Intraoperative monitoring.

This article discusses some of the routine as well as more specialized monitoring devices available. In thoracic surgery monitoring may be even more challenging because the surgery itself may involve manipulation of the airways, the pulmonary as well as cardiovascular systems. The anesthesiologist must have a full understanding of the required monitoring devices and decide which if any special techniques are needed depending on the surgical procedure and the patient's preoperative condition.

The effects of endobronchial cuff inflation on double-lumen endobronchial tube movement after lateral decubitus positioning.

OBJECT: This study was designed to measure changes in tracheal and bronchial lumen distances from mainstem and secondary carina with lateral positioning, and to assess whether inflation of the endobronchial cuff before lateral positioning would further secure a double-lumen endobronchial tube (DLT) and reduce movement. DESIGN: Prospective study. SETTING: University-affiliated cancer center. PARTICIPANTS: Fifty adult patients scheduled for elective thoracic surgical procedures requiring the placement of a left DLT. INTERVENTIONS: Patients were sequentially assigned to either the endobronchial cuff-inflated group or the deflated group during lateral positioning. After induction of general anesthesia, a left polyvinylchloride (PVC) DLT was placed and the position confirmed. In the supine position, the distance from the tip of the tracheal lumen to main carina was measured using a fiberoptic bronchoscope (FOB) passed through the tracheal lumen, and the distance from the bronchial lumen to secondary carina was measured with the FOB passed through the bronchial lumen. The patients were then positioned laterally and a second set of measurements taken. Overall movement was determined by increases and decreases in tracheal and bronchial distances obtained by substracting supine values from lateral values. MEASUREMENTS AND MAIN RESULTS: There was significant tracheal movement in 40 of 50 patients, with a mean of 0.92 +/- 1.0 cm. This was predominantly in the upward direction, as seen in 35 of 50 patients. There was significant bronchial movement in 37 of 50 patients, with a mean of 0.92 +/- 1.15 cm. Also, predominance in the upward direction was seen in 34 of 50 patients. CONCLUSIONS: DLTs move with lateral positioning, regardless of endobronchial cuff inflation. The movement is predominantly in the upward direction. Therefore, fiberoptic visualization in the supine position should be used only to confirm that the endobronchial lumen is placed on the appropriate side and the cuff is at least 1 cm inside the left mainstem bronchus. Final positioning should always be verified in the lateral position.

A clinical evaluation of pulse oximetry during thoracic surgery.

To evaluate the utility of pulse oximetry for monitoring oxygenation during thoracic surgery, pulse oximeter oxygen saturation (SpO2) values from the Nellcor N-100 (Nellcor Inc, Haywood, CA) and Novametrix model 500 (Medical Systems Inc, Wallingford, CT) were compared with simultaneous arterial saturation values (SaO2) in 20 patients. A total of 255 matched observations were recorded, and the data were divided for statistical analysis into preinduction of anesthesia and postinduction groups. The preinduction group showed a good correlation between SpO2 and SaO2 values, with both pulse oximeters consistently overestimating the SaO2. However, once anesthesia was induced, there was no longer any correlation for either of the pulse oximeters versus simultaneous SaO2 values, although on average, the SpO2 values were significantly higher than the corresponding SaO2 values. It was concluded that pulse oximetry is useful in following trends of oxygenation in patients with preexisting lung pathology undergoing thoracic surgery, but it cannot replace arterial blood gas sampling for the intraoperative management of respiratory function.

Awareness and general anaesthesia.

A state exists after the induction of anaesthesia in which patients may be aware of their surroundings yet unable to communicate. This problem of awareness and recall during general anaesthesia is a recent one in the relatively short history of anaesthesia. Prior to the introduction of muscle relaxants in 1942 by Griffith and Johnson, it was felt that "light anaesthesia" would be signified by violent movements. Today, the concepts of anaesthetic depth, awareness, and recall have become more complicated with the addition of numerous newer, shorter-acting, intravenous anaesthetic agents with varying effects on the conscious state. Several methods have been described to detect awareness. None has yet been found to be totally reliable and numerous reports of awareness can be found in the literature. Light inhalation and total intravenous anaesthesia have been blamed for the majority of these case reports. However, awareness during total intravenous anaesthesia is avoidable with the proper use of a combination of a hypnotic and an analgesic such as midazolam and alfentanil for general anaesthesia.