PubMed Health⌕ Search

Biomedical subjects

K Messeter

Publications and source records attributed to K Messeter.

At least 37 records · Page 2Linked to original sources
PubMed1992

Modulation by carbon dioxide and pH of the contractile responses to potassium and prostaglandin F2 alpha in isolated human pial arteries.

Variation of PCO2 with concomitant changes in extracellular pH (pHo) may modulate cerebrovascular resistance, but the direct actions of carbon dioxide and pHo on human cerebral arteries are unknown. In this study, we have evaluated the effects of different carbon dioxide tensions (2.7, 4.2 and 7.2 kPa) with either fixed (pHo = 7.44) or concomitant changes in pHo, on contractions induced by depolarization (potassium) or receptor stimulation (prostaglandin F2 alpha) in isolated human pial arteries. Isolated changes in PCO2 had no significant effect on either potency (unchanged EC50 value) or the maximum response (Emax) in potassium-contracted arteries. Hypercapnia with uncompensated pHo significantly decreased both EC50 and Emax values, whereas uncompensated hypocapnia significantly increased the EC50 value without any effect on Emax. Concentration-response curves induced by prostaglandin (PG) F2 alpha were shifted significantly to the right (increased EC50 = decreased potency) during both hypo- and hypercapnia, independent of changes in pHo. The maximal responses were enhanced significantly during hypocapnia (Emax = 110 (SEM 2)%), but this enhancement was converted into a slight attenuation when pHo was compensated (Emax = 92 (4)%). Hypercapnia, with or without compensation of pHo, decreased the Emax values to 69 (16)% and 73 (9)%, respectively. We conclude that hypocapnia increases contractility in human pial arteries--an effect which is reversed by compensation of pHo. In contrast, the hypercapnic decrease of PGF2 alpha-induced contractions appears to be independent of pHo. The results confirm a relationship between contractility and pHo, but do not exclude a direct action of carbon dioxide in receptor-stimulated arteries.

Adult↗
PubMed1992

Human brain temperature during anesthesia for intracranial operations.

The intraventricular and rectal temperatures were registered in nine patients subjected to major surgery of the brain. Copper-constantan thermocouples were introduced into the lumen of an intraventricular catheter also used for perioperative monitoring of intracranial pressure. During anesthesia, the intraventricular temperature was higher than rectal temperature, the mean difference being 0.30 +/- 0.24 degrees C. No significant changes in intraventricular temperature were seen during different stages of the operations. It is concluded that during routine anesthesia rectal temperature can be relied on for a reasonable estimation of human brain temperature. It should be observed, however, that in the postoperative period, both rectal and intraventricular temperature rose considerably. In three patients, the intraventricular temperature rose as much as 2.5-4 degrees C, thus increasing the temperature gradient between rectum and brain. The relevance of these findings are discussed.

Journal Article↗
PubMed1992

Effects of nitrous oxide on cerebral haemodynamics and metabolism during isoflurane anaesthesia in man.

Seven normoventilated and five hyperventilated healthy adults undergoing cholecystectomy and anaesthetized with methohexitone, fentanyl and pancuronium were studied with measurement of cerebral blood flow (CBF), cerebral metabolic rate of oxygen (CMRO2), and quantified electroencephalography (EEG) under two sets of conditions: 1) 1.7% end-tidal concentration of isoflurane in air/oxygen; 2) 0.85% end-tidal concentration of isoflurane in nitrous oxide (N2O)/oxygen. The object was to study the effects of N2O during isoflurane anaesthesia on cerebral circulation, metabolism and neuroelectric activity. N2O in the anaesthetic gas mixture caused a 43% (P less than 0.05) increase in CBF during normocarbic conditions but no significant change during hypocapnia. CMRO2 was not significantly altered by N2O. EEG demonstrated an activated pattern with decreased low frequency activity and increased high frequency activity. The results confirm that N2O is a potent cerebral vasodilator in man, although the mechanisms underlying the effects on CBF are still unclear.

Adult↗
PubMed1992

Complications and side effects during thiopentone therapy in patients with severe head injuries.

This study reports all complications and side effects occurring in 38 patients with severe traumatic brain lesions treated with barbiturate coma because of a dangerous increase in intracranial pressure. The treatment was induced by intravenous infusion of thiopentone (5-11 mg.kg-1) followed by a continuous infusion of 4-8 mg.kg-1.h-1. The subsequent rate of thiopentone infusion was governed by the level of the intracranial pressure with the intention of keeping ICP below 20 mmHg (2.7 kPa). The duration of treatment was 1-15 days. Arterial hypotension occurred in 58%, hypokalemia in 82%, respiratory complications in 76%, infections in 55%, hepatic dysfunction in 87% and renal dysfunction in 47% of the patients. Twenty patients survived. Mortality in 17 patients was caused by an untreatable increase in intracranial pressure. In one patient complications due to barbiturate treatment may have contributed to the fatal outcome. In none of the other cases were the noted complications and side effects associated with any permanent symptoms or dysfunctions.

Adolescent↗
PubMed1992

A porcine model for sequential assessments of cerebral haemodynamics and metabolism.

We present a physiologically stable porcine model designed for sequential assessments of pharmacological effects on mean hemispheric cerebral blood flow (CBF) and cerebral metabolic rate for oxygen (CMRO2) at sustained normocapnia. The dynamic influence of continuously administered fentanyl (0.040 mg.kg-1.h-1 i.v.), nitrous oxide (70%) and pancuronium (0.30 mg.kg-1.h-1 i.v.) on these variables was studied in eight normoventilated pigs. CBF was reliably assessable at 10-min intervals by clearance of intra-arterially injected 133Xe, monitored by an extracranial scintillation detector. CMRO2 was calculated from CBF and the simultaneously measured cerebral arteriovenous difference in blood oxygen content. The intracerebral distribution of a contrast medium injected into the external and internal carotid arteries was studied by angiography, and the cerebral venous outflow was investigated by measurements of the distribution of an intra-arterially administered non-diffusible tracer, [99mTc]pertechnetate, to the internal and external jugular veins. After a 3-h equilibration period, CBF and CMRO2 were determined on six occasions over a study period lasting 1 h 40 min. The mean ranges of these variables were 56-60 and 1.9-2.0 ml.100 g-1.min-1, respectively. We conclude that the model enables repeated assessments of CBF and CMRO2 under stable physiological background conditions and thus valid cerebral pharmacodynamic investigations of drugs given for anaesthesia.

Animals↗
PubMed1991

Cardiopulmonary perfusion and cerebral blood flow in bilateral carotid artery disease.

The fear of cerebral complications after cardiopulmonary bypass in patients with heart disease and severe carotid artery disease has led many authors to suggest combined approaches in these patients. The pathogenetic mechanism for stroke is based partly on the stenotic narrowing of the carotid artery. A diameter reduction of 75% is frequently considered hemodynamically significant and indicative of an increased risk for neurological morbidity. We studied the cerebral blood flow in 7 patients undergoing coronary artery bypass grafting who also had severe bilateral carotid disease. The results were compared with the results in 17 patients without carotid disease who had bypass grafting. The cerebral blood flow was measured by xenon 133 washout technique before, during, and after cardiopulmonary bypass with moderate hypothermia. Acid-base regulation was according to the alpha-stat theory, and blood pressure was kept greater than 50 mm Hg. The cerebral blood flow levels (mL.100g-1.min-1) before, during, and after cardiopulmonary bypass in the study group (30 +/- 11, 31 +/- 8, 47 +/- 20) (mean +/- standard deviation) were almost identical to those in the control group (30 +/- 11, 28 +/- 8, 47 +/- 12). The cerebral blood flow levels for the left and right hemispheres in the group with carotid disease were comparable and within normal ranges. In 2 patients, slight differences were noted between hemispheres, and this finding may indicate an increased risk for ischemia. These patients, however, did not show any signs of postoperative deficit. The flow limitations of critical carotid stenoses do not seem to imply a risk for cerebral hypoperfusion if cardiopulmonary perfusion is performed in a controlled manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Arterial Occlusive Diseases↗
PubMed1991

Cerebral vasoreactivity and the prediction of outcome in severe traumatic brain lesions.

Mean hemispheric blood flow (CBF) was studied in 38 comatose, severely brain-injured patients following intravenous administration of xenon-133. Repeated measurements were performed in order to evaluate cerebral vasoreactivity following a decrease in PaCO2. Simultaneously, arterial-venous oxygen differences (AVDO2) and intracranial pressure (ICP) were measured. An impaired CBF response to hyperventilation (delta CBF/delta PaCO2 less than 1.0) was obtained in 22 patients. Three of 16 patients with preserved CO2-reactivity died because of their brain injuries and 12 patients reached good recovery/moderate disability. In the group of patients with impaired vasoreactivity 11 of 22 patients died and only three patients reached good recovery/moderate disability. The study documents that in patients with severe traumatic brain lesions measurements of cerebral vasoreactivity to hyperventilation give prognostic information that is not obtained by clinical observations or CT-scanning.

Blood Flow Velocity↗
PubMed1991

Simultaneous transcranial Doppler sonography and cerebral blood flow measurements of cerebrovascular CO2-reactivity in patients with aneurysmal subarachnoid haemorrhage.

Transcranial Doppler sonography (TCD) flow velocities and cerebral blood flow (CBF) measurements were evaluated in 14 patients who had suffered a major aneurysmal subarachnoid hemorrhage (SAH). Cerebrovascular reactivity to hypocapnia was evaluated simultaneously by the two methods. The measurements were performed under general anaesthesia preoperatively, within 72 hours after the bleed, during normocapnia and hypocapnia. There was poor correlation between absolute values of hemispheric CBF and corresponding TCD mean flow velocity. Controlled hyperventilation was associated with a significant decrease in CBF as well as TCD flow velocity (p less than 0.001). In terms of reactivity indices the correlation between the two methods was poor and not significant (r = 0.33, p = 0.09). The principal differences between the methods are discussed as well as the application of TCD in the evaluation of cerebrovascular reactivity.

Adult↗
PubMed1989

Cerebral vasoreactivity to carbon dioxide during cardiopulmonary perfusion at normothermia and hypothermia.

With the pH-stat acid-base regulation strategy during hypothermic cardiopulmonary bypass (CPB), carbon dioxide (CO2) is generally administered to maintain the partial pressure of arterial CO2 at a higher level than with the alpha-stat method. With preserved CO2 vasoreactivity during CPB, this induction of "respiratory acidosis" can lead to a much higher cerebral blood flow level than is motivated metabolically. To evaluate CO2 vasoreactivity, cerebral blood flow was measured using a xenon 133 washout technique before, during, and after CPB at different CO2 levels in patients who were undergoing coronary artery bypass grafting with perfusion at either hypothermia or normothermia. The overall CO2 reactivity was 1.2 mL/100 g/min/mm Hg. There was no difference between the groups. The CO2 reactivity was not affected by temperature or CPB. The induced hemodilution resulted in higher cerebral blood flow levels during CPB, although this was counteracted by the temperature-dependent decrease in the hypothermia group. After CPB, a transient increase in cerebral blood flow was noted in the hypothermia group, the reason for which remains unclear. The study shows that manipulation of the CO2 level at different temperatures results in similar changes in cerebral blood flow irrespective of the estimated metabolic demand. This finding further elucidates the question of whether alpha-stat or pH-stat is the most physiological way to regulate the acid-base balance during hypothermic CPB.

Acid-Base Equilibrium↗
PubMed1988

Cerebral blood flow and oxygen consumption during isoflurane and halothane anesthesia in man.

In 13 patients, the effects on cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO2) of isoflurane and halothane administered in a clinically relevant situation were studied. Measurements were performed during fentanyl/nitrous oxide (65%) anesthesia together with moderate hyperventilation (PaCO2 approx 4.5 kPa), and repeated after addition of 0.65 MAC of isoflurane (n = 6) or halothane (n = 7). CBF was measured after intravenous administration of 133xenon and CMRO2 was calculated from the arterial venous differences of oxygen content (AVDO2) determined in arterial and jugular venous bulb blood. CBF and CMRO2 (means +/- s.e. mean) determined prior to administration of volatile agents were 28 +/- 5 ml x 100(-1) x min-1 and 2.0 +/- 0.3 ml x 100 g-1 x min-1, respectively, in the isoflurane group. In the halothane group, CBF was 25 +/- 0.4 ml x 100 g-1 x min-1 and CMRO2 was 2.0 +/- 0.4 ml x 100 g-1 x ml-1. There were no significant intergroup differences. Isoflurane did not change CBF, whereas halothane produced an increase of 36% (P less than 0.05) compared to values obtained during fentanyl/N2O anesthesia. In addition, isoflurane caused a further decrease in CMRO2 of 12% (P less than 0.01) as compared to a 20% increase (P less than 0.05) with halothane. The cerebral metabolic depression caused by the short-acting anesthetic induction agents would be expected to decrease with time, and could partly explain the observed increase in CMRO2 produced by halothane. The study suggests that the cerebrovascular and metabolic properties of isoflurane differ from those of halothane, also in man.

Adult↗
PubMed1988

Cerebral blood flow, vasoreactivity, and oxygen consumption during barbiturate therapy in severe traumatic brain lesions.

Mean hemispheric cerebral blood flow (CBF) and intracranial pressure (ICP) were measured in 19 severely head-injured patients treated with barbiturate coma. The CBF was calculated from the clearance of tracer substance monitored by extracranial scintillation detectors after intravenous administration of xenon-133. In 11 of the patients cerebral arteriovenous oxygen differences were measured simultaneously. In all patients the effects of pronounced hyperventilation were recorded prior to initiation of barbiturate treatment. A normal CBF response to hyperventilation (delta CBF/delta PaCO2 greater than or equal to 1) was obtained in eight patients. In these patients induction of barbiturate coma was accompanied by physiological decreases in CBF and in the calculated cerebral metabolic rate of oxygen (CMRO2); they also exhibited a rapid and lasting decrease in ICP. A decreased or an abolished CO2 reactivity was recorded (delta CBF/delta PaCO2 less than 1) in 11 patients. In 10 of these 11 patients the physiological decreases in CBF and CMRO2 were not obtained during barbiturate treatment and the decrease in ICP was transitory. This study demonstrates a correlation between cerebral vasoreactivity, physiological effects of barbiturate therapy, and clinical outcome.

Adolescent↗
PubMed1987

Cerebral blood flow and autoregulation during hypothermic cardiopulmonary bypass.

Mean hemispheric cerebral blood flow (CBF) was studied following intravenous or intraarterial administration of xenon-133, in 10 men admitted for coronary artery bypass grafting. Repeated CBF measurements were performed to evaluate autoregulation before, during, and after cardiopulmonary bypass (CPB). During CPB mean CBF remained unchanged compared with the pre-CPB level, without evidence of cerebral hyperemia or impairment of autoregulation. A marked increase in CBF occurred after CPB and was followed by a time-dependent reduction toward the pre-CPB level. The data support the alpha-stat regulation theory but cannot explain the cerebral vasodilation observed after CPB.

Adult↗
PubMed1987

Prediction and prevention of delayed ischemic dysfunction after aneurysmal subarachnoid hemorrhage and early operation.

Mean hemispheric cerebral blood flow (CBF) was studied after the intravenous administration of xenon-133 in 20 anesthetized patients with aneurysmal subarachnoid hemorrhage. Before early aneurysm operation, repeated CBF measurements were made to evaluate the cerebral vascular reactivity to controlled hyperventilation. Thirteen individuals received intravenous treatment with the calcium channel blocker nimodipine, whereas the other seven patients did not receive such specific antiischemic treatment. Five of the latter patients had an impaired CO2 response, and three showed delayed ischemic deterioration (DID), whereas none of the seven nimodipine-treated patients with impaired CO2 response showed DID. One nimodipine-treated patient with a preserved CO2 response, in whom operation was complicated, developed DID. The observed findings indicate that DID after uncomplicated early aneurysm operation may be associated with an early disturbance of cerebral vasoreactivity. Treatment with nimodipine may counteract the development of DID in patients with an impaired CBF CO2 response.

Adult↗
PubMed1987

A comparison of intraparenchymatous and intraventricular pressure recording in clinical practice.

A comparison of intraventricular pressure (IVP) and intraparenchymatous pressure was performed in 11 patients with severe traumatic brain lesions. Intraparenchymatous pressure was measured with a Honeywell microtransducer placed intracerebrally. Before the microtransducer was used in clinical practice, basic data on drift and temperature sensitivity were tested in experiments in vitro. Under clinical conditions the correspondence between the measured IVP and intraparenchymatous pressures appeared to be better than previously reported for different devices for epidural or subdural pressure recording. It is concluded that intraparenchymatous pressure monitoring is reliable in clinical practice and that such measurements are valuable in patients with compressed and/or distorted ventricles that preclude possibilities for IVP recording.

Brain Injuries↗
PubMed1986

Delayed ischemic deterioration in patients with early aneurysm operation and intravenous nimodipine.

A consecutive series of 100 individuals with aneurysmal subarachnoid hemorrhage were subjected to early aneurysm operation followed by subsequent intravenous administration of the calcium antagonist nimodipine during the critical period for symptomatic vasospasm. A total of 85 patients were in Hunt and Hess neurological Grades I through III, and 15 were in Grade IV or V before operation. In 39 individuals the aneurysm was located in the anterior cerebral artery complex (ACA), in 29 it originated from the internal carotid artery complex (ICA), and in 32 individuals the ruptured aneurysm arose from the middle cerebral artery (MCA). Of the patients, 71% made a good neurological recovery; the morbidity was 22%, and the mortality was 7%. Of the Grade I-III patients, 79% made a good neurological recovery, and the mortality was 6%. Delayed ischemic cerebral deterioration with permanent dysfunction occurred in five patients, all with ruptured ACA aneurysms. No single patient in the ICA or MCA populations developed delayed ischemic deterioration with fixed neurological deficit despite the presence of several potential risk factors, especially among the MCA aneurysm patients.

Brain Ischemia↗
PubMed1986

Cerebral hemodynamics in patients with acute severe head trauma.

Mean hemispheric cerebral blood flow (CBF) was studied in 11 comatose brain-injured patients following intravenous administration of xenon-133. Repeated measurements were performed in order to evaluate cerebral vasoreactivity following a decrease in PaCO2. In addition, the effect of induced barbiturate coma was evaluated in patients with intracranial hypertension. The cerebral vasoreactivity and the CBF response following induction of barbiturate coma varied. In patients with normal CO2 reactivity, barbiturate treatment was accompanied by a considerable decrease in CBF as compared to patients with decreased or abolished CO2 response. During barbiturate treatment the intracranial pressure (ICP) became normal in three of four patients with preserved CO2 response, but reached normal levels in only one of five patients with impaired CO2 reactivity. Patients whose ICP became normal recovered. The data suggest a positive correlation between CO2 reactivity and the effect of barbiturate treatment. Furthermore, preserved cerebral vasoreactivity after severe head injury may be of prognostic value.

Adolescent↗
PubMed1981

Treatment of stress response to laryngoscopy and intubation with fentanyl.

The cardiovascular response to laryngoscopy and intubation was investigated in lightly anaesthetised patients admitted to hospital for elective intracranial surgery. One group of patients was given fentanyl 5 microgram/kg body weight before induction with thiopentone and suxamethonium. The other group served as controls. Fentanyl treatment caused a significant attenuation of the blood pressure and pulse response to laryngoscopy and intubation. Different techniques for induction of anaesthesia are discussed in relation to the demands of neuroanaesthesia.

Adult↗