The Yale journal of biology and medicine
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Ocular regional anesthesia can be accomplished with either a peribulbar or retrobulbar approach. Each has advantages and disadvantages. Complications can be vision-threatening or life-threatening. Positioning the eye in neutral gaze when retrobulbar block is executed and using a needle no longer than 31 mm are effective strategies to reduce the incidence of serious complications.
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Transesophageal echocardiography offers a noninvasive technique for the continuous monitoring of cardiac performance. The combination of 2-dimensional echocardiography and Doppler velocitometry provide assessment of cardiac anatomy, valve function and, ventricular loading conditions. ⋯ Despite considerable effort to achieve this goal, a satisfactory technique has been difficult to realize. This paper discusses the role of cardiac output monitoring in perioperative care and critically examines echocardiographic techniques for cardiac output monitoring.
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The relative merits of general vs regional anesthesia for patients undergoing major vascular surgery has been the subject of debate over the past decade. Previous studies of regional vs general anesthesia often were deficient in experimental design and, therefore, did not produce definitive answers. Some of these deficiencies related to non-standardized, poorly conducted, and/or described general anesthetic techniques, nonstandardized methods of postoperative analgesia in the general anesthesia groups, and variations in preoperative cardiac status in the study groups. ⋯ The reported beneficial effects have included amelioration of the neuroendocrine stress response to surgery, improvement in pulmonary function, cardiovascular stability, enhancement of lower limb blood flow, reduction in the incidence of graft thrombosis, and a reduction in the thrombic response to surgery. Skeptics still question whether recent studies have the power to determine whether regional anesthesia decreases the incidence of cardiac and pulmonary complications following major vascular surgery. Furthermore, the issue of whether the beneficial effects of regional anesthesia on the incidence of graft thrombosis and the thrombotic response to surgery relating to intraoperative or postoperative regional anesthesia/analgesia, to regional anesthesia per se, or to the systemic effects of absorbed local anesthetics remains unresolved.
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Perioperative cardiac events continue to represent a significant cause of morbidity in patients undergoing noncardiac surgery. The evaluation of the high risk patient should begin with an assessment of the probability of coronary artery disease and exercise tolerance. Decisions to undergo further evaluation, including noninvasive testing, should be based upon the perioperative morbidity and mortality rate for the planned surgical procedure. In patients with significant coronary artery stenoses and a high probability of perioperative cardiac morbidity, coronary artery bypass grafting, percutaneous transluminal coronary angioplasty, and preoperative optimization of hemodynamics in an intensive care unit have all been advocated as means of reducing risk.
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The development of ambulatory electrocardiographic recorders and analysers and the application of transesophageal echocardiography in the mid-1980's enabled investigators to quantify and describe the occurrence of silent as well as symptomatic ischemia in the perioperative period. Several technical advances which have recently occurred in ECG monitoring include the use of miniaturized digital computing equipment to store and analyze data. In addition, real time ST-segment analysis has become widely available on multicomponent monitors in both the operating room and intensive care units. ⋯ Postoperative pain, physiological and emotional stress may all combine to cause tachycardia, hypertension, increase in cardiac output, and fluid shifts which, in high risk patients, might result in subendocardial ischemia and eventual myocardial infarction. If postoperative myocardial ischemia is the cause of late postoperative myocardial infarction in patients undergoing non-cardiac surgery, then treatment of postoperative myocardial ischemia should reduce morbidity. In addition, reducing pain and stress and avoiding postoperative hypoxemia might prevent postoperative myocardial ischemia and minimize the need for extensive preoperative cardiac evaluation.