Innervation of the human cardiac conduction system. A quantitative immunohistochemical and histochemical study

BACKGROUND

Cardiac conduction is influenced by peptidergic mechanisms as well as classic neurotransmitters. The distribution of peptide-containing nerves has not been well defined.

METHODS AND RESULTS

Immunofluorescence and histochemical techniques were used to visualize the innervation of the human conduction system and to distinguish nerve subpopulations according to their peptide and enzyme content. Nerve fibers and fascicles displaying immunoreactivity for protein gene product 9.5 (PGP 9.5) were more numerous in the sinus and atrioventricular nodes than in the penetrating bundle, bundle branches, and adjacent myocardium. The relative density of innervation was greater in the central region of the sinus node than in the peripheral regions. Nerve densities were also higher in the transitional region of the atrioventricular node compared with its compact region. Acetylcholinesterase (AChE)-positive nerves were the main subtype identified in the sinus and atrioventricular nodes, representing half to two thirds of the stained area occupied by PGP 9.5-immunoreactive nerves. Neuropeptide Y-immunoreactive nerves represented the main peptide-containing subpopulation and occurred throughout the conduction system, displaying a similar pattern of distribution and relative density to those demonstrating tyrosine hydroxylase immunoreactivity. Nerve fibers showing immunoreactivity for vasoactive intestinal polypeptide, somatostatin, substance P, or calcitonin gene-related peptide exhibited distinct patterns of distribution and comprised a relatively minor component of the innervation, the percentage of stained area being 10- to 40-fold lower than that occupied by neuropeptide Y- and PGP 9.5-immunoreactive nerves, respectively.

CONCLUSIONS

The innervation of human conduction tissues exhibits significant regional variation and comprises putative parasympathetic nerves and intrinsic neurons (AChE positive), sympathetic efferent nerves (neuropeptide Y- and tyrosine hydroxylase-immunoreactive nerves), and other peptide-containing nerves, some of which (substance P and calcitonin gene-related peptide containing) are considered to represent afferent nerves. Locally released peptides may be involved in the neural modulation of the human conduction system.

Comparison of monoclonal antibodies AUA1 and BER EP4 with anti-CEA for detecting carcinoma cells in serous effusions and distinguishing them from mesothelial cells

Commercially available monoclonal antibodies AUA1, BER EP4 and carcinoembryonic antigen (CEA) were applied to cell blocks from 95 serous effusions. AUA1 and BER EP4 were reactive with 89% of effusions known to contain carcinoma cells, and anti-CEA with 71%. They also reacted with cells in two effusions from patients with malignant disease which were regarded as negative on conventional cytological examination of Papanicolaou-stained smears. They were negative in all but one of the benign effusions. Using all three antibodies, 95% of effusions containing carcinoma cells were detected. Use of these antibodies could improve the cytological diagnosis of serous effusions.

A comparison of two systems for assessing cerebral venous oxyhaemoglobin saturation during cardiopulmonary bypass in humans

The Somanetics Invos 3,100 cerebral oximeter is a new noninvasive device which measures the regional oxygen saturation of haemoglobin within the cerebral microvasculature by infrared spectroscopy. It was used in nine patients undergoing elective cardiac surgery and its results were compared with measurements of jugular venous bulb saturations obtained by the Oximetrix Opticath oximetry system. The index value of jugular venous bulb saturation was obtained by analysis of jugular bulb blood in an Il282 cooximeter. The cerebral oximeter was less accurate and precise (standard deviation of difference 14.1%) than the Oximetrix system (standard deviation of the difference 2.65%) and also demonstrated a systematic error in bias unrelated to cerebral perfusion pressure. The cerebral oximeter may therefore be less useful than jugular venous bulb saturation in the clinical management of patients undergoing cardiopulmonary bypass.

Aprotinin therapy in cardiac operations: a report on use in 41 cardiac centers in the United Kingdom

Aprotinin, a serine protease inhibitor, has recently been shown to reduce blood loss in cardiac surgical patients. Data on the safety and efficacy of aprotinin therapy administered to 671 cardiac surgical patients in 41 United Kingdom cardiac surgical units have been submitted to interim analysis. The patients studied were in high-risk categories for excessive bleeding, including 457 redo operations and 79 patients with active infective endocarditis. Overall mortality was 12% in redo cases and 5.1% in first-time operations. Adverse events were reported in only 20 patients (3%). Median blood loss at 24 hours after operation was 400 mL, and median transfusion volume throughout the operative and postoperative period was 2 units. These data confirm that the use of aprotinin therapy in high-risk cardiac surgical patients is associated with a low incidence of adverse events.

Aprotinin therapy in heart and heart-lung transplantation

Patients who undergo cardiothoracic transplantation represent a considerable challenge to any blood conservation program. It is well recognized that excessive bleeding increases the mortality and morbidity rates of any surgical procedure, but patients who undergo heart and lung transplantation, either singly or in combination, have a greater probability of bleeding more frequently and to a greater extent than patients who undergo many other types of surgery. In addition to the problems inherent in excessive bleeding are those associated with the need for increased donor blood transfusion requirements in these procedures. In this regard it is imperative to avoid the transmission of any blood-borne infection to a patient who is immunosuppressed. In particular, the cytomegalovirus is a key problem. With large blood losses and in patients with uncommon blood groups, it may not be possible to guarantee unlimited supplies of cytomegalovirus-negative blood.

Fine needle aspiration biopsy of lymph nodes and subcutaneous masses

The results of fine needle aspiration biopsy of lymph nodes and subcutaneous masses in 169 patients and the technique used are discussed. Of the 169 cases 76 were classified as cytologically malignant, 52 as benign/inflammatory and 49 as inadequate. Neck masses were most commonly sampled. The overall diagnostic accuracy achieved was 75%. No false positive and 2 false negative cases were seen. The advantages and limitations of the procedure are discussed as well as some of the possible sources of error.

Aprotinin inhibits platelet adhesion to endothelial cells

Studies were conducted to assess the effect of the serine protease inhibitor aprotinin on platelet adherence to both thrombin-stimulated and unstimulated human umbilical vein endothelial cells. Aprotinin treatment reduced significantly the adherence of platelets to endothelium pretreated or not with thrombin. In addition, aprotinin similarly reduced the adherence of platelets to plastic or collagen-coated tissue culture wells suggesting that the main site of action of the drug in this system is on the platelets. The role of endothelium-derived relaxing factor (EDRF; nitric oxide) in these platelet-endothelium reactions was investigated by prior incubation of both platelets and endothelial cells with NG-monomethyl-L-arginine (L-NMMA) which prevents the production of nitric oxide. The results demonstrated that nitric oxide was a significant inhibitor of the thrombin-induced platelet adherence in this assay system. Treatment with aprotinin in the presence or absence of L-NMMA reduced adherence of platelets to equivalent levels suggesting that aprotinin acts directly on the platelets via a mechanism that is EDRF-independent, to inhibit adherence.

Aprotinin does not inhibit the release of PGI2 or vWF from cultured human endothelial cells

The release of prostacyclin (PGI2) and von Willebrand factor (vWF) from human umbilical vein endothelial cells (HUVEC) was examined to determine if aprotinin had any effects on these endothelial cell reactions. These end-points were chosen to indicate if this serine protease inhibitor caused alterations in the control of haemostatic function by endothelium, in the light of the improvement in haemostasis seen in patients given aprotinin therapy at the time of open heart surgery. Stimuli used to promote secretion of prostacyclin and vWF were human alpha-thrombin, histamine, protamine sulphate, poly-L-lysine and phorbol myristate acetate. Aprotinin (30 microMs) had no significant effect on the basal or stimulated release of PGI2 or vWF from HUVEC.

Suture technique affects perianastomotic colonic crypt cell production and tumour formation

Suture line recurrence is an important cause of failure after potentially curative resection for colonic carcinoma. Our aim was to determine whether suture technique affected the incidence of perianastomotic tumours in experimentally induced colonic cancer. Sprague-Dawley rats were randomized into three groups. A 1 cm longitudinal colotomy was repaired with four interrupted 6/0 polypropylene monofilament sutures, using either a transmural technique (n = 18) or a seromuscular technique (n = 18). Control animals (n = 18) had a sham laparotomy. All animals received nine, weekly, subcutaneous injections of azoxymethane (total dose 90 mg/kg) starting 6 weeks after laparotomy. Surviving animals were killed 32 weeks after laparotomy. Five animals from each group were given intraperitoneal bromodeoxyuridine (100 mg/kg) 1 h before being killed. At death, perianastomotic tumours occurred more frequently in animals with transmural sutures than in either controls or those with seromuscular sutures. This difference was associated with a greater mucosal bromodeoxyuridine crypt cell labelling index in the transmural suture group. We conclude that a transmural anastomotic suture technique promotes the development of experimental perianastomotic colonic tumours.

Propofol for long-term sedation in the intensive care unit. A comparison with papaveretum and midazolam

Thirty-seven patients with a wide range of illnesses were studied during mechanical ventilation of the lungs in an intensive care unit. Fifteen were sedated with a continuous propofol infusion, with analgesia provided by bolus doses of papaveretum. Twelve received a continuous infusion of papaveretum, supplemented by bolus doses of midazolam. The level of sedation was assessed every four hours and measurements were made of haemodynamic and respiratory variables. Levels of sedation were generally satisfactory in both groups. Six patients who received propofol required the use of muscle relaxants, because of their strong respiratory drives, to achieve synchronisation with the ventilator. There was no significant difference in respiratory or haemodynamic variables between the groups, but several patients required inotropic support because of their disease. There was no evidence of inhibition of adrenal steroidogenesis in the propofol group. Propofol can be a useful sedative agent in the intensive care unit, but sedative regimens should be tailored to individual patient requirements.

The serine antiprotease aprotinin (Trasylol): a novel approach to reducing postoperative bleeding

Aprotinin is a polypeptide from bovine lung which has been known since 1930, and which has previously been administered to humans as a relatively non-specific protease inhibitor in a number of disease states. In 1987, a remarkable use for this drug was realized, when by chance, it was discovered that by infusing large doses of aprotinin during cardiac surgery, it was possible to greatly reduce the bleeding which had hitherto been regarded as normal in such operations. The aim of this article is to briefly review the biochemistry and pharmacology of aprotinin, and to describe the background to its use in preventing postoperative bleeding. The use of aprotinin in reducing bleeding after cardiac surgery is then described in detail, and outlined for other types of major surgery. The possible modes of action of aprotinin in reducing bleeding are discussed, with particular reference to the bleeding which follows cardiac surgery. The profound effect of aprotinin, given in a novel dosage to reverse the postoperative haemostatic defect suggests that this drug may abolish the need for blood transfusions in most patients after major surgery. In addition, it is clear that aprotinin will provide a potent tool to probe some of the remaining mysteries of the haemostatic process.

Major surgery in von Willebrand's disease

Two patients with von Willebrand's disease underwent major surgery, the first had aortic valve replacement and the second a total hip replacement. Clinically, the best practical test for monitoring the dose of cryoprecipitate necessary to maintain haemostasis was the bleeding time. The response to coagulation factor replacement in von Willebrand's disease is extremely variable, and it is necessary to maintain close coagulation monitoring until the patient's surgical condition is satisfactory for discharge from hospital.

Reduction in blood loss and blood use after cardiopulmonary bypass with high dose aprotinin (Trasylol)

The effect of high dose aprotinin (Trasylol) was evaluated in three groups of patients undergoing cardiopulmonary bypass. In a prospective, placebo-controlled, double-blind study, 80 patients having primary aorta-coronary bypass grafting received aprotinin (700 mg approximately) or saline placebo from the beginning of the procedure until skin closure. Standardized anesthetic, perfusion, and surgical techniques were used. The total loss from the thoracic drains was significantly reduced in the aprotinin group as compared with the loss in the placebo group (309 +/- 133 ml versus 573 +/- 166 ml, p less than 0.01; mean +/- standard deviation). There was a threefold difference in the total hemoglobin loss into the chest drains (aprotinin 12.0 +/- 12.6 gm versus placebo 37.7 +/- 18.3 gm). Patients of the aprotinin group received remarkably less bank blood postoperatively: 13 units total compared with 75 units. Of the 40 patients in the aprotinin group, 32 received no bank blood compared with 2 of 37 patients in the placebo group. Venous hemoglobin levels preoperatively, on day 1, and on day 7 postoperatively did not differ between the groups. At day 7 the values were 13.1 +/- 1.4 gm/dl versus 12.5 +/- 1.2 gm/dl in the aprotinin group and the placebo group, respectively. Platelet counts determined at fixed times perioperatively did not differ between the two groups. In contrast, template bleeding time measured in 32 study patients was distinctly different between groups, with a postoperative rise of 6.2 +/- 2.1 minutes in the placebo group opposed to only 1.5 +/- 1.1 minutes in the aprotinin group.(ABSTRACT TRUNCATED AT 250 WORDS)

Optical properties of fiber optic surgical tips

The optical emission pattern of experimental sphere-tipped fibers and an assortment of shapes of sapphire-tipped fibers has been measured. The emission patterns were recorded in both air and water. These patterns show that cone and wedge shaped tips unexpectedly have focusing properties. The observed patterns help give an understanding of the results that the tips produce on tissues. The optical analysis suggests ways of improving tip designs.

Microprocessor-controlled hemodynamics: a step towards improved efficiency and safety

Manual titration of sodium nitroprusside (SNP) is widely used for treatment of hypertension following cardiac surgery. This study compared conventional manual control with control by a research prototype of an automatic infusion module based on a proportional plus integral plus derivative (PID) negative feedback loop. Two groups of coronary artery bypass patients requiring SNP for postoperative hypertension were studied prospectively. In the first group, hypertension was controlled by manual adjustment of the SNP infusion rate, and in the second, the infusion rate was controlled automatically. The actual and desired mean arterial pressures (MAP) over consecutive ten-second epochs were recorded during the period of infusion. The MAP was maintained within 10% of the desired MAP 45.8% of the time in the manual group, compared with 90.0% in the automatic group, and the mean percent error in the automatic group was significantly less than in the manual group (P less than 0.01). It is concluded that adoption of such systems will result in improved patient safety and may facilitate more effective distribution of nursing staff within intensive care units.

Free radicals. Formation, function and potential relevance in anaesthesia

Free radical species are ubiquitous in plant and animal life. This article describes briefly the formation of certain oxygen-centred free radicals which are essential for aerobic metabolism and host defences in humans. The mechanism of cytotoxicity of excess or inappropriate free radical production is described. The potential relevance of free radical tissue injury to the anaesthetist is illustrated using oxygen toxicity, adult respiratory distress syndrome and halothane hepatitis as examples.

Rate of inactivation of human and rodent hepatic methionine synthase by nitrous oxide

The rate of inactivation of hepatic methionine synthase by nitrous oxide has been determined in 22 patients undergoing laparotomy during general anesthesia, including 70% nitrous oxide. Mean half-time of inactivation was 46 min. Metabolic consequences of nitrous oxide are, thus, critically dependent on the duration of anesthesia, and are unlikely to be significant during exposures of less than 40 min. Inactivation of methionine synthase is very much more rapid in the rat exposed to 50% nitrous oxide, with a half-time of 5.4 min.

Effect of aprotinin on need for blood transfusion after repeat open-heart surgery

Of 22 patients undergoing repeat open-heart surgery through a previous median sternotomy wound 11 were randomised to receive the serine proteinase inhibitor aprotinin in high dosage (about 700 mg intravenously from the start of anaesthesia to the end of operation, depending on the length of the surgical procedure). Their mean blood loss was 286 ml compared with 1509 ml in the 11 control patients (p less than 0.001), and mean haemoglobin losses were 8.3 g and 78 g, respectively (p less than 0.001). Blood transfusion requirements were eightfold higher in the control group than in the aprotinin group, 7 of whom received only the single unit of their own blood taken before cardiopulmonary bypass.

Effects of aprotinin on hemostatic mechanisms during cardiopulmonary bypass

Cardiopulmonary bypass (CPB) is associated with activation of humoral systems, which results in the release of proteases. These proteases may affect platelets and stimulate granulocytes. In the present study, the protease inhibitor aprotinin was given in high doses to 11 patients to achieve plasma concentrations of more than 150 kallikrein inactivator units per milliliter during CPB. At such concentrations, kallikrein and plasmin are effectively inhibited. This treatment resulted in platelet preservation during CPB. Platelet numbers were virtually unaffected, and thromboxane release was prevented in the aprotinin-treated group in contrast to the control group. Postoperatively, hemostasis was significantly better preserved after aprotinin treatment (blood loss of 357 ml in the treated group versus 674 ml in the untreated group; p less than 0.01). Since tissue-plasminogen activator activity was similar in both groups, the improved hemostasis most likely should be attributed to platelet preservation. Furthermore, aprotinin lessened neutrophilic elastase release, which might contribute to decreased pulmonary dysfunction in patients at risk.

A comparison of 99mTc-DTPA and 113mIn-DTPA aerosol clearances in humans. Effects of smoking, hyperinflation, and in vitro oxidation

As an index of permeability of the alveolar epithelium, the clearance of an inhaled aerosol of 99mTc-DTPA is increased in several disease states. However, the usefulness of the test to assess the severity of disease is limited because healthy smokers also have abnormally rapid rates of clearance. Because the stability of the 99mTc-DTPA bond might be a contributory factor, we tested the affinity of 99mTc for DTPA in vitro, and in groups of healthy smokers (n = 13) and nonsmokers (n = 7) we measured the clearances of 99mTc-DTPA and 113mIn-DTPA, which have a similar molecular shape and charge. In vitro, sodium hypochlorite or hydrogen peroxide released as much as 98% of free 99mTc from the 99mTc-DTPA complex. When incubated with human neutrophils stimulated with phorbol myristate acetate, between 4 and 7% of free 99mTc-DTPA was released after 30 min, and 12% was released after 60 min. In vivo, the clearances of both 99mTc-DTPA and 113mIn-DTPA in the smokers (n = 13) were faster than in the nonsmokers (n = 7) (p less than 0.05). Within the smokers, the mean 99mTc-DTPA clearance (T1/2 25 +/- 4 min) was faster than the mean 113mIn-DTPA clearance (34 +/- 6 min), (p less than 0.05). For nonsmokers, the difference was smaller (T1/2 99mTc-DTPA, 56 +/- 6; T1/2 113mIn-DTPA, 62 +/- 6) and not significant. During hyperinflation, smokers (n = 8) and nonsmokers (n = 8) both demonstrated an increase in 113mIn-DTPA clearance.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute ventilatory changes during i.v. induction of anaesthesia with thiopentone or propofol in man. Studies using inductance plethysmography

We have compared the acute ventilatory changes during induction of anaesthesia with equipotent doses of thiopentone and propofol in 12 premedicated female patients. Using ventilatory inductance plethysmography we have shown that both agents depress respiration to a similar and significant degree (P less than 0.001). However, although the functional residual capacity was reduced in patients receiving propofol, it increased slightly after induction with thiopentone (P less than 0.05).

Retrograde tracing shows that CGRP-immunoreactive nerves of rat trachea and lung originate from vagal and dorsal root ganglia

The origins of sensory innervation of the lower respiratory tract are thought to be principally the nodose and jugular ganglia of the vagus nerve. It has been suggested and partially demonstrated that there is also a component arising from dorsal root ganglia, but the segmental levels involved are not known precisely. We have therefore investigated the origins of sensory nerves within the rat respiratory tract, particularly those containing calcitonin gene-related peptide (CGRP), using the technique of retrograde axonal tracing combined with immunohistochemistry. Injections of True blue were made into extra-thoracic trachea (n = 4 rats) and percutaneously into the right and left lung (n = 4 each). Retrogradely labelled neuronal perikarya were detected in vagal and dorsal root ganglia, and sympathetic chain ganglia. CGRP-immunoreactive cells were seen only in vagal and dorsal root ganglia. Tracheal innervation arose bilaterally in the vagal sensory ganglia but those on the right side represented the principal source; the majority of CGRP-containing neurons occurred in the jugular ganglion. A very small component of labelling occurred in spinal ganglia at levels C2-C6. The sensory innervation of the lungs was seen to arise predominantly from the ipsilateral dorsal root ganglia (45% of cells CGRP-immunoreactive) at levels T1-T6. In contrast to the trachea, the contribution of vagal sensory neurones to the lungs appeared to be less than that of the spinal ganglia. These results show that the sensory innervation of the rat lungs has a major origin in the dorsal root ganglia, in which almost half of the involved neurons contain CGRP, and confirm that most CGRP-immunoreactive nerves in the trachea arise in the right jugular ganglion.

Failure of aerosolised 99mTc DTPA clearance to predict outcome in patients with adult respiratory distress syndrome

The rate of clearance of technetium-99m labelled diethylene triamine pentacetic acid (99mTc DTPA) was measured in 32 patients with adult respiratory distress syndrome to determine if a more rapid clearance rate, possibly reflecting a more severe abnormality of pulmonary function, was associated with a reduced likelihood of recovery from pulmonary failure. Although the mean rate of clearance from lung to blood (T1/2LB) of 99mTc DTPA was more rapid in the patients (T1/2LB = 29 (SEM 3.2) min than in 42 normal subjects (T1/2LB = 59 (1.8)min), there was no difference between the clearance rate in the 18 patients who recovered from respiratory failure (T1/2LB = 31 (5) min) and the 14 who died (T1/2LB = 27 (4) min). Additionally, not all patients studied had abnormally rapid clearance rates. In 12 of the 32 patients the T1/2 fell within the range for normal individuals; this was found more commonly in patients who were predisposed to develop adult respiratory distress syndrome by pancreatitis or massive blood transfusion. These data suggest that a single measurement of 99mTc DTPA clearance in patients with established respiratory failure and adult respiratory distress syndrome is of no value in assessing the likelihood of recovery from this condition.

Epithelial and endothelial flux after bypass in dogs: effect of positive end-expiratory pressure

Cardiopulmonary bypass (CPB) causes lung injury that occasionally progresses to the adult respiratory distress syndrome (ARDS). We measured the effect of 10 cmH2O of positive end-expiratory pressure (PEEP) on small solute and protein flux in dogs 1 wk before and 2 h after the completion of CPB. As an index of alveolar epithelial permeability, the clearance from lung to blood of inhaled technetium-99m-labeled diethylenetriaminepentaacetic acid (99mTc-DTPA) was measured. To assess microvascular endothelial integrity, the rate of accumulation in the lung interstitium of intravascular 113mIn-transferrin was measured. The clearance half time (t 1/2) for 99mTc-DTPA in the study dogs declined from 18.8 +/- 1.9 min (mean +/- SE) at base line to 9.4 +/- 2.0 min during PEEP (P less than 0.05). Two hours after CPB, the t 1/2 was 8.1 +/- 1.6 min at base line and unchanged during PEEP. The 113mIn-transferrin rate of accumulation was unchanged by PEEP before CPB. After CPB, the index was 3.25 +/- 0.95 slope/min X 10(-3) (P less than 0.05). Of the five dogs with a significant slope, four showed a decrease in microvascular flux during PEEP, although for the group the mean change in slope was not significant (P = 0.10). We conclude that the application of PEEP does not increase 99mTc-DTPA clearance in lungs already injured by CPB, and may actually decrease the apparent microvascular protein flux in some cases.

The effect of human antiendotoxin monoclonal antibodies on endotoxin-induced lung injury in the rat

A model of endotoxin-induced lung injury was developed in the rat. We found that 24 h after intravenously administered endotoxin (3 mg/kg) there was increased clearance of the isotope 99mTcDTPA from the lung to blood, increased neutrophils in the lung in bronchoalveolar lavage, and increased levels of products of peroxidation of lipids and nucleic acid in the serum. Using this model, we evaluated the effect of pretreatment of rats with a human monoclonal antibody specific to the core glycolipid that is common to all endotoxins. We found that pretreatment prevented the increased clearance of 99mTcDTPA from the lung, as well as the increase in lipid peroxidation products in the serum. The antibody did not prevent increased neutrophil accumulation in the lung. The findings suggest that the administration of human antiendotoxin monoclonal antibodies prior to endotoxemia may prevent some of the changes in the lung associated with endotoxin.

Propofol infusion for sedation in the intensive care unit: preliminary report

Propofol (2,6,di-isopropylphenol) was given by continuous intravenous infusion to provide sedation after cardiac surgery in 30 patients and its effects compared with those of midazolam given to a further 30 patients. Propofol infusion allowed rapid and accurate control of the level of sedation, which was satisfactory for longer than with midazolam. Patients given propofol recovered significantly more rapidly from their sedation once they had fulfilled the criteria for weaning from artificial ventilation and as a result spent a significantly shorter time attached to a ventilator. There were no serious complications in either group. Both medical and nursing staff considered the propofol infusion to be superior to midazolam in these patients. These findings suggest that propofol is a suitable replacement for etomidate and alphaxalone-alphadolone for sedating patients receiving intensive care.

Increased pulmonary transvascular protein flux after canine cardiopulmonary bypass. Association with lung neutrophil sequestration and tissue peroxidation

We examined the hypothesis that increased pulmonary transvascular protein flux after cardiopulmonary bypass (CPB) is mediated in part by neutrophil-derived, oxygen-free radicals. Measurements of transvascular lung 113mIn-transferrin flux, transpulmonary neutrophil counts, and plasma concentrations of thiobarbituric acid (TBA) reactive substances were made in 8 dogs after CPB and in 6 dogs who underwent thoracotomy alone. The TBA reactivity is indicative of lipid peroxidation and was used as an index of oxygen-free radical release. All 14 dogs had a baseline measurement of lung protein flux 1 wk prior to thoracotomy. In the bypass dogs, lung protein flux was -0.2 +/- 0.3 protein flux units (mean +/- SEM) at baseline and increased significantly after bypass to 3.3 +/- 1.0 (p less than 0.01). The control thoracotomy group had baseline values similar to the baseline studies in the CPB dogs (0.2 +/- 0.3 units), but no significant difference was noted after thoracotomy. The CPB dogs showed initial significant parallel falls in left atrial (LA) and central venous (CV) neutrophil counts during bypass (baseline, 5.3 +/- 0.7 X 10(9) cells/L in both sample sites, falling to 3.0 +/- 0.5 and 2.9 +/- 0.5, respectively, p less than 0.001), but a significant CV-LA transpulmonary gradient existed only when pulmonary perfusion recommenced after a period of total asystole. Concentration of TBA reactive substances increased significantly during the course of bypass (baseline LA, 6.4 +/- 0.5 nmol/L, baseline CV, 6.4 +/- 0.5, increasing to 9.8 +/- 1.0 and 9.4 +/- 1.6 at the end of bypass, respectively, p less than 0.01), but likewise, there was a significant transpulmonary gradient only after reversal of asystole.(ABSTRACT TRUNCATED AT 250 WORDS)

The non-steroidal anti-inflammatory agent, indoprofen, does not protect against hydrochloric acid induced lung injury in the rat

The effects of pulmonary instillation of hydrochloric acid on solute flux from the lung (measured as the clearance of 99mTcDTPA) together with an index of oedema formation (the ratio of lung wet weight to lung dry weight) was measured in rats. There was a significant increase in 99mTcDTPA clearance (P less than 0.001) and also in lung wet:dry weight ratio (P less than 0.01) 4-5 h following acid challenge. There was no difference in the effects of challenge with acid of pH1 and pH2. In addition, intravenous injection of indoprofen (20mg/kg) a non-steroidal anti-inflammatory agent failed to produce any beneficial effect on the variables under study when given after acid (pH2) challenge. There was also histological evidence of an influx and sequestration of granulocytes into the lung. Despite this, the plasma concentration of thiobarbituric acid reactive material (used as an index of cell-derived, oxidant-free radical production) was significantly reduced in all acid-treated groups. These data show that hydrochloric acid will initiate a severe inflammatory response in the lung of the rat and that the non-steroidal anti-inflammatory agent indoprofen when given after the injury produced no evidence of a beneficial effect on this inflammatory response.

Infused salbutamol accentuates acid-induced lung injury in the rat

The effect in the rat of salbutamol infusion (1 microgram min-1 kg-1) on acid-induced lung injury has been determined. Severity of lung injury was assessed by two techniques: the pulmonary clearance of 99mTc-diethylenetriaminepenta-acetate (99mTc-DTPA) and the lung wet/dry weight ratio, giving indices of alveolar epithelial permeability and transendothelial water filtration respectively. Mean half-time of clearance of 99mTc-DTPA was increased significantly in rats who had intratracheal acid-induced injury and control (saline) intravenous infusion (19.4 +/- 2.6 min) compared with non-acid-treated rats (98.1 +/- 7.2) (P less than 0.0001). However, those animals who had intratracheal acid injury and subsequent salbutamol intravenous infusion had significantly faster clearance (11.5 +/- 1.9) than the acid and control infusion group (P less than 0.05). Gravimetric lung water in the acid-only rats (expressed as wet/dry weight ratio) was increased significantly (6.4 +/- 0.3) compared with the non-acid-treated controls (5.4 +/- 0.2) (P less than 0.01). Acid-treated rats who had salbutamol infused had dramatically increased lung water (10.0 +/- 0.6) (P less than 0.001 vs acid and control infusion). Intravenous salbutamol infusion itself produced no significant difference in the results for both techniques, compared with the non-acid-treated time-course controls. Infused salbutamol accentuates acid-induced lung injury in the rat. Possible factors responsible for these findings include beta 2-adrenergic agonist mediated inhibition of hypoxic pulmonary vasoconstriction (HPV) and a predominant beta 1-adrenergic agonist inotropic effect of salbutamol with resultant rise in pulmonary artery pressure.

Comparison of lung vascular and epithelial permeability indices in the adult respiratory distress syndrome

Measurements of pulmonary clearance of inhaled 99mTc-DTPA and transvascular 113mIntransferrin flux were made in 12 patients with established ARDS and 14 volunteer control subjects (7 smokers and 7 nonsmokers). Smokers had significantly increased 99mTc-DTPA clearance (clearance rate constant, 3.6 +/- 0.8; mean +/- SEM) compared with nonsmokers (1.2 +/- 0.1). All patients with ARDS had increased clearance of 99mTc-DTPA (5.2 +/- 0.9), but the finding was nonspecific in that increased clearance overlapped with the findings in normal smokers. Protein flux in smokers (protein flux units, 0.0 +/- 0.2) was similar to that in nonsmokers (0.3 +/- 0.2). In 9 of the 12 patients with ARDS, protein flux was increased, and as a group (3.2 +/- 1.0) they differed significantly (p less than 0.01) from the combined smoking and nonsmoking control subjects (0.2 +/- 0.1, n = 14). The parameters of DTPA clearance and transvascular protein flux correlated well in the patients with ARDS (Spearman's rank correlation = 0.71, p less than 0.01). Although 99mTc-DTPA clearance is a sensitive technique in ARDS, a single study in this context does not allow a diagnostic conclusion because of its non-specificity. Abnormal protein flux appears to be more specific for ARDS but was not a universal finding in the patients studied.

Increased production of peroxidation products associated with cardiac operations. Evidence for free radical generation

We investigated the degree and time course of neutrophil sequestration into human lungs during cardiac operations. At the same time, measurement of the concentration of peroxidation products in the plasma was used as an index of oxidant free radical activity. The study was performed in two groups of patients. Group A (n = 11) had studies extending over the entire operative period and showed a highly significant sequestration of neutrophils into the lung, together with a highly significant (p less than 0.001) rise in peroxidation products from 2.8 +/- 0.12 nmol/ml(mean +/- standard error of the mean)before bypass to a peak of 5.05 +/- 0.13 nmol/ml at the end of bypass. As these changes occurred only during the time after release of the aortic cross-clamp, we investigated this period in more detail in a second group of patients (Group B, n = 7). Results from this group showed that significant release of peroxidation products occurred at the same time as pulmonary neutrophil sequestration. This study has produced evidence of increased oxidant activity in the lung associated with cardiac operations. Nevertheless, it is not known whether the neutrophils sequestered into the lung alone induced the increased activity. Similarly, whether neutrophil-derived oxidant species are the sole cause of lung tissue injury remains unproved.

Effect of raised thoracic pressure and volume on 99mTc-DTPA clearance in humans

Although positive airway pressure is often used to treat acute pulmonary edema, the effects on epithelial solute flux are not well known. We measured independently the effect of 1) positive pressure and 2) voluntary hyperinflation on the clearance of inhaled technetium-99m-labeled diethylenetriaminepentaacetic acid (99mTc-DTPA) in six nonsmokers and six smokers. Lung volumes were monitored by inductance plethysmography. Each subject was studied in four situations: 1) low end-expiratory volume (LO-), 2) low volume plus 9 cmH2O continuous positive airway pressure (LO+), 3) high end-expiratory volume (HI-), and 4) high volume plus continuous positive airway pressure (HI+). The clearance half time of 99mTc-DTPA for the nonsmokers decreased from 64.8 +/- 7.0 min (mean +/- SE) at LO- to 23.2 +/- 5.3 min at HI- (P less than 0.05). Positive pressure had no synergistic effect. The mean clearance half time for the smokers was faster than nonsmokers at base line but unaffected by similar changes in thoracic volume and pressure. We conclude that, in nonsmokers, positive airway pressure increases 99mTc-DTPA clearance primarily through an increase in lung volume and that smokers are immune to these effects.