Lennart Kaijser

Blood flow in resting (contralateral) arm and leg during isometric contraction.

1. Blood flow in resting forearm and calf were measured plethysmographically in healthy young men during isometric contraction performed both as a handgrip and as a dorsiflexion of the foot. The isometric contraction was maintained for 2 min at one third maximal voluntary contraction for the handgrip and half maximal voluntary contraction for the dorsiflexion of the foot. In some experiments the possible influence on blood flow of inadvertent muscle activation in the resting limb was checked by recording the e.m.g.

Clinical Physiology: The Effect of Circulatory Occlusion on Isometric Exercise Capacity and Energy Metabolism of the Quadriceps Muscle in Man

Occlusion of the circulation to the quadriceps muscle for 20 min resulted in decreases in the muscle ATP and phosphorylcreatine (PC) contents of 1 and 32 per cent, respectively, and increases in ADP and AMP of 7 and 37 per cent. Decrease in PC was statistically significant after 4 min of occlusion, suggesting that the local intramuscular oxygen store was sufficiently depleted at this time as to be limiting to normal mitochondrial function. Pyruvate and lactate concentrations in muscle and the lactate to pyruvate ratio were significantly increased after 15 min of occlusion but not before. The calculated local oxygen store in the muscle was 2.0 mmol O2 - (kg dry muscle)-1. Local oxygen store depletion after 4 and 10 min of occlusion was estimated to be 40-50 and 90-100 per cent complete. Increasing time of pre-exercise occlusion resulted in decreased isometric endurance capacity. The observed decreases in endurance, however, were far greater than could be accounted for by any parallel decrease in the local muscle energy stores.

Extraction of endogenous plasma triglycerides by the working human forearm muscle in the fasting state.

The extraction of triglycerides (TG) by the working forearm was determined in eight healthy fasting men, both by the measurement of chemical arterial-deep venous (a-dv) TG differences and by the a-dv differences in TG radioactivity after endogenous labeling with tritiated palmitate. Measurements were made before and then during nicotinic acid infusion. Correction for plasma water shift in the forearm vasculature was made by estimating the (125I)albumin activity after an intravenous injection. The overall mean value +/- S.E.M. without and with nicotinic acid was for TG arterial concentration (mumol/1) 713 +/- 153 and 695 +/- 140, TG a-dv concentration difference (mumol/1)-14 +/- 7 and -6 +/- 4, TG arterial radioactivity (cpm/ml) 1650 +/- 469 and 1471 +/- 342, TG a-dv radioactivity difference 12 +/- 24 and -2 +/- 13. The average standard errors for the determinations of triglycerides were 0.85% and 1.5% for the chemical and the isotope methods, respectively. In conclusion, no significant average a-dv difference in TG concentration as determined by either the chemical or the isotope method was detected. With the standard errors achieved, however, a-dv differences of less than around 20 mumol/lcould not be discovered. Such an extraction of endogenous plasma TG could, if oxidized, account for about 25% of the oxygen extraction by the eercising forearm.

Myocardial Protection During Aortic Valve Replacement. Cardiac Metabolism and Enzyme Release Following Hypothermic Cardioplegia

Cardiac metabolism following hypothermic potassium cardioplegia was studied in 23 patients undergoing isolated aortic valve replacement. All had normal coronary arteries. Cardioplegia was induced by infusing 700-1 000 ml of cold Ringers acetate containing 20 mekv K+ selectively into the left coronary artery. Simultaneous blood samples were taken from the radial artery, a central vein and from the coronary sinus before and after cardioplegia. The PO2, O2-saturation and content, PCO2, pH, lactate, glucose, potassium, myoglobin, total creatine kinase (CK), its isoenzyme CK-MB, aspartate aminotransferase (ASAT) and alanine aminotransferase (ALAT) were assessed. Before bypass lactate was extracted by the heart. During the initial 10 to 20 min after cardioplegia there was a marked release of lactate in the coronary sinus. Myoglobin concentration and CK-MB serum activity peaked during the first 4 hours after the release of the aortic cross-clamping. In order to determine the best indicator of myocardial damage after cardioplegia, duration of extracorporeal circulation (ECC-time), aortic occlusion time (AOT), mean myocardial temperature (MMT) and the product of AOT and MMT, referred to as time-temperature area (TTA), were related to possible indicators of myocardial injury, such as enzyme and myoglobin release. The TTA was the best way of expressing the degree of exposure of the heart to ischaemia. The CK-MB to peak area (CK-MB max area) was the best indicator of the degree of ischaemic injury sustained by the heart during operation.

The relation between carbohydrate extraction by the forearm and arterial free fatty acid concentration in man: I. Forearm work with nicotinic acid infusion

To see if the magnitude of carbohydrate extraction by working skeletal muscle in man is inversely correlated with the arterial free fatty acid (FFA) concentration as in the heart, eighteen healthy men were studied during dynamic forearm work with and without nicotinic acid. The extraction or release of glucose, lactate and pyruvate was determined by the simultaneous sampling of blood from the brachial artery (a) and a deep vein (dv) of the active forearm. Nicotinic acid decreased the arterial FFA concentration from 498 +/- 53 to 134 +/- 12 mumol per litre plasma and this caused a decrease in calculated extraction of FFA. However, it did not affect the extraction of glucose, which was of a magnitude similar to one third of the oxidative metabolism in both situations. One of the possible reasons of this difference compared to the human heart muscle is that the exercising skeletal muscle may utilize stored substrate to a greater extent, which makes possible shifts in substrate utilized for oxidation without changes in substrate extraction. Another reason may be that FFA utilization covers a far smaller proportion of oxidative metabolism in skeletal than in heart muscle already before nicotinic acid.

Prevalence of ECG findings in 18-19 year old Swedish men.

2268 consecutive men, 18-19 years of age, were examined at an enlistment centre regarding their health, some anthropometric variables and electrocardiogram. ECG items according to the modified Minnesota code [1] were found in 230 subjects (10%). Most common ECG findings were T wave abnormalities (2.2%). Heart rate was higher in the groups with QRS axis deviation, T wave items, sinus tachycardia and supraventricular ectopic beats. Systolic and/or diastolic blood pressure was increased in the groups with T wave items, sinus tachycardia and ventricular ectopic beats. A dysfunction of the autonomic tone can often be suspected as a cause of the abnormality, especially in the groups with tachycardia, T wave changes, AV block grade I and AV junctional rhythm. An ECG recording during orthostasis was considered to be of value to clarify the nature of the ECG abnormality.

Adenosine in cold blood cardioplegia – a placebo-controlled study

OBJECTIVE Adenosine as an additive in blood cardioplegia is cardioprotective in animal studies, but its clinical role in myocardial protection remains controversial. The aim of this study was to investigate whether the addition of adenosine in continuous cold blood cardioplegia would enhance myocardial protection. METHODS In a prospective double-blind study comparing adenosine 400 μmol l(-1) to placebo in continuous cold blood cardioplegia, 80 patients undergoing isolated aortic valve replacement were randomized into four groups: antegrade cardioplegia with adenosine (n = 19), antegrade cardioplegia with placebo (n = 21), retrograde cardioplegia with adenosine (n = 21) and retrograde cardioplegia with placebo (n = 19). Myocardial arteriovenous differences in oxygen and lactate were measured before, during and after aortic occlusion. Myocardial concentrations of adenine nucleotides and lactate were determined from left ventricular biopsies obtained before aortic occlusion, after bolus cardioplegia, at 60 min of aortic occlusion and at 20 min after aortic occlusion. Plasma creatine kinase (CK-MB) and troponin T were measured at 1, 3, 6, 9, 12 and 24 h after aortic occlusion. Haemodynamic profiles were obtained before surgery and 1, 8 and 24 h after cardiopulmonary bypass. Repeated-measures analysis of variance was used for significance testing. RESULTS Adenosine had no effects on myocardial metabolism of oxygen, lactate and adenine nucleotides, postoperative enzyme release or haemodynamic performance. When compared with the antegrade groups, the retrograde groups showed higher myocardial oxygen uptake (17.3 ± 11.4 versus 2.5 ± 3.6 ml l(-1) at 60 min of aortic occlusion, P < 0.001) and lactate accumulation (43.1 ± 20.7 versus 36.3 ± 23.0 µmol g(-1) at 60 min of aortic occlusion, P = 0.052) in the myocardium during aortic occlusion, and lower postoperative left ventricular stroke work index (27.2 ± 8.4 versus 30.1 ± 7.9 g m m(-2), P = 0.034). CONCLUSIONS Adenosine 400 μmol l(-1) in cold blood cardioplegia showed no cardioprotective effects on the parameters studied. Myocardial ischaemia was more pronounced in patients receiving retrograde cardioplegia.

The Effect of Noradrenaline and of Increased Sympathetic Activity on the Hyperemia following Short and Prolonged Forearm Work

Forearm blood flow was measured plethysmographically after 5- and 55-min forearm work. While the post-exercise peak flow was essentially the same in both situations, venous PCO2, H+, lactate, K+, and osmolality were lower during and after prolonged work. It was concluded that they could not have acted as major flow-increasing factors unless the sensitivity to vasoactive stimulation was changed. The sensitivity to adrenergic stimuli was then tested by noradrenaline infusion and lower body low pressure, which evoked almost the same flow reduction after long and short term work. The infusion after prolonged work was, however, followed by a marked flow increase which could be blocked by propranolol, indicating a qualitative change in sensitivity. However, the change in adrenergic sensitivity seems not to be great enough to be the factor maintaining flow during prolonged work.

Myocardial metabolism during aortic valve replacement. III: Continuous infusion of cold blood for cardioplegia

Myocardial energy metabolism during hypothermic potassium cardioplegia with blood as the cardioplegia vehicle was studied in eight patients undergoing aortic valve replacement. Cardiac arrest was induced with a single bolus infusion and maintained by continuous perfusion. Myocardial biopsies were taken from the left ventricle 10 min after aortic cross-clamping (a.c.) and immediately before declamping (d.c.) and were analyzed for ATP, creatine phosphate (CP), creatine (C) and lactate. The interindividual range of myocardial temperature was 15-21 degrees a.c. and 17-22 degrees C immediately before d.c. The ATP concentration decreased (12.7 +/- 3.9-10.4 +/- 3.5 mmol X kg-1 dry muscle), the lactate concentration increased (102 +/- 30-156 +/- 8 mmol X kg-1 d.m.), and the total creatine (CP + C) remained constant. Induction of cardioplegia by blood resulting in a mean myocardial temperature of 19 degrees C could not prevent anaerobic metabolism. The changes in ATP levels between 10 min after a.c. and just before d.c. were small, however, indicating that oxygen delivery during continuous blood cardioplegia at a myocardial temperature of c. 20 degrees C prevented further loss of ATP. The lactate concentration, however, increased markedly between 10 min after a.c. and d.c., demonstrating that a significant proportion of the total metabolism was anaerobic.

Insulin and substrate exchange in the forearm during prolonged forearm work

Forearm exchange of insulin and uptake of oxygen, glucose and free fatty acids (FFA) were studied during 120 min forearm work in six healthy male volunteers. At rest the arterial-deep venous difference of insulin was zero. At the onset of work release of insulin occurred, which continued at constant rate throughout the work despite unaltered arterial insulin concentration. Extractions of oxygen, glucose and FFA were of similar magnitudes at 120 as at 15 min work, while lactate release decreased with time. It is concluded that (1) a significant insulin release from muscle tissue or its vascular bed occurs and continues at undiminished rate during prolonged work, (2) a substantial amount must be bound in the tissue, unless local synthesis takes place and (3) despite this loss of insulin from the forearm no major change in glucose and FFA extraction occurs with duration of work.