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Emergency care

The pain relieving effects of ENTONOX are rapid, being felt after only four to five breaths. They also disappear quickly once administration of the gas ceases. Furthermore, ENTONOX has the benefit of a non-invasive mechanism of delivery, few side effects or contraindications and is simple to use. These properties make ENTONOX an ideal analgesic for treating patients in the pre-hospital setting as well as in accident and emergency departments (6). Adequately trained healthcare professionals can safely administer ENTONOX in the pre-hospital setting.

Proven value of a short-acting analgesic 

One of the first papers to examine the use of ENTONOX in a pre-hospital setting, for self-administration by patients in severe pain, found it to be well tolerated and effective in reducing pain and anxiety (1). Subsequent studies have proven the value of a short-acting analgesic with minor complications or negative side effects.

In 1982, Donen et al. studied 240 patients who received ENTONOX (2). More than 90% of those with traumatic chest, abdomen or back pain, experienced reduced pain. Apart from slight drowsiness, few side effects were noted (3).

Quicker turnaround of patients 

In busy accident and emergency departments time is of the essence in treating patients, and an analgesic with rapid onset and offset can be invaluable. In 2007 Descamps et al demonstrated that first line ENTONOX use, with or without simple oral analgesia, was associated with significantly shorter time spent in the emergency department compared to intravenous morphine and/or midazolam for the reduction of acute traumatic dislocated shoulder. Results showed that use of morphine and/or midazolam was associated with significantly prolonged transit times (177 minutes) through the emergency department compared to ENTONOX (77 minutes). (7)

Benefits for the Ambulance Service 

ENTONOX therapy has the added benefit of not affecting subsequent diagnosis or ongoing treatment of the patient once they arrive at the hospital.

At the scene of an accident the patient may be difficult to reach to allow injectable pain relief to be administered. Whilst fire and rescue emergency services concentrate on getting the patient out ENTONOX inhalation equipment can be passed to the patient for effective pain relief.

Management of pain in trauma care is important; not only to avoid unnecessary suffering, but also to prevent anxiety and distress that may lead to deterioration of the patient. ENTONOX will not mask any underlying symptoms that can help with later diagnosis and treatment.

Analgesia for acute heart attack 

Nitrous oxide has only minor cardiovascular effects in patients with coronary artery disease. Both Thornton et al. and Wynne et al. found very little effect on the circulatory system from 50% nitrous oxide (4, 5). Wynne even speculated that the weak myocardial depressant effect of nitrous oxide could be of value from the perspective of myocardial oxygen balance. However, ENTONOX should be used with caution in patients with heart failure or severe cardiac dysfunction (e.g. after heart surgery).

(1) Baskett P, Withnell A. Use of ENTONOX in the ambulance service. Br J Med 1970; 2:41-43.
(2) Donen N et al. Pre-hospital analgesia with ENTONOX, Can Anaesth Soc J 1982; 29(3):275-9.
(3) Faddy SC, Garlick SR. A systematic review of the safety of analgesia with 50% nitrous oxide: Can lay responders use analgesic gases in the prehospital setting? Emerg Med J 2005; 22:901-908. Review.
(4) Thornton JA. Cardiovascular effects of 50% nitrous oxide and 50% oxygen mixture. Anaesthesia 1973; 28:484-9
(5) Wynne J et al. Hemodynamic effects of nitrous oxide administered during cardiac catheterization. JAMA 1980; 243: 1440-3.
(6) O’Sullivan I, Benger J. nitrous oxide in emergency medicine. Emerg Med J 2003; 20:214-17.
(7) Descamps MJL, Gwilym S, Weldon D, Holloway V. Accident and Emergency Nursing 2007;15:223-227

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