THE VALUE OF BLOOD-GAS ANALYSIS IN OUT-OF -HOSPITAL SETTINGS - PART 1

Prehospital blood gas analysis is a new method in out-of-hospital emer gency care. In a prospective pilot study we evaluated the feasibility of prehospital compensation of severe acidosis relying on different mo nitoring systems to evaluate patients oxygen, carbon dioxide or acid-b ase status, respectively. Methods: With the help of arterial blood gas checks taken at the site of the emergency, the acid base status of pa tients undergoing out of hospital cardiopulmonary resuscitation was an alysed. The values derived from the first arterial puncture were used to determine the presence and the type of acidosis. The data of the ar terial blood gas checks were set into relation with the time elapsed s ince the beginning of resuscitation and they were compared with end-ti dal CO2. Results: During the observation period 26 blood gas analyses from patients who had out-of-hospital resuscitation because of cardiac arrest were done. Twenty three patients had severe acidosis (pH range <6.9 to 7.31), one had alkalosis (pH 7.51). Only two had an arterial pH within normal range. The pCO(2) was variable (range: 24 to 97 mm Hg ). The correlation of pH with time from the beginning of resuscitation to arterial puncture was poor (r=0.407, p<0.05). There was no correla tion between pH and BE(r=0.267) or pH and pCO(2), (r=0.016) respective ly. Prehospital capnometry had a poor correlation with arterial pCO(2) in most emergeny patients. Only patients with respiratory disturbance s of extrapulmonary origin showed a good correlation between end-tidal CO2 and the arterial pCO(2). In severely ill patients the arterio-alv eolar CO2-difference was unexpectedly high (>15 mm Hg). ln four patien ts resuscitation was not sucessful until compensation of an unexpected ly severe acidosis based upon the findings from blood-gas analysis had been performed. Conclusions: Arterial blood gas analysis proved to be helpful in the optimal management of out of hospital cardiac arrest. The incidence of severe acidosis in patients undergoing cardiopulmonar y resuscitation was 80%. The probability of developing acidosis was fo und to increase slightly depending on the time elapsed since the begin ning of CPR. The application of a calculated buffering of acidosis wit h sodium bicarbonate showed a good outcome in selected cases. ln emerg ency patients alternative methods fail to detect severe disturbances o f the patients oxygen and/or carbon dioxide status and the acid-base b alance. Management of prehospital cardiac arrest could be optimized by the routine use of blood gas analysis.