Acute increased intracranial pressure in rabbits caused by inflation of an extradural balloon was associated with a sequential alteration in vital signs. As the balloon was inflated with small increments of saline, the intracranial pressure rose. The first few increments were not usually associated with a sustained rise in intracranial pressure. As the intracranial pressure was raised with additional increments, the vital signs altered in the following order. As the first increments were added, the respiratory rate decreased. Further inflation of the balloon was associated with a definite reduction of the pulse rate and marked slowing of the respiration. As the respirations became slower, with the increasing intracranial pressure their amplitude increased. At this stage, later than the onset of respiratory change, further increment was sufficient to give a sudden parallel rise of the intracranial and arterial pressures. With this parallel rise of pressures the respiration became short and shallow associated with periods of apnea. Pulse rate usually increased as the arterial pressure rose. A transient sudden rise of venous blood pressure was observed when the arterial pressure rose suddenly parallel to rise of intracranial pressure. If the balloon was not deflated the arterial pressure declined, the pulse rate decreased significantly and periods of apnea occurred. Thereafter the intracranial and systemic arterial pressures gradually declined along with a reduction of the pulse rate. Respiration ceased and finally the heart stopped.
Apnea ; Arterial Pressure ; Brain* ; Heart ; Heart Rate ; Inflation, Economic ; Intracranial Pressure* ; Rabbits ; Respiration ; Respiratory Rate ; Venous Pressure ; Vital Signs