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Effect of Positive End-Expiratory Pressure on the Concentration of Sodium and Potassium in Plasma and Urine, Plasma Creatinine and Urine Output in Mechanically Ventilated Patients
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Bong Jae Lee, Kyu Suk Suh, Dong Ok Kim, Dong Soo Kim
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Korean J Crit Care Med. 1999;14(2):154-160.
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 Abstract
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- BACKGOUND: It has been suggested that the addition of positive end-expiratory pressure (PEEP) to the patients with ventilator support leads to an impairment on renal hemodynamics and water- and sodium-retaining hormonal systems, such as plasma renin activity (PRA), plasma aldosterone, urinary antidiuretic hormone (ADH).
METHODS
To evaluate the effects of 5 cmH2O and 10 cmH2O PEEP on renal function, we measured the plasma concentration of sodium (Na+), potassium (K+) and creatinine, urinary excretion of Na+, K+ and urine output in eight normovolemic male patients requiring ventilator support. Also changes in mean arterial pressure, pulse rate, arterial oxygen tension (PaO2) and carbon dioxide tension (PaCO2) during the experimental period were measured in these patients.
RESULTS
Both 5 and 10 cmH2O PEEP showed no significant effect on the mean arterial pressure, heart rate, PaO2, and PaCO2. Both 5 and 10 cmH2O PEEP showed no significant effect on the plasma concentration of sodium, potassium and creatinine. 5 cmH2O PEEP showed no significant effect on the urinary excretion of sodium, potassium and urine output, but 10 cmH2O PEEP showed significant effect on the urinary excretion of sodium (19% decrease, p<0.05), and urine output (12.5% decrease, p<0.05) respectively.
CONCLUSIONS
10 cmH2O PEEP was revealed to decrease urinary sodium excretion along with urinary output and this phenomenon was likely to relate with water- and sodium-retaining hormonal systems. These results suggested that it was preferable to apply high PEEP cautiously in patients with impaired renal function.
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Effects of Blood-Brain Barrier Disruption on Cerebral Oxygen Balance
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Doo Ik Lee, Young Kyu Choi, Dong Ok Kim, Keon Sik Kim, Ok Young Shin, Moo Il Kwon
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Korean J Crit Care Med. 1999;14(2):126-130.
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Abstract
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- BACKGOUND: Disruption of the blood-brain barrier (BBB) can alter the internal milieu and may increase the release of excitatory amino acid neurotransmitters or catecholamines, which may affect metabolic rate or coupling. This study was performed to evaluate whether disruption of BBB by unilateral intracarotid injection of hyperosmolar mannitol would alter oxygen supply/consumption balance in the ipsilateral cortex.
METHODS
Rats were anesthetized with 1.4% isoflurane using mechanical ventilation via tracheostomy. 25% mannitol was administered at a rate of 0.25 mlxkg-1s-1 for 30 s through unilateral internal carotid artery. The BBB transfer coefficient (Ki) of 14C-alpha-aminoisobutyric acid was measured in one group (N=7) after administering mannitol.
Regional cerebral blood flow (rCBF), regional arterial and venous O2 saturation and O2 consumption were measured in another group using a 14C-iodoantipyrine and microspectrophotometry (N=7).
RESULTS
Vital signs were similar before and after administering mannitol. Ki was significantly higher in the ipsilateral cortex (IC) than in the contralateral cortex (CC), (22.3+/-8.4 vs 4.4+/-1.1 microliterxg-1min-1). rCBF was similar between IC (105+/-21 mlxg-1min-1) and the CC (93+/-20). Venous O2 saturation was lower in the IC (43+/-7%) than in the CC (55+/-4). O2 consumption was higher in the IC (9.6+/-3.0 mlx100 g-1min-1) than in the CC (6.7+/-1.5).
CONCLUSIONS
Our data suggested that increasing permeability of the BBB increased cerebral O2 consumption and deteriorated cerebral oxygen balance.
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