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Biomedical subjects

J C Torner

Publications and source records attributed to J C Torner.

At least 91 records · Page 5Linked to original sources
PubMed1985

Direct spinal cord stimulation and recording in hemorrhagic stock.

Somatosensory evoked potentials (SSEPs) have been used extensively to evaluate the central nervous system. A limitation of using SSEPs is that the peripheral nervous system is intrinsically linked to the production of these potentials. Peripheral nerve ischemia and neuropathies have been shown to result in changes in SSEPs that may be misinterpreted as showing a pathological condition in the central nervous system. Our experimental paradigm was designed to study the practicality and possible benefits of obtaining spinal evoked potentials (SEPs) by direct cord stimulation and recording. Twelve lambs underwent laminectomies at C-7 and L-1. Epidural electrodes were placed at each level. Each lamb was then bled to produce mean arterial pressures of 80, 60, 40, and less than or equal to 30 mm Hg. At each of these designated pressures, SEPs were obtained by direct cord stimulation and recording. At the same time, spinal cord blood flow was measured using the radioactive microsphere technique. The spinal cord blood flow remained constant down to a mean arterial pressure of 40 mm Hg, whereas blood flow to the peripheral nerve and renal cortex decreased with the mean arterial pressure. SEPs produced by this method did not vary in terms of latency or amplitude over mean arterial pressures ranging from 100 to 30 mm Hg. We conclude that SEPs produced by direct cord recording and stimulation constitute a method of assessing cord viability free of the variables attributable to the peripheral nervous system.

Animals↗
PubMed1985

The natural history of aneurysms and arteriovenous malformations.

The authors summarize the findings of previous studies relating to the natural history of aneurysms and arteriovenous malformations (AVM's). Ruptured aneurysms have their highest rate of rebleeding on Day 1, and at least 50% will rebleed during the 6 months after the first hemorrhage. Thereafter, the rate drops to at least 3% a year. This is the same rate as seen in anterior and posterior communicating artery aneurysms treated by anterior cerebral artery clipping and carotid ligation; these operations provide immediate protection but do not result in long-term diminution of the risk of rebleeding. Patients with unruptured incidental and unruptured multiple aneurysms rebleed at a rate of 1% per year, as do patients with subarachnoid hemorrhage of unknown etiology. The risk of rebleeding for AVM's is 3% a year.

Cerebral Hemorrhage↗
PubMed1984

Prevalence of diabetes mellitus among patients with subarachnoid hemorrhage.

Diabetes mellitus is generally accepted as an important risk factor in cerebrovascular disease. The importance of this condition varies with the type of stroke. Patients with aneurysmal subarachnoid hemorrhages (SAHs) have a lower or equivalent prevalence of diabetes mellitus than the general population. In particular, insulin-dependent diabetes is rarely present prior to aneurysmal rupture. These observations suggest that diabetic patients are not at increased risk for aneurysmal SAH.

Adolescent↗
PubMed1984

Cooperative study of intracranial aneurysms and subarachnoid hemorrhage: a long-term prognostic study. II. Ruptured intracranial aneurysms managed conservatively.

The late natural history of ruptured intracranial aneurysms was studied in 568 cases reported to the Cooperative Study of Intracranial Aneurysms and Subarachnoid Hemorrhage from 1958 to 1965. The patients had been selected for conservative management of their aneurysms at the time of diagnosis. A follow-up search in 1981 and 1982 revealed 378 known deaths; 40% had occurred within six months of hemorrhage. During the next two decades, the patients' survival probabilities were significantly worse than those of a matched US population. Multiple aneurysms did not differ prognostically from single aneurysms, but posterior circle aneurysms carried a better prognosis after ten-year survival. The rate of probable recurrent bleeding after six months was 2.2% per year for the first 9 1/2 years and 0.86% per year for the second decade. Reported rebleeding episodes were fatal in 78%.

Adolescent↗
PubMed1984

Cooperative study of intracranial aneurysms and subarachnoid hemorrhage: a long-term prognostic study. III. Subarachnoid hemorrhage of undetermined etiology.

Among 6,638 cases reported to the Cooperative Study of Intracranial Aneurysms and Subarachnoid Hemorrhage were 477 cases in which the cause of hemorrhage could not be determined after carotid and vertebral angiography. These patients were followed up for up to 24 years after hemorrhage. Twenty patients were subsequently found to have an aneurysm or arteriovenous malformation missed by the first angiographic survey. After six-month survival, the rate of recurrent hemorrhage was a maximum 0.86% per year. Survival was significantly better than that of patients with verified ruptured aneurysms managed conservatively in this cooperative study. For normotensive patients who survived the first six months, the life expectancy for the next 20 years equaled that of an age- and sex-matched US population. Hypertensive patients had a higher mortality than normotensive patients.

Adult↗
PubMed1984

Effects of naloxone on canine cerebral vascular smooth muscle.

The pharmacological effects of naloxone on cerebral arterial smooth muscle in vitro were examined using canine basilar arterial strips. Naloxone exerted two different effects on canine basilar artery: (1) at a high concentration (3 X 10(-4) M) it produced nonspecific vasodilation, and (2) at lower concentrations (3 X 10(-7), 3 X 10(-6), and 3 X 10(-5) M) it inhibited the vasoconstrictor effects of norepinephrine without altering KCl-, serotonin-, or hemoglobin-induced constriction. Morphine (2 X 10(-5) or 2 X 10(-4) M) did not reverse the specific vasodilating effect of naloxone (3 X 10(-5) M) on norepinephrine-induced constriction. Rather, morphine and naloxone together produced a greater vasodilating effect on norepinephrine-induced constriction than either agent alone. Naloxone (3 X 10(-5) M) failed to alter either phenylephrine-induced constriction or clonidine-induced constriction. The vasodilating effect of naloxone (3 X 10(-5) M) on 10(-3) M norepinephrine-induced constriction was not reduced with 10(-6) M propranolol. These results suggest that the vasodilating effect of naloxone on norepinephrine-induced constriction does not result from an antagonistic action on opiate receptors, direct inhibition of alpha-adrenoreceptors, or direct stimulation of beta-adrenoreceptors in canine cerebral arterial smooth muscle. The vasodilating effect of naloxone on norepinephrine-induced constriction may influence the CBF changes following naloxone administration.

Animals↗
PubMed1984

Antifibrinolytic therapy in the acute period following aneurysmal subarachnoid hemorrhage. Preliminary observations from the Cooperative Aneurysm Study.

Antifibrinolytic therapy remains a controversial issue in the management of subarachnoid hemorrhage (SAH). The relationship of antifibrinolytic therapy with mortality, rebleeding, ischemia, hydrocephalus, and clotting abnormalities was studied in 672 patients in the International Cooperative Study on the Timing of Aneurysm Surgery. The patients with antifibrinolytic therapy had a significantly lower rebleeding rate, but higher rates of ischemic deficits and hydrocephalus. The net result was no difference in mortality in the 1st month following the initial SAH. Further clinical trials are needed to determine the overall effects of antifibrinolytic therapy.

Antifibrinolytic Agents↗
PubMed1984

Effect of laminectomy and anesthesia upon spinal cord blood flow.

Spinal cord blood flow (SCBF) in 10 sheep subjected to laminectomy at L6-7, T6-7, and C7-T1 was compared to that of 10 control sheep subjected to anesthesia alone. Blood flow was measured using the radioactive microsphere technique, with the PaCO2 maintained at 40 +/- 2 mm Hg. Both laminectomy and control animals showed a decrease in SCBF at a rate of 7% to 16%/hr for the 3 hours following the first blood flow determination. When prelaminectomy and postlaminectomy SCBF values were compared to their counterparts in the control animals, there were no significant differences. Laminectomy does not appear to alter SCBF from control values. Spinal evoked potentials (SEP's) were elicited in the laminectomy group by direct cord stimulation at C-7 and L-7. No changes were noted in amplitude or latency of SEP's over time in either caudal or rostral conduction.

Anesthesia, Intravenous↗
PubMed1984

The effects of naloxone on canine splanchnic arterial smooth muscle.

The pharmacological properties of naloxone on vascular smooth muscle in vitro were examined using canine mesenteric arterial segments. Naloxone exerted two different effects on the artery: (A) naloxone at a high concentration (3 X 10(-4) M) produced a nonspecific vasodilation; and (B) naloxone at lower concentrations (3 X 10(-7), 3 X 10(-6), and 3 X 10(-5) M) augmented the vasoconstrictor effects of epinephrine and norepinephrine without altering KCl- or serotonin-induced constriction. Naloxone's augmenting effect on epinephrine-induced constriction was dose dependent. Even when the arterial strips were incubated in low calcium (0.8 mM) or calcium free Kreb's solution, naloxone (3 X 10(-5) M) still augmented epinephrine-induced constriction. With respect to naloxone's effect on another alpha-adrenoreceptor agonist, naloxone (3 X 10(-5) M) failed to alter phenylephrine-induced constriction. Naloxone's augmenting effect on norepinephrine-induced constriction was abolished when the specimens were incubated with 10(-5) M normetanephrine, while naloxone (3 X 10(-5) M) still augmented the constriction even when the specimens were incubated with 10(-5) M cocaine. These results suggest that naloxone at lower concentrations may augment the constrictor responses to catecholamines, at least in part, by inhibiting the extraneuronal uptake of those catecholamines.

Animals↗
PubMed1983

CT and clinical correlations in recent aneurysmal subarachnoid hemorrhage: a preliminary report of the Cooperative Aneurysm Study.

Computed tomography was performed on 1,378 patients admitted within 3 days of subarachnoid hemorrhage (SAH) at 71 centers in a cooperative study. CT on the day of SAH (day 0) was abnormal in 95.8%. Intracranial blood was detected in 95.3% of patients on day 0, 90.5% on the first day after SAH (day 1), and 73.8% on day 3. CT was normal in only 1 of 284 patients in stupor or coma but was normal in 14.6% of 638 alert patients. In the first few days after SAH, CT is highly accurate, often obviating the need of CSF examinations. The interval from SAH until CT and the seriousness of the patient's condition are two factors that influence the results of CT.

Coma↗
PubMed1983

Aneurysmal rebleeding: a preliminary report from the Cooperative Aneurysm Study.

It is generally considered that the peak incidence of rebleeding after aneurysmal subarachnoid hemorrhage is at the end of the 1st or the beginning of the 2nd week after the initial rupture. However, in a series of 2265 patients admitted within 3 days of their first subarachnoid hemorrhage, the peak of rebleeding occurred on the same day as the initial hemorrhage and there was no later peak. These data suggest that new management strategies for minimizing rebleeding must be considered for patients admitted soon after aneurysm rupture.

Antifibrinolytic Agents↗
PubMed1983

Bleeding from cerebral arteriovenous malformations as part of their natural history.

The case records of 191 patients with a cerebral arteriovenous malformation (AVM) were reviewed to determine bleeding characteristics of these lesions. Possible influences of age, sex, the location and size of the AVM, type of initial hemorrhage, and condition of the patients were analyzed. Of these 191 patients, 102 had a single hemorrhage, 32 had a recurrent hemorrhage, and 57 never bled. The follow-up period for patients with an unruptured AVM was a mean of 4.8 years and a maximum of 31 years; for those with a ruptured AVM, the mean was 2 years, and the maximum 37 years. Size of the AVM was significantly related to the risk of first hemorrhage. The average yearly risk for first hemorrhage was between 2% and 3%. Bleeding occurred most frequently in the 11- to 35-year-old age group. The risk of rebleeding increased with advancing age. Among 93 patients followed after their AVM had ruptured, the risk of rebleeding was 6% in 1 year. After the first year, the average rebleeding rate was about 2% per year up to 20 years.

Adolescent↗
PubMed1981

Antifibrinolytic therapy in patients with aneurysmal subarachnoid hemorrhage. A report of the cooperative aneurysm study.

Antifibrinolytic therapy was used in 1,114 patients who had aneurysmal subarachnoid hemorrhage (SAH) and who were treated by the 13 institutions of the Cooperative Aneurysm Study. Patients were started on treatment within one week after SAH was diagnosed, and therapy was discontinued 14 days after the ictus. Rebleeding occurred in 10% of the treated patients. Overall mortality among the treated patients during the two weeks following hemorrhage was 10.7%. Though some minor and a few major side effects occurred, serious complications of therapy were infrequent.

Adolescent↗
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↗