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Application of transesophageal echocardiography to continuous intraoperative monitoring of left ventricular performance.

Transesophageal M mode echocardiography was used for continuous monitoring of left ventricular dimensions in 21 patients (11 with valvular and 10 with coronary heart disease) undergoing open heart surgery. Echocardiograms were recorded in six stages of the procedure and simultaneous measurements of cardiac output (with dye dilution) and atrial pressures were made. Measurements of left ventricular diameters with the transesophageal technique correlated excellently with the corresponding measurements obtained with the standard parasternal method. In patients with volume overload, surgical correction was accompanied by a decrease in diastolic dimension, velocity of circumferential fiber shortening, mid wall stress and end-diastolic stiffness, and an increase in cardiac output. Pericardial and chest wall closures generally caused a significant decrease in cardiac output, and correlated with a decrease in diastolic diameter and an increase in the stiffness constant of the left ventricle. Thus, the decrease in cardiac output may have been due to decreased distensibility of the ventricular cavity secondary to mechanical restriction by the pericardium and chest wall. Pericardial opening caused a significant delay in septal motion that was reversed by closing the pericardium. This study confirms the validity of transesophageal echocardiography and its usefulness in monitoring changes in ventricular function during cardiac surgery.

Adult↗

Technical aspects of intraoperative monitoring of lower cranial nerve function.

The efficacy of monitoring facial nerve activity in decreasing long-term morbidity has promoted an interest in monitoring other at-risk cranial nerves during procedures that involve manipulation of the basal cranial nerves. This presentation details practical techniques for monitoring the lower cranial nerves, which have been experientially developed over the past 9 years. Emphasis is placed on the selection of electrodes and procedural changes required for reliable and safe stimulation of the basal cranial nerves. Either paired hook-wire or tethered needle electrodes can be used for monitoring glossopharyageal, accessory, and hypoglossal nerve function. Several options for monitoring vagus nerve function are discussed. Of these, the transoral placement of paired hook-wire electrodes remains the most reliable, cost-effective, and least morbid technique. Electrical stimulation of the glossopharyngeal and vagus nerves carries the risk of unanticipated, potentially irreversible disturbances in cardiovascular function. Guidelines for type and optimal placement of stimulating electrodes and recommended intensity levels to prevent unfavorable reactions are presented.

Journal Article↗

Hypnosis for monitoring intraoperative spinal cord function.

In such procedures as the Harrington operation for idiopathic scoliosis, evaluation of spinal cord function is advisable immediately after the back is straightened. The authors have used hypnosis for this procedure, as an adjunct to anesthetic management. Patients are awakened on the table, given lower extremity tests, and are then reanesthetized. The incidence of postoperative pain and other discomfort is also reduced by hypnosis.

Adolescent↗

Use of peripheral nerve action potentials for intraoperative monitoring.

Following a physical injury to peripheral nerve, clinical evaluation and the use of conventional EMG/NCS is often unable to determine whether axons are crossing the site of injury before severe changes in distal tissues occur. The INAP recording identifies functional axons within neuromas before other signs of reinnervation have developed. In clinically complete lesions, recording an INAP across the injury indicates the presence of regenerating axons, and neurolysis of the encasing connective tissue is recommended. If an INAP is absent, resection of the dense neuroma is usually undertaken with end-to-end suture or graft. A present INAP indicates clinically significant regenerating axons even with large distances to target tissue. An absent INAP for injuries far from target tissue indicates a poor prognosis. In clinically incomplete lesions, INAP recording is of no value over the clinical examination and EMG/NCS. INAP can aid peripheral nerve tumor resection by identification of intact nerve fascicles. INAP responses are obtained by placing platinum-iridium bipolar stimulating electrodes proximal to the injury. The INAP is then recorded by distal electrodes. A standard EMG/NCS instrument with an isolated stimulation unit can be used with the appropriate gain and time base settings. Stimulus intensity required for a supramaximal response is usually less than 75 V at 0.05 msec duration. Frequency bandpass is similar to that for conventional EMG/NCS studies. Electrodes must elevate the nerve during the recording. Artifact from 60 Hz line frequency and stimulus are common problems.

Humans↗

[Intraoperative monitoring in artificial respiration of premature and newborn infants. I. Monitoring of respiratory parameters and alveolar ventilation].

Monitoring of ventilation serves to ensure adequate alveolar ventilation and arterial oxygenation, and to avoid pulmonary damage due to mechanical ventilation. Basic clinical monitoring, i.e., inspection, auscultation (including precordial or oesophageal stethoscope) and monitoring of heart rate and blood pressure, is mandatory. Mechanical ventilation is monitored by ventilation pressures (peak pressure, plateau pressure and endexpiratory pressure), ventilation volumes (measured at the in/expiratory valve of the respirator and by hot-wire anemometry at the tube connector), ventilation rate, and inspiratory oxygen concentration (FiO2). Alveolar ventilation should be continuously and indirectly recorded by capnometry (pECO2) and by measurement of transcutaneous pCO2 (tcpCO2), whereas oxygenation is determined via measurement of transcutaneous pO2 (tcpO2). Invasive monitoring of gas exchange is essential in prolonged or intrathoracic interventions as well as in neonates with cardiopulmonary problems. paCO2 may be estimated by capillary or venous blood gas analysis; arterial blood gas analysis is required for exact determination of paCO2 as well as arteriocutaneous pCO2 (atcDCO2) and arterio-end-expiratory (aEDCO2) gradients.

Acid-Base Equilibrium↗