PubMed · 91821
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K E Britton, M Granowska. 1979-11-17. Images of brain function.. https://doi.org/10.1016/s0140-6736(79)92481-4
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BACKGROUND: Proximal Femoral Fracture (PFF) or 'hip fracture' is a frequent injury, and adverse outcomes are common. Many patients are elderly, with significant comorbidity. Several factors suggest the importance of developing appropriate techniques to optimize intravascular fluid volume. These may include protocols that enhance the efficacy of clinicians' assessments, invasive techniques such as oesophageal Doppler or central venous pressure monitoring, or advanced non-invasive techniques such as plethysmographic pulse volume determination. OBJECTIVES: To determine the optimal method of fluid volume optimization for adult patients undergoing surgical repair of hip fracture. Comparisons of fluid types (e.g. crystalloid vs. colloid) or of blood transfusion strategies or of other pharmacological interventions (e.g. inotropes) are not considered in this review. SEARCH STRATEGY: Randomized controlled trials (RCTs) since 1985 were identified by searching MEDLINE, EMBASE, the Cochrane Library, the Cochrane Anaesthesia Group's specialized Controlled Trials Register and bibliographies of retrieved articles. Relevant journals and conference proceedings were handsearched. SELECTION CRITERIA: RCTs comparing a fluid optimization intervention with normal practice (control) or with another fluid optimization intervention, in patients following PFF undergoing surgery of any type under anaesthesia of any type. DATA COLLECTION AND ANALYSIS: Searches and exclusion of clearly irrelevant articles were performed by one reviewer. Two reviewers examined independently the remaining studies, extracting study quality and results data. A wide range of short- and long-term outcome data was sought. Study quality was assessed using a ten-point instrument and studies were excluded if they did not meet the study criteria or if results were likely to be biased. Due to a lack of consistency in reporting, combination of data was not generally possible. MAIN RESULTS: Searches identified only four trials, of which two studies, randomizing a total of 130 patients, were of adequate quality and addressed the review question. Both studies were of invasive advanced haemodynamic monitoring during the intraoperative period only. One study randomized patients to 'normal care' or optimization using oesophageal Doppler; the second study randomized patients to 'normal care', oesophageal Doppler or central venous pressure monitoring. In each study, invasive monitoring led to a significant increase in volume of fluid infused and a reduction in length of hospital stay. The pooled Peto odds ratio for in-hospital fatality was 1.44 (95% confidence interval 0.45-4.62). Neither study followed patients beyond hospital discharge or assessed functional outcomes (for example return to previous accommodation). No serious complications were reported to be directly attributable to the monitoring interventions. There were no studies of protocol-guided fluid optimization or of advanced non-invasive techniques. REVIEWER'S CONCLUSIONS: Invasive methods of fluid optimization during surgery may shorten hospital stay, but their effects on other important, patient-centred, longer-term outcomes are uncertain. An adverse effect on fatality cannot be excluded. Other fluid optimization techniques have not been evaluated. The lack of randomized studies of adequate quality addressing this important question is disappointing given the high incidence and frequently adverse outcome of PFF. More research is needed.
In recent years a number of physiological models have gained prominence in the analysis of dynamic contrast-enhanced T1-weighted MRI data. However, there remains little evidence to support their use in estimating the absolute values of tissue physiological parameters such as perfusion, capillary permeability, and blood volume. In an attempt to address this issue, data were simulated using a distributed pathway model of tracer kinetics, and three published models were fitted to the resultant concentration-time curves. Parameter estimates obtained from these fits were compared with the parameters used for the simulations. The results indicate that the use of commonly accepted models leads to systematic overestimation of the transfer constant, Ktrans, and potentially large underestimates of the blood plasma volume fraction, Vp. In summary, proposals for a practical approach to physiological modeling using MRI data are outlined.
UNLABELLED: We examined the effects of low-pressure carbon dioxide pneumoperitoneum on regional cerebral oxygen saturation (ScO(2)) and cerebral blood volume (CBV) in children. Fifteen children, ASA I--III, scheduled for laparoscopic fundoplication, were investigated in the head-up position (10) and ventilated to a baseline end-tidal CO(2) (PETCO(2)) between 25 and 33 mm Hg. Ventilatory settings remained unchanged during the operation. ScO(2) and CBV were assessed with near-infrared spectroscopy and recorded together with end-tidal and arterial carbon dioxide (PaCO(2)) at 5 time points: before insufflation, 30, 60, and 90 min after the start of CO(2) insufflation, and 10 min after desufflation. The intraabdominal pressure was kept between 5 and 8 mm Hg. During insufflation, PETCO(2) increased from 30.0 plus minus 2.8 to 38.3 plus minus 5.1 mm Hg (P < 0.001) and PaCO(2) increased from 32.0 plus minus 4.7 to 40.4 plus minus 5.9 mm Hg (P < 0.001). ScO(2) increased by 15.7% plus minus 8.8% (from 61 plus minus 9 to 70 plus minus 9 arbitrary units ) (P < 0.001). CBV increased by 4.6% plus minus 8.8% (from 123 plus minus 66 to 128 plus minus 66 arbitrary units [P = 0.048]). After desufflation, PETCO(2) and PaCO(2) decreased, but did not return to preinsufflation values. ScO(2) and CBV also decreased after desufflation. In conclusion, hyperventilation and the head-up position before CO(2) insufflation are not sufficient to prevent the CO(2)-mediated cerebral hemodynamic effects of low-pressure pneumoperitoneum (5--8 mm Hg) in children. IMPLICATIONS: Peritoneal CO(2) absorption during laparoscopic surgery causes hypercapnia and CO(2)-mediated cerebral hemodynamic effects. Hyperventilation and the head-up position before CO(2) insufflation is not sufficient to counteract these effects of low-pressure pneumoperitoneum (5--8 mm Hg) in children.