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Query: UMLS:C0020672 (hypothermia)
 17,327 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The factors that influence the functional integrity of the central nervous system during clinical procedures involving profoundly hypothermic circulatory arrest (PHCA) have not been objectively evaluated. Intraoperative monitoring of somatosensory evoked potentials (SEPs) was performed in nine infants undergoing PHCA during repair of congenital cardiac anomalies to investigate the short-term effects of this intervention on neurophysiologic function. Latency prolongation of the primary cortical (N18,P22) and cervical spinal cord (N13) responses, reflecting slowing of neural transmission with hypothermia, occurred as a power function of decreasing systemic temperature (p less than .01). The cortical evoked response disappeared during profound hypothermia (less than 18 degrees C), remaining absent throughout the period of circulatory arrest and for a variable period of time after reperfusion. Regression analysis indicated that the time required for the recovery of the cortical evoked response on reperfusion was a linear function of the time-temperature integral of the arrest period (p less than .001) and the pH at the onset of circulatory arrest (p less than .001). Neurologic complications occurred in three patients and included cortical blindness (n = 2) and a generalized seizure disorder (n = 1). Visual dysfunction was not reflected in the intraoperative SEP recordings, whereas prolonged delay of SEP recovery, indicative of global central nervous system injury, was observed in the patient who experienced seizures after the surgery. This preliminary experience with SEP monitoring during PHCA suggests a role for this modality in determining the short-term effects of this procedure on neurophysiologic function. The recovery characteristics of somatosensory neural transmission appear to be modulated by the duration of, and temperature and pH maintained during, the arrest period.
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PMID:Cerebral monitoring of somatosensory evoked potentials during profoundly hypothermic circulatory arrest. 674 73

Spontaneous periodic hypothermia is a rare syndrome of recurrent, centrally mediated hypothermia without an identifiable systemic cause or brain lesion. Most patients defend a temporarily lowered temperature "set point" during episodes of hypothermia, despite manifesting many well-known systemic consequences of core temperature hypothermia. No case of death directly attributable to an episode of spontaneous periodic hypothermia has been reported, although many of the serious systemic effects of hypothermia have been documented in these cases, so it is not unlikely that death may occur. The syndrome's cause, and that of Shapiro syndrome, remains unknown. Pharmacologic trials to date have been only modestly successful. Anticonvulsant agents, clonidine, and cyproheptadine appear the most likely to succeed, with cyproheptadine being a reasonable first choice. Given that the term "spontaneous periodic hypothermia" describes a syndrome, and not a pathophysiologic mechanism, it is likely to encompass a common eventuality, arrived at via several different pathways. One can postulate mechanisms such as structural abnormalities, trauma, infection, irritation, and degeneration involving strategic locations which create a focus for epileptic or other periodic dysfunction whose scope involves the centers for thermoregulation. The existence of 2 distinct, oppositional thermoregulatory centers would allow for speculation of similar mechanisms accounting for cases of both periodic hypo- and hyperthermia (61). Postmortem data regarding the hypothalamic and surrounding areas from future cases of Shapiro syndrome and spontaneous periodic hypothermia would be of great interest. Further, more sensitive in vivo testing methods are clearly needed. The role of PET or single photon emission computed tomography (SPECT) with technetium 99m-labeled hexamethylpropylene amine oxime (Tc 99m HMPAO) performed acutely during an episode remains to be characterized (64, 103, 105). The term "diencephalic epilepsy" may in fact be accurate, given the periodic episodes of the case presented here and similar cases resulting from non-generalized seizure activity, with or without an underlying predisposing lesion. The label diencephalic epilepsy has been merely speculative so far, however, as definitive evidence of seizure activity has not been documented. Further, it is expected that the descriptive terms "spontaneous periodic hypothermia" and "episodic spontaneous hypothermia with hyperhidrosis" will outlive their usefulness as researchers gain greater understanding of this syndrome, and be replaced with a more pathophysiologically meaningful nomenclature.
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PMID:Spontaneous periodic hypothermia. 756 67