Anesthesia and analgesia
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Anesthesia and analgesia · Nov 1997
Clinical TrialAcute normovolemic hemodilution can replace preoperative autologous blood donation as a standard of care for autologous blood procurement in radical prostatectomy.
Predonation of autologous blood (PAD) is a standard of care for patients undergoing radical prostatectomy, but recent studies have shown that PAD is not cost-effective. Acute normovolemic hemodilution (ANH) is an alternative autologous blood procurement technique that is much less costly than PAD. We compared the efficacy and costs of ANH alone to ANH combined with PAD. Two hundred-fifty patients who predonated fewer than 3 units of autologous blood before radical prostatectomy underwent ANH to a target hematocrit of 28%. Perioperative hematocrit levels, transfusion outcomes and costs, and postoperative outcomes were compared for patients who predonated 0, 1, or 2 units of blood before surgery. A computer model was used to estimate the savings in red blood cells (RBC) associated with each autologous intervention. ANH alone resulted in a 21% allogeneic transfusion rate and contributed a mean net savings of 112 mL RBC in blood conservation (equivalent to 0.6 unit of blood). The addition of 1 or 2 units of PAD reduced allogeneic exposure rates to 6% or 0%, respectively. Overall, patients who predonated blood had a mean net loss of 198 mL of RBC (equivalent to 1 blood unit), due to both an absence in compensatory erythropoiesis and to the wastage of 60% of the blood units donated. Patients who underwent ANH alone had a 60% reduction in mean total transfusion costs ($103 +/- $102) compared with patients who predeposited 2 units of autologous blood in addition to ANH ($269 +/- $11, P < 0.05). We conclude that ANH can replace PAD as an autologous blood option because it is less costly and equally effective. A combination of ANH and PAD can further decrease allogeneic blood exposure, but it increases transfusion costs and wastage. ⋯ A patient's own blood can be obtained for use in surgery by predonation or acute normovolemic hemodilution on the day of surgery. Both blood collection techniques decrease the need for blood bank transfusions, but acute normovolemic hemodilution is less expensive and more convenient for patients.
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Anesthesia and analgesia · Nov 1997
Risk factors for neurologic deterioration after revascularization surgery in patients with moyamoya disease.
To investigate the risk factors for postoperative neurological deterioration in patients with moyamoya disease, we retrospectively reviewed the perioperative course of 368 cases of revascularization surgery in 216 patients with this disease. Risk factors anecdotally associated with postoperative ischemic events were analyzed by comparing groups with or without a history of such events on the operative day. Ischemic events were noted in 14 cases (3.8%), 4 of which were defined as strokes and the others as transient ischemic attack (TIA). Postoperative neurological deterioration more often developed in patients who suffered from frequent TIAs, had precipitating factors for TIA, and underwent indirect nonanastomotic revascularization. The authors conclude that the incidence of postoperative ischemic events were related more to the severity of moyamoya disease and the type of surgical procedure than to other factors, including anesthetic management. ⋯ Although preventing stroke is the major concern for patients with moyamoya disease, risk factors for perioperative cerebral ischemia have not been clarified. We retrospectively analyzed the perioperative course in 368 cases with this disease and found that the severity of the disease and type of surgical procedure were major determinants of postoperative cerebral ischemia.
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Anesthesia and analgesia · Nov 1997
Clinical TrialPostoperative pharmacokinetics and sympatholytic effects of dexmedetomidine.
Dexmedetomidine is a selective alpha2-adrenoceptor agonist with centrally mediated sympatholytic, sedative, and analgesic effects. This study evaluated: 1) pharmacokinetics of dexmedetomidine in plasma and cerebrospinal fluid (CSF) in surgical patients; 2) precision of a computer-controlled infusion protocol (CCIP) for dexmedetomidine during the immediate postoperative period; and 3) dexmedetomidine's sympatholytic effects during that period. Dexmedetomidine was infused postoperatively by CCIP for 60 min to eight women, targeting a plasma concentration (Cp) of 600 pg/mL. Before, during, and after infusion, blood was sampled to determine plasma concentrations of norepinephrine, epinephrine, and dexmedetomidine, and CSF was sampled to determine dexmedetomidine concentrations (C[CSF]). Heart rate and arterial blood pressure were measured continuously from 5 min before until 3 h after the end of infusion. During the infusion, Cp values generally exceeded the target value: median percent error averaged 21% and ranged from -2% to 74%; median absolute percent error averaged 23% and ranged from 4% to 74%. After infusion, C(CSF) was 4% +/- 1% of Cp. Because C(CSF) barely exceeded the assay's limit of quantitation, CSF pharmacokinetics were not determined. During the infusion, norepinephrine decreased from 2.1 +/- 0.8 to 0.7 +/- 0.3 nmol/L; epinephrine decreased from 0.7 +/- 0.5 to 0.2 +/- 0.2 nmol/L; heart rate decreased from 76 +/- 15 to 64 +/- 11 bpm; and systolic blood pressure decreased from 158 +/- 23 to 140 +/- 23 mm Hg. We conclude that infusion of dexmedetomidine by CCIP using published pharmacokinetic parameters overshoots target dexmedetomidine concentrations during the early postoperative period. Hemodynamic and catecholamine results suggest that dexmedetomidine attenuates sympathetic activity during the immediate postoperative period. ⋯ We studied the pharmacokinetic and sympatholytic effects of dexmedetomidine during the immediate postoperative period and found that during this period, the published pharmacokinetic data slightly overshoot target plasma dexmedetomidine concentrations. We also found that heart rate, blood pressure, and plasma catecholamine concentrations decrease during dexmedetomidine infusion.
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Anesthesia and analgesia · Nov 1997
A microscopic analysis of cut-bevel versus pencil-point spinal needles.
An in vitro examination of 25-gauge Quincke and 25-gauge and 27-gauge Whitacre spinal needles was performed after insertion in 210 consenting adult patients. In addition, 300 unused Quincke needles and 300 unused pencil-point needles were examined under a dissecting microscope. When the microscopic evaluation was performed on the needles after spinal blockade, burrs or blunting of the needle tip were noted in 24% of the Quincke needles compared with only 3% of the 25-gauge Whitacre needles and 10% of the 27-gauge Whitacre (P < 0.05). Bony contact with 25-gauge Quincke and 27-gauge Whitacre needles resulted in an increased incidence of microscopic tip damage (versus 25-gauge Whitacre). Needle-tip damage with the Whitacre needles was limited to blunting of the tip. The analysis of unused needles revealed significant differences among manufacturers of the cut-bevel needles with respect to stylet-to-needle length and burrs on the end of the stylet. The leading edge of the stylet protruded beyond the opening of the needle tip in 7% of the Quincke needles. However, only minor needle-tip abnormalities were noted with the pencil-point needles (i.e., variability in the side-port opening to needle tip distance, side-port opening integrity). In conclusion, bony contact produced more damage to the cut-bevel than to the pencil-point needle tips. In addition, fewer inherent manufacturing defects were noted with the pencil-point versus cut-bevel needles. ⋯ It has been suggested that damaged needle tips may contribute to a higher incidence of headaches after spinal anesthesia. A microscopic examination revealed that the pencil-point (versus cut-bevel) needles had fewer manufacturing flaws and were less susceptible to tip damage when bony contact occurred during the placement of the spinal needle.
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Anesthesia and analgesia · Nov 1997
Effects of inhaled nonimmobilizer, proconvulsant compounds on desflurane minimum alveolar anesthetic concentration in rats.
Anesthetics depress the central nervous system, whereas nonimmobilizers (previously called nonanesthetics) and transitional compounds having the same physical properties (e.g., solubility in lipid) do not produce anesthesia (nonimmobilizers) or are less potent anesthetics than might be predicted from their lipophilicity (transitional compounds). Potential explanations for the absent or decreased anesthetic effect of nonimmobilizer and transitional compounds include the theories that the nonimmobilizers are devoid of anesthetic effect and that transitional compounds have a decreased capacity to produce anesthesia; that the effects of these compounds are not apparent because the concentrations examined are too low; or that anesthesia, or lack thereof, results from a balance between depression and excitation (all nonimmobilizer and transitional compounds produce convulsions). To examine these issues further, we tested the effect of various multiples of the convulsive 50% effective dose (ED50) of three nonimmobilizers and one transitional compound on the minimum alveolar anesthetic concentration (MAC) of desflurane in rats. The nonimmobilizer 2,3-dichlorooctafluorobutane (NI-1), from 0.7 to 1.1 times its convulsive ED50, increased the MAC of desflurane by 14%-27%, but at 1.6 times its convulsive ED50 caused no change in MAC; the nonimmobilizer 1,2-dichlorohexafluorocyclobutane (NI-2) did not change MAC at concentrations up to its convulsant ED50, but it increased MAC by 25% and 36% at 1.3 and 1.7 times its convulsant ED50, respectively. The nonimmobilizer flurothyl (NI-3) decreased the MAC of desflurane by 20% +/- 6% (mean +/- SD) at 0.5 times its convulsant ED50, but it caused no change at higher partial pressures (up to 7.8 times its convulsant ED50), and the transitional compound CF3CCl2-O-CF2Cl (T-1) significantly decreased MAC by 16% +/- 7% at 0.8 times its convulsant ED50, but the 6%-8% decreases in MAC at 0.4 and 1.6 times its convulsant ED50 were not significant. Thus, neither nonimmobilizer nor transitional compounds produced a consistent dose-related effect on the MAC of desflurane, and any changes were small. These results suggest that the excitation produced by transitional compounds or nonimmobilizers does not explain their limited ability or inability to produce anesthesia. The data are consistent with a decreased anesthetic efficacy of transitional compounds and the lack of efficacy of nonimmobilizers. ⋯ Inhaled compounds that do not cause anesthesia (nonimmobilizers) are used to test theories of anesthetic action. Their use presumes that a trivial explanation, such as cancelling stimulatory and depressant effects, does not explain the absence of anesthesia. The present results argue against such an explanation.