AnesthesiaWeb - Lit Reviews- A Prospective, Randomized Comparison of Preoperative and Continuous Balanced Epidural or Paravertebral Bupivacaine on Post-Thoracotomy Pain, Pulmonary Function and Stress Responses

February 2000

A Prospective, Randomized Comparison of Preoperative and Continuous Balanced Epidural or Paravertebral Bupivacaine on Post-Thoracotomy Pain, Pulmonary Function and Stress Responses.

Richardson J, Sabanathan S, Jones J, Shah RD, Cheema S, Mearns AJ
Br J Anaesth 1999;83:387-392.

Commentary by Richard W. Rosenquist, M.D.

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[ see abstract below ]

Although epidural analgesia has been shown to be highly effective, the technical aspect of inserting these catheters in the mid-thoracic region remains difficult for many practitioners. Even in qualified hands, these catheters are not always successfully placed. This important study by Richardson, et al. compares the use of continuous balanced analgesia using epidural or paravertebral bupivacaine on post-thoracotomy pain, pulmonary function and stress responses. The results of their study make a convincing argument that the performing a paravertebral block should be considered in the management of postoperative pain following thoracotomy. The ability to decrease visual analog pain scores at rest and with coughing, improve pulmonary function, decrease stress response, and reduce side effects are all very desirable. Further studies comparing these techniques in larger cohorts of patients will help determine the preferred method of providing postoperative analgesia.

ABSTRACT

A Prospective, Randomized Comparison of Preoperative and Continuous Balanced Epidural or Paravertebral Bupivacaine on Post-Thoracotomy Pain, Pulmonary Function and Stress Responses.
AUTHORS: Richardson J, Sabanathan S, Jones J, Shah RD, Cheema S, Mearns AJ.
SOURCE: Br J Anaesth. 1999;83:387-392.
ABSTRACT:
Objective: To determine the role of preoperative and continuous balanced epidural or paravertebral bupivacaine on post-thoracotomy pain, pulmonary function and stress responses.

Design: Randomized prospective case series.

Participants: One-hundred adult patients scheduled for elective thoracotomy.

Methods: Patients were randomized to either an epidural group or a paravertebral group. In the epidural group, preoperative catheterization was performed between T7 and T10 under local anesthesia. This was followed by a test dose of .5% bupivacaine 3 ml and then .25% bupivacaine 10-15 ml. In the paravertebral group, paravertebral blocks were performed at T6-8 ipsilateral to side of thoracotomy. The test dose was followed by an injection of .5% bupivacaine up to 20 ml. At least 20 minutes were allowed to elapse before the start of surgery. All patients were given a general anesthetic. Before chest closure in the paravertebral group, an epidural-type catheter was inserted by the surgeon into the paravertebral space under direct vision using a standard technique. During chest closure, a second bolus of .25% bupivacaine up to 20 ml was injected into the paravertebral space. In the epidural group, an additional 10 ml of .25% bupivacaine was injected into the epidural space. Postoperatively, all patients were given a continuous infusion of local anesthetic (.25% bupivacaine in the epidural group and .5% bupivacaine in the paravertebral group) at a rate of .1 ml/kg/hour. All patients also received diclofenac 50 mg q 8 hours and PCA morphine using a 1 mg bolus with a five minute lock-out with no background infusion.

Outcome Measures: Postoperative data was collected for a 48 hour period. Outcome measures included pain scores at rest and on maximal coughing, morphine requirements, hourly sedation scores, and nausea and vomiting episodes for the first 24 hours and then every four hours thereafter. Blood measurement of glucose and cortisol concentrations was obtained before operation, 15 minutes after incision, and at 4, 12, 24 and 48 hours after operation. Side effects, such as hypotension and urinary retention, were recorded. Postoperative respiratory morbidity was evaluated by looking at sputum changes, abnormalities in auscultation, chest radiological changes, fever greater than 38°C, glucose cytosis greater than a total white cell count of 14 X 10⁹/liter, and oxygen saturation less than 90%. In addition, the number of patients complaining of pain at the six month outpatient follow-up were also recorded.

Results: There were no significant differences between the two groups in age, sex, weight or type of surgery. An epidural catheter could not be placed in five patients and data from the remaining 95 patients were analyzed. The distribution of visual analog pain scores, both at rest and on coughing, were significantly different between the groups. Patients in the paravertebral group had significantly lower VAS pain scores, both at rest and on coughing. Cumulative morphine consumption in the first and second 24 hour periods was significantly higher in the epidural group. Pulmonary function as assessed by peak expiratory flow rate was significantly better in the paravertebral group. The lowest postoperative peak expiratory flow rate as a fraction of the preoperative control was .73 in the paravertebral group. In contrast, it was .54 in the epidural group. These minimal levels occurred at similar mean postoperative times of 19 hours. Pulse oximetry readings were significantly better in the paravertebral group throughout the 48 hour study as compared to the epidural group. Plasma concentrations of cortisol increased significantly from baseline in the epidural and paravertebral groups. Plasma concentrations of glucose increased significantly from baseline in the epidural group, but not in the paravertebral group. When the areas under the plasma concentration versus time curves were compared, the increases in both plasma cortisol and glucose concentration were significantly less in the paravertebral group. There were no neurologic complications in either group. The distribution of complications between the groups was significantly different, with a greater incidence of nausea, vomiting and postoperative respiratory morbidity in the epidural group. Postoperative hypotension requiring temporary cessation of infusion occurred in the epidural group only. The epidural group required significantly more frequent catheterization than the paravertebral group. The hospital stay was identical for both groups. In the follow-up out-patient clinic visit at six months, 10 patients in the epidural group had persistent chest pain compared with three in the paravertebral group.

Conclusions: Both continuous paravertebral and epidural blocks beginning before operation as part of a balanced analgesic regimen were highly effective for post-thoracotomy pain. In this study, the authors found that paravertebral analgesia was superior in terms of analgesia, pulmonary function, neuroendocrine stress responses, side effects and postoperative respiratory morbidity. Effective pain control following thoracotomy has consistently proved to be a challenging part of postoperative care. Thoracotomy produces one of the most damaging surgical insults, and is associated with significant pathophysiologic abnormalities. The severe chest wall trauma associated with this surgical procedure may include fractured ribs, damaged peripheral nerves and central nervous system hypersensitivity. This significant trauma is exacerbated by the fact that the chest wall cannot be immobilized to control pain, but must remain in constant motion to allow ventilation and clearance of secretions. Failure to control the pain adequately following a surgical procedure frequently results in the development of significant pulmonary complications. Although numerous techniques have been developed to help control the pain after thoracotomy, there is still no universally accepted method, and it remains a significant challenge. Techniques have included oral opiates, intravenous opiates, intercostal nerve blocks, cryoanalgesia, interpleural analgesia, epidural analgesia and paravertebral blockade. In addition, the development of neurogenic-type pain, which is poorly controlled by opiate analgesics, suggests a strong role for the use of local anesthetics as part of the postoperative analgesia plan. Ideally, a postoperative pain control plan is initiated preoperatively, maintained throughout the operation and carried into the postoperative period. Furthermore, a multi-modal or balanced approach that uses multiple medications is more effective than a single medication alone. This study demonstrated that continuous paravertebral analgesia as part of a balanced analgesia plan was superior to continuous epidural in terms of analgesia, pulmonary function, neuroendocrine stress responses, side effects and postoperative respiratory morbidity.