Educational psychology in medical learning: a randomised controlled trial of two aide memoires for the recall of causes of electromechanical dissociation

OBJECTIVES

Although mnemonics are commonly used in medical education there are few data on their effectiveness. A RCT was undertaken to test the hypothesis that a new aide memoire, "EMD-aide", would be superior to the conventional "4Hs+4Ts" mnemonic in facilitating recall of causes of electromechanical dissociation (EMD) among house officers.

METHOD

"EMD-aide", organises causes of EMD by frequency of occurrence and ease of reversibility: four groups organised by shape, colour, position, numbering, clockwise sequence, and use of arrows. Eight hospitals were randomised in a controlled trial and 149 house officers were then recruited by telephone. Baseline ability to recall causes of EMD was recorded at one minute and overall. House officers were then sent a copy of either "4Hs+4Ts" or "EMD-aide" according to randomisation group. Recall ability was retested at one month.

RESULTS

68 of 80 and 51 of 69 house officers completed the study in the "4Hs+4Ts" and "EMD-aide" groups respectively (NS) with similar baseline recall. After intervention median number of recalled causes was greater in the "EMD-aide" group, eight compared with seven at one minute (p = 0.034) and eight compared with seven overall, p = 0.067. Recall of all eight causes was more common in "EMD-aide" group, 54% compared with 35%, p = 0.054, and these house officers spent longer examining their aide memoire, p<0.001.

CONCLUSIONS

"EMD-aide" may be superior to "4Hs+4Ts" in facilitating the recall of the causes of electromechanical dissociation. Educational psychology of medical learning and the use of aide memoires in general are worthy of further study.

Survey of abuse and violence by patients and relatives towards intensive care staff

A postal survey of senior nurses in intensive care units in England and Wales was conducted. The aim was to ascertain the frequency of abusive and violent behaviour by patients and relatives towards intensive care staff, discover the perceived causes, effects and documentation of such behaviour and define the current and proposed security arrangements for intensive care units. Response rate was 94%. During the study period, verbal abuse of nurses by patients and by relatives occurred in 87% and 74% of intensive care units, respectively. The relevant figures for doctors were 65% and 59%, respectively. Nurses experienced physical abuse by patients and by relatives in at least 77% and 17% of intensive care units, respectively (doctors 38% and 8%). Illness was the main perceived cause of offences by patients whereas 'distress' (45%), alcohol (24%), sociopathic behaviour (27%) were the main putative causes amongst relatives. Whilst 43% of intensive care units have no security system at the door, staff awareness, training and communication skills may be the principle tools in reducing the frequency and consequences of violent and abusive behaviour. This survey probably underestimates the problem.

Nasopharyngeal oxygen therapy produces positive end-expiratory pressure in infants

The World Health Organisation recommends nasopharyngeal catheters as a safe and efficient method of oxygen administration in infants. However, little is known about the mechanisms of the improvement in oxygenation. The aim of the present study was to determine whether nasopharyngeal oxygen therapy produces positive end-expiratory pressure (PEEP). Nine spontaneously breathing infants (median age 13 months, range 10 days to 20 months) after heart surgery were investigated. All patients had normal pulmonary blood flow at the time of the study (Qp:Qs=1:1). Oxygen (oxygen fraction 1.0) was delivered by an 8 F catheter inserted into the nasopharynx (tip just visible below the soft palate). The pulmonary mechanics were analysed using a single compartment model of the respiratory system. Oesophageal pressure (Pes) at end-expiration, dynamic lung compliance (C(L)) and resistance (R(L)), minute ventilation, PaCO2 and PaO2 were measured at baseline without a nasopharyngeal catheter or oxygen, and at oxygen flows of 0.5 l/min, 1.0 l/min and 2.0 l/min. All the flows generated significant increases in PEEP. Mean difference in PEEP (SD, paired t-test versus baseline): 1.6 cm H2O (1.4, P=0.008) with 0.5 l/min of oxygen; 2.8 cm H2O (2.7, P=0.014) with 1.0 l/min of oxygen; and 4.0 cm H2O (2.9, P = 0.004) with 2.0 l/min of oxygen. There was a significant correlation between all the nasopharyngeal flows (in ml/kg per min) and the generated PEEP (P<0.001) and between the C(L) values and the generated PEEP (P < 0.05). There was no significant difference in PaCO2 and R(L). Minute ventilation was significantly less with nasopharyngeal oxygen than at baseline. As expected, PaO2 increased significantly with increasing oxygen flows.

CONCLUSION

Administration of oxygen through an 8 F nasopharyngeal catheter at flow rates recommended by the World Health Organisation (0.5 l/min in newborns, 1.0 l/min in infants) produces moderate amounts of positive end-expiratory pressure. The levels achieved may contribute to an improvement in oxygenation by altering the visco-elastic properties of the lung.

Psychological adjunct to perioperative antiemesis

In a prospective, randomized study, we have examined the effects of preoperative and preinduction positive suggestion on postoperative emetic sequelae. A total of 226 patients were allocated randomly to receive either positive suggestions or no suggestions. Those patients in the positive suggestion group were told before operation and on induction of anaesthesia that postoperative emetic sequelae would be greatly reduced by the use of two antiemetic drugs. Control patients were simply asked to participate in a study of postoperative well being with no mention of nausea or vomiting. Nausea, vomiting or retching, and antiemetic administration were measured in the first 24 h after operation. Antiemetic administration in the positive suggestion group was 16.5% less than in the control group (P = 0.03) but there was no significant difference between the groups in nausea or vomiting-retching.

Fatal carbon dioxide embolism and severe haemorrhage during laparoscopic salpingectomy

We report a case of fatal carbon dioxide embolism and severe haemorrhage during laparoscopic salpingectomy. A sudden decrease in end-tidal carbon dioxide concentration occurred after 1 h of operating time which, together with the clinical signs, suggested carbon dioxide embolism. Haemorrhage after pelvic venous injury was first noted after deflation of the pneumoperitoneum and resulted in potentiation of the adverse haemodynamic effects of massive gas embolism. Minimally invasive surgery involves more extensive tissue trauma and an increased duration of pneumoperitoneum compared with diagnostic laparoscopy and may increase the risk of serious complications.

Positive end expiratory pressure and critical oxygenation during transport in ventilated patients

Transportation of patients critically dependent on positive end expiratory pressure (PEEP) can be problematic, as a patient of ours with adult respiratory distress syndrome (ARDS) and bilateral broncho-pleural fistulae demonstrated. He required intermittent positive pressure ventilation (IPPV) (Siemens 900C) with 100% O2 and PEEP of 2 kPa to maintain his arterial O2 saturation (SaO2) greater than 90%. Severe hypoxemia (SaO2 less than 75%) occurred on change to a portable ventilator (Oxylog, Dräger) with a PEEP value (Ambu 20) at its expiratory port, despite adjusting the valve to 2 kPa, continuing use of 100% O2, and varying the ventilatory pattern. The problem appeared due to loss of PEEP because of gas leak from the lungs via his intercostal catheters. It was solved by introducing a continuous O2 flow of 5 l/min into the circuit between the Oxylog non-rebreathing valve and endotracheal tube. We used a model lung to investigate the effect of a gas leak from the lungs or circuit on the performance of the Oxylog IPPV/PEEP system. Lung compliance and ventilatory pattern were adjusted so that tidal volume (VT) = 0.61, peak inspiratory Airway pressure (PIP) = 5 kPa, PEEP = 1.5 kPa, and respiratory rate = 10/min. A small leak was introduced from the lung resulting in a decrease in PIP, VT, and PEEP. Adjustment of ventilator minute volume to restore PIP to 5 kPa failed to restore PEEP, airway pressure continuing to fall throughout the expiratory pause. PEEP was restored by providing a compensatory flow of O2 of 5 l/min to the system between the Oxylog non-rebreathing valve and the lung.(ABSTRACT TRUNCATED AT 250 WORDS)

Laryngeal compression and stridor as the presenting feature of ruptured thoracic aortic aneurysm. Report of two cases

Two patients are reported in whom rupture of a thoracic aortic aneurysm presented with neck swelling and progressive stridor. Stridor occurred due to compression of the larynx by haematoma tracking up from the mediastinum. The presentation of thoracic aortic aneurysms and of rupture of thoracic aortic aneurysms are discussed with particular reference to mechanisms of cardiovascular and respiratory manifestations. The importance of early control of the airway is emphasised if there is to be any hope of survival from acute rupture.

Adriamycin cardiomyopathy. Fatal outcome of general anaesthesia in a child with adriamycin cardiomyopathy

The death under general anaesthesia of a child with Adriamycin cardiomyopathy is reported. The acute, subacute and chronic cardiotoxic effects of Adriamycin are discussed and the risk factors for chronic Adriamycin cardiomyopathy presented, with particular reference to cumulative dosage of Adriamycin. The insidious onset of impairment of cardiac function is stressed and suggestions for anaesthetic management outlined.

Potential leaks from anaesthetic machines. Potential leaks through open Rotameter valves and empty cylinder yokes

Twenty anaesthetic machines were examined to detect leakage of fresh gas through open Rotameter flow control valves and empty cylinder yokes. Significant leakage was demonstrated in most machines. Any leakage in machines which comply with ISO 5358, where oxygen is the last gas into the common gas manifold, is selective for nitrous oxide and, conversely, it is selective for oxygen in machines where oxygen is the first gas into the common gas manifold. Leakage is augmented by back pressure from ventilators that function as minute volume dividers. In ventilated patients the leakage described may contribute to hypoventilation and patient hypoxia or to pollution of the operating theatre and patient awareness.

Anaesthesia for trans-sternal thymectomy in myasthenia gravis

A retrospective review is presented of the thirty patients who underwent trans-sternal thymectomy for myasthenia gravis in our unit from 1980-85. The clinical status of these patients is contrasted to that of more severely debilitated patients described by other authors. The problems encountered by the anaesthetist in the perioperative care of patients with mild myasthenia gravis are discussed. Management of the perioperative anticholinesterase regime is described and a case presented for the use of suxamethonium for intubation. A less invasive postoperative regime is advocated in which tracheostomy and nasotracheal intubation are avoided, and anticholinesterase therapy is re-introduced orally as soon as possible after surgery.

Dangers of placement of narrow bore nasogastric feeding tubes

Three complications of the use of narrow bore nasogastric feeding tubes are described. Clinical tests to determine correct placement are noted to be unreliable and the importance of radiological confirmation is stressed. A number of suggestions are made for safe use of these tubes.