| 1. |
- Dahm, S L, et al.
(författare)
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Charcoal as an airway isoflurane reflection filter
- 1998
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Ingår i: European Journal of Anaesthesiology. - : Ovid Technologies (Wolters Kluwer Health). - 1365-2346 .- 0265-0215. ; 15:2, s. 230-233
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Tidskriftsartikel (refereegranskat)abstract
- The isoflurane-saving and CO2-retaining effects of a charcoal filter were compared with a Siemens standard heat and moisture (HME) exchanger and an emptied specimen (dummy). Isoflurane was delivered during the inspiratory phase and consumption investigated at 10, 15 and 25 cycles min-1. The investigation was performed by ventilation with humidified air with a constant end-tidal CO2 and temperature. For a comparison, isoflurane was delivered in a conventional manner via the ventilator. The arrangement with a charcoal filter reduced the isoflurane consumption by a factor of 2.0-2.6, depending on ventilatory rate. Most of the saving was a result of the method of isoflurane delivery (factor 1.4-2.0), while adding the reflector gave a further reduction (factor 1.3-1.5). One circumstance that reduced the net efficiency of the charcoal filter was that it also reflected CO2; consequently, total minute ventilation had to be increased to maintain constant end-tidal CO2.
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| 2. |
- Ekelund, A, et al.
(författare)
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Additional colloids have only a minor haemodilutive effect after surgery for aneurysmal subarachnoid haemorrhage
- 1999
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Ingår i: British Journal of Neurosurgery. - : Informa UK Limited. - 0268-8697 .- 1360-046X. ; 13:4, s. 399-404
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Tidskriftsartikel (refereegranskat)abstract
- Haemodilution is commonly used as prophylaxis, as well as treatment for cerebral ischaemia after aneurysmal subarachnoid haemorrhage (SAH). Thirty-six patients operated for aneurysmal SAH were evaluated retrospectively; 24 received haemodilutive therapy and 12 patients, as a control group, received no additional therapy. There was a 'spontaneous' drop in haematocrit by 22% in both groups, and a corresponding drop in haemoglobin by 23% in the treatment group and 19% in the non-haemodiluted group, during the first 4 days after the SAH. After the initial decrease the haematocrit remained stable between 0.28 and 0.33 until day 14 in both groups. The haemodilutive group had only a minor lower haematocrit level during days 8-12 as the additional fluid resulted in increased renal excretion. This minor difference was, however, significant (p < 0.02).
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| 3. |
- Ekelund, A, et al.
(författare)
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Transcranial cerebral oximetry related to transcranial Doppler after aneurysmal subarachnoid haemorrhage
- 1998
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Ingår i: Acta Neurochirurgica. - : Springer Science and Business Media LLC. - 0001-6268 .- 0942-0940. ; 140:10, s. 1029-1036
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Tidskriftsartikel (refereegranskat)abstract
- Noninvasive methods for detecting cerebral artery vasospasm, still a serious complication following aneurysmal subarachnoid haemorrhage, are of vital interest. Up-to-date transcranial Doppler ultrasound (TCD) has proved to be sensitive in detecting vasospasm in the middle cerebral artery, but has less accuracy for other cerebral arteries. Transcranial cerebral oximetry (TCCO) is a new non-invasive technique which may increase the reliability for detecting cerebral ischaemia. The purpose of the present study was to evaluate a putative correlation between TCCO and TCD. We examined the two hemispheres in 14 patients with the aim of evaluating a proposed correlation between TCD and TCCO. Analysis of all absolute values (maximum TCD mFV and minimum TCCO saturation, respectively) in all series indicate a correlation between TCCO and TCD, p < 0.01, r = -0.62. All patients with TCD mean flow velocity > 120 cm/s also presented TCCO saturation < 60%. Conversely, all patients with normal TCCO saturation (> or = 63%) presented normal or moderately increased TCD velocities. In clinical neurosurgical practice it is of great interest if a true correlation between TCD and TCCO exists. The present results support the assumption that TCCO may enhance the reliability for detecting cerebral ischaemia after aneurysmal subarachnoid haemorrhage.
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| 4. |
- Enlund, M, et al.
(författare)
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Narkosdosering en svår balansgång
- 1998
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Ingår i: Läkartidningen. - 0023-7205. ; 95:48, s. 5477-5482
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Tidskriftsartikel (refereegranskat)abstract
- The optimal dosage of anaesthetic agents may be difficult. Not only does the intensity of surgical stimuli vary during a surgical procedure, but drug sensitivity varies between subjects exposed to comparable stimuli. Moreover, clinically monitored body reactions do not always reflect the balance between central nervous system effects of the surgical stimuli and of the anaesthetic agent. Therefore, the specialist in anaesthesiology requires access to additional methods of monitoring to enable dosage to be optimised for each patient, minute by minute, thus improving the chances of maintaining an appropriate depth of anaesthesia. Two electro-encephalographic techniques are presented in the article, and aspects of under- and over-dosage of anaesthetic agents are discussed.
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| 5. |
- Reinstrup, Peter, et al.
(författare)
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Distribution of cerebral blood flow during anesthesia with isoflurane or halothane in humans
- 1995
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Ingår i: Anesthesiology. - 1528-1175. ; 82:2, s. 359-366
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Halothane and isoflurane have been shown to induce disparate effects on different brain structures in animals. In humans, various methods for measuring cerebral blood flow (CBF) have produced results compatible with a redistribution of CBF toward deep brain structures during isoflurane anesthesia in humans. This study was undertaken to examine the effects of halothane and isoflurance on the distribution of CBF. METHODS: Twenty ASA physical status patients (four groups, five in each) anesthetized with either isoflurane or halothane (1 MAC) during normo- or hypocapnia (PaCO2 5.6 or 4.2 kPa (42 or 32 mmHg)) were investigated with a two-dimensional CBF measurement (CBFxenon, intravenous 133xenon washout technique) and a three-dimensional method for measurement of the regional CBF (rCBF) distribution with single photon emission computer-aided tomography (SPECT; 99mTc-HMPAO). In the presentation of SPECT data, the mean CBF of the brain was defined as 100%, and all relative flow values are related to this value. RESULTS: The mean CBFxenon level was significantly influenced by the PaCO2 as well as by the anesthetic used. At normocapnia, patients anesthetized with halothane had a mean CBFxenon of 40 +/- 3 (SE) ISI units. With isoflurane, the flow was significantly (P < 0.01, 33 +/- 3 ISI units) less than with halothane. Hypocapnia decreased mean CBFxenon (P < 0.0001) during both anesthetics (halothane 24 +/- 3, isoflurane 13 +/- 2 ISI units). The effects on CBFxenon, between the anesthetics, differed significantly (P < 0.01) also during hypocapnia. There were significant differences in rCBF distribution measured between the two anesthetics (P < 0.05). During isoflurane anesthesia, there was a relative increase in flow values in subcortical regions (thalamus and basal ganglia) to 10-15%, and in pons to 7-10% above average. Halothane, in contrast, induced the highest relative flow levels in the occipital lobes, which increased by approximately 10% above average. The rCBF level was increased approximately 10% in cerebellum with both anesthetics. Changes in PaCO2 did not alter the rCBF distribution significantly. CONCLUSIONS: There is a difference in the human rCBF distribution between halothane and isoflurane with higher relative flows in subcortical regions during isoflurane anesthesia. However, despite this redistribution, isoflurane anesthesia resulted in a lower mean CBFxenon than did anesthesia with halothane.
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| 6. |
- Reinstrup, Peter, et al.
(författare)
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Regional cerebral blood flow (SPECT) during anaesthesia with isoflurane and nitrous oxide in humans
- 1997
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Ingår i: British Journal of Anaesthesia. - 1471-6771. ; 78:4, s. 407-411
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Tidskriftsartikel (refereegranskat)abstract
- Nitrous oxide and isoflurane have different effects on absolute cerebral blood flow (CBF) and regional distribution of CBF in humans. In this study we examined the effects of isoflurane in combination with nitrous oxide on CBF. We studied 10 patients (two groups of five patients, ASA I) anaesthetized with 50% nitrous oxide and either 0.5 or 1.0 MAC of isoflurane during normocapnia (PaCO2 5.7 kPa) using two-dimensional CBF measurement (CBFxenon) (i.v. 133xenon washout technique) and a three-dimensional method for measurement of regional CBF (rCBF) distribution with SPECT (single photon emission computer-aided tomography with 99mTc- HMPAO). The results were compared with 1.0 MAC of isoflurane from a previous study performed in exactly the same way as the present investigation. During normocapnia, anaesthesia with 50% nitrous oxide and 0.5 MAC of isoflurane resulted in a mean CBFxenon of 45 (SEM 5) ISI units. Increasing the isoflurane concentration to 1.0 MAC had no significant effect on mean CBFxenon (53 (5) ISI units). Both flow values were significantly (P = 0.01) higher than the CBFxenon value obtained when 1 MAC of isoflurane was administered alone (33 (3) ISI units). There were no significant differences in rCBF distribution regardless of whether or not isoflurane was given alone or together with nitrous oxide at 0.5 or 1 MAC. In all situations there were higher relative flows in subcortical regions (thalamus and basal ganglia, 10%) and in the pons (7-10% above average). rCBF in the cerebellum was approximately 10% greater than average. In summary, we have found that mean CBF was greater with combined nitrous oxide and isoflurane anaesthesia than previously found with isoflurane alone; however, relative flow distribution was similar.
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| 7. |
- Wallerstedt, S M, et al.
(författare)
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Effects of propofol on isolated human pial arteries
- 1999
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Ingår i: Acta Anaesthesiologica Scandinavica. - : Wiley. - 0001-5172. ; 43:10, s. 1065-1068
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The intravenous anaesthetic propofol has been reported to increase cerebral vascular resistance in vivo. The underlying mechanisms are not fully understood, but may include effects on metabolism and direct effects on the vascular smooth muscle. The present study was designed to evaluate the direct effects of propofol on human pial arteries. METHODS: We investigated the direct effect of propofol (10(-6)-10(-4) M) on isolated human pial arteries at basal tension as well as the influence on contractions induced by 5-hydroxytryptamine, prostaglandin F2alpha, noradrenaline and potassium chloride. RESULTS: Propofol did not change the basal tension. Propofol at 10(-6) and 10(-5) M did not affect the concentration-response curves of any of the contractile agents tested. Propofol at the supraclinical concentration 10(-4) M reduced the contractions induced by all contractile agents. CONCLUSION: Propofol reduces the tone of human pial arteries in vitro at supraclinical concentrations, but has no effect on the tone at clinically relevant concentrations.
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