Sažetak | Cilj istraživanja: Svrha je rada istražiti može li primjena kratkotrajne visokoslane dijete utjecati na cerebrovaskularnu reaktivnost i sistemsku hemodinamiku kod mladih zdravih ispitanika, u odgovoru na fiziološke podražaje (ortostatski test, hiperkapniju (test zadržavanja daha, BHT), hipokapniju izazvanu hiperventilacijom i hiperoksiju).
Nacrt studije: Kontrolirana intervencijska studija u kojoj su svi ispitanici u istom protokolu, s ponovljenim istovjetnim mjerenjima.
Ispitanici i metode: Dvadeset je sedam osoba (Ž:21, M:6, dobni raspon 19-24) bilo na sedmodnevnoj dijeti s malo soli (NS; <2,3 g NaCl/dan), a nakon toga sedmodnevnoj visokoslanoj dijeti (VS; >11,2 g NaCl/dan). Nakon oba dijetna protokola analizirani su krv i urin te su provedena antropometrijska mjerenja. Arterijski krvni tlak, otkucaji srca, promjenjivost srčane frekvencije, moždani i sistemski hemodinamski parametri mjereni su istovremeno s transkranijalnim dopplerskim ultrazvukom i The Task Force® Monitorom, prije i nakon navedenih podražaja.
Rezultati: Ispitanici su ostali normotenzivni tijekom oba dijetna protokola. U odgovoru na ortostatski test, smanjile su se vrijednosti moždanog protoka krvi (MPK), dijastoličkog moždanog protoka krvi (DMPK) i integrala brzine u vremenu (VTI). Povisile su se vrijednosti indeksa moždane pulzatilnosti (IMP) oba puta, a vrijednosti otpora moždane cirkulacije (OMC) kod VS dijete. U sistemskoj se cirkulaciji povisio srčani minutni volumen (SMV), a smanjio ukupni periferni otpor (UPO). Uslijed hiperkapnije značajno su povišene vrijednosti MPK-a, VTI-a, DMPK-a i sistoličkog moždanog protoka krvi (SMPK), a smanjene vrijednosti OMC-a. Bilježi se značajan pad srčane frekvencije (SF) nakon oba puta. Porast udarnog volumena (UV) značajan je u NS, a u NS i VS pad SMV-a i indeksa SMV (ISMV). Hipokapnija je dovela do pada tlaka moždane perfuzije (MPT), MPK-a, VTI-ja, DMPK-a, SMPK-a, a porasta vrijednosti OMC-a i IMP-a, kao i porasta SF-a, SMV-a i ISMV-a, a pada vrijednosti sistemskih tlakova te UPO-a i IUPO-a. Hiperoksija je dovela do nižih vrijednosti moždanih tlakova, povišenog IMP, sistemski niže SF, SMV i ISMV. Koncentracije noradrenalina i vanililmandelične kiseline u urinu smanjene su kod VS dijete. Visokoslana dijeta uzrokovala je prigušenje odgovora simpatikusa mjereno NF/VF te slabljenje baroreceptorskog odgovora u odnosu na niskoslanu dijetu kod ortostatskog podražaja i kod hiperventilacije.
Zaključak: Rezultati sugeriraju da je MPK bio očuvan kod VS dijete. Održan MPK kod VS dijete dio je cerebrovaskularnog odgovora s promjenom otpora, prigušenim BRS i simpatičkom aktivnošću na ortostatski test. Osim porasta UV u NS kod BHT, u ostalim provokacijskim testovima nema razlike u fiziološkom odgovoru između NS i VS dijete. Međutim, simpatički odgovor je prigušen, ne samo u ortostazi, nego i u hiperventilaciji kod VS dijete. |
Sažetak (engleski) | Objectives: The purpose of the paper is whether it is possible to apply a short-term high-salt (HS) diet to influence indicators of cerebrovascular reactivity in young healthy subjects, in response to selected physiological research stimuli (orthostatic test, hypercapnia induced by breath hold test, hypocapnia induced by hyperventilation and hyperoxia).
Study Design: The study was designed as a controlled intervention study in which all subjects were subjected to the same protocol, with repeated identical measurements.
Participants and methods: In the end, 27 people participated in the research (Female: 21, Male: 6, age range 19-24). Participants were on a 7-day low-salt diet (low salt LS; <2.3 g table salt/day), followed by a 7-day HS diet (>11.2 g table salt/day). After each weeks, blood and urine analyzes and anthropometric measurements were performed. Arterial blood pressure, heart rate (HR) and heart rate variability, cerebral and systemic hemodynamic parameters were recorded simultaneously with transcranial Doppler ultrasound and The Task Force® Monitor, before and after the mentioned stimuli.
Results: The subjects remained normotensive during both weeks of measurement. After orthostatic changes, mean cerebral blood flow (CBF), diastolic cerebral blood flow (DCBF) and velocity time integral (VTI) values decreased in both protocols, while cerebrovascular resistance (CVR) values increased in LS and cerebral pulsatility index (CPI) during both diets. In the systemic circulation, the cardiac output (CO) increased and the total peripheral resistance (TPR) decreased. As a result of hypercapnia, CBF, VTI, DCBF and systolic cerebral blood flow (SCBF) values were significantly increased, and CVR was reduced. A significant decrease in HF was after each measure. The increase in SV is significant in LS, and in LS and HS the drop in cardiac output (CO) and the cardiac index (CI). Hypocapnia led to a decrease in cerebral perfusion pressure (CPP), CBF, VTI, DCBF, SCBF, and an increase in CVR and CPI values, as well as an increase in SF, CO and CI, and a decrease in values of systemic pressures as well as TPR and TPRI. Hyperoxia led to lower values of cerebral pressures, increased CPI, and systemic lower HR, CO and CI. The concentration of noradrenaline and vanillylmandelic acid in urine is reduced in HS. A HS diet caused an attenuation of the sympathetic response measured by low frequency/high frequency ratio and an attenuation of the baroreceptor response compared with a LS diet during orthostatic stimulation and hyperventilation.
Conclusion: The results suggest that MPK in response to the orthostatic test was preserved in the HS diet, with altered cerebrovascular resistance and dampened BRS and sympathetic activity.
With exeption of the increase of SV in LS after BHT, in other provocation tests there was no difference in the physiological response between the NS and VS diet. However, the sympathetic response is dampened, not only in orthostasis, but also in hyperventilation in the HS diet. |