Measured and predicted values of oxygen consumption during isoflurane anesthesia in man.
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Biomedical subjects
Publications and source records attributed to F Giunta.
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AIM: To evaluate the effect of noradrenaline infusion in a case of hyperdynamic septic shock refractory to volume loading, dopamine and dobutamine, on hemodynamic parameters, oxygen transport, lactate and pyruvate levels. DESIGN: Description of a clinical case. SETTING: Postsurgical Intensive Care Unit in a University Hospital. PATIENT: A 48-year-old woman with symptoms of peritonitis due to Enterobacter Agglomerans and refractory hyperdynamic septic shock. INTERVENTIONS: Administration of noradrenaline in doses ranging from 0.03 to 0.14 micrograms/kg/min. MEASUREMENTS AND RESULTS: Before and after noradrenaline infusion the following were evaluated: hemodynamic (parameters) and oxygen transport acid-base status, arterial blood levels of lactate and pyruvate, and lactate/pyruvate ratio. During the administration of noradrenaline an increase was observed over time in oxygen consumption (from 110 +/- 16 to 164 +/- 19 mL/min/m2; p < 0.01), peripheral vascular resistance (from 509 +/- 95 to 1172 +/- 384 dynes.sec.cm-5, p < 0.01) and the oxygen extraction index (from 12.9 +/- 2.1 to 21.2 +/- 2.9%, p < 0.01), together with reduced lactate (from 24.4 +/- 1.5 to 4.9 +/- 5.1 mmol/L) and pyruvate levels (from 945 +/- 62 to 357 +/- 174 mumol/L; p < 0.01) and a reduced lactate/pyruvate ratio (from 26.2 +/- 1.2 to 11.8 +/- 5.9, p < 0.01). No significant increases were found in cardiac output and oxygen delivery. CONCLUSIONS: In the case observed here the infusion of noradrenaline induced an increase in oxygen consumption and the oxygen extraction index associated with a reduction in the lactate/pyruvate ratio and the normalisation of the acid-base status. These changes were not associated with an increase in oxygen which remained delivery > or = 600 mL/min/m2.
This paper reviews the present state and future perspectives of the peri-operative application of Transoesophageal Echocardiography (TEE) for early detection of myocardial ischaemia during general surgery. The increasing clinical relevance of this problem parallels the progressively higher frequency of surgery performed in patients at relatively high cardiovascular risk, due to a longer life-span and improved anaesthetic techniques. TEE potentially provides a powerful method for detailed cardiac monitoring in patients undergoing general surgery. The detection of a new regional asynergy during echocardiographic monitoring represents an early and reliable marker of myocardial ischaemia. The sensitivity, specificity and feasibility of TEE monitoring of intraoperative myocardial function and ischaemia will be outlined and compared with those of ECG and invasive monitoring. Problems related to the interpretation of intra-operative findings, with special reference to possible non-ischaemic mechanisms responsible for intra-operative regional asynergies--which can decrease the specificity of this method--are considered. Though still under investigation, the potential contribution of ultrasonic tissue characterisation of the asynergic ventricular wall as an additional, or even alternative, marker of myocardial ischaemia, is discussed. Finally, educational problems related to the new tasks facing the anaesthesiologist involved in intra-operative echo-Doppler evaluation of cardiac function are also foreseen.
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OBJECTIVE: To compare a method of measuring energy expenditure and gas exchange using the Fick principle with the standard indirect calorimetry technique. DESIGN: Prospective study of a consecutive sample of postoperative patients. Oxygen consumption (VO2), CO2 production (VCO2), respiratory quotient, and energy expenditure were derived from measurements of variables, including oxygen content and cardiac output. Energy expenditure and gas exchange were measured simultaneously by continuous indirect calorimetry over a 60-min period. SETTING: Surgical ICU in a university hospital. PATIENTS: Twenty-six consecutive patients (45 to 80 yrs) who underwent sustained surgical trauma. Excluded from the study entry were patients with time-related fluctuations of hemodynamic variables, poor cooperation, patients who required supplemental oxygen, or mechanical ventilation. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: While the measurements of VO2 and VCO2 by calorimetry and thermodilution were significantly correlated with one another (for VO2, r2 = .93, p less than .001; for VCO2, r2 = .26, p less than .01), VO2 and VCO2 values by indirect calorimetry were consistently greater than VO2 and VCO2 values by the Fick method (p less than .01). The respiratory quotient calorimetric measurements ranged between 0.69 and 0.99, whereas the corresponding thermodilution measurements spread to impossible values, from 0.24 to 1.30 (0.821 +/- 0.07 vs. 0.740 +/- 0.24, p less than .05). There was an insignificant relationship (r2 = .06, p = .21) between the values of respiratory quotient by the two methods. A strong, positive correlation between energy expenditure measured by indirect calorimetry and energy expenditure measured by the Fick method was observed (r2 = .92, p less than .001). The limit of agreement between the two methods was -0.24 +/- 73 kcal/day/m2 (-1.00 +/- 305 kJ/day/m2). CONCLUSIONS: In postoperative patients, while VO2 and energy expenditure measurements by thermodilution are easy to perform and accurate for clinical purposes, VCO2, and respiratory quotient measurements are too imprecise and inaccurate to serve any useful function. Therefore, in those clinical situations in which an evaluation of respiratory quotient and substrate utilization may be useful for purposes of metabolic care of the surgical patient, precise measurements of gas exchange with indirect calorimetry are mandatory.
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Modern stereotactic surgical procedures were developed mainly because digital CT image gave us the opportunity to recognize the morphology and the site of a brain lesion, and, at the same time, CT offered a very easy and reliable way to calculate target coordinates because the brain scans are digital maps. Digital x-ray image obtained with an x-ray-intensifier and a TV Analog/Digital converter is not suitable for stereotactic use because image distortion is multifactorial and it is impossible to rectify. We have developed a new apparatus (Neurogil) for intra-operative use that is able to produce a digital image on a display, the measures displayed match exactly with the patient's brain. A linear array of 1024 photodiodes is working in front of an x-ray source and it collects the density image of the patient's head positioned between them. It shows the patient's head with the stereotactic frame exactly as a radiogram, but no distortion is present. Digital brain angiograms are possible with electronic subtraction, mathematical enhancement and with a stereoscopic view on a particular display. Any kind of mathematical calculation or computer-graphic application is possible. A special software was developed for stereotactic closed and open surgery.
The two main neurosurgical tools are the operative microscope and stereotactic apparatus. The operative microscope is essential in cisternal or ventricular surgery and the stereotactic apparatus is essential in approaching intracerebral lesions. Both given their best performance when the one aids the other. Small convexity lesions are best approach with stereotactic aid, and excellent microsurgical intracerebral lesions can be debulked with the operative microscope. Malignant tumours pursue their inevitable course but slow growing tumours and angiomas may have long survival even with one subtotal removal. The major problem in removing slow-growing tumors is the difficulty in distinguishing tumour from normal brain, but the stereotactic guide is useful in delimitating tumour volume. The results in 57 cases are described.
The simultaneous occurrence of meningioma and glioma is extremely rare. Three new cases and 54 adequately described in the literature are analyzed. Clinical diagnosis may be difficult due to discrepancy between clinical and radiological findings. Unexpected clinical deterioration following removal of a tumour and relapse simulating recurrence may occur. The introduction of CT technology does not seem to have offered the expected contribution to the early diagnosis of these coincidental lesions, at least before the introduction of the newer generation scanners or MRI. While removal of both tumours in one session yielded the best results, surgery for the sole glioma appeared to be associated with an unacceptably high mortality. Although several aetiopathogenetic hypotheses have been suggested for explaining this curious association, coincidental meningioma and glioma are most likely to be different primary brain tumours occurring randomly in the same individual.
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In most cases of brain stem expansive lesion a surgical approach is possible, but in each patient it must be evaluated if the surgical risk is proportional to the therapeutic result. Sometime surgery is limited to a biopsy sample, particularly in malignant lesions. We started stereotactic serial biopsy sampling in all CT or NMR intraaxial brain stem expansive lesions as a preliminary diagnostic procedure. The aim is to look for benign well delimited lesions that we consider for surgical removal or to drain haematomas and abscesses. 35 patients with brain stem expansive lesions were submitted to 47 surgical procedures: 35 stereotactic biopsies (one each patient) and, among them, 12 were major surgical procedures (with craniotomy) for microsurgical removal of the expansive lesions. 15 patients were in paediatric age. Suboccipital transcerebellar approach was performed in 25 mesencephalic, pontine, bulbar expansive lesions and frontal approach was limited to 10 thalamo-mesencephalic lesions. There was no mortality. Two patients were stereotactically drained and definitively cured.
Since 1981, high frequency jet ventilation (HFJV) has been used in 300 patients undergoing surgery, most commonly during i.v. general anaesthesia for endoscopy and surgery of the airways: laryngoscopy, bronchoscopy, laryngeal microsurgery and laser surgery (more than 230 patients); repair of tracheal stenosis, tracheal sleeve pneumonectomy and tracheal sleeve lobectomy. HFJV was administered through a narrow injection catheter inserted in the airway, with a second rigid catheter positioned distally to the injector in the airway for gas sampling and measurement of airway pressure. In all subjects gas exchange was satisfactory, even during tracheoplasty and bronchoplasty.
CT diagnosed brain stem malignant lesions were in the past almost always treated with radiation therapy (RT). Eventually this turned out to be a grave mistake. With stereotactic serial biopsies of all brain stem expanding lesions we have been able to verify the histological nature in all cases but two and to prevent a blind therapeutic approach. In 24 patients bearing CT diagnosed expansive lesions into the brain stem 68 samples were taken during 24 stereotactic procedures. In 8 patients surgical removal of the expanding lesion was attempted after stereotactic biopsy.