Anesthesia and analgesia
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Anesthesia and analgesia · May 2001
Plasma tranexamic acid concentrations during cardiopulmonary bypass.
Although tranexamic acid is used to reduce bleeding after cardiac surgery, there is large variation in the recommended dose, and few studies of plasma concentrations of the drug during cardiopulmonary bypass (CPB) have been performed. The plasma tranexamic acid concentration reported to inhibit fibrinolysis in vitro is 10 microg/mL. Twenty-one patients received an initial dose of 10 mg/kg given over 20 min followed by an infusion of 1 mg. kg(-1). h(-1) via a central venous catheter. Two patients were removed from the study secondary to protocol violation. Perioperative plasma tranexamic acid concentrations were measured with high-performance liquid chromatography. Plasma tranexamic acid concentrations (microg/mL; mean +/- SD [95% confidence interval]) were 37.4 +/- 16.9 (45.5, 29.3) after bolus, 27.6 +/- 7.9 (31.4, 23.8) after 5 min on CPB, 31.4 +/- 12.1 (37.2, 25.6) after 30 min on CPB, 29.2 +/- 9.0 (34.6, 23.8) after 60 min on CPB, 25.6 +/- 18.6 (35.1, 16.1) at discontinuation of tranexamic acid infusion, and 17.7 +/- 13.1 (24.1, 11.1) 1 h after discontinuation of tranexamic acid infusion. Four patients with renal insufficiency had increased concentrations of tranexamic acid at discontinuation of the drug. Repeated-measures analysis revealed a significant main effect of abnormal creatinine concentration (P = 0.02) and time (P < 0.001) on plasma tranexamic acid concentration and a significant time x creatinine concentration interaction (P < 0.001). ⋯ A 10 mg/kg initial dose of tranexamic acid followed by an infusion of 1 mg.kg(-1).h(-1)produced plasma concentrations throughout the cardiopulmonary bypass period sufficient to inhibit fibrinolysis in vitro. The dosing of tranexamic acid may require adjustment for renal insufficiency.
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Anesthesia and analgesia · May 2001
Clinical TrialContinuous fascia iliaca compartment block in children: a prospective evaluation of plasma bupivacaine concentrations, pain scores, and side effects.
We sought to determine the plasma concentrations of bupivacaine and its main metabolite after continuous fascia iliaca compartment (FIC) block in children. Twenty children (9.9 +/- 4 yr, 38 +/- 19 kg) received a continuous FIC block for either postoperative analgesia (n = 16) or femoral shaft fracture (n = 4). A bolus dose of 0.25% bupivacaine (1.56 +/- 0.3 mg/kg) with epinephrine was followed by a continuous administration of 0.1% bupivacaine (0.135 +/- 0.03 mg. kg(-)(1). h(-)(1)) for 48 h. Plasma bupivacaine levels were determined at 24 h and 48 h by using gas liquid chromatography. Heart rate, arterial blood pressure, respiratory rate, side effects, and pain scores were recorded at 4-h intervals during 48 h. No significant differences were found between mean plasma bupivacaine levels at 24 h (0.71 +/- 0.4 microg/mL) and at 48 h (0.84 +/- 0.4 microg/mL) (P = 0.33). FIC block provided adequate analgesia in most cases. No severe adverse effects were noted. We conclude that the bupivacaine plasma concentrations during continuous FIC block in children are within the safety margins. FIC block is well tolerated, and provides satisfactory pain relief in most cases. ⋯ In this study, we have shown that, in children, continuous fascia iliaca compartment block, a technique providing neural blockade of the thigh and the anterior part of the knee, was associated with safe plasma bupivacaine concentrations, was well tolerated, and provided satisfactory pain scores in most cases.
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Anesthesia and analgesia · May 2001
Comparative StudyThe disposition of the cervical spine and deformation of available cord space with conventional- and balloon laryngoscopy-guided laryngeal intubation: a comparative study.
Orotracheal intubation causes cervical spine (C-spine) extension and potential (hypothetical) space available for the cord (SAC)-deformation. In the present study, we determined and compared the changes induced by conventional- and balloon laryngoscopy-guided orolaryngeal intubation in the upper C-spine's osseous unit-orientation, segmental angulation, segmental SAC-sagittal surface areas (SSAs), segmental/total posterior SAC-aspect, and segmental SAC-width. Eight healthy volunteers were enrolled. A set of neutral head position (baseline)- and two sets of intubation-lateral C-spine radiographs were obtained. Relative to baseline, both intubation techniques induced significant changes in the occiput (OCC)-, third cervical vertebra (C3)-, C4-, and C5-orientation, the OCC-C1-segmental angulation, all the segmental SAC-SSAs, and the OCC-C1-, and C1-2-posterior SAC-aspect (P < 0.05 to < 0.001); conventional intubation caused additional significant changes in C2-orientation, total (OCC through C5)-posterior SAC-aspect, and OCC-C1-SAC-width (P < 0.05 to < 0.001). Relative to conventional intubation, balloon-assisted intubation caused less change in C3-orientation and C2-3-SAC-width (P < 0.05), and less reduction in OCC-C1-, C1-2-, and C4-5-SAC-SSAs (P < 0.05 to < 0.01). Orotracheal intubation should be cautiously performed in patients with space-occupying upper-C-spine-SAC lesions, even if there is no concomitant osseous/ligamentous pathology. In such cases, balloon laryngoscopy may be chosen over the conventional technique, because it causes less SAC deformation. ⋯ This study shows that direct laryngoscopy-guided orotracheal intubation causes deformation of the upper cervical space available for the cord, even in the absence of cervical spine instability. These effects are attenuated with balloon laryngoscopy, and thus, its use is recommended in patients with space-occupying lesions within the spinal canal.
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Anesthesia and analgesia · May 2001
Comparative StudyThe detection of interatrial flow patency in awake and anesthetized patients: a comparative study using transnasal transesophageal echocardiography.
The Valsalva maneuver in the awake patient and the ventilation maneuver in the tracheally intubated anesthetized patient are two provocation methods to detect a patent foramen ovale (PFO) by means of contrast transesophageal echocardiography. In 60 patients undergoing posterior fossa surgery, a contrast agent was administered via a peripheral vein during a Valsalva maneuver immediately before anesthesia induction, followed by central venous administration during a ventilation maneuver in the same patients when anesthetized and endotracheally intubated. We evaluated both maneuvers with a 32-element monoplane transnasal transesophageal echocardiography probe to trace the atrial flow of the contrast agent in a 90 degrees bicaval view. A maneuver was rated positive when more than four bubbles appeared in the left atrium during the first three cardiac cycles after intrathoracic pressure release. The right atrial cross-sectional area before pressure release, and the peak septal excursion during atrial contrast opacification, were measured. McNemar's test was used to assess a paired dichotomous response on the two maneuvers for a significant difference. In 56 patients, the ventilation maneuver was significantly (P < 0.037) more often positive for PFO (n = 14) than the Valsalva maneuver (n = 7). Although there was no difference in the methods regarding the peak septal excursion, the mean right atrial area before pressure release was significantly smaller during the ventilation maneuver than during the Valsalva maneuver (11.2 +/- 3.1 cm(2) vs 14.4 +/- 3.3 cm(2), n = 42, P < 0.05). In the patients with a positive ventilation, but a negative Valsalva maneuver, the discrepancy was even larger (10.9 +/- 4.4 cm(2) vs 16.3 +/- 4.2 cm(2), n = 7, P < 0.001). We conclude that the ventilation maneuver is superior to the Valsalva maneuver in detecting PFO. Our data suggest that a peak pressure of 30 cm H(2)O during the ventilation maneuver achieves a more pronounced reduction in right atrial load and allows right atrial pressure to exceed left atrial pressure when intrathoracic pressure is released. ⋯ A controlled ventilation maneuver in anesthetized patients immediately before posterior fossa surgery may be superior to the preoperative Valsalva maneuver in detecting a patent foramen ovale by contrast transesophageal echocardiography. This approach identifies patients at high risk for paradoxic embolism, but it is not practical for preoperative identification of patients who might benefit from patent foramen ovale closure before surgery.
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Anesthesia and analgesia · May 2001
Can initial distribution volume of glucose predict hypovolemic hypotension after radical surgery for esophageal cancer?
We recently reported that the initial distribution volume of glucose (IDVG) reliably measures the central extracellular fluid volume in the presence or absence of fluid gain or loss. We examined which variables, including IDVG, can predict subsequent hypovolemic hypotension produced by the continuous shift of the extracellular fluid from the central to the peripheral compartment early after radical surgery for esophageal cancer. IDVG and plasma volume were calculated after measuring cardiac index (CI), central venous pressure, and pulmonary artery wedge pressure immediately after admission to the intensive care unit. Intraoperative fluid balance and urine volume were also recorded. Postoperative hypovolemic hypotension was clinically defined as systolic blood pressure < 80 mm Hg responsive to IV fluid administration. Either IDVG < 105 mL/kg or CI < 3.4 L. min(-1). m(-2) was associated with subsequent hypovolemic hypotension (P = 0.002 for the former and P = 0.00 03 for the latter), while remaining variables were not. IDVG and CI were well correlated (r = 0.8 7, n = 25, P = 0.0001). Our results suggest that IDVG can help predict the subsequent hypovolemic hypotension early after radical surgery for esophageal cancer. ⋯ Routine cardiovascular variables immediately after major surgery cannot predict the subsequent hypovolemic hypotension produced by the shift of the extracellular fluid. Glucose dilution using glucose 5 g and a one-compartment model can predict it simply and rapidly.