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Biomedical subjects

J J Caronna

Publications and source records attributed to J J Caronna.

13 recordsLinked to original sources
PubMed1979

Upward transtentorial herniation: seven cases and a literature review.

Seven cases of upward transtentorial herniation occurred. In each patient, coma with reactive, miotic pupils, asymmetrical or absent caloric responses, and decerebrate posture indicated brain-stem compression. In this setting, the development of unequal, then midposition, fixed pupils signaled midbrain failure from upward herniation. Vertebral angiography showed upward displacement of the superior cerebellar arteries. Results of autopsy confirmed the existence of grooving of the vermis by the tentorial margins and, in one case, of anterior displacement and distortion of the midbrain. In five of 45 reported cases of upward herniation, the conditions were diagnosed antemortem. Instances of cerebellar hematoma and tumor predominated. In at least seven patients, performance of ventriculography may have precipitated herniation. Clinical details were provided in only nine patients and did not separate upward herniation from brain-stem compression. Cerebellar ischemic infarct found in one of our patients is a rarely reported cause of upward herniation.

Adult↗
PubMed1978

Cerebral hemodynamics and metabolism in pseudotumor cerebri.

A comprehensive analysis of cerebral hemodynamics and metabolism was carried out in 14 patients with pseudotumor cerebri. Tracer techniques were employed to measure cerebral blood flow (CBF) and vascular reactivity to acute changes in arterial carbon dioxide tension and blood pressure, cerebral blood volume (CBV), and the cerebral metabolic rate for oxygen and glucose. There was a small reduction (p less than 0.01) in CBF (44 +/- 7 ml/100 gm/min; normal, 54 +/- 9) with normal vascular reactivity; an increase (p less than 0.005) in CBV (4.8 +/- 0.8 ml/100 gm; normal, 3.6 +/- 0.5), and normal cerebral metabolism. We conclude that an abnormality of the cerebral microvasculature is responsible for an elevation in CBV, but the intracranial hypertension can be explained only by tissue swelling due to an increase in water content. The relationship between the vascular abnormality and the tissue swelling remains to be defined.

Adolescent↗
PubMed1978

Duration of apnea needed to confirm brain death.

To determine the duration of respiratory arrest needed to attain a PaCO2 level high enough to provide maximal stimulation of respiration, we evaluated changes in PaCO2, PaO2 and apH during periods of apnea lasting as long as 10 minutes in 10 apparently brain-dead subjects. Before apnea, mean PaCO2 was 33 mm Hg. In seven subjects who did not breathe for 10 minutes, the mean rate of rise of PaCO2 was 3.2 mm Hg per minute. PaCO2 at 4 minutes was 50 mm Hg and at 10 minutes was 67 mm Hg. Three subjects breathed, two after less than 2 minutes of apnea, when PaCO2 was 47 and 54 mm Hg, and one after 4.5 minutes, when PaCO2 was 47 mm Hg. These data indicate: (1) that the threshold for respiratory stimulation may approach a PaCO2 of 60 mm Hg in patients with brain damage; (2) that the rate of increase in PaCO2 is such that, even in a normocapnic subject after 3 minutes of apnea, the PaCO2 may not be sufficiently high to stimulate respiration; and (3) if a patient is hypocapnic prior to the onset of apnea, PaCO2 may not reach 60 mm Hg even after 15 minutes. To confirm absolute apnea, then, blood gas monitoring is necessary for verification of normocapnia prior to the beginning of apnea. In the absence of blood gas determinations, no fixed period of apnea, sufficient in all cases to establish absolute apnea, can be ascertained.

Adult↗
PubMed1977

A prospective study of nontraumatic coma: methods and results in 310 patients.

Neurological signs and outcome are compared in the first 310 patients from a continuing prospective study of coma not caused by trauma or drugs. Sixteen percent of the patients achieved an independent existence within a month; severe disability or the vegetative state developed in 25% of patients comatose for six hours and in 79% of those still in coma after a week. The chance of regaining an independent existence was greater in patients who, by one day, obeyed commands or moved the limbs appropriately in response to noxious stimuli or who had attained any of the following: orienting eye movements, normal responses to oculocephalic or oculovestibular stimulation, or normal muscle tone. Conversely, the chance of regaining an independent existence fell in patients who, after one day, had either extensor responses of the limbs or failed to move them in response to noxious stimuli or who lacked eye opening, pupillary reactions, corneal responses, or any eye movement in response to oculovestibular or oculocephalic stimulation. Beyond these general guidelines, numbers of patients with particular signs are presently too small for confident prediction of outcome.

Adolescent↗
PubMed1977

Cerebral blood flow and oxygen consumption in rat, measured with microspheres or xenon.

The cerebral blood flow and, in some rats, the cerebral rate of oxygen consumption were measured in three groups of male rats. Fractionation of radioisotope-labeled microspheres was used to measure regional cerebral blood flow in four parts of the rat brain. The arterial and cerebral venous concentrations of radioactive xenon during desaturation were used to measure the blood flow and oxygen consumption of cortex when venous blood was collected from the superior sagittal sinus, or of whole brain when the transverse sinus was sampled. The regional cerebral flow measured with microspheres had a large standard error reflecting the technical difficulty of this method. The cerebral blood flow measured with xenon was higher when venous blood was sampled from the superior sagittal sinus than when sampled from the transverse sinus, but cerebral oxygen consumption rates were similar. The difference reflects the greater trauma involved in the superior sagittal approach and possible extracerebral contamination present in the transverse sinus approach.

Animals↗
PubMed1976

Atherosclerotic cerebral infarction: pathophysiologic aspects.

When the supply of substrate to the brain is threatened, homeostatic mechanisms induce cerebral vasodilatation to compensate for the insufficiency. When a region of the brain is rendered completely ischemic, local infarction occurs. The size of the infarct depends partly on the availability of collateral circulation and the adequacy of the homeostatic mechanisms controlling blood flow in stillpatent vessels. Several approaches to acute-phase treatment of stroke derive from clinical and experimental studies of cerebral blood flow and metabolism. We must conclude that both surgical and nonsurgical therapeutic measures have been of limited value in the treatment of cerebral infarction and that the basic therapy for completed stroke remains good medical management of complications and attentive nursing care.

Blood Flow Velocity↗
PubMed1975

Can one predict outcome of medical coma?

The combined evaluation of the motor response to stimulation and the oculovestibular (OV) reflex gives useful indicants to the outcome of medical coma. We examined 48 patients during the first 12 h and at 24 h after the onset of medical coma. We excluded patients who had ingested drugs or who had hypothermia. Motor responses to a noxious stimulus were scored on a 6 'best' and 1 'worst' scale, and the presence or absence of oculovestibular responses to icewater irrigations was recorded. Subjects were divided by outcome at three months into three groups: death or persistent vegetative state, severe disability, and moderate disability or good recovery. On the basis of the present series it was often possible to distinguish among the outcomes at or before 24 h. The patient's age and the presence or absence of pupillary responses, spontaneous eye movements and oculocephalic responses were not predictive of outcome, nor were the respiratory pattern, blood gases, blood pressure, heart rate and temperature. A minimal motor score and an absence of oculovestibular responses at 12 h always were assoicated with death. With higher motor scores, the absence of oculovestibular responses at either 12 or 24 h implied an outcome no better than severe disability. The results of the present study imply that early bedside assessments can yield accurate predictive information in medical coma.

Cerebrovascular Disorders↗
PubMed1975

Whole-brain blood flow and oxygen metabolism in the rat during nitrous oxide anesthesia.

The Kety-Schmidt washout technique has been modified to measure whole-brain blood flow and metabolism in the rat. During nitrous oxide anesthesia, 14 rats exhaled (133)Xe, and continuous and simultaneous arterial and cerebral venous samples were drawn from a femoral artery and the transverse sinus of the brain. Extracerebral contamination of the venous sample was minimal, and equilibration of (133)Xe in brain tissue and blood was obtained after 10-24 min of inhalation. Cerebral blood flow was calculated from the total activity of the mechanically integrated arterial and venous samples according to the principle of Scheinberg and Stead. At a mean Paco2 of 40 mmHg, CBF averaged 98 +/- 6 (SEM) ml/100 g-min and CMRO2 averaged 5.4 +/- 0.7 (SEM) ml/100 g-min. CBF changed 2.4% with each millimeter Hg change of Paco2 while CMRO2 changed only insignificantly. The values obtained for CBF are higher than reported for man and large laboratory animals bur reflect the proportionately greater amount of gray matter in the rat brain.

Anesthesia, Inhalation↗