Anesthesia and analgesia
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Anesthesia and analgesia · Jun 2004
Comparative StudyInsulin decreases isoflurane minimum alveolar anesthetic concentration in rats independently of an effect on the spinal cord.
The observation that insulin supplies an element of analgesia suggests that insulin administration might decrease the concentration of inhaled anesthetic required to produce MAC (the minimum alveolar anesthetic concentration required to eliminate movement in response to noxious stimulation in 50% of subjects). We hypothesized that insulin decreases MAC by directly affecting the nervous system, by decreasing blood glucose, or both. To test these hypotheses, we infused increasing doses of insulin either intrathecally or IV in rats anesthetized with isoflurane and determined the resulting MAC change (assessing forelimb and hindlimb movement separately). Infusion of insulin produced a dose-related decrease in MAC that did not differ among groups. That is, the IV and intrathecal infusions caused similar decreases in MAC at a given infusion rate. Blood glucose concentrations were larger in the rats given insulin with 5% dextrose. However, the percentage change in MAC determined from forelimb versus hindlimb movement did not differ. For a given insulin infusion rate, MAC changes and glucose levels did not correlate with each other, except, possibly, for the most rapid infusion rate, for which smaller glucose concentrations were associated with a marginally larger decrease in MAC. Intrathecal infusions of insulin did not produce spinal cord injury. In summary, we found that insulin decreases isoflurane MAC in a dose-related manner independently of its effects on the blood concentration of glucose. The sites at which insulin acts to decrease MAC appear to be supraspinal rather than spinal. The effect may be due to a capacity of insulin to produce analgesia through an action on one or more neurotransmitter receptors. ⋯ Intrathecal and IV insulin administration equally decrease isoflurane MAC in rats, regardless of the concentration of blood sugar. These findings indicate that although insulin decreases MAC, the decrease is not mediated by actions on the spinal cord.
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Anesthesia and analgesia · Jun 2004
Comparative StudyIncreasing the value of time reduces the lost economic opportunity of caring for surgeries of longer-than-average times.
Anesthesiology groups that provide care for surgical procedures of longer-than-average duration are economically disadvantaged by both increased staffing costs and reduced revenue. Under the current billing system, anesthesia time is valued the same regardless of the total case duration. In this study, we evaluated the effect on four academic anesthesiology departments of two hypothetical scenarios by changing the anesthesia care billing system to make more valuable either 1) all time units or 2) just second-hour and subsequent time units. From the four departments, case-specific data (anesthesia Current Procedural Terminology code and minutes of care) were collected for all anesthesia cases billed for 1 yr. Basic units were determined from the American Society of Anesthesiologists (ASA) relative value guide. The average time for each case was defined as the average anesthesia time for that specific Current Procedural Terminology code, as published by the Center for Medicare and Medicaid Services (CMS). The actual total ASA units per hour (tASA/h) was determined by adding all the basic units and time units and dividing by hours of anesthesia care (minutes of anesthesia care divided by 60). We then calculated a hypothetical CMS tASA/h for each group by substituting the CMS average time for each anesthesia procedure time for the actual time reported by each group and using 15-min time units. For each group, the Actual (Act) tASA/h and CMS tASA/h were calculated for both options-changing the interval for all time units or only for second and subsequent hours. Intervals were 15, 12, 10, 7, 6, or 5 min. When changing all time units, Act tASA/h and CMS tASA/h were never equal for all groups. The two productivity measures became approximately equal if only time units after the first hour were changed to 6- to 7-min intervals. When changes were applied only to the Act tASA/h (with CMS tASA/h remaining at 15-min intervals), at the 12-min interval either option resulted in a similar or higher Act tASA/h than CMS tASA/h. Both options increase the value of time and help compensate for the lost economic opportunity of longer-than-average surgical durations. ⋯ Longer-than-average surgical durations result in less potential revenue per hour under current billing methodology. This study quantifies the increase in billing productivity when the value of time is increased, when evaluating the billing productivity of four academic anesthesiology groups.
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Anesthesia and analgesia · Jun 2004
Case ReportsUse of continuous paravertebral analgesia to facilitate neurologic assessment and enhance recovery after thoracoabdominal aortic aneurysm repair.
Neurologic assessment after thoracic aortic aneurysm repair is important for detecting and treating late onset paraplegia. Traditional methods of pain control, such as patient-controlled IV analgesia and epidural analgesia, may interfere with neurologic assessment. We present a case of a patient who received continuous thoracic paravertebral analgesia that provided excellent analgesia while preserving the ability to monitor neurologic function. ⋯ We provided postoperative continuous paravertebral analgesia in a patient after thoracoabdominal aneurysm repair requiring postoperative neurologic assessment. Paravertebral analgesia provides unilateral analgesia with fewer neurologic and hemodynamic side effects than central neuraxial blockade and should be considered for management of patients undergoing thoracic aortic aneurysm repair.
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Anesthesia and analgesia · Jun 2004
A platelet activating factor receptor antagonist inhibits cytokine production in human whole blood by bacterial toxins and live bacteria.
We previously reported that a platelet-activating factor receptor (PAFR) antagonist (TCV-309) suppressed lipopolysaccharide (LPS)-induced mortality and tumor necrosis factor (TNF) production in mice. However, the effect of TCV-309 on cytokine production induced by Staphylococcus enterotoxin B (SEB) or live bacteria has not been reported. In this study we investigated the effect of TCV-309 on cytokine production in human whole blood induced by LPS, SEB, and both Gram-positive and -negative bacteria. Human whole blood diluted 5:1 (980 microL) was placed in the wells of a 24-well plate. Ten microliters of LPS, SEB, Escherichia coli O18 K(+), or Staphylococcus aureus were added to each well. After incubation at 37 degrees C for 6 h, TNF, interleukin (IL)-6, and IL-8 in the culture medium were measured. TCV-309 did not affect the growth of either E. coli or S. aureus bacteria in the culture medium for the 6 h incubation. LPS, SEB, and both E. coli and S. aureus induced TNF, IL-6, and IL-8 in human whole blood. TCV-309 significantly inhibited the production of TNF, IL-6, and IL-8 induced by LPS, SEB, and bacteria. A PAFR antagonist suppressed cytokine production induced by LPS, SEB, and both Gram-positive and -negative bacteria in human whole blood. A PAFR plays an important role of producing proinflammatory cytokines induced by both toxins and live bacteria. ⋯ The platelet-activating factor receptor plays an important role in producing proinflammatory cytokines induced by bacterial toxins, such as lipopolysaccharide,Staphylococcus enterotoxin B, and live Gram-positive and Gram-negative bacteria.
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Anesthesia and analgesia · Jun 2004
Enhanced vasodilatory responses to milrinone in catecholamine-precontracted small pulmonary arteries.
Beta-adrenergic agonists (e.g., epinephrine [E] and norepinephrine [NE]) and phosphodiesterase-III inhibitors (e.g., milrinone) are often used in combination to augment ventricular function in the perioperative period. In the myocardium, milrinone acts synergistically with beta-adrenergic agonists to increase contractility. However, the potential interaction between catecholamines with combined alpha- and beta-adrenergic activity and milrinone in the pulmonary circulation has not been determined. We evaluated the vasodilatory effects of milrinone and nitroglycerine on large elastic and small muscular porcine pulmonary vascular rings precontracted with catecholamines with beta-adrenergic agonist activity (E and NE), the alpha-adrenergic agonist phenylephrine, and a nonadrenergic agonist, the thromboxane analog U46619. In small pulmonary arteries, the vasorelaxation with milrinone was significantly enhanced in rings precontracted with E or NE compared with those precontracted with phenylephrine or U46619. However, in large pulmonary arteries, the vasorelaxation with milrinone was similar in all vessel rings and was not influenced by the agonist used to induce precontraction. In marked contrast, the vasorelaxant responses to nitroglycerine were not altered by the specific agonist used for precontraction in either small or large pulmonary vascular rings. Thus, the pulmonary vascular effects of milrinone are enhanced when combined with drugs with beta-adrenoreceptor agonist activity. The vasodilatory interactions exhibited by phosphodiesterase-III inhibitors and the catecholamines NE and E suggest that their combined use might be beneficial in circumstances in which ventricular dysfunction and increased pulmonary vascular resistance occur. ⋯ This study demonstrated that milrinone had enhanced vasodilator effects when combined with drugs with beta-adrenoreceptor agonist activity in small pulmonary artery segments removed from pigs.