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J H Van der Walt

Publications and source records attributed to J H Van der Walt.

14 recordsLinked to original sources
PubMed2000

Computerized tomography of the lungs and arterial oxygen tension studies during apnoea in anaesthetized young lambs.

Computerized tomography (CT) of the lungs and arterial oxygen tension studies were performed during general anaesthesia in an animal model to understand changes in pulmonary atelectasis associated with anaesthesia in children during a 2 min apnoeic period. Six anaesthetized lambs were subjected to three periods of apnoea lasting 2 min each. A series of 10 mm CT transaxial views were taken at three levels of the chest and arterial blood gases were analysed at the start of the apnoeic period (baseline) and again every 30 s during the apnoeic period. The areas of atelectasis were measured using the extended Hounsfield scale. The results confirmed that significant background atelectasis was associated with general anaesthesia as found in adult human studies, but failed to demonstrate any increase in atelectasis during the period of induced apnoea. The decline in arterial oxygen tension in this study could be explained due to simple utilization of oxygen in keeping with physiological principles.

Anesthesia, General↗
PubMed1993

The Australian Incident Monitoring Study. The oxygen analyser: applications and limitations--an analysis of 200 incident reports.

The first 2000 incidents reported to the Australian INcident Monitoring Study were analysed with respect to the role of the oxygen analyser; 27 (1%) were first detected by the oxygen analyser. All of these were amongst the 1256 incidents which occurred in association with general anaesthesia, of which 48% were "human detected" and 52% "monitor detected". The oxygen analyser was ranked 7th and detected 4% of these monitor detected incidents. This figure would have been much higher had the oxygen analyser been correctly used on more occasions. The oxygen analyser detected 10 ventilator-driving-gas leaks into the circuit, 6 hypoxic mixtures due to rotameter settings, 3 inappropriate nitrous oxide concentrations, 2 disconnections and 1 leak at the common gas outlet, and 2 partial and 1 total failure of ventilation. In a theoretical analysis of these 1256 incidents it was considered that the oxygen analyser, used on its own, would have detected 114 (9%), had they been allowed to evolve (3% before any potential for organ damage). In 4 incidents an oxygen analyser gave faulty readings, in 3 caused a leak and in one a total circuit obstruction; 5 incidents were not detected because the alarm had been disabled. Despite the advent of piped gas supplies, failure of gas delivery or delivery of a "wrong" gas mixture still occurs surprisingly frequently in current anaesthetic practice; hypoxic mixtures were supplied on 16 occasions, other "wrong" mixtures on 23 and the oxygen supply failed on 7 occasions.(ABSTRACT TRUNCATED AT 250 WORDS)

Accidents↗
PubMed1993

The Australian Incident Monitoring Study. The stethoscope: applications and limitations--an analysis of 2000 incident reports.

The first 2000 incidents reported to the Australian Incident Monitoring Study (AIMS) were analysed with respect to the role of the oesophageal or precordial stethoscope as a continuous monitor. There were 1099 of the 1256 incidents during general anaesthesia in which one might have been used in this way, but use was reported in only 65 cases (5%), predominantly during paediatric cases. In only one report, a cardiac arrest, was the stethoscope the first to detect the incident. In a theoretical analysis it was considered that the stethoscope, used on its own for continuous monitoring, could have detected 54% of the 1256 incidents (almost 25% before any potential for organ damage), had they been allowed to evolve. However, AIMS data suggest that the actual yield using a stethoscope as a continuous monitor may be much lower than this, and that even the use of a "mobile" stethoscope can not be relied upon to detect oesophageal or endobronchial intubation. These reports confirm that there is limited use of the stethoscope for continuous monitoring in current anaesthetic practice in Australia; it has been superseded by the sophisticated electronic monitors now available. However, in areas with limited resources continuous auscultation with a stethoscope remains a basic requirement.

Accidents↗
PubMed1993

The Australian Incident Monitoring Study. Problems with ventilation: an analysis of 2000 incident reports.

A review of the first 2000 incidents reported to the Australian Incident Monitoring Study found 317 incidents which involved problems with ventilation. The major portion (47%) were disconnections; 61% of these were detected by a monitor. Monitor detection was by a low circuit pressure alarm in 37% but this alarm failed to warn of non-ventilation in 12 incidents (in 6 because it was not switched "on" and in 6 because of a failure to detect the disconnection). Failure of detection was usually with ventilator bellows descending in expiration. Complete failure to ventilate occurred in 143 incidents, most commonly because of a disconnection. Disconnection was associated, in one-third of the cases, with interference to the anaesthetic circuit by a third party and in nearly half with surgery on the head and neck. Leaks affected ventilation in 129 incidents, but in only 19 was ventilation totally lost; leaks associated with seal failure of the absorber were common. Misconnections occurred in 36 incidents, most commonly involving the scavenging system. The frequency of a complete failure to check an anaesthetic machine was greater when an induction room was involved than when only the operating theatre was the site of the incident. These incidents suggest that meticulous checking and monitoring for failure of ventilation, preferably using at least two separate, self-activating systems is highly desirable. The Australian and New Zealand College of Anaesthetists' policy on low circuit pressure alarms, oximetry and capnography is vindicated by these reports.

Accidents↗
PubMed1993

The Australian Incident Monitoring Study. Pneumothorax: an analysis of 2000 incident reports.

Eighteen (1%) of the first 2000 incidents reported to the Australian Incident Monitoring Study (AIMS) involved actual or suspected pneumothoraces; 17 were confirmed. Eleven of the patients were seriously ill beforehand. Four developed tension pneumothoraces, and in 2 incidents (1 tension) the pneumothoraces were bilateral. Nine of the 17 were iatrogenic; 6 (35%) followed neck vein cannulation, and 3 (18%) were surgical complications of tracheotomies. No death was attributed to a pneumothorax. In 8 of the 17 incidents, diagnostic delay or difficulties occurred. Contributing factors identified included urgency, distorted anatomy, failure to check, and haste on the part of the anaesthetist. Desaturation detected by pulse oximetry and hypotension detected by invasive blood pressure monitoring warned the anaesthetist on 2 occasions each. Indications for central vein cannulation or trans-tracheal airway manoeuvres must be firm. Such procedures should always be followed by a closely scrutinised erect chest X-ray as soon as practicable. The possibility of a pneumothorax must always be considered when unexpected cardiorespiratory deterioration occurs.

Anesthesia↗
PubMed1993

The Australian Incident Monitoring Study. Recovery room incidents in the first 2000 incident reports.

Of the first 2000 incidents reported to the Australian Incident Monitoring Study 120 (6%) occurred in the recovery room after general, regional or local anaesthesia. Over two thirds (69%) of these involved the respiratory system, 19% were cardiovascular, 3% involved the central nervous system and 9% were miscellaneous in nature. These recovery room incidents were associated with significantly more adverse outcomes (56%) than incidents in the operating theatre (24%). The types and relative frequencies of these recovery room incidents were similar to those of serious recovery complications in a recent analysis of closed malpractice claims; this suggests that incident monitoring may be useful in the study and prevention of recovery room complications. Over three quarters (77%) of all recovery incidents (and 88% of respiratory incidents) were detected clinically; the remainder were first detected by a monitor. A theoretical analysis showed that over 95% of respiratory events, had they been allowed to evolve, would have been detected by pulse oximetry before organ damage occurred, emphasising the potential importance of pulse oximetry in reducing adverse outcome from any complication in the recovery ward which might be "missed" by clinical observation. The findings of this study underline the importance of having an adequate number of trained recovery nursing staff supported by the availability of a pulse oximeter for each patient at least until the return of protective reflexes and the ability to maintain adequate arterial saturation has been established.

Accidents↗
PubMed1993

The Australian Incident Monitoring Study. Paediatric incidents in anaesthesia: an analysis of 2000 incident reports.

The first 2000 incidents reported to the Australian Incident Monitoring Study (AIMS) were analysed to compare anaesthetic incidents in infants and children with those in adults. Of the 2000, 1790 (90%) involved adults, 151 (7%) children and 56 (3%) infants. Healthy children (ASA I) generated a greater proportion of incidents in this group than adults and infants, emphasizing the need for maintaining the same standards for children in this group as for infants and higher risk groups. The AIMS results are similar to those of the United States (US) paediatric "closed claims" studies; the paediatric subset in both the US study and AIMS made up 10% of the total. Also, in both studies, incidents involving the respiratory and breathing circuit systems accounted for nearly half the problems, and cardiovascular problems and problems with the anaesthetic machine each accounted for 10-14% of incidents. In the AIMS study procedures on the head and neck yielded proportionately more incidents in the infant/child group than in the adult group, as did incidents involving the respiratory and breathing circuit systems. Incidents in the child group were often detected clinically; however, there were no differences between the three age groups in the way monitors were used or performed; hence the same monitoring recommendations apply to all groups. Combined oximetry and capnography would have detected nearly 90% of all applicable problems in the AIMS study and could have prevented nearly 90% of the claims arising from inadequate ventilation in the US "closed claims" study.(ABSTRACT TRUNCATED AT 250 WORDS)

Accidents↗
PubMed1993

The Australian Incident Monitoring Study. Human failure: an analysis of 2000 incident reports.

Information of relevance to human failure was extracted from the first 2,000 incidents reported to the Australian Incident Monitoring Study (AIMS). All reports were searched for human factors amongst the "factors contributing," "factors minimising", and "suggested corrective strategies" categories, and these were classified according to the type of human error with which they were associated. In 83% of the reports elements of human error were scored by reporters. "Knowledge-based errors" contributed directly to about one-quarter of incidents; the outcome of one third of incidents was thought to have been minimised by prior experience or awareness of the potential problems, and in one fifth some strategy to improve knowledge was suggested. Correction of "rule-based errors" or provision of protocols or algorithms were thought, together, to have a potential impact on nearly half of all incidents. Failure to check equipment or the patient contributed to nearly one-quarter of all incidents, and inadequate crisis management contributed to a further 1 in 8. "Skill-based errors" (slips and lapses) were directly responsible for 1 in 10 of all incidents, and were thought to make an indirect contribution in up to one quarter. "Technical errors" were responsible for about 1 in 8 incidents. Analysing the relative contribution of each type of error for each type of problem allows the development of rational preventative strategies.(ABSTRACT TRUNCATED AT 250 WORDS)

Accidents↗
PubMed1987

Oral premedication in children.

Preoperative and postoperative sedation, postoperative analgesia and vomiting were assessed following four different oral premedications in 143 children aged 1-10 years, weighing 10-30 kg, and undergoing elective adenotonsillectomy or inguinal surgery. Diazepam, diazepam combined with droperidol, trimeprazine and trimeprazine combined with droperidol were compared in a double-blind trial in conjunction with a standardised inhalational anaesthetic technique employing an intraoperative narcotic. Trimeprazine produced significantly more preoperative sedation (P less than 0.001) and was associated with enhanced postoperative analgesia (P less than 0.01). The incidence of postoperative vomiting was significantly less in the group receiving trimeprazine (P less than 0.001). The addition of droperidol to diazepam and trimeprazine only marginally improved the performance of those drugs but significantly prolonged postoperative recovery times. This was more marked when droperidol was combined with trimeprazine.

Child↗
PubMed1987

The effect of premedication on the incidence of postoperative vomiting in children after E.N.T. surgery.

The influence of premedication and intraoperative narcotic administration on the incidence of vomiting after E.N.T. surgery was studied over a six-month period in 596 children. A high incidence of vomiting was found after intramuscular papaveretum and hyoscine and after oral diazepam. Oral trimeprazine tartrate was associated with a low incidence of vomiting and was found to have an anti-emetic effect when an opiate analgesic was administered after induction of anaesthesia.

Adolescent↗
PubMed1987

Ergonomics.

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Ergonomics↗
PubMed1984

Reductive metabolism of halothane in children.

The volatile halothane metabolites, 2-chloro-1,1,1,-trifluoroethane and 2-chloro-1,1-difluoroethylene, were identified in the exhaled breath of ten children during halothane anaesthesia. Although there was considerable variation among children in the concentration and time-course of metabolite exhalation, exhaled concentrations of these metabolites were of a similar magnitude to those reported in adults. This result suggests that the lower incidence of halothane hepatitis in children compared with adults is not due to a poor ability to metabolise halothane by the reductive pathway.

Anesthesia, Inhalation↗
PubMed1978

Effect of heating on the osmotic fragility of stored blood.

The effect of incubation at 37 degrees C, 46 degrees C, 47 degrees C and 48 degrees C for 1 h on the osmotic fragility of blood was determined. Blood taken from volunteers into ACD and CPD was examined after 1, 7, 14 and 21 days of storage. In addition, 22-day-old blood stored in CPD was examined. The osmotic fragility was unchanged after incubation at 37 degrees C and 46 degrees C, slightly increased at 47 degrees C and markedly increased at 48 degrees C. The duration of storage did not have any marked effect. The results suggest that incubation of stored blood at 46 degrees C for 1 h does not cause red cell damage.

Adult↗