The association between muscle EMG and perfusion in knee extensor muscles

The relationships between electromyographic (EMG) activity and force as well as muscle blood flow and work have been well established. However, the association between muscle blood flow and EMG activity remains unsolved. Thus, to test the hypothesis that muscle EMG activity relates to muscle perfusion in different compartments of the quadriceps femoris (QF) muscle, 12 healthy male subjects were studied. During two very submaximal exercise bouts, at different exercise intensities, oxygen labelled radiowater and positron emission tomography were used to measure muscle perfusion. In addition, produced force of knee extensors and muscle EMG activity in the vastus lateralis (VL), vastus medialis (VM) and rectus femoris (RF) muscles were recorded during both exercise bouts. Although the exercise intensity and average force production was higher during the second exercise bout (38 +/- 15 versus 51 +/- 17 N; P = 0.007), the mean EMG activity was lower (RF; P<0.001) or unchanged (VL; P = 0.722 and VM; P = 0.640). During the second exercise period, perfusion also remained unchanged in the entire QF muscle (P = 0.223) and in its separate muscles (VL, P = 0.703; VM, P = 0.141; RF, P = 0.113) in a group level. However, the individual changes in muscle perfusion were tightly related to changes in muscle EMG activity in VL (r = 0.84; P = 0.002) and VM (r = 0.68; P = 0.015) but poorly in the RF muscle (r = 0.40; P = 0.257). In conclusion, the different associations between muscle perfusion and EMG activity in different QF muscles suggests specific functional role of the vasti muscles and the RF muscle.     

Contraction-induced [18F]-fluoro-deoxy-glucose uptake can be measured in human calf muscle using high-resolution PET

Contraction-induced glucose uptake can be imaged and quantified by the use of positron emission tomography (PET). In the human extremities, such data may reveal important information regarding the in vivo mechanical function of e.g. the force transmitting tissues such as tendons. However, to investigate structures of limited size, a PET scanner with high resolution is required. We tested the potential of the recently developed high-resolution brain PET scanner (ECAT HRRT) for imaging of human lower extremities. [18F]-fluoro-deoxy-glucose uptake following voluntary and stimulated isometric muscle contractions was studied in a 30-year-old male. The results showed that the activated muscle or muscles are clearly delineated in the high-resolution PET images. Furthermore, the load-induced gain in tendon uptake was clearly visualized. In conclusion, the HRRT scanner is an appropriate tool for investigating physiological processes within the human extremities, and the very high resolution yields a potential for more accurate conclusions when target tissues are limited in size.     

Effect of exercise intensity on oxygen consumption kinetics in non-exercising muscle during exercise

This study examined the effect of exercise intensity on the kinetics of muscle oxygen consumption in non-exercising forearm flexor muscles (VO(2mf)) during exercise. Seven healthy male subjects performed cycling exercise for 60 min at 30% of maximal oxygen consumption (%VO(2max)) and 30 min at 50% VO(2max) on separate days. The VO(2mf) values at rest and during exercise were measured by near-infrared spectroscopy. The VO(2mf) at 30% VO(2max) significantly increased to 1·2 ± 0·1-fold over resting value at 20 min after the beginning of exercise (P<0·05) and remained constant within 1·2- to 1·3-fold over resting value until 60 min during exercise. The VO(2mf) at 50% VO(2max) significantly increased to 1·2 ± 0·1-fold over resting value at 15 min after the beginning of exercise (P<0·05). Subsequently, the VO(2mf) at 50% VO(2max) increased with time to 1·3 ± 0·1-fold over resting value at 20 min after the beginning of exercise and to 1·5 ± 0·2-fold over resting value at 30 min. The VO(2mf) 15-30 min of exercise at 50% VO(2max) was significantly higher than that at 30% VO(2max) (P<0·05). These data suggest that the increase in VO(2mf) has a time lag from the beginning of exercise, and the kinetics of VO(2mf) during exercise differs with exercise intensity. Therefore, we conclude that the kinetics of VO(2mf) during exercise is dependent on exercise intensity.     

Regional cerebral blood flow and oxygen metabolism during migraine with and without aura

Eleven cases of migraine with and without aura were investigated with positron emission tomography (PET). Regional cerebral blood flow (rCBF), oxygen metabolism (rCMRO₂) and oxygen extraction (rOER) were measured during baseline ( n =11), aura ( n = 6), headache ( n = 10) and after treatment with sumatriptan ( n = 4). Data were analysed using and ROI-based approach from 26 different anatomically defined regions, and also an exploratory approach whereby all subjects were normalized to a stereotactic brain atlas; t -maps were constructed by depicting significant changes between states. The exploratory approach revealed a region corresponding to the primary visual cortex with significant reductions in rCBF (23.1%) and rCMRO₂ (22.5%), but no change in rOER during the headache phase compared to baseline. These data suggest that cerebral ischemia was not the primary cause of the attacks in these cases.     

Postexercise blood flow restriction does not enhance muscle hypertrophy induced by multiple‐set high‐load resistance exercise

To test the applicability of postexercise blood flow restriction (PEBFR) in practical training programmes, we investigated whether PEBFR enhances muscle hypertrophy induced by multiple‐set high‐load resistance exercise (RE). Seven men completed an eight‐week RE programme for knee extensor muscles. Employing a within‐subject design, one leg was subjected to RE + PEBFR, whereas contralateral leg to RE only. On each exercise session, participants performed three sets of unilateral knee extension exercise at approximately 70% of their one‐repetition maximum for RE leg first, and then performed three sets for RE + PEBFR leg. Immediately after completion of the third set, the proximal portion of the RE + PEBFR leg was compressed with an air‐pressure cuff for 5 min at a pressure ranging from 100 to 150 mmHg. If participants could perform 10 repetitions for three sets in two consecutive exercise sessions, the work load was increased by 5% at the next exercise session. Muscle thickness and strength of knee extensor muscles were measured before and after the eight‐week training period and after the subsequent eight‐week detraining period. There was a main effect of time but no condition × time interaction or main effect of condition for muscle thickness and strength. Both muscle thickness and strength increased after the training period independent of the condition. This result suggests that PEBFR would not be an effective training method at least in an early phase of adaptation to high‐load resistance exercise.     

Evaluation of oxygen uptake kinetics and oxygen kinetics of peripheral skeletal muscle during recovery from exercise in patients with chronic obstructive pulmonary disease

The biochemical features of skeletal muscle and its contribution to exercise intolerance in patients with chronic obstructive pulmonary disease (COPD) is under active investigation. Near-infrared spectroscopy (NIRS) can non-invasively provide information on the oxidative capacity of muscle. To clarify whether oxygenation of peripheral muscle is one determinant of exercise tolerance, we simultaneously examined the oxygen uptake (V O 2off) kinetics and oxygen kinetics of peripheral skeletal muscle evaluated by NIRS during recovery from exercise in COPD patients. Fifteen patients with COPD and five normal control subjects performed a symptom-limited incremental exercise test. On the following day, all patients performed a constant work rate exercise test while being monitored using NIRS continuously for changes in concentration of oxygenated haemoglobin (HbO2) and during expired gas analysis. We found that the time constant of during recovery from constant work rate exercise (V O 2off) and the time constant of V O 2off during recovery (tau V O 2off) were significantly longer in COPD patients than in normal control subjects. was inversely correlated with absolute values of forced expiratory volume in 1 s (FEV1.0) and FEV1.0 (% predicted). However, no significant correlation was found between and FVC (forced vital capacity), FEV1.0/FVC, or diffusing capacity of the lung for CO (DLCO). Moreover, was inversely correlated with maximal V O 2off and maximal work rate. In contrast, exhibited a significant positive correlation with tau V O 2off. These results indicate that V O 2off kinetics during recovery is related to re-oxygenation of peripheral skeletal muscle evaluated by NIRS in patients with COPD. Therefore, NIRS may be a useful tool to estimate the impairment of cardiopulmonary responses and re-oxygenation of peripheral skeletal muscle during the immediate recovery phase after exercise in COPD patients.     

Reproducibility and sensitivity of muscle reoxygenation and oxygen uptake recovery kinetics following running exercise in the field

The purpose of this study was to assess the reliability of postexercise near‐infrared spectroscopy (NIRS)‐derived measurements and their sensitivity to different exercise intensities in the field. Seventeen athletes (24·1 ± 5·6 year) repeated, on three occasions, two 2‐min submaximal shuttle‐runs at 40% and 60% of V_IFT (final speed of the 30–15 intermittent fitness test) and a 50‐m shuttle‐run sprint (Sprint), with (OCC) or without (CON) repeated transient arterial occlusions of the medial gastrocnemius during the postexercise period. NIRS variables (i.e. oxyhaemoglobin [HbO₂], deoxyhaemoglobin [HHb] and their difference [Hb_diff]) were measured continuously for 3 min after each exercise. Half‐recovery (½Rec) and mean response (MRT; monoexponential curve fitting) times of muscle reoxygenation and muscle oxygen uptake () recovery were calculated. Reliability was assessed using the typical error of measurement, expressed as a coefficient of variation (CV). Postexercise recovery of muscle reoxygenation revealed CVs ranging from 16·8% to 37·3%; CV for recovery ranged from 6·2% to 20·9%, with no substantial differences shown between NIRS variables and exercise intensities. While running, intensity did not affect MRT or ½Rec for muscle reoxygenation, and differences were found for recovery (e.g. [Hb_diff]‐ MRT = 28·7 ± 5·2, 34·2 ± 5·1 and 37·3 ± 6·2 s for 40%, 60% and Sprint, respectively, P<0·01). To conclude, the kinetics of postexercise NIRS measurements showed CV values ranging from 6% to 37%, with no substantial differences between exercise intensities or NIRS‐derived variables. However, exercise intensity did influence recovery kinetics, but not that of muscle reoxygenation in an occlusion‐free condition.     

Simultaneous quantification of myocardial perfusion,oxidative metabolism,cardiac efficiency and pump function at rest and during supine bicycle exercise using 1‐11C‐acetate PET – a pilot study

Background: PET using 1‐¹¹C‐acetate (ACE‐PET) applied at rest is used for measuring absolute myocardial blood flow (MBF) and oxidative metabolic rate (k_mono). We evaluated the feasibility of quantitative ACE‐PET during exercise. Methods: Five endurance athletes underwent dynamic PET scanning at rest and during supine bicycle stress. Exercise was maintained at a workload of 120 Watt for 17 min. The rate‐pressure product (RPP) was recorded repeatedly. MBF, k_mono in left (LV) and right (RV) ventricular wall, cardiac output (CO), cardiac efficiency and a lung uptake value reflecting left heart diastolic pressures were calculated from the PET data using previously validated models. Results: MBF increased from 0·71 ± 0·17 to 2·48 ± 0·25 ml min^?1 per ml, LV‐k_mono from 0·050 ± 0·005 to 0·146 ± 0·021 min^?1, RV‐k_mono from 0·023 + 0·006 to 0·087 + 0·014 min^‐1, RPP from 4·7 ± 0·8 to 13·2 ± 1·4 mmHg × min^?1 × 10³ and Cardiac Output from 5·2 ± 1·1 to 12·3 ± 1·2 l min ^?1 (all P < 0·001). Cardiac efficiency was unchanged (P = 0·99). Lung uptake decreased from 1·1 ± 0·2 to 0·6 ± 0·1 ml g^?1 (P < 0·001). Discussion: A number of important parameters related to cardiac function can be quantified non‐invasively and simultaneously with a short scanning protocol during steady state supine bicycling. This might open up new opportunities for studies of the integrated cardiac physiology in health and early asymptomatic disease.     

Effects of oxygen supplementation on cerebral oxygenation during exercise in chronic obstructive pulmonary disease patients not entitled to long-term oxygen therapy

Background: The rate of change (Δ) in cerebral oxygenation (COx) during exercise is influenced by blood flow and arterial O₂ content (CaO₂). It is currently unclear whether ΔCOx would (i) be impaired during exercise in patients with chronic obstructive pulmonary disease (COPD) who do not fulfil the current criteria for long‐term O₂ therapy but present with exercise‐induced hypoxaemia and (ii) improve with hyperoxia (FIO₂ = 0·4) in this specific sub‐population. Methods: A total of 20 non‐hypercapnic men (FEV₁ = 47·2 ± 11·5% pred) underwent incremental cycle ergometer exercise tests under normoxia and hyperoxia with ΔCOx (fold‐changes from unloaded exercise in O₂Hb) being determined by near‐infrared spectroscopy. Pulse oximetry assessed oxyhaemoglobin saturation (SpO₂), and impedance cardiography estimated changes in cardiac output (ΔQT). Results: Peak work rate and ΔCOx in normoxia were lower in eight O₂‘desaturators’ compared with 12 ‘non‐desaturators’ (P<0·05). Area under ΔCOx during sub‐maximal exercise was closely related to SpO₂ decrements in ‘desaturators’ (r = 0·92, P<0·01). These patients showed the largest improvement in peak exercise capacity with hyperoxia (P<0·05). Despite a trend to lower sub‐maximal ΔQT and mean arterial pressure with active intervention, ΔCOx was significantly improved only in this group (0·57 ± 0·20 versus 2·09 ± 0·42 for ‘non‐desaturators’ and ‘desaturators’, respectively; P<0·05). Conclusions: ΔCOx was impaired in non‐hypoxaemic patients with COPD who desaturated during exercise. Hyperoxic breathing was able to correct for these abnormalities, an effect related to enhanced CaO₂ rather than improved central haemodynamics. This indicates that O₂ supplementation ameliorates exercise COx in patients with COPD who are not currently entitled to ambulatory O₂ therapy.     

Resuscitation of severe but brief haemorrhagic shock with PFC in rabbits restores skeletal muscle oxygen delivery and does not alter skeletal muscle metabolism

Studies have demonstrated that perfluorocarbon (PFC) emulsions associated with hyperoxia improved whole body oxygen delivery during resuscitation of acute haemorrhagic shock (HS). Nevertheless the microcirculatory effects of PFC and the potential deleterious effects of hyperoxic reperfusion are still of concern. We investigated (i) the ability of a newly formulated, small sized and highly stable PFC emulsion to increase skeletal muscle oxygen delivery and (ii) the effect of hyperoxic reperfusion on skeletal muscle metabolism after a brief period of ischaemia using an original, microdialysis-based method that allowed simultaneous measurement tissue oxygen pressure (PtiO2) and interstitial lactate and pyruvate. These measurements were carried out in anaesthetised and ventilated (FiO2 = 1) rabbits subjected to acute HS (50% of blood volume withdrawal) and either resuscitated with a PFC emulsion diluted with a 5% albumin solution (16.2 g PFC per kg body weight) (n = 10) or with a modified fluid gelatin solution (Gelofusine) (n = 10). We found no difference between the two groups for the haemodynamic and haematological variables (except for the venous oxygen partial pressure). However, a significant difference was observed in the slope of the regression linear relationship exhibited between the mean arterial pressure (MAP) and the PtiO2, PFC group showing a much steeper slope than Gelofusine group. In addition, PtiO2 values increased linearly with decreasing haematocrit (Hct) values in PFC-resuscitated animals and decreased linearly with decreasing Hct values in Gelofusine-resuscitated animals. There were no differences between the two groups concerning the blood and interstitial lactate/pyruvate ratios suggesting no deleterious effect of hyperoxic resuscitation in skeletal muscle. In conclusion these results suggest that resuscitation of severe, but brief, HS with PFC increased skeletal muscle oxygen delivery without measurable deleterious effects.     

Cerebral metabolic rate of oxygen (CMRO2) in pig brain determined by PET after resuscitation from cardiac arrest

Aim

To assess the regional vulnerability to ischemic damage and perfusion/metabolism mismatch of reperfused brain following restoration of spontaneous circulation (ROSC) after cardiac arrest.

Method

We used positron emission tomography (PET) to map cerebral metabolic rate of oxygen (CMRO₂), cerebral blood flow (CBF) and oxygen extraction fraction (OEF) in brain of young pigs at intervals after resuscitation from cardiac arrest. After obtaining baseline PET recordings, ventricular fibrillation of 10 min duration was induced, followed by mechanical closed-chest cardiopulmonary resuscitation (CPR) in conjunction with i.v. administration of 0.4 U/kg of vasopressin. After CPR, external defibrillatory shocks were applied to achieve restoration of spontaneous circulation (ROSC). CBF and CMRO₂ were mapped and voxelwise maps of OEF were calculated at times of 60, 180, and 300 min after ROSC.

Results

There was hypoperfusion throughout the telencephalon at 60 min, with a return towards baseline values at 300 min. In contrast, there was progressively increasing CBF in cerebellum throughout the observation period. The magnitude of CMRO₂ decreased globally after ROSC, especially in cerebral cortex. The magnitude of OEF in cerebral cortex was 60% at baseline, tended to increase at 60 min after ROSC, and declined to 50% thereafter, thus suggesting transition to an ischemic state.

Conclusion

The cortical regions tended most vulnerable to the ischemic insult with an oligaemic pattern and a low CMRO₂ whereas the cerebellum instead showed a pattern of luxury perfusion.     

The effects of low-dose dopamine on splanchnic blood flow and oxygen uptake in patients with septic shock

Objective: To assess the effects of low-dose dopamine on splanchnic blood flow and splanchnic oxygen uptake in patients with septic shock. Design: Prospective, controlled trial. Setting: University hospital intensive care unit Patients: 11 patients with septic shock, diagnosed according the criteria of the 1992 American College of Chest Physicians/Society of Critical Care Medicine consensus conference, who required treatment with norepinephrine. Measurements and main results: Systemic and splanchnic hemodynamics and oxygen transport were measured before and during addition of low-dose dopamine (3 μg/kg per min). Low-dose dopamine had a marked effect on total body hemodynamics and oxygen transport. The fractional splanchnic flow at baseline ranged from 0.15 to 0.57. In 7 patients with a fractional splanchnic flow less than 0.30, low-dose dopamine increased splanchnic flow and splanchnic oxygen delivery and oxygen consumption. In 4 patients with a fractional splanchnic flow above 0.30, low-dose dopamine did not appear to change splanchnic blood flow. Conclusion: Low-dose dopamine has a potential beneficial effect on splanchnic blood flow and oxygen consumption in patients with septic shock, provided the fractional splanchnic flow is not already high before treatment. Received: 19 September 1995 Accepted: 21 September 1996     

Intramuscular water movement during and after isometric muscle contraction: evaluation at different exercise intensities

We aimed at evaluating the effect of isometric muscle contraction on intramuscular water movement at different exercise intensities. Seven men performed 1‐min isometric ankle dorsiflexion (20% and 50% maximal voluntary contractions [MVCs]) with a non‐magnetic custom‐made dynamometer, inside a magnetic resonance (MR) device. Axial diffusion‐weighted images were obtained before, during and at 1–20 min (1‐min interval) after the exercise to calculate the apparent diffusion coefficient (ADC) of the tibialis anterior. Under the same exercise condition, the concentration change of total haemoglobin (Hb) and myoglobin (Mb) (total Hb/Mb) within the tibialis anterior was assessed by performing near‐infrared spectroscopy before, during and after the exercise outside the MR device. The 20% MVC exercise significantly increased the ADC only at 1 min postexercise (P<0·01), whereas the ADC significantly increased during and at 2–20 min after the 50% MVC exercise (P<0·01). The 20% MVC exercise decreased the total Hb/Mb during exercise (P<0·01), but the value significantly increased at 1 min postexercise (P<0·01). The total Hb/Mb significantly decreased during the 50% MVC exercise, but significantly increased at 1–5 min postexercise (P<0·01). One‐minute moderate‐intensity isometric exercise activates intramuscular water movement during and after the exercise. This activation was found even after a low‐intensity exercise, but the effect was small and did not last long. The effect of intramuscular hyperaemia on the postexercise ADC elevation may be limited to the very early period after low‐ to moderate‐intensity exercises.     

急性心肌梗死早期病人首次与非首次排便过程中心肌耗氧量研究

[目的]探讨不同排便次数对急性心肌梗死(AMI)早期病人排便过程中心率、血压、心肌耗氧量(MVO2)变化的影响。[方法]通过多功能心电监护仪,记录23例AMI早期病人25例次排便过程中不同时段的心率和血压,比较首次排便组与非首次排便组排便过程中心率、血压及MVO2等指标的变化。[结果]两组排便过程中心率、血压及MVO2的变化趋势基本相同,但非首次排便组血压在便中前期较首次排便者明显升高。[结论]对于非首次排便的AMI病人,护理人员仍应提高警惕,加强排便知识宣教和排便中监护。     

急性心肌梗死早期病人首次与非首次排便过程中心肌耗氧量研究

[目的]探讨不同排便次数对急性心肌梗死（AMI）早期病人排便过程中心率、血压、心肌耗氧量（MVO2）变化的影响。[方法]通过多功能心电监护仪，记录23例AMI早期病人25例次排便过程中不同时段的心率和血压，比较首次排便组与非首次排便组排便过程中心率、血压及MVO2等指标的变化。[结果]两组排便过程中心率、血压及MVO2的变化趋势基本相同，但非首次排便组血压在便中前期较首次排便者明显升高[结论]对于非首次排便的AMI病人，护理人员仍应提高警惕，加强排便知识宣教和排便中监护。     

A regression analysis study of the primary somatosensory cortex during pain

Several functional imaging studies of pain, using a number of different experimental paradigms and a variety of reference states, have failed to detect activations in the somatosensory cortices, while other imaging studies of pain have reported significant activations in these regions. The role of the somatosensory areas in pain processing has therefore been debated. In the present study the left hand was immersed in painfully cold water (standard cold pressor test) and in nonpainfully cold water during 2 min, and PET-scans were obtained either during the first or the second minute of stimulation. We observed no significant increase of activity in the somatosensory regions when the painful conditions were directly compared with the control conditions. In order to better understand the role of the primary somatosensory cortex (S1) in pain processing we used a regression analysis to study the relation between a ROI (region of interest) in the somatotopic S1-area for the stimulated hand and other regions known to be involved in pain processing. We hypothesized that although no increased activity was observed in the S1 during pain, this region would change its covariation pattern during noxious input as compared to the control stimulation if it is involved in or affected by the processing of pain. In the nonpainful cold conditions widespread regions of the ipsilateral and contralateral somatosensory cortex showed a positive covariation with the activity in the S1-ROI. However, during the first and second minute of pain this regression was significantly attenuated. During the second minute of painful stimulation there was a significant positive covariation between the activity in the S1-ROI and the other regions that are known to be involved in pain processing. Importantly, this relation was significantly stronger for the insula and the orbitofrontal cortex bilaterally when compared to the nonpainful state. The results indicate that the S1-cortex may be engaged in or affected by the processing of pain although no differential activity is observed when pain is compared with the reference condition.     

Enhanced sympathetic nervous activity after intravenous propranolol in ischaemic heart disease: plasma noradrenaline splanchnic blood flow and mixed venous oxygen saturation at rest and during exercise

To study the mechanisms by which acute beta-adrenergic blockade may change the activity of the sympathetic nervous system we have measured haemodynamic responses including splanchnic blood flow in twenty-three patients with ischaemic heart disease at rest and during supine exercise before and after i.v. injection of 0.039 mmol (10 mg) dl-propranolol. After propranolol both at rest and on exercise blood pressure, cardiac output and heart rate decreased, while splanchnic vascular resistance increased; mixed venous oxygen saturation decreased whilst arterial oxygen saturation and oxygen uptake were unchanged. Plasma noradrenaline increased after propranolol, values correlating with mixed venous oxygen saturation and splanchnic vascular resistance, both at rest and during exercise before and after propranolol, only at rest was there any correlation with arterial blood pressure. The increase in sympathetic nervous activity after propranolol may be due to a reduction in cardiac output and thereby alteration of the metabolic state (oxygen or related factors) in tissues. Afferent neural signals from the tissues may play a significant role in the regulation of sympathetic nervous activity.     

Early adrenaline administration does not improve circulatory recovery during resuscitation from severe asphyxia in newborn piglets

Aim of the study

To investigate the effects of early intravenous adrenaline administration on circulatory recovery, cerebral reoxygenation, and plasma catecholamine concentrations, after severe asphyxia-induced bradycardia and hypotension.

Methods

One-day-old piglets were left in apnoea until heart rate and mean arterial pressure were less than 50 min⁻¹ and 25 mmHg, respectively. They randomly received adrenaline, 10 μg kg⁻¹ (n = 16) or placebo (n = 15) and were resuscitated with air ventilation and, when needed, closed-chest cardiac massage (CCCM). Eight not asphyxiated animals served as time controls.

Results

CCCM was required in 13 piglets given adrenaline and in 13 given placebo. Time to return of spontaneous circulation was: 72 (66–85) s vs. 77 (64–178) s [median (quartile range)] (p = 0.35). Time until cerebral regional oxygen saturation (CrSO₂) had increased to 30% was 86 (79–152) s vs. 126 (88–309) s (p = 0.30). The two groups did not differ significantly in CrSO₂, heart rate, arterial pressure, right common carotid artery blood flow, or number of survivors: 13 vs. 11 animals. Plasma concentration of adrenaline, 2.5 min after resuming ventilation, was 498 (268–868) nmol l⁻¹vs. 114 (80–306) nmol l⁻¹ (p = 0.01). Corresponding noradrenaline concentrations were 1799 (1058–4182) nmol l⁻¹vs. 1385 (696–3118) nmol l⁻¹ (ns). In the time controls, the concentrations were 0.4 (0.2–0.6) nmol l⁻¹ of adrenaline and 1.8 (1.3–2.4) nmol l⁻¹ of noradrenaline.

Conclusion

The high endogenous catecholamine levels, especially those of noradrenaline, may explain why early administered adrenaline did not significantly improve resuscitation outcome.