EXPERIMENTAL ISCHÆMIA: SENSORY PHENOMENA, FIBRILLARY TWITCHINGS, AND EFFECTS ON PULSE, RESPIRATION, AND BLOOD-PRESSURE

¹ Physiological Laboratory, University of Aberdeen, and the Department of Physiology, Prince of Wales Medical College, Patna

1. An account is given of the phenomena observed in limbs with ischæmia of about fifteen to thirty-five minutes' duration, and also in the post-ischæmic period.

2. Ischæmia per se is not associated with any notable sensory phenomena beyond a feeling of numbness, provided the limb is kept warm and the occluding pressure is not more than about 30 mm. Hg above the systolic pressure.

3. Serial contractions of ischæmic muscle set up continuous severe pain localised over the belly of the muscle. Static contraction of ischæmic muscle is also accompanied by pain of similar distribution, but of less extent and severity. The pain disappears almost immediately after re-establishment of the circulation, and is probably due to the effects of metabolites.

4. The effects on blood-pressure of simple ischæmia and of ischæmia associated with serial and static muscular contractions are dealt with.

5. Within one to two minutes following the re-entry of blood into a limb after ischæmias lasting fifteen to thirty-five minutes, an intense "pins and needles" sensation with hyperæsthesia develops; this rapidly reaches a maximum, and passes off in about ten minutes. Fibrillary twitchings are almost simultaneously evident (particularly in the small muscles of the hand), which cease shortly before the complete cessation of the sensory phenomena. These sensory and motor phenomena are phases in the recovery of nerve-endings and of muscle fibres respectively.

6. A relationship of the fibrillary twitchings to diminution in muscle calcium is indicated by observations on the muscles of the post-ischæmic limbs of animals and on that of the blood calcium.

7. Metabolites from the ischæmic limb pass into the blood and increase the depth of respiration and slow the pulse-rate.

I have pleasure in acknowledging my indebtedness to Professor J. A. MacWilliam for much kindly help and criticism.