title: Effect of epinephrine on the ability of end-tidal carbon dioxide readings to predict initial resuscitation from cardiac arrest.
abstract: OBJECTIVE
  To determine if the administration of epinephrine changes the partial pressure of end-tidal CO2 during cardiac arrest, as previously reported. Such a change could diminish the demonstrated ability of end-tidal CO2 measurements to predict resuscitation from cardiac arrest.
  
  
  METHODS
  The partial pressures of end-tidal CO2 of adult cardiac arrest patients who received i.v. epinephrine in doses from 1 to 15 mg were monitored throughout arrest.
  
  
  METHODS
  Emergency department of a university hospital.
  
  
  METHODS
  Adults (n = 64) in cardiac arrest with a mean age of 70 +/- 12 yrs, of whom 35 were males and 15 had a mean time of return of spontaneous circulation of 6.5 +/- 11 hrs.
  
  
  METHODS
  End-tidal CO2 (in torr) was analyzed on arrival, before the first dose of epinephrine, and 4 mins after epinephrine was administered in varying doses chosen by the supervising physician.
  
  
  RESULTS
  The end-tidal CO2 decreased an average of 0.3 torr (0.04 kPa) after epinephrine was administered. Patients with a return of pulse had a decrease of -2 torr (-0.3 kPa) vs. an increase of 0.3 torr (0.04 kPa) for those patients with no return of pulse (p = .07). In 33% of patients, there was no change; in 28%, the partial pressure of end-tidal CO2 increased, and in 39%, it decreased. There was no correlation between the change in end-tidal CO2 after epinephrine and whether or not patients regained a pulse (r2 = .08, p = .07), although a decrease in end-tidal CO2 was most often associated with return of pulse. At a threshold of 10 torr (1.3 kPa), the first end-tidal CO2 had a positive predictive value for return of pulse of 50% and a negative predictive value of 82%. Just before epinephrine administration, the positive predictive value was 71% and the negative predictive value was 83%; 4 mins after epinephrine administration, the positive predictive value was 64% and the negative predictive value was 86%. A decrease in end-tidal CO2 after epinephrine had a positive predictive value of 53% and a negative predictive value of 92%. End-tidal CO2 readings predicted resuscitation most accurately when taken after initial stabilization and before administration of epinephrine.
  
  
  CONCLUSIONS
  Although epinephrine administration may decrease end-tidal CO2 tensions in cardiac arrest, it does so unpredictably in individual patients, and it does not eliminate the predictive value of this measurement.
authors.affiliation: Department of Medicine, University of California, San Francisco.
authors.forename: M
authors.initials: M
authors.lastname: Callaham
authors.forename: C
authors.initials: C
authors.lastname: Barton
authors.forename: M
authors.initials: M
authors.lastname: Matthay
mesh_terms: D000368:Aged; D001639:Bicarbonates / Q000627:therapeutic use; D002245:Carbon Dioxide / Q000378:metabolism*; D004837:Epinephrine / Q000627:therapeutic use*; D005260:Female; D006323:Heart Arrest / Q000628:therapy*; D006801:Humans; D008297:Male; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012151:Resuscitation; D013990:Tidal Volume / Q000187:drug effects
chemical_list: D001639:Bicarbonates; D002245:Carbon Dioxide; D004837:Epinephrine