1Department of Anesthesiology, 2Department of Radiology, 3Department of Clinical Statistics, and 4Department of Thoracic Surgery, Nice School of Medecine, University of Nice-Sophia Antipolis, Hôpital Pasteur, Avenue de la voie romaine, F-06000 Nice, CHU de Nice, France*Corresponding author
Accepted for publication: April 30, 2001
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Abstract |
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Br J Anaesth 2001; 87: 5649
Keywords: complications, pulmonary; complications, morbidity; anaesthetics local; analgesics opioid, morphine; physiotherapy
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Introduction |
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Patients and methods |
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Respiratory characteristics were determined by clinical examination, chest x-ray, arterial blood gas analysis and respiratory function tests (forced expiratory volume in one second (FEV1) and the forced vital capacity (FVC)). The day before surgery, patients were randomized in one of the two groups of analgesia using a table of random numbers to receive either postoperative i.v. opioid PCA or epidural ropivacainesufentanil (TEA).
All patients were premedicated with 100 mg oral hydroxyzine and were given 1.5 g cefuroxime 1 h before and for 24 h after surgery (750 mg every 8 h). In the TEA group, a 20-gauge catheter (Vygon, Les Ulis, France) was inserted 34 cm into the epidural space after midline puncture at T4T5 with a Tuohy needle (Braun, Melsungen, Germany). Good position was defined by bilateral anaesthesia between T1 and T8 after injection of 3 ml of 2% lidocaine with 1/200 000 epinephrine via the epidural catheter. If the catheter could not be inserted or was accidentally withdrawn before day 3, the patient was given an i.v. PCA pump, but was kept in the TEA group for the intention to treat analysis.
General anaesthesia was standardized in groups. Induction was achieved with thiopental 5 mg kg1, sufentanil 0.5 µg kg1, and atracurium 0.5 mg kg1. After tracheal intubation with a left side double lumen endobronchial tube (Carlens®, Rüsch, Germany) (39 French women, 41 French men) the lungs were ventilated by a volume-cycled ventilator (Cato®, Dräger, Germany) at zero end-expiratory pressure, with a tidal volume of 10 ml kg1. The rate was adjusted to maintain an end-tidal carbon dioxide partial pressure near 35 mm Hg. After checking clinically that ventilation of the operative lung had ceased, anaesthesia was maintained with 0.51 MAC sevoflurane and 7080% oxygen in air, with the same ventilatory parameters maintained during one lung ventilation. Continuous infusion of atracrium 0.6 mg kg1 h1 and sufentanil 0.3 µg kg1 h1 was also maintained. Central body temperature and urinary flow were monitored. Invasive arterial pressure was monitored with a radial catheter inserted under general anaesthesia and a central venous line measured central venous pressure. At the end of surgery, the upper lung was re-expanded by manual inflation under visual control with 50% nitrous oxideoxygen. The final inflation was performed at Paw=40 cm H2O for 5 s. Patients were warmed until body temperature reached 36°C. When clinical signs of weaning were present, patients were extubated and oxygen administered via a nasal probe, adapted to pulse oximeter values (36 litre min1). Patients were placed in the PACU for 4 days.
Patients in the TEA group received an epidural continuous infusion of ropivacaine 0.2% combined with sufentanil (1 or 0.5 µg ml1 if age was over 70 yr). An infusion started 1 h before the end of surgery at a rate of 6 ml h1, and was adjusted thereafter according to the visual analogue scale (VAS). In the recovery room, i.v. PCA patients received an initial i.v. bolus administration of morphine (3-mg doses every 5 min) titrated by a nurse until VAS was lower than 40 mm. At this time, a PCA pump (Abbott Pain Manager®, Abbott Laboratories, North Chicago, IL, USA) was connected using a 1.5 mg bolus and a 5 min lockout period. If pain control was considered insufficient (i.e. VAS greater than 40 mm) analgesia rescue doses were given and repeated until efficient analgesia was achieved. In the i.v. PCA group, patients received a supplemental morphine 3 mg bolus every 5 min and in the TEA group, patients were given a supplemental bolus of ropivacaine 6 ml and continuous infusion was increased by steps of 2 ml h1 every 30 min if needed. Patient monitoring and treatment of hypotension, nausea, vomiting, and pruritus were standardized. In case of hypotension (defined as systolic arterial pressure lower than 90 or 100 mm Hg in patients with arterial hypertension history), patients were given boluses of ephedrine from 3 to 30 mg titrated to achieve values over 100 mm Hg. For nausea, droperidol 2.5 mg was given i.v. every 4 h as needed, followed by ondansetron 4 mg if control was insufficient or if vomiting occurred. For itching, propofol 1020 mg was given i.v. every 6 h as needed. All patients received propacetamol 2 g, an injectable acetaminophen prodrug, every 6 h, and 300 mg per 24 h continuous infusion of ketoprofen for 3 days. Patients were encouraged to use the PCA as often as needed and before physiotherapy.
Physiotherapy was performed twice a day by the same physiotherapist, according to a standardized 20-min procedure: abdominal and diaphragmatic breathing, deep breathing exercises and effective coughing. All patients received terbutalin aerosol just before physiotherapy. Patients were maintained in a semirecumbent position, and sat in an armchair the day following surgery.
Characteristics of patients were noted as well as factors influencing respiratory function, for example, smoking habit (pack yr), current or past-smoker (i.e. patients who stopped smoking for more than 8 weeks).7 All patients received respiratory physiotherapy for almost 3 days preoperatively. Type of lung resection, duration of lung separation and anaesthesia, blood transfusion and volume of fluid infused during surgery were also noted. Blood gas analysis was performed daily at 07:00 in ambient air for 15 min, as well as a respiratory function test in a sitting position (Flow Meter®, Sherwood Medical, St Louis, MO, USA), measuring FVC and FEV1. The physician performing the respiratory function tests was blinded to the study group. The best of three measurements was retained for analysis.
Chest x-ray was performed immediately after extubation. Thoracic CT scan was performed on the third day after the surgery (ELITE®, Epscint, IL, USA). All patients were placed in the supine position with arms above the head. Images were obtained from lung apex to costodiaphragmatic angle without i.v. infusion of contrast. Scans were obtained after inspiration of an ordinary tidal volume (acquisition time=1.1 s per section, tube current=240 mA and 140 KVp, matrix 512x512). The slice thickness was 10 mm with a 20 mm interval. Some 1 mm thick slices were obtained in patients with atelectasis. The dorsal border of atelectasis was manually highlighted. The ventral border between atelectasis and normal lung tissue was evaluated. The exact amount of atelectasis was calculated as the sum of all pixels (picture elements) having a density between 100 and +100 Hounsfield units.8 Absolute lung area was calculated for each scan as atelectatic and aerated areas. The extent of atelectasis was expressed in square centimetres as a percentage of the total lung area. Atelectasis was also classified into four types depending on thickness: lamellar atelectasis <3 mm, plate atelectasis >3 mm and <10 mm, segmental atelectasis >10 mm and lobar atelectasis.9
Clinical complications were assessed daily. A chest x-ray was performed and analysed by a radiologist in case of tachypnea over 20 breaths min1 associated with an arterial oxygen partial pressure below 60 mm Hg despite 6 litre min1 oxygen and fever (above 38.5°C). Clinical respiratory complications were classified in two groups: (1) atelectasis with clinical intolerance requiring bronchial clearing by fibroscopy (CT scan was performed just before the fibroscopy) and (2) pneumonia (modified criteria of Andrews).10
Patients assessed pain using VAS ranging from 0 (no pain) to 100 mm (worst pain imaginable) at rest and while coughing every 4 h. All patients were instructed how to use the VAS preoperatively. Side effects arising from the analgesic procedure were also recorded. General effects including hypotension (systolic arterial pressure <90 mm Hg or 100 if hypertension history), heart rate, sedation (0=awake, 1=sleepy but awakened by oral order, 2=sleepy but awakened by nociceptive stimulation, 3=not responsive), respiratory depression (respiratory rate less than 8 breaths min1), confusion, nausea, vomiting, and pruritus, were recorded at 4-h intervals for 4 days. Lower limb motor block was assessed twice a day with the Bromage score (0=no paralysis; 1=unable to raise the leg, 2=enable to bend the knee, 3=paralysis). Local complications were also sought, including neurological complications, catheter occlusion, kinks, and displacement.
On the fourth day, the epidural catheter was withdrawn, and bacteriological analysis performed. At the end of the study, global satisfaction concerning pain was evaluated on a VAS (0 mm=not satisfied; 100 mm=entirely satisfied).
The perioperative characteristics were compared using chi-squared analysis for category and the KruskallWallis test for continuous variables. The overall incidence of atelectasis in the two groups was compared with chi-squared analysis, whereas the percentage of atelectasis was evaluated with a Wilcoxon test. Postoperative assessment for all variables measured over time was evaluated using repeated measures analysis of variance. Results are presented as mean (SD). A significance threshold of P<0.05 was retained.
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Results |
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Discussion |
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Peroperative atelectasis was virtually eliminated by performing re-expansion manoeuvres.18 CT scans were obtained on the third day when the impact of analgesia was greatest. The scans were obtained after the inspiration of a normal tidal volume because the patients could not sustain a prolonged expiration. Radiological abnormalities seen earlier could have been influenced by the intraoperative period and pain was less intense up to day 3. We observed no atelectasis resulting from extrinsic compression, such as pleural effusion or gastric distention. This supports the idea that the reported incidence of these abnormalities reflects the quality of analgesia and postoperative physiotherapy.
Our main objective for analgesia was to obtain a VAS score at rest of less than 40 mm at rest at all times. Some authors have reported delays of 612 h before obtaining effective analgesia with i.v. PCA.19 We attempted to avoid these delays by concentrating on early pain scores and giving rescue analgesia doses to either group to obtain efficient, prolonged pain control at rest. However, pain relief during coughing or deep breathing exercises could only be obtained with TEA and local anaesthetics, in agreement with previous studies.4 A meta-analysis has also demonstrated that postoperative atelectasis is reduced by epidural analgesia.20 However, the control patients were given nurse-controlled intermittent parenteral injections of opioids, which may have resulted in an inappropriate plasma opioid concentration. The absence of difference between our groups could be a result of two factors: first, better pain control provided by i.v. PCA, as plasma opioid concentrations remained within the therapeutic index;21 second, the effect of multimodal analgesia, which reduces morphine consumption and improves the quality of analgesia.22
Respiratory physiotherapy designed to increase pulmonary volume prevents atelectasis and pulmonary complications.23 24 Because all patients were informed preoperatively about the importance of physiotherapy to prevent respiratory complications, all of them, in the i.v. PCA group sustained 20-min physiotherapy sessions twice a day, despite their pain. In addition, deep breathing exercises were done with the same efficiency whatever the analgesic techniques used, as all the groups had comparable forced vital capacity values. Respiratory comfort during physiotherapy was better with TEA than with multimodal analgesia, but it had no beneficial effect on postoperative lung consolidation.
Our patients could be classified as low respiratory risk on the basis of preoperative pulmonary function tests. However, there is no data suggesting that spirometry can identify high risk patients because of its variable predictive value.13 All the patients had been heavy smokers and almost half of them were smokers at the time of surgery; both of these factors are clinical respiratory risks.25 26 Most of the patients in other studies had no clinical risk factors, which explains the lack of difference between systemic opioids and TEA in pulmonary complications.5 Our population is representative of the large majority of patients undergoing thoracotomy, but it would be valuable to study the influence of TEA in a high risk groups selected with high risk factors.
We found no difference in clinical respiratory complications or in the length of hospital stays for the two groups of thoracotomized patients. The lack of statistical power to detect significant differences in true clinical outcomes could explain these results, as 150 patients would be required. Yeager and colleagues found an improvement in postoperative morbidity after thoracic surgery in high risk patients given epidural analgesia.27 However, in the absence of preoperative respiratory characteristics, clear definitions and sensitive diagnosis assessment of atelectasis and clinical respiratory complications, it is difficult to affirm a clear benefit of central block on postoperative pulmonary morbidity compared with parenteral opioids in that study.
In summary, despite optimization of i.v. PCA, the administration of local anaesthetics and opioids delivered via a thoracic epidural catheter provides better analgesia while coughing. However, compared with multimodal analgesia and active physiotherapy, TEA does not improve spirometric or oxygenation parameters, nor the amount and size of atelectasis on a standard population of smokers undergoing resection of lung cancer.
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Acknowledgements |
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References |
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