Comparison of the transcutaneous oxygen and carbon dioxide tension in different electrode locations during general anaesthesia

BACKGROUND AND OBJECTIVE

The best place for the electrode of transcutaneous measurement of oxygen tension (tcPO2) and carbon dioxide tension (tcPCO2) during general anaesthesia was investigated in three different locations.

METHODS

Fifteen patients for major abdominal surgery in the supine position were studied. The electrode of the TCM4 (Radiometer, Copenhagen, Denmark) was put on the chest, upper arm or forearm. TcPO2, tcPCO2, end-tidal carbon dioxide tension (etCO2), percutaneous oxygen saturation (SaO2), arterial oxygen tension (PaO2 ) and arterial carbon dioxide tension (PaCO2) were simultaneously measured at four different etCO2 concentrations and inhaled oxygen percentages and the location of the electrode was changed to other places to repeat the same measurement. In total, 12 measurements for each patient and 60 measurements for each place were performed.

RESULTS

TcPO2 correlated better than SaO2 (R2 = 0.58) with PaO2 (R2 = 0.76), and tcPCO2 correlated well with PaCO2 (R2 = 0.76) and etCO2 (R2 = 0.74) when the electrode was put on the chest, while not on the upper arm or forearm (R2 < 0.5). However, limits of agreement were too big to use tcPO2 (bias, -67.9; limits of agreement, 16.5, -152.3) and tcPCO2 (bias, -0.47; limits of agreement, 8.7, -9.64) as surrogate measures of PaO2 and PaCO2, respectively even when the electrode was put on the chest.

CONCLUSIONS

When the electrode was put on the chest, tcPO2 and tcPCO2 might be available as non-invasive monitors of oxygenation and CO2 status during general anaesthesia, while the absolute values were not interchangeable with PaO2 and PaCO2, respectively.

Étude clinique du masque laryngé en pédiatrie. Comparaison du LMA–classic et du LMA–ProSeal taille 2 et 2,5

OBJECTIVES

To compare the Classic laryngeal mask airway (MLC) and the ProSeal LMA (MLP), size 2 and 2.5 in terms of ease of insertion, leak pressure and side effects during insertion and extraction in the recovery room.

STUDY TYPE

Randomised prospective.

MATERIAL AND METHOD

All children between 10 and 30 kg scheduled for general anaesthesia with laryngeal mask (ML) were included. There was no imposed protocol for the anaesthesia. The ML size was determined according to the child's weight. The MLC was inserted using the standard technique. The MLP was inserted following the recommendations, with or without the handle according to the operator's choice. The data analysed were: insertion type, ease of insertion of the mask, of the nasogastric tube (SG), number of attempts of mask insertion, complications, gastric leaks.

RESULTS

One hundred (and) twenty children were included. There was no statistical difference in terms of difficulty of insertion, number of failed attempts, leak pressure or side effects. The use of the handle did not make insertion easier. Insertion of a nasogastric tube was possible in 92% cases.

CONCLUSION

MLP is as easy to use in children as the MLC. MLP has the advantage of allowing rapid access to the stomach. It seems that the MLP is safer since its correct position is confirmed by easy gastric tube insertion.

[Oropharyngeal ulcers following anaesthesia with the laryngeal tube S]

We report a case of acute tongue and uvula ulcerations consecutive to the use of a laryngeal tube Sonda (LTS) for airway management. The LTS was used during general anaesthesia for hysteroscopy and resection of endometrial hyperplasia. No trouble occurred during LTS insertion and anaesthesia. Symptomatic treatment provided complete resolution within a few days. This event points out the potential risk of more serious lesions.

Keuskamp and the Amsterdam Infant Ventilator

At the First International Symposium on the History of Modern Anaesthesia (1982), Professor Keuskamp mentioned that the introduction of breathing machines for lung ventilation during operations had taken over 'the tiresome handwork of ventilation'. This paper traces some aspects of Keuskamp's professional career and his role in the development of the Amsterdam Infant Ventilator. In 1974, Urban and Weitzner from the State University of New York reported that the ventilator was a reliable and effective constant-volume paediatric ventilator. Other clinicians from the United States and Europe echoed this satisfactory clinical evaluation. At present, this paediatric ventilator is still in use for the initial ventilation of small infants and for the mechanical ventilation of different animal species in a variety of experimental settings.

An insidious failure of an oxygen analyzer

We present a case of oxygen analyzer malfunction diagnosed by the failure of the patient to adequately breathe oxygen as measured by end-tidal oxygen concentration. A warning icon, compliant with international standards, was not noticed at the time by those involved in the patient's care. The role of effective medical device user interface design is discussed.

The laryngeal tube

The laryngeal tube (VBM Medizintechnik, Sulz, Germany) is a relatively new extraglottic airway, designed to secure a patent airway during either spontaneous breathing or controlled ventilation. In this review article, we have assessed the potential role of the laryngeal tube during anaesthesia and during cardiopulmonary resuscitation. There are four variations of the laryngeal tube: standard laryngeal tube, disposable laryngeal tube, laryngeal tube-Suction II and disposable laryngeal tube-Suction II. The design of the device has been revised several times. Insertion of the standard laryngeal tube is as easy as with the laryngeal mask airway classic. The laryngeal tube may provide a better sealing effect than the laryngeal mask. The incidence of complications with the two devices is similar, although the laryngeal tube may require more re-adjustments of its position to obtain a clear airway. Compared with the ProSeal laryngeal mask, the laryngeal tube may be less effective. The efficacy of the standard laryngeal tube is unclear, particularly in patients breathing spontaneously or in children. The efficacy of the laryngeal tube Suction-II and disposable devices is also not clear. From the limited number of studies and reports available, it can be concluded that the laryngeal tube is potentially useful in maintaining a clear airway during anaesthesia and cardiopulmonary resuscitation. In addition, the device may be useful as an aid to tracheal intubation.

Bispectral index system (BIS) monitoring reduces time to extubation and discharge in children requiring oral presedation and general anesthesia for outpatient dental rehabilitation

PURPOSE

Pediatric oral rehabilitation patients who receive presedation with oral Versed and general anesthesia (GA) occasionally experience prolonged sedation and delayed discharge. The Bispectral Index System (BIS) is an EEG monitor that measures the anesthesia level. The purpose of this study was to compare the effects of monitoring the BIS to not monitoring the BIS on time from discontinuation of GA to extubation and to discharge.

METHODS

Twenty-nine children were enrolled. BIS was monitored from admission until discharge. Each child received 0.7 mg/kg of oral Versed. In the operating room, GA with sevoflurane (IH), rocuronium 1 mg/kg (IV), fentanyl 1 microg/kg (IV), and ondansetron 0.15 mg/kg (IV) was administered. Randomly, in half the patients, the anesthesiologist maintained the level of anesthesia and BIS by adjusting sevoflurane. In the rest, the anesthesiologist did not know BIS. The time from turning off sevoflurane to discharge was compared.

RESULTS

Group 1 patients were extubated 5+/-2 minutes sooner than group 2 patients (P=.04). The post-anesthesia care unit stay for group 1 patients was 47+/-17 minutes compared to 63+/-17 minutes in group 2. (p=0.02).

CONCLUSIONS

Monitoring anesthesia with BIS promotes earlier extubation and discharge for pediatric dental patients who receive oral Versed and sevoflurane GA.

Increases in bispectral index lead to interventions that prevent possible intraoperative awareness

In this case a woman underwent a cervical laminectomy with a total i.v. anaesthesia technique and during her care two problems occurred with propofol delivery. In both cases, bispectral index increases alerted caregivers to the decreased propofol delivery and allowed them to make corrections in a manner timely enough to prevent the occurrence of awareness during anaesthesia. The case illustrates how intraoperative processed electroencephalographic monitoring may decrease the incidence of recall of awareness following surgery.

Hubert Ingham Clements: a pioneer of Australian anaesthesia

Hubert Ingham Clements was an inventor, designer and engineer who manufactured many pieces of apparatus for use in the scientific and medical practice, particularly in the field of anaesthesia from 1917 when he designed and manufactured suction pumps and anaesthetic machines. His products were ingenious, light and portable where desirable, but sturdy, extraordinarily reliable, of low maintenance and high performance. His contribution to the specialty of anaesthesia is acknowledged.

The Marrett apparatus: is hospital anaesthetic equipment compatible with field use?

Major Rex Marrett in 1945 was commissioned to design an anaesthetic apparatus for field use to replace the Field Pattern Boyle's apparatus in use during the Second World War. His design was both elegant and avant garde and was capable of being used with all agents and circuitry then in current use. It was an economical machine with vaporizer in circle and carbon dioxide absorption as its chief mode of operation. The equipment and its later developments are described. Eventually the desire for knowing volatile agent concentrations led to its decline with production ceasing in 1976.

Vivian Richard Ebsary, A.M. biomedical engineer, inventor, philanthropist

Vivian Ebsary was an inventor, designer and manufacturer of varied pieces of medical equipment, particularly those involving pumps. These included hypothermia machines and the heart-lung cardiopulmonary bypass machines used in Australian and New Zealand hospitals from the mid 1950s until well into the 1970s. Ebsary also designed and manufactured anaesthetic machines, a hyperbaric unit, scoliosis implant equipment, a chairlift and many other devices for use in the general community. This paper presents an overview of his life's involvement with medicine and medical technology in Australia.

Norman R. James F.F.A.R.A.C.S., a pioneer of high quality anaesthesia in Australia

Dr Norman R. James was a multi-talented, highly accomplished clinician, teacher and innovator broadly recognized on three continents. In the United Kingdom, he served in London's Emergency Medical Service during World War II and was dubbed "England's foremost exponent of regional anaesthesia". In his native land, he was the first Director of Anaesthetics at The Royal Melbourne Hospital with many innovations to his credit including a serious effort to reform anaesthetic practice in Australia. Dr M. T. "Pepper" Jenkins, the charismatic founder of anesthesiology at the University of Texas Southwestern Medical School, recruited him to Dallas in 1960, where he taught the art and science of anesthesiology at Parkland Memorial Hospital until his retirement in 1974. He died in 1987 and is buried in Winnsboro, Texas. A brief story of his life and career follows.

[General anesthesia outside the operating room in patients with Pierre-Robin syndrome]

Anesthesiologists are increasingly asked to involve in administering general anesthesia outside the operating room for such procedures as computed tomography, magnetic resonance imaging or angiography. Especially, pediatric patients require some kind of sedation or general anesthesia during these procedures. We report general anesthesia outside the operating room in patients with Pierre-Robin syndrome, who are expected to have possible difficult airway. A one-year-old girl and a 16-year-old boy were anesthetized for cardiac catheterization. General anesthesia was given at the angiography room which was located outside the operating room. Anesthesia was induced with oxygen, nitrous oxide and sevoflurane while portable storage unit for difficult airway was prepared including various types and size of laryngoscopes, laryngeal mask airway, fiberoptic intubation equipment and surgical airway access. Fortunately, tracheas were successfully intubated without using special devices, although cautious care during induction was taken. According to development of medical and surgical procedures, it is readily presumed that anesthesiologists will be more often involved in the sedation or anesthesia conducted outside the operating room in future. Anesthesiologists should always ensure enough staffing, proper monitoring and equipment when sedation or anesthesia is conducted outside the operating room, particularly if patients have anesthetic risks.

The C.O.N. apparatus

The C.O.N. apparatus developed in the late 1950s utilised a non-explosive mixture of cyclopropane, nitrogen and oxygen. Its development is described.

Randomised, crossover comparison of the single-use SoftSeal?and the LMA Unique?laryngeal mask airways

We performed a randomised, crossover, single-blind trial among 168 patients, to compare the single-use SoftSeal and LMA Unique laryngeal mask airways in spontaneously breathing adults. Size-3 and -4 laryngeal mask airways, inserted by experienced anaesthetists, performed equivalently for successful first-time placement (148 (91%) vs 155 (96%) for the SoftSeal and LMA Unique, respectively). The SoftSeal was more often rated as difficult to insert (27 (17%) vs 4 (3%); p < 0.001) and was more likely to show evidence of mucosal trauma after the first insertion (14 (10%) vs 5 (4%); OR 1.3 (95% CI 1.3-11.3); p < 0.05). The fibreoptic view of the larynx was better through the SoftSeal (vocal cords not visible in 27 (17%) vs 44 (27%); p < 0.05) and it more frequently provided a ventilation seal at 20 cmH(2)O (93 (59%) vs 62 (39%); OR 2.15 (CI 1.44-3.21); p < 0.001). In contrast to the LMA Unique(trade mark), its cuff pressure did not increase during nitrous oxide anaesthesia (median (IQR [range]) decrease 3 (- 20-23 [-40-94]) cmH(2)O vs increase of 16 (-2-39 [-54-112]) cmH(2)O; p < 0.01). Both devices were equivalent for the success of first-time insertion and performed satisfactorily clinically. There were some performance differences, but either appears suitable for airway management in spontaneously breathing patients.