Acta anaesthesiologica Scandinavica
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Acta Anaesthesiol Scand · Jan 1977
Comparative StudyThe 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. ⋯ 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.
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Capnography and measurement of the respiratory minute volume were carried out on normal, conscious subjects during breathing of pure O2 via a Mapleson C modification of a Magill attachment, with and without continuous gas evacuation. The measurements were performed in two series, with intermittent discharge and with continuous evacuation. ⋯ The measurements indicated CO2 accumulation at a flow below 200% of the respiratory minute volume. There was no significant difference between the systems with and without evacuation.
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Acta Anaesthesiol Scand · Jan 1976
Anesthetic management of posterior fossa surgery in the sitting position.
From the surgical aspect, the sitting position gives good surgical access to the operative site, improves venous drainage, gives a better view of facial area for monitoring evoked responses from cranial nerve stimulation and allows for better ventilation. Conversely, the sitting position can present complications such as air emboli, postural hypotension and serious cardiac arrhythmias due to surgical stimulation of cranial nerves and brainstem. This paper presents our clinical experience in 180 neurosurgical procedures on the posterior fossa in the sitting position. ⋯ Surgical stress also accounted for the 13 patients (7%) having frequent premature ventricular extrasystoles. One case of profound hypotension and another case of virtual cardiac standstill were noted during the use of the bipolar electrocautery at or near the fifth nerve exit from brainstem. Additional hemodynamic data, the physiopathology, diagnosis and treatment of air embolism is discussed.
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Acta Anaesthesiol Scand · Jan 1976
Breathing mechanics, dead space and gas exchange in the extremely obese, breathing spontaneously and during anaesthesia with intermittent positive pressure ventilation.
Breathing mechanics and gas exchange were studied in 10 extremely obese subjects (average weight 138 kg) prior to and during anaesthesia with mechanical ventilation. Breathing mechanics were analysed from measurements of transpulmonary pressure (during anaesthesia, trans-chest wall pressure as well) inspiratory gas flow and tidal volume. Gas exchange was studied by analysing inspired and from the Bohr equation, and the division into anatomical and alveolar dead space was arrived at by capnography. ⋯ A moderate hypoxaemia was recorded during spontaneous breathing, and the alveolar-arterial oxygen tension difference was slightly elevated. During anaesthesia this difference was markedly greater. It is concluded that the most probable reason for the relative hypoxaemia is right-to-left shunting.