hydrophobic filter is used with each patient, the use of a disposable respiratory circuit is not called for.

[Perioperative EEG monitoring: studies of the electrophysiological arousal mechanism]

Electroencephalogram recordings have been advocated for assessment of changes in cerebral function during anaesthesia. Controversy exists on the specificity of EEG parameters indicating depth of anaesthesia, because cortical electrical activity is modulated not only by drugs but also by a variety of exogenous and endogenous stimuli. In clinical practice, EEG measures often fail to accurately predict anaesthetic depth since the effects of nociceptive stimulation on the EEG are still not well defined. Previous reports indicate that in anaesthetised patients sensory stimulation may induce a shift to a dominant EEG frequency with faster waves similar to patterns seen during emergence from anaesthesia under certain circumstances. This electrophysiological arousal (EEG desynchronisation) may be associated with clinical arousal phenomena such as movement and increases in haemodynamic and respiratory activity. However, the mechanism of arousal during emergence from anaesthesia may be quite different from arousal reactions induced by noxious stimulation. Recent studies indicate that surgical stimulation can induce increases in slow wave EEG-activity ("reverse" or "paradoxical" arousal) associated with clinical arousal phenomena. Stimulus related delta patterns also were observed after acoustical or painful stimulation in head injured patients. The occurrence of slow EEG wave patterns may be related to functional blockade of the ascending activating system of the brain stem. In contrast, slowing of the EEG is comparable to EEG changes seen with increasing concentrations of anaesthetics. This indicates the difficulty to discriminate arousal phenomena from drug effects using EEG monitoring alone.(ABSTRACT TRUNCATED AT 250 WORDS)

[Laryngeal mask: a new concept in maintenance of patency of the respiratory tract]

A laryngeal mask is, no doubt, a useful and indispensible device for the majority of adults and children subjected to surgery. Its application is simple and atraumatic, involving the minimal hemodynamic and somatic reactions. A laryngeal mask is a good alternative to facial mask and endotracheal intubation in a great number of clinical situations. Moreover, it provides blind and fibreoptic technique of intubation, though its role in emergency situations is still to be found out. Despite the evident necessity of further investigation, laryngeal masks can be safely used in clinical practice now.

Anaesthetic considerations for magnetic resonance imaging

Magnetic resonance imaging (MRI) has become an increasingly popular non-invasive radiological diagnostic procedure, with several distinct advantages over computerised tomography (CT). The images are produced using a strong (1.5-Tesla) magnetic field and radiofrequency (RF) pulses. Due to the effects of the strong magnetic field, certain groups of patients with implanted ferromagnetic objects and women in their first trimester of pregnancy are precluded from undergoing MRI. While most of the patients undergo MRI awake or with light sedation, few need heavy sedation or general anaesthesia. The problems related to anaesthesia in MRI include the constant presence of a strong magnetic field, the RF pulses and their effect on the anaesthesia machine, monitoring devices, magnetically coded material, and loose ferromagnetic objects. In this article, the current availability of MRI-compatible anaesthesia machine, various monitoring devices, and safe conduct of anaesthesia during MRI for patients of all ages are discussed. In addition, the implications of the strong magnetic field on patient resuscitation inside the MRI suite and the recommended procedure for a successful outcome are outlined.

[Anesthetic and respiratory care for patients undergoing magnetic resonance imaging]

Simple and small ventilators, paraPAC and ventiPAC (pneuPAC) were used for anesthetic and respiratory care of patients undergoing magnetic resonance imaging (MRI), combined with or without MRI-compatible anesthetic machine, Ohmeda (R) Excell 210. These ventilators can be connected to Excell by the addition of a conventional below for ventilator (Ohmeda). The 1.5 tesla room shield type MRI machine (SIGNA, GE) did not interfere with the functions of the ventilator and anesthetic machine placed near the patient. Oscillometric blood pressure monitor (BP-203, Nippon Colin) and a gas and pulse oximetry (RGM, Ohmeda) monitor were used with 6 m extended lines for monitoring in the next room. Pulse oximetry signals were disturbed sometimes only by radiofrequency pulses for 3 to 10 minutes, but a pulse oximeter was one of the most useful monitors. Two representative cases were reported here. These ventilators can be used for almost all MRI cases with or without MRI compatible anesthetic machines.

Cuffed nasopharyngeal tube as 'dedicated airway' in difficult intubation

A cuffed nasopharyngeal airway was used in five cases of difficult intubation, initially to maintain anaesthesia, and subsequently to act as a landmark for the passage of a fibreoptic laryngoscope loaded with a tracheal tube. In all cases, airway patency was well preserved with the device and there were no significant problems with its use. The notion of a 'dedicated airway' for difficult intubation cases is developed. A trouble-free airway will permit time to consider solutions for difficult cases and time for the novice to learn fibreoptic laryngoscopy technique.