Clonidine added to bupivacaine enhances and prolongs analgesia after brachial plexus block via a local mechanism in healthy volunteers.

BACKGROUND AND OBJECTIVE: The addition of clonidine to local anaesthetics enhances pain relief after peripheral nerve block, but the site of action is unproven. METHODS: Seven healthy volunteers underwent three brachial block procedures using bupivacaine 0.25% 1 mg kg(-1) + epinephrine 1:200,000 (=local analgesic) in a randomized, double-blind cross-over fashion: (a) control treatment: local analgesic with 0.9% sodium chloride solution for the block and an intramuscular injection of saline; (b) intramuscular treatment: local analgesic with 0.9% NaCl for block and an intramuscular injection of clonidine 2 microg kg(-1) and (c) block treatment: local analgesic with clonidine 2 microg kg(-1) for block and an intramuscular injection of saline. RESULTS: The onset and duration of complete blockade (sensory/motor/temperature) was evaluated in the four nerve regions of the hand and forearm. Additionally, sedation score, blood pressure, heart rate and plasma clonidine concentrations were determined. The median duration of complete sensory blockade was 270 min (range 0-600) for block treatment compared to 0 min (range 0-480) for intramuscular treatment (P < 0.05) and 0 min (range 0-180) for control treatment (P < 0.05). Motor and temperature blockade exhibited similar results. Administration of clonidine was associated with sedation and a decrease in heart rate and blood pressure independent of the route of administration. Plasma clonidine concentrations were lower for block compared to the intramuscular treatment. CONCLUSIONS: The admixture of clonidine to bupivacaine plus epinephrine prolongs and enhances brachial plexus blockade. Lower clonidine plasma concentrations for block treatment strongly suggest a local effect.

Anesthesia considerations for lung volume reduction surgery.

Patient selection is of crucial importance for outcome after lung volume reduction surgery. The anesthesiologist should be involved actively in patient selection, because he or she is in charge of the treatment during the critical perioperative period. Patient history and status and results from chest radiographs, high-resolution CT scans, and catheterization of the right heart should be taken carefully into account in the patient selection process. Promising new results involving functional parameters may predict outcome objectively after lung volume reduction surgery in the future. Careful selection and preoperative preparation of patients also are important to avoid complications and keep the success rate high. The anesthesiologist's understanding of the principles involved is important for the successful conduct of lung volume reduction surgery. It is unclear if lung volume reduction surgery is superior to conventional therapy in the long run because the decline in lung function is progressive after the procedure. A multicenter trial comparing patients undergoing lung volume reduction surgery with patients with emphysema who are treated conventionally hopefully will clarify this important question in the future.

The effects of thoracic epidural analgesia with bupivacaine 0.25% on ventilatory mechanics in patients with severe chronic obstructive pulmonary disease.

UNLABELLED: Optimal analgesia is important after thoracotomy in pulmonary-limited patients to avoid pain-related pulmonary complications. Thoracic epidural anesthesia (TEA) can provide excellent pain relief. However, potential paralysis of respiratory muscles and changes in bronchial tone might be unfavorable in patients with end-stage chronic obstructive pulmonary disease (COPD). Therefore, we evaluated the effect of TEA on maximal inspiratory pressure, pattern of breathing, ventilatory mechanics, and gas exchange in 12 end-stage COPD patients. Pulmonary resistance, work of breathing, dynamic intrinsic positive end-expiratory pressure, and peak inspiratory and expiratory flow rates were evaluated by assessing esophageal pressure and airflow. An increase in minute ventilation (7.50 +/- 2.60 vs 8.70 +/- 2.10 L/min; P = 0.04) by means of increased tidal volume (0.46 +/- 0.16 vs 0.53 +/- 0.14 L/breath; P = 0.003) was detected after TEA. These changes were accompanied by an increase in peak inspiratory flow rate (0.48 +/- 0.17 vs 0.55 +/- 0.14 L/s; P = 0.02) and a decrease in pulmonary resistance (20.7 +/- 9.9 vs 16.6 +/- 8.1 cm H(2)O. L(-1). s(-1); P = 0.02). Peak expiratory flow rate, dynamic intrinsic positive end-expiratory pressure, work of breathing, PaO(2), and maximal inspiratory pressure were unchanged (all P > 0.50). We conclude that TEA with bupivacaine 0.25% can be used safely in end-stage COPD patients. IMPLICATIONS: Thoracic epidural anesthesia with bupivacaine 0.25% does not impair ventilatory mechanics and inspiratory respiratory muscle strength in severely limited chronic obstructive pulmonary disease patients. Thus, thoracic epidural anesthesia can be used safely in patients with end-stage chronic obstructive pulmonary disease.

Pulmonary artery thromboendarterectomy: a comparison of two different postoperative treatment strategies.

UNLABELLED: Pulmonary artery thromboendarterectomy (PTE) is a potentially curative surgical procedure for chronic thromboembolic pulmonary hypertension. It is, nevertheless, associated with considerable mortality caused by postoperative complications, such as reperfusion pulmonary edema (RPE) (i.e., pulmonary infiltrates in regions distal to vessels subjected to endarterectomy) and right heart failure (RHF). However, there are no reports about the influence of different postoperative treatment strategies on complications and mortality. Therefore, we compared two different treatment strategies. In Group I (n = 33), positive inotropic catecholamines and vasodilators were avoided during termination of cardiopulmonary bypass (CPB) and thereafter, and mechanical ventilation was performed with low tidal volumes < 8 mL/kg, duration of inspiration:duration of expiration = 3:1, and peak inspiratory pressures < 18 cm H(2)O. In Group II (n = 14), positive inotropic catecholamines and vasodilators were regularly used for termination of CPB and thereafter, and ventilation was performed with high tidal volumes (10-15 mL/kg) and peak inspiratory pressures up to 50 cm H(2)O. Hemodynamics, the incidence of RPE and RHF, duration of ventilation, morbidity, and mortality were recorded. Cardiac index was comparable before surgery (2.11 +/- 0.09 vs 2.08 +/- 0.09 L. min(-1). m(-2)) and 20 min after CPB (2.26 +/- 0.09 vs 2.60 +/- 0.20 L. min(-1). m(-2)). RPE occurred in 6.1% (Group I) versus 14.3% (Group II), and RHF was observed in 9.1% (Group I) versus 21.4% (Group II). Mortality was 9.1% (Group I) versus 21.4% (Group II). Thus, the avoidance of positive inotropic catecholamines and vasodilators in combination with nonaggressive mechanical ventilation after PTE was associated with a low incidence of RPE, RHF, duration of ventilation, and mortality after PTE. IMPLICATIONS: The avoidance of positive inotropic catecholamines and vasodilators in combination with nonaggressive mechanical ventilation was associated with a low incidence of reperfusion pulmonary edema and/or right heart failure after pulmonary artery thromboendarterectomy.

Lung volume reduction surgery: preoperative functional predictors for postoperative outcome.

UNLABELLED: Approximately 20% of patients undergoing lung volume reduction surgery (LVRS) exhibit no functional improvement postoperatively. Therefore, we examined whether variables characterizing ventilatory mechanics before LVRS could serve as predictors for outcome. In 32 patients undergoing LVRS, lung function, dyspnea score, and ventilatory mechanics were assessed preoperatively and 3 mo after LVRS. Ventilatory mechanics were characterized by total resistive work of breathing (WOB), mean airway resistance (Rawm), and dynamic intrinsic positive end-expiratory pressure (PEEPi,dyn). Calculations of WOB, Rawm, and PEEPi,dyn were made from measurements of airflow, volume, and esophageal pressure. Preoperative PEEPi,dyn correlated well with the increase in forced expiratory volume percent predicted (r = 0.75; P < 0.0001) and the decrease in dyspnea score (r = -0.74; P < 0.0001) after LVRS. Rawm and WOB showed inferior correlation compared with PEEPi,dyn. The examination of distinct threshold values for WOB, Rawm, and PEEPi,dyn with respect to predicting improvement resulted in a sensitivity of 93% and specificity of 88% for a cutoff point of preoperative PEEPi,dyn > or =5 cm H2O. Preoperative PEEPi,dyn correlated well with improvement in forced expiratory volume and dyspnea score after LVRS. Thus, preoperative assessment of PEEPi,dyn could improve risk to benefit stratification before LVRS. IMPLICATIONS: We examined the preoperative ventilatory mechanics of patients with emphysema undergoing lung volume reduction surgery with respect to their value in predicting outcome. Preoperative intrinsic positive end-expiratory pressure correlated well with the increase in forced expiratory volume in 1 s after surgery. Thus, this variable seems promising for improved patient selection.

Ventilatory mechanics and gas exchange during exercise before and after lung volume reduction surgery.

Many patients with emphysema are able to meet ventilatory demands during resting conditions, but they show severe limitations during exercise. To examine the effect of lung volume reduction (LVR) surgery on exercise performance and the mechanism of possible improvement, we measured ventilatory mechanics (pulmonary resistance [RL], work of breathing [WOB], dynamic intrinsic positive end-expiratory pressure [PEEPi,dyn], peak expiratory flow rate [PEFR]), breathing pattern, oxygen uptake (V O2), and carbon dioxide removal (V CO2) at rest and during cycle ergometry in eight patients before and 3 mo after LVR surgery. Ventilatory mechanics were evaluated assessing esophageal pressure and air flow. Three months after LVR surgery, the tolerated workload was doubled when compared with the preoperative value (p < 0.0005), associated with a reduction of RL (p < 0.05), PEEPi,dyn (p < 0.005), and WOB (p < 0. 005) at comparable workloads. Maximal ventilatory capacity and maximal tidal volume (VT) increased significantly (p < 0.01). Maximal V O2 increased from 474 +/- 23 to 601 +/- 16 ml/min (p < 0. 005) and maximal V CO2 from 401 +/- 13 to 558 +/- 21 ml/min (p < 0. 005), though no significant difference at comparable workloads could be observed. In conclusion, emphysema surgery leads to an improvement of ventilatory mechanics at rest and during exercise. Higher maximal VT and minute ventilation were observed, resulting in improvement of maximal V O2 and V CO2 and exercise capacity.

Clonidine added to the anesthetic solution enhances analgesia and improves oxygenation after intercostal nerve block for thoracotomy.

UNLABELLED: We evaluated the effect of adding clonidine to bupivacaine on postoperative pain control and oxygenation after intercostal nerve blockade (ICB) for thoracotomy, and attempted to distinguish a systemic from a local effect of clonidine. ICB with 2 mg/kg 0.5% bupivacaine was performed in 36 patients undergoing thoracotomy. Patients were randomized to one of three groups: 1) a control group that received bupivacaine with saline for ICB and an IM injection of saline, 2) an IM group that received bupivacaine with saline for ICB and an IM injection of 2 micrograms/kg clonidine, and 3) a block group that received bupivacaine with 2 micrograms/kg clonidine for ICB and an IM injection of saline. Blood gases, visual analog scale (VAS) scores, and analgesic demand were determined hourly for 8 h after arrival in the postoperative care unit (PCU). Patients in the block group had significantly lower VAS scores, higher arterial oxygen tension, and lower analgesic demand for the first 4 h in the PCU, compared with the two other groups. No difference was noted thereafter. We conclude that the addition of clonidine to bupivacaine for ICB leads to a short-term effect enhancing postoperative pain control and improving arterial oxygenation, probably mediated by a direct effect on the nerves. IMPLICATIONS: Severe pain after thoracotomy can lead to impaired ventilation. We studied the effect of adding clonidine to bupivacaine for intercostal nerve blockade after thoracotomy. Clonidine administered directly on the nerves enhanced analgesia and improved oxygenation for a short time compared with systemic administration or control.

Changes in ventilatory mechanics and diaphragmatic function after lung volume reduction surgery in patients with COPD.

BACKGROUND: Lung volume reduction (LVR) has recently been used to treat severe emphysema. About 25% of the volume of each lung is removed with this method. Little is known about the mechanism of functional improvement so a study was undertaken to investigate the changes in ventilatory mechanics and diaphragmatic function in eight patients after LVR. METHODS: Measurements of work of breathing (WOB), intrinsic positive end expiratory pressure (PEEPi), dynamic compliance (Cdyn), and arterial carbon dioxide tension (PaCO2) were performed on the day before surgery and daily for seven days after surgery, as well as one, three, and six months after surgery. All measurements were performed on spontaneously breathing patients, simultaneously assessing oesophageal pressure via an oesophageal balloon catheter and air flow via a tightly adjusted mask. Diaphragmatic function was evaluated by measuring oesophageal and transdiaphragmatic pressure (Pdi) preoperatively and at one, three, and six months postoperatively. RESULTS: Mean forced expiratory volume in one second (FEV1) was 23 (3.6)% predicted, and all patients were oxygen dependent before the-operation. One day after LVR the mean decrease in WOB was 0.93 (95% confidence interval (CI) 0.46 to 1.40) joule/l, the mean decrease in PEEPi was 0.61 (95% CI 0.35 to 0.87) kPa, and the mean increase in Cdyn was 182.5 (95% CI 80.0 to 284.2) ml/kPa. Similar changes were found seven days and six months after surgery. PaCO2 was higher on the day after the operation but was significantly reduced six months later. Pdi was increased three and six months after surgery. CONCLUSIONS: Ventilatory mechanics improved immediately after LVR, probably by decompression of lung tissue and relief of thoracic distension. An improvement in diaphragmatic function three and six months postoperatively also contributes to improved respiratory function after LVR.

The influence of lung volume reduction surgery on ventilatory mechanics in patients suffering from severe chronic obstructive pulmonary disease.

Recently, lung volume reduction [LVR] removal of about 20% of lung volume), has been performed to treat severe emphysema. Little is known, however, about the mechanism and time course of functional improvement, and the reasons that such patients can be tracheally extubated very early. Therefore, we studied changes in ventilatory mechanics in 12 patients after LVR. Measurements of work of breathing (WOB), intrinsic positive end-expiratory pressure (PEEPi), dynamic compliance (Cdyn), and mean airway resistance (Rawm) were performed the day before surgery, early postoperatively, and 1 and 3 mo after surgery. All measurements were performed on tracheally extubated patients, simultaneously assessing esophageal pressure via esophageal balloon catheter and air flow via tightly adjusted mask. Standard spirometry was assessed pre-operatively and 1 and 3 mo postoperatively. The patients presented with forced expiratory volume in 1 s (FEV1), of 670 +/- 50 mL and pathological values of WOB and PEEPi. All patients were successfully tracheally extubated within 5 h postoperatively. Immediately thereafter, a marked and sustained decrease in WOB, PEEPi, and Rawm was noted, as well as an increase in Cdyn. Ventilatory mechanics improved immediately after LVR, probably due to decompression of lung tissue, thereby enabling successful tracheal extubation.

Early postoperative stress: video-assisted wedge resection/lobectomy vs conventional axillary thoracotomy.

Postoperative pain is a major cause of ineffective breathing after lung surgery, predisposing patients to hypoxemia. Because potent analgesics like opioids depress ventilation and other analgesic techniques are time-consuming, efficient postoperative pain therapy is difficult. Therefore, a less painful surgical approach could be beneficial. Forty-seven patients with diagnosis of a pulmonary nodule were prospectively studied. Patients were assigned to a video-assisted thoracic surgery (VATS) group (n=22) or a group undergoing axillary thoracotomy (n=25). Visual analogue scale (VAS) scores, plasma glucose levels, plasma epinephrine and plasma norepinephrine levels, as well as arterial oxygen (PaO2) and carbon dioxide (PaCO2) tension were determined the day before surgery, and 3, 15, 24, 48, and 72 h after surgery. Postoperative piritramide (a synthetic morphine compound) demand was recorded. VAS values were significantly lower (p<0.05) during the whole observation period in the VATS group. Significantly higher epinephrine levels were observed 3 and 15 h after surgery (267.4 +/- 28 vs 111.8 +/- 13 ng/L; p<0.01; and 176.6 +/- 46.5 vs 96 +/- 14.5 ng/L; p<0.05) in the thoracotomy group, whereas there was no significant difference in norepinephrine (correction of norephinephrine) levels. Piritramide demand was significantly (p<0.05) reduced in the VATS group throughout the whole observation period. There was no difference in PaCO2 values but PaO2 Values were higher in the VATS group over 72 h, with maximum differences occurring at 15 h after operation: 60.9 +/- 1.9 vs 49.2 +/- 2.4 mm Hg (p<0.01). In conclusion, the videoendoscopic approach is associated with less postoperative pain and better oxygenation than traditional surgical approaches.