Cardiodynamic responses during seated and supine recovery from supramaximal exercise

Separate and combined influence of posture and sprint running on plasma volume changes

It is currently unknown whether any changes in plasma volume (PV) after sprint running are inherent to sprint running per se or are due to other confounding factors such as changes in posture. The purpose of the present study was to examine the independent effects of sprint running on PV changes. Eight females completed two trials on separate days: (1) a 30-s sprint on a non-motorised treadmill and (2) a control trial where no exercise was undertaken but blood samples were taken at identical time points as in the exercise trial. Changes in PV were calculated using haematocrit and haemoglobin. Post-sprint PV reductions were greater in the sprint than the control trial (mean: -17.7, SD=3.1% vs. mean: -7.5, s = 4.9, P<0.05, n=8). There were greater changes in PV in the sprint than the control trial in most sampling points. These data show that sprint running of only 30 s induces transient reductions in PV independently of posture change. The present findings suggest that PV changes due to sprint running should be routinely reported as well as the posture and the exact time in this posture.

Postexercise syncope: Wingate syncope test and effective countermeasure

Altered systemic haemodynamics following exercise can compromise cerebral perfusion and result in syncope. As the Wingate anaerobic test often induces presyncope, we hypothesized that a modified Wingate test could form the basis of a novel model for the study of postexercise syncope and a test bed for potential countermeasures. Along these lines, breathing through an impedance threshold device has been shown to increase tolerance to hypovolaemia, and could prove beneficial in the setting of postexercise syncope. Therefore, we hypothesized that a modified Wingate test followed by head-up tilt would produce postexercise syncope, and that breathing through an impedance threshold device (countermeasure) would prevent postexercise syncope in healthy individuals. Nineteen recreationally active men and women underwent a 60 deg head-up tilt during recovery from the Wingate test while arterial pressure, heart rate, end-tidal CO2 and cerebral tissue oxygenation were measured on a control day and a countermeasure day. The duration of tolerable tilt was increased by a median time of 3 min 48 s with countermeasure in comparison to the control (P < 0.05), and completion of the tilt test increased from 42 to 67% with the countermeasure. During the tilt, mean arterial pressure was greater (108.0 ± 4.1 versus 100.4 ± 2.4 mmHg; P < 0.05) with the countermeasure in comparison to the control. These data suggest that the Wingate syncope test produces a high incidence of presyncope, which is sensitive to countermeasures such as inspiratory impedance.

Effect of differences in post-exercise lactate accumulation in athletes' haemodynamics

To verify the relationship between exercise intensity and post-exercise haemodynamics, we studied haemodynamic and lactate responses during 10 min following 3 bicycle tests. Two tests were performed for 3 min at 70% and 130% of the workload corresponding to anaerobic threshold (70% W(at) and 130% W(at) tests), and 1 was performed until exhaustion at 150% of the maximum workload achieved during a previous incremental test (150% W(max) test). During the recovery period after the 150% W(max) test we observed the highest increases in blood lactate with respect to the baseline: at the 9th minute of recovery lactate concentration increased by +9.3 +/- 2.7, +6.4 +/- 3.1, and +1.1 +/- 0.9 mmol x L(-1) in the 150% W(max) (p > 0.05 with respect to the other protocol sessions), 130% W(at), and 70% W(at) tests, respectively. We also observed greater reductions in cardiac pre-load and systemic vascular resistance in the 150% W(max) test than in the 130% W(at) and 70% W(at) tests. However, the cardiac output response successfully faced the increased vasodilatation occurring during 150% W(max) test so that changes in mean blood pressure were similar in the 3 test conditions. This study shows that exercises that yielded different lactate concentrations also led to greater vasodilatation. Nevertheless, mechanisms controlling the cardiovascular apparatus successfully prevented a drop in blood pressure in spite of the cardiovascular stress.

Exercise related syncope, when it's not the heart

Syncope or pre-syncope in association with physical exercise may be the first indication of a dangerous underlying cardiovascular condition. Thus, the diagnostic workup of patients presenting with exercise-related syncope must include assessment of the risk for acute cardiac death. When potentially lethal conditions have been ruled out, several hypotensive syndromes that are associated with exercise should be considered. This review aims to give a concise overview of several forms of exercise- related functional hypotensive syndromes causing syncope, including the physiology of post-exercise hypotension. The focus is on underlying mechanisms, clinical considerations, and outlining treatment strategies for these syndromes.

Elevation of a patient's trunk and legs does not influence length of stay in the post-anesthesia care unit

CONTEXT

Patient recovery time after anesthesia depends on problem-oriented monitoring and individual assessment.

OBJECTIVE

To investigate the influence of patient positioning on post-anesthesia recovery time.

TYPE OF STUDY

Retrospective.

SETTING

Post-anesthesia care unit, Hospital das Clínicas, São Paulo.

METHODS

Data were obtained from patients recovering from anesthesia in a supine horizontal position or with their trunk and legs elevated at 30 degrees. Data were recorded every 30 minutes. The start time was considered to be the admission to the unit, and the final measurement was taken with the patient reached an Aldrete-Kroulik index of 10. The length of time until discharge was recorded.

RESULTS

442 patients recovering after general (n = 274) or regional anesthesia (n = 168) were assigned to be kept in a supine position or with their trunk and legs elevated. There was no difference in the medians for non-parametric results, between supine position (75 min, n = 229) and trunk and legs elevated (70 min, n = 213); p = 0.729. Patients recovered faster from regional anesthesia with trunk and legs elevated (70 min) than in the supine position (84.5 min), although not significantly (p = 0.097). There was no difference between patients recovering from general anesthesia, no matter the positioning (70 min; p = 0.493).

DISCUSSION

Elevated legs may supposedly improve venous return and cardiac output since spinal anesthesia blocks sympathetic system and considering leg-raising has been shown to improve cardiac output from hipovolemia. Our findings did not support this hypothesis. Some limitations included a retrospective collection of data that did not allow randomization for recovery position and the unregistered duration of the exposure to the anesthetic drugs.

CONCLUSIONS

There was no difference in anesthesia recovery time in relation to positioning patients supinely or with trunk and legs elevated.

Haemodynamic responses following intermittent supramaximal exercise in athletes

We aimed to investigate haemodynamics during active and passive recovery following repeated bouts of supramaximal exercise. Seven male athletes underwent two sessions of supramaximal exercise which consisted of a warm-up and of five bouts of cycling at the maximum speed possible for 30 s against a resistance equivalent to 150% of the maximum workload achieved in a previous incremental test. Bouts were separated by 1 min of recovery and followed by 10 min of recovery which was either active (pedalling at 40 W) or passive (completely rest seated on the cycle). Haemodynamic variables were evaluated by means of impedance cardiography. Heart rate (HR), stroke volume (SV), cardiac output (CO), mean blood pressure (MBP), thoracic electrical impedance (Z0) as an inverse index of central blood volume, and systemic vascular resistance (SVR) were assessed. The main findings were that active recovery, with respect to passive recovery, induced higher changes from baseline in HR (+29.1 +/- 4.5 versus +15.6 +/- 2.9 beats min(-1) at the 10th minute of recovery, P < 0.05), SV (+19.9 +/- 5.6 versus -6.4 +/- 3.3 ml, P < 0.01) and CO (+3.8 +/- 1.2 versus +0.4 +/- 0.2 l min(-1), P < 0.01). Furthermore, MBP was similar between the two kinds of recovery despite an increase in Z0 during passive compared to active recovery. These results suggest that the faster haemodynamic recovery towards baseline and the decrease in cardiac preload during passive recovery may be successfully prevented by cardiovascular regulatory mechanisms which include an increase in SVR, thus avoiding a drop in blood pressure.

Hemodynamics during active and passive recovery from a single bout of supramaximal exercise

The aim of this work was to study the differences in cardiovascular response during two modes of recovery [active (AR): pedalling at 40 W; and passive (PR): complete rest seated] from a single bout of supramaximal exercise. Eight male amateur soccer players underwent two supramaximal cycle-ergometer tests, each consisting of pedalling against a resistance equivalent to 150% of the maximum workload achieved in a previous incremental test, followed by randomly assigned AR or PR. Cardiodynamic variables were obtained using an impedance cardiograph. Subjects were also connected to a sphygmomanometer, for systolic and diastolic blood pressure, and to a metabolimeter for oxygen uptake (VO(2)) assessments. We measured: heart rate (HR), stroke volume (SV), cardiac output (CO), the inverse of myocardial contractility calculated as pre-ejection period/left ventricular ejection time ratio (PEP/LVET), mean blood pressure (MBP), thoracic electrical impedance ( Z(0)) as an index of central blood volume, and arterio-venous oxygen difference (A-V O(2) Diff.). PR caused a lower CO compared to AR [mean (SE): 7 (0.7) vs. 10.4 (0.6) l.min(-1 )at the 5th min of recovery] due to lower HR [106.2 (3.6) vs. 121.8 (4.5) bpm at the 5th min of recovery], SV [67.1 (5) vs. 86.1 (4.8) ml at the 5th min of recovery], and PEP/VET values [0.44 (0.007) vs. 0.39 (0.015) at the 5th min of recovery]. No differences were found in MBP and Z(0) between PR and AR [95.1 (1.9) vs. 92.3 (2.7) mmHg and 26.2 (1.1) vs. 26.6 (1) Omega respectively at the 5th min of recovery], while A-V O(2) Diff. values were higher during AR than during PR [108.8 (4.3) vs. 75.2 (5.4) ml.l(-1) at the 5th min of recovery]. Thus, although after a single bout of supramaximal exercise SV and CO are lower during PR than during AR, these differences are not due to an impairment of cardiovascular function, but are fully explained by the lesser muscular engagement that leads to a reduction in stimuli deriving from mechanoreceptors and central commands, thus causing a faster return of myocardial contractility and HR to resting values.