Anesthesiology
-
One possible mechanism of impaired oxygenation in cardiac surgery with extracorporeal circulation (ECC) is the accumulation of extravascular lung water (EVLW). Intrathoracic blood volume (ITBV) and pulmonary blood volume (PBV) also may increase after separation from ECC, which can influence both cardiac performance and pulmonary capillary fluid filtration. This study tested whether there were any relationships between lung fluid accumulation and pulmonary gas exchange during the perioperative period of cardiac surgery and ECC. ⋯ Cardiac surgery with the use of ECC induces alterations of thoracic intravascular and extravascular fluid volumes. Postoperatively, increased ITBV and PBV need not be associated with higher EVLW. Thus, sufficient mechanisms protecting against lung edema formation or providing resolution of EVLW probably are maintained after ECC. Since oxygenation is impaired during and after cardiac surgery, it is concluded that mechanisms other than or in addition to changes of ITBV, PBV, and EVLW predominantly influence gas exchange.
-
The newly developed neuromuscular blocking agent, mivacurium, has been evaluated in adults and children, but there are no data on its effects in infants. This study was designed to evaluate the neuromuscular effects of mivacurium by dose-response analysis, and its cardiovascular effects in 90 infants 2-11 months of age anesthetized with 1% halothane and nitrous oxide:oxygen. ⋯ The ED50 duration of action and infusion requirements of mivacurium in infants 2-6 months of age are comparable with those of infants 7-11 months of age.
-
Previous studies have shown that desflurane and isoflurane produce similar hemodynamic actions. This investigation examined the cardiovascular effects of desflurane and isoflurane in the presence or absence of dexmedetomidine, a highly selective alpha 2-adrenergic agonist that may be clinically useful as a premedicant or anesthetic adjuvant. ⋯ The results indicate that the cardiovascular actions of desflurane or isoflurane are similar in the absence or presence of dexmedetomidine; however, some differences between anesthetic groups were noted. In the presence of dexmedetomidine, systemic vascular resistance during desflurane anesthesia was higher when compared with that during isoflurane anesthesia, indicating that desflurane produces less pronounced direct effects on peripheral vascular tone. The concomitant greater reductions in cardiac output are consistent with greater impedance to left ventricular outflow in desflurane-anesthetized dogs pretreated with dexmedetomidine, because no differences in contractile function were observed between volatile anesthetics. In contrast, cardiac output during isoflurane anesthesia after pretreatment with oral dexmedetomidine is better maintained secondary to the peripheral vasodilator actions of this agent.
-
Cardioplegia is used to protect the myocardium from ischemic injury during open-heart surgery. However, the delivery of cardioplegic solutions may be impaired by anatomic and/or functional conditions, such as the development of transient aortic regurgitation during antegrade administration of cardioplegia or shunting through a foramen ovale during retrograde administration. In this study, the authors used a new method of cardioplegia administration, based on intraoperative contrast echocardiography, to detect on-line causes of inadequate cardioplegia delivery. ⋯ This study shows that incomplete myocardial distribution of cardioplegia, secondary to transient aortic valve incompetence or shunting through the foramen ovale, is not uncommon in patients undergoing coronary surgery.
-
There has been little systematic examination concerning the comparative effects of the anesthetized versus the awake state on outcome from cerebral ischemia. This experiment evaluated infarct volume and neurologic function in rats subjected to temporary focal ischemia while anesthetized with either sevoflurane or halothane. Outcome in these animals was compared to that observed in rats maintained unanesthetized during a similar ischemic insult. ⋯ Both halothane and sevoflurane substantially reduced damage in this focal ischemia model when compared to outcome resulting from the same insult induced in awake rats. The reduction in intraischemic mean arterial pressure caused by the anesthetics did not seem contributory to outcome. Brain temperature differences among the groups were not defined. Because small differences in pericranial temperature were shown to have major effects on outcome, further work is required to determine if differences in brain temperature explain the observed protective effects of these anesthetics.