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

Oxygen embolism caused by accidental subcutaneous injection of hydrogen peroxide during orthopedic surgery: A case report

INTRODUCTION

We report a 39-year-old male patient with a fracture of the right acetabulum undergoing open reduction and internal fixation with a plate under general anesthesia. At closure, the surgeons injected 0.75% ropivacaine into the subcutaneous tissue of the incision wound for postoperative analgesia. Soon after injection, subcutaneous emphysema at the injection site and a sudden decrease in end-tidal CO2 tension with crude oscillatory ripples during the alveolar plateau phase were observed. Shortly thereafter, it was found that the surgeons had mistakenly injected hydrogen peroxide instead of ropivacaine. Fortunately, the patient recovered to normal status after 10 minutes. After the surgery, the patient was carefully observed for suspected pulmonary embolism and discharged without complications.

CONCLUSION

Adverse events related to medication errors can occur in operating rooms, and most cases can be prevented through communication and verification by medical staff. The use of hydrogen peroxide should be reevaluated; when used, medical staff should be aware of the risk of oxygen embolism and take extreme care.

Hyperbaric medicine for the hospital-based physician

Hyperbaric oxygen (HBO2) is the inhalation of 100% oxygen at pressures > 1.4 times atmospheric pressure. Hyperbaric oxygen can be delivered in monoplace (single person) or multiplace (multi-person) chambers. Most clinical HBO2 exposures are between 2 and 2.4 atm abs for approximately 2 hours. Hyperbaric oxygen causes the blood and tissue oxygen levels to increase, reduces the volume of intravascular and tissue bubbles (to treat decompression sickness [DCS] and arterial gas embolism [AGE]), and accelerates wash-out of other gases, such as nitrogen or carbon monoxide (CO), which is important for DCS, AGE, and CO poisoning. Hyperbaric oxygen favorably modulates ischemia-reperfusion injury by transiently inhibiting neutrophil-endothelial interactions, which is important for patients with DCS, AGE, CO poisoning, and potentially other acute ischemic conditions. Because of enhanced oxygen delivery, HBO2 is used for acute crush injury, ischemic flaps and grafts, acute central retinal arterial occlusion, other acute arterial occlusions, and idiopathic sudden sensorineural hearing loss. Hyperbaric oxygen has antimicrobial effects and is offered for patients with limb- or life-threatening infections, such as clostridial gas gangrene and necrotizing fasciitis. The most common US indication for HBO2 is the treatment of ischemic wounds (eg, diabetic lower extremity wounds, late effects of radiation, and refractory osteomyelitis). In ischemic wounds, HBO2 can deliver sufficient oxygen to the nonhealing wound to stimulate angiogenesis and healing through multiple mechanisms, including increased collagen production, increased growth factor receptor numbers, upregulation of vascular endothelial growth factor, increased circulating endothelial progenitor cells, and improvement in neutrophil-mediated host defense. Clinical trials support efficacy of HBO2 for acute CO poisoning, diabetic lower extremity wounds, crush injury, and radiation necrosis. Most hyperbaric chambers are associated with wound care centers and may be hospital based or nonhospital based. We review some of the disorders treated with HBO2 that hospital-based clinicians may be asked to evaluate.

Crisis management during anaesthesia: embolism

BACKGROUND

Embolism with gas, thrombus, fat, amniotic fluid, or particulate matter may occur suddenly and unexpectedly during anaesthesia, posing a diagnostic and management problem for the anaesthetist.

OBJECTIVES

To examine the role of a previously described core algorithm "COVER ABCD-A SWIFT CHECK" supplemented by a specific sub-algorithm for embolism, in the management of embolism occurring in association with anaesthesia.

METHODS

The potential performance of this structured approach for each of the relevant incidents among the first 4000 reported to the Australian Incident Monitoring Study (AIMS) was compared with the actual management as reported by the anaesthetists involved.

RESULTS

Among the first 4000 incidents reported to AIMS, 38 reports of embolism were found. A sudden fall in end-tidal carbon dioxide and oxygen saturation were the cardinal signs of embolism, each occurring in about two thirds of cases, with hypotension and electrocardiographic changes each occurring in about one third of cases.

CONCLUSION

The potential value of an explicit structured approach to the diagnosis and management of embolism was assessed in the light of AIMS reports. It was considered that, correctly applied, it potentially would have led to earlier recognition of the problem and/or better management in over 40% of cases.

Intraoperative visible bubbling of air may be the first sign of venous air embolism during posterior surgery for scoliosis

STUDY DESIGN

Case report of two children sustaining venous air embolism (VAE) during posterior surgery for scoliosis.

OBJECTIVES

To report 2 cases where visible bubbling at the operative site was the first clinical indication of VAE-induced cardiovascular collapse and to raise the level of consciousness that VAE in the prone position can occur, often with serious consequences.

SUMMARY OF BACKGROUND DATA

Twenty-two cases of VAE during surgery for scoliosis in the prone position have been reported. Ten were fatal and ten were in children. Visible bubbling at the operative site was noted in two published cases.

METHODS

Retrospective study of 2 cases of VAE at one institution. Clinical, anesthetic, and radiographic features are presented. Details of previously published cases are reviewed and discussed.

RESULTS

Both patients were girls with adolescent scoliosis who underwent prone positioned posterior spinal fusion with instrumentation. Visible bubbling of air at the thoracic aspect of the surgical site was noted near the completion of instrumentation and was the first indication of VAE. In both cases, this was clinically recognized and promptly treated. One patient survived normally and the other died.

CONCLUSIONS

Visible air bubbling at the operative site may herald the onset of massive VAE during multilevel posterior spinal fusion and instrumentation. A prospective multicenter study using precordial Doppler, central venous catheter, and end-tidal CO2 is recommended to determine the true incidence of VAE in spinal deformity surgery and to evaluate monitoring and treatment methods.

Paradoxical air embolism from patent foramen ovale in scoliosis surgery

STUDY DESIGN

A case was reported in which paradoxical air embolism arose from the patent foramen ovale in scoliosis surgery.

OBJECTIVES

To present a case of suspected paradoxical air embolism after scoliosis surgery.

SUMMARY OF BACKGROUND DATA

Embolic accident during scoliosis surgery may be caused by air, thrombus, or fat. There is growing attention on patent foramen ovale involved in paradoxical embolism. The devastating consequences are caused by multiple artery occlusions.

METHODS

Details of a recent documented neurologic complication (paraplegia, weakness of right arm, and blurry vision) after scoliosis surgery have been analyzed in medical publications.

RESULTS

The surgical procedure was not imputed. The causative role of epidural catheter for analgesia was considered, but it is likely that a paradoxical embolism occurred in this case, based on the multifocal (cerebral and spinal) neurologic dysfunction, the evidence of cerebral ischemia (on computed tomography), and the presence of a patent foramen ovale (on postoperative transesophageal echocardiography). Although no intraoperative embolism detection was available, air embolism was highly suspected because there was no absolute argument to exclude cruor or fatty embolism.

CONCLUSIONS

It is critical to detect a patent foramen ovale before surgery and cerebral embolization intraoperatively. This might permit ascertainment of the etiologic diagnosis in case of a complication in surgery for scoliosis.

Amount of air infused to patient increases as fluid flow rates decrease when using the Hotline HL-90 fluid warmer

OBJECTIVE

The intraoperative use of fluid warming devices has been recommended to avoid perioperative hypothermia and related adverse outcomes. To evaluate whether these devices might introduce risks of their own, we measured the volume of air escaping from a warmed intravenous solution that might be delivered to a patient.

METHODS

In an operating room maintained at 19-19.5 degrees C, we tested an HL-90 Hotline fluid warmer with the L-70 fluid-warming set. One liter of lactated Ringer's solution was infused at flow rates of 150, 300, 500 and 3400 ml/h. The air that formed within the L-70 tubing during infusion was collected in a bubble trap placed at the end of the L-70 tubing. The volume of air in the bubble trap was measured. Twelve separate measurements were obtained at each flow rate. One additional study (n = 8) was performed using the L-10 Gas Vent to determine whether this equipment might reduce the volume of air infused when fluid flow rate was 300 mL/h. The volume of air collected at each flow rate was compared using ANOVA.

RESULTS

Volume of air increased significantly from 1.0 +/- 0.2 mL to 2.9 +/- 0.4 ml as flow rate decreased from 3400 ml/h to 150 ml/h (p < 0.0001). The L-10 gas eliminator was ineffective in reducing the amount of air infused.

CONCLUSIONS

We conclude that the use of the Hotline fluid warmer can result in infusion of air into the patient, introducing possible risk of air embolism.

Capnometry as a tool to unmask silent pulmonary embolism

Because pulmonary embolism is often silent, simple clinical procedures are desirable to identify patients with a low to intermediate probability of pulmonary embolism. Among 19,467 patients managed under general anesthesia, we had one bile tract surgery case and three neurosurgical cases whose silent pulmonary embolism was initially suggested by an increase in the arterial to end-tidal CO2 gradient (from 17 to 27 mmHg) after general anesthesia was induced or their trachea was intubated. During the preoperative assessment, the patients presented no clinical manifestations suggestive of pulmonary embolism. Our initial diagnosis was confirmed by scintigraphy and/or angiography done immediately after the operations. Because capnometry has been shown to be applicable to non-intubated, spontaneously breathing patients, we suggest that measuring the gradient may serve as an additional method for unmasking silent pulmonary embolism in patients at risk or with disturbed consciousness, whether they are scheduled for operations or not.

Massive air embolus to the left ventricle: diagnosis and monitoring by serial echocardiography

Air embolization is an unusual but potentially dangerous complication in left heart catheterization. Microbubbles can be detected with two-dimensional echocardiography, which is often used for this purpose during open heart and bypass surgeries. Permanent neurologic sequelae and hemodynamic collapse can result from embolization of air bubbles to the cerebral and coronary circulations, respectively. Hyperbaric oxygen is the treatment of choice for cerebral air embolization. We present a 39-year-old man who had air embolization during left ventriculography in the form of a large pocket of "pooled" air. The patient was treated with conservative therapy successfully. Two-dimensional transthoracic echocardiography was used to document the presence of the air and follow its dissolution.

Two cases of fatal air embolism in children undergoing scoliosis surgery

Venous air embolism during surgery is a rare but important complication and can be rapidly fatal. We present two cases of fatal air embolism in the prone position occurring in small children undergoing surgery for progressive scoliosis. Venous air embolism is a rare complication in the prone position. This is thought to be because in this position there is virtually no gravitational gradient between the site of surgery and the right atrium. The possible sites of entry of air and ways that this may be minimized are discussed.

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)

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)

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.

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

The first 2000 incidents reported to the Australian Incident Monitoring Study were analysed with respect to the role of the capnograph. One hundred and fifty-seven (8%) were first detected by a capnograph and there were a further 18 (1%) in which capnography was contributory. Of the 1256 incidents which occurred in association with general anaesthesia 48% were "human detected" and 52% "monitor detected". The capnograph was ranked second and detected 24% of these monitor detected incidents; this figure would have been nearly 30% if a correctly checked, calibrated capnograph had always been used. The capnograph is a "front-line" monitor for oesophageal intubation, failure of ventilation, anaesthetic circuit faults, gas embolism, sudden circulatory collapse and malignant hyperthermia. It is a valuable "back-up" monitor when other monitors (e.g. low pressure alarm, pulse oximeter) are not in use, are being used incorrectly or fail. Such situations, in order of frequency of detection were: circuit-leak, overpressure of the breathing circuit, bronchospasm, leak of ventilator-driving-gas into the patient circuit, aspiration and/or regurgitation and hypoventilation. There were 20 reports of "failure", over two-thirds of which would not have occurred with appropriate checking and calibration. Seven were due to gas sampling problems and 6 to apnoea alarm failure. Two circuit leaks and 2 faulty unidirectional valves were not detected; on 3 occasions problems occurred due to power failure, calibration problems, or misinterpretation of an alarm.(ABSTRACT TRUNCATED AT 250 WORDS)

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

Although 70-80% of problems have some component of human error, its overall contribution to many problems may be small; studies of complex systems have revealed that up to 85% are primarily due to deficiencies in the lay-out and processes of the system. The anaesthetist has to operate in a complex system; many problems originate from deficiencies in this system. Information of relevance to system failure was extracted from the first 2000 incidents reported to the Australian Incident Monitoring Study (AIMS). A system-based deficiency directly contributed to one-quarter of problems (four-fifths if human factors are included), some aspect of the system minimized the adverse outcome in over half of all cases (four-fifths if human factors are included), and in two-thirds (three-quarters if human factors are included) a system-based strategy would have been helpful; the system was implicated in 90% of all incidents (97% if human factors are included). Regardless of whether or not all human error should be regarded as part of the "system", attempts to modify its incidence and nature have to emanate from the system. AIMS reporting pathways and the organizations involved in developing and implementing strategies to improve the system operate at four levels. Level I involves the use of AIMS reports by hospitals and group practices for audit at a local level. Level II involves AIMS participants sending forms to the AIMS central office; collated information is then sent back to contributors by newsletter. Level III involves interaction between AIMS and the major professional bodies and level IV interaction between AIMS, these bodies and a variety of national and international agencies. Over 100 topics were identified from the AIMS data for consideration at one or more of these levels. AIMS has the potential not only to play a vital practical role in the continued enhancement of the quality of anaesthetic practice, but also to provide a valuable resource for research at the increasingly important interface between human behaviour and complex systems.

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

The Australian Patient Safety Foundation was formed in 1987; it was decided to set up and co-ordinate the Australian Incident Monitoring Study as a function of this Foundation; 90 hospitals and practices joined the study. Participating anaesthetists were invited to report, on an anonymous and voluntary basis, any unintended incident which reduced, or could have reduced, the safety margin for a patient. Any incident could be reported, not only those which were deemed "preventable" or were thought to involve human error. The Mark I AIMS form was developed which incorporated features and concepts from several other studies. All the incidents in this symposium were reported using this form, which contains general instructions to the reporter, key words and space for a narrative of the incident, structured sections for what happened (with subsections for circuitry incidents, circuitry involved, equipment involved, pharmacological incidents and airway incidents), why it happened (with subsections for factors contributing to the incident, factors minimising the incident and suggested corrective strategies), the type of anaesthesia and procedure, monitors in use, when and where the incident happened, the experience of the personnel involved, patient age and a classification of patient outcome. Enrollment, reporting and data-handling procedures are described. Data on patient outcome are presented; this is correlated with the stages at which the incident occurred and with the ASA status of the patients. The locations at which the incidents occurred and the types of procedures, the sets of incidents analysed in detail and a breakdown of the incidents due to drugs are also presented.(ABSTRACT TRUNCATED AT 250 WORDS)