Anaesthetic management of patients undergoing lung volume reduction surgery for treatment of severe emphysema.

Lung volume reduction surgery can improve lung function in patients with emphysema. We report our anaesthetic experience, problems and the physiological data of eight patients. Our aims were prevention of air trapping and air leaks, good analgesia and early recovery and mobilization. We were able to achieve these aims using pressure limited ventilation, lumbar epidural diamorphine, propofol infusions and intensive physiotherapy. Hypoxia during one-lung ventilation was the main intraoperative problem. Air leaks, infection and pulmonary hypertension were the main postoperative problems.

Effect of acute alterations in afterload on left ventricular function in patients with combined coronary artery and peripheral vascular disease.

OBJECTIVE: To assess the effect of acute alterations in afterload by aortoiliac clamping, during peripheral vascular surgery, on left ventricular function. DESIGN: Prospective examination of the left ventricular long axis and transmitral Doppler flow preoperatively and intraoperatively; before aortic clamping, during clamping and 5 min, 15 min, and 5 days after unclamping. SETTING: A tertiary referral centre for cardiac and vascular disease equipped with invasive and non-invasive facilities. PATIENTS: 20 patients (11 men; mean (SD) age 61 (8) years) with significant aortoiliac disease and documented coronary artery disease and 21 normal controls of similar age. RESULTS: Preoperatively: long axis function was abnormal compared with that in normal controls. In systole total long axis excursion and peak shortening rate were reduced, onset of shortening delayed, and there was pre-ejection lengthening (P < 0.001). In diastole there was abnormal shortening during isovolumic relaxation, delaying the onset of long axis lengthening (P < 0.001). Peak lengthening rate was also reduced and A wave excursion increased (P < 0.001). Transmitral Doppler showed increased A wave velocity and reduced peak E/A diastolic flow velocities ratio (P < 0.001). Intraoperatively: preclamping results did not differ from those before operation. With clamping the extent of systolic and diastolic abnormalities promptly increased as to a lesser extent did those of transmitral flow velocity, although heart rate and blood pressure did not change significantly. Total long axis excursion and A wave amplitude were more reduced by aortic than iliac clamping, whereas the onset of lengthening was more delayed and the lengthening velocity more reduced with iliac clamping. Some 5 min after unclamping systolic long axis function had already returned towards normal; total excursion increased, as did the peak shortening rate, and the onset of shortening became less delayed (P < 0.001). In diastole the delayed onset of lengthening regressed, its lengthening velocity increased, and A wave excursion fell (P < 0.001). Early diastolic transmitral flow velocity also increased. This improvement in systolic and diastolic long axis function had progressed 15 min after unclamping but showed no further change at 5 days. At 5 days after operation, however, systolic and diastolic measurements had improved compared with those preoperatively. CONCLUSION: Resting left ventricular long axis function is abnormal in patients with combined coronary artery disease and peripheral vascular disease. It is unaffected by anaesthesia but deteriorates with aortic or iliac clamping, although blood pressure remains unchanged. It promptly improves with unclamping after successful peripheral arterial reconstruction. Thus, even in apparently stable coronary artery disease, resting subendocardial function is labile, showing pronounced alterations with changing after-load, even when arterial pressure itself does not change.

Commentary: mannitol: molecule magnifique or a case of radical misinterpretation?

Reactive oxygen species are constantly formed in biological systems. When production exceeds antioxidant protection, oxidative stress leading to molecular damage occurs. The most reactive ROS in biological systems is the hydroxyl radical which damages adjacent molecules at diffusion controlled rates. The possibility of preventing such chemistry inside cells with therapeutic doses of mannitol at present seem remote.

Use of endotracheal silicone stents for relief of tracheobronchial obstruction.

In this article we describe our initial experience with bifurcated and longitudinal silicone stents that can be inserted entirely endoscopically. A total of 10 patients were stented; half had upper airways obstruction resulting from malignant disease and half had anastomotic obstruction after single-lung (3 patients), double-lung (1 patient), or heart-lung transplantation (1 patient). All patients derived immediate relief of life-threatening stridor. Stents were in place for between 5 days and 2 1/2 years (mean, 232.9 days). In the patients with malignant disease, the stents have provided effective relief from stridor for the remainder of their lives. In the transplant recipients, the medium-term results are encouraging, with the stents providing effective relief from stridor, although the longitudinal stents have been associated with distal migration, requiring that the stents be replaced on up to five occasions. The stents have not been associated with infection in the nonimmunosuppressed patients, and during the relatively short follow-up period there has been no tissue reaction to the material.

Effect of temperature on rate of left ventricular pressure fall in humans.

The time constant (T) of left ventricular pressure fall is widely used as an index of ventricular "relaxation". It is not known whether its rate limiting step is deactivation, an enzymic energy consuming reaction whose rate is therefore sensitive to temperature, or elastic recoil. To distinguish between these possibilities, the time constant was measured by simple logarithmic (Tlog) and exponential (Texp) methods in 12 patients during cooling before coronary artery grafting. Ventricular loading conditions were altered by transfusion from bypass to maintain arterial and left atrial pressures constant in individual patients, though heart rate fell from 86 (8.4) to 68 (10) beats/min. Tlog increased from 49 (10) ms mean (SD), at 37 degrees C to 86 (15) ms at 31 degrees C, and Texp from 63(14) at 37 degrees C to 112 (23) ms at 31 degrees C with intermediate values at 34 degrees C. Texp proved sensitive to "noise" at low temperatures, but the overall change in Tlog with temperature was 9% per degree C--considerably less than that observed experimentally for the rate of tension decline of isolated myocardium, and possibly itself an overestimate because of the concomitant fall in heart rate. The relatively small effect of temperature on Tlog in humans, associated with a considerable load sensitivity appearing under hypothermic conditions, does not favour simple dependence on deactivation as the rate limiting step of left ventricular pressure fall, but suggests that its determinants may be complex.

Tracheopathia osteochondroplastica. A cause of unexpected difficulty in tracheal intubation.

A 60-year-old man presented for aortocoronary saphenous vein grafting; tracheal intubation was found to be difficult before surgery. Bronchoscopy at the time suggested tracheal carcinoma, but subsequent biopsy of the trachea demonstrated tracheopathia osteochondroplastica. The condition is described and its implications for anaesthetists are discussed.

Respiratory mass spectrometry during general anaesthesia.

The performance of a respiratory mass spectrometer, modified commercially for use during general anaesthesia, has been evaluated. Stability and linearity proved satisfactory for monitoring respiratory gases and accurate measurement was possible when the inspired concentration of all gases was less than 80%. The system has been installed centrally in a three-room operating theatre suite and the selection of long sampling probes which permit an adequate response time for all gases is discussed.

Measurement of metabolic gas exchange during anaesthesia. A method using mass spectrometry.

A method is described for measuring metabolic gas exchange during general anaesthesia using a respiratory mass spectrometer, a mixing box and two inert tracer gases. Measurement of inspired and expired minute volume is possible to within 2%; oxygen consumption, carbon dioxide output and respiratory quotient can be measured to within 10%.

Pulmonary function after prolonged mechanical ventilation with high concentrations of oxygen.

The mortality and morbidity resulting from mechanical ventilation with high concentrations of inspired oxygen has been investigated in two groups of patients. Ninety-one patients requiring mechanical ventilation for pulmonary disease included six (group 1) in whom death was attributed directly to respiratory failure but only three in whom oxygen toxicity might have been relevant. Review of the clinical and postmortem findings suggests that oxygen was probably not a contributory factor in two of these three. A second group of 16 patients who survived prolonged mechanical ventilation with oxygen in excess of 40% (average 14.5 days) included five who had been ventilated with 75% oxygen or more for an average of 38 hours. Lung function studies carried out on this second group of patients approximately one year later demonstrated that all but three had significant defects in either ventilation, gas transfer, or both. Oxygen toxicity was thought to be a likely cause in one and a possible contributory factor in three more. It is suggested that the adverse effects of oxygen on the alveolar epithelium are rarely of practical importance in hypoxaemic patients requiring mechanical ventilation but disturbance to the pulmonary defences against infection may well be of greater importance. The fear of inducing oxygen toxicity should not be allowed to interfere with the relief of arterial hypoxaemia in ventilated patients.

Muscle blood flow and rate of recovery from pancuronium neuromuscular blockade in dogs.

The effect of changes in muscle blood flow on the rate of recovery from neuromuscular block produced by pancuronium was investigated in dogs, and were shown to be independent variables. The significance of this finding in relation to recent work on blood concentrations of the drug and on the pharmacodynamics of the drug is discussed.