1 108

Correspondence The role of the laryngeal mask in prehospital trauma care

I read with interest the two case reports on the use of the laryngeal mask airway (LMA) in prehospital trauma care by Greene, Roden and Hinchley (Anaesthesia 1992; 47: 688-9). I am pleased that the LMA is increasingly being considered for emergency airway management when intubation of the trachea proves impossible. The degree of protection against aspiration provided by the LMA remains unproven, but as the authors stated, there is some evidence that it is, at least, partially protective [I]. In the prehospital care of trauma victims (and indeed other critically ill patients), adequate tissue oxygenation is the therapeutic priority. Therefore, in situations where tracheal intubation is not possible, the LMA is a useful alternative. It has been shown that paramedical personnel can easily learn to use the LMA and insert it rapidly with only a small failure rate (94% success rate at first insertion) 121. The second-line intervention for airway maintenance in North America is the oesophageal obturator airway (OOA) and, to date, there have been no studies directly comparing the OOA with the LMA. However the OOA is associated with recognised complications (tracheal obturation, oesophageal perforation and aspiration of stomach contents on removal) and is not available in paediatric sizes [3]. The OOA also requires neck flexion for insertion and is contraindicated in cervical spine trauma, whereas the LMA can be inserted with no neck movement. There has been one small field study examining the use of

the LMA in prehospital trauma care, but it only investigated 25 patients and there was no clinical information about these patients. However it did confirm the high success rate of insertion of the LMA in the field 141. Insertion of the LMA is a very valid second-line manoeuvre when intubation of the trachea is not possible during prehospital emergency care. I believe LMAs should be available wherever advanced life support is carried out (including in ambulances) and that when paramedical personnel are taught tracheal intubation they should also be taught how to use the LMA.

Royal Berkshire Hospital, Reading, Berkshire RCI 5AN

M.B. WALKER

References [I] JOHN RE, HILL S. HUGHESTJ. Airway portection by the laryngeal mask. A barrier to dye placed in the pharynx. Anaesthesia 1991; 46: 366-7. [2] PENNANT JH. WALKER MB. Comparison of the endotracheal tube and laryngeal mask in airway management by paramedical personnel. Anesthesiology 1992; 7 4 53 I 4 [3] SCHWARTZ AJ, CAMPBELL FW. Cardiopulmonary resuscitation. In: Barash PG, Cullen BF, Stoelting RK, eds. Clinical anesthesia. Philadelphia: Lippincort, 1989: 1477-1515. [4] DE MELLOWF, WARDP. The use of the laryngeal mask airway in primary anaesthesia. Anaesthesia 1990; 4 5 793-794.

Laryngeal mask airway and low flow anaesthesia We would like to describe our experience combining the Brain laryngeal mask airway and low flow anaesthesia. Twenty patients suitable for anaesthesia with a laryngeal mask airway were chosen. Following induction with propofol a laryngeal mask was inserted and its correct position ascertained. The patient was allowed to breathe spontaneously through a circle system with a carbon dioxide absorber. Anaesthesia was maintained with nitrous oxide, oxygen and isoflurane. A fresh gas flow of 4:2 1.min-I N 2 0 : 0 2 was reduced after 15 min to 2 : l I.min-’ N,O:O,, and then 5 min later to 1 : l 1.min-I N 2 0 : 0 2This . has been shown to safeguard against hypoxia developing in the circle due to the differential nitrous oxide and oxygen uptake by the patient. No case lasted more than 2 h. End-tidal carbon dioxide concentration was measured with a calibrated Datex capnograph and in none of the patients increased to more than 6%. Oxygen saturation was measured with a Novametrix 505 and did not dccrcase below 95%.

This technique combines the advantages of a laryngeal mask airway with those of a circle system. The economical aspect of this arrangement should be emphasised as the cost of the volatile agents used in the main operating theatres of a district general hospital (f 56 000 per annum) could be halved by the use of a low flow technique in the operating theatre and normal high flows in the anaesthetic room [I].

University Hospital of Wales, Cardiff CF4 4XW

M.R.W. STACEY A. SHAMBROOK

Reference [l] COTTERSM, PETROS AJ. DORECJ, BARBER ND, WHITEDC. Low-flow anesthesia: Practice, cost implications and acceptability. Anaesthesia 1991. 46: 1009-12.

Nil by mouth after midnight? We modified pre-operative fasting guidelines at Foothills Hospital, Calgary, Alberta, Canada in 1988 following publication of the studies quoted by Dunnett and Zorab (Anaesthesia 1992, 47: 638). The Department of Anaesthesia agreed unanimously that instructions for ambulatory (day surgery) patients should be modified to read:- ‘Do not eat any solid food after midnight. On the morning of surgery you should drink a cup (6 oz = 150 ml) of coffee or tea, or a glass (6 oz = 150 ml) of apple juice or water 3 h before your scheduled time of surgery.’ In a follow-up study of 211 patients [I], 73% had taken

advantage of the relaxed guidelines. The remainidg 27% were not thirsty, thought the drink might cause nausea or vomiting postoperatively, or their surgeon had insisted on the old guidelines. Change of guidelines for inpatients was more difficult because of nurses following the last order to be written. If a surgeon wrote the order “PO after midnight’ later than the anaesthetist wrote ‘clear fluids until 3 h pre-operatively the surgeon’s order was followed and vice versa. To overcome this confusion, the heads of the Departments of Anaesthesia and Surgery wrote a joint letter to all members

Laryngeal mask airway and low flow anaesthesia.

1 108 Correspondence The role of the laryngeal mask in prehospital trauma care I read with interest the two case reports on the use of the laryngeal...
122KB Sizes 0 Downloads 0 Views