Anesthesia and analgesia
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Anesthesia and analgesia · Nov 1997
Clinical TrialThe effect of age on retrieval of local anesthetic solution from the epidural space.
We conducted this prospective study to determine whether advancing age is correlated with retrieval of local anesthetic solution from the epidural space. Three hundred forty-six patients (ASA physical status I or II, 20-93 yrs of age, 177 female and 169 male patients) undergoing epidural anesthesia were enrolled. The epidural space was identified by a loss of resistance technique using air, and a catheter was introduced 3 cm. Three milliliters of 2% lidocaine with epinephrine was injected as a study dose by hand at a rate of 1 mL/s with the patient in the supine position. The syringe was immediately aspirated to retrieve the local anesthetic solution. A retrieved volume of 0.5 mL or more with a glucose concentration less than 6 mg/dL was defined as retrieval positive, and a volume of less than 0.5 mL was defined as retrieval negative. There was a significant correlation between age and retrieval volume among all the patients (Y = 0.008X-0.222, P < 0.0001) with a significant increase in the positive retrieval incidence and volume from the patients in their 50s (11%, 0.6 +/- 0.3 mL) to the patients in their 60s (26%, 1.0 +/- 0.6 mL) (P < 0.05 for both). The incidence of positive retrieval and the retrieval volume were greater in the patients in their 60s and older (30%, 1.1 +/- 0.63 mL) than in the younger than 60 (10%, 0.6 +/- 0.3 mL) (P < 0.0001 and P < 0.001). The glucose concentration was 2.3 +/- 1.2 mg/dL in the positive cases. We conclude that there is a weak positive correlation between age and the local anesthetic solution retrieved from the epidural space. ⋯ We conducted a study in 346 patients to determine whether advancing age could be correlated with retrieval of local anesthetic solution from the epidural space. We found a weak positive correlation between advanced age and the amount of solution retrievable from the epidural space. Further studies are required to determine whether this phenomenon may call for dose adjustments in patients aged more than 60 yrs.
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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
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
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.