Control Group: (n = 69, 51 analysed): oxygen 100% inhaled for five minutes
Experimental Group: (n = 69, 61 analysed): nitrous oxide 35% inhaled for five minutes
Administration of ordinary analgesics was not restricted.
74% followed for ?

The evidence

Myocardial infarction: nitrous oxide relieved pain.

Clinical bottom line (level 2b)

  1. Patients with an acute myocardial infarction who are given nitrous oxide were more likely to have pain relief, than those given oxygen alone.
Thompson and Lown: Journal of the American Medical Association 1976; 235 (9): 924-927
Expires January 2005

The study

Double-blinded ?concealed randomised cross-over trial without intention-to-treat
Setting: coronary care unit of a general hospital, USA

69 patients (aged ?, ?% male) pain typical of myocardial infarction

Excluded if
  • in severe distress, needing immediate relief
  • pain at admission


    • Control Group: (n = 69, 51 analysed): oxygen 100% inhaled for five minutes
    Experimental Group: (n = 69, 61 analysed): nitrous oxide 35% inhaled for five minutes
    Administration of ordinary analgesics was not restricted.
    74% followed for ?

    The evidence

    Outcome Time to outcome CEREERRRR
    (95% CI)    		ARR
    (95% CI)    		NNT
    (95% CI)
    no pain relief unknown 36
    (70.6%)    		 16
    (26.2%)    		 63%
    (41% to 76%)    		 44.4%
    (27.7% to 61.0%)    		 2
    (2 to 4)

    Comments

    1. Follow-up was only 74% as 69 patients were entered into the trial, but data was only reported on 51 patients in the control group (although it was 61 in the experimental group). There was no indication as to where the other 18 patients had gone.
    2. It was unclear as to whether the percentages of pain relief referred to the number of patients (51) or the number of episodes of pain (61). The percentages were taken to refer to the number of patients.

    Citation

    1. Thompson PL, and Lown B: Nitrous oxide as an analgesic in acute myocardial infarction. Journal of the American Medical Association 1976; 235 (9): 924-927
    Contributor: Clare Wotton and Bob Phillips, January 2000
    Reviewer:

    Clinical Question.
    Patient myocardial infarction
    Intervention or Exposure nitrous oxide
    Comparison oxygen
    Outcome pain relief
Outcome Time to outcome CEREERRRR
(95% CI)		ARR
(95% CI)		NNT
(95% CI)
no pain relief unknown 36
(70.6%)		 16
(26.2%)		 63%
(41% to 76%)		 44.4%
(27.7% to 61.0%)		 2
(2 to 4)

Comments

  1. Follow-up was only 74% as 69 patients were entered into the trial, but data was only reported on 51 patients in the control group (although it was 61 in the experimental group). There was no indication as to where the other 18 patients had gone.
  2. It was unclear as to whether the percentages of pain relief referred to the number of patients (51) or the number of episodes of pain (61). The percentages were taken to refer to the number of patients.

Citation

  1. Thompson PL, and Lown B: Nitrous oxide as an analgesic in acute myocardial infarction. Journal of the American Medical Association 1976; 235 (9): 924-927
Contributor: Clare Wotton and Bob Phillips, January 2000
Reviewer:

Clinical Question.
Patient myocardial infarction
Intervention or Exposure nitrous oxide
Comparison oxygen
Outcome pain relief