Lobar volume reduction surgery: a method of increasing the lung cancer resection rate in patients with emphysema

BACKGROUND

Guidelines on patient selection for lung cancer resection identify a predicted postoperative forced expiratory volume in 1 second (ppoFEV(1)) of <40% as a predictor of high risk. Experience with lung volume reduction surgery suggests that ppoFEV(1) may be underestimated in those with concomitant emphysema.

METHODS

Anatomical lobectomy was performed in 29 patients with a resectable lung cancer within a poorly perfused, hyperinflated emphysematous lobe identified by radionuclide perfusion scintigraphy and computed tomographic scanning. Perioperative changes in spirometric parameters at 3 months were compared in 14 patients (group A) of mean age 69 years (range 48-78) with ppoFEV(1) <40% (mean (SD) 31.4 (7)%) and 15 patients (group B) with ppoFEV(1) >40% (mean (SD) 47 (5)%). The correlation between predicted and actual postoperative FEV(1) was also assessed.

RESULTS

In group B there was a significant perioperative reduction in FEV(1) (p=0.01) but in group A FEV(1) did not change significantly after lobectomy (p=0.87); mean difference in perioperative change between groups A and B 331 ml (95% CI 150 to 510). Despite the difference in ppoFEV(1) between the groups, there was no difference in actual FEV(1) at 3 months. In-hospital mortality was 14% in group A and zero in group B, but at a median follow up of 12 (range 6-40) months there was no difference in survival between the groups.

CONCLUSIONS

Selection for lung cancer resection in patients with emphysema using standard calculations of ppoFEV(1) may be misleading. The effect of lobar volume reduction allows for an extension of the selection criteria.

Introducing ropivacaine into a department's epidural analgesic practice. Improving acute pain service practice

The results of introducing a new licensed local anaesthetic drug, ropivacaine, into routine practice were evaluated by measuring the efficacy and adverse effects of patient controlled epidural analgesia (PCEA), using ropivacaine 2 mg/ml (R), or the mixtures in current use: fentanyl 5 (micrograms/ml with bupivacaine 1 mg/ml (BF5) and fentanyl 10 (micrograms/ml) with bupivacaine 1 mg/ml (BF10). All patients were nursed on general wards after surgery. For two months, 102 consecutive patients were studied. Pain scores at rest were significantly better in the fentanyl and bupivacaine groups, (mean rank R: 35.5, BF5: 22.7, BF10: 26.9, P < 0.05). There was a significant correlation between patient controlled boluses and pain at rest and (p < 0.001), and pain on moving (p < 0.001). Nausea and vomiting was worse in the BF10 (p < 0.05). Older patients demanded less analgesia (p < 0.001). Postoperatively BF5 provided better pain relief with trends demonstrating fewer side-effects and complications than BF10 or R. We now use fentanyl 5 (micrograms/ml and bupivacaine 1 mg/ml as our standard epidural infusion mixture.

Breath interval as a measure of dynamic opioid effect

We measured breath interval to characterize the time course of opioid effect in anaesthetized patients breathing spontaneously during knee replacement surgery with concurrent regional nerve blockade. Breath interval was recorded before and after a single dose of fentanyl 0.75 microgram kg-1 i.v. Breath interval was measured between the start of successive inspirations, identified by a decrease in carbon dioxide concentration, sampled at the laryngeal mask connection. Nineteen patients were admitted to the study, of whom nine were withdrawn (there was a recording failure for one patient, five patients had inadequate block and three were excessively depressed by the fentanyl). Using MKMODEL software, the mean (SD) dynamic elimination half-life and dynamic mean brain residence time of fentanyl were 15.3 (7.8) and 24.1 (8.1) min, respectively. The times to detection of change from baseline, and peak effect of fentanyl on breath interval were 0.9 (0.6) and 5.2 (1.4) min, respectively. Breath interval increased from 2.9 (1.0) s to a maximum of 9.0 (5.7) s. There were no differences between the time course of changes in breath interval and end-tidal carbon dioxide concentrations. End-tidal carbon dioxide concentrations increased from a baseline of 6.6 (0.9)% to a peak of 8.2 (0.8)%. Breath interval was a useful and reproducible method of monitoring the duration of opioid effect in anaesthetized patients breathing spontaneously when surgical stimulation was not affecting the CNS. The data provide information on the duration of action of fentanyl and could guide dosage.

Remifentanil and tramadol

The lack of analgesic efficacy limits tramadol as a sole agent to treat severe pain after surgery. However, it has a relative lack of respiratory depressant and constipating effects compared with morphine and codeine, and does not share the propensity of nonsteroidal anti-inflammatory drugs to provoke asthma, gastrointestinal mucosal damage and renal impairment. It may well have a place in the management of pain after surgery, in combination with another drug, such as paracetamol, or after control of the worst of pain after surgery by a regional local anaesthetic technique.

Toward the paperless hospital?

This report describes an ethnographic study of document use by anaesthetists. In doing so, it focuses on the role of the preoperative risk assessment form as used in anaesthetic practice at a cardiothoracic hospital, and considers what would be the advantages and disadvantages of shifting the paper into the electronic form. Evidence from this case study is used to comment on how the practical use of documents by medical professionals can be fundamentally at odds with how the organization at large would like to use them. We argue that hospital trusts need to take into account this practical perspective in order to build effective, on-line document systems.

Remifentanil and pulmonary extraction during and after cardiac anesthesia

We measured the apparent blood clearance and pulmonary extraction ratio of remifentanil in 10 adult patients undergoing elective myocardial revascularization for the first time with hypothermic cardiopulmonary bypass (CPB). Patients received continuous infusions of remifentanil 1.0, 1.5 or 2.0 microg x kg(-1) x min(-1). After surgery, remifentanil was infused at 1.0 microg x kg(-1) x min(-1) in all patients. Remifentanil concentrations were measured in pulmonary and radial artery blood by gas chromatography with high resolution mass spectrometry before and after CPB and 165 min (60 SD) after surgery. Cardiac output was measured by thermodilution at the time of blood sampling. The mean pulmonary extraction ratio of remifentanil was 5.7% (13.1% SD), which was not significantly different from zero. However, pulmonary extraction ratio was related inversely to the pulmonary artery hydrogen ion concentration and directly to the percent of nonionized form of the base in the pulmonary artery. Remifentanil concentrations in pulmonary and radial artery blood were related directly to infusion rate, but not to duration of infusion. There was no evidence of accumulation or sequestration. Mean apparent blood remifentanil clearance was 2.03 L/min (0.35 SD) and, in contrast to remifentanil pulmonary extraction ratio, was related directly to cardiac index and oxygen delivery. Increased tissue perfusion increased blood remifentanil clearance. We found predictable blood remifentanil levels with no evidence of accumulation or pulmonary extraction.

Co-induction of anaesthesia: the cardiac patient

Cardiac patients pose special problems to the anaesthetist because of their underlying disease and the nature of the corrective surgery. Information about new methods of induction of anaesthesia obtained in fit patients may not be applicable directly to patients with heart disease. More suitable are patients undergoing cardioversion. Titrating intravenous induction agents to response elicited appears to be more important than the agent used, although it is possible to inject too slowly with drugs whose offset of action is by distribution. Anaesthetic agents alone are not sufficient to ablate the response to tracheal intubation, skin incision and sternotomy. Balancing induction of anaesthesia with small doses of opioid can obtund the haemodynamic responses. The effects of a drug used solely for induction of anaesthesia are unlikely to be present at the end of 3 or 4 h of surgery. However, this is not the case with agents used to maintain anaesthesia if early extubation after anaesthesia is practised. Reports of anaesthetic techniques for cardiac surgery tend to give total doses used rather than the timing and dose of the constituent agents. At Papworth Hospital, Cambridge, UK, after opioid premedication, midazolam sedation is used during insertion of some, or all, vascular cannulae. Two main techniques then exist. Either an intravenous or volatile anaesthetic agent is started immediately, supplemented by an opioid and muscle relaxant, or anaesthesia is induced with opioid and relaxant and the anaesthetic agent is begun only after transfer to the operating theatre, just before skin preparation. Either way, the end-point of induction of anaesthesia is difficult to discern in heavily premedicated patients with midazolam sedation.

Enoximone and warming after hypothermic cardiopulmonary bypass

In a randomized, controlled study of 24 patients undergoing myocardial revascularization, we found that enoximone 0.5 mg kg-1 i.v., followed by 5 micrograms kg-1 min-1, when rewarming after hypothermic cardiopulmonary bypass, prevented subsequent cooling of the periphery after transfer to the intensive care unit. Skin surface temperatures on the foot increased by mean 0.33 (SD 0.5) degree C h-1 in the enoximone group, but decreased by 0.43 (0.4) degree C h-1 in the control group until core temperature had increased to 37 degrees C (P < 0.001); only then did peripheral temperatures begin to increase in the control group. Enoximone did not merely redistribute heat from the core to the periphery. The capacity to transfer heat by the circulation rather than the ability to generate heat in the core appeared to limit body warming in the ICU after hypothermic cardiopulmonary bypass.

Convective warming after hypothermic cardiopulmonary bypass

In a randomized, controlled study, we found that convective warming after hypothermic cardiopulmonary bypass did not accelerate the rate of warming of the body core or the time to tracheal extubation. The relationship between body core and shell temperature, however, was affected. In all patients inadequate time spent rewarming on cardiopulmonary bypass prolonged body core warming time and time to tracheal extubation. Rate of warming of body core was inversely related to body mass index. Convective warming was delivered using BairHugger (Augustine Medical Inc., MN, USA) and Warm Touch (Mallinckrodt Medical UK Ltd, Northampton, UK) blankets. There was no difference between the performance of each blanket when powered by the BairHugger 500 power unit set at its medium setting of 38 degrees C, and when chest drain and radial artery cannulation sites were left exposed for observation.

Efficacy of continuous intercostal bupivacaine for pain relief after thoracotomy

We studied 20 patients undergoing thoracotomy, in a double-blind, placebo-controlled crossover trial of intercostal bupivacaine. Bupivacaine 0.25% was infused at 5 ml h-1 through each of two catheters placed in the intercostal space at operation. Mean (95% confidence limits) 24-h requirements for morphine from a patient-controlled analgesia device were 29 (22-37) mg during bupivacaine infusion and 44 (32-57) mg during saline infusion (P = 0.04). Patients also recorded significantly smaller visual analogue scores for pain during bupivacaine infusion. There were no adverse effects related to the intercostal infusion of bupivacaine. We conclude that bupivacaine, infused through catheters placed during thoracotomy in the adjacent intercostal spaces, is a useful adjunct to systemic opioid analgesia.

Transdermal fentanyl for the relief of pain after upper abdominal surgery

Transdermal fentanyl (n = 22) was compared with placebo (n = 18) in a double-blind study of pain after upper abdominal surgery. All patients also received i.v. morphine on demand for supplementary analgesia. The transdermal systems were applied 2 h before induction of anaesthesia and remained in situ for 24 h. After operation, pain scores were significantly lower and peak expiratory flow rates significantly higher in the transdermal fentanyl group, who demanded significantly less morphine than the control group. Mean plasma fentanyl concentrations at 12 and 24 h were within the therapeutic range (1.5 and 2.0 ng ml-1, respectively).

Plasma fentanyl concentrations during transdermal delivery of fentanyl to surgical patients

Plasma fentanyl concentrations were measured during and after transdermal fentanyl delivery in groups of patients undergoing general surgery. At 8 and 12 h, concentrations did not differ from those observed in a matched group of patients receiving fentanyl by i.v. infusion. At 24 h, concentrations were significantly lower in one of the transdermal groups. Plasma fentanyl clearance did not differ significantly between the groups. Plasma fentanyl concentrations decreased slowly after removal of the transdermal system.

Concurrent drug therapy in patients undergoing surgery

In a retrospective study of 57,176 patients and a prospective study of 216 patients undergoing surgery, 24-32% of patients were receiving some concurrent medication. Between 10 and 16% were taking drugs for cardiovascular disease. Of these, only 71% had their normal medication prescribed before surgery and only 41% received their drugs on the day of surgery.

Pain relief after surgery

Relief of pain after surgery remains poor for the majority of patients. The pain is unpleasant, and is associated with arterial hypoxaemia, venous thrombosis, myocardial ischaemia and a more florid hormonal response to surgery. Regional analgesia, systemic, subarachnoid or extradural opioids and antiprostaglandin drugs are all used to treat pain after surgery. Systemic opioids are used usually, because regional and axial techniques are labour intensive and antiprostaglandin drugs ineffective. Opioids given orally undergo extensive first pass metabolism and intramuscular doses are absorbed unpredictably. Intravenous administration avoids both problems and excellent results have been obtained using Patient Controlled Analgesia devices, but these machines are expensive. A simple regimen suitable for application to large numbers of surgical patients is required. Continuous infusion of fentanyl 100 micrograms h-1 IV begun two hours before surgery and supplemented by a single bolus dose of fentanyl 100 micrograms IV provided an effective background of analgesia.

Adverse effects of opioid analgesic drugs

Opioids were available in clinical practice since before the birth of modern anaesthesia--Setürner isolated morphine in 1806. They have a record of safety which is reflected in their high therapeutic ratios, especially the synthetic opioids introduced recently (table III). The most serious immediate adverse effect, respiratory depression, is a predictable effect related closely to analgesia. It is fortunate for anaesthetists who use opioids regularly, that recognition and treatment of respiratory problems are an integral part of their craft and that opioid antagonists are effective in reversing respiratory depression.

Pharmacokinetics of fentanyl during constant rate i.v. infusion for the relief of pain after surgery

Forty-five patients in four groups undergoing orthopaedic, upper abdominal, prolonged or cardiac surgery received a constant rate i.v. infusion of fentanyl 100 micrograms h-1, for 24 h starting 2 h before surgery. A single bolus dose was given i.v. at the induction of anaesthesia. Plasma fentanyl concentrations, measured by radioimmunoassay were between 1 and 3 ng ml-1 until the infusions were discontinued. Clearance of fentanyl was decreased in the cardiac surgery group only. The elimination half-life was 7.3-9.7 h. This simple regimen produced effective analgesia.

Effect of induction of anaesthesia with etomidate on corticosteroid synthesis in man

The effects of a single bolus dose of etomidate 0.3 mg kg-1 or thiopentone 5 mg kg-1, on the synthesis of corticosteroid hormones and adrenocorticotrophic hormone (ACTH), were compared for 24 h in 12 patients, undergoing minor surgery under general anaesthesia. Following opioid premedication i.m. and general anaesthesia, plasma cortisol concentrations decreased transiently within the first hour of anaesthesia in all 12 patients. The six patients who received etomidate had statistically higher plasma 11-deoxycorticosterone concentrations at 4 and 24 h than those who had received thiopentone (P less than 0.01). Throughout the study, no difference in plasma cortisol, corticosterone or ACTH concentrations were found between the two groups. We have demonstrated a biochemical effect of a single bolus dose of etomidate consistent with incomplete inhibition of adrenocortical mitochondrial 11 beta-hydroxylase activity, but no clinically significant adrenocortical suppression.