Anesthesia and analgesia
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Anesthesia and analgesia · Apr 2004
Randomized Controlled Trial Clinical TrialPreoperative oral dextromethorphan attenuated tourniquet-induced arterial blood pressure and heart rate increases in knee cruciate ligament reconstruction patients under general anesthesia.
The precise mechanism of tourniquet-induced arterial blood pressure increase is unknown. We determined the effect of preoperative oral dextromethorphan (DM) on arterial blood pressure and heart rate changes during tourniquet inflation in knee cruciate ligament reconstruction patients under general anesthesia. Patients in the DM group (n = 38) received oral DM 30 mg, and patients in the control group (n = 38) received oral placebo 2 h before the induction of anesthesia. Anesthesia was maintained with sevoflurane 2.0% and N(2)O in 33% oxygen, and the trachea was intubated until the end of surgery. Arterial blood pressure and heart rate were measured at 0, 30, and 60 min after the start of tourniquet inflation. Systolic arterial blood pressure and heart rate at 60 min in the control group were significantly more than those in the DM group (131.1 +/- 15.8 mm Hg versus 123.6 +/- 15.9 mm Hg [P < 0.05] and 74.1 +/- 11.3 bpm versus 67.8 +/- 8.5 bpm [P < 0.01], respectively). The percentage increase in systolic arterial blood pressure and heart rate in the DM group was also attenuated when compared with that in the control group (P < 0.05). In conclusion, preoperative oral DM 30 mg significantly attenuated arterial blood pressure and heart rate increases during tourniquet inflation under general anesthesia. ⋯ We demonstrated that preoperative oral dextromethorphan 30 mg significantly attenuated arterial blood pressure and heart rate increases at 60 min during tourniquet inflation in patients undergoing knee cruciate ligament reconstruction under general anesthesia.
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Lumbar epidural anesthesia and analgesia has gained increasing importance in perioperative pain therapy for abdominal and lower limb surgery. The loss-of-resistance technique, used to identify the epidural space, is thought to rely on the penetration of the ligamentum flavum. However, the exact morphology of the ligamentum flavum at different vertebral levels remains controversial. Therefore, in this study, we directly investigated the incidence of lumbar ligamentum flavum midline gaps in embalmed cadavers. Vertebral column specimens were obtained from 45 human cadavers. On each dissected level, ligamentum flavum midline gaps were recorded. The incidence of midline gaps per number of viable specimens at the following levels was: L1-2 = 10 of 45 (22.2%), L2-3 = 5 of 44 (11.4%), L3-4 = 5 of 45 (11.1%), L4-5 = 4 of 43 (9.3%), L5/S1 = 0 of 33 (0%). In conclusion, the present study determined the frequency of lumbar ligamentum flavum midline gaps. Gaps in the lumbar ligamentum flavum are most frequent between L1 and L2 but are more rare below this level. When using the midline approach, the ligamentum flavum may not impede entering the epidural space in all patients. ⋯ The ligamentum flavum is a crucial anatomical landmark for the safe performance of epidural anesthesia. However, the present study demonstrates some failure of the lumbar ligamentum flavum as a landmark. This may mean that, using a midline approach, one cannot always rely on the ligamentum flavum as a perceptible barrier to epidural needle advancement.
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Anesthesia and analgesia · Apr 2004
Bispectral index as an indicator of seizure inducibility in electroconvulsive therapy under thiopental anesthesia.
The prediction of seizure thresholds in electroconvulsive therapy (ECT) remains problematic. We examined the relationship between bispectral index (BIS) score and seizure duration in ECT performed under thiopental anesthesia in patients receiving their usual regimen of antidepressant medication for its potential as a predictor of seizure inducibility. One-hundred ECT treatments were evaluated in 16 adult patients diagnosed with depression. BIS scores were recorded at the preanesthetic and preictal periods and at recovery from ECT. Seizure duration was defined as the duration of the electroencephalogram seizure pattern. The relationships between preanesthetic and preictal BIS scores and seizure duration were evaluated. Effective seizure threshold was determined by receiver operator characteristic analysis, and the area under the curve (AUC) was calculated for seizure durations of more than 10 s, more than 20 s, and more than 30 s. The relationship between seizure duration and thiopental estimated effect-site and plasma concentrations was analyzed as well. Preictal BIS scores for seizures lasting longer than 30 s were significantly higher than those for seizures lasting <30 s. A preictal BIS score of 55 or more represents a strongly determinant condition for achieving seizures that last longer than 30 s (AUC, 0.937; receiver operator characteristic), as well as for briefer seizures that last more than 20 or 10 s (AUC: 0.938 and 0.959, respectively). There was no significant correlation between seizure duration and the estimated thiopental effect-site or plasma concentration. We conclude that during thiopental anesthesia, the minimum threshold for inducing seizures of any duration correlates with a preictal BIS score of 55. This threshold was independent of antidepressant regimen and thiopental dosage. We suggest that the preictal BIS score is useful in predicting the ictogenic threshold in ECT. ⋯ We found that the bispectral index (BIS) score serves as an indicator of seizure inducibility in electroconvulsive therapy (ECT) under thiopental anesthesia and that the relationship between BIS score and seizure duration was not linear, suggesting that the pharmacological mechanisms by which thiopental and propofol suppress ECT seizure activity are different.
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Anesthesia and analgesia · Apr 2004
The antiinflammatory effects of ketamine in endotoxemic rats during moderate and mild hypothermia.
Endotoxemia is a common problem among critically-ill patients. We previously found that ketamine inhibited hypotension, metabolic acidosis, and increase of plasma cytokines during endotoxemia in rats. Although endotoxic patients often develop hypothermia, it has not been determined whether ketamine retains its antiinflammatory effects during hypothermia. We investigated the effects of ketamine on endotoxemic rats subjected to moderate and mild hypothermia. Male Wistar rats (n = 100) were anesthetized intraperitoneally with pentobarbital sodium and assigned to one of two protocols: one representing moderate hypothermia (30 degrees C-32 degrees C) and the other, mild hypothermia (33 degrees C-35 degrees C). Each protocol included 5 equal groups: 1). Escherichia coli endotoxin (15 mg/kg IV) in normothermia, 2). ketamine (10 mg x kg(-1) x h(-1) IV) during and after endotoxin injection in normothermia, 3). saline in hypothermia, 4). endotoxin (15 mg/kg IV) in hypothermia, and 5) ketamine (10 mg x kg(-1) x h(-1) IV) in hypothermia after endotoxin injection. Rats were then warmed or cooled to maintain rectal temperatures as above for 6 h. We assessed hemodynamics, acid-base status, and plasma concentrations of tumor necrosis factor-alpha, and interleukin-6. Endotoxemic rats developed hypotension and metabolic acidosis as well as increased plasma cytokine concentrations. At 6 h after endotoxin injection, the mean systolic arterial blood pressure decreased by 71% in the saline/normothermia/endotoxin group, whereas it decreased by only 6%, 41%, and 29% in the ketamine/normothermia/endotoxin, saline/moderate hypothermia/endotoxin, and ketamine/moderate hypothermia/endotoxin groups, respectively. Ketamine administration to endotoxemic rats with hypothermia, whether moderate or mild, also attenuated hypotension, metabolic acidosis, and cytokine increase, but these effects were not superior to those of hypothermia alone. Our findings suggest that, during hypothermia, ketamine administration may not have additive beneficial antiinflammatory effects. ⋯ Although ketamine administration decreased the severity of hypotension and acidosis in endotoxemic rats, ketamine administration may not have additive beneficial antiinflammatory effects during hypothermia.
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Anesthesia and analgesia · Apr 2004
Case ReportsProfound hypoxemia resulting from shunting across an inadvertent atrial septal tear after left ventricular assist device placement.
Defects within the interatrial septum (IAS) can be a source of significant right-to-left shunting and hypoxemia, particularly after placement of a left ventricular assist device (LVAD). We report a case of LVAD placement in which an unrecognized IAS tear occurred intraoperatively, leading to profound arterial desaturation. Transesophageal echocardiography (TEE) was instrumental in making the diagnosis. Certain intraoperative events increased the pressure gradient between the right and left atria, aggravating hypoxemia. We recommend that patients undergoing LVAD placement be screened intraoperatively with TEE for unrecognized IAS defects. Re-examination of the IAS should occur on weaning from cardiopulmonary bypass. ⋯ A traumatic atrial septal defect after atrial cannulation caused a right-to-left intracardiac shunt on initiation of left ventricular assist device support that was further aggravated by chest closure and pleural suction, culminating in severe hypoxemia.