Anesthesia and analgesia
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Anesthesia and analgesia · Jun 2002
The incidence and risk factors for hypotension after spinal anesthesia induction: an analysis with automated data collection.
We sought to identify factors that are associated with hypotension after the induction of spinal anesthesia (SpA) by using an anesthesia information management system. Hypotension was defined as a decrease of mean arterial blood pressure of more than 30% within a 10-min interval, and relevance was defined as a therapeutic intervention with fluids or pressors within 20 min. From January 1, 1997, to August 5, 2000, data sets from 3315 patients receiving SpA were recorded on-line by using the automatic anesthesia record keeping system NarkoData. Hypotension meeting the predefined criteria occurred in 166 (5.4%) patients. Twenty-nine patient-, surgery-, and anesthesia-related variables were studied by using univariate analysis for a possible association with the occurrence of hypotension after SpA. Logistic regression with a forward stepwise algorithm was performed to identify independent variables (P < 0.05). The discriminative power of the logistic regression model was checked with a receiver operating characteristic curve. Calibration was tested with the Hosmer-Lemeshow goodness-of-fit test. The univariate analysis identified the following variables to be associated with hypotension after SpA: age, weight, height, body mass index, amount of plain bupivacaine 0.5% used for SpA, amount of colloid infusion before puncture, chronic alcohol consumption, ASA physical status, history of hypertension, urgency of surgery, surgical department, sensory block height of anesthesia, and frequency of puncture. In the multivariate analysis, independent factors for relevant hypotension after SpA consisted of three patient-related variables ("chronic alcohol consumption," odds ratio [OR] = 3.05; "history of hypertension," OR = 2.21; and the metric variable "body mass index," OR = 1.08) and two anesthesia-related variables ("sensory block height," OR = 2.32; and "urgency of surgery," OR = 2.84). The area of 0.68 (95% confidence interval, 0.63-0.72) below the receiver operating characteristic curve was significantly greater than 0.5 (P < 0.01). The goodness-of-fit test showed a good calibration of the model (H = 4.3, df = 7, P = 0.7; C = 7.3, df = 8, P = 0.51). This study contributes to the identification of patients with a high risk for hypotension after SpA induction, with the risk increasing two- or threefold with each additional risk factor. ⋯ By using automated data collection, 5 (chronic alcohol consumption, history of hypertension, body mass index, sensory block height, and urgency of surgery) of 29 variables could be detected as having an association with hypotension after spinal anesthesia induction. The knowledge of these risk factors should be useful in increasing vigilance in those patients most at risk for hypotension, in allowing a more timely therapeutic intervention, or even in suggesting the use of alternative methods of spinal anesthesia, such as titrated continuous or small-dose spinal anesthesia.
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Anesthesia and analgesia · Jun 2002
Pressure support compared with controlled mechanical ventilation in experimental lung injury.
It has been suggested that, in acute lung injury (ALI), spontaneous breathing activity may increase oxygenation because of an improvement of ventilation-perfusion distribution. Pressure support ventilation (PSV) is one of the assisted spontaneous breathing modes often used in critical care medicine. We sought to determine the prolonged effects of PSV on gas exchange in experimental ALI. We hypothesized that PSV may increase oxygenation because of an improvement in ventilation-perfusion distribution. Thus, ALI was induced in 20 pigs by using repetitive lung lavage. Thereafter, the animals were randomized to receive either PSV with a pressure level set to achieve a tidal volume >4 mL/kg and a respiratory rate <40 min(-1) (n = 10) or controlled mechanical ventilation (CMV) with a tidal volume of 10 mL/kg and a respiratory rate of 20 min(-1) (n = 10). Positive end-expiratory pressure was set at 10 cm H(2)O in both groups. Blood gas analyses and determination of ventilation-perfusion (.V(A)/.Q) distribution were performed at the onset of ALI and after 2, 4, 8, and 12 h. The main result was an improvement of oxygenation because of a decrease of pulmonary shunt and an increase of areas with normal .V(A)/.Q ratios during PSV (P < 0.005). However, during CMV, a more pronounced reduction of shunt was observed compared with PSV (P < 0.005). We conclude that, in this model of ALI, PSV improves gas exchange because of a reduction of .V(A)/.Q inequality. However, improvements in .V(A)/.Q distribution may be more effective with CMV than with PSV. ⋯ Assisted spontaneous breathing may have beneficial effects on gas exchange in acute lung injury. We tested this hypothesis for pressure support ventilation in an animal model of acute lung injury. Our results demonstrate that pressure support does not necessarily provide better gas exchange than controlled mechanical ventilation.
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Anesthesia and analgesia · Jun 2002
Case ReportsAn unusual presentation of end-tidal carbon dioxide after esophageal intubation.
This article discusses the inherent danger of general anesthesia and the need for a variety of tools to safely manage the airway.
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Anesthesia and analgesia · Jun 2002
Ventilation with negative airway pressure induces a cytokine response in isolated mouse lung.
We tested the hypothesis that, under relatively low tidal volume (VT) mechanical ventilation, continuing lung decruitment induced by negative end-expiratory pressure (NEEP) would increase the lung cytokine response, potentially contributing to lung injury. Mouse lungs were excised and randomly assigned to one of 3 different ventilatory strategies: 1) the zero end-expiratory pressure group served as a control, 2) the NEEP7 group received a NEEP of -7.5 cm H(2)O, and 3) the NEEP15 group received a NEEP of -15 cm H(2)O. In all 3 groups, a VT of 7 mL/kg was used. After 2 h of ventilation, lung lavage fluid was collected for measurements of tumor necrosis factor-alpha, monocyte chemoattractant protein-1, and lactate dehydrogenase. Increases in plateau pressure before and after mechanical ventilation were significantly greater in the NEEP15 group compared with the zero end-expiratory pressure group or NEEP7 group. Lung compliance was decreased in the NEEP15 compared with the other two groups. Concentrations of tumor necrosis factor-alpha, monocyte chemoattractant protein-1, and lactate dehydrogenase in lung lavage were larger in the NEEP15 group than in the other groups. Atelectatic lung during repeated collapse and reopening of lung units accentuates the lung cytokine response that may contribute to lung injury even during relatively low VT mechanical ventilation. ⋯ Repeated closing and reopening of lung units induced by negative end-expiratory pressure resulted in lung inflammation and cell injury even under mechanical ventilation using a normal tidal volume. This finding may have clinical relevance in certain patients who are prone to atelectasis during mechanical ventilation.
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Anesthesia and analgesia · Jun 2002
The effects of OP-1206 alpha-CD on walking dysfunction in the rat neuropathic intermittent claudication model.
IV prostaglandin E1 improves clinical symptoms in patients with spinal canal stenosis. In the present study, we assessed the effects of OP-1206 alpha-CD, an orally active prostaglandin E1 analog, on walking dysfunction in the rat neuropathic intermittent claudication model. To induce spinal stenosis, two pieces of silicon rubber were placed in the lumbar (L4-6) epidural space in rats. Postsurgical walking function was measured using a treadmill apparatus. Spinal cord blood flow (SCBF) and skin blood flow (SKBF) were measured using a laser-Doppler flowmeter. OP-1206 alpha-CD was administered orally bid for 11 days from postoperative Day 3. In Control nontreated rats, a significant walking dysfunction was observed from Day 1 after the induction of spinal stenosis and persisted for 14 days when compared with the Sham-Operated group. On postoperative Day 15, SCBF revealed a significant reduction in the territory of spinal stenosis, although SKBF was not affected. OP-1206 alpha-CD significantly improved walking dysfunction on postoperative Days 5 (300 microg/kg), 7 (150 and 300 microg/kg), and 14 (150 and 300 microg/kg) when compared with the Vehicle-Treated group. On postoperative Day 15, the decrease in SCBF was significantly (150 and 300 microg/kg) improved by OP-1206 alpha-CD treatment, albeit SKBF remained unaffected. These data show that oral treatment with OP-1206 alpha-CD is effective in improving walking dysfunction induced by spinal canal stenosis, and this therapeutic effect is likely mediated by improved SCBF at the territory of spinal stenosis. ⋯ Intermittent motor dysfunction is a clinical symptom associated with partial spinal compression. The present study provides evidence that oral treatment with the prostaglandin E1 analog (OP-1206 alpha-CD) is effective in improving motor dysfunction and spinal cord blood flow in rats with spinal compression.