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Biomedical subjects

M K Gerk

Publications and source records attributed to M K Gerk.

7 recordsLinked to original sources
PubMed1981

Overall management of ruptured aneurysm: comparison of early and late operation.

The overall management results with 61 consecutive patients admitted within 3 days of subarachnoid hemorrhage from a ruptured intracranial aneurysm were analyzed. During the course of this study, the preferred method of management shifted from late surgery (planned at least 7 days after the last hemorrhage) to early surgery (within 4 days of the last hemorrhage). Ten moribund patients were excluded from analysis, leaving 24 in the late group and 27 in the early group. Both groups had comparable patient demographic characteristics and neurological conditions, and their care was supervised by one neurosurgeon (N.F.K.). A microsurgical intracranial operation was performed on all patients who survived long enough to have surgery. The intraoperative conditions and complications were similar for the two groups. The average length of follow-up was 11 months in the late and 9 months in the early group. The overall management results for the late group showed a 42% favorable outcome, a 17% unfavorable outcome, and a 42% mortality. The early group had an 81% favorable outcome, a 7% unfavorable outcome, and an 11% mortality. Patients in both good and poor conditions fared better in the early group. Seven late group patients rebled, compared to none in the early group. The number of medical complications, the length of hospitalization, and the occurrence of symptomatic vasospasm were all greater in the late group. Vasospasm in the early group occurred only postoperatively and, with the aneurysms secured, was treated more aggressively and successfully with hypertensive/hypervolemic therapy than the predominantly operative vasospasm in the late group.

Adult↗
PubMed1981

Influence of changes in arterial pCO2 on cerebral blood flow and metabolism during high-dose barbiturate therapy in dogs.

In 13 dogs the response of the cerebral circulation to changes in PaCO2 ranging from 20 to 60 torr was studied before and after administration of high doses of sodium thiopental. Infusion of sufficient barbiturate to produce 30- to 60-second burst suppression in the electroencephalogram was associated with a profound degree of cerebral vasoconstriction, equivalent to that produced by hypocapnia with PaCO2 = 20 torr. Furthermore, once sodium thiopental was administered, no significant difference in cerebral blood flow (CBF) or vascular resistance (CVR) was noted between PaCO2 of 30 and 20 torr. However, changes of approximately 15% in CBF and 30% in CVR were noted between PaCO2 at 40 and 20 torr. These data suggest that hyperventilation of PaCO2 of less than 30 torr may not effectively increase the degree of cerebral vasoconstriction in these circumstances.

Animals↗
PubMed1981

Influence of a continuous high dose infusion of mannitol on cerebral blood flow in normal dogs.

In normal dogs, the continuous infusion of 2 g of mannitol per kg resulted in a transient increase in cerebral blood flow of approximately 30%, which was accompanied by a concomitant reduction in cerebrovascular resistance. These changes were maximal 30 minutes after the infusion was initiated and resolved by 180 minutes. The changes were not related to alterations in arterial blood gases, systemic arterial or central venous pressures, or heart rate.

Animals↗
PubMed1980

Alterations in cerebral blood flow, oxygen metabolism, and electrical activity produced by high dose sodium thiopental.

High dose barbiturate therapy is being used with increasing frequency in the management of a widening spectrum of neurological disorders. Accurate regulation of the barbiturate dose is essential to maximize cerebral vasoconstriction and reduce brain metabolism while avoiding the cardiovascular depressant side effects of the drug. The purpose of this study was to determine whether the electroencephalogram (EEG) could be used to regulate administration of the agent. In nine mongrel dogs cerebral blood flow (CBF) was determined using the radioactive microsphere technique. After the determination of control CBF, a slow infusion of sodium thiopental was begun. CBF determinations were repeated when the periods of burst suppression in the EEG over several minutes averaged 30, 60, 120, and 240 seconds. CBF and oxygen metabolism showed a nearly identical pattern of a precipituos drop from control levels reaching a plateau at burst suppression between 30 and 60 seconds. Changes in cerebrovascular resistance were of a similar but opposite nature. Significant increases in heart rate occurred with burst suppression of 30 seconds, whereas the arterial pressure and cardiac index decreased with burst suppression between 30 and 60 seconds. In this study cerebral metabolic depression and vasoconstriction from sodium thiopental reached a plateau when sufficient barbiturate was administered to produce EEG burst suppression of between 30 and 60 seconds. At this level there was no important cardiovascular depression. Administration of additional barbiturates significantly decreased systemic arterial pressure and cardiac output, but produced no further decrement in the cerebral metabolic rate of oxygen or the CBF. There was no predictable relationship between cerebral metabolism or cardiovascular function and blood levels of sodium thiopental.

Animals↗
PubMedDate not supplied

The response of spinal cord blood flow to high-dose barbiturates.

The response of spinal cord blood flow (SCBF) to high-dose barbiturate therapy is documented. In nine mongrel dogs with an arterial pCO2 (PaCO2) of 40 mm Hg, sodium thiopental was administered to produce 30, 60, 120, and 240 seconds of electroencephalographic (EEG) burst suppression. At 30-second intervals of EEG suppression, cervical and thoracic cord segments demonstrated a decrease in SCBF of 47% and 39%, respectively, from control values. Isoelectric EEG intervals longer than 30 seconds were not associated with any further significant decrease in SCBF. In 13 other dogs and in the absence of barbiturates, hypocapnia to 20 mm Hg from PaCO2 of 60 mm Hg produced reductions in SCBF of 89% for the cervical and 82% for the thoracic segments. In the presence of thiopental-induced 30- to 60-second intervals of EEG silence, the decrement in SCBF in response to the same degree of hypocapnia was 83% and 75%, respectively, although the absolute value of this reduction was half that without barbiturates. These findings of a significant reduction in SCBF in response to high-dose barbiturate therapy are suggestive of a protective effect of barbiturates upon spinal cord injury as occurs in the brain. Further studies of the influence of barbiturates upon spinal cord compressive syndromes are indicated.

Animals↗
PubMedDate not supplied

The effects of high dose mannitol on cerebral blood flow in dogs with normal intracranial pressure.

In normal dogs, bolus administration of a very high dose of mannitol (2 gm/kg) resulted in a small, transient increase in cerebral blood flow (CBF) of approximately 8 percent lasting less than 10 minutes followed by a significant reduction in CBF of approximately 20 percent lasting at least three hours. The increase in CBF may in part be related to changes in cardiovascular and hematological parameters. No explanation is available for the reduction below control values but, since urine losses were not replace in these animals, changes in the state of hydration may have been responsible. It appears that the increase in CBF resulting from mannitol administered by bolus infusion are of neither sufficient magnitude nor duration to explain the protective effect observed in other studies where cerebral blood flow was reduced below ischemic levels. This suggests then, that either the effect of mannitol on CBF is quantitatively different when flow is reduced to critical levels or that the protective effect observed when the cerebral circulation is compromised is based upon a different mechanism than augmentation of flow. Further studies on the effect of mannitol on CBF in ischemic situations, where the cerebral circulation is compromised, are required.

Animals↗