The aetiology and prevention of peri-operative corneal abrasions.

Corneal abrasion is the most frequent ocular complication to occur during the peri-operative period. This review describes the aetiology of corneal abrasions and evaluates the current methods of prevention. Most abrasions are caused by lagophthalmos (failure of the eyelids to close fully) during general anaesthesia, resulting in corneal drying. General anaesthesia reduces both the production and the stability of tears and therefore increases the incidence of this painful condition. Taping the eyelids closed, soft contact lenses, the instillation of aqueous gels or paraffin-based ointments are all effective in preventing corneal abrasions, but ointments are associated with significant morbidity.

A study of the incorrect use of ventilator disconnection alarms.

Pressure-sensitive ventilator disconnection alarms may fail to function correctly when used with discharging compliance ventilators such as the Manley Blease. The increase in gas flow on disconnection generates raised pressure owing to the resistance provided by components of the breathing system. Thirty-four anaesthetists, who were unaware of the nature of the survey, were observed to see if previous recommendations for the correct adjustment of the ventilator alarm were being followed. It was found that 77% of alarms were incorrectly adjusted and would not have alarmed in the event of a true disconnection occurring.

Non-invasive monitoring of cardiac output changes during aortic cross-clamping for infrarenal reconstruction--a new technique using suprasternal Doppler-derived cardiac output.

There is a significant morbidity and mortality associated with elective infrarenal aortic reconstruction. To examine the value of continuous cardiac output monitoring for predicting those at risk, 40 consecutive patients were monitored using Doppler-derived cardiac output. The anaesthetist was blind to all information from the monitor and managed the patients using standard techniques. In 28 patients there were no observed changes, while in seven, cardiac output rose after aortic cross-clamping. In five patients a fall in cardiac output occurred after cross-clamping. No cardiac events or cardiac deaths occurred in the 35 patients who showed a rise or no change in cardiac output. However, there were three cardiac events, including one cardiac death in the group of five patients in whom a fall in cardiac output was observed. It would appear that intraoperative non-invasive Doppler-derived cardiac output monitoring successfully predicts high-risk patients who would perhaps benefit from more intensive pre-, peri- and postoperative care.

Postoperative analgesia for haemorrhoidectomy. A comparison between caudal and local infiltration.

This study compared the analgesic effectiveness of local infiltration of bupivacaine with caudal extradural bupivacaine in the first 48 hours after haemorrhoidectomy. Surgical and anaesthetic protocol was rigidly standardised. The caudal group had significantly less pain in the first 6 hours after haemorrhoidectomy, and on first bowel opening, when compared to those who received local infiltration of bupivacaine. There was no significant difference between the two groups with respect to further analgesic requirements, complications, time to first bowel action, and duration of hospital stay. The definite advantage of caudal extradural bupivacaine for haemorrhoidectomy must be balanced against the rare but potentially serious complications associated with its use.

Ventilator disconnexion alarm failures. The role of ventilator and breathing system accessories.

Pressure-sensitive ventilator disconnexion alarms do not always alarm during disconnexion of a discharging compliance ventilator such as Manley Blease, unless accurately adjusted. High flows during disconnexion result in significant pressure generation caused by outflow resistance of catheter mounts, heat and moisture exchangers, capnometer cuvettes, and angled connectors; this may lead to alarm failure because of incorrectly adjusted pressure alarm limits. The exact position of the disconnexion is critical and if the alarm's pressure sensor is placed in either the inspiratory or expiratory limb of the ventilator it makes no difference to its correct function. Nine different heat and moisture exchanges were compared in the same breathing system. Those with 15-mm male connectors generate the highest pressures on disconnexion (1.1 kPa). It is suggested that the low pressure alarm limit is set only marginally below the peak inspiratory pressure, and that it is readjusted for every patient and after every change in ventilation. Most importantly, the alarm should be shown to be functional by a trial disconnexion at the tracheal tube.

A plea for noradrenaline.

Hypotension induced by nifedipine and chlorpromazine is discussed, together with the role of noradrenaline in the correction of this problem, which was resistant to other forms of therapy.

Ischaemic pain in Buerger's disease. Report of a female patient receiving long-term local analgesia.

A female patient with Buerger's disease developed severe ischaemic pain in her left index finger which was refractory to several therapeutic measures. A silastic catheter inserted in the region of the median nerve at the elbow was topped up intermittently with local anaesthetic for 6 weeks and effected excellent analgesia. The catheter was removed when the pain had abated, and the finger tip later amputated.

Anaesthetic problems in cross clamping of the thoracic aorta.

Cross clamping of the descending thoracic aorta is performed in this hospital for graft replacement of suprarenal aneurysms or during endarterectomy for extensive aortic occlusive disease. The anaesthetic management of nine patients is described and the surgical results are presented. Proximal aortic clamping and declamping lead to profound haemodynamic changes. Myocardial infarction, ventricular failure and even death may result. Renal preservation during clamping and massive blood transfusion are also problems of this surgical approach. The measures taken to ameliorate the consequences of proximal aortic clamping are discussed in detail.

Intermittent assisted ventilation. An assessment using the Retec breathing assistor.

A simple ventilator assistor was utilised in three of six patients after transthoracic repair of hiatus hernia. The device was found to be easy and convenient to use but in the pilot study produced no demonstrable improvement in respiratory function. At 10 days postoperation, the arterial oxygen tension had not risen to a preoperative level in five patients, and the FVC and FEVI were less than the values obtained before surgery in every patient.

The Retec breathing assistor. An application of fluidics to apparatus for inhalation therapy.

The Retec breathing assistor, with its gluidic valve, is an interesting method of providing assisted positive pressure inspiration, a resistive load to expiration and a capability for the administration of drugs by nebuliser. It requires some co-operation but very little training by patients, and is easily cleaned and maintained.