Comparison of two commonly used reference materials for exercise bicycle tests with a Swedish clinical database of patients with normal outcome.

BACKGROUND: Reference values for working capacity, blood pressure, heart rate, perceived exertion, etc. during bicycle exercise tests have been sought after for many years. This is because earlier commonly used reference values for physical work capacity have been either too low or too high when compared to the clinical experience of several Swedish departments of clinical physiology. The aim of the study was to compare two commonly used reference materials with normal outcomes from a clinical database. METHODS: Data from a clinical database of standardized exercise tests in Kalmar, Sweden, between 2004 and 2012, and having been judged as normal, were divided into 5-year categories of 5-10 to 75-80 years of age covering people from 7 to 80 years of age. RESULTS: Maximal working capacity (Wmax ), maximal heart rate, maximal systolic blood pressure and maximal perceived exertion are presented for each of the 15 age categories. Regression equations are also presented for each sex with age and height as independent predictors. Quantitative comparisons of Wmax are calculated for the three materials and possible explanations discussed. CONCLUSIONS: Values of Wmax lie between the two reference materials most commonly used in Sweden. In addition, the present material covers subjects aged 7-19 years.

Muscle blood flow response to mental stress and adrenaline infusion in man: microdialysis ethanol technique compared to (133)Xe clearance and venous occlusion plethysmography.

BACKGROUND AND AIM: Adrenaline, administered locally by microdialysis in skeletal muscle, causes vasoconstriction around the microdialysis catheter. This is contrary to the vasodilation that normally occurs when adrenaline is infused intravenously or intra-arterially. The hypothesis was tested that vasoconstriction, measured by microdialysis, would not occur with two interventions causing increased plasma levels of adrenaline, mental stress and intravenous adrenaline infusion (0.1 nmol kg(-1) min(-1)). METHODS: Twenty-four men (27 +/- 1.6 years) underwent these interventions. Blood flow was determined by the microdialysis ethanol technique and (133)Xe clearance (gastrocnemius muscle, medial head) and by venous occlusion plethysmography (calf). RESULTS: The ethanol outflow/inflow ratio, which is inversely related to blood flow, decreased to 92.0 +/- 3.4% of basal, P = 0.014 (mean +/- SEM, n = 16) during the mental stress test, but increased to 108.3 +/- 2.2% of basal, P = 0.001 (n = 16) during the adrenaline infusion. The latter increase was abolished when adrenaline was infused during alpha-receptor blockade by phentolamine. On the contrary, by (133)Xe clearance and venous occlusion plethysmography, blood flow increased during both interventions; 2.0-1.7-fold (mental stress) and 1.3-1.4-fold (adrenaline infusion), respectively, P<0.05. CONCLUSION: Adrenaline causes vasoconstriction in skeletal muscle when blood flow is measured with the microdialysis ethanol technique, irrespective of the mode of administration. The discrepant blood flow result obtained with the microdialysis ethanol technique might, at least partly, be explained by differential diffusion properties of ethanol and (133)Xe. An additional or alternative explanation might be that an inserted microdialysis catheter shifts the balance of vasoconstrictor and vasodilator effects of adrenaline in skeletal muscle.

Oxygen supplementation increases glucose tolerance during euglycaemic hyperinsulinaemic glucose clamp procedure in patients with severe COPD and chronic hypoxaemia.

Investigations in chronic obstructive pulmonary disease (COPD) patients have shown impaired glucose tolerance in hypoxic COPD patients, compared with COPD patients with normal arterial blood gases. In healthy subjects, hypoxaemia or stay at altitude, have been shown to alter glucose metabolism. At altitude the effect seems to be dependent on duration of stay. A short stay is associated with insulin resistance, a longer stay gives rise to increased glucose uptake. The euglycaemic hyperinsulinaemic glucose clamp technique is a method to study glucose tolerance and enables determinations of glucose clearance in peripheral tissues. We investigated six COPD patients [forced expiratory volume in 1 s 0.7 +/- 0.2 l (mean +/- SD)] with chronic hypoxaemia (PaO(2) 7.9 +/- 0.6 kPa at rest, breathing air), with and without oxygen supplementation, using the glucose clamp technique. Net peripheral glucose uptake was 5.5 +/- 1.2 and 7.1 +/- 1.6 mg (kg*min)(-1) (+29%) breathing air and supplemental oxygen, respectively (P = 0.03). The tissue sensitivity to insulin increased 32% (P = 0.03) with oxygen supplementation. The results indicate that normalization of oxygen saturation in COPD patients with chronic hypoxaemia may have an immediate effect on glucose tolerance and tissue sensitivity to insulin in these patients.

Myocardial metabolism before and after valve replacement for aortic stenosis.

AIM: Post ischemic disturbances of myocardial metabolism that may contribute to postoperative heart failure and are accessible to metabolic treatment have been identified early after coronary surgery. Knowledge derived from these studies may not be applicable to other patient groups. Therefore we studied myocardial energy metabolism in patients operated for isolated aortic stenosis. METHODS: Twenty patients undergoing isolated aortic valve replacement (AVR) because of aortic stenosis without significant regurgitation were studied before and immediately after surgery. Myocardial uptake of oxygen and energy substrates was assessed with coronary sinus catheter technique. RESULTS: Free fatty acids (FFA) were the main source of myocardial energy before and after AVR. A significant uptake of lactate was only recorded preoperatively. A significant uptake of glutamate of the same magnitude as previously described in coronary patients was found pre- and postoperatively. Postoperatively a relative decrease of myocardial oxygen extraction ratio (P<0.001) and oxygen consumption (P=0.14) by approximately 20% was observed. CONCLUSION: Preoperative and postoperative metabolic adaptation with substantial uptake of glutamate, previously claimed to be due to chronic or repetitive ischemia, was demonstrated. The results indicate that oxidative metabolism had not fully recovered when the procedure was completed. However, the potentially unfavorable postoperative metabolic state with predominant reliance on FFA as energy source was out-balanced by the unloading effect of AVR with a reduction in myocardial oxygen extraction.

Lung perfusion scintigraphy prior to lung volume reduction surgery.

PURPOSE: The aim of this study was to evaluate whether lung perfusion scintigraphy (LPS) contributes to the preoperative classification of emphysema heterogeneity in patients undergoing LVRS (lung volume reduction surgery) compared to classification based only on computed tomography (CT). MATERIAL AND METHODS: Forty-five potential candidates for LVRS were examined with CT and LPS. The distribution of emphysema within the lungs was visually classified into three categories: markedly heterogeneous, intermediately heterogeneous, or homogeneous. The results of the two imaging techniques were compared to an objective, CT-based computerized classification of heterogeneity. RESULTS: Visual evaluation of all 90 lungs resulted in 50 correct classifications based on CT, in 40 based on LPS and in 68 correct classifications based on the combination of CT and LPS. The combination was superior to CT alone (p<0.01) in classification of emphysema heterogeneity. There was no significant difference between the evaluations based on either CT or LPS. CONCLUSION: The combined information from CT and LPS are superior in assessing emphysema heterogeneity prior to LVRS.

Myocardial uptake and release of substrates in type II diabetics undergoing coronary surgery.

OBJECTIVE: Knowledge about myocardial metabolism in diabetic patients is limited, and even more so in association with myocardial ischaemia and cardiac surgery. This study investigates myocardial substrate utilization in type II diabetic patients after elective coronary artery bypass graft surgery (CABG). DESIGN: Myocardial substrate utilization in 10 type II diabetic patients was assessed during the first hours after elective CABG with the coronary sinus catheter technique. RESULTS: No significant myocardial uptake of carbohydrates was observed. Free fatty acids were extracted throughout the study period but uptake was not related to arterial levels. As arterial levels of beta-hydroxybutyric acid tended to increase a significant myocardial uptake emerged. The average extraction rate of beta-hydroxybutyric acid was 31% with a peak of 42%. A comparable extraction rate of glutamate was also found whereas alanine was released from the heart. CONCLUSION: Free fatty acids were the main source of energy for the heart whereas uptake of carbohydrates was restricted. The high extraction rates of beta-hydroxybutyric acid and glutamate suggest an adaptive role for these substrates during this unfavourable metabolic state for the post-ischaemic diabetic heart.

Effects of high-dose glucose-insulin-potassium on myocardial metabolism after coronary surgery in patients with Type II diabetes.

The effects of glucose-insulin-potassium (GIK) on cardiac metabolism have been studied previously in non-diabetic patients after cardiac surgery. Although patients with diabetes mellitus can be expected to benefit most from such treatment, the impact of GIK in diabetic patients undergoing cardiac surgery remains unexplored. Therefore the present study investigates the effects of high-dose GIK on myocardial substrate utilization after coronary surgery in patients with Type II diabetes. A total of 20 patients with Type II diabetes undergoing elective coronary surgery were randomly allocated to either post-operative high-dose GIK or standard post-operative care, including insulin infusion if necessary to keep blood glucose below 10 mmol/l. Myocardial substrate utilization was studied using the coronary sinus catheter technique. Haemodynamic state was assessed with the aid of Swan-Ganz catheters. High-dose GIK caused a shift towards carbohydrate utilization, with significant lactate uptake throughout the study period and significant uptake of glucose after 4 h. Arterial levels of non-esterified fatty acids and beta-hydroxybutyric acid decreased, and after 1 h no significant uptake of these substrates was found. Increases in the cardiac index and stroke volume index were found in patients treated with high-dose GIK. A decrease in systemic vascular resistance was found both in the control group and in the high-dose GIK group. We conclude that high-dose GIK can be used in diabetic patients after cardiac surgery to promote carbohydrate uptake at the expense of non-esterified fatty acids and beta-hydroxybutyric acid. This could have implications for treatment of the diabetic heart in association with surgery and ischaemia.

Exercise and insulin cause GLUT-4 translocation in human skeletal muscle.

Studies in rodents have established that GLUT-4 translocation is the major mechanism by which insulin and exercise increase glucose uptake in skeletal muscle. In contrast, much less is known about the translocation phenomenon in human skeletal muscle. In the current study, nine healthy volunteers were studied on two different days. On one day, biopsies of vastus lateralis muscle were taken before and after a 2-h euglycemic-hyperinsulinemic clamp (0.8 mU. kg(-1). min(-1)). On another day, subjects exercised for 60 min at 70% of maximal oxygen consumption (VO(2 max)), a biopsy was obtained, and the same clamp and biopsy procedure was performed as that during the previous experiment. Compared with insulin treatment alone, glucose infusion rates were significantly increased during the postexercise clamp for the periods 0-30 min, 30-60 min, and 60-90 min, but not during the last 30 min of the clamp. Plasma membrane GLUT-4 content was significantly increased in response to physiological hyperinsulinemia (32% above rest), exercise (35%), and the combination of exercise plus insulin (44%). Phosphorylation of Akt, a putative signaling intermediary for GLUT-4 translocation, was increased in response to insulin (640% above rest), exercise (280%), and exercise plus insulin (1,000%). These data demonstrate that two normal physiological conditions, moderate intensity exercise and physiological hyperinsulinemia approximately 56 microU/ml, cause GLUT-4 translocation and Akt phosphorylation in human skeletal muscle.

Pulmonary embolism: a follow-up study of the relation between the degree of right ventricle overload and the extent of perfusion defects.

OBJECTIVES: To describe the course of changes in perfusion lung scintigraphy (LS) after acute pulmonary embolism (PE) and test the hypothesis that patients with persistent pulmonary hypertension (PH)/right ventricle (RV) dysfunction after acute PE can be differentiated from those without through larger perfusion defects (PDf) on LS. Design. Prospective, one-year follow-up study with repeated LS and echocardiography-Doppler investigations. SETTING: Single centre, University Hospital. SUBJECTS: Patients with clinical suspicion of acute PE with a diagnosis confirmed by LS and/or pulmonary angiography and able to undergo repeated investigations. Of the 78 patients included, a six-week follow-up was completed in 67 and a one-year follow-up in 64. MAIN OUTCOME MEASURES: Time course of PDf in relation to time course of pulmonary artery systolic pressure (PAsP) and RV function. RESULTS: Initially, PDf decreased exponentially, until the beginning of a stable phase, which was achieved within 54 days for 90% of the patients and within 148 days for all. The temporal relation for the regress of PDf and decrease in PAsP was loose. Patients with persistent PDf suffered PH/RV dysfunction more often than those without. However, the variability in the degree of haemodynamic changes for a given extent of PDf was large. CONCLUSIONS: After acute PE, LS is of use for the identification of the group of patients that may have persistent PH/RV dysfunction. However. since the identification of individual patients is uncertain, LS cannot replace echocardiography-Doppler in the identification of persistent PH/RV dysfunction after acute PE.

Pulmonary embolism: one-year follow-up with echocardiography doppler and five-year survival analysis.

BACKGROUND: The long-term prognosis for patients with pulmonary embolism (PE) is dependent on the underlying disease, degree of pulmonary hypertension (PH), and degree of right ventricular (RV) dysfunction. A precise description of the time course of pulmonary artery pressure (PAsP)/RV function is therefore of importance for the early identification of persistent PH/RV dysfunction in patients treated for acute PE. Other objectives were to identify variables associated with persistent PH/RV dysfunction and to analyze the 5-year survival rate for patients alive 1 month after inclusion. METHODS AND RESULTS: Echocardiography Doppler was performed in 78 patients with acute PE at the time of diagnosis and repeatedly during the next year. A 5-year survival analysis was made. The PAsP decreased exponentially until the beginning of a stable phase, which was 50 mm Hg at the time of diagnosis of acute PE was associated with persistent PH after 1 year. The 5-year mortality rate was associated with underlying disease. Only patients with persistent PH in the stable phase required pulmonary thromboendarterectomy within 5 years. CONCLUSIONS: An echocardiography Doppler investigation performed 6 weeks after diagnosis of acute PE can identify patients with persistent PH/RV dysfunction and may be of value in planning the follow-up and care of these patients.

Assessment of myocardial glutamate requirements early after coronary artery bypass surgery.

Glutamate is an important substrate for the intermediary metabolism of the heart, particularly in association with ischemia. Early after coronary artery bypass surgery (CABG) myocardial uptake of glutamate seems to be limited by substrate availability (arterial levels). However, glutamate is not an innocuous substrate. As arterial levels of glutamate are important both for myocardial uptake and adverse effects, an attempt was made to determine a minimum dose of glutamate sufficient to supply the needs of the heart after CABG. Ten patients received and infusion of 220-240 ml of 0.1 M L-glutamic acid solution at varying rates during two 30-min periods, starting 2 h after uncomplicated elective CABG. Intravenous glutamate infusion caused a dose-dependent linear increase in arterial glutamate and an increased myocardial uptake of glutamate. However, myocardial uptake of glutamate correlated with arterial levels only at lower infusion rates. Although maximal peak uptake in individual patients (6.6 +/- 1.1 mumol/min) occurred at an average increase of arterial whole blood glutamate of 172 +/- 34 mumol/L, the greatest impact on myocardial glutamate uptake was achieved by increasing arterial whole blood glutamate by less than 100 mumol/L. This implies that an infusion rate of 30-40 mg glutamate/kg BW/h could suffice to achieve a maximal or near maximal myocardial glutamate uptake in most patients after CABG. The adequacy of this dosage remains to be confirmed in high-risk patients.

Improved lung function and quality of life following increased elastic recoil after lung volume reduction surgery in emphysema.

Lung volume reduction surgery for severe emphysema with removal of 20-30% of the most destroyed parts of the lung parenchyma has been reported to improve lung function substantially. Increased elastic recoil has been suggested as one underlying mechanism for the improvement. Fourteen patients, seven men and seven women with a mean age of 62 years, who underwent bilateral lung volume reduction surgery have been followed up for 3 months. We here report the data on quality of life, lung function and elastic recoil. FEV1.0 increased by a mean of 26% from 0.581 to 0.731 (P < 0.01). The mean TLC was reduced by 16% from 8.91 to 7.51 (P < 0.001). The level of hyperinflation decreased as implied by a reduction in the ratio of RV to TLC from 0.70 to 0.60 (P < 0.001). The pulmonary elastic recoil improved, with an increase in the transpulmonary pressure at maximal inspiration (PelTLC) from 0.95 kPa to 1.35 kPa (P < 0.05) and an average increase in the coefficient of retraction PelTLC/TLC) from 0.12 kPa l-1 to 0.19 kPa l-1 (P < 0.01). The resting PaO2 increased from a mean of 8.7 kPa to 9.8 kPa (P < 0.01). The patients reported a high degree of subjective improvement according to the St. George's Respiratory Questionnaire and the working capacity on a bicycle increased by 26% from a mean of 38 W to 48 W (P < 0.01). The promising short-term results of lung volume reduction surgery for severe emphysema appear to be related to improved pulmonary elastic recoil.

Intravenous aspartate infusion after a coronary operation: effects on myocardial metabolism and hemodynamic state.

BACKGROUND: In a previous study glutamate infusion after coronary artery bypass grafting was associated with beneficial effects on myocardial metabolism and myocardial performance. It has been claimed that aspartate is more important than glutamate for the recovery of myocardial metabolism after cardioplegic arrest. Therefore, the metabolic and hemodynamic effects of aspartate were studied after coronary artery bypass grafting. METHODS: Fifty to 240 mL of a 0.1 mol/L aspartic acid solution was infused intravenously during 60 minutes in 10 patients early after coronary artery bypass grafting. Myocardial metabolism was studied using the coronary sinus catheter technique. RESULTS: Aspartate infusion caused a significant increase in the arterial levels of both aspartate and glutamate. This was associated with a significant increase in myocardial uptake of aspartate and a decrease in myocardial uptake of glutamate. Myocardial exchange of other substrates remained unaffected. There were no changes in hemodynamic state except an increase of heart rate and pulmonary vascular resistance. CONCLUSIONS: Interactions with glutamate metabolism, compatible with competitive inhibition of myocardial glutamate uptake, which may have outweighed potential effects of aspartate, were observed. Recognition of these amino acid interactions is important as they are used together as additives in cardioplegic solutions.

Pulmonary embolism: relation between the degree of right ventricle overload and the extent of perfusion defects.

BACKGROUND: Inasmuch as the presence of right ventricle (RV) overload in patients with pulmonary embolism (PE) is associated with a bad prognosis, evaluation of RV function in PE is of importance. This study was done to establish if the degree of RV overload can be predicted from the extent of perfusion defects (PDf). METHODS: One hundred twenty-one consecutive patients with PE diagnosed by lung scintigraphy (LS) were examined by echocardiography Doppler (ED) immediately after diagnosis. PDf were graded visually in categories (LS score 1 = < or =20%, 2 = >20% of total lung area) and on a continuous scale (normal perfusion = 0, no perfusion = 1). The reproducibility of both methods was tested. RV wall motion was assessed on a four-point scale (0 = normal to 3 = severely hypokinetic). The distance from LV posterior wall to RV anterior wall and dimensions of RV and LV were measured. Pulmonary artery systolic pressure (PAsP) was calculated by using the maximum velocity of tricuspid regurgitation. RESULTS: There were 51 patients with LS score 1 and 70 (58%) with score 2. In comparison with patients with LS score 1, those with score 2 more often had RV hypokinesis 2+ or 3+ (n = 49 vs n = 16) (p < 0.001), larger RV (34 +/- 6 mm [22 to 48] vs 29 +/- 5 [17 to 38]) (SD [range]) (p < 0.001) and higher PAsP (51 +/- 13 mm Hg [21 to 83] vs 42 +/- 14 [20 to 81]) (p < 0.001). The variability in both groups was large. With continuous scaling, PDf averaged 0.3. This was also the value that best discriminated RV hypokinesis 2+ or 3+ in a receiver operating characteristic curve. However, the variability for this scan scoring method was SD 0.073, giving a 95% confidence limit of +/-0.15. CONCLUSION: There is a significant correlation between RV overload and PDf, but the variability is large; therefore, an estimate of the size of perfusion defects in LS cannot replace ED in the assessment of PAsP and the degree of RV overload in PE.

Changes in human coronary sinus blood flow and myocardial metabolism induced by ventricular fibrillation and defibrillation.

BACKGROUND: During implantation of cardioverter-defibrillators, repeated inductions of ventricular fibrillation and defibrillation are performed. Little is known about the myocardial metabolism associated with ventricular fibrillation and defibrillation in humans. METHODS: Sixteen patients scheduled for transvenous cardioverter-defibrillator implantation were included in the study. In 10 of the patients, blood samples were taken simultaneously in the coronary sinus and radial artery and analyzed for PO2, PCO2, standard bicarbonate, pH, lactate, alanine, glucose, and glycerol. Oxygen saturation, base excess, and oxygen content were calculated. The patients were studied before, shortly after, and 2 and 5 minutes after successful defibrillation. In six of the patients, coronary sinus blood flow was registered continuously. RESULTS: The coronary sinus blood flow declined from a basal value of 93 +/- 16 mL/min to 35 +/- 6 mL/min 14 +/- 2 seconds after induction of ventricular fibrillation. Following termination of ventricular fibrillation, coronary sinus blood flow increased to a peak value of 227 +/- 75 mL/min. Oxygen saturation, PO2, and oxygen content in the coronary sinus increased by approximately 25% shortly after each episode of ventricular fibrillation and defibrillation. The coronary sinus lactate increased and the arterio-coronary sinus lactate difference decreased shortly after each of the four episodes, but was normalized within 2 minutes. CONCLUSIONS: Repeated threshold tests during defibrillator implantation did not cause any long-lasting or cumulative metabolic effects, indicating that the described technique, with a 5-minute recovery period in between episodes, is safe as regards myocardial metabolism.

Echocardiography Doppler in pulmonary embolism: right ventricular dysfunction as a predictor of mortality rate.

To test the hypothesis that right ventricular (RV) systolic dysfunction at the time of diagnosis of pulmonary embolism (PE) is a predictor of mortality rate, 126 consecutive patients with PE were examined with echocardiography Doppler (ED) on the day of diagnosis. RV function was assessed by evaluation of wall motion on a four-point scale. The material was divided into two groups: group A (n = 56) with normal or slightly reduced RV function and group B (n = 70) with moderately or severely reduced RV function. The overall mortality rate was 7.9% in the hospital and 15.1% within 1 year. Four deaths occurred in group A and 15 in group B (p = 0.04). All in-hospital deaths (n = 10) occurred in group B (p = 0.002). The variables associated with mortality rate were RV dysfunction and cancer (in-hospital, p = 0.002 and 0.004; 1 year, p = 0.04 and < 0.001, respectively). Nine (7.1%) deaths (all in-hospital) were caused by PE. Five of these patients had advanced-stage cancer. The in-hospital mortality rate in patients without cancer was 4%, all from PE and all in group B. In conclusion, RV dysfunction when diagnosis of PE is established is associated with mortality rate. A strategy for risk stratification of patients with PE with ED may be of clinical usefulness.

High incidence of scintigraphic myocardial uptake defects at rest and during exercise in male elite runners.

OBJECTIVE: To evaluate the usefulness of myocardial perfusion scintigraphy (MIBI-SPECT) as a diagnostic tool in well trained men. DESIGN: The study was prospective, involving 2 d stress-rest myocardial scintigraphy (MIBI-SPECT), polar map reconstruction with and without uniform attenuation correction, and comparison with a healthy male group (local Swedish) and with a commonly used reference group (American, Emory University Hospital). SETTING: University Hospital, Stockholm, Sweden. SUBJECTS: 16 healthy, male elite runners (mean (SD) age 26.1 (3.1) years). Peak oxygen uptake 73 (4) ml O2/kg/min. RESULTS: Uptake defects on polar maps were found in the majority of the runners compared with both reference groups (local Swedish 13/16, American 10/16). Most defects (91%) were fixed. Defects were located in the anterior, lateral, and posterior regions of the left ventricle. Application of a uniform attenuation correction algorithm enhanced rather than reduced perfusion defect size, probably because this correction method is imperfect in SPECT studies of the thoracic cavity. CONCLUSIONS: If myocardial perfusion scintigraphy is used for evaluating well trained men, existing normal reference files for semiquantitative evaluation appear to be inadequate.

Power output for wheelchair driving on a treadmill compared with arm crank ergometry.

OBJECTIVES: The limiting factors with regard to power output available for wheelchair ambulation have not been identified. The aim of the present study was to correlate power output during wheelchair driving with (i) power output and oxygen uptake during arm crank ergometry and (ii) arm muscle strength. METHODS: Eleven disabled men were examined for maximal power output (POmax) during wheelchair driving on a treadmill and during arm crank ergometry. Oxygen uptake (VO2) was recorded at submaximal and maximal arm crank ergometry in all men and during submaximal wheelchair driving on a treadmill in four men. Power output during wheelchair driving on a treadmill was measured. Static and dynamic elbow muscle strength was measured isokinetically. RESULTS: POmax was significantly lower (P < 0.001) for wheelchair driving (109 (31) W; mean (SD)) than for arm ergometry (163 (49) W). There was a significant correlation between POmax for arm crank ergometry and wheelchair driving (r = 0.73). There was no correlation between POmax and elbow strength. The mechanical efficiency was constant for the different levels on the arm crank ergometry test. The submaximal testing showed a consistently lower mechanical efficiency for wheelchair driving than for arm crank ergometry. CONCLUSIONS: It is suggested that the lower level of power output for wheelchair driving is fully explained by the lower mechanical efficiency. Any improvement in power output available for ambulation must be based on wheelchair ergonomics.

Metabolic and hemodynamic effects of intravenous glutamate infusion early after coronary operations.

Amino acids, particularly glutamate, have been proposed to play an important role in the recovery of cardiac oxidative metabolism after ischemia. In this investigation, the metabolic and hemodynamic effects of glutamate infusion after coronary operations were studied. From 220 to 240 ml 0.1 mol/L l-glutamic acid solution was infused in 10 patients during 1 hour starting 2 hours after operation. A control group of 10 patients received an infusion of 240 ml saline solution. During glutamate infusion, there were significant increases in the uptake of glutamate (from 0.7 +/- 0.2 micromol/min in the basal state to a peak of 5.7 +/- 1.2 micromol/min at 20 minutes) and lactate (from 4.9 +/- 2.0 micromol/min in the basal state to 14.1 +/- 4.4 micromol/min at 60 minutes; p < 0.01), whereas the uptake and release of other substrates remained essentially unaffected. Arterial glutamate levels (in whole blood) increased from 103 +/- 10 micromol/L to 394 +/- 20 micromol/L at 60 minutes. Thirty minutes after discontinuation of the glutamate infusion, arterial levels had decreased to 129 +/- 17 micromol/L. The markedly improved utilization of lactate and the unchanged release of alanine together suggest that the oxidative metabolism of the heart was stimulated by glutamate. The metabolic changes were associated with improved myocardial performance. Left ventricular stroke work index increased from 26.8 +/- 2.1 gm x beat(-1) x m(-2) body surface area to 31.3 +/- 3.1 gm x beat(-1) x m(-2) body surface area during glutamate infusion. Metabolic support with amino acids may provide a means to improve recovery of metabolic and hemodynamic function of the heart early after cardiac operations.

Insulin resistance is not exhibited by advanced chronic obstructive pulmonary disease patients.

We have previously reported increased blood glucose concentrations and skeletal muscle glycogen depletion in severe COPD patients with chronic respiratory failure. In order to see if insulin resistance exists in severe COPD, we investigated nine patients with advanced COPD with chronic hypoxaemia and seven healthy control subjects of similar age, using the euglycaemic hyperinsulinaemic glucose clamp technique. We could not demonstrate a subnormal intravenous glucose requirement in response to insulin when maintaining euglycaemia in the COPD patients with chronic hypoxaemia. This indicates that the net metabolism of glucose in COPD patients with chronic hypoxaemia is not resistant to insulin.