Myocardial damage following cardiac surgery: comparison between single-dose Celsior cardioplegic solution and cold blood multi-dose cardioplegia.

Myocardial protection during cardiac surgery can be accomplished by different cardioplegic solutions. The aim of this study was to assess myocardial damage after heart valve surgery performed with myocardial protection of a single dose of Celsior cardioplegia or with repeated cold blood cardioplegia. After the stratification of 139 valvular patients by means of matching according to cross-clamp and cardiopulmonary bypass time, 32 patients were retained for comparison (16 patients received Celsior and 16 patients received cold blood cardioplegia). Creatine kinase-MB (CK-MB) and cardiac troponin I (cTnI) release were evaluated until six days after the operation. Pre-operative characteristics were similar in both groups. In the Celsior group, CK-MB and cTnI values were significantly higher from the first up to the sixth post-operative day. Peak cTnI values were 19.4 ± 13.4 and 9.7 ± 7 ng/mL (p=0.01) in the Celsior and the Cold Blood group, respectively. Peak CK-MB values were 79.6 ± 58.8 and 45.9 ± 20.6 U/L (p=0.07) in the Celsior and the Cold Blood group, respectively. Cold blood cardioplegia reduces perioperative myocardial damage compared to the Celsior solution in elective cardiac valve operations.

Pump blood processing, salvage and re-transfusion improves hemoglobin levels after coronary artery bypass grafting, but affects coagulative and fibrinolytic systems.

Cell saving systems are commonly used during cardiac operations to improve hemoglobin levels and to reduce blood product requirements. We analyzed the effects of residual pump blood salvage through a cell saver on coagulation and fibrinolysis activation and on postoperative hemoglobin levels. Thirty-four elective coronary artery bypass graft (CABG) patients were randomized. In 17 patients, residual cardiopulmonary bypass (CPB) circuit blood was transfused after the cell saving procedure (cell salvage group). In the other 17 patients, residual CPB circuit blood was discarded (control group). Activation of the coagulative, fibrinolytic and inflammatory systems was evaluated pre-operatively (Pre), 2 hours after the termination of CPB (T0) and 24 hours postoperatively (T1), measuring prothrombin fragment 1.2 (PF 1.2), plasmin-anti-plasmin (PAP), plasminogen activator inhibitor-1 (PAI-1) and interleukin-6 (IL-6). The cell salvage group of patients had a significant improvement in hemoglobin levels after processed blood infusion (2.7 ± 1.7 g/dL vs 1.2 ± 1.1 g/dL; p=0.003). PF1.2 levels were significantly higher after infusion (T0: 1175 ± 770 pmol/L vs 730 ± 237 pmol/L; p=0.037; T1: 331 ± 235 pmol/L vs 174 ± 134 pmol/L; p=0.026). Also, PAP levels were higher in the cell salvage group, although not significantly (T0: 253 ± 251 ng/mL vs 168 ± 96 ng/mL; p: NS; T1: 95 ± 60 ng/mL vs 53 ± 32 ng/mL; p: NS). No differences were found for PAI-1, IL-6, heparin levels or for red blood cell (RBC) transfusions. The cell salvage group of patients had increased chest tube drainage (749 ± 320 vs 592 ± 264; p: NS) and fresh frozen plasma transfusion rate (5 (29%) pts vs 0 pts; p<0.04). Pump blood salvage with a cell saving system improved postoperative hemoglobin levels, but induced a strong thrombin generation, fibrinolysis activation and lower fibrinolysis inhibition. These conditions could generate a consumption coagulopathy.

Myocardial protection during aortic surgery: comparison between Bretschneider-HTK and cold blood cardioplegia.

The ideal cardioplegic strategy in thoracic aorta operations requiring long cardiopulmonary bypass and cross-clamp time has not been established. Suboptimal myocardial protection may lead to myocardial damage and possible post-operative complications. We evaluate post-operative cardiac Troponin I (cTnI) release, low cardiac output syndrome (LCOS) and mortality, using a cold crystalloid single-dose intracellular or cold blood multidose cardioplegia in 112 elective or emergent thoracic aorta operation patients. Fifty-four patients (HTK group) received Custodiol® cardioplegic solution and 58 received cold blood cardioplegia (CB group). Cross-clamp time, cardiopulmonary bypass (CPB) time and cTnI peak release were similar in both groups. No differences were found for atrial and ventricular arrhythmias, inotropic support, LCOS and in-hospital mortality. Two-way ANOVA analysis revealed an interactive effect on cTnI peak (p=0.012) of cardioplegic solution type across the cross-clamp time quintile. In the fifth quintile, cross-clamp time patient (>160 min) cTnI peak value was higher in CB patients (p=0.044). HTK and CB cardioplegic solutions assure similar myocardial protection in patients undergoing thoracic aorta operations. In long cross-clamp times, the lower post-operative cTnI release detected using HTK may be indicative of a better myocardial protection in these extreme conditions.

Amiloride and calcium effect on the outer barrier of the frog skin.

Amiloride (0.1 mM) as well as Ca++ (10 mM) inhibit Na+ transport across frog skin by blocking Na+ entrance across the outer barrier of the epithelium. The inhibition produced by amiloride consists of an "early" and a "late" phase which together account for almost a total inhibition of the short-circuit current (SCC). The analysis of the time course indicates that the two phases are due to the inhibition of superficially and deeply located Na sites, respectively, Ca++, instead, only blocks a fraction of the SCC, and this fraction seems to correspond to the inhibition of the same population of Na sites blocked by the "late" phase of amiloride effect. The location of the two populations of Na sites as well as the possible relationship between them are discussed in terms of maturation of the outermost cell layer.

Studies on chloride permeability of the skin of Leptodactylus ocellatus: I. Na+ and Cl- effect on passive movements of Cl-.

The outflux of chloride through the isolated skin (JCl31) of the South American frog Leptodactylus ocellatus (L.) is carried by a mechanism that saturates at high concentration of chloride on the inside, and is stimulated by the presence of Cl- in the outer solution (trans side). The presence of Na+ on the outside, by itself, does not increase JCl31. However, when JCl31 is already increased by chloride on the trans side, the addition of Na+ produces a significant further increase. At low concentration of Cl- on the outside JCl31 is carried by an exchange diffusion mechanism. At high concentrations of Cl- outside, JCl31 proceeds through a route which involves changes in electrical parameters. The results suggest that both mechanisms are located on the cell membranes and, therefore, that the fluxes would cross through the cytoplasm of the cells. Na+ stimulates the second mechanism only.

Studies on chloride permeability of the skin of Leptodactylus ocellatus: III. Na+ and Cl- effect on electrical phenomena.

During their flux through the skin of the frog Leptodactylus ocellatus, Na+ and Cl- interact with each other. This interaction gives rise to electrical phenomena which are studied in the present paper. The skin is mounted in Na2SO4 Ringer's with 115 mM Na+ on the inside, and a variety of outer solutions. The osmolarity of all solutions is kept constant at 237.8 mosmol by adding sucrose. When the main anion used on the outside is SO=4 the electrical potential difference (deltapsi) rises steadily with the concentration of sodium (Na+)0 up to 87 mV, which is reached at about 20 mM. Thereafter deltapsi remains constant. When the main anion is Cl- it is observed that deltapsi rises steadily with (NaCl)0 with a slope similar to the curve obtained with SO=4 (37 mV per decade), but with a lower intercept attributed to an inward Cl pumping which is characteristic of this frog species. At 2--9 mM (NaCl)0 a Cl-specific channel is activated. Further increases of (NaCl)0 produce a decrease of deltapsi. The specificity of the activation of this site by monovalent cations and its use by monovalent anions is also studied.

Studies on chloride permeability of the skin of Leptodactylus ocellatus: II. Na+ and Cl- effect of inward movements of Cl-.

At low concentration (1 mM) of Cl- in the outer solution, the influx of chloride through the isolated skin (JCl13) of the South American frog Leptodactylus ocellatus (L.) seems to be carried by two mechanisms: (i) a passive one that exhibits the characteristics of an exchange diffusion process, and (ii) an active penetration. Studies of the influx and efflux of chloride (JCl13 and JCl31) indicate that the presence of a high (107 mM) concentration of Cl- in the outer solution activates the translocation of this ion through the cells. Studies of the unidirectional flux of Cl- across the outer barrier (JCl12) indicate that Na+ out stimulates the penetration of Cl- at this level. Cl- out, in turn, stimulates the JNa12, but this effect is only detected at low concentrations of Na+ out.

Polarized monolayers formed by epithelial cells on a permeable and translucent support.

An epithelial cell line (MDCK) was used to prepare monolayers which, in vitro, develop properties of transporting epithelia. Monolayers were formed by plating cells at high densities (10(6) cells/cm2) on collagen-coated nylon cloth disks to saturate the area available for attachment, thus avoiding the need for cell division. An electrical resistance developed within 4-6 h after plating and achieved a steady-state value of 104 +/- 1.8 omega-cm2 after 24 h. Mature monolayers were morphologically and functionally polarized. They contained junctional complexes composed of desmosomes and tight junctions with properties similar to those of "leaky" epithelia. Monolayers were capable of maintaining a spontaneous electrical potential sensitive to amiloride, produced a net water flux from the apical to basal side, and discriminated between Na+ and Cl- ions. The MDCK permeability barrier behaves as a "thin" membrane with negatively charged sites. It has: (a) a linear conductance/concentration relationship; (b) an asymmetric instantaneous current/voltage relationship; (c) a reduced ability to discriminate between Na+ and Cl- caused by lowering the pH; and (d) a characteristic pattern of ionic selectivity which suggests that the negatively charged sites are highly hydrates and of medium field strength. Measurements of Na+ permeability of electrical and tracer methods ruled out exchange diffusion as a mechanism for ion permeation and the lack of current saturation in the I/deltapsi curves does not support the involvement of carriers. The discrimination between Na+ and Cl- was severely but reversibly decreased at low pH, suggesting that Na+-specific channels which exclude Cl- contain acidic groups dissociated at neutral pH. Bound Ca++ ions are involved in maintaining the integrity of the junctions in MDCK monolayers as was shown by a reversible drop of resistance and opening of the junctions in Ca++-free medium containing EGTA. Several other epithelial cell lines are capable of developing a significant resistance under the conditions used to obtain MDCK monolayers.

The sodium-transporting compartment of the epithelium of frog skin.

1. The abdominal frog skin was mounted between two chambers containing Ringer with 1 mM-Na on the outside and 115 mM-Na on the inside. When the Na concentration of the outer solution ([Na](o)) is instantaneously raised from 1 to 50 mM, the short circuit current (I) increases to a new value in less than a second, and becomes essentially time-independent. Only in a few experiments was it observed to increase further, although at a much slower rate.2. At a time t after this increase, the addition of 10(-4)M amiloride to the outer solution produces an exponential decrease of I. The area under this exponential curve is generally taken to reflect the existence of a Na- transporting compartment (NaTC).3. The amount of Na represented by NaTC is a function of t: it increases from 1.7 x 10(-9) mole. cm(-2), at t = 10 sec, to 22.8 x 10(-9) mole. cm(-2) at t = 10 min.4. In view of the fact that (a) I is not a function of the size of the ;NaTC' and (b) that whereas I reaches a steady value in a fraction of a second the size of NaTC keeps increasing for minutes, it is proposed that the ;NaTC' represents an amount of Na which is not located along the main route of transepithelial transport.5. On the assumption that the NaTC is located in a cellular compartment and that, in order to accumulate in this compartment Na should be accompanied by a permeable anion, a series of experiments were performed with Ringer in which Cl(-) was replaced by gluconate. It was observed as expected, that NaTC in gluconate is 164 times smaller than in Cl(-), but I only decreases to one half its value in Cl(-) Ringer.

The effect of antidiuretic hormone on Na movement across frog skin.

1. The effect of antidiuretic hormone (ADH) on the movement and distribution of Na was studied. This was done using three different approaches: (a) the measurement of Na and (22)Na in slices of epithelium of skins which were exposed to Ringer of varied composition containing (22)Na, (b) the measurement of the influx of Na from the outer to the inner bathing solution with (22)Na added to the outside, and (c) the use of a recently introduced technique which permits the direct evaluation of the flux from the outer solution --> epithelium, (J(OT)), i.e. the flux across the barrier which is generally regarded as the site of ADH activity.2. ADH increased the influx from the outer to the inner bathing solution of Na (50%) not only when the concentration of Na on the outside was 115 mM (i.e. higher than in the epithelium) but even when the concentration was 1 mM (67%).3. When the skin was bathed with 1mM-Na Ringer on the outside, ADH increased the unidirectional Na flux J(OT) by 56% (Rana pipiens) and 71% (Leptodactylus ocellatus). When the concentration was 115 mM a small increase (17%) was observed in paired skins of R. pipiens. Under this condition no change was observed in L. ocellatus.4. The amount of epithelial sodium which is labelled by (22)Na added to the outside was taken to reflect the amount of Na involved in Na transport across the epithelium. Depending on whether the concentration of Na on the outside was high (115 mM) or low (1 mM), ADH produced an increase, or a decrease, of both the total Na content and the amount of (22)Na exchanged.5. When the concentration of Na on the outside was low, ADH increased the total influx and J(OT) in spite of the fact that it lowers the total Na content and does not affect the exchangeable pool of Na. This observation is inconsistent with the view that the effect of ADH is due to the fact that the increased permeability of the outer barrier allows more Na into the cell, and that the resulting increase of Na concentration in the cytoplasm accelerates the Na pumps at the inner side of the cells.6. It is concluded that ADH speeds up Na movements at the outward facing barrier, and that this exchange which facilitates the penetration of Na into a transporting compartment produces also a gain or a loss of Na in compartments not directly involved in Na transport across the epithelium. One compartment which is not involved in Na transport might be the cytoplasm of the epithelial cells.

The penetration of sodium into the epithelium of the frog skin.

The aim of this paper is twofold. First, to describe a method for the measurement of the unidirectional flux of Na from the outer bathing solution into epithelium (J(OT)), and second, to describe the use of this method under a variety of experimental conditions in order to obtain some insight into the nature of this flux. The method developed is based on the exposure of a frog skin to a Ringer solution containing (22)Na. The exposure is made so that neighboring points along the surface remain in contact with the (22)Na solution for gradually longer periods, ranging from 0 to 46 sec. Some 8 to 10 samples of the exposed part are used to obtain the time course of the uptake of (22)Na and this time course is used, in turn, to evaluate J(OT). This flux is then studied in skins mounted between two identical Ringer solutions with 115 mM Na (11.25 +/- 0.10 [18] micromole.hr(-2) cm(-2)), and in skins mounted with Ringer with 1 mM Na on the outside and 115 mM Na on the inside (0.43 +/- 0.05 [18] micromole.hr(-1).cm(-2). From the observations that the flux is much larger than the net Na flux across the whole skin, that it is inhibited by K(+), and is unaffected by ouabain, it is concluded that the penetration of Na(+) into the epithelium does not occur by simple diffusion and is not directly dependent on an ouabain-sensitive mechanism. In the course of these experiments it was observed that when the skin was crushed between two chambers the uptake of Na in the neighboring exposed areas was decreased.