5 Anaesthesia for thoracic surgery

5 Anaesthesia for thoracic surgery BRIAN R KAVANAGH A L A N N. S A N D L E R Anaesthesia for thoracic, as opposed to cardiac, surgery is becoming increasingly refined and identified as an independent specialty. This is reflected in the number of published textbooks focusing on thoracic anaesthesia (Marshall et al, 1987; Kaplan, 1992; Benumof, 1995) and also by the new development of highly technical thoracic procedures. This chapter briefly reviews the critical issues of importance to practising anaesthetists who are involved in thoracic surgery and outlines some of the recent developments in the field. PERSPECTIVE The role of thoracic anaesthesia became apparent in the 1930s when thoracotomy had become relatively safe and was being increasingly practised. The anaesthetic management of patients undergoing lobectomy was reported in 1930 and again in 1936, when the number had increased to 128 (Magill, 1936). Surprisingly low hospital mortality rates were also recorded by Beecher (1940). Reliable airway control with endotracheal intubation and positive pressure ventilation were the major factors responsible for the development of general anaesthesia for thoracotomy. To facilitate separation of the lungs, large-bore endotracheal tubes and bronchial blockers were developed (Rowbotham, 1926). Later, specific double-lumen tubes (DLTs) for selective endobronchial intubation were introduced. Safe modem inhalational anaesthetics and muscle relaxants were also developed. Finally, sophisticated intensive cardiorespiratory monitoring, in conjunction with effective postoperative analgesic techniques, permitted the highly developed anaesthetic care of thoracic patients with marginal cardiopulmonary status. The future care of these patients will centre around the provision of cost-effective anaesthesia and post-operative analgesia for all patients, in addition to the increasing refinement of anaesthetic skill, agents and monitoring techniques. P R E - O P E R A T I V E EVALUATION Pre-operative evaluation for thoracic surgery is focused on three principal questions. First, is the disease resectable? This information is obtained from BailliOre's Clinical Anaesthesiology77 Vol, I0, No. 1, April 1996 ISBN 0-7020-2099~0 0950-3501/96/010077 + 22 $12.00/00

Copyright © 1996, by Bailli~re Tindall All rights of reproduction in any form reserved

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appropriate staging of the disease, in the case of malignancy, and ensures that the planned surgical procedure can be satisfactorily completed from the technical standpoint. Second, does the patient have sufficient physiological reserve to undergo major surgery? This issue refers to assessment with respect to cardiorespiratory fitness for general anaesthesia and routine airway assessment. In general, if coronary artery bypass grafting is necessary to optimize a patient, this should be performed before pulmonary resection, although both procedures have been performed under the same anaesthetic (Dalton et al, 1978; Piehler et al, 1985). Third, for patients in whom pulmonary resection is planned, does the predicted post-operative pulmonary function suggest that the likelihood of post-operative respiratory failure is acceptably low? The pre-operative evaluation centres on a good history, physical examination and appropriate laboratory investigation. A history of dyspnoea suggests that the patient's ventilatory requirements are increased. Dyspnoea may have a pulmonary or a cardiac basis. Left ventricular failure as a cause of dyspnoea suggests a greatly increased cardiac risk and has significant implications for intra-operative monitoring. Severe exertional dyspnoea suggests markedly impaired pulmonary reserve and the potential requirement for post-operative mechanical ventilation. The presence of wheezing, cough or sputum may suggest asthma or chronic bronchitis, with concomitant impaired gas exchange, airway hyperreactivity and mucus production. A history of tobacco use should further increase the suspicion of chronic bronchitis. Haemoptysis is usually only a problem when it occurs in large quantities, making airway management and lung separation difficult. Chest pain may be present in up to 40% of patients with carcinoma of the lung. It should be differentiated from angina pectoris, pleuritic pain and reflux oesophagitis. For patients with intra-thoracic malignancies, additional symptoms may be present related to local invasion of tumour, metastatic tumour spread and paraneoplastic syndromes. Pleural effusion, chest wall pain, oesophageal obstruction, lobar atelectasis, superior vena caval obstruction, brachial plexus invasion, Homer's syndrome and recurrent laryngeal nerve invasion are all potential manifestations of local invasion. Metastatic spread may involve any organ system, and paraneoplastic syndromes include ectopic adrenocorticotrophic hormone (ACTH) or anti-diuretic hormone (ADH) hypersecretion, carcinoid syndrome, hypercalcaemia, proximal myopathy related to dermatomyositis, and a myasthenic syndrome (Eaton-Lambert syndrome). Routine laboratory tests may disclose information pertinent to the thoracic surgical patient. Polycythaemia and leukocytosis may be associated with chronic hypoxaemia and pulmonary infection respectively. Sputum Gram staining and culture may allow optimal pre-operative antibiotic therapy. Sputum cytology may assist in the diagnosis of neoplasms. Abnormal liver function tests, cardiac technetium scanning, hypercalcaemia, and anaemia, thrombocytopenia or leukopenia may indicate involvement of the respective organ system. A chest X-ray may suggest hyperinflation, lobar collapse, consolidation, pleural involvement, bone lysis, airway compression or deviation, bullae,

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mediastinal enlargement, pneumothorax, lesions in the lung fields and lung abscess. These issues will influence pre-operative preparation, optimization and intra-operative management. Electrocardiography serves as an adjunct to history and physical examination, and the presence of new or unanticipated repolarization changes on a baseline electrocardiogram (ECG) warrants further cardiac evaluation for the presence of coronary artery disease. The pre-operative cardiac assessment for patients undergoing non-cardiac surgery has been extensively reviewed. Patients with isolated hypoxaemia, as detected by arterial blood gas analysis, usually have intrapulmonary shunting or mismatch of ventilation and perfusion. The cause for this will usually be apparent from the history and chest X-ray. Patients with chronic lung disease may have chronic hypoventilation and carbon dioxide retention. This elevated basal arterial CO2 tension (Paco2) reflects an impaired ventilatory response to carbon dioxide and suggests that further diminution in alveolar ventilation will occur in the context of general anaesthesia and opioids. In general, a resting Pac% greater than 50 mmHg represents an absolute contra-indication to pneumonectomy. Patients with primarily severe emphysema or early interstitial pulmonary fibrosis present with dyspnoea and maintain a normal Pac% owing to increased minute ventilation. Although the Paco2 may be normal, the ventilatory requirements are elevated and spontaneous effort may be inadequate post-operatively, indicating the need for assistance with mechanical ventilation. Pulmonary function testing (PFT) is performed to assess those patients at risk of increased morbidity and mortality, the effect of bronchodilator therapy, the degree of lung resection possible and the need for postoperative ventilation. Total lung capacity (TLC), vital capacity (VC), functional residual capacity (FRC) and forced expiratory volume in 1 second (FEV~) will all decrease with thoracotomy, regardless of the extent of postoperative analgesia (Tisi, 1979; Shulman et al, 1984). The natural history of post-operative pulmonary dysfunction has been reviewed in a landmark article by Craig (1981). Expiratory reserve volume (ERV) decreases by up to 60% following thoracotomy. These changes occur immediately in the post-operative period and require days to return to normal values. A major concern in patients scheduled for lung resection is the predicted post-operative pulmonary function. Because PFTs are standardized according to patients' age, sex and height, the most practical approach is to think in terms of the percentage of predicted values. The risk of morbidity is proportional to both the degree of pulmonary impairment and the amount of lung tissue resected. An inability to climb one flight of stairs suggests a prohibitive degree of peri-operative risk, while the ability to climb more than three flights suggests that a pneumonectomy may be undertaken without the need for further investigative pulmonary function testing (Ginsberg, 1995). Exercise oximetry provides some refinement of the basic exercise testing, and the absence of arterial oxygen desaturation on exercise provides additional reassurance of the cardiopulmonary reserve. Postoperative pulmonary function can be predicted to a certain extent by the

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combination of pre-operative pulmonary function and an assessment of the percentage of pulmonary blood flow to the area of lung scheduled to undergo resection. If the percentage 'remaining blood flow' (i.e. 100% minus the percentage blood flow to the area to be resected) is multiplied by the pre-operative FEVI, a reasonable assessment of the predicted postoperative FEV~ should be yielded. If this value is greater than 0.8 litre, the planned lung resection is reasonable, as long as complicating factors, such as hypercapnic ventilatory failure, pulmonary hypertension and concomitant cardiac disease, are not prohibitive. Other approximate guidelines for pneumonectomy, lobectomy and segmental resection are minimum values for FEV~ of 2 litres, 1 litre and 0.6 litre, respectively. Assessment of elevated pulmonary vascular resistance includes clinical, electrocardiographic and radiological evidence of pulmonary hypertension and right ventricular strain or failure. Patients with elevated pulmonary vascular resistance (PVR) and/or impaired right ventricular function may not be able to tolerate the increased pulmonary pressure associated with pulmonary artery clamping and lung resection. A PVR greater than 190 dynes.sec.cm-5 was related to increased operative risk (Jones, 1980). This can be assessed pre-operatively by the insertion of a pulmonary artery catheter, estimation of the resting pulmonary arterial pressure (PAP) and calculation of the PVR. Increases in PAP (>40mmHg) and Paco2 (> 60 mmHg) or decreases in arterial oxygen tension (Pao2) (< 45 mmHg) following balloon occlusion of the pulmonary artery suggest the inability to compensate for vascular occlusion (Benumof, 1995). The assessment of patients with mediastinal masses presents special anaesthetic challenges. Surgery is usually undertaken in this context to obtain tissue for diagnosis (bronchoscopy with or without mediastinoscopy) or to relieve acute airway obstruction (laser bronchoscopy or stent insertion). Pre-operative assessment centres around formulating a plan to secure the patient's airway and contingency plans in the event of difficulty. The key issue before inducing anaesthesia is knowledge of the airway anatomy. Although history, physical examination, spirometry, chest X-ray, X-ray of the thoracic inlet and flow-volume loop analysis may yield useful information, the definitive investigation is a computed tomography (CT) scan covering the whole airway. The critical questions are: 1. 2. 3. 4. 5.

Is there airway compression or involvement? What is the extent of the airway narrowing? How high above the carina is the mass? Is tracheomalacia present? Can the patient tolerate the supine position for the induction of anaesthesia?

The anaesthetist should ensure that the endotracheal tube is distal to any airway compression prior to the induction of general anaesthesia or paralysis. Additional considerations in patients with mediastinal mass lesions include the presence of superior vena caval compression or pericardial or cardiac involvement. These issues can be addressed by echocardiography, in addition to CT scan of the thorax.

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MONITORING The key issues relating to monitoring for thoracic surgery centre on the presence and severity of systemic disease, the nature of the pulmonary pathology present and the dynamics of the specific surgery involved. Standard patient monitors, as for all procedures, include ECG, pulse oximetry, arterial blood pressure measurement, direct observational assessment of the patient and access to a neuromuscular stimulator and temperature probe. Pulse oximetry is mandated during anaesthesia by most national professional anaesthesia standards associations. Pulse oximetry--allowing for the technical limitations, including hypothermia, low cardiac output, hypoperfusion, diathermy use and interference from external light--is extremely useful in the assessment of arterial haemoglobin oxygen saturation (Sao2) in the range of 60-100%. The waveform may also be useful in the detection of innominate artery compression during mediastinoscopy, as the perfusion through the fight brachial artery will be reduced. This can be detected if the pulse oximeter is placed on a finger on the fight hand. It is important to note, however, that pulse oximetry does not detect significant shunting, or its extent, when the Sao2 remains greater than 99% in the context of a high inspired oxygen fraction (F~o2). Furthermore, the device gives no indication of the aetiology of the decreased Sao2 when this is detected. An additional critical point to note is the fact that pulse oximetry is a poor monitor of alveolar hypoventilation in the presence of supplemental oxygen. In addition to pulse oximetry for the assessment of Sao2, the transcutaneous oxygen sensor and the indwelling intra-arterial 'optode' have been employed for the assessment of arterial oxygen tension. The intra-arterial 'optode' is a fibre-optic probe that consists of a single heparin-coated optical fibre, which is inserted via a small intra-arterial catheter and has a luminescent dye-coated tip. It functions by emission of light from the fibre and activation of the luminescent dye. Although of dubious accuracy at low levels of Pao2 (Barker et al, 1987), it allows simultaneous arterial pressure monitoring, arterial blood sampling and direct oxygen measurement, and allows the anaesthetist to detect intermediate grade shunts in which the Sao2 is still in excess of 99% but the Pao2 has decreased significantly from baseline. Direct arterial cannulation is useful in thoracic surgery as it allows for continuous beat-to-beat measurement of blood pressure as well as sampling for the determination of arterial blood gases. Major changes in arterial pressure are common accompaniments of surgical manipulations or intravascular volume shifts, and rapid recognition permits early detection, diagnosis and correction (Nobak, 1983). Serial arterial blood gas determinations may be useful during one-lung anaesthesia to provide warning of impending arterial hypoxaemia, prior to actual arterial haemoglobin desaturation. Detection of hyper- or hypoventilation can also be determined directly from the Paco2, rather than relying on the end-tidal Pco2. However, we do not believe that there is a need for serial arterial blood gas determinations in uncomplicated, routine one-lung anaesthesia. During anaesthesia for mediastinoscopy, placement of the arterial cannula in the fight radial artery will allow monitoring of compres-

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sion of the innominate artery by the mediastinoscope (Petty, 1979). Loss of the arterial blood pressure waveform indicates decreased blood flow to the brain through the right common carotid artery via the innominate artery, and allows repositioning of the mediastinoscope. However, if the systemic arterial pressure, as opposed to the right carotid circulation, is of primary importance, the arterial cannula should be placed in the left radial artery and the digital pulse oximeter placed on a digit on the fight hand. Pulmonary artery catheterization, allowing estimation of left-sided filling pressures, cardiac output and calculation of derived haemodynamic parameters, in addition to the measurement of mixed venous oxygen saturation (Svo2) and the facility of atrial and/or ventricular pacing, has many theoretical applications in the field of thoracic anaesthesia (Nobak, 1983). However, many features of thoracic anaesthesia, especially single-lung ventilation, render the application of the pulmonary artery catheter (PAC) less useful. For example, the catheters are usually--but not always---directed, by pulmonary artery curvature and flow, to the fight lung. Uncertainty about which lung the catheter is located in, which perfusion zone the catheter is in, alterations in ventricular compliance, changes in ventricular independence) alterations in the reliability of cardiac output and Svo2 measurements when the catheter is located in a non-dependent and deflated lung, and variable effects of positive end-expiratory pressure (PEEP), all serve to limit the usefulness of the PAC as a clinical tool in thoracic surgical procedures. More sophisticated PAC catheters are available, such as the PAC with five pacing electrodes, which can be used for atrial, ventricular or atrioventricular sequential pacing in patients who require a PAC for haemodynamic monitoring. A further development in the area of PAC monitoring has been the addition of fibre-optic bundles for light transmission, allowing the continuous measurement of Svo2. A key issue in the management of most thoracic surgical patients is the requirement for minimization of fluid intake. Regardless of the patient's haemodynamic status, fluid intake should be reduced to the minimum tolerable, given the patient's underlying medical condition and the assessment of ongoing losses. In our institution, therefore, despite caring for critically ill patients undergoing thoracic surgery, we seldom employ a PAC and find that most patients--certainly all 'routine' ASA class II or III patients--can be managed without a PAC. Estimation of Paco2 is possible with expired gas sampling, using a capnometer or mass spectrometer. The ability of end-tidal carbon dioxide to reflect the Paco2 in thoracic surgery is highly variable, so that arterial blood may need to be sampled for estimation of Paco2 directly. Upon commencement of single-lung ventilation, the tidal volume should be reduced by 20-25%, as dictated by increases in the airway pressure, and the ventilatory frequency increased proportionately. PHYSIOLOGY A gradient, induced by gravity, results in preferential distribution of pulmonary blood flow to the lower (more dependent) lung zones. During two-

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lung ventilation in the lateral position, the mean blood flow to the nondependent lung is less than that to the dependent lung. However, the loss of lung volume associated with anaesthesia and paralysis alters the relative pressure-volume relationships of the lungs. The dependent lung shifts from the highly compliant mid-portion of the pressure-volume (P-V) curve to the lower, less compliant portion. Factors associated with the reduction of FRC include general anaesthesia, paralysis, pressure of abdominal contents, compression by mediastinal structures and poor positioning on the operating table. The non-dependent lung shifts from a less compliant upper part of the P-V curve to the more compliant, middle position. Thus ventilation is preferentially distributed to the non-dependent lung, but perfusion is preferentially distributed to the dependent lung. This results in significant venous admixture. One-lung ventilation in this context results in worsened gas exchange associated with an obligatory right-to-left transpulmonary shunt through the non-ventilated, non-dependent lung. With normal pulmonary autoregulation (hypoxic pulmonary vasoconstriction: HPV), blood flow to the non-dependent hypoxic lung should be reduced. However, the effectiveness of this mechanism may be limited under certain circumstances. Furthermore, absorption atelectasis, accumulation of secretions and the formation of fluid transuded into the dependent lung also impair oxygenation. HPV was first described by Von Euler and Liljestrand in 1946 and characterized by others (Marshall et al, 1981). While extensive characterization of the mechanisms of HPV has been carried out in animal models (Benumof, 1985; Pearl, 1992), the importance of HPV in one-lung anaesthesia in humans has not been defined. In fact, a recent study from our group casts doubt on the role of HPV in clinical practice (Friedlander et al, 1994). In animal experiments, it has been shown that inhalational agents inhibit HPV, whereas intravenous drugs do not. Several categories of indication for single-lung ventilation currently exist. These include protection of a lung, ventilation of a lung and facilitation of surgical exposure. Lung protection may include unilateral prevention of the spillage of purulent material or blood, protection of unilateral bullae or blebs from the effects of positive pressure ventilation and protection during bronchoalveolar lavage. In terms of unilateral ventilation, the presence of a significant bronchopleural fistula, bronchial leak or major bronchus disruption with air leakage indicates that the selective ventilation of the contralateral lung will ensure alveolar ventilation. Upper lobectomy, pneumonectomy, videothoracoscopy and thoracic aortic aneurysm repair constitute the major reasons for lung separation in terms of optimizing surgical exposure. Lung separation optimizes exposure for lower or middle lobectomy and oesophageal resection, but is not critical in these cases. LUNG SEPARATION The three principal techniques available for lung separation are doublelumen endotracheal tubes, bronchial blockers, and endobronchial tubes. Bronchial blockers with an intrinsic lumen and a distal inflatable cuff

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have been used in the past but are currently seldom used. Arterial embolectomy catheters (Fogarty catheters) have also been used to provide separation of the lungs. They are inserted into the trachea before placement of a single-lumen endotracheal tube and are passed down the trachea until some resistance is met, with the curvature facing in the direction of the bronchus to be occluded. Using a fibre-optic bronchoscope, the catheter is then guided into either the right or left lung and positioned so that when the balloon of the embolect0my catheter is inflated, the lung is obstructed (Ginsberg, 1981). The obstructed lung then collapses by absorption atelectasis after ventilation with 100% oxygen. The technique may be especially useful in children in whom DLTs are too large. The smallest DLT available is a left-sided 28 French tube, which can be used in patients from 10 to 14 years old and from 30 to 45 kg. The bronchial blocker most often used for adults is a Fogarty occlusion (embolectomy) catheter (Ginsberg, 1981). In cases of difficulty with positioning the blocker, the placement can be facilitated by deflation of the endotracheal cuff and turning both the tube and the blocker in the required direction. Alternatively, the blocker may be passed directly through the lumen of the tube and positioned under direct fibreoptic visualization; the proximal end of the blocker may then protrude through a sealable bronchoscopic endotracheal tube adaptor port. In children weighing less than 10 kg, bronchial blockage can also be performed using a Fogarty embolectomy catheter with balloon capacity of 0.5 ml (Veil, 1969). Although the use of bronchial blockers can easily be learned, it may occasionally take more time to perform than does insertion of a DLT. In addition, the limited inability to suction and/or ventilate the lung distal to the blocker, coupled with the definite need for a fibre-optic bronchoscope, is a disadvantage compared with DLTs. If absolute separation of the lungs is essential, as in severe infective or haemorrhagic situations, a bronchial blocker should not be used as it is a relatively unstable system and may not guarantee absolute separation at all times. A combination bronchial blocker/single-lumen endotracheal tube (the Univent tube) was introduced in 1982 by Fuji Systems Corporation, Tokyo, Japan. This single-lumen endotracheal tube has a moveable endobronchial blocker housed in a channel within the wall of the endotracheal tube. The moveable blocker is positioned into the desired main-stem bronchus under direct vision with the aid of a fibre-optic bronchoscope (Inoue et al, 1982; Hultgren et al, 1986). There is a small lumen through the blocker that allows some suctioning and the application of oxygen and/or continuous positive airway pressure (CPAP) (Inoue et al, 1982; Kamaya and Krishna, 1985). The actual endotracheal tubes are very large and cumbersome, however, and the positioning of the blocker is not always straightforward. DLTs are currently the most widely used means of achieving single-lung ventilation. They consist of two attached modified tubes arranged such that the lumen of one tube extends into the mainstem bronchus and the other tube ends with a lumen in the distal trachea. A proximal tracheal cuff and a distal endobronchial cuff in the mainstem bronchus allow separation of the lungs.

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Disposable DLTs made of clear, non-toxic, tissue-implantable plastic are relatively easy to insert. The endobronchial cuff is blue, allowing recognition and optimal placement with the fibre-optic bronchoscope. In addition, the ends of both lumens have black radio-opaque lines, which allows recognition on a chest X-ray. The tubes have high-volume, low-pressure tracheal and endobronchial cuffs. Most practitioners use a left-sided tube for all instances where lung separation is required, and withdraw the tube in cases where the proximal left mainstem bronchus is to be occluded, for example in left pneumonectomy. The shape of the endobronchial cuff on the right-sided DLT allows right upper lobe ventilation and minimizes the chance of fight upper lobe obstruction by the tube. However, the take-off position of the right mainstem bronchus is highly variable. The clear tubing allows continuous observation of the tidal movements of respiratory moisture, as well as observation of secretions from each lung. P l a c e m e n t of a DLT

The curvature of the DLT is initially concave anteriorly, and after the distal tube passes 2-3 cm through the vocal cords, the stylet is removed and the tube is carefully rotated so that the endobronchial portion of the DLT is directed into the appropriate side. The tube is advanced until slight resistance is encountered. The depth of insertion for left DLTs has been shown to be approximately 29 cm at the incisors for patients who are approximately 170 cm tall. With each 10 cm increase in height, an additional 1 cm of depth is required (Brodsky et al, 1991). Much has been written about the optimal positioning of DLTs for thoracic surgery. One approach is to insert the DLT into the trachea as described above. When the tube is in the trachea, the proximal tracheal cuff is inflated and the lungs ventilated. Endotracheal position is rapidly confirmed by bilateral chest auscultation and visualization of end-tidal carbon dioxide. We then pass the paediatric bronchoscope through the tracheal lumen, identify the trachea and the carina, and ensure that the distal endobronchial cuff is just below the level of the carina when slowly inflated. If the endobronchial lumen is not on the desired side, the whole tube is withdrawn a few centimetres, the fibre-optic bronchoscope is passed through the distal endobronchial lumen, and the tube is then advanced into the desired mainstem bronchus. We do not believe in spending time performing a series of clamping and declamping manoeuvres when verification of positioning is so simple with direct vision. In one study, almost half of all DLTs that were thought to be in the correct position were subsequently shown to be incorrectly placed when confirmation was sought with fibre-optic bronchoscopy (Smith et al, 1987). We reconfirm correct tube placement after the patient is placed in the final position (Slinger, 1995). The outside diameter (OD) of the fibre-optic bronchoscope determines whether it will pass through the tracheal lumen of the DLT. The smallest sizes (2.6-4.2 mm OD) pass through all DLTs, the largest size (5.6 mm OD) does not pass through any, and those with an OD

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of 4.9 mm pass easily through a size 41 DLT and only with difficulty through a size 37 mm DLT. Where absolute lung separation is needed, the use of an underwater seal may be used. If the bronchial cuff is not adequately inflated and positive pressure is applied to the proximal bronchial lumen, gas will appear bubbling through the tracheal lumen. Malposition is the principal problem associated with the use of DLTs. The tube may be down the wrong side or may not be far enough down, or the bronchial cuff may herniate. In all cases, repositioning should take account of the acuteness of the clinical context and the stage of surgery. If significant hypoxaemia has developed owing to a DLT malposition or dislodgment, a sensible course is to deflate the endobronchial cuff, withdraw the DLT such that the bronchial lumen is above the carina and inflate both lungs with 100% oxygen. When hypoxaemia is corrected, the tube may be repositioned as above. If hypoxaemia is not critical and the clinical situation permits, the tube can be repositioned without recourse to two-lung ventilation. A DLT is relatively contraindicated where there is a lesion in the airway or a difficult upper airway that results in poor laryngeal visualization. However, in many circumstances, abnormal airway anatomy can be overcome by topicalizing the airway and passing the DLT via a bronchoscope passed through the endobronchial lumen. Patients requiring rapid sequence intubation do not constitute a contra-indication as long as laryngoscopy and tracheal intubation are expected to be relatively easy. Following endotracheal placement after a rapid sequence induction, precise endobronchial placement can be accomplished later, as described. M A N A G E M E N T OF ONE L U N G VENTILATION The management of one-lung ventilation in a paralysed patient in the lateral decubitus position with an open chest involves manipulation of the Fio 2, tidal volume (Vr), ventilatory rate, dependent lung PEEP and nondependent lung CPAP. An F~o2of 1.0 is routinely used during one-lung ventilation and serves to protect against hypoxaemia during the procedure. An F,o2 of 1.0 has resulted in mean Pao 2 values of between 150 and 210 mmHg during onelung ventilation (Tarhan and Lundborg, 1971; Kerr et al, 1974; Flacke et al, 1976; Capan et al, 1980). Absorption atelectasis in the dependent lung (Dantzker et al, 1975) can be minimized by the use of a high VT and PEEP. Recent work demonstrating the adverse effects of 100% inspired oxygen during anaesthesia in terms of the development of absorption atelectasis may have implications for one-lung anaesthesia. This issue remains to be studied in thoracic surgical patients. During one-lung ventilation, the dependent lung should be ventilated with a VT of between 10 and 12 ml/kgo A VT of between 8 and 15 ml/kg produces no significant effect on transpulmonary shunt or Pao2 (Katz et al, 1982). An inadequate Vr may result in atelectasis, whereas an excessive VT

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may result in significant increases in pulmonary vascular resistance in the ventilated lung, resulting in shunting of blood through the non-ventilated, non-dependent lung. The respiratory rate should be adjusted to maintain a Paco2 of 35-40 mmHg. Hyperventilation resulting in hypocapnia may decrease Pao2 by increasing dependent lung PVR and inhibiting nondependent lung HPV. At the start of one-lung ventilation, an Fio2 of 1.0, a tidal volume of 10 ml/kg and a 10-20% increase in respiratory rate are used. If a problem with either ventilation or arterial oxygenation occurs, a logical analysis and stepwise approach resolves the issues. First, if the situation is critical, immediate resumption of two-lung ventilation with 100% oxygen is indicated. If the situation is subacute, the usual checking of 100% delivery to the dependent lung should be confirmed by reviewing the delivery machine and the placement of the DLT. The most effective manoeuvre to increase Pao2 during one-lung ventilation is the application of CPAP to the non-dependent lung (Capan et al, 1980; Brown and Davis, 1984; Eisenkraft et al, 1984; Hannenberg et al, 1984; Thiagarajah et al, 1984; Merridew and Jones, 1985; Cohen et al, 1988). A level of CPAP of 5-10 crnH20 maintains FRC and reduces intrapulmonary shunt. The non-dependent lung should be expanded slightly with 100% oxygen prior to the application of ipsilateral CPAP, which at a level of 5-10 cmH20 does not inflate the lung enough to interfere with surgical exposure. CPAP can be applied to the non-dependent lung using a variety of delivery systems (Aalto-Setala et al, 1975; Brown and Davis, 1984; Hannenberg et al 1984; Lyons, 1984; Thiagarajah et al, 1984), all of which include an oxygen source, connector tubing to the non-dependent lung, a pressure relief valve and a pressure gauge. Although application of PEEP to the dependent lung results in increases in ipsilateral FRC, the use of such selective PEEP has been associated with either a decrease or only a slight increase in Pao2 (Tarhan and Lundborg, 1970; Capan et al, 1980; Katz et al, 1982; Cohen et al, 1988). PEEP may increase the PVR of the ipsilateral lung and divert perfusion to the nondependent side. If hypoxaemia is not corrected with non-dependent lung CPAP, PEEP should be applied to the dependent lung. The combination of CPAP and PEEP, each in the range of 5-10 cmH20, can be jointly titrated to yield the best Sao2. Two-lung ventilation should be reinstituted intermittently with the surgeon's co-operation should the CPAP/PEEP combination fail. In the case of a pneumonectomy, occlusion of the pulmonary artery will eliminate the shunt.

BRONCHOSCOPY Bronchoscopy can be performed using a rigid or a flexible fibre-optic bronchoscope (FOB). In either case, the procedure can be performed under local or general anaesthesia. However, in the vast majority of cases, rigid bronchoscopy is performed under general anaesthesia. Topical anaesthesia of the airway is best pel-formed following pre-treatment with anti-sialogogues. Topical or regional application of cocaine and/or lidocaine (O'Callaghan-

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Enright and Finucane, 1995) and intravenous sedation with appropriate monitoring may be used. If general anaesthesia is chosen for FOB, anaesthetic agents with an appropriate duration of action should be chosen. In addition, topicalization of the airway following induction of general anaesthesia greatly reduces the anaesthetic requirements and attenuates the responses to airway instrumentation. For FOB, a wide-bore, single-lumen tube provides optimal conditions and can be changed if necessary to a DLT for thoracotomy. Several techniques can be used to maintain ventilation and oxygenation during rigid bronchoscopy, including apnoeic oxygenation, apnoea and intermittent ventilation, intermittent jet ventilation and high-frequency jet ventilation (HFJV). Apnoeic oxygenation consists of the insufflation of oxygen at 10-15 litres per minute via a small endotracheal catheter. With pre-oxygenation, oxygenation for more than 30 minutes can be attained (Frumin et al, 1959). However, if the duration of apnoea exceeds 5 minutes, increases in Paco2 become significant. For the technique of apnoea and intermittent ventilation, oxygen and volatile anaesthetics (unless intravenous anaesthesia is being used) are delivered from the anaesthetic circuit to the bronchoscope, which is fitted with an eye-piece covering the closed end. The Sanders injection system applies the Venturi principle to ventilate the lungs by attaching a jet ventilator (oxygen at 50 psi via a thin cannula) and inflating through the bronchoscope. The ventilation is directed parallel to the long axis of the bronchoscope through a side port and is regulated with a toggle switch. The major advantage of the Sanders system is that continuous ventilation is possible, extending the permissible duration of the procedure and allowing ongoing surgical inspection and intervention. In one comparative assessment, Paco2 was lower when the Sanders system, as opposed to intermittent ventilation, was used (Giesecke et al, 1973). Highfrequency positive-pressure ventilation (HFPPV) has been described for rigid bronchoscopy. With an HFPPV of up to 150 breaths per minute, blood gases were comparable to the Sanders technique, but at frequencies of 500 breaths per minute, oxygenation deteriorated and carbon dioxide was not removed effectively. However, HFPPV has the advantage that the tracheobronchial wall remains immobile during ventilation (Vour'h et al, 1983). Neodymium-yttrium-aluminum garnet (Nd-YAG) lasers are used for the resection of obstructive airway pathology. This is usually conducted with general anaesthesia and neuromuscular paralysis. The laser beam is introduced using a fibre-optic bundle passed either through a port of the FOB or directly through a rigid bronchoscope. To minimize the risk of an airway fire, the lowest possible Fio2 (using an oxygen/air blender) is used (Warner et al, 1984). In addition, saline-soaked packs and specially designed nonflammable endotracheal tubes reduce this risk (Eisenkraft and Neustein, 1992). Complications of bronchoscopy include mechanical trauma to the pharynx or teeth, haemorrhage, hypoxaemia, pneumothorax (especially following transbronchial biopsy in the setting of positive pressure ventilation),

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reflex bronchospasm, haemodynamic instability, bronchial or tracheal perforation, subglottic oedema and barotrauma. MEDIASTINOSCOPY Mediastinoscopy is used to biopsy and stage the mediastinal spread of neoplasms prior to thoracotomy. The mediastinoscope is inserted superior to the sternal notch under general anaesthesia. Muscle relaxation is important to prevent coughing. Complications include haemorrhage, pneumothorax, recurrent laryngeal nerve injury and occlusion of the innominate artery (Lee and Salvatore, 1976). MEDIASTINAL MASSES

Patients with anterior mediastinal masses present significant specific difficulties, as discussed above (Neuman et al, 1984). Options include empirical treatment and mass shrinkage with steroids, radiotherapy or chemotherapy. Failing this, biopsy through an anterior mediastinotomy can be performed under local anaesthesia. If this is not possible, assessment and planning for anaesthesia should proceed along the lines suggested above. The endotracheal tube should be distal to the site of airway compression, as confirmed by fibre-optic bronchoscopy, and back-up provisions include alteration of patient positioning (e.g. the lateral position), rigid bronchoscopy and prior set-up for femoral-femoral bypass. THORACOSCOPIC SURGERY

Thoracoscopy permits visualization of the pleura, pleurodesis, laser therapy for pneumothorax and endoscopic pulmonary resection. Thoracoscopy can be performed with local anaesthetic infiltration plus intercostal nerve blocks to provide local and regional anaesthesia and anaesthetize the parietal pleura, plus ipsilateral stellate ganglion blockade to suppress coughing. If general anaesthesia is used, the lungs should usually be separated, especially for thoracoscopic surgery. Thoracoscopic surgery has become standard for pulmonary resection, biopsy and bleb removal. The anaesthetic issues relating to these procedures are similar to standard management of one-lung ventilation, the exceptions relating to carbon dioxide insufflation, post-operative analgesia and pulmonary function, and the potential for spontaneous ventilation (Slinger, 1995). The effects of carbon dioxide insufflation are variable and may produce haemodynamic instability. Furthermore, because of the intrinsic elastic recoil of the lung, there is usually no need for positive pressure in the operative hemithorax (Slinger, 1995). The anticipated benefits with respect to pain and pulmonary function after thoracotomy are probably realized, based on clinical observations, but the issue has not been resolved by properly conducted randomized con-

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trolled trials. Although the hemithorax is opened for the introduction of the thoracoscope, once the lung has collapsed and the thoracoscope is inserted, the chest is effectively resealed and a stable pneumothorax is established. It is then quite possible to have a patient breathe spontaneously and avoid the complications of one-lung ventilation and positive pressure ventilation (Slinger, 1995). B R O N C H O P L E U R A L FISTULA Anaesthesia for repair of bronchopleural fistulae centres on providing adequate ventilation to the unaffected lung. If the fistula is complicated by empyema, the additional concern is contamination of the unaffected lung. If the fistula is large, and/or there is significant sepsis, lung separation is required. A bronchial blocker has the limitation of not permitting the suctioning of purulent matter from an infected lung. Furthermore, prior to lung separation, spontaneous ventilation may be necessary as positive pressure ventilation may result in most of the tidal volume exiting through the fistula. In practice, if the fistula is small or moderate and there are no anticipated difficulties in endotracheal intubation, induction of general anaesthesia and intubation with a DLT can proceed. For large fistulae, insertion of a DLT with spontaneous ventilation, with the patient awake or asleep, is advised. Problems associated with bronchopleural fistula and empyema are related to positive pressure ventilation, which may result in infectious contamination of healthy lung tissue, loss of tidal volume, decreased alveolar ventilation leading to carbon dioxide retention, and the development of a tension pneumothorax. In cases of large bronchopleural fistulae, HFJV may be the optimal treatment. However, there is no universal agreement on this (Bishop et al, 1987). BULLOUS DISEASE Surgical excision of bullae results in a decreased propensity for pneumothorax. If the bulla is large in the context of minimal pulmonary reserve, removal may lower lung volume and improve lung compliance. Intraoperative positive pressure ventilation may be associated with extremely large dead space or expansion or rupture of the bulla. The latter can result in the development of tension pneumothorax. If there is significant concern about pneumothorax, maintenance of spontaneous ventilation is required until separation of the lungs is achieved. In practice, induction of anaesthesia with gentle manual ventilation and intubation suffices, so long as there is the immediate facility to decompress a potential pneumothorax. HFJV has been described for the anaesthetic management of bullectomy (Normandale, 1985; McCarthy et al, 1987), as has a technique of sequential one-lung ventilation using a DLT (Benumof, 1987).

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T R A C H E A L RESECTION The key issues in anaesthesia for tracheal resection are three-fold: is there significant airway stenosis or obstruction preoperatively?; how are ventilation and anaesthesia to be accomplished during the resection?; and how is the patient to be managed following resection? If there is significant tracheal stenosis, the airway should be secured with the patient awake and breathing spontaneously, or, if this is impossible, cardiopulmonary bypass should be used from the outset. For intra-operative ventilation, a sterile endotracheal tube with a sterile circuit may be inserted into the distal trachea, HFJV may be used or cardiopulmonary bypass may be employed. After resection, the original endotracheal tube can be advanced beyond the tracheal suture line and ventilation continued as before. With low tracheal or bronchial lesions, resection and reconstruction may be performed with a DLT or endobronchial tube in situ. If the patient is ventilated through a circuit connected to the anaesthetic machine, volatile agents can be used to maintain anaesthesia. If not, intravenous anaesthetics are required. Post-operatively, extubation followed by maintenance of neck flexion is required to protect the anastomosis. In our institution, strong sutures extending from the chin to the base of the neck are used to accomplish this position. We prefer to use continuous infusion techniques consisting of propofol, alfentanil and vecuronium for general anaesthesia for these procedures. LUNG TRANSPLANTATION The development of lung transplantation has been enhanced by significant advances in surgical technique, patient selection, organ protection and postoperative management, including immunosuppression. In many centres, the current major option for lung transplantation is the so-called sequential single-lung transplantation (SSLT) (Kaiser et al, 1991). At our centre, the patient profile for SSLT is emphysema 40%, bronchiolitis obliterans 3%, cystic fibrosis 32%, bronchiectasis 6%, interstitial lung disease 11%, primary pulmonary hypertension 4% and pulmonary hypertension due to Eisenmenger's syndrome 4%. The selection criteria for organ donation at our hospital include age under 55 years, excellent oxygenation, clear chest X-ray, no evidence of aspiration or infection on bronchoscopy, no evidence of lung injury and the absence of previous thoracotomy. In addition, some centres require negative cytomegalovirus titres. The maintenance of the organ donor is described elsewhere (Cheng et al, 1994), and the optimal preservation of the excised lungs is undergoing constant improvement. Excellent strategies have been proposed to assess the intra-operative needs for patients undergoing SSLT (Cheng et al, 1994). The key issue in these patients is prediction of the need for intra-operative cardiopulmonary bypass. In our institution, the best predictors for cardiopulmonary bypass include:

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1. the inability to walk more than 300 m in 6 minutes; 2. desaturation to less than 85% Sa% on treadmill exercise testing in the context of supplemental oxygen; 3. an oxygen requirement in excess of 5 litres per minute during exercise; 4. a right ventricular ejection fraction of less than 27% during exercise (de Hoyos et al, 1993). We do not recommend premedication, other than antisialagogues, prior to the induction of anaesthesia. Anaesthesia is induced using a modified rapid sequence induction, owing to the urgent nature of the surgery, and frequently with the patient in a semi-recumbent position. The largest possible DLT is inserted. A PAC is then inserted, taking into account the risk of pneumothorax and using a sufficiently long sheath to allow withdrawal prior to pulmonary artery division and reinsertion under direct vision prior to pulmonary artery reanastomosis. Nitrous oxide is avoided in order to maximize the Fi% to prevent further elevation of PVR and to reduce the propensity for expansion of a potential pneumothorax. Immunosuppressive therapy is begun intra-operatively with the administration of methylprednisolone and continued after surgery with methylprednisolone, cyclosporine and azathioprine. In addition, some institutions include monoclonal lymphocyte antibody in the regimen. The major intra-operative complications associated with SSLT have been reviewed by Cheng et al (1994) and include the inability to rely on end-tidal Pco2 values owing to massive physiological dead space, hypoxaemia associated with hypoventilation and reduced lung volumes prior to the final testing of anastomotic sutures, inadequacy of single-lung ventilation associated with reduced minute ventilation and breath stacking during single-lung ventilation, systemic hypothermia and complications associated with the use of cardiopulmonary bypass. The decision to use cardiopulmonary bypass in these cases is based on the development of pulmonary hypertension, hypoxaemia, hypercarbia or inadequate systemic perfusion when the pulmonary artery is clamped (Cheng et al, 1994). Cardiopulmonary bypass is always used in this context if excessive inotropic or pressor support is required. After the second lung is reperfused and ventilated, the anastomosis is wrapped and checked, both mainstem bronchi are thoroughly suctioned, the DLT is replaced with a single-lumen endotracheal tube and the patient is transferred to the ICU intubated and mechanically ventilated.

POST-OPERATIVE COMPLICATIONS Thoracic surgical procedures may be complicated by almost any type of post-operative surgical complication relating to respiration, systemic circulation, bleeding and infection. However, a number of specific acute complications need to be addressed. Herniation of the heart may occur after extended pneumonectomy and presents as profound hypotension, hypoxaemia and a change in the ECG axis, with an altered chest X-ray. If it is

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suspected, the patient should be immediately returned to the operating room and, during transport, should be managed with the operative side up, pressor circulatory support, 100% oxygen and elimination of PEEP and reduction of airway pressures (Sandier, 1995). Application of positive pressure into the chest tube on the operative side may relieve the situation, but care must be taken that the chest tube is actually functional and that the diagnosis is not actually ipsilateral tension pneumothorax. Some degree of pulmonary oedema and atelectasis in the dependent lung is the norm rather than the exception, and is contributed to by fluid shifts owing to lateral positioning during surgery. Atelectasis can be compounded by ventilation at low Vr (tidal volumes). Post-thoractomy haemorrhage can be profound and should be expeditiously explored. Atrial dysrhythmias occur in approximately 1 in 5 patients, and the prophylactic use of digoxin does not appear to alter the outcome (Shields and Uyiki, 1968). Peripheral nerve injury, due to either malpositioning or surgical trauma, can jeopardize the brachial plexus, or intrathoracic, recurrent laryngeal or phrenic nerves. P O S T - T H O R A C T O M Y PAIN C O N T R O L Pain control after thoracic surgery has been the focus of numerous articles and has recently been reviewed by our group (Kavanagh et al, 1994a). The pain is severe and in a significant number of patients may be associated with long-term discomfort (Dajczman et al, 1991). Systemic modalities include systemic opioids, non-steroidal anti-inflammatory drugs (NSAIDs) and ketamine. Systemic opioids are the traditional therapy and have been administered in a variety of modes, including intravenous, subcutaneous and intramuscular routes. Many opioids can be safely and effectively used, the usual problems encountered including respiratory depression, nausea and vomiting and somnolence. NSAIDs have a major role in the therapy of post-thoractomy pain. Rectal indomethacin (Keenan et al, 1983), intravenous lysine-acetyl salicylate (Jones et al, 1985), tenoxicam (Merry et al, 1992) and diclofenac (Perttunen et al, 1992) significantly reduce pain scores and/or decrease the required amount of supplemental systemic analgesic. The potential adverse effects include operative bleeding, renal dysfunction and upper gastrointestinal bleeding, but these do not appear to be significant problems in the majority of patients (Dahl and Kehlet, 1991). The use of intramuscular ketamine has been described for the acute management of post-thoractomy pain (Dich-Nielsen et al, 1992) and was found to be as efficacious as systemic meperidine. There is a possibility that such agents as ketamine may have a significant role in the modulation of central nervous system sensitization and the subsequent development of postoperative pain in general (Woolf and Thompson, 1991). Adverse effects of ketamine are infrequent with analgesic, as opposed to induction, doses of the drug.

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Regional anaesthesia for post-thoractomy pain includes intercostal, interspinal and interpleural blockade, cryoanalgesia and transcutaneous electrical nerve stimulation (TENS). Intercostal analgesia may be achieved in a number of ways, although the use of indwelling catheters is increasing. The overall results from well-designed studies examining effectiveness suggest that intercostal catheters provide some enhancement of systemic analgesia, transiently reduce post-operative pain scores and lower the requirements for systemic opioids (Galway et al, 1975; Sabanathan et al, 1990; Chan et al, 1991; Dryden et al, 1993). The major concern with this mode of analgesia is the high systemic blood level of local anaesthetic obtained. However, clinical toxicity does not appear to be a problem. Inter-pleural analgesia consists of the administration of local anaesthetics through an indwelling catheter located in the pleural space. The overall impression from several studies is that the administration of bupivacaine yields short-term reductions in pain scores without decreasing the need for systemic opioids (Symreng et al, 1989; Mann et al, 1992; Schneider et al, 1993). Thoracic epidural local anaesthesia can provide a tightly circumscribed band of analgesia over the chest wall, resulting in highly effective postoperative pain relief (E1-Baz et al, 1984). The associated problems include technical difficulties with insertion of the catheter, urinary retention, hypotension and potential difficulties in dose titration. Epidural opioids may be administered through catheters located in the thoracic or lumbar regions. The principal problems associated with epidural opioids include respiratory depression, urinary retention, nausea and pruritus. Technical problems associated with epidural catheter placement are unrelated to the agents used and, depending on practice patterns, may be more common with thoracic rather than epidural cannulation. In general, lipid-soluble agents (e.g. fentanyl) should be administered close to the operative site, i.e. thoracic epidural in this context (Salomfiki et al, 1991). Lipid-insoluble agents (e.g. morphine) are probably as efficacious administered at any level. Therefore, if morphine alone is to be used, or if local anaesthetics are not to be used, lumbar cannulation is probably preferable in terms of technical ease of insertion and potential complications. Both thoracic and lumbar epidural administration of narcotics are highly effective (E1-Baz et al, 1984; Shulman et al, 1984; Whiting et al, 1988; Etches et al, 1991; Grant et al, 1992; Sandler et al, 1992), and there are no real advantages in terms of respiratory depression associated with the coadministration of epidural opioids and opioid antagonists (Gowan et al, 1988; Baxter et al, 1991; Etches et al, 1991). NSAIDs do not improve the already excellent analgesia achieved with a thoracic epidural opioid and local anaesthetic combination (Bigler et al, 1992). Paravertebral blockade has not been adequately tested in post-thoractomy analgesia. However, our impression, based on the unilateral blockade, ease of insertion and lack of complications, is that it has significant potential as a therapeutic modality. TENS, the basis of which is unknown (Melzack and Wall, 1965; Wall and Sweet, 1967), has similarly not been tested with any degree of clinical rigor.

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The role of pre-emptive analgesia in post-thoractomy pain relief is unclear, but preliminary evidence from our group suggests that there may be a slight benefit from pre-incisional, as opposed to post-incisional, lumbar epidural fentanyl (Katz et al, 1992). However, the pre-emptive use of multimodal regimens cannot currently be recommended (Kavanagh et al, 1994b).

SUMMARY Anaesthesia for thoracic surgery involves a diversity of skills and expertise, including clinical judgement, pre-operative assessment, airway management, intra-operative physiology and pharmacology, and the challenges of prevention and therapy of post-operative pain. It is a growth area in anaesthetic research and practice, and is one of the most challenging types of clinical anaesthetic practice.

REFERENCES Aalto-Setala M, Heinonen J & Salorinne Y (1975) Cardiorespiratory function during thoracic anesthesia: comparison of two-lung ventilation and one-lung ventilation with and without PEEP. Acta Anaesthesiologica Scandinavica 19: 287-295. Barker SJ, Tremper KK & Heitzmann HA (1987) Continuous fiberoptic arterial oxygen tension in dogs. Critical Care Medicine 15: 403. Baxter AD, Laganiere S, Samson Bet al (1991) A dose-response study of nalbuphine for postthoracotomy epidural analgesia. Canadian Journal of Anaesthetics 38: 175-82. Beecher HK (1940) Some controversial matters of anesthesia for thoracic surgery. Journal of Thoracic Surgery 10: 202-212. Benumof JL (1985) One-lung ventilation and hypoxic pulmonary vasoconstriction: implications for anesthetic management. Anesthesia and Analgesia 64: 821-833. Benumof JL (1987) Sequential one-lung ventilation for bilateral bullectomy. Anesthesiology 67: 268-272. Benumof JL (1995) Anesthesia for Thoracic Surgery, 2nd edn, pp 188-189. Philadelphia: WB Saunders. Bigler D, Moiler J, Kamp-Jensen Met al (1992) Effects of piroxicam in addition to continuous thoracic epidural bupivacaine and morphine on postoperative pain and lung function after thoracotomy. Acta Anaesthesiologica Scandinavica 36: 647-650. Bishop MJ, Benson MS, Sato Pet al (1987) Comparison of high-frequency jet ventilation with conventional ventilation for bronchopleural fistula. Anesthesia and Analgesia 66: 833-838. Brodsky JB, Benumof JL & Ehrenwerth J (1991) Depth of placement of left double-lumen endobronchial tubes. Anesthesia and Analgesia 73: 570-572. Brown DL & Davis RF (1984) A simple device for oxygen insufflation with continuous positive airway pressure during one-lung ventilation. Anesthesiology 61:481-482. Capan LM, Turndorf H, Patel C et al (1980) Optimization of arterial oxygenation during one-lung anesthesia. Anesthesia and Analgesia 59:847-851. Chad VWS, Chung F, Cheng DCH et al (1991) Analgesic and pulmonary effects of continuous intercostal nerve block following thoractomy. Canadian Joarnal of Anaesthetics 38: 733-739. Cheng DCH, Demajo W & Sandier AN (1994) ls•ng transplantation. Anesthesiology Clinics of North America 12(4): 749-765. Cohen E, Eisenkraft JB, Thys DM et al (1988) Oxygenation and hemodynamic changes during onelung ventilation. Journal of Cardiothoracic Anesthesia 2: 34-40. Craig DB (1981 ) Postoperative recovery of pulmonary function. Anesthesia and Analgesia 60: 46.

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Dahl JB & Kehlet H (1991) Non-steroidal anti-inflammatory drugs: rationale for use in severe postoperative pain. British Journal of Anaesthesia 66: 703-712. Dajczman E, Gordon A, Kreisman H et al (1991) Long term postthoracotomy pain. Chest 99: 270-274. Dalton ML Jr, Parker TM, Mistrot Jet al (1978) Concomitant coronary artery bypass and major noncardiac surgery. Journal of Thoracic and Cardiovascular Surgery 75:621-624. Dantzker DR, Wagner PD & West JB (1975) Instability of lung units with low V/Q ratios during O~ breathing. Journal of Applied Physiology 38: 886-895. Dich-Nielsen JO, Svendsen LB, Berthelsen P (1992) Intramuscular low-dose ketamine versus pethidine for postoperative pain treatment after thoracic surgery. Acta Anaesthesiologica Scandinavica 36: 583-587. Dryden CM, McMenemiu I & Duthie DJR (1993) Efficacy of continuous intercostal bupivacaine for pain relief after thoracotomy. British Journal of Anaesthesia 70:508-510. Eisenkraft JB & Neustein SM (1992) Anesthetic management of therapeutic procedures of the lungs and airway. In Kaplan JA (ed.) Thoracic Anesthesia, 2nd edn, pp 419-440. New York: Churchill Livingstone. Eisenkraft JB, Thys DM, Cohen E et al (1984) Hemodynamic effects of CPAP and PEEP during onelung anesthesia with isoflurane. Anesthesiology 61: A520. E1-Baz NM, Faber LP & Jensik RJ (1984) Continuous epidural infusion of morphine for treatment of pain after thoracic surgery: a new technique. Anesthesia and Analgesia 63-"757-764. Etches RC, Sandier AN & Lawson SL (1991) A comparison of the analgesic and respiratory effects of epidural nalbuphine or morphine in postthoracotomy patients. Anesthesiology 75: 9-14. Euler US yon, & Liljestrand G (1946) Observations on the pulmonary arterial blood pressure in the cat. Acta Physiologica Scandinavica 12: 310-320. Flacke JW, Thompson DS & Read RC (1976) Influence of tidal volume and pulmonary artery occlusion on arterial oxygenation during endobronchial anesthesia. Southern Medical Journal 69: 619. Friedlander M, Sandler A, Kavanagh B et al (1994) ls hypoxic pulmonary vasoconstriction important during single lung ventilation in the lateral decubitus position? Canadian Journal of Anaesthetics 41: 26-30. Frumin MJ, Epstein R & Cohen G (1959) Apneic oxygenation in man. Anesthesiology 20: 789. Galway JE, Caves PK & Dundee JW (1975) Effect of intercostal nerve blockade during operation on lung function and the relief of pain following thoractomy. British Journal of Anaesthesia 47: 730-735. Giesecke AH, Gerbershagen H, Dortman C et al (1973) Comparison of the ventilating and injection bronchoscopes. Anesthesiology 38: 298-303. Ginsberg RJ (1981) New technique for one lung anesthesia using an endobronchial blocker. Journal of Thoracic and Cardiovascular Surgery 32: 542-546. Ginsberg RJ (1995) Preoperative assessment of the thoracic surgical patient: a surgeon's viewpoint. In Pearson FG, Deslauriers J, Ginsberg RJ et al (eds) Thoracic Surgery, pp 29-36. New York: Churchill Livingstone. Gowan JD, Hurtig JB, Fraser RA et al (1988) Naloxone infusion after prophylactic epidurai morphine: effects on incidence of postoperative side-effects and quality of analgesia. Canadian Journal of Anaesthetics 35: 143-148. Grant RP, Dolman JF, Harper JA et al (1992) Patient-controlled lumbar epidural fentanyl compared with patient-controlled intravenous fentanyl for postthoracotomy pain. Canadian Journal of Anaesthetics 39: 214-219. Hannenberg AA, Satwicz PR, Dienes RS Jr et al (1984) A device for applying CPAP to the non-ventilated upper lung during one lung ventilation. II. Anesthesiology 60: 254-255. Hoyos A de, Demajo W, Snell Get al (1993) Preoperative prediction for the use of cardiopulrnonary bypass in lung transplantation. Journal of Thoracic and Cardiovascular Surgery 106: 787-795. Hultgren BL, Krishna PR & Kamaya H (1986) A new tube for one lung ventilation: experience with the Univent tube. Anesthesiology 65:A481. Inoue H, Shohtsu A, Ogawa Jet al (1982) New device for one-lung anesthesia: endotracheal tube with movable blocker. Journal of Thoracic and Cardiovascular Sttrgery 83: 940-941. Jones DP (1980) Symposium on non-cardiac thoracic surgery: diagnostic workup of chest disease. Surgical Clinics of North America 60: 743-755. Jones RM, Cashman JN & Foster JMG (1985) Comparison of infusions of morphine and lysine acetyl

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salicylate for the relief of pain following thoracic surgery. British Journal of Anaesthesia 57: 259-263. Kaiser LR, Pasque MK, Trulock EP et al (1991) Bilateral sequential lung transplantation: the procedure of choice for double-lung replacement. Annals of Thoracic Surgery 52: 438-445. Kamaya H & Krishna PR (1985) New endotracheal tube (Univent tube) for selective blockade of one lung. Anesthesiology 63: 342-343. Kaplan JA (ed.) (1992) Thoracic Anesthesia, 2nd edn. New York: Churchill Livingstone. Katz JA, Larlane RC, Faidey HB et al (1982) Pulmonary oxygen exchange during endobronchial anesthesia: effect of tidal volume and PEEP. Anesthesiology 56: 164-17l. Katz J, Kavanagh BP, Sandier AN et al (1992). Pre-emptive analgesia: clinical evidence of neuroplasticity contributing to post-operative pain. Anesthesiology 77: 439-464. Kavanagh BP, Katz J, Sandier AN (1994a) Pain control after thoracic surgery: a review of current techniques. Anesthesiology 81(3): 737-759. Kavanagh BP, Katz J, Sandier AN et al (1994b) Multimodal analgesia after thoracic surgel~¢does not reduce postoperative pain. British Journal of Anaesthesia 73" 184-189. Keenan DJM, Cave K, Langdon Let al (1983) Comparative trial of rectal indomethecin and cryoanalgesia for control of early postthoractomy pain. British Medical Journal 287: 1335-1337. Ken" JH, Crampton Smith A, Pccs-Roberts C et al (1974) Observations during endobronchial anesthesia. II. Oxygenation. British Journal of Anaesthesia 46: 84-92. Lee J & Salvatore A (1976) Innominate artery compression simulating cardiac arrest during mediastinoscopy: a case report. Anesthesia and Analgesia 55: 748-749. Lyons TE (1984) A simplified method of CPAP delivery to the non-ventilated lung during unilateral pulmonmy ventilation. Anesthesiology 61: 216-217. McCarthy G, Coppel DL, Gibbons JR et al (1987) High-frequency jet ventilation for bilateral bullectomy. Anesthesia 42: 411-414. Magill 1W (1936) Anesthesia in thoracic surgery. Proceedings of the Royal Society of Medicine 29: 643-652. Mann LJ, Young FR & Williams JK (1992) Intrapleural bupivacaine in the control of postthoracotomy pain. Annals of Thoracic Surgery 53: 449-454. Marshall BE, Marshall C, Benumof JL et al (1981) Hypoxic pulmonary vasoconstriction in dogs: effects of lung segment size and oxygen tension. Journal of Applied Physiology 51: 1543-1551. Marshall BE, Longnecker DE & Fairly HB (1987) Anesthesia for Thoracic Procedures. Oxford: Blackwell Scientific. Melzack R & Wall PD (1965) Pain mechanisms: a new theory. Science 150: 971-979. Menidew CG & Jones RDM (1985) Non-dependent lung CPAP (5 cmH20) with oxygen during ketamine, halothane, or isoflurance anesthesia and one-lung ventilation. Anesthesiology 63: A567. Merry AF, Wardall GJ, Cameron RJ et al (1992) Prospective, controlled, double-blind study of I.V. tenoxicam for analgesia after thoracotomy. British Journal of Anaesthesia 69: 92-94. Neuman G, Weingarten AE, Abramowitz RM et al (1984) The anesthetic management of the patient with an anterior mediastinal mass. Anesthesiology 60: 144-147. Nobak CR (1983) Intraoperative monitoring, in Kaplan JA (ed.) Thoracic Anesthesia. New York: Churchill Livingstone. Normandale JP & Feneck RD (1985) Bullous cystic lung disease. Anaesthesia 40:1182-1185. O'Callaghan-Enright S & Finucane BT (1995) Anesthetizing the airway. Anesthesiology Clinics of North America 13: 325-336. Pearl RG (1992) The pulmonary circulation. Current Opinion in Anesthesiology 5: 848-854. Perttunen K, Kalso E, Heinonen I e t al (1992) t.V. diclofenac in post-thoracotomy pain. British Journal of Anaesthesia 68: 474--480. Petty C (1979) Right radial artery pressure during mediastinoscopy. Anesthesia and Analgesia 58: 428-430. Piehler JM, Trastek VF, Pairolero PC et al (1985) Concomitant cardiac and pulmonary operations. Journal of Thoracic and Cardiovascular Surgery 90: 662-667. Rowbotham S (1926) Intratracheal anesthesia. Lancet 2: 583-584. Sabanathan S, Mearns AJ, Bickford Smith PJ et al (1990) Efficacy of continuous extrapleural intercostal nerve block on post-thoracotomy pain and pulmonary mechanics. British Journal of Surgery 77: 221-225. Salomaki TE, Laitinen JO & Nuutinen LS (1991) A randomized double-blind comparison of epidural versus in~avenous fentanyl infusion for analgesia after thoractomy. Anesthesiology 75: 790-795.

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Sandier AN (1995) Anesthesia. In Pearson FG, Deslauriers J, Ginsberg RJ et al (eds) Thoracic Surgery, pp 85-114. New York: Churchill Livingstone. Sandler AN, Panos L, Stringer D et al (1992) A randomized, double-blind comparison of lumbar epidural and intravenous fentanyl infusions for postthm'actomy pain relief: analgesic, pharmacokinetic and respiratory effects. Anesthesiology 77: 626-634. Schneider RF, Villamena PC & Harvey Jet al (1993) Lack of efficacy of intrapleural bupivacaine for postoperative analgesia following thoractomy. Chest 103: 414416. Shields TW & Ujiki GT (1968) Digitalization for prevention of an'hythmias following pulmonary surgery. Surgery Gynecology and Obstetrics 126: 743-746. Shulman M, Sandier AN & Bradley JW et al (1984) Postthoractomy pain and pulmonary function following epidural and systemic morphine. Anesthesiology 61: 569-575. Slinger P (1995) New trends in anaesthesia for thoracic surgery including thoracoscopy. Canadian Journal of Anaesthetics 42: R77-R84. Smith GB, Hirsch N & Ehrenwerth J (1987) Sight and sound: can double-lumen endotracheal tubes be placed accurately without fiberoptic bronchoscopy? British Journal of Anaesthesia 58: 1317-1320. Syrm-eng T, Gomez MN & Rossi N (1989) lntrapleural bupivacaine vs saline after thoracotomy: effects on pain and lung function--a double-blind study. Journal of Cardiothoracic Anesthesia 3: 144-149. Tarhan S & Lundborg RO (1970) Effects of increased expiratory pressure on blood gas tensions and pulmonary shunting during thoractomy with use of the Carlens catheter. Canadian Anaesthetists Society Journal 17: 4-11. Tarhan S & Lundborg RO (1971 ) Carlens endobronchial catheter versus regular endobronchial tube during thoracic surgery: a comparison of blood gas tensions and pulmonary shunting. Canadian Anaesthetists Society Journal 18: 594-599. Thiagarajah S, Job C & Rao A (1984) A device for applying CPAP to the non-ventilated upper lung during one lung ventilation. Anesthesiology 60: 253-254. Tisi GM (1979) Preoperative evaluation of pulmonary function: validity, indications, and benefits. American Review of Respiratory Disease 119:293-310. Vale R (1969) Selective bronchial blocking in a small child. British Journal of Anaesthesia 41: 453-454. Vour'h G, Fischler M & Michon F et al (1983) Manual jet ventilation v high-frequency jet ventilation during laser resection of tracheo-bronchial stenosis. British Journal of Anaesthesia 55: 973-975. Wall PD & Sweet WH (1967) Temporary abolition of pain in man. Science 155: 108-109. Warner ME, Warner MA & Leonard P (1984) Anesthesia for neodymium-YAG laser resection of major airway obstructing tumors. Anesthesiology 60: 230-232. Whiting WC, Sandier AN & Lau LC et al (1988) Analgesic and respiratory effects of epidural sufentanil in patients following thoracotomy. Anesthesiology 68: 36-43. Woolf CJ & Thompson SWN (1991 ) The induction and maintenance of central sensitization is dependent on N-methyl-D-aspartic acid receptor activation: implications for the treatment of postinjury pain hypersensitivity states. Pain 44: 293-299.