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Biomedical subjects

J G McComb

Publications and source records attributed to J G McComb.

119 records · Page 7Linked to original sources
PubMed1979

Influence of nitroprusside on cerebral pressure autoregulation.

The authors studied 10 cats to assess the question of abolition of cerebral autoregulation attendant on the use of nitroprusside for hypotensive anesthesia. After the establishment of stable base line parameters, a continuous infusion of sodium nitroprusside was begun in a dose sufficient to maintain a mean systemic arterial pressure of 65 mm Hg. Infusion was continued for incremental periods of 30 seconds to 10 minutes, increasing the time of infusion by 30 seconds after each subsequent trial. At 10 seconds after the cessation of nitroprusside administration, intravenous dopamine was infused to raise the systemic arterial pressure to a mean of 100 mm Hg, and the subsequent response in intracranial pressure was recorded in each instance. In no animal was a loss of cerebral autoregulation noted when the nitroprusside infusion was maintained for 3 minute or less. When the infusion was maintained for 4 minutes or longer, cerebral autoregulation was lost in each animal, and the length of time to return of cerebral autoregulation correlated with the duration of nitroprusside infusion. Sodium nitroprusside disturbs the integrity of cerebral pressure autoregulation, and the onset and extent of this disturbance is a dose-dependent phenomenon.

Animals↗
PubMed1976

The effect of cerebrospinal fluid pressure on the size of drainage pathways.

The cerebrospinal fluid drainage pathways were studied using labeled molecules of different sizes. Following determination of the limiting size, the cerebrospinal fluid pressure was raised above the normal range and changes in transfer were measured. These data show that molecules smaller than the limiting size will transfer at an increased rate in response to elevated pressures. Larger molecules did not demonstrate an increased transfer with raised cerebrospinal fluid pressures, suggesting that the pathways did not enlarge.

Animals↗
PubMed1975

Further studies on the difference between ventricular and subarachnoid perfusion.

In order to study the exchanges between the subarachnoid fluid and the adjacent cortical tissue independently of the choroid plexus, artificial cerebrospinal fluid (CSF) was perfused from the supracallosal cistern to the cisterna magna in the rabbit. Test substances were introduced into the blood and held at a constant level. The degree of penetration by the blood-borne test substances into the artificial CSF perfused into the cortical subarachnoid space was noted. The degree of penetration of these test substances into the artificial CSF does not solely reflect rates of exchange between this fluid and the exposed cortex for it was shown histologically as well as physiologically that the artificial CSF does not remain in the subarachnoid space but also enters the subdural space to exchange with the blood via the dural capillaries. Thus this experimental model routinely produces an artefactual situation which restricts its use in the study of CSF-brain relations.

Animals↗
PubMedDate not supplied

Central nervous system malformations and the VATER association.

Four patients with findings compatible with the VATER association having a malformation of the central nervous system requiring neurosurgical intervention are reviewed. Each patient has a different neurosurgical lesion, one of which has not been hitherto described as occurring with the other anomalies of the association. We suggest that all patients with the VATER association be evaluated carefully for malformations having neurosurgical implications.

Abnormalities, Multiple↗
PubMedDate not supplied

Early CT detection of intracranial seeding from medulloblastoma.

Since 1975, intracranial subarachnoid metastases of medulloblastoma have been detected in seven of 23 initial contrast-enhanced computed tomographic (CT) scans in children with proven medulloblastoma. Furthermore, four of the seven cases with subarachnoid seeding were diagnosed after the introduction of high-resolution contrast-enhanced CT. Only three cases of seeding had been detected in the previous 17 low-resolution cases studied with CT. Thus, it is quite likely that the incidence of subarachnoid metastases may be substantially more than the overall figure of 30% indicated by this series. This may have an impact on the treatment of these patients, since the frequent appearance of metastases may indicate the need for more vigorous chemotherapeutic regimens. One should be aware of the possibility of early intracranial subarachnoid seeding and that it can be demonstrated by contrast-enhanced CT. This is particularly true when using high-resolution scanners in conjunction with 5 mm sections through the posterior fossa.

Adolescent↗