Comparison of gastric luminal and gastric wall PCO2 during hemorrhagic shock

Measurement of gastric wall PCO2 has emerged as a promising monitor of perfusion deficits during low-flow states of circulatory shock. In the present study, gastric luminal PCO2 measured with the gastric tonometer was compared with the PCO2, measured directly in the wall of the stomach during hemorrhagic shock in two groups of five Sprague-Dawley rats. One group was pretreated with the H2 blocker, ranitidine. During a 120-min interval of hemorrhage, tonometer PCO2 increased from 60 +/- 7 mmHg to 90 +/- 10 mmHg, and time-coincident gastric wall PCO2 from 52 +/- 5 mmHg to 131 +/- 14 mmHg. Following reinfusion of shed blood, tonometer PCO2 remained elevated for an interval exceeding 60 min, but gastric wall PCO2 returned to control levels within approximately 10 min. Ranitidine pretreatment did not alter the relationships between gastric wall PCO2 and tonometer PCO2. These observations indicate that gastric luminal PCO2 underestimates relatively rapid increases in gastric wall PCO2 during profound hemorrhagic shock in rats.

Comparison of parathyroid donor grafts

We compared the degrees of cell maturity, antigenicity and secretory function of parathyroid tissues (PTG) from cadavers (C-PTG), 20-28 week fetuses (F-PTG) and PTG adenomas (A-PTG). In A-PTG, scattered or clustered immature cells were observed, but there were none in F-PTG and C-PTG tissues. A-PTG and C-PTG exhibited better secretory function than did F-PTG. No clear differences were found in HLA class I (ABC) antigen quantity among the three donor PTG tissues, but the amounts of HLA class II (DR) antigen in A-PTG and F-PTG were significantly lower than that in C-PTG. The results demonstrate that C-PTG, with its functional advantages, and F-PTG, with its relatively low antigenicity, can be used in clinical transplantation, while A-PTG tissues are not suitable for clinical transplantation on account of their immaturity and the possibility of carcinomatous change.

Increased angiotensin II type-1 receptor gene expression in neuronal cultures from spontaneously hypertensive rats

In this study we compared the expression of angiotensin II type 1 (AT1) receptor messenger RNA (mRNA) and AT1 receptors in neurons cultured from Wistar-Kyoto (WKY) and spontaneously hypertensive (SH) rat brains. Neuronal cultures from the hypothalamus and brain-stem of 1-day-old SH rats exhibited approximately 4-fold higher steady-state levels of AT1 receptor mRNA than the corresponding WKY cultures. This was attributable to greater levels of both AT1A and AT1B receptor mRNA subtypes in SH rat neuronal cultures compared with WKY rat neurons. SH rat neuronal cultures also exhibited increased numbers (approximately 2.3-fold) of binding sites for [3H]DuP753, an AT1 receptor selective ligand, and enhanced (approximately 3.4-fold) stimulation of inositol phospholipid hydrolysis by angiotensin II compared with WKY neurons. By contrast, cultured astroglia from SH and WKY rat brain exhibited no significant differences in either the levels of AT1 receptor mRNA or the specific binding of [3H]DuP753. These data suggest that in SH rat neurons, AT1 receptor transcription and translation is increased, compared with neurons from WKY rats.

Angiotensin II type 2 receptor expression in neuronal cultures from spontaneously hypertensive rat brain

We have compared the levels of angiotensin II (AII) type 2 (AT2) receptors in neuronal cultures from 1-day-old Wistar Kyoto (WKY) and spontaneously hypertensive (SH) rat hypothalamus and brainstem. These studies were performed to determine if the increase in total AII receptors observed in SH neurons in previous studies includes the AT2 receptor subtype. Specific binding of the AT2 receptor selective ligand [125I]CGP42112 to WKY and SH rat neuronal cultures was time dependent and saturable in each case. Kd (approximately 0.35 nM) and Bmax (approximately 95 fmol/mg protein) values for [125I]CGP42112 specific binding did not significantly differ between WKY and SH rat cultures. In addition, AT2 receptor-mediated reductions in cellular cGMP exhibited no significant differences in WKY and SH rat neuronal cultures. We conclude that the greater levels of AII receptors found in SH rat hypothalamus/brainstem neuronal cultures, compared with WKY rat neurons from these areas, do not include the AT2 receptor subtype.

Expression of embryonic zeta-globin and epsilon-globin chains in a 10-year-old girl with congenital anemia

A 10-year-old Danish girl with congenital anemia is described. At birth, she had severe anemia and erythroblastosis and was transfused a number of times during the first year. The need for transfusions has since declined steadily. Her reticulocyte counts varied between 2% and 15%, and her bone marrow aspirate showed some dyserythropoietic features. Her hemoglobin F level was consistently elevated, up to as much as 41%. Her erythrocytes had a normal level of I antigen but an undetectable level of i antigen. Moreover, embryonic zeta-globin and epsilon-globin chains were present in some of her circulating erythrocytes. These findings may represent the manifestations of a new variant of congenital anemia.

Nude mouse interim host model for human parathyroid grafts. Part III. Mechanism of modification of allograft antigenicity

The alterations of number and DR antigen expression of antigen presenting cells (APCs) in human PTG grafts during the interim hosting period were analyzed. The results were as follows: 1) In C-PTG grafts, the APC number was reduced obviously within 100 days in the interim host. In F-PTG and A-PTG grafts, the APC number was increased at 30 d of interim hosting, and then decreased gradually. 2) No obvious change in D-related (DR) antigen expression of individual APCs was seen in C-PTG and F-PTG grafts. In A-PTG grafts, DR antigen expression was increased at 30 d of interim hosting, but then dropped gradually and asynchronously.

Osmoregulation of the magnocellular system during pregnancy and lactation

We compared the responsiveness of both the vasopressin (VP) and oxytocin (OT) magnocellular systems to osmotic stimulation during pregnancy and lactation to determine if changes in thresholds and sensitivities were similar for both neuropeptides. Virgin, pregnant (day 20), and lactating (day 6) Sprague-Dawley rats were injected with a hypertonic NaCl solution (0.25 M-8.0 M NaCl; 15 ml/kg sc) and decapitated 2 h later. Late in gestation, the apparent osmotic threshold for both VP and OT release was lower by approximately 10 mosmol/kgH2O than that of virgin and lactating animals. The sensitivity (i.e., slope of the linear regression relating plasma osmolality and VP or OT levels) of the magnocellular system to osmoregulation, however, was unchanged in pregnant animals but was significantly attenuated (P < 0.01) for both peptides during lactation (slopes of lactating vs. virgin rats: OT, 1.7 vs. 3.4; VP, 1.1 vs. 1.9). The neural lobe content of VP decreased (P < 0.05) in pregnant rats, whereas OT stores were reduced (P < 0.05) in lactating animals. Thus, during pregnancy, the lower tonicity of plasma is perceived as normal by both VP and OT neuroendocrine systems enabling excretion of an acute sodium or water load.

Nude mouse interim host model for human parathyroid grafts. Part IV. Human PTG xenograft rejection in a mouse B lymphocyte system

An interim host model for human parathyroid gland (PTG) grafts has been established. In this experiment, the proliferation of mouse blood vessels and infiltration of mouse B lymphocytes into human PTG grafts were successively observed. The results showed that within 10 d of interim hosting, when PTG grafts were still nourished by permeable factors, scattered mouse B lymphocyte infiltration was already apparent. As time went by, B lymphocyte infiltration and IgG secretion became more obvious. At 60-90 d interim hosting, an intact human-mouse tissue "chimera" was formed. Thereafter, human PTG grafts were gradually fragmented and absorbed. The theoretical significance and clinical value of this rejection phenomenon are discussed.

Myocardial hypercarbic acidosis reduces cardiac resuscitability

BACKGROUND

The severity of spontaneous myocardial hypercarbic acidosis during cardiac arrest previously has been predictive of the likelihood of restoring spontaneous circulation. The present study investigated whether hypercarbia itself impairs cardiac resuscitation. Since coronary perfusion pressure is the overriding determinant of cardiac resuscitability, we used a porcine model of cardiac arrest in which coronary perfusion pressure was controlled.

METHODS

In 31 domestic pigs anesthetized with pentobarbital, the lungs were mechanically ventilate. Myocardial carbon dioxide tension and hydrogen ion concentration were measured by sensors advanced into the myocardium. After 15 min of untreated ventricular fibrillation, venoarterial extracorporeal circulation was initiated. Animals were randomized to receive a carbon dioxide gas fraction in the extracorporeal perfusate of 0.00, 0.10, 0.30, or 0.50 with oxygen concentration maintained constant at 0.50. Extracorporeal flow was adjusted to maintain a coronary perfusion pressure in the range of 60-80 mmHg, a level of predictive resuscitability.

RESULTS

The proportion of animals successfully resuscitated and the proportion of animals maintaining spontaneous circulation for 60 min or longer decreased with increasing perfusate PCO2 and concurrent increases in myocardial CO2 tension in the absence of altered oxygen utilization (P < .01).

CONCLUSIONS

Hypercarbia, in this experimental setting, was therefore a quantitative determinant of both myocardial resuscitability and the restoration of spontaneous circulation.

Regional blood flow during closed-chest cardiac resuscitation in rats

Quantitative measurement of regional blood flow during cardiac arrest and resuscitation has been confined to large animals. We report on a rodent model utilizing radioactive microspheres during cardiac arrest and resuscitation for investigation of regional blood flow. Ventricular fibrillation was electrically induced in 10 pentobarbital-anesthetized Sprague-Dawley rats. Resuscitation was attempted by precordial compression followed by external direct current countershock. During precordial compression, cardiac output corresponded to 12% of prearrest flow. Similarly low flows were observed in the myocardium and brain. However, much lower flows were observed in the adrenal glands, kidneys, intra-abdominal viscera, skin, and skeletal muscle. Five of ten animals were successfully resuscitated. During precordial compression, resuscitated animals had significantly higher cardiac output (13.1 +/- 4.1 vs. 8.6 +/- 1.46 ml/min), myocardial blood flow (0.70 +/- 0.24 vs. 0.22 +/- 0.15 ml.min-1.g-1), cerebral blood flow (0.17 +/- 0.04 vs. 0.06 +/- 0.02 ml.min-1.g-1), and adrenal blood flow (1.09 +/- 0.60 vs. 0.27 +/- 0.16 ml.min-1.g-1). Thirty minutes after successful resuscitation, cardiac output and myocardial, cerebral, renal, and adrenal blood flows and blood flow to splanchnic viscera (with the exception of the spleen) had returned to > or = 70% of prearrest flows. These studies confirm the conclusion of earlier investigations in larger animals that visceral blood flow during cardiac arrest and precordial compression is preferentially distributed to the brain and myocardium. Successful cardiac resuscitation is contingent on threshold levels of myocardial blood flow that exceed 0.4 ml.min-1.g-1.

Angiotensin-II induction of plasminogen activator inhibitor-1 gene expression in astroglial cells of normotensive and spontaneously hypertensive rat brain

Angiotensin-II (AII) stimulates plasminogen activator inhibitor-1 (PAI-1) gene transcription, translation, and protein secretion from astroglial cells derived from normotensive [Wistar-Kyoto (WKY)] rat brain, an effect mediated by AII type 1 (AT1) receptors. Since abnormal expression of the brain AII system has been demonstrated in spontaneously hypertensive (SH) rats, we investigated the regulation of PAI-1 gene expression by AII in astroglial cells from the brains of these animals. AII caused an increase in PAI-1 gene expression in SH rat astroglia in a manner similar to that observed in WKY-derived cultures. However, both the basal and AII-stimulated levels of PAI-1 mRNA in SH rat astroglia were only 20% of those observed in WKY rat astroglial cultures. Consequently, there was a significant reduction in the de novo synthesis and secretion of PAI-1 from astroglia of SH rat brain. The reduced synthesis and secretion of PAI-1 from SH rat brain astroglia was associated with lower numbers of AT1 receptors in these cells. However, the steady state levels of AT1 receptor mRNA were comparable in both WKY and SH rat astroglia. This reduction in AII-modulated PAI-1 levels in SH rat astroglia is consistent with a proposed role of these interactions in the development of hypertension in these animals.

Extracorporeal circulation as an alternative to open-chest cardiac compression for cardiac resuscitation

Open-chest direct cardiac compression represents a more potent but highly invasive option for cardiac resuscitation when conventional techniques of closed-chest cardiac resuscitation fail after prolonged cardiac arrest. We postulated that venoarterial extracorporeal circulation might be a more effective intervention with less trauma. In the setting of human cardiac resuscitation, however, controlled studies would be limited by strategic constraints. Accordingly, the effectiveness of open-chest cardiac compression was compared with that of extracorporeal circulation after a 15-min interval of untreated ventricular fibrillation in a porcine model of cardiac arrest. Sixteen domestic pigs were randomized to resuscitation by either peripheral venoarterial extracorporeal circulation or open-chest direct cardiac compression. During resuscitation, epinephrine was continuously infused into the right atrium, and defibrillation was attempted by transthoracic countershock at 2-min intervals. Systemic blood flows averaged 198 ml.kg-1.min-1 with extracorporeal circulation. This contrasted with direct cardiac compression, in which flows averaged only 40 ml.kg-1.min-1. Coronary perfusion pressure, the major determinant of resuscitability on the basis of earlier studies, was correspondingly lower (94 vs 29 mm Hg). Extracorporeal circulation, in conjunction with transthoracic DC countershock and epinephrine, successfully reestablished spontaneous circulation in each of eight animals after 15 min of untreated ventricular fibrillation. This contrasted with the outcome after open-chest cardiac compression, in which spontaneous circulation was reestablished in only four of eight animals (p = .038). We conclude that extracorporeal circulation is a more effective alternative to direct cardiac compression for cardiac resuscitation after protracted cardiac arrest.

Cardiac anaphylaxis in the Sprague-Dawley rat

Anaphylactic shock was induced in pentobarbital-anesthetized, mechanically ventilated Sprague-Dawley rats that had been sensitized 21 days earlier to crystallized ovalbumin. The sensitization was confirmed by passive cutaneous anaphylaxis test. Antigen challenge produced an immediate reduction in mean aortic pressure from 168 to 67 mm Hg within 1 minute after intravenous injection of ovalbumin. Plasma histamine increased from 4.5 to 128 ng/ml within 5 minutes after injection of antigen. There were no changes in airway or esophageal pressures after antigen challenge. Left ventricular diastolic pressure was increased, and contractility, as measured by the rate of change of left ventricular pressure (dP/dt), was decreased over an interval exceeding 90 minutes. When isolated, constant flow--perfused hearts from sensitized Sprague-Dawley rats were challenged with antigen, decreases in left ventricular function were observed associated with decreased positive and negative maximum rate of change of left ventricular pressure (dP/dtmax). This experimental model in the rat therefore demonstrated selective myocardial impairment with reduced inotropism and lusitropism after anaphylaxis.

Post-transcriptional regulation by interferon-alpha of epsilon-globin production in human erythroleukemia K-562 cells

Treatment of human K-562 erythroleukemia cells with interferon-alpha (IFN-alpha) resulted in a six-fold increase in the production of epsilon-globin, a component of embryonic hemoglobin, but in a two-fold or less augmentation of the production of other globin species. There was no comparable increase in the production of epsilon-globin mRNA following IFN treatment. We did, however, observe a shift in the cytoplasmic location of the epsilon-globin mRNA from the messenger ribonucleoprotein (mRNP) to the polysome fraction after IFN-alpha addition. No such shift was noted in the location of the mRNA for A gamma-globin, the major globin product of K-562 cells, which was always present in the polysome fraction. These results are significant with respect to the mechanisms of cellular regulation and differentiation induced by IFNs.

Human embryonic zeta-globin chain expression in deletional alpha-thalassemias

zeta-Globin chain expression in carriers of a number of deletional alpha-thalassemias is investigated by radioimmunoassay. In a few cases, zeta-globin mRNAs are also studied. zeta-Globin chains are detected in (--SEA/), (--MED/), and (--SPAN/) deletions, but not in six other deletional mutations. These results suggest that the DNA element capable of suppressing zeta-globin expression in adult erythroid cells is present within the (--SPAN/) deletion, while the DNA fragment between the 5' breakpoints of the (--SA/) and the (--SEA/) deletions may contain sequences necessary for augmenting zeta-globin expression in adult erythroid cells. Furthermore, zeta-globin chains are shown by an immunocytologic technique to be present in all circulating erythrocytes in carriers of the (--SEA/) and (--MED/) deletions. This simple immunocytologic test is highly sensitive and specific to detect adult carriers of either the (--SEA/) or (--MED/) deletions, and can be used for the detection of couples at risk of pregnancies involving fetuses with homozygous alpha-thalassemia.

Identification of a membrane-associated 1-0-alkyl-2-arachidonoyl-sn-glycero-3-phosphocholine hydrolyzing phospholipase A2 in guinea pig 1 epidermis. Implications in the cutaneous biosynthesis of platelet-activating factor

A membrane-associated 1-0-alkyl-2-arachidonoyl-GPC hydrolyzing phospholipase A2 was identified in guinea pig epidermis. It is regio-specific (associated with the particulate microsomal fraction) and specific for the hydrolysis of 1-0-alkyl-2-arachidonoyl-sn-glycero-3-phosphocholine. It is sensitive to low calcium concentrations suggesting that it may be activated by increasing intracellular calcium. Since ether-linked phospholipids are known to exist in the epidermis, further understanding of the properties of this 1-0-alkyl-arachidonoyl-hydrolyzing PLA2 may allow us to control the generation of 1-0-alkyl-2-lyso-sn-glycero-3-phosphocholine, a key substrate for the generation of the platelet-activating factor in the tissue.

Dietary intake of concentrated gamma-linolenic acid (GLA)-enriched oil suppresses cutaneous level of dihomo-gamma-linolenic acid (DGLA): possible in vivo inhibition of microsomal elongation of GLA to DGLA

The dietary supplementation of normal guinea-pig diet with moderate levels of vegetable oils containing gamma-linolenic acid (GLA) is associated with elevation of epidermal levels of dihomo-gamma-linolenic acid (DGLA) and 15-hydroxyeicosatrienoic acid (15-lipoxygenase product of DGLA). However, supplementation of diet with higher level (70%) of GLA (GLA-70) resulted in marked decrease of epidermal level of DGLA. This nutritional observation prompted us to investigate in vitro the effects of varying concentrations of polyunsaturated fatty acids (PUFAs) on rat liver microsomal chain elongation of GLA into DGLA. Our data revealed that low concentrations of GLA (less than 100 microM) are stimulatory on the chain elongation while higher concentrations (greater than 100 microM) are inhibitory. The 18-carbon linoleic acid (precursor of GLA) was also markedly inhibitory at high concentrations. Interestingly, the longer chain 20-carbon n-3 PUFAs: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) exerted negligible effect. The results suggest that increased systemic presence of free PUFAs, such as may occur in vivo after dietary intake of high n-6 PUFA-containing vegetable oils, may explain the decreased level of DGLA in the epidermal tissue.

Atrial natriuretic peptide receptor subtypes in rat neuronal and astrocyte glial cultures

We have compared the levels and subtypes of atrial natriuretic peptide (ANP) receptors in astrocyte glial and neuronal cultures prepared from the hypothalamus and brain stem of 1-day-old rats. Astrocyte glial cultures contain approximately twice the number of ANP receptors, as measured by 125I-ANP specific binding, compared with neuronal cultures. Rat ANP-(99-126), rat brain natriuretic peptide (BNP32), C-type natriuretic peptide (CNP-22), atriopeptin I, and [des-Gln18,Ser19,Gly20,Leu21, Gly22]atrial natriuretic factor-(4-23)-NH2[C-ANF-(4-23)] all competed strongly for 125I-ANP binding in both culture types, with inhibitory constant values ranging from 0.47 to 8.07 nM. The presence of ANP-C receptors (clearance type) in both cell types is indicated from the strong competition of 125I-ANP specific binding by C-ANF-(4-23). The potency profiles for stimulation of guanosine 3',5'-cyclic monophosphate levels by these peptides were ANP = BNP much greater than CNP-22 greater than atriopeptin I in astrocyte glia and CNP-22 much greater than BNP32 greater than ANP greater than atriopeptin I in neuronal cultures. These results indicate that both types of culture contain guanylate cyclase-coupled ANP receptors, with astrocytes containing predominantly the ANP-A subtype and neurons predominantly the ANP-B subtype.

Characterization of a polyclonal anti-peptide antibody to the angiotensin II type-1 (AT1) receptor

A polyclonal antibody has been prepared against a synthetic peptide corresponding to amino acids 14-23 of the angiotensin II type-1 (AT1) receptor. The antibody is of high titer and mono-specific. Western blot analysis of membranes from rat liver, kidney, and adrenal gland showed that the antibody specifically recognizes a protein band of MW 70,000 whose amounts are highest in the liver, followed by kidney and adrenals. In addition, a relatively less prominent band of MW 95,000 was also detected. The relative distribution of this protein correlates well with the values obtained for [3H]-DuP753 binding and AT1 receptor mRNA.

Angiotensin II stimulation of plasminogen activator inhibitor-1 gene expression in astroglial cells from the brain

In this study, we investigated the mechanism of angiotensin II (Ang II) induced secretion of plasminogen activator inhibitor-1 (PAI-1) from astroglial cells prepared from 21-day-old rat brain. Competition-inhibition experiments with the use of selective antagonists for Ang II receptor subtypes indicated that astroglial cells contain chiefly Ang II type 1 (AT1) receptors. The interaction of Ang II with AT1 receptors resulted in a time- and concentration-dependent stimulation of PAI-1 gene expression. A maximal, 20-fold induction of PAI-1 messenger RNA (mRNA) steady-state levels was observed with 10 nM Ang II. This effect of Ang II was blocked by DuP753, an AT1 receptor antagonist, but not by PD123177, an AT2 receptor antagonist. Raise in PAI-1 mRNA levels was followed by an elevation in PAI-1 concentration in culture media reaching its maximum after 24 h. Interaction of Ang II with AT1 receptors also resulted in a time- and concentration-dependent stimulation of inositol phospholipid (IP) hydrolysis. A maximal, 3- to 5-fold stimulation of IP hydrolysis was observed with 10 nM Ang II. The time course experiments indicated that Ang II-induced stimulation of IP hydrolysis precedes the stimulation of PAI-1 mRNA. This suggested that activation of phospholipase C, IP hydrolysis system and possibly protein kinase C (PKC) may mediate Ang II's effect on PAI-1 mRNA. Direct stimulation of PKC by phorbol ester, phorbol 12,13-dibutyrate (PDB), resulted in a time- and concentration-dependent elevation of PAI-1 mRNA levels, similar to that caused by Ang II (maximal stimulation of 20-fold with 100 nM PDB for 4 h). This effect was totally blocked by the protein kinase C inhibitor, H7. In addition, Ang II stimulation of PAI-1 mRNA was also blocked by H7. In contrast, Ang II did not elevate PAI-1 mRNA levels in astroglial cultures from neonatal rat brains. However, treatment of neonatal cultures with PDB increased levels of this mRNA species. These observations indicate that the coupling of AT1 receptors with IP hydrolysis and PKC activation may be important for Ang II stimulation of PAI-1 gene expression. The lack of Ang II's effect on PAI-1 mRNA in neonatal astroglia may be explained either by a low coupling efficiency between AT1 receptors and the second messenger system, or by a low AT1 to AT2 receptor level ratio.

[Changes in T cell subsets and the expression of receptors of transferrin and interleukin-2 in chronic active hepatitis]

The changes of T-cell subsets and expression of transferrin receptor (TFR) and interleukin-2 receptor (IL 2 R) of peripheral blood lymphocyte from patients with chronic active hepatitis (ACH) and chronic serious hepatitis (CSH) were studied. The results showed that T3+ cells were decreased. (P less than 0.01) and T8+ cells were significantly increased (P less than 0.01) in patients with CAH and CSH. TH/TS ratio was markedly decreased in both groups of patients (P less than 0.01). The data also showed that TFR and IL 2 R were in a state of high-expression in resting T-cell, but no obvious changes could be found in the expression of receptor of PHA-stimulated T cells of patients, as compared the controls. The results suggested that some inhibitory factor may be present in the serum of CAH and CSH patients.

Pulmonary ventilation/perfusion defects induced by epinephrine during cardiopulmonary resuscitation

BACKGROUND

Epinephrine has been shown to impair pulmonary excretion of CO2 during resuscitation. This phenomenon was investigated in a rodent model of cardiac arrest and conventional resuscitation.

METHODS AND RESULTS

The effects of racemic epinephrine were compared with the selective alpha 1-agonist methoxamine and with saline placebo during cardiac resuscitation in 15 Sprague-Dawley rats mechanically ventilated with gas containing 70% oxygen. Epinephrine and methoxamine but not saline placebo significantly increased coronary perfusion pressure from approximately 32 to 55 mm Hg. Following epinephrine, end-tidal PCO2 decreased from approximately 10 to 5 mm Hg. This was associated with a time-coincident decrease in PaO2 from approximately 130 to 74 mm Hg and an increase in PaCO2 from approximately 26 to 40 mm Hg. These changes indicated increases in alveolar dead space ventilation concomitant with increases in pulmonary arteriovenous admixture. No such effects were observed after administration of either methoxamine or saline placebo. Each of the 15 rats was successfully resuscitated. However, a significantly larger number of transthoracic countershocks were required after epinephrine compared with methoxamine or placebo before return of spontaneous circulation.

CONCLUSIONS

Epinephrine induced ventilation/perfusion during cardiopulmonary resuscitation as a result of redistribution of pulmonary blood flow.

[Rational management of cardiac arrest]

When immediate defibrillation fails, successful cardiac resuscitation is contingent on prompt reestablishment of myocardial blood flow. Conventional methods of closed-chest resuscitation generates only critical levels of myocardial blood flow and therefore are of limited value for successful resuscitation. Methods that optimize the site, depth, rate and duration of precordial compression may increase myocardial blood flow, however, the lack of objective measurements of their hemodynamic effects limits the optimal performance of this resuscitation method. With the recognition that elimination of CO2 is flow limited, measurement of end-expired PCO2 has emerged as a practical option for continuous assessment of systemic blood flow and coronary perfusion pressure. With measurement of the end-expired PCO2, operator fatigue may be recognized, the technique of precordial compression may be optimized, and the likelihood of restoring spontaneous circulation may be estimated. When conventional cardiac resuscitation fails or is predicted to fail by measurements of end-tidal PCO2, more effective interventions such as open-chest direct cardiac massage may be instituted. Regarding the vast resuscitation polypharmacy, only agents that act by selectively augmenting coronary perfusion pressure and myocardial blood flow are of proven benefit for successful resuscitation.