Noninvasive continuous arterial pressure measurements in the assessment of acute, severe central hypovolemia.

UNLABELLED: Acute, severe hypovolemia is a medical emergency. Traditional vital sign parameters allow no optimal triage. High predictive power of finger plethysmography-based stroke volume (SV) and pulse pressure (PP) was recently suggested. To assess the performance of the PP and SV parameters, lower body negative pressure of -40 mmHg, than -60 mmHg - corresponding to moderate and severe central hypovolemia - was applied in 22 healthy males (age 35 ± 7 years). Slow breathing induced fluctuations in the above indices, characterized by stroke volume variability (SVV), and pulse pressure variability (PPV), were assessed. Responses in heart rate (HR) and shock index (SI) were also studied. Discriminative capacity of these parameters was characterized by the area under the ROC (receiver operating characteristic) curves (AUC). RESULTS: In comparison of baseline to severe central hypovolemia SV, PP, HR, and SI showed good discriminating capacity (AUC 99%, 88%, 87%, and 93%, respectively). The discriminating capacity of SVV and PPV was poor (77% and 70%, respectively). In comparison of moderate and severe hypovolemia, the discriminating capacity of the studied parameters was uniformly limited. CONCLUSIONS: Plethysmography-based SV and PP parameters can be used to detect acute severe volume loss. Sensitive parameters discriminating moderate and severe central hypovolemia are still lacking.

Hemodynamic effects of slow breathing: does the pattern matter beyond the rate?

PURPOSE: Patterned breathing allows standardized serial measurements of heart rate variability and baroreflex indices. The slow breathing augments these parameters, and regular exercises, including yoga breathing practices with even respiratory rates have long-term beneficial effects in cardiovascular diseases. The role of temporization of breathing phases, i.e. the ratio of expiration to inspiration, is not known. In order to characterize the hemodynamic and autonomic responses during varying breathing phases 27 volunteers performed three short breathing sessions at 6/minutes frequency with 5:5, 3:7 and 7:3 inspiration expiration ratios. RESULTS: The immediate responses in arterial pressure and heart rate were negligible. The time domain parameters of heart rate variability (SDRR, PNN50,RMSSD) increased significantly with patterned breathing. So did the spontaneous baroreflex gain of increasing sequences (up-BRS, from 12 ± 7 to 17 ± 10 ms/mmHg, p < 0.05), and the cross-spectral low frequency gain, the LFalpha (from 11 ± 7 to 15 ± 7 ms/mmHg, p < 0.05). None of these parameters differed significantly from each other while using any of tested inspiratory-expiratory patterns. CONCLUSION: The major determinant of autonomic responses induced by slow patterned breathing is the breathing rate itself. From our observations, it follows that slow breathing exercises performed either with diagnostic or therapeutic purpose could be simplified, allowing more extensive investigations.

Oesophageal acid stimulation in humans: does it alter baroreflex function?

The aim of this study was to investigate if oesophagel acid stimulation (Bernstein test) had an influence on heart rate and blood prsure variability and baroreflex gain. We compared the cardiovascular responses in 10 patients with established gastro-esophageal reflux disease (Group 1) and 10 control subjects (Group 2) during esophageal saline and 0.1 mol/l hydrochloric acid instillation. Indices of heart rate and blood pressure variability and baroreflex gain (derived from linear spontaneous sequences and cross spectral analysis) were calculated. In Group 1 the standard deviation of RR intervals (SDRR: 46 ms vs 51 ms, p=0.030) and the root mean square of successive differences (RMSSD: 24 ms vs. 26 ms p=0.027) were significantly lower during acid infusions, than during saline. We found no significant difference in minimum, maximum and mean RR intervals and systolic blood pressures and in the percentage of RR intervals, which differed from adjacent cycles by more than 50 ms (PNN50). The power spectra of RR intervals in the high frequency band tended to be lower during acid infusion (p=0.055). There was no significant difference in blood pressure spectra, neither in low nor in high frequency band. In Group 2 there was no significant difference between any parameters measured during acid and saline. The baroreflex gain was not changed during the studied conditions in any group. Neither increased vagal tone, nor increased vagal variability occurred and the baroreflex gain was not altered during oesophageal acid simulation.

Severe cardiovascular autonomic dysfunction in a patient with Guillain-Barre syndrome: a case report.

Autonomic dysfunction is a frequent and severe complication of Guillain-Barre syndrome. It is often responsible for cardiovascular abnormalities, even cardiac arrest. We report a 49-year-old patient, who suffered from Guillain-Barre syndrome necessitating mechanical ventilation. He showed wide fluctuations of blood pressure and heart rate spontaneously or in relation with medical procedures. Though heart rate variability (HRV) and baroreflex sensitivity (BRS) values derived from different methods were extremely low, vigorous stimuli, like eyeball pressure test and carotid sinus massage, produced exaggerated responses, like severe bradycardias, hypotension and cardiac arrest. Despite the plasma exchange and supportive therapies, the patient finally developed adult respiratory distress syndrome (ARDS), sepsis and died due to septic shock.

[Cardiovascular autonomic regulation following orthoptic heart transplantation]. / A cardiovascularis autonóm reguláció vizsgálata orthotopicus szívátültetést követóen.

Numerous recent observations have indicated autonomic reinnervation of transplanted human hearts. In order to assess autonomic regulation 5 patients were studied 1 to 5 years following cardiac transplantation. A series of tests were performed, including blood pressure and ECG recordings on rest, during 15/min patterned breathing, isometric handgrip exercise, and Valsalva manoeuvre. The time domain indices (SDRR, pNN50, rMSSD) and the frequency domain indices of heart rate variability were also studied. Among the five patients under study only one exhibited features compatible with both sympathetic and parasympathetic reinnervation. Traditional autonomic reflex tests and the analysis of time and frequency domain indices of HRV serve as simple tool in primary assessment of cardiac reinnervation.

Effect of postural changes on arterial baroreflex sensitivity assessed by the spontaneous sequence method and Valsalva manoeuvre in healthy subjects.

The objective of this study was to compare the baroreflex sensitivity (BRS) assessed by the new, non-invasive, spontaneous sequence method (BRS-sequence) with the Valsalva manoeuvrebased BRS. Fourteen healthy volunteers were studied in the supine position, during 60 degrees head-up tilt (HUT) and during -30 degrees head-down tilt (HDT). Blood pressure and R-R intervals were continuously and non-invasively recorded using a Finapres device. The BRS-sequence was assessed by analysing the slopes of spontaneously occurring sequences of three or more consecutive beats in which systolic blood pressure and R-R interval of the following beat increased or decreased in the same direction in a linear fashion; it was compared with data obtained during the Valsalva manoeuvre in each position. The time and frequency domain indices of R-R interval variability were also evaluated. The mean difference of BRS between the two non-invasive methods was 3.86 ms/mmHg with a standard deviation of 9.14 ms/mmHg. BRS was decreased during HUT and increased during HDT as assessed by both techniques. The changes in BRS were associated with vagal withdrawal and sympathetic activation during HUT and enhancement in the cardiac vagal tone and reduction in the sympathetic activity during HDT. We conclude that the BRS-sequence technique provides a reliable method to study the neural control of the circulation, although the body position in consecutive measurements needs to be standardized.

Short-term monitoring of the vascular resistance of the human skin microvasculature.

OBJECTIVE AND METHOD: Laser Doppler flowmetry is a non-invasive tool in assessing the temporary changes of skin microcirculation. Another non-invasive equipment the Finapres 2300 finger blood pressure monitor provides a continuous blood pressure signal. The combination of the two devices allows short-term monitoring of the changes in the resistance of skin microvasculature. In order to assess the role of skin blood vessels in physiological responses to complex reflex tests Valsalva manoeuvre was performed by 12 healthy volunteers. For comparison a thermal stimulation (cold pressor) test was also done. RESULTS: The two tests resulted in skin blood flow responses of similar magnitude. The changes in calculated regional peripheral resistance (dRPR) indicated that both responses involved active vasoconstrictor mechanisms. It is of importance that the active vasoconstriction could be documented only at the late strain phase (V2) but not in the early strain phase (V1) of the Valsalva manoeuvre (%dRPR in V1 = 0.14 vs. V2 = 0.96, p < 0.05). CONCLUSIONS: In conclusion our findings support the theory that changes in the tone of the skin blood vessels parallel the changes in systemic vasculature in response to complex reflex tests. This is the first report which documents the feasibility of the continuous monitoring of the regional peripheral resistance.

[Management of severe orthostatic hypotension by head-up-tilt posture and administration of fludrocortisone]. / Súlyos fokú orthostaticus hypotonia kezelése "head-up-tilt" fektetéssel és fludrocortisonnal.

A case of a 66-year-old man with recurrent episodes of syncope is reported. The syncopal attacks started five years ago in sitting and standing positions. At the time of admission the fainting attacks occurred 2-3 times per day. The diagnostic tests revealed severe orthostatic hypotension. The medical treatment was started with salt enriched diet and fludrocortisone. The efficacy of the therapy was tested by using the tilt table test with a self developed computer system consisting of a non-invasive finger blood pressure monitor and ECG. The orthostatic tolerance improved with the medical therapy, however remained unsatisfactory for the patient's daily activity. Though the patient had less frequent symptoms, he had still sustained episodes of recurrent syncopes. The medical therapy was than combined with sleeping in the 15 degrees head-up-tilt position. The repeat tilt table test was performed two weeks after initiation of the 15 degrees head-up-tilt sleeping. The orthostatic tolerance was markedly improved. The patient became free of symptoms and during a four-week follow-up his condition remained stable. At the control the patient reported about deterioration of his symptoms as a result of the discontinuation of sleeping in "head-up-tilt" position for two weeks. The objective signs leading to aggravate his symptoms was documented by the tilt table test. We reinstituted the "head-up-tilt" sleeping in his therapeutic management.

The mechanism of blood pressure variability. Study in patients with fixed ventricular pacemaker rhythm.

BACKGROUND: Several studies have shown that heart rate variability plays an anti-oscillatory role in the regulation of blood pressure variability in humans. We tested whether systolic blood pressure variability in patients with a fixed ventricular pacemaker rhythm differs from that in patients with sinus rhythm. METHODS AND RESULTS: In 18 patients with a fixed ventricular pacemaker rhythm and in ten age-matched patients with sinus rhythm the systolic blood pressure oscillation and the low and high-frequency spectral components of systolic blood pressure were studied in the resting supine position during spontaneous breathing and during forced deep ventilation of 6 cycles.min-1. Patients with a pacemaker had a higher amplitude of systolic blood pressure oscillation than control subjects during spontaneous breathing (13.5 +/- 2.0 mmHg vs 6.4 +/- 1.6 mmHg, P = 0.035), and a slight but not significant difference also persisted during forced deep ventilation 19.0 +/- 2.3 mmHg vs 15.0 +/- 2.3 mmHg, P = 0.18). The increment in systolic blood pressure fluctuation from spontaneous breathing to forced deep ventilation was less marked in the pacemaker group than in the control subjects (40% vs 130%, P = 0.43). Although all the systolic blood pressure spectral components of the pacemaker patients were higher during both spontaneous breathing and forced deep ventilation, the differences between the two groups did not reach statistical significance. CONCLUSIONS: Our observations in patients with a fixed ventricular pacemaker rhythm suggest that the mechanical effects on the intrathoracic vessels and the consecutive stroke volume changes are responsible for respiration-related systolic blood pressure oscillation and reflex systolic blood pressure changes.

[Continuous non-invasive blood pressure monitoring in the diagnosis of pacemaker syndrome]. / Folyamatos, noninvazív vérnyomásmérés a pacemaker szindróma diagnózisában.

The drop in blood pressure coinciding with the atrioventricular dyssynchrony plays an important role in the genesis of pacemaker syndrome. The diagnosis is often based on continuous blood pressure recording. Formerly the continuous blood pressure monitoring could only be performed by invasive methods. The authors demonstrate the feasibility of a new non invasive continuous blood pressure recorder, the Finapres 2300, by presenting illustrative case reports. The authors recommend more widespread use of non invasive haemodynamic monitoring for the diagnosis of pacemaker syndrome.