ISOLATED HUMAN BLOOD PLATELETS DISCRIMINATE BETWEEN ANAESTHETIC AND NON-ANAESTHETIC GASES AT HIGH PRESSURES

We have compared the effects of the anaesthetic gases nitrogen and argon on adenosine diphosphate (ADP)-induced human blood platelet aggregation with the effects of the non-anaesthetic gas helium. All three gases showed dose-dependent inhibition of platelet aggregation. For nitrogen and argon there was a linear relationship between gas pressure and inhibition of aggregation over the range 15–68 atmospheres absolute (atm abs), whereas helium had a threshold for inhibition of approximately 34 atm abs. The inhibition by all gases was reversible after slow decompression. At pressures greater than 55 atm abs, nitrogen produced less inhibition than helium, indicating anaesthetic-pressure antagonism. Whereas pressure alone and the anaesthetic gases inhibited aggregation, the platelet shape change elicited by ADP was resistant to both nitrogen and helium, indicating that ADP binding and the early events in platelet activation were relatively unaffected by these conditions.