Anesthesia and analgesia
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Anesthesia and analgesia · Dec 1997
The effects of sevoflurane on cerebral hemodynamics during propofol anesthesia.
We investigated the cerebral hemodynamic effects of 0.5 and 1.5 minimum alveolar anesthetic concentration (MAC) sevoflurane during propofol anesthesia in 10 patients undergoing supratentorial tumor resection. All patients received a standardized anesthetic, and their lungs were ventilated with a mixture of air and oxygen to produce mild hypocapnia. Anesthesia was then maintained with a propofol infusion. Muscle relaxation was obtained by infusion of atracurium. A transcranial Doppler probe was used to measure red cell flow velocity in the right middle cerebral artery (Vmca). A right-sided jugular bulb catheter was inserted for sampling of jugular bulb blood. After a 30-min period of stabilization and before the start of surgery, baseline arterial and jugular bulb blood samples were drawn to define the arterial-venous oxygen content difference (AVDO2). Mean arterial pressure and Vmca were recorded. Sevoflurane (0.5 and 1.5 MAC) in oxygen/air was then administered, and all measurements were repeated. Administration of sevoflurane at 0.5 MAC did not change Vmca or AVDO2. Sevoflurane (1.5 MAC) did not change Vmca. There was an approximately 25% reduction in AVDO2 (P < 0.05). This suggests that during propofol anesthesia, although 1.5 MAC sevoflurane does not increase red blood cell velocity, there is a relative increase in flow with respect to metabolism. Administration of large-dose sevoflurane may be associated with a degree of luxury perfusion. ⋯ We investigated the cerebral hemodynamic effects of sevoflurane in patients undergoing neurosurgery. Small-dose sevoflurane (1%) did not change brain blood flow or oxygen consumption. Large-dose sevoflurane (3%) did not change flow velocity but reduced brain oxygen consumption by 25%. Sevoflurane may provide a degree of luxury perfusion.
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Anesthesia and analgesia · Dec 1997
Time-dependent changes in heart rate and pupil size during desflurane or sevoflurane anesthesia.
To better characterize alterations in autonomic function associated with prolonged anesthesia, we tested the hypothesis that the time-dependent effects of sevoflurane and desflurane differ. We studied seven male volunteers, each anesthetized for 8 h with 1.25 minimum alveolar anesthetic concentration desflurane on one study day and with 8 h sevoflurane on another. These volunteers did not undergo surgery and were minimally stimulated during the study. Measurements included blood pressure, heart rate, pupillary size and light reactivity, concentrations of serum catecholamines, and carbon dioxide production. Over time, heart rate and pupil size increased significantly. During 6 of the 14 anesthetics (45%), heart rate at some point exceeded 95 bpm; similarly, pupil size at some time exceeded 5 mm during 8 anesthetics (57%). In contrast, plasma catecholamine concentrations and carbon dioxide production remained unchanged, and blood pressure remained nearly constant. There are thus substantial time-dependent changes in autonomic functions during prolonged anesthesia, even in unstimulated, nonsurgical volunteers, but we could not detect a difference in these changes during desflurane compared with sevoflurane anesthesia. ⋯ Pupil size and heart rate changes are used to guide the delivery of anesthesia. In volunteers, pupil size and heart rate increased with increasing duration of constant desflurane or sevoflurane anesthesia. Thus, anesthetic duration alters heart rate and pupil size independent of surgery and changes in anesthetic delivery.
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Anesthesia and analgesia · Dec 1997
Comparative StudyArgon pneumoperitoneum is more dangerous than CO2 pneumoperitoneum during venous gas embolism.
We investigated the possibility of using argon, an inert gas, as a replacement for carbon dioxide (CO2). The tolerance of argon pneumoperitoneum was compared with that of CO2 pneumoperitoneum. Twenty pigs were anesthetized with enflurane 1.5%. Argon (n = 11) or CO2 (n = 9) pneumoperitoneum was created at 15 mm Hg over 20 min, and serial intravenous injections of each gas (ranging from 0.1 to 20 mL/kg) were made. Cardiorespiratory variables were measured. Transesophageal Doppler and capnographic monitoring were assessed in the detection of embolism. During argon pneumoperitoneum, there was no significant change from baseline in arterial pressure and pulmonary excretion of CO2, mean systemic arterial pressure (MAP), mean pulmonary artery pressure (PAP), or systemic and pulmonary vascular resistances, whereas CO2 pneumoperitoneum significantly increased these values (P < 0.05). During the embolic trial and from gas volumes of 2 and 0.2 mL/kg, the decrease in MAP and the increase in PAP were significantly higher with argon than with CO2 (P < 0.05). In contrast to CO2, argon pneumoperitoneum was not associated with significant changes in cardiorespiratory functions. However, argon embolism seems to be more deleterious than CO2 embolism. The possibility of using argon pneumoperitoneum during laparoscopy remains uncertain. ⋯ Laparoscopic surgery requires insufflation of gas into the peritoneal cavity. We compared the hemodynamic effects of argon, an inert gas, and carbon dioxide in a pig model of laparoscopic surgery. We conclude that argon carries a high risk factor in the case of an accidental gas embolism.
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Anesthesia and analgesia · Dec 1997
Multi-institutional survey of graduates of pediatric anesthesia fellowship: assessment of training and current professional activities.
We surveyed all the graduates of four fellowship programs in pediatric anesthesia between 1985 and 1993 to assess their current professional activities, their evaluation of fellowship training, and their opinions on future directions of such training. One-hundred ninety-one (62%) of the graduates responded. Nearly all of the respondents had sought fellowship training for pediatric anesthesia and thought that the training was worthwhile. At the time of the survey, 40% worked in a children's hospital, 72% had university or affiliate positions, and 54% had a practice that was > 50% pediatric. Those with > or = 12 mo fellowship and/or board certification in pediatrics were the most likely to have a pediatric-dedicated practice. Seventy percent of the respondents thought that fellowship training should be for 12 mo, and the proportion of respondents who recommended inclusion of training in pain management and clinical research was greater than the number who had actually received such training. Fifty-eight percent of respondents supported restriction of fellowship positions in the future, but 83% did not support a mandatory 2-yr fellowship with research training. We conclude that fellowships in pediatric anesthesia seem to be successful in providing training that is not only satisfying to the trainees, but that is also followed by active involvement in the care of children and in the training of residents and fellows in anesthesia. Additional information should be gathered to assess the impact of this training on pediatric care, to formulate a standardized curriculum, and to justify support for such training in the future. ⋯ We surveyed graduates of four fellowship programs in pediatric anesthesia (1985-1993) to assess current professional activities, fellowship training, and future directions of such training. Fellowships in pediatric anesthesia seem to provide training that is satisfying to trainees and that is followed by active involvement in the care of children.
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Anesthesia and analgesia · Dec 1997
Transdiscal lumbar sympathetic block: a new technique for a chemical sympathectomy.
Genitofemoral neuritis, which occurs when the neurolytic solution spreads into the psoas muscle, is the most common complication after neurolytic lumbar sympathetic block. We developed a transdiscal approach for neurolytic lumbar sympathetic block to reduce the danger of genitofemoral neuritis by making a sympathectomy without penetration of the psoas muscle, through which the genitofemoral nerve passes. We attempted transdiscal lumbar sympathetic block in 14 patients for whom the last previous lumbar sympathetic block performed by using the conventional paravertebral method was unsuccessful. Under fluoroscopic guidance, the needle was inserted transdiscally at L2-3 and/or L3-4 and was advanced until its tip pierced the anterior longitudinal ligament. Radiography and computed tomography revealed that the injected contrast media spread along the anterolateral surface of the vertebral column without any flow into the psoas muscle. Alcohol was injected successfully in all patients. During the 1-mo follow-up period, no patients had any symptom of genitofemoral neuritis. Thirteen patients who had been suffering from lower extremity pain achieved partial or complete pain relief. One patient with plantar hyperhidrosis achieved persistent anhidrosis. These results suggest that the transdiscal approach can be a technical option for neurolytic lumbar sympathetic block. ⋯ Neurolytic lumbar sympathetic block was performed with the needle advanced through the intervertebral disc. With this technique, the risk of genitofemoral neuritis, the most common complication after neurolytic lumbar sympathetic block, was reduced because the needle does not penetrate the psoas muscle, through which the genitofemoral nerve passes.