Anesthesia and analgesia
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Anesthesia and analgesia · Jan 2003
Comparative StudyA comparison of lactated ringer's solution to hydroxyethyl starch 6% in a model of severe hemorrhagic shock and continuous bleeding in dogs.
In this randomized, controlled study in dogs, we examined the short-term effects of blood pressure targeted fluid resuscitation with colloids or crystalloids solutions on systemic oxygen delivery, and lactate blood concentration. Fluid resuscitation using hydroxyethyl starch (HES) 6% to a mean arterial blood pressure (MAP) of 60 mm Hg was compared with lactated Ringer's solution (LR) to a MAP of 60 or 80 mm Hg (LR60 and LR80, respectively). The model was one of withdrawal of blood to a MAP of 40 mm Hg through an arterial catheter that was then connected to a system allowing bleeding to occur throughout the study whenever MAP exceeded 40 mm Hg. Target MAP was maintained for 60 min with a continuous infusion of the designated fluid replacement. All 15 dogs (5 in each group) survived until the last measurement. Blood loss in the LR80 group (2980 +/- 503 mL) (all values mean +/- SD) was larger than in the LR60 and HES60 groups (1800 +/- 389 mL, and 1820 +/- 219 mL, respectively) (P < 0.001). Whereas 840 +/- 219 mL of HES60 was needed to maintain target MAP, 1880 +/- 425 mL of LR was needed in the LR60 group, and 4590 +/- 930 mL in the LR80 group (P < 0.001). Lactate blood concentrations were smaller and delivered O(2) higher in the HES60 group (35 +/- 17 mg/dL and 239 +/- 61 mL/min, respectively) in comparison to the LR60 group (89 +/- 18 mg/dL and 140 +/- 48 mL/min, respectively) and the LR80 group (75 +/- 23 mg/dL and 153 +/- 17 mL/min, respectively) (P = 0.02 and P = 0.026). In conclusion, fluid resuscitation during uncontrolled bleeding, to a target MAP of 60 mm Hg, using HES60 resulted in larger oxygen delivery and smaller systemic lactate A resuscitation to a target MAP of 60 or 80 mm Hg using LR. ⋯ Fluid resuscitation to a target mean arterial blood pressure of 60 mm Hg during uncontrolled bleeding resulted in larger oxygen delivery and smaller systemic lactate concentrations when hydroxyethyl starch 6% was used, in comparison to lactated Ringer's solution resuscitation to a target mean arterial blood pressure of 60 or 80 mm Hg.
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Anesthesia and analgesia · Jan 2003
Case ReportsConversion disorder after implant of a spinal cord stimulator in a patient with a complex regional pain syndrome.
This case history describes the treatment of a patient suffering with persistent pain. He was treated surgically with implantation of a spinal cord stimulator. After surgery, a partial paralysis that could not be explained medically and that was probably related to emotional factors occurred, and cognitive behavioral treatment was begun. This paper discusses the importance of considering social and psychological factors when medical treatment options are considered.
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Reports of anesthesia personnel shortages in 2001 led to the first comprehensive analysis of labor supply and demand for anesthesiologists since 1993. We now update this analysis and forecast, incorporating newly available data about residency composition, American Board of Anesthesiology and Certified Registered Nurse Anesthetist certification, the 2002 residency match, surgical facilities, and the US physician workforce. In addition, US residency programs were surveyed; national health care utilization and economic data were reviewed. Adjusted for the new information, our model still shows an anesthesiologist shortfall in 2002, projected to continue through 2005. We now estimate a current shortage of 1100-3800 anesthesiologists in 2002, on the basis of past service demand growth assumptions of 2%-3%, respectively. By 2005 this number is expected to be 500-3900, depending on a future service demand growth of 1.5%-2%, respectively. To avoid a surplus of anesthesiologists in 2006-2010, our model suggests that the number of graduates should level out at 1600 yearly, with a 1.5% service demand growth. To forecast the anesthesia personnel market more accurately, thereby helping supply match demand, substantially better quantification of future demand for anesthesia services is needed. If sustained growth in service demand >1.5% is likely, entry into the specialty should be encouraged beyond the current level. ⋯ With updates from training programs, surgical activity, and other sources, our previously described model estimates a continuing shortfall of 1000-3800 anesthesiologists in 2002 and 500-3900 in 2005, assuming that service demand growth is 1.5% or 2% annually. If service growth >1.5% is likely, entry into the specialty should be encouraged beyond current levels.
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Anesthesia and analgesia · Jan 2003
Validity of arterial and mixed venous oxygen saturation measurements in a canine hemorrhage model after resuscitation with varying concentrations of hemoglobin-based oxygen carrier.
In this study, we evaluated the validity of saturation measurements in mixed venous and arterial blood during posthemorrhagic anemia and resuscitation with varying levels of hemoglobin-based oxygen carrier (Hemoglobin glutamer-200 [bovine]; Oxyglobin [Hb-200]). Nineteen anesthetized, splenectomized, mixed-breed dogs were anesthetized (two were excluded from the data because they did not survive the exsanguination, supporting the validity of the model). Their pulmonary arteries were cannulated with the Abbott QVUE Oximetrix 3 catheter. An 18-gauge catheter was placed in the femoral artery, and a reusable Nellcor probe was applied to the tongue. Mixed venous and arterial samples were drawn at baseline, after 40% hemorrhage (to keep arterial pressure at 50 mm Hg), and postresuscitation with 30 mL/kg of 6% hetastarch in lactated Ringer's solution (n = 4), 10 mL/kg of Hb-200, 20 mL/kg of hetastarch (n = 6), 20 mL/kg of Hb-200, and 10 mL/kg of hetastarch (n = 7). Samples were compared with oxygen content from the LEXO2CON-K oxygen analyzer, and oxygen content was calculated for all values from the monitors. Results were compared by using analysis of variance. There was good correlation (0.97 > or = r > or = 0.92) for the measured versus calculated hemoglobin oxygen saturation values at baseline. After resuscitation, the correlation between calculated and measured values of oxygen content was significantly smaller for all tested instruments. The values of oxygen content calculated from the oxygen saturation monitor and from the oximetric pulmonary artery can deviate by as much as 20% from directly measured values. We conclude that the administration of this oxygen therapeutic may interfere with the values of some monitors. ⋯ This study evaluated oxygen saturation monitors in a canine model of acute blood loss and resuscitation with a blood substitute and found that these may interfere with the monitors' results in a dose-dependent way.
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Anesthesia and analgesia · Jan 2003
Glycine receptors mediate part of the immobility produced by inhaled anesthetics.
Many inhaled anesthetics potentiate the effect of glycine on inhibitory strychnine-sensitive glycine receptors in vitro, supporting the view that this receptor could mediate the immobility produced by inhaled anesthetics during noxious stimulation (i.e., would underlie minimum alveolar anesthetic concentration [MAC]). There are quantitative differences between anesthetics in their capacity to potentiate glycine's effect in receptor expression systems: halothane (most potentiation), isoflurane (intermediate), and cyclopropane (minimal). If glycine receptors mediate MAC, then their blockade in the spinal cord should increase the MAC of halothane more than that of isoflurane and isoflurane MAC more than cyclopropane MAC; the increases in MAC should be proportional to the receptor potentiation produced in vitro. Rats with chronically implanted intrathecal catheters were anesthetized with halothane, isoflurane, or cyclopropane. During intrathecal infusion of artificial cerebrospinal fluid, MAC was determined. Then MAC was re-determined during an infusion of 3, 12, 24, or 48 (isoflurane only) micro g/min of strychnine (strychnine blocks glycine receptors) in artificial cerebrospinal fluid. Strychnine infusion increased MAC in proportion to the enhancement of glycine receptors found in vitro. The maximum effect was with an infusion of 12 micro g/min. For the combined results at 12 and 24 micro g/min of strychnine, the increase in MAC correlated with the extent of in vitro potentiation (r(2) = 0.82). These results support the hypothesis that glycine receptors mediate part of the immobilization produced by inhaled anesthetics. ⋯ In vitro, halothane potentiates glycine's effect on strychnine-sensitive glycine receptors more than isoflurane and isoflurane more than cyclopropane. The present in vivo work indicates that antagonism of the glycine receptor with strychnine increases minimum alveolar anesthetic concentration for halothane more than isoflurane and isoflurane more than cyclopropane. Such results support the notion that glycine receptors may mediate part of the immobility produced by inhaled anesthetics.