Parkinson’s disease is characterized by preferential degeneration of the
dopamine-producing neurons of the brain stem substantia nigra. Imbal-ances between mechanisms governing dopamine transport across the
plasma membrane and cellular storage vesicles increase the level of toxic
pro-oxidative cytosolic dopamine.
The safe upper limit for vitamin B6 has been set at 100 mg/d, although no adverse effects have been associated with high intakes of vitamin B 6 from food sources only. When toxicity occurs, it causes a severe sensory neuropathy, leaving patients unable to walk. Some cases of photosensitivity and dermatitis have also been reported.
Folate, Vitamin B12 See Chap. 90.
Vitamin C Both ascorbic acid and its oxidized product dehydroascorbic acid are biologically active.
When a patient is hypothermic, target organs and the cardiovascular system respond minimally to most medications. Moreover, cumulative doses can cause toxicity during rewarming because of increased binding of drugs to proteins, and impaired metabolism and excretion. As an example, the administration of repeated doses of digoxin or insulin would be ineffective while the patient is hypothermic, and the residual drugs are potentially toxic during rewarming.
Achieving a mean arterial pressure of at least 60 mmHg should be an early objective.