Pulmonary volume recruitment restores pulmonary compliance and resistance in anaesthetized young children.

BACKGROUND: Oxygenation and gas exchange are impaired after induction of general anaesthesia. A timed re-expansion inspiratory manoeuvre (TRIM) improves pulmonary compliance and reverses haemoglobin oxygen desaturation rapidly in lambs. METHODS: Twenty children of less than 2 years of age were given a standardized ventilated general anaesthetic. After 15 min of anaesthesia they were randomized to receive either a TRIM or 100% oxygen for 3 min. Dynamic pulmonary compliance and airway resistance were measured. RESULTS: Pulmonary compliance fell by 12% and airway resistance rose by 12% during 15 min of ventilated general anaesthesia. 100% oxygen caused a further fall of 9% in compliance (P=0.016), whilst TRIM resulted in a 30% increase in compliance (P < 0.01). The changes in airway resistance with 100% oxygen and TRIM were not statistically significant. CONCLUSIONS: This study shows that TRIM increases pulmonary compliance during standardized ventilated general anaesthesia.

Pulmonary volume recruitment manoeuvre restores pulmonary compliance and resistance after apnoea in anaesthetized lambs.

BACKGROUND: We studied the effects of an episode of induced apnoea on the dynamic compliance (Crs) and resistance (Rrs) of the respiratory system in anaesthetized lambs and investigated the mechanisms underlying the effectiveness of a timed reexpansion inspiratory manoeuvre (TRIM). METHODS: Following 2 min of apnoea, three manoeuvres were randomly performed: (i) control: reventilated without TRIM using initial settings and gas composition of 30% oxygen in 70% nitrous oxide; (b) T1: TRIM with 30% oxygen in 70% nitrous oxide, followed by reventilation with the initial settings; and (c) T2: preoxygenate with 100% oxygen, apnoea, then TRIM with 100% oxygen, then reventilation with 100% oxygen at the initial settings. The percentage change in Crs and Rrs was calculated at first breath, second breath, 10, 20, 40, 60, 90, 120 and 180 s postapnoea. RESULTS: Mean control decreased 15% and did not return to baseline during the study period. TRIM increased mean Crs in T1 and T2 by 8% and 9%, respectively, at first breath and returned to baseline and did not deteriorate for the remainder of the study period. Mean Rrs in the control group increased 20% and did not return to baseline during the study period. Mean Rrs in T1 and T2 initially increased 17% and 27%, respectively, at first breath and returned to baseline within 40 s. CONCLUSIONS: These results demonstrate that significant deterioration occurs in Crs and Rrs following 2 min of apnoea in anaesthetized lambs, which is not corrected with normal ventilation but is rapidly and completely reversed with a TRIM. This supports our hypothesis that volume recruitment of alveoli is an effective manoeuvre in restoring lung function. The practice of preoxygenation is also reinforced as the lambs maintained maximal oxygen saturation if they were ventilated with 100% oxygen prior to the 2 min of apnoea.

An audit of perioperative management of autistic children.

BACKGROUND: Autistic children are very difficult to manage in the hospital setting because they react badly to any change in routine. METHODS: We have developed a unique management program for autistic children admitted for medical and surgical procedures requiring a general anaesthetic. Details of each patient managed according to this program have been prospectively entered into an Autistic Register. RESULTS: An audit of this database shows that we have administered anaesthesia on 87 occasions for 59 autistic children over 4 years. CONCLUSIONS: There is great variation in the severity of autism and hospital needs of these children. The focus is on early communication with the patient's families, flexibility to individualize the admission process and anaesthetic plan with admission and early discharge on the day of surgery whenever possible. Oral midazolam is an effective premedication for the milder cases and oral ketamine is the most reliable for moderate and severe cases. Comparison of oral midazolam and ketamine shows no significant different postoperative recovery and hospital discharge times. Routine intravenous fluids and antiemesis prophylaxis with removal of the i.v. cannula before return to the ward are also seen as important steps to decrease stress and smooth the postoperative phase. This program has also successfully been extended to the management of problem children due to other causes.

Anaesthesia alert: an integrated, networked, register of paediatric anaesthetic problems.

The Paediatric Register of Anaesthetic Problems (PaedRAP) is a network-based anaesthesia hazard alert system. It is integrated with pre-anaesthesia consultations and patient questionnaires. All files, both electronic and on paper, are available 24 hours a day close to the operating theatres. This ensures that pertinent information is readily available when and where it is most needed. The PaedRAP is also linked to the automated theatre booking system to print warnings on the theatre lists. This minimizes the chance that important information goes unnoticed. Documentation of the progression of the various categories of patient problems and evolving management strategies has been useful both for individuals and groups.

Clinical predictors of anaesthetic complications in children with respiratory tract infections.

Details of the preoperative condition, in particular symptoms of respiratory tract infections (RTI), perioperative management and the occurrence of perioperative complications, were collected in a survey of 2051 children. Logistic regression was used to determine which variables were predictors of anaesthetic adverse events. 22.3% of the children had symptoms of an RTI on the day of surgery, and 45.8% had a 'cold' in the preceding 6 weeks. Logistic regression returned eight variables. They were method of airway management, parent states the child has a 'cold' on the day of surgery, child has nasal congestion, child snores, child is a passive smoker, induction agent chosen, child produces sputum, and whether reversal agent used. Orotracheal intubation was associated with an increased probability of complications when compared with laryngeal mask airway and facemask. RTI in the preceding 6 weeks did not increase probability of complications. Wheeze, fever, malaise and age could not be excluded as predictors in this study because children with these symptoms and infants with colds were effectively excluded from the study.

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.

Relative bioavailability and plasma paracetamol profiles of Panadol suppositories in children.

OBJECTIVE: To determine the relative bioavailability and plasma paracetamol concentration profiles following administration of a proprietary formulation of paracetamol suppositories to postoperative children. METHODOLOGY AND RESULTS: Study A-eight children undergoing minor surgery had blood samples collected following the rectal administration of either a 250 mg or 500 mg paracetamol suppository on one day and an equivalent oral dose on the following day. A mean dose of 13 mg/kg gave a mean Cmax (Tmax) of 7.7 mg/L (1.6 h) and 4.9 mg/L (2.0 h) following oral and rectal administration, respectively. The mean relative rectal bioavailability was 78% (95% confidence interval of 55-101%). Study B-20 children undergoing tonsillectomy and/or adenoidectomy were randomly assigned to receive a postoperative dose of 500 mg of paracetamol either as 2 x 250 mg liquid filled or 1 x 500 mg hard wax Panadol suppository. A mean dose of 25 mg/kg produced mean maximum plasma paracetamol concentrations of 13.2 mg/L and 14.5 mg/L at 2.1 and 1.9 h for the hard and liquid filled suppository, respectively. The absorption rate constants and areas under the curves suggested no difference in the rate or extent of absorption between the two formulations. CONCLUSION: Absorption of paracetamol following rectal administration of Panadol suppositories to postoperative children is slower and reduced as compared to oral therapy. The hard wax and liquid filled products have similar absorption characteristics. The usually quoted antipyretic therapeutic range for paracetamol is 10-20 mg/L, although 5 mg/L may be effective. A single rectal dose of 25 mg/kg will obtain this lower concentration within 1 h of administration and maintain it for up to 6 h. When given in an appropriate dose for analgesia, maximum plasma paracetamol concentrations would be available in the immediate postoperative period if the rectal dose was given 2 h before the planned end of the procedure.

A timed reexpansion inspiratory manoeuvre (TRIM) for treating oxyhaemoglobin desaturation in children following a period of apnoea--studies in an animal model.

Our clinical experience has shown that the use of a constant distending airway pressure of 30 cm water for 10 s, termed a timed reexpansion inspiratory manoeuvre (TRIM), is often successful in correcting oxyhaemoglobin desaturation in anaesthetized children. The aim of this study was to assess the efficacy of TRIM in lambs. Following a standard relaxant anaesthetic, ventilation was stopped and oxyhaemoglobin saturation allowed to fall to 70% and the time taken to return to baseline was compared between three groups. The median time was 42.5 s when ventilation was restarted with 33% oxygen in nitrous oxide (33% group), 30 s when ventilation was restarted with 100% oxygen (100% group) and 22.5 s with a TRIM before restarting ventilation with 33% oxygen in nitrous oxide (TRIM group). The correction of desaturation was more rapid in the TRIM group compared with the 33% group (P < 0.004) and the 100% group (P < 0.003). Oxyhaemoglobin desaturation due to apnoea in anaesthetized lambs is more effectively treated with a TRIM than by increasing the inspired oxygen fraction.

The anaesthetic management of autistic children.

Autistic children are difficult to manage and there are no anaesthesia studies to suggest management strategies. We present five case reports which describe an integrated management program taking into account the special needs of autistic children and their families. We describe a method of early warning and recognition of these patients and the establishment of a database to allow review of our program. We also present a process to minimize the stress and problems inherent in the conventional admission process. Oral ketamine (6 to 7 mg/kg) has proven to be the most reliable preoperative sedative for these patients.

Needleless and sharp-free anaesthesia.

Accidental occupational infection of anaesthetists from patient body fluids is a very real and potentially fatal risk that will be significantly reduced with the routine use of universal precautions and the adoption of specific safe work practices. Employers are required by law to provide a safe working environment and safe systems for work which anaesthetists should implement according to recommendations in this paper. A protocol should be available to be acted upon in the event of occupational parenteral, mucous membrane and non-intact skin exposure to infected patient body fluids. Recommendations are made in six major areas of clinical practice which anaesthetists should adopt to minimize risks to themselves and other healthcare workers: loading syringes, cannulating blood vessels, administering intramuscular (IM) or local anaesthetic injections, administering intravenous (IV) drugs, use of sutures and surgical instruments by anaesthetists and the safe disposal of needles, glass ampoules and other sharp materials. Despite the known risks and the development of these safe practices there is poor compliance by anaesthetists with measures to safeguard themselves and others.

Anaesthesia and recently vaccinated children.

Most countries have active vaccination programmes for children aged two months and older. It is likely that many children presenting for medical procedures which require general anaesthesia have been vaccinated recently. Although there is no evidence suggesting increased risks associated with anaesthetizing recently vaccinated children there are many theoretical reasons why this situation needs critical assessment and review. After vaccination there is local swelling and pain at the site of the injection and the most common side effects seen are fever, malaise, headache, rash and myalgia which may last from one day to three weeks. Anaesthesia, stress and trauma are known to suppress the immune system. It is suggested that if possible, children should not be subjected to anaesthesia for elective procedures within two to three weeks after vaccination. Urgent procedures should be managed according to anaesthetic principles which will minimize the effect of anaesthesia on the physiological system affected by the immunization process at the time. Paediatric anaesthesia risk management programmes should include vaccination data to enable the risks of anaesthesia in recently vaccinated children to be analysed.

A national survey of atropine use by Australian anaesthetists.

All Fellows of the Faculty of Anaesthetists, Royal Australasian College of Surgeons (now Australian and New Zealand College of Anaesthetists) were surveyed by mail regarding their use of prophylactic atropine. They were asked whether their usual practice was to give atropine for the following indications: premedication, induction of anaesthesia, intubation of the trachea, one dose of suxamethonium, a second dose of suxamethonium, halothane anaesthesia, oropharyngeal surgery, bronchoscopy and eye surgery. For each indication they were asked for details regarding their practice concerning neonates, infants, children and adults. The large response rate of 86% of Fellows returning a survey form ensured that the survey was representative of Australian anaesthetic practice. Results indicate a wide variation in practice regarding the prophylactic use of atropine, with neonates, infants and children more likely to receive prophylactic atropine than adults. The majority do not give prophylactic atropine as premedication, but may give it in the younger age groups at induction, and many (67%) only give it if they are to administer suxamethonium to a child. The only indication for which a convincing majority (> 80%) of anaesthetists agreed that prophylactic atropine should be given was when a repeated dose of suxamethonium was to be given to neonates, infants or children. A large proportion of anaesthetists (> 80%) agreed that atropine is not necessary prior to halothane anaesthesia in all age groups, nor as premedication, at induction, at intubation, prior to oropharyngeal surgery or prior to eye surgery in adults. These results were compared with the practice at a major paediatric hospital where the practice is not to use routine prophylactic atropine.

The Australian Incident Monitoring Study. Which monitor? An analysis of 2000 incident reports.

The role of monitors in patients undergoing general anaesthesia was studied by analysing the first 2000 incidents reported to the Australian Incident Monitoring Study; 1256 (63%) were considered applicable to this study. In 52% of these a monitor detected the incident first; oximetry (27%) and capnography (24%) detected over half of the monitor detected incidents, the electrocardiograph 19%, blood pressure monitors 12%, a low pressure (circuit) alarm 8%, and the oxygen analyser 4%. Of the other monitors used, 5 first detected 1-2% of incidents, and the remaining 8 less than 0.5% each. The oximeter would have detected over 40% of the monitor detected incidents had its more informative modulated pulse tone always been relied upon instead of the "bleep" of the ECG. A theoretical analysis was then carried out to determine which of an array of 17 monitors would reliably have detected each incident had each monitor been used on its own and had the incident been allowed to evolve. To facilitate "scoring" of monitors, the incidents were categorized empirically into 60 clinical situations; 40% of applicable incidents were accounted for by only 5 clinical situations, 60% by 10 and nearly 80% by 20. 98% were accounted for by the 60 situations. A pulse oximeter, used on its own, would theoretically have detected 82% of applicable incidents (nearly 60% before any potential for organ damage). These figures for capnography are 55% and 43% and for oximetry and capnography combined are 88% and 65%, respectively. With the addition of blood pressure monitoring these become 93% and 65%, and of an oxygen analyser, 95 and 67%. Other monitors, including the ECG, each increase the yield by by less than 0.5%. The international monitoring recommendations and those of the Australian and New Zealand College of Anaesthetists are thoroughly vindicated by the patterns revealed in this study. The priority sequence of monitor acquisition for those with limited resources should be stethoscope, sphygmomanometer, oxygen analyser if nitrous oxide is to be used, pulse oximeter, capnograph, high pressure alarm, and, if patients are to be mechanically ventilated, a low pressure alarm (or spirometer with alarm); an ECG, a defibrillator, a spirometer and a thermometer should be available.

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)

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.

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.

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.