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Biomedical subjects

G E Cold

Publications and source records attributed to G E Cold.

70 records · Page 4Linked to original sources
PubMed1985

Use of a continuous infusion of althesin in neuroanaesthesia. Changes in cerebral blood flow, cerebral metabolism, the EEG and plasma alphaxalone concentration.

Ten patients with small supratentorial tumours were studied during craniotomy. Cerebral blood flow (CBF) was measured in the contralateral hemisphere by a modification of the Kety and Schmidt technique using xenon-133 i.v. With an Althesin infusion rate of 0.2 ml kg-1 h-1, CBF was 24.4 +/- 5.4 ml min-1/100 g and CMRO2 1.87 +/- 0.44 ml min-1/100 g at PaCO2 4.1 +/- 0.7 kPa (mean +/- SD). During constant infusion rates of Althesin, steady values of CMRO2 were obtained, while an increase in infusion rate of 150% was associated with an increase in plasma alphaxalone concentration, a decrease in CMRO2 and a tendency of further EEG suppression. However, great inter- and intraindividual variations were present, and correlations between CMRO2, EEG activity and plasma alphaxalone concentration were weak.

Adult↗
PubMed1985

CBF and CMRO2 during continuous etomidate infusion supplemented with N2O and fentanyl in patients with supratentorial cerebral tumour. A dose-response study.

In 14 patients with supratentorial cerebral tumours with midline shift below 10 mm, CBF and CMRO2 were measured (Kety & Schmidt) during craniotomy. The anaesthesia was continuous etomidate infusion supplemented with nitrous oxide and fentanyl. The patients were divided into two groups. In Group 1 etomidate infusion of 30 micrograms kg-1 min-1 was used throughout the anaesthesia, and CBF and CMRO2 were measured twice. In this group CMRO2 (means +/- s.d.) averaged 2.31 +/- 0.43 ml O2 100 g-1 min-1 70 min after induction and 2.21 +/- 0.38 ml O2 100 g-1 min-1 130 min after induction. In Group 2 the etomidate infusion was increased from 30 to 60 micrograms kg-1 min-1 after the first study and a significant fall in CMRO2 from 2.52 +/- 0.56 to 1.76 +/- 0.40 ml O2 100 g-1 min-1 was found. Simultaneously, a significant fall in CBF was observed. The CO2 reactivity was preserved during anaesthesia.

Adult↗
PubMed1984

Thiopental loading during controlled hypotension for intracranial aneurysm surgery.

In this study we report our clinical experience with supplementary thiopental loading, based on 30 patients undergoing surgery for intracranial aneurysm after a recent episode of subarachnoid haemorrhage. As standard procedure we used pentobarbitone induction, pancuronium relaxation, endotracheal intubation, maintenance with halothane 0.5%, N2O 66% in oxygen, fentanyl, and moderate hypocapnia. A thiopental load of up to 20 mg X kg-1 was supplied while the aneurysm was approached. Satisfactory and well-controlled hypotension was obtained in five cases after thiopental alone, and after thiopental and sodium nitroprusside (SNP) (means +/- s.d.) 1.3 +/- 0.9 microgram X kg-1 X min-1 in the remaining 25 patients. No ECG sign of myocardial ischaemia was observed. One disadvantage was a prolonged recovery period, which in some cases necessitated controlled ventilation for some hours. We conclude that thiopental loading can be used safely as a supplement to neuroanaesthesia for aneurysm surgery.

Adult↗
PubMed1984

Minimum cerebral blood flow and metabolism during craniotomy. Effect of thiopental loading.

Cerebral blood flow and metabolism were measured repeatedly during surgery for cerebral tumours by a modification of the classical Kety & Schmidt method using 133Xe infusion intravenously. Our standard procedure for neuroanaesthesia (pentobarbitone-fentanyl induction, halothane-nitrous oxide maintenance) reduced blood flow from 47.1 to 24.2 ml X 100 g X ml-1 and metabolism from 3.30 to 1.83 ml O2 X 100 g-1 X ml-1. PaCO2 was reduced by hyperventilation from 5.3 to 3.6 kPa. Additional thiopental loading and maintenance using 4 + 4 mg X kg-1 (n = 5) or 8 + 8 mg X kg-1 (n = 5) reduced cerebral metabolism by an additional 15% (P less than 0.01) and blood flow by 16.5% (P less than 0.01), while mean arterial blood pressure fell from 11.0 to 9.9 kPa (P less than 0.05). PaCO2 remained unchanged. This additional reduction in cerebral metabolism and blood flow is small, but we nevertheless conclude that it may well be of clinical interest to the problem of protecting the brain in case of episodes of focal cerebral ischaemia which may arise peroperatively during intracranial surgery.

Adult↗
PubMed1981

Dose response studies in elderly patients subjected to epidural analgesia.

In 51 men, aged 60-87 years, subjected to lumbar epidural analgesia for transurethral resection of the prostate gland, the relationship between doses of 10, 15 and 20 ml mepivacaine 1.5 with adrenaline 1:200,000 and the extension of analgesia was studied. Three different postures during application of epidural analgesia were investigated (left lateral position, sitting position with the patient turned supine immediately after injection, and the sitting position with the patient turned supine 5 min after injection. The results indicate that posture did not significantly influence the extension of analgesia, which was found to be positively correlated to the volume of mepivacaine, and the segmental dose requirement was positively correlated to the volume injected. It is concluded that transurethral resection of the prostate gland in patients over 60 years old can be performed using mepivacaine 1.5% with adrenaline 1:200,000 injected in the lumbar epidural space. In some cases, doses of 15 and 20 ml provoked an unwanted extension of analgesia, reaching the upper thoracic segments.

Aged↗
PubMed1981

Cerebral blood flow in the acute phase after head injury. Part 2: Correlation to intraventricular pressure (IVP), cerebral perfusion pressure (CPP), PaCO2, ventricular fluid lactate, lactate/pyruvate ratio and pH.

In 40 comatose patients with severe head injury, cerebral blood flow (CBF) studies were performed with the 133Xenon washout technique over the most severely injured hemisphere. All patients were mildly sedated with diazepam, chlorpromazine and meperidine and subjected to respiratory support. Simultaneously with the CBF study, intraventricular pressure (IVP), systemic arterial pressure (SAP) and ventricular fluid (VF) lactate, pyruvate and pH were measured. The results indicate a positive correlation between CBF and lactate in patients with a good recovery, irrespective of the time after the trauma, and a positive correlation irrespective of outcome, if the measurements were performed more than 3 days after the trauma. In patients with mainly supratentorial lesions without signs of brain-stem lesions, CBF and CPP were positively correlated, while CBF and ICP were negatively correlated (lost autoregulation). In contradistinction, CBF was positively correlated to ICP and PaCO2 in patients with diffuse brain injury. In some cases of repeated dynamic studies, the clinical course seemed to be related to changes in the measured parameters.

Brain Concussion↗
PubMed1981

Effect of two levels of induced hypocapnia on cerebral autoregulation in the acute phase of head injury coma.

In eight unconscious and artificially ventilated patients with severe head injury, cerebral autoregulation (CA) was tested during angiotensin infusion, before and after a reduction of Paco2. Intracranial pressure (ICP) and systemic arterial pressure (SAP) were continuously recorded. Regional cerebral blood flow (rCBF) was measured by the intracarotid Xe133 washout technique as initial slope index, stochastic and compartmental analysis. In contradistinction to previous human studies, we found a preserved CA during moderate hypocapnia (mean Paco2 34.2 mmHg) while the CA after a further decrease in Paco2 (mean value 23.1 mmHg) was lost. The apparently preserved CA may be a "false phenomenon" due to a regional increase in ICP. After a decrease in Paco2, an association between high CO2 reactivity and rCBF increase during angiotensin was disclosed, while a decreased or unchanged rCBF was observed in regions with inverse steal or abolished CO2 reactivity. The study indicates that the interpretation of CA is facilitated by performing the test during two levels of Paco2, but the presence of impaired autoregulation in the acute phase of head injury indicates that deliberate increase in SAP may be dangerous, as it may provoke an increase of regional ICP and brain oedema.

Adolescent↗
PubMed1980

Cerebral blood flow in the acute phase after head injury. Part 1: Correlation to age of the patients, clinical outcome and localisation of the injured region.

In 40 comatose patients with severe head injury, a total of 114rCBF studies were performed with the intraarterial 133xenon washout technique over the most severely injured hemisphere. All patients were subjected to respirator treatment, and mildly sedated with diazepam, chlorpromazine or meperidine. The average values of the regional flow were corrected for changes in PaCO2 by simultaneous measurements of CO2 reactivity. A PaCO2 value of 30 mmHg (4 kPa) was chosen as the reference value. The results indicate that hyperaemia following head injury is a common phenomenon, especially in young victims with supratentorial cortical lesions. The hyperaemic phase can last from some days to several weeks and is of no prognostic significance. In elderly patients with supratentorial cortical lesions, and in patients with mainly brain-stem lesions or diffuse brain lesions a persistent low flow state was observed in the acute phase (first 1-3 days after the injury). This low flow state was also observed 1-2 weeks after the injury if loss of consciousness persisted, but it was of no prognostic significance, as CBF values between 15 and 20 ml/100 g/min were associated with a good recovery.

Adolescent↗
PubMed1979

Serum bromide after general anaesthesia with halothane.

Serum bromide was determined in 30 patients during the first few postoperative days after general anaesthesia with halothane. The material comprised a group of younger patients (19-50 years) and a group of elderly patients (greater than 70 years), neither of whom received thiomebumal induction, and a group of younger patients (19-50 years) who received thiomebumal induction. The changes in serum bromide were independent of age and induction with barbiturate, and a maximum rise in serum bromide was found most often 2-3 days after the anaesthesia. All groups showed a rise in serum bromide to therapeutically sedative concentrations, and a significant correlation was found between MAC-hours halothane exposure and serum bromide.

Adult↗
PubMed1978

Cerebral metabolic rate of oxygen (CMRO2) in the acute phase of brain injury.

In 22 comatose patients with acute brain injury, the cerebral metabolic rate of oxygen (CMRO2) was calculated as the product of the hemispheric cerebral blood flow (CBF) and the arteriovenous oxygen content difference. All patients were subjected to moderate sedation without barbiturates, normothermia and respiratory treatment. The CBF was calculated by the 133xenon washout method as the average of 16 regions. The results indicate high jugular venous oxygen tension and, in some studies, very low oxygen consumption. A critical, low CMRO2 was not found, and values of about 0.4 ml/100 g/min were compatible with restitution of intellectual function. The CMRO2 was unrelated to the clinical outcome and to the time after the trauma. In bilateral studies, the lowest values were measured in the most severely injured hemisphere.

Adolescent↗
PubMed1978

Cerebral autoregulation in unconscious patients with brain injury.

In 18 unconscious patients with traumatic brain injury, the cerebral autoregulation was tested during the first 2-3 weeks after the acute trauma. Regional cerebral blood flow (rCBF) was measured by the intra-arterial 133xenon washout method before and after an increase of about 20% in the mean arterial blood pressure (MABP) by angiotensin. The difference between MABP and intraventricular pressure (IVP) was used as cerebral perfusion pressure (PP). Simultaneously, ventricular fluid pH, lactate and pyruvate were measured. Regional loss of autoregulation indicated by a 20% flow increase was observed in 29 out of 35 studies (83%), while hemispheric loss of autoregulation was observed in only one study. The results of the autoregulation tests were unrelated to the clinical outcome, the presence of brain-stem lesion, and the ventricular fluid pH, lactate and lactate/pyruvate ratio. In repeated studies, a gradual normalization of the autoregulation was observed about 5 days after the acute trauma.

Adolescent↗
PubMed1977

The cerebrovascular CO2 reactivity during the acute phase of brain injury.

Using the intra-arterial 133xenon (133Xe) method, the cerebrovascular response to acute Paco2 reduction was studied in 26 unconscious, brain-injured patients subjected to controlled ventilation. The CO2 reactivity was calculated as delta in CBF/delta Paco2. The perfusion pressure was defined as the difference between mean arterial pressure and mean intraventricular pressure. Although the CO2 reactivities did not differ significantly from that in awake, normocapnic subjects, it was low in the acute phase of injury, especially in those patients with severe outcome in whom the brain-stem reflexes were often affected. An increase of the CO2 reactivity with time was observed, indicating normal response after 1-2 weeks. Chronic hypocapnia in six unconscious patients resulted in sustained CSF pH adaptation. The question whether a delay in CSF pH adapation exerts an influence on the CO2 reactivity, and the influence of cerebral lactacidosis on the CO2 response are discussed.

Adolescent↗
PubMed1977

The effects of PaCO2 reduction on regional cerebral blood flow in the acute phase of brain injury.

In 26 unconscious patients with brain injuries, regional cerebral blood flow (rCBF) was measured with a 16-channel Cerebrograph before and after acute reduction of PaCO2. The intra-arterial 133xenon washout technique was used, and CBF was calculated regionally as initial slope index or stochastic flow. The CO2 reactivity was calculated as deltaln CBV/deltaPaCO2. In supratentorial cortical lesions, an acute fall in PaCO2 increased the homogeneity of the regional flow pattern (decrease in the standard deviation of the regional flow values), and reduced the number of focal hyperaemic regions (tissue peaks). The CO2 reactivity in tissue peak regions was generally higher than in regions without tissue peaks. In severely injured patients with a poor outcome (dementia, vegetative survival or death), inverse steal reaction was accounted for in 11% of all regions, but only in 3% of the regions in patients who survived without dementia. Inverse steal reaction was most frequently seen during the first 3 days after the trauma. In repeated CBF studies, an increase in the CO2 reactivity with time was observed after the acute trauma. In comparison with the CO2 reactivity found in normocapnic awake subjects, this increase was higher than expected in several cases.

Adolescent↗
PubMedDate not supplied

Glucose uptake and lumped constant variability in normal human hearts determined with [18F]fluorodeoxyglucose.

BACKGROUND: Myocardial glucose uptake can be measured with [18F]fluoro-2-deoxyglucose (FDG) and positron emission tomography (PET). However, changes of myocardial metabolism may alter the ratio between the net rates of FDG and glucose uptake, known as the lumped constant. We tested the hypothesis that the variability of the lumped constant determined in animals explains the disagreement between human net myocardial glucose uptake calculated from aortocoronary sinus deficits and measured with PET. METHODS AND RESULTS: In the three-compartment model of glucose transfer into cells, the lumped constant is a function of the relationship between the net and the unidirectional rates of uptake of glucose and glucose tracers such as FDG. Using this principle, validated in the human brain and the animal heart under experimental conditions, we estimated the lumped constant of the human heart by PET in 10 healthy men under several metabolic conditions established by altering the circulating insulin level during a euglycemic clamp and with somatostatin and heparin infusions. The lumped constant varied systematically between 0.44 and 1.35. At insulin levels below 100 pmol/L, free fatty acids were inversely related to serum insulin levels and the lumped constant increased linearly with serum insulin concentration. At insulin levels above 100 pmol/L, free fatty acids were suppressed and the lumped constant varied in inverse proportion to the insulin level. When the lumped constant was estimated in this manner, net myocardial glucose uptake agreed with that determined in previous measurements of blood flow and aortocoronary sinus deficit. CONCLUSION: In the intact human organism, the cardiac lumped constant varies with the metabolic condition, as predicted from studies of the brain and animal heart under experimental conditions.

Adult↗