Evaluation of the correlation with preoperative left ventricular end-systolic volume index and postoperative exercise tolerance in the patient with aortic regurgitation]

Twenty-three male patients (49 +/- 11 years old) undergoing aortic valve replacement (AVR) for aortic regurgitation received the exercise tolerance test using bicycle ergometer at more than one year after AVR. Preoperative left ventricular end-systolic volume index (LVESVI) significantly correlated with tolerance time, peak VO2, anaerobic threshold (AT) during the exercise, and with serum noradrenaline (NAd) levels at rest. Then patients were divided into two groups: those with preoperative LVESVI < or = 70 ml/M2 (13 patients, group A), and those with LVESVI > 70 ml/M2 (10 patients, group B). All patient in group A achieved more than 75 W of the exercise, however only one in group B achieved this level. The increase of VO2 in group B with an increasing exercise was significantly suppressed compared to group A, and then, the peak VO2 levels in group B were significantly lower than in group A (A: 20.9 +/- 3.7, B: 11.4 +/- 3.9 ml/kg/min). In addition group B showed a less increase of AT levels (A: 10.6 +/- 2.9, B: 6.8 +/- 2.3 ml/kg/min). In contrast, serum lactate and NAd levels in group B increased significantly at 50 W of the exercise compared to group A (A: 12.5 +/- 3.7, 332.3 +/- 104.2; B: 17.5 +/- 5.7 mg/dl, 746.7 +/- 324.3 pg/ml, respectively) though a significant difference of NAd levels before the exercise was observed between the both groups (A: 173.7 +/- 34.2, B: 329.0 +/- 132.1). In conclusion, group A showed a better exercise tolerance physiologically and biochemically compared to group B.(ABSTRACT TRUNCATED AT 250 WORDS)     

Is ventilatory anaerobic threshold useful for preoperative assessment?

The anaerobic threshold (VAT), obtained by measurement of ventilatory volume and by expiratory gas analysis, and the anaerobic threshold (LAT), obtained directly from the lactic acid value in the blood, were compared and evaluated during exercise load in 25 patients with mitral valve disease. Exercise loading was performed with an ergometer using a multistep method of increases of 5 W (Group A, 11 cases) or 10 W (Group B, 14 cases) per minute. The oxygen uptake value at the points of 0.5 mmol.l-1 and 1.0 mmol.l-1 increase in the lactic acid values when compared with the starting values were designated as 0.5 LAT and 1.0 LAT. VAT was found in 4 of 11 (36%) patients in Group A and in 12 of 14 (86%) patients in Group B and the ratio obtained was significantly higher in Group B than in A. The 0.5 LAT values for Group A and B were 2.4 +/- 0.5 and 2.2 +/- 0.3, respectively. The 1.0 LAT values were 2.9 +/- 0.7 and 2.7 +/- 0.4, and among the two groups no significant difference was found concerning 0.5 LAT or 1.0 LAT. VAT was seen in 16 or 25 patients and the average VAT value of the 16 was roughly at the midpoint between the average values for 0.5 LAT and 1.0 LAT. Therefore in patients in which VAT was seen with the expiratory gas method, VAT and LAT values were basically equivalent. However, in Group A, VAT was seen in only 4 of 11 patients and it is a fact that it is difficult to find VAT without a suitable exercise load.     

Effects of Recombinant Human Erythropoietin and Exercise Training on Exercise Capacity in Hemodialysis Patients

Abstract: The effects of recombinant human erythropoietin (rHuEPO) and exercise training on exercise capacity were evaluated in 20 hemodialysis patients. After improvement of anemia by rHuEPO (Phase I), patients were divided into 2 groups. Group 1, 10 patients, was placed in a 3–month exercise training program. Group 2, 10 patients, served as a control group (Phase 2). A symptom-limited exercise tolerance test was performed at the start of Phase 1 and before and after Phase 2. Hemoglobin (Hb) values were kept constant throughout Phase 2. In Phase 1, maximum workloads (62.0 ± 19.1 to 76.5 ± 25.6 W, p < 0.001), maximum O₂ uptake (Vo_2max) (18.7 ± 3.5 to 2.2 ± 5.9 ml/min/kg, p < 0.01), and Vo₂ at anaerobic threshold (AT) (Vo_2AT) (8.5 ± 2.1 to 10.2 ± 2.9 ml/min/kg, p < 0.01) were all improved by rHuEPO. However, in Phase 2, despite unchanged Hb values and maximum workloads, Vo_2max (20.7 ± 4.6 to 17.6 ± 2.6 ml/min/kg, p < 0.05) and Vo_2AT (10.6 ± 1.4 to 9.5 ± 1.8, ml/min/kg p < 0.05) were decreased in Group 2. However, in Group 1, maximum workloads (66.7 ± 8.2 to 81.7 ± 7.5 W, p < 0.01) were improved, and Vo_2max and Vo_2AT were not decreased significantly in the same period. Exercise training in rHuEPO-treated hemodialysis patients resulted in an improved aerobic exercise capacity, whereas those without exercise training did not have increased capacity. Throughout the study, O₂ uptakes were lower than those of nonrenal anemic patients who had similar Hb values. Maximum lactate values also remained low. In conclusion, improvement in the exercise capacity in hemodialysis patients treated with rHuEPO was minimal. Some defects were suggested in the aerobic energy production system in skeletal muscle of dialysis patients. Anemia-improved patients should participate in incremental physical activity to maintain an improved exercise capacity.     

Effect of exercise at the AT point for children with cerebral palsy

Eleven children with spastic cerebral palsy (CP) who could walk underwent exercise at the anaerobic threshold (AT) point. The subjects exercised for 20 minutes per session, twice a week for a period ranging from 6 to 20 weeks. The subjects were divided into two groups. The leg exercise group contained six CP children who exercised on a cycle ergometer with average attendance of 1.8 days a week. The other five CP children constituted the arm exercise group and exercised using an arm cranking ergometer with average attendance of 1.5 days per week. After the exercise period, the oxygen uptake (VO2) at the AT point increased significantly in the children in the leg exercise group. On the other hand, the VO2 at the AT point did not change in children in the arm exercise group. These results demonstrate that cycle ergometer exercise at the AT point is effective in improving the physical endurance of children with CP. In contrast, arm exercises for children with CP seem to have little effect on increasing physical endurance.     

Venous saturation and the anaerobic threshold in neonates after the Norwood procedure for hypoplastic left heart syndrome

BACKGROUND: Reduction in oxygen delivery can lead to organ dysfunction and death by cellular hypoxia, detectable by progressive (mixed) venous oxyhemoglobin desaturation until extraction is limited at the anaerobic threshold. We sought to determine the critical level of venous oxygen saturation to maintain aerobic metabolism in neonates after the Norwood procedure (NP) for the hypoplastic left heart syndrome (HLHS). METHODS: A prospective perioperative database was maintained for demographic, hemodynamic, and laboratory data. Invasive arterial and atrial pressures, arterial saturation, oximetric superior vena cava (SVC) saturation, and end-tidal CO2 were continuously recorded and logged hourly for the first 48 postoperative hours. Arterial and venous blood gases and cooximetry were obtained at clinically appropriate intervals. SVC saturation was used as an approximation of mixed venous saturation (SvO2). A standard base excess (BE) less than -4 mEq/L (BElo), or a change exceeding -2 mEq/L/h (deltaBElo), were used as indicators of anaerobic metabolism. The relationship between SvO2 and BE was tested by analysis of variance and covariance for repeated measures; the binomial risk of BElo or deltaBElo at SvO2 strata was tested by the likelihood ratio test and logistic regression, with cutoff at p < 0.05. RESULTS: Complete data were available in 48 of 51 consecutive patients undergoing NP yielding 2,074 valid separate determinations. BE was strongly related to SvO2 (model R2 = 0.40, p < 0.0001) with minimal change after adjustment for physiologic covariates. The risk of anaerobic metabolism was 4.8% overall, but rose to 29% when SvO2 was 30% or below (p < 0.0001). Survival was 100% at 1 week and 94% at hospital discharge. CONCLUSIONS: Analysis of acid-base changes revealed an apparent anaerobic threshold when SvO2 fell below 30%. Clinical management to maintain SvO2 above this threshold yielded low mortality.     

Effects of sildenafil on cardiopulmonary responses during stress

PURPOSE: To investigate possible effects of sildenafil on the cardiopulmonary responses during sexual intercourse we evaluated cardiopulmonary responses during exercise in a group of impotent patients. MATERIALS AND METHODS: The study sample included patients with erectile dysfunction who underwent a cardiopulmonary exercise test before and after the administration of 100 mg. sildenafil citrate. Cardiopulmonary exercise test parameters at rest, at the anaerobic threshold, at peak exercise and at 1-minute recovery were recorded, including systolic and diastolic blood pressure, the heart rate, O2 consumption, CO2 production, ventilation and the respiratory rate. Furthermore, O2 consumption per kg. body weight, the ventilatory equivalent for O2 consumption (ventilation/O2 consumption) and CO2 production (ventilation/CO2 production), the respiratory quotient, metabolic equivalents metabolic equivalents, oxygen pulse (O2 consumption/heart rate) and the change in O2 consumption/change in heart rate were calculated. RESULTS: In 2 of the 43 patients enrolled in the study myocardial ischemia and high blood pressure were detected at rest in 2, respectively, who were excluded from analysis. In the remaining 41 patients with a mean age +/- SD of 52.3 +/- 8.6 years a statistically significant decrease in systolic and diastolic blood pressure was noted after sildenafil use at all stages tested (p <0.002 to 0.001). The heart rate mildly increased after sildenafil use at rest and at peak exercise (p = 0.018). The O2 pulse decreased at the anaerobic threshold (p = 0.003), peak exercise (p = 0.001) and recovery (p = 0.047). In the 11 patients with a mean age of 40.8 +/- 10.12 years who had psychogenic erectile dysfunction the only 2 parameters affected were an increased heart rate and decreased systolic blood pressure at rest, while O2 consumption/heart rate decreased at the anaerobic threshold. In the 18 patients with a mean age of 61.1 +/- 8.9 years who had organic erectile dysfunction and an unremarkable medical history a decrease was noted in systolic and diastolic blood pressure at rest and at peak exercise, and diastolic blood pressure also at recovery, while the heart rate increased at recovery. In the 12 patients with a mean age of 60.16 +/- 9.12 years who had treated cardiovascular disease systolic and diastolic blood pressure decreased at all states and O2 consumption/heart rate at the anaerobic threshold and at peak exercise, while increased values were noted for the respiratory rate at the anaerobic threshold and ventilation/CO2 production at recovery. CONCLUSIONS: Hemodynamic changes after sildenafil administration should be considered minimal in concert with patient health status. Younger patients without signs of systemic atherosclerosis compensate the vasodilatory effect of sildenafil during exercise, while in older patients with vasculogenic erectile dysfunction moderate changes may be noted regardless of cardiovascular disease in the medical history.     

Does an aortopulmonary shunt before repair of tetralogy of Fallot limit exercise tolerance in long-term survivors?

The purpose of this study was to evaluate the impact of an aortopulmonary shunt on exercise capacity in long-term survivors after total repair of tetralogy of Fallot (17.6(2.0) years' follow-up). Submaximal exercise tests, pulmonary function tests, lung diffusion tests for carbon monoxide, two-dimensional and Doppler echocardiography were performed in 12 patients with an aortopulmonary shunt (group A) and in 21 patients (group B) without a shunt before repair. There were no significant differences in two-dimensional and Doppler echocardiographic findings nor in pulmonary function. Group A showed a significantly lower diffusion capacity of the lung for carbon monoxide at rest (66.2(13.0)% versus 84.1(9.5)%; P < 0.01) and at the anaerobic threshold (71.8(11.0)% versus 87.2(9.8)%; P < 0.01) as well as a significantly reduced physical working capacity at ventilatory anaerobic threshold (1.6) (0.32) W/kg versus 2.41(0.43) W/kg; p < 0.01). A negative correlation was observed between the duration of palliative shunts and diffusion capacity of the lung for carbon monoxide at rest at ventilatory anaerobic threshold (r = −0.8635 and −0.9108 respectively). A shunt placed before definitive repair impairs the long-term working capacity, probably by diminishing the diffusion capacity of the lung for carbon monoxide, especially if the shunt is in place for more than 20 months.     

Exercise tolerance after correction of tetralogy of Fallot

Twenty-six postoperative patients with tetralogy of Fallot (TF) were evaluated by exercise stress test with an upright cycle ergometer. Oxygen uptake was assessed at the anaerobic threshold and the peak achieved work load. Oxygen uptake at the anaerobic threshold (VO2AT) was in the normal range regardless of the existence of residual stenosis (PS) or pulmonary regurgitation (PR). However, oxygen uptake at the peak achieved workload (VO2max) was subnormal in patients with PS or PR. Maximal heart rate in TF patients was lower than normal. Patients with PR showed significantly reduced VO2max as compared with those without PR (p less than 0.05). This is found to be resulted from limitation of the oxygen pulses increase.     

Long-term follow-up of exercise tolerance after coronary bypass grafting]

Six hundred forty-eight serial graded exercise tests were performed on 400 patients up to 10 years after coronary bypass graftings (CABG). The maximal attained exercise tolerance, over 10 METS, were observed in 60% of patients and the negative response to exercise test in 43% of patients. The positive response in various parameters were observed at the following rates: graft occlusion-30% vs graft patent-46% (p less than 0.01); incomplete revascularization-39% vs complete revascularization-22% (p less than 0.01); and less than or equal to 8 METS 4-45% vs greater than or equal to 10 METS-28% (p less than 0.01), respectively. However, no significant difference was observed among number of vessels diseased, number of graftings, and presence of old myocardial infarction. The maximal attained stage of exercise, over 10 METS, in various parameters were at the following rates: less than or equal to 59 years old-70% vs greater than or equal to 60 years old-44% (p less than 0.01); male-63% vs female-32% (p less than 0.01); and graft patent-63% vs graft occlusion-50% (p less than 0.05), respectively. The serial analysis of exercise test demonstrated that improved exercise tolerance appears to persist for at least 5 years after CABG. However, the patients in complete revascularization had a tendency to increase the rate of positive response. In conclusion, the completeness of revascularization as well as graft patency was the main factor limiting exercise tolerance, and correlates with the extent and the duration of improvement after CABG.     

A cost/benefit analysis of randomized invasive monitoring for patients undergoing cardiac surgery

The aim of this study was to determine the effect of choice of invasive monitoring on cost, morbidity, and mortality in cardiac surgery. Two hundred and twenty-six adults undergoing elective cardiac surgery were initially assigned at random to receive either a central venous pressure monitoring catheter (group I), a conventional pulmonary artery (PA) catheter (group II), or a mixed venous oxygen saturation (SvO2) measuring PA catheter (group III). If the attending anesthesiologist believed that the patient initially randomized to group I should have a PA catheter, that patient was then reassigned to receive either a conventional PA catheter (group IV) or SvO2 measuring PA catheter (group V). The total costs were defined as the total amount billed to the patient for the catheter used; the professional cost of its insertion; and the determinations of cardiac output, arterial blood gas tensions, hemoglobin level, and hematocrit. Mean total monitoring and laboratory costs in Group I ($591 +/- 67) were statistically significantly (P less than 0.05) less than costs in Group II ($856 +/- 231). Further, mean monitoring and laboratory costs in Group II were statistically significantly (P less than 0.05) less than those in Group III ($1128 +/- 759). Patients in group IV incurred mean total costs of $986 +/- 578, while those in group V had mean total costs of $1126 +/- 382 (NS). There were no significant differences between any of the groups with respect to length of stay in the intensive care unit, morbidity, or mortality.(ABSTRACT TRUNCATED AT 250 WORDS)     

Assessment of Subjective Perceived Exertion at the Anaerobic Threshold with the Borg CR-10 Scale

The purpose of this study was to evaluate the anaerobic threshold (AT) with a graphic visual method for estimating the intensity of ventilatory and metabolic exertion and to determine the ratings of perceived exertion (RPE) on the Borg CR-10 scale during a continuous ramp type exercise test (CT-R). Forty healthy, physically active and sedentary young women (age 23.1 ± 3.52 years) were divided into two groups according to their fitness level: active group (AG) and sedentary group (SG) and were submitted to a CT-R on a cycloergometer with 20 to 25 W/min increments. Shortly before the end of each one-minute period, the subjects were asked to rate dyspnea (RPE-D) and leg fatigue (RPE-L) on the Borg CR-10 scale. After the AT was determined with the graphic visual method, the score that the volunteers gave on the Borg CR10 scale was verified. Data were analyzed using the Mann-Whitney and Spearman correlation tests with the significance level set at 5%. The mean ratings of RPE-L and RPE-D at the AT level were not significantly different between groups (p > 0.05). Significant correlations were found between VO₂, heart rate (HR), power output and RPE for both groups. The muscular and respiratory RPE, according to the Borg CR-10 scale, were correlated with the AT, suggesting that scores close to 5, which correspond to a “strong” perception, may be used as parameters for quantifying aerobic exercise intensity for active and sedentary individuals. The similar perception of exercise intensity, which corresponded to the AT of different individuals, makes it possible to prescribe exercise at an intensity equivalent to the AT by means of the RPE.

Key points

• Interest in quantitative and systematic determination of the AT is growing, however, qualitative studies measure the AT by perceived exertion, are still unsubstantial.
• Borg CR-10 scale is a category scale with ratio properties consisting of numbers related to verbal expressions, which allows rate comparison between intensities as well as a determination of intensity levels.
• Scores close to 5 expressed on the Borg CR-10 scale, which correspond to a “strong” perception, may be used as parameters for quantifying the aerobic exercise intensity of both active and sedentary women.

Key words: Rating of perceived exertion, anaerobic threshold, exercise test     

The effects of walking at the anaerobic threshold level on vertebral bone loss in postmenopausal women

Summary The purpose of this study was to determine the optimal intensity of exercise necessary to prevent the postmenopausal bone loss on the basis of anaerobic threshold (AT). Thirty-three postmenopausal women were randomized to control (group C: n=12) or two exercise groups (group H and group M). All women performed a treadmill exercise test, and the AT was measured by expired gas analysis. The exercise regimen consisted mainly of walking at a speed that kept the exercise heart rate above the AT (group H: n=12) or below the AT (group M: n=9). Exercise was performed for 30 minutes, three times a week for 7 months. The bone mineral density (BMD) of the lumbar vertebrae was measured using dual energy X-ray absorptiometry. The BMD level in group C decreased by 1.7±2.7%, but there was a significant increase of 1.1±2.9% in group H. In group M there was a decrease of 1.0±3.1% which did not differ from group C. In group C, serum osteocalcin and urinary hydroxyproline excretion were significantly increased, but no changes were seen in either of the exercise groups. Urinary calcium significantly decreased in the exercise groups. We conclude that short-term (7 months) exercise with intensity above the AT is safe and effective in preventing postmenopausal bone loss.     

The effects of prostaglandin E1 on systemic and cerebral oxygenation before and during cardiopulmonary bypass

The purpose of this study was to examine the effects of a small dose of prostaglandin E1 on systemic and cerebral oxygenation. Thirty patients for coronary artery bypass graft surgery were randomly divided into two groups: Group 1 received PGE1 25 ng.kg-1.min-1. Group 2 received PGE1 50 ng.kg-1.min-1. After measuring baseline hemodynamics and mixed (SvO2) and juglar (SjvO2) venous oxygen saturations, administration of PGE1 at a rate of 25 ng.kg-1.min-1 or 50 ng.kg-1.min-1 was started before and during CPB. In group 2, mean arterial pressure (MAP) decreased during CPB, while in group 1, MAP was unchanged during CPB. There was no change in SjvO2 both in group 1 and group 2 before and during CPB. The administration of PGE1 at a rate of 25 ng.kg-1.min-1 during CPB was suitable for the maintenance of SvO2 and SjvO2.     

Expired Gas Analysis During Exercise Testing Pre-pneumonectomy

Purpose Expired gas analysis has enabled the successful prediction of postoperative complications in patients undergoing thoracic esophagectomy. We conducted this study to determine whether preoperative expired gas analysis during exercise testing can help identify patients at high risk of postoperative complications after pneumonectomy. Methods We measured the vital capacity, percent vital capacity, forced expiratory volume in 1.0 s, percent forced expiratory volume in 1.0 s, maximum oxygen uptake per minute, anaerobic threshold, arterial partial pressure of oxygen, and arterial partial pressure of carbon dioxide in 27 patients scheduled to undergo pneumonectomy. Group A consisted of 18 patients without postoperative cardiopulmonary complications and group B consisted of 9 patients with postoperative cardiopulmonary complications. We compared preoperative cardiopulmonary data between these two groups. Results Postoperative cardiopulmonary complications developed in 9 of the 27 patients (33.3%), 3 (11%) of whom died. The maximum oxygen uptake and the anaerobic threshold were significantly higher in group A than in group B (P < 0.05), whereas spirometric pulmonary function testing and arterial blood gas analysis showed no intergroup differences. Conclusion Expired gas analysis during exercise testing can help identify patients at high risk of postoperative cardiopulmonary complications after pneumonectomy.     

Evaluation of the exercise intensity generated by active video gaming in patients with cystic fibrosis and healthy individuals

BackgroundAdherence of patients with cystic fibrosis (CF) to exercise is challenging. Here we compared the physiological responses during the use of interactive video games (VG) with the cardiopulmonary exercise test (CPET) in healthy and CF subjects.MethodsCross-sectional study including CF and healthy (CON) subjects older than 6 years. Individuals were evaluated in two visits. At visit one, anthropometric measures, spirometry and CPET were performed. In the second visit, a physical activity questionnaire was applied and gas analyses performed during the use (10 min) of both Nintendo Wii (Wii Fit Plus: (1) Obstacle Course, (2) Rhythm Boxing and (3) Free Run) and Xbox One (Just Dance 2015: (1) Love Me Again, (2) Summer and (3) Happy).ResultsTwenty-five CON and 30 CF patients were included. The mean FEV₁ (%) was significantly lower in the CF group compared to CON. There were no differences between groups at peak exercise (CPET) for heart rate (HR), oxygen consumption (VO₂) and minute ventilation (V_E). In the CON group, games 2 and 3 (Xbox) and game 3 (Nintendo) increased HR to values similar to the anaerobic threshold (AT), while for the CF group this occurred for games 2 (Xbox) and 3 (Nintendo). As for VO₂ and V_E, both groups obtained similar responses as compared to AT values in games 2 (Xbox) and 3 (Nintendo).ConclusionThe use of VG generated a cardiorespiratory response similar to AT levels found during CPET, indicating that it may be an alternative for exercise training of CF individuals.     

Factors influencing mixed venous oxygen saturation in intensive care

Changes in mixed venous blood oxygen saturation (SvO2) were studied in 2 groups of patients. Group I patients (n = 10) were all hypoxaemic, suffering from acute respiratory failure, requiring that FIO2 be maintained at 1 throughout the study; respiratory and haemodynamic conditions were improved using PEEP and cardiovascular support. On the other hand, Group II patients (n = 13) were non-hypoxaemic patients with circulatory shock in whom FIO2 was gradually increased, and the haemodynamic status was improved using positive inotropic drugs (dopamine, dobutamine, adrenaline, amrinone). All 23 patients had a Swan-Ganz catheter set up for monitoring; all the usual haemodynamic and respiratory parameters were measured. Haematocrit values were kept at the same level throughout the study. Haemodynamic parameters were measured each time a new therapeutic procedure was carried out. No close relationship between SvO2 changes and changes in cardiac index or O2 consumption were found. However, a close relationship existed between changes in SvO2 and changes in O2 extraction (EAO2): SvO2 = -EAO2 + 102 (Group I; r = 0.90, n = 54); SvO2 = -1.2 EAO2 + 103 (Group II; r = 0.93, n = 66). A strong relationship was also found between changes in SvO2 and in FIO2 in each patient of Group II. In the complicated physiological set-up of an intensive care patient, SvO2 reflects oxygen extraction. A fall in SvO2 is related to an altered oxygen demand: oxygen supply ratio. In the most seriously ill patients, there is no relationship between changes in SvO2 and cardiac index.     

Non-invasive assessment of right and left ventricular volumes 11 to 24 years after corrective surgery on patients with tetralogy of Fallot

Patients who had corrective surgery for tetralogy of Fallot using a transannular right ventricular outflow tract (TRVOT) patch showed a higher risk of post-operative mortality and reoperation in the long-term follow-up. A total of 642 patients were operated upon for tetralogy of Fallot between 1952 and 1982. Twenty-six patients who survived for more than 10 years were selected for this study. Fifteen randomly selected patients (group 1) without outflow tract patch were compared with 11 patients (group 2) where a transannular right ventricular outflow patch had been used. Right and left ventricular volumes were assessed using combined first-pass and equilibrium radionuclide ventriculography. After administration of 25 mCi of 99mTc-pertechnetate, data were acquired with a gamma camera with a large viewing field and the patient at rest and during exercise. The patients in group 1 were able to manage a workload of 65 +/- 24 W on the bicycle ergometer while the patients in group 2 could only reach a mean maximum of 34 +/- 12 W. Right ventricular end-diastolic volume (RV-EDV) at rest was 198 +/- 67 ml in group 1 and 224 +/- 69 ml in group 2. During exercise, RV-EDV was increased to 218 +/- 75 ml in group 1 (P less than 0.01) and to 246 +/- 79 ml in group 2. Right ventricular end-systolic volumes did not change significantly during exercise. In group 1, the left ventricular (LV) volumes were comparable to the normal; in group 2, LV-EDV was diminished at rest and during the stress test.(ABSTRACT TRUNCATED AT 250 WORDS)     

Test-retest reliability of the oxygen uptake efficiency slope in surgical patients

The oxygen uptake efficiency slope is a measure of cardiopulmonary fitness, that can be obtained from a sub-maximal cardiopulmonary exercise test. It has been evaluated in medical patients but its reliability in surgical populations remains uncertain. We conducted a test-retest study with the aim of establishing the reliability of the oxygen uptake efficiency slope in relation to that of the anaerobic threshold and peak oxygen uptake, in general surgical patients. Twenty-six patients over 60 years old completed two symptom-limited, incremental cycle ergometry tests within 7 days. The mean (SD) anaerobic threshold was 13.0 (3.0) mlO(2) .kg(-1) .min(-1) . There were no significant differences between mean test and retest values of anaerobic threshold (p = 0.50), peak oxygen uptake (p = 0.76) or oxygen uptake efficiency slope (p = 0.42). Reliability coefficients (95% CI) for the anaerobic threshold, oxygen uptake efficiency slope and peak oxygen uptake were 66.7% (45.3-87.9%), 89.0% (81.0-96.9%) and 91.7% (85.7-97.8%), respectively. The oxygen uptake efficiency slope was determined easily in all patients and found to have excellent reliability. Its clinical utility in determining pre-operative fitness warrants further evaluation.     

Glucose tolerance and insulin secretion in infants with the left to right shunt congenital heart disease]

Between 1980 and 1988, 32 infants under three years of age with left to right shunt congenital heart disease underwent cardiac catheterizations, and their glucose tolerance and insulin secretion were investigated. These patients were divided into three groups by weight and compared. Group I consisted of 11 patients whose weights were 80% or more of the ideal body weight (IBW) for their age. Group II consisted of 10 patients whose weights were between 70% and 80% of the IBW. Group III consisted of 11 patients whose weights were less than 70% of the IBW. The CTR and biochemical blood studies showed no difference. By cardiac catheterization, Group III showed higher pulmonary/systemic vascular pressure ratio (Pp/Ps) than Group I. The mixed venous O2 saturation (SvO2) were 69.5 +/- 6.41% in Group I, 64.8 +/- 5.78% in Group II, 57.2 +/- 3.59% in Group III. Group III showed the lowest SvO2 of the three. Group III also showed the lowest arterial O2 saturation (SaO2). This indicates that the patients of Group III had the most serious congestive heart failure. In the 0.5 g/kg intravenous glucose tolerance tests, the K values (glucose disappearance rates) were as follows: Group I: 3.30 +/- 0.597, Group II: 2.91 +/- 0.624, Group III: 2.48 +/- 0.417. Group III showed the lowest values of the three. This indicates the deterioration of glucose tolerance in Group III. In the examination of serum insulin secretion, Group III showed the lowest serum insulin levels: 26.6 +/- 18.3 mmu/ml at 3-minute intervals, 22.8 +/- 14.3 mmu/ml at 5-minute intervals. After cardiac catheterization, corrective operations were performed on 17 patients out of 32. Fifteen patients survived, though 2 patients of Group III died early postoperatively. The results of glucose tolerance test and serum insulin levels before and after operation in 12 survivors were compared. Although the K values had been 2.8 +/- 0.41 before operation, it rose up to 3.81 +/- 0.81 three to four weeks after operation. The serum insulin levels at 3, 5, 10 and 15-minute intervals also rose after operation. This indicates the improvement of glucose tolerance and insulin secretion due to the improved circulation. It is suggested that the adequate nutritional management before and after operation on infants with serious congestive heart failure, because they tend to have malnutrition before operation. Aggressive and careful nutritional management is advisable.     

Weaning from artificial respiration: value of continuous monitoring of mixed venous oxygen saturation

Weaning from mechanical ventilation is particularly difficult in patients with combined cardiac and respiratory failure. Continuous monitoring of mixed venous blood oxygen saturation (SvO2) redefines weaning in terms of tissue oxygenation. A stable SvO2 greater than 60% during weaning is a reliable index of weanability. However, further studies are required to establish a tolerance threshold for SvO2 during weaning. In the limited experience reported here, an immediate and abrupt fall in SvO2, when the patient started to breathe spontaneously was invariably associated with difficulties in weaning. In some patients, other signs of left ventricular dysfunction rapidly ensued, with a fall in cardiac index. Weaning remained possible if the treatment was capable of increasing cardiac output and normalizing SvO2. If, during spontaneous breathing, SvO2 remained stable in the 50-55% range, with no significant decrease in cardiac output, abrupt and unpredictable drops of SvO2 under 40% range occurred. Such falls always preceded signs of tissue hypoxia, leading to a resumption of controlled mechanical ventilation. However, further studies are required to fully delineate the role of SvO2 in the fine tuning of inotropic support and ventilatory assistance in the difficult weaning of patients recovering from cardio-respiratory failure.