PubMed · 14347262
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M M ROGER. 1965. CIRCULATORY CHANGES IN DEHYDRATION.. https://pubmed.ncbi.nlm.nih.gov/14347262/
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BACKGROUND: Previous studies have reported impaired blood flow in the ophthalmic artery (OA) and central retinal artery (CRA) in exfoliation syndrome and exfoliation glaucoma. This study evaluates blood flow at the long and short posterior ciliary arteries (LPCA and SPCA, respectively) in these conditions. METHODS: Consecutively examined candidates for cataract surgery were included. Only one eye (OD) was included in the analyses for consistency. Patients were classified into non-glaucoma and non-exfoliation (controls), primary open angle glaucoma (POAG), exfoliation syndrome and exfoliation glaucoma groups, based on the findings of the OD. Sixty-eight patients (41 males, 60.3%) were included. Color Doppler imaging (CDI) of the nasal and temporal branches of LPCA and SPCA was performed using a 7.5 Mhz probe. The peak systolic velocity (PSV), end diastolic velocity (EDV) and resistivity index (RI) were recorded for the examined vessels. RESULTS: EDV at the LPCA was significantly lower in exfoliation syndrome and glaucoma, compared with controls and POAG respectively. EDV was significantly lower and RI was significantly higher at the SPCA in exfoliation glaucoma, compared with exfoliation, whereas respective differences were statistically not significant between controls and POAG. CONCLUSIONS: The hemodynamic impairment at the LPCA in exfoliation syndrome and glaucoma supports an association between exfoliation and ischemic stress at the anterior ocular segment.
There are no clinical outcome data on which to base recommendations on how to assess and support the preterm circulation. Current standards are derived from an assumed proportionality between systemic and organ blood flow and mean blood pressure. Our study of central measures of systemic blood flow suggests preterm haemodynamics are more complex than this. Low systemic blood flow is common in the first 24 h after birth in very preterm babies and is not necessarily reflected by low blood pressure. The causes of this low systemic blood flow are complex but may relate to maladaptation to high extrauterine systemic (and sometimes pulmonary) vascular resistance. After day 1, hypotensive babies are more likely to have normal or high SBF reflecting vasodilatation. Empirically, inotropes that reduce afterload (such as dobutamine) may be more appropriate in the transitional period, while those with more vasoconstrictor actions (such as dopamine) may be more appropriate later on. Defining the haemodynamic in an individual baby needs both blood pressure and echocardiographic measures of systemic blood flow. Research in this area needs to move beyond just demonstrating changes in physiological variables to showing improvements in important clinical outcomes.
An intrathoracic pressure regulator (ITPR) is a device that can be added to the external end of a tracheal tube to create controlled negative airway pressure between positive pressure ventilations. The resulting downward bias of the airway pressure baseline promotes increased venous return and enhanced circulation during CPR and also during hypovolemic shock. In the present study, we exercised a mathematical model of the human cardiopulmonary system, including airways, lungs, a four chambered heart, great vessels, peripheral vascular beds, and the biomechanics of chest compression and recoil, to determine the relationship between systemic perfusion pressure during CPR and the value of baseline negative airway pressure in an ITPR. Perfusion pressure increases approximately 50% as baseline airway pressure falls from zero to -10 cm H2O. Thereafter perfusion pressure plateaus. Negative bias pressures exceeding -10 cm H2O are not needed in ITPR-CPR.