Biochemical and biophysical changes in guinea pigs after acute head injury

Animal experiments were set up mainly to derive additional diagnostic data from the study of biochemical changes after acute head injury. In standardized experiments guinea pigs were subjected in groups of 20 to three identical head injuries, each of either 1.0 J or 1.5 J intensity. The trauma was likely to result in a concussion or contusion syndrome similar to that found in man; 40 animals served as controls. During the 60 min after injury observation and measurement of body functions did not reveal signs of a shock-like condition or hypoxaemia in the traumatized animals compared with control animals. Superficial anaesthesia probably did not influence the findings. Temperature and respiration were altered significantly in all the animals receiving head injuries. Blood gas analysis showed a decrease of standard bicarbonate only after the 1.5 J injury but even though hypoxaemia was not present 2,3-diphosphoglycerate values and P50 increased, compared with the control animals. The fall of plasma lipid concentrations reported probably had to be seen as a sympathomimetic effect of the minor (1.0 J) trauma. Of special significance was the increased activity of malate dehydrogenase and aldolase, found only in the blood of severely traumatized animals, as this could serve as an early diagnostic aid for evaluating head injuries.