Biomedical subjects

R K Webb

Publications and source records attributed to R K Webb.

At least 37 records · Page 2Linked to original sources

PubMed1993

The Australian Incident Monitoring Study. The electrocardiograph: 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 electrocardiograph (ECG). Of these, 138 (7%) were first detected by the ECG. Of the 1256 incidents which occurred in association with general anaesthesia (GA incidents) 48% were "human detected" and 52% "monitor detected", the ECG was ranked third and detected 121 (19%) of these monitor detected GA incidents. However over 98% of incidents first detected by the ECG were heart rate changes; they would also have been detected by a pulse meter or pulse oximeter which would have supplied additional information about the adequacy of peripheral perfusion. The ECG is a "first-line" monitor in situations with the potential for myocardial ischaemia, complex dysrhythmias or altered myocardial conduction and should be used in all critically ill patients as well as those at significant risk of these problems. The ECG frequently detects incidents involving minor physiological trespass, such as simple heart rate and rhythm changes associated with anaesthetic agents. These incidents are generally detected relatively early in their evolution. AIMS data has confirmed, however, that the ECG has such poor sensitivity for serious physiological changes such as hypoxia, hypercarbia and hypotension that it cannot even be regarded as a useful "back-up" monitor for these problems. Indeed a "normal" ECG in a dangerous situation may lead to a degree of complacency.(ABSTRACT TRUNCATED AT 250 WORDS)

Accidents↗

PubMed1993

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

Of the first 2000 incidents reported to the Australian Incident Monitoring Study, 1256 occurred in relation to general anaesthesia and 81 of the latter were first detected by blood pressure (BP) monitoring. A further 25 incidents not associated with general anaesthesia were first detected by blood pressure monitoring, giving a total of 106. In the monitor detection of incidents in relation to general anaesthesia, BP monitoring ranked fourth after oximetry, capnography and low pressure alarms. On the other hand, 38 incidents in which the problem was primarily one of significant change in BP were first detected by means other than the BP monitor (20 clinically, 12 by pulse oximetry and 6 by ECG). Early detection rates of hypotension were 60% for invasive methods, 40% for automated non-invasive (NIBP) devices and 30% for manual sphygmomanometry. There were 21 reports of BP monitor "failure"; the 11 of these which occurred with NIBPs involved unexplained false "low" or "high" readings and failure to detect profound hypotension, and led to considerable morbidity and at least one death. The 10 cases of invasive monitoring failure were predominantly due to mains power loss, hardware breakage or operator error. In a theoretical analysis of the 1256 GA incidents, it was considered that on its own, BP monitoring would have detected 919 (73%), but in the vast majority, by the time this detection has occurred, potential organ damage could not be excluded. It is recommended that BP be measured at regular intervals dictated by clinical requirements (usually at least every five minutes).(ABSTRACT TRUNCATED AT 250 WORDS)

Accidents↗

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. Crisis management--validation of an algorithm by analysis of 2000 incident reports.

Anaesthetists are called upon to manage complex life-threatening crises at a moment's notice. As there is evidence that this may require cognitive tasking beyond the information-processing capacity of the human brain, it was decided to try and develop a generic crisis management algorithm analogous to the "Phase I" immediate response routine used by airline pilots. Such an algorithm, based on the mnemonic "COVER ABCD, A SWIFT CHECK", was developed and refined over 3 meetings, each attended by 60-100 anaesthetists and aviation psychologists. It was validated against 1301 relevant incidents among the first 2000 incidents reported to the Australian Incident Monitoring Study. It proved sufficiently robust and safe to recommend its general use as an initial response to any incident or crisis which occurs when a patient is breathing gas from an anesthetic machine. It requires a limited knowledge base and is easily learnt and rehearsed during the anaesthetist's working day. It will provide a functional diagnosis in over 99% of cases and will correct 62% of the problems in 40-60 seconds. In the remaining 37% it will allow the anaesthetist to proceed with a "sub-algorithm", confident in the knowledge that some important step has not been missed. In just over 30% of incidents this will be for a problem familiar to all anaesthetists (e.g. laryngospasm, bradycardia); in just over 6% it will be for a less common, more complex, but finite, set of problems (3% cardiac arrest, 1% air embolism, 1% anaphylaxis, 1% for the remaining desaturations); in less than 1% diagnosis and correction will require a more complex checklist (e.g. for malignant hyperthermia, pneumothorax). The next stage, the development of specific sub-algorithms and a structured team approach for ongoing problems, is in progress.

Algorithms↗

PubMed1993

The Australian Incident Monitoring Study. Problems before induction of anaesthesia: an analysis of 2000 incident reports.

The first 2000 incidents reported to the Australian Incident Monitoring study (AIMS) were examined to identify those incidents which occurred preoperatively (defined as occurring prior to the commencement of general or regional anaesthesia). The 35 incidents, representing 1.7% of the total, which occurred in this time period were analysed with a view to identifying areas in which current practice could be improved. Almost all incidents led to significant delays in operating lists, and 9 resulted in cancellation of surgery. A number of areas of concern specific to the preoperative period were identified. Inadequate coordination between surgical and anaesthetic staff in patient preparation was a frequent cause of preoperative incidents. Improvement in this area may reduce surgical delays and patient morbidity. Problems with premedication drugs resulted in 8 of the 35 incidents, and care must be taken in the prescription and administration of these drugs to minimise adverse effects on patients. Only 2 cases of incorrect patient identification were reported. However, in view of its disastrous consequences, vigilance in patient identification by all members of the operating team, including the anaesthetist, is essential.

Accidents↗

PubMed1993

The Australian Incident Monitoring Study. The "wrong drug" problem in anaesthesia: an analysis of 2000 incident reports.

Amongst the first 2000 incidents reported to the Australian Incident Monitoring Study, there were 144 incidents in which the "wrong drug" was nearly or actually administered to a patient. Thirty-three percent of the incidents involved ampoules and just over 40% syringes; in over half of the latter the syringes were of the same size, and also, in over half, they were correctly labelled. In 81% of the 144 incidents the "wrong drug" was actually given. This was more common with syringes (93%) than ampoules (58%). Thus the most common error was actually giving the wrong drug from a correctly labelled syringe. The most common drug involved was a muscle relaxant in both ampoule and syringe incidents. In 74% of all reports, there was the potential for serious harm to the patient; however no deaths were reported. Factors which contributed significantly to the incidents were similar appearance, inattention and haste. "Failure of communication" was a significant factor in syringe incidents when two or more staff were involved. The only significant factor which minimised the outcome was rechecking of the syringe or drug ampoule before giving the drug. Strategies suggested to address the "wrong drug" problem include education of staff about the nature of the problem and the mechanisms involved; colour coding of selected drug classes for both ampoules and syringes; the use of standardised drug storage, layout and selection protocols; having a drawing up and labelling convention; and the use of checking protocols.

Anesthesia↗

PubMed1993

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

The first 2000 incidents reported to the Australian Incident Monitoring Study were analysed with respect to the incidence and circumstances of problems with endotracheal intubation; 85 (4%) indicated difficulties with intubation. One third of these were emergency cases, one third involved an initially unassisted trainee and one fifth were outside normal working hours. Failure to predict a difficult intubation was reported in one third of the cases, with another quarter presenting serious difficulty despite preoperative prediction. Difficulties with ventilation were experienced in 1 in 7 of the 85 reports; there was one cardiac arrest, but no death. Endotracheal intubation was not achieved in one fifth of the cases. The commonest complications reported amongst the 85 incidents were oesophageal intubation (18 cases), arterial desaturation (15 cases), and reflux of gastric contents (7 cases). Emergency trans-tracheal airways were required in 5 cases. Obesity, limited neck mobility and mouth opening, and inadequate assistance together accounted for two thirds of all the contributing factors. The most successful intubation aid in this series was a gum elastic bougie. A capnograph contributed to management in 28% and a pulse oximeter in 12% of the cases in which they were used. The most serious desaturations were associated with accidental oesophageal intubation. These data suggest a lack of reliable preoperative assessment techniques and skills for the prediction of difficult intubations. They also suggest the need for a greater emphasis on ensuring that the necessary equipment is available, and on teaching and learning drills for difficult intubation and any associated difficulty with ventilation.

Accidents↗

PubMed1993

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

There were 35 oesophageal intubations in the first 2000 incidents reported to the Australian Incident Monitoring Study (AIMS). These reports confirm existing impressions that misplacement of the endotracheal tube can occur in trained as well as untrained hands, and that auscultation is an unreliable test. On the other hand, the value of capnography is emphasised, with no false positives in the 16 cases in which the instrument was used. There was one false negative. Over the 4 years of the AIMS study, reports have declined in frequency. It is possible that the early detection of oesophageal intubation by capnography has altered its status to the extent that anaesthetists no longer regard it as a "critical" incident. It is highly recommended that the presence of the expected concentration of carbon dioxide in expired air be confirmed by capnography immediately after any endotracheal intubation.

Accidents↗

PubMed1993

The Australian Incident Monitoring Study. Problems related to the endotracheal tube: an analysis of 2000 incident reports.

The first 2000 incidents reported to the Australian Incident Monitoring Study were analysed with respect to problems with the endotracheal tube; 189 (9%) were reported. The most common problem was endobronchial intubation which accounted for 42% of these 189 reports; endobronchial intubation was the most common cause of arterial desaturation in the 2000 incidents. Obstructions and oesophageal intubation each accounted for 18% of the 189 problems with tubes. The remainder was made up of disconnections and leaks (7% each), misplacements other than endobronchial or oesophageal (4%), inappropriate choice of tube (3%), cuff herniation (1%), failure to deflate the cuff and foreign body in the tube (0.5% each). The pulse oximeter and capnograph first detected 58% of these incidents; a further 25% were detected clinically. The pulse oximeter is the "front-line" monitor for endobronchial intubation, and the capnograph the "front-line" monitor for oesophageal intubation, disconnection and obstruction. Recommendations are made for how to prevent problems and how to determine the nature of those that do occur.

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. Clinical anaphylaxis: an analysis of 2000 incident reports.

There were 57 reports of possible allergic reactions in the perioperative period in the first 2000 incidents reported to the Australian Incident Monitoring Study. These were examined and classified with respect to presentation, clinical course, agents implicated and management strategies employed. Reactions were graded as to probability of allergic aetiology and severity of systemic disturbance. Two deaths were reported. A method of determining an "allergy score" was devised as an indication of which reactions may be most deserving of further investigation.

Anaphylaxis↗

PubMed1993

The Australian Incident Monitoring Study. Cardiac arrest--an analysis of 2000 incident reports.

Eighty-seven cases of cardiac arrest from the first 2000 incidents reported to the Australian Incident Monitoring Study were reviewed. "Cardiac arrest" was taken to include patients who were either pulseless or had electrocardiographic asystole or ventricular fibrillation. Cases were grouped by primary cause--drug administration (19), vagal stimulation (16), hypoventilation (15), bleeding (13), anaphylaxis (6), direct cardiac stimulation (4) and miscellaneous (14). Overall, 20 patients died (23% of the 87 cases); all of these were in the hypoventilation, bleeding, or miscellaneous groups (4, 9 and 7 patients, respectively). Cardiac compression was performed in 66% of patients; 20% were defibrillated; adrenaline was given to 42% and bicarbonate to 3%. There was a clear anaesthetic cause for 46% of this series of arrests, and with hindsight, a preventable factor was present in over half (58%) of these. Preventative strategies regarding staffing, equipment, policy and procedures are suggested.

Anesthesia↗

PubMed1993

The Australian Incident Monitoring Study. Air embolism--an analysis of 2000 incident reports.

There were 19 cases of air embolism (1%) among the first 2000 incidents reported to the Australian Incident Monitoring Study. No embolism-induced fatalities were reported. Serious acute systemic effects occurred in 14 incidents; one circulatory arrest required electrical counter-shock. The surgical field was the entry route for the air in 63% of the incidents; 47% of the cases occurred during head and neck surgery. Capnography was the most successful first detector (26%) and it confirmed the diagnosis in another 26%. Invasive blood pressure monitoring, the electrocardiograph and the pulse oximeter played a useful role in detecting and/or confirming air embolism. Doppler monitoring was not reported in this series. A successful first response for management included head-down posture, manual ventilation, 100% oxygen and control of the air entry site. Cerebral arterial gas embolism may induce vascular endothelial damage and possible delayed neurological sequelae; hyperbaric oxygen therapy should be considered.

Anesthesia↗

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. Problems with regional anaesthesia: an analysis of 2000 incident reports.

There were 160 incidents associated with regional anaesthesia amongst the first 2000 incidents reported to the Australian Incident Monitoring Study. They were categorised into 6 groups; epidural anaesthesia (83), spinal anaesthesia (42), brachial plexus blocks (14), intravenous local anaesthesia (4), ocular blocks (3), and local infiltration (14). The largest single cause of incidents involved circulatory problems; these occurred in all the groups except brachial plexus block (30 cases of hypotension, 7 of arrhythmias, 3 of cardiac arrest, 2 of hypertension and 1 of myocardial ischaemia). There were 24 drug errors, of which 10 involved the "wrong drug" and 4 "inappropriate use". With the exception of these, all the remainder involved problems specific to regional anaesthesia: 26 inadvertent dural punctures; 19 failed or inadequate blocks; 14 dural puncture headaches (all cured by blood patches); 10 inadvertent total or high spinal blocks (of which 7 required artificial ventilation); 5 blocks on the wrong side or in the wrong patient; 3 late hypoxic incidents and a variety of miscellaneous problems. Three-quarters of all incidents occurred in the presence of an anaesthetist and over 90% in patients of ASA Groups I-III. Rapid recognition by the anaesthetist prevented many potentially life threatening events, and the only death was as a result of surgical bleeding.

Accidents↗

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. Patient awareness during anaesthesia: an analysis of 2000 incident reports.

Amongst the first 2000 incidents reported to the Australian Incident Monitoring Study were 16 cases in which patient recall of perioperative events was consistent with awareness. Awareness that occurred in 3 of 10 cases during anaesthesia was attributed to low concentrations of volatile anaesthetic agent; the conduct of anaesthesia appeared to be unremarkable in the other 7. The remaining 6 cases involved the inadvertent paralysis of patients prior to induction of anaesthesia, most commonly by "syringe swap" when suxamethonium was given instead of fentanyl. Some of these patients were significantly distressed. These preliminary findings suggest that incident monitoring should be useful in the study of awareness associated with anaesthesia and the development of strategies to prevent it.

Anesthesia↗