Quality of pre-hospital emergency ventilation in patients with severe head injury

M. J. Richards1, D. J. Lockey1 and M. Helm2

1 Bristol, UK and 2 Ulm, Germany

Editor—We would like to comment on the article by Helm and colleagues,1 in which two specific outcomes of out-of-hospital ventilation, oxygenation and ventilation are investigated. The article concluded that tracheal intubation and controlled ventilation in the pre-hospital setting do not guarantee optimal oxygenation or ventilation. Optimal oxygenation was achieved in 85.2% of patients. In 1996, Stocchetti and Furlan2 demonstrated that 57% of patients with head trauma had an arterial oxygen saturation <90% at the scene of the accident. If this patient group is similar, the system that Helm and colleagues describe provides excellent improvement in the on-scene oxygenation of head-injured patients, especially as some of the poorly oxygenated patients had significant chest injuries and might well have been difficult to oxygenate, even in the hospital intensive care setting. With regard to ‘adequate ventilation’, we accept that, while capnography can be difficult to interpret in the hypovolaemic patient or those with severe lung contusion, it still provides invaluable information. In addition to providing evidence of appropriate ventilation, capnography also provides confirmation of tracheal intubation and detection of disconnection. Both the Intensive Care Society,3 and the Association of Anaesthetists,4 have produced guidelines for transfer of the critically ill. Both organizations advise the use of capnography. We see no reason why primary transfers of the critically ill should have lower standards than secondary transfers, particularly in doctor-led systems. Lastly, the authors comment that blood gas analysis is the gold standard in ventilatory monitoring, but is impractical in the pre-hospital setting. This is usually the case, but with the advent of hand-held devices that can perform blood gas analysis as well as other blood tests, it may be that in the few patients with prolonged scene times or long transfers, this level of monitoring may become practical.

M. J. Richards

D. J. Lockey

Bristol, UK

Editor—First of all, we would like to thank Drs Richards and Lockey for their comments on our article.1 We agree totally with their recommendations and have followed them on a routine basis in our emergency medical service in Ulm, Germany for 3 yr!

With regard to ‘adequate ventilation’, capnography can be difficult to interpret in the hypovolaemic trauma patient or those with severe lung contusion.5 6 The use of capnography for controlling artificial ventilation is therefore limited in this group of trauma patients. However, we agree that capnography provides confirmation of tracheal intubation and detection of disconnection, and that its routine use should be recommended as a monitor of safety in ventilated patients in the pre-hospital setting. Capnography has been mandatory in any ventilated patient received into our emergency medical service for nearly 3 yr.

Blood gas analysis is the gold standard in ventilatory monitoring. In the pre-hospital setting, especially in primary rescue missions of traumatized patients, it seems to be impractical as a monitoring method on a routine basis because it is invasive, time-consuming and non-continuous. Again we agree with Drs Richards and Lockey when they recommend blood gas analysis in the few cases with prolonged scene times or long transfers. We have been performing blood gas analysis, as well as determination of haematocrit and plasma electrolytes, in such cases using a hand-held blood gas analyser (i-Stat; Hewlett Packard) on a routine basis for more than 2 yr.

M. Helm

Ulm, Germany

References

1 Helm M, Hauke J, Lampl L. A prospective study of the quality of pre-hospital emergency ventilation in patients with severe head injury. Br J Anaesth 2002; 88: 345–9[Abstract/Free Full Text]

2 Stocchetti N, Furlan A, Volta F. Hypoxaemia and arterial hypotension at the accident scene in head injury. J Trauma 1996; 40: 764–7[ISI][Medline]

3 Intensive Care Society. Guidelines for Transport of the Critically Ill Adult. Intensive Care Society, 1997

4 Association of Anaesthesists. Recommendations for the Transfer of Patients with Acute Head Injuries to Neurosurgical Units. Association of Anaesthesists, 1996

5 Morley AP. Pre-hospital monitoring of trauma patients: experience of an emergency helicopter medical service. Br J Anaesth 1996; 76: 726–30[Free Full Text]

6 Helm M, Hauke J, Lampl L, Sauermüller G, Bock KH. Arterial to end-tidal carbon dioxide gradient and Horovitz-quotient—of value in diagnosing blunt chest trauma? Br J Anaesth 1995; 74: 127





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