Anesthesia and analgesia
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Anesthesia and analgesia · Dec 2002
Risk assessment of hemorrhagic complications associated with nonsteroidal antiinflammatory medications in ambulatory pain clinic patients undergoing epidural steroid injection.
We prospectively studied 1035 individuals undergoing 1214 epidural steroid injections to determine the risk of hemorrhagic complications. A history of bruising or bleeding was present in 176 (15%) patients. A platelet count was assessed in 77 patients before the epidural steroid injection; none was less than 100 x 10(9)/L. Nonsteroidal antiinflammatory drugs (NSAIDs) were reported by 383 (32%) patients, including 34 patients on multiple medications. Aspirin was the most common NSAID and was noted by 158 patients, including 104 patients on 325 mg or less per day. There were no spinal hematomas (major hemorrhagic complications). Blood was noted during needle or catheter placement in 63 (5.2%) patients (minor hemorrhagic complications). NSAIDs did not increase the frequency of minor hemorrhagic complications. However, increased age, needle gauge, needle approach, needle insertion at multiple interspaces, number of needle passes, volume of injectant, and accidental dural puncture were all significant risk factors for minor hemorrhagic complications. There were 42 patients with new neurologic symptoms or worsening of preexisting complaints that persisted more than 24 h after injection; median duration of the symptoms was 3 days (range, 1-20 days). Our results confirm those of previous studies performed in obstetric and surgical populations that document the safety of neuraxial techniques in patients receiving NSAIDs. We conclude that epidural steroid injection is safe in patients receiving aspirin-like antiplatelet medications. Minor worsening of neurologic function may occur after epidural steroid injection and must be differentiated from etiologies requiring intervention. ⋯ Previous studies performed in obstetric and surgical populations have demonstrated that antiplatelet therapy does not increase the risk of spinal hematoma associated with spinal or epidural anesthesia and analgesia. We confirm the safety of epidural steroid injection in patients receiving aspirin-like medications.
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Anesthesia and analgesia · Dec 2002
Evaluating the relationship between arterial blood pressure changes and indices of pulse oximetric plethysmography.
The finger plethysmographic waveform of pulse oximeters is a qualitative indicator of fingertip perfusion. This waveform has been used to assess the depth of anesthesia. Its cyclical changes associated with mechanical ventilation have also been used to detect changes in blood volume under normotensive conditions and has revealed that minimal normotensive hypovolemia can cause a significant increase in the delta-down component of this waveform. Hypovolemia may be associated with hypotension; the latter may be due to causes other than hypovolemia. Because the effects of the hypotension on plethysmographic waveform have not been evaluated, it may be difficult to detect hypovolemia in these conditions by inspecting a plethysmogram. Therefore, we performed this study to evaluate the effect of normovolemic hypotension on characteristics of plethysmographic waveform in 33 adult patients undergoing general anesthesia with controlled hypotension. The delta-down and ventilatory systolic variation components were increased significantly with decreases in systolic blood pressure. The result of this study shows that the effect of pharmacologic hypotension on the plethysmographic waveform of pulse oximeter is similar to that of minimal hypovolemia. Therefore, blood volume may be inaccurately assessed by the inspection of ventilatory-induced cyclical changes of pulse oximetric waveform in the presence of hypotension. ⋯ The cyclical respiratory-induced changes in the amplitude of the pulse oximeter waveform can be used to detect normotensive hypovolemia. This study shows that hypotension produces the same effect. Therefore, in hypotensive conditions, we cannot determine the presence of hypovolemia.
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Anesthesia and analgesia · Dec 2002
Development and analysis of a new certifying examination in perioperative transesophageal echocardiography.
A key element in developing a process to determine knowledge and ability in applying perioperative echocardiography has included an examination. We report on the development of a certifying examination in perioperative echocardiography. In addition, we tested the hypothesis that examination performance is related to clinical experience in echocardiography. Since 1995, more than 1200 participants have taken the examination, and more than 70% have passed. Overall examination performance was related positively to longer than 3 mo of training (or equivalent) in echocardiography and performance and interpretation of at least six examinations a week. We concluded that the certifying examination in perioperative echocardiography is a valid tool to help determine individual knowledge in perioperative echocardiography application. ⋯ This report describes the process involved in developing the certifying transesophageal echocardiography examination and identifies correlates with examination performance.
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Anesthesia and analgesia · Dec 2002
Comparative StudyBispectral index monitoring: a comparison between normal children and children with quadriplegic cerebral palsy.
We performed this study to compare the correlation of bispectral index (BIS) values with different sevoflurane concentrations between normal children and those with quadriplegic cerebral palsy with mental retardation (CPMR). Twenty children with CPMR (Group I) and 21 normal children (Group II) between 2 and 14 yr of age were studied. Anesthesia was induced and maintained with sevoflurane and 66% N(2)O/O(2). Bispectral values were recorded on an Aspect Medical Systems (Natick, MA) monitor, and sevoflurane concentrations were measured with an Ohmeda (Hanover, MA) inhaled anesthetic monitor. The BIS values were recorded after midazolam premedication; after the induction of anesthesia; at end-tidal sevoflurane concentrations of 1%, 3%, and again at 1%; and after emergence from the anesthetic. Both groups were similar in age and sex distribution, but children in Group I weighed less than those in Group II (P < 0.05). The BIS values were significantly lower in Group I compared with Group II after sedation, at 1% sevoflurane concentrations, and after emergence. No difference was observed between the two groups at anesthesia induction (8%) and at 3% sevoflurane concentration. We conclude that, in children with CPMR, BIS values exhibit a pattern of change similar to that observed in normal children. However, absolute BIS values obtained in such children are lower than those in normal children while awake and at different sevoflurane concentrations. ⋯ We compared bispectral (BIS) values with different sevoflurane concentrations between normal children and children with cerebral palsy. We observed that, in children with cerebral palsy, BIS values exhibited a similar pattern of change as is observed in normal children. However, absolute BIS values obtained in such children are lower than those in normal children while awake and at different sevoflurane concentrations.
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Anesthesia and analgesia · Dec 2002
Interactions of volatile anesthetics with cholinergic, tachykinin, and leukotriene mechanisms in isolated Guinea pig bronchial smooth muscle.
We studied relaxation of airway smooth muscle by sevoflurane, desflurane, and halothane in isolated guinea pig bronchi. Ring preparations were mounted in tissue baths filled with physiological salt solution and continuously aerated with 5% CO(2) in oxygen. Electrical field stimulation induced contractions sensitive to tetrodotoxin, indicating nerve-mediated responses. These consisted of an atropine-sensitive cholinergic phase and a nonadrenergic noncholinergic (NANC) phase sensitive to SR48968, a neurokinin-2 receptor antagonist. Anesthetics were added to the gas aerating the tissue baths. Sevoflurane and desflurane at 1.0 minimum alveolar anesthetic concentration and halothane at 1.0-2.0 minimum alveolar anesthetic concentrations inhibited both cholinergic and NANC contractions to electrical field stimulation. None of the anesthetics affected responses to exogenously applied neurokinin A, a likely mediator of NANC contractions, suggesting prejunctional inhibition of NANC neurotransmission. The anesthetics did not affect the initiation of contractile responses to leukotriene C(4) (LTC(4)), a mediator of asthmatic bronchoconstriction. However, sevoflurane and desflurane both relaxed bronchi in a steady-state contraction achieved by LTC(4). Surprisingly, halothane did not relax LTC(4) contractions. Concerning LTC(4)-elicited bronchoconstriction, sevoflurane and desflurane were more potent airway smooth muscle relaxants in vitro. ⋯ Halothane, sevoflurane, and desflurane attenuated airway smooth muscle tone via inhibition of cholinergic and nonadrenergic noncholinergic neurotransmission. Sevoflurane and desflurane reduced leukotriene C(4)-induced bronchoconstriction, whereas halothane did not. This indicates a beneficial role for sevoflurane and desflurane in asthmatics.