Use of intracoronary KCl in the beating and asystolic heart to determine the mechanism of initiation of the left ventricular mechanoreceptor reflex.

To provide further evidence that the veratrum alkaloids' mechanical, positive inotropic effect and not their chemical depolarising action predominates in initiating the left ventricular mechanoreceptor (including the Bezold) reflex the effect of intracoronary KCl, a chemical depolarising agent like the veratrum alkaloids, but with a negative inotropic effect, was studied in beating and verapamil-asystolic hearts. Five dogs were placed on a total cardiac bypass, pneumonectomised and their coronary and systemic circulations isolated and perfused separately, at a constant rate, so that changes in systemic pressure reflected changes in systemic resistance. Injection of 5 mmol X litre-1 KCl into the isolated coronary circulation caused cardiac asystole and a resultant reflex rise in systemic pressure (resistance) of 26 +/- 9% (p less than 0.05) above the control of 10.5 +/- 0.7 kPa (79 +/- 5 mmHg). This pressure rise, which indicates predominance of KCl's mechanical, negative inotropic over its chemical depolarising effect, was abolished by vagotomy, indicating its reflex nature. Contrariwise, in five other pneumonectomised dogs, similarly perfused on total cardiac bypass but with cardiac asystole from intracoronary verapamil, a subsequent, similar intracoronary dose of KCl now produced a fall in systemic pressure (resistance) of 8 +/- 2% (p less than 0.005) below the control of 12.8 +/- 0.5 kPa (96 +/- 4 mmHg). This pressure fall, presumably due to chemical depolarisation of the left ventricular mechanoreceptors, was also abolished by vagotomy.(ABSTRACT TRUNCATED AT 250 WORDS)

Reflex hypotension due to regional activation of left ventricular mechanoreceptors to explain the hypotension noted in clinical myocardial ischaemia or reperfusion.

To determine if regional increases in myocardial contractility, as may occur clinically in angina pectoris, myocardial infarction, or coronary thrombolysis, can initiate the reflex hypotension that sometimes accompanies these conditions, regional injections of positive inotropic agents were made into 32(3)% of the left ventricular myocardium in seven pneumonectomised dogs on total cardiac bypass. The coronary and systemic circulations were isolated and perfused separately. The systemic circulation was perfused at a constant rate so that changes in systemic pressure reflected changes in resistance. Regional injections of doses from 0.001 to 1.0 micrograms noradrenaline in a 0.1 ml volume appreciably increased regional contractility, detected visually and by strain gauge arches, whereas global contractility (left ventricular peak dP/dt) was increased much less. This caused a fall in the systemic pressure (resistance) of 14(2)% below the control value of 78(5)mm Hg, at the largest dose. The decreases in resistance were abolished by bilateral vagotomy, proving their reflex nature. The smaller (0.0001-0.01 micrograms) doses of noradrenaline and the smallest (0.25 micrograms) dose of veratridine increased regional contractility almost without increasing global contractility, indicating that the increase in regional contractility was the major cause of the reflex decrease in systemic resistance. In one animal a decrease in contractility in a control myocardial region occurred simultaneously with the experimentally produced increase in regional left ventricular contractility. This decrease may be analogous to the increase in contractility in the non-ischaemic left ventricular myocardium that occurs simultaneously with the decrease in contractility in the ischaemic region in clinical or experimental myocardial infarction. Left ventricular mechanoreceptors in the region with increased contractility probably initiate the reflex hypotension that sometimes occurs in both circumstances. Thus in angina pectoris or acute myocardial infarction the reflex hypotension probably originates in the hyperactive non-ischaemic myocardial region, whereas in coronary arterial thrombolysis it probably originates in the newly reperfused, formerly ischaemic, region.

A new approach to massive blood transfusion during pediatric liver resection.

Morbidity and death during liver resection in children are due to hemorrhage and the consequences of massive transfusion. To overcome these problems, a new rapid method of blood transfusion was used in four children (8 to 35 months, 8.6 to 13 kg) undergoing extensive hepatic resection for tumor (tumor weight, 440 to 1625 gm). The rapid infusion device consisted of a roller pump and a bubble oxygenator-warmer circuit primed with washed packed red cells resuspended in fresh-frozen plasma and calcium-free balanced salt solution (Plasmalyte). The infusate was warmed, oxygenated, and buffered before it was administered. An average of 5130 ml per patient of this reconstituted blood was infused at an average rate of 122 +/- 45 ml/min, with peak infusion rates sometimes as great as 1 L/min. Cardiac output, pulmonary artery wedge pressure, body temperature, urine output, blood gases, blood chemistries, and coagulation factors remained unchanged during and after these massive transfusions. Blood transfusion at rapid rates required during pediatric liver resection can be accomplished safely if the storage lesion of the bank blood is previously corrected.

A biomechanical study of the aponeurotic inguinal hernia repair.

The aponeurotic inguinal hernia repair is essentially a union of the aponeuroses of the external oblique and transversus abdominis muscles in the groin. Its tension-free status and resistance to intra-abdominal stress were measured in a biomechanical study. Comparative studies were made with the American Bassini procedure. Suture tensions were measured at three sites in six aponeurotic repairs and the mean tension was 3.9 +/- 2.9 grams, which was within the accuracy of the combined transducer and recorder measurement. Similar measurements in six American Bassini operations registered 633 +/- 230 grams mean tension. A relaxing incision in the Bassini repair reduced but did not eliminate tension. Mean tension figures remained at 401 +/- 198 grams. Specimens of external oblique aponeuroses in six random patients were tested, counter to their parallel fibers, in a tensiometer. The thickness of the specimens varied from 0.21 to 1.2 millimeters. The tissue mean stress capacity under tension was 4.1 +/- 1.9 x 10(6) pascals with a range of 2.5 to 6.5 x 10(6) pascals. An analysis was made of the impact of intra-abdominal pressure at five possible sites of failure in the aponeurotic repair. Established values of suture bite tissue tear resistance and our values of external oblique aponeurosis stress tension were used to calculate the resistance of the aponeurotic repair to established values of intra-abdominal pressure. The maximum reported intra-abdominal pressure is 26.6 kilopascals. In this series, the largest reconstructed inguinal floor was 5 square centimeters and supported a load of 1,360 grams force. There was a safety margin of 2.4 against a failure of tissue of minimal thickness (0.2 millimeter) in the aponeurotic repairs when subjected to maximum intra-abdominal pressure. With average thickness of specimen (0.45 millimeter) there was a safety margin of 5.4. The 2-0 polypropylene suture had a requirement of 1,590 grams force maximum knot pull strength, which was much greater than our measured tensions. The added suture-line tension created by the assumed intra-abdominal pressure with sutures spaced one-half centimeter apart was calculated to be 65 grams force. This figure is well below the reported tensions of 5,300 and 9,100 grams force resisting tissue pull through failure in the external oblique and transversus aponeurosis, respectively. The transversalis aponeurosis component of the repair had shown in the proceeding study a tensile strength greater than the external oblique aponeurosis, and by analogy, a competence to resist intra-abdominal pressure.(ABSTRACT TRUNCATED AT 400 WORDS)

Factors influencing early survival after liver transplantation.

The purpose of this study was to analyze data from all adult and pediatric liver transplants performed between January 1, 1983 and January 15, 1986 at the University of Minnesota Hospital and identify perioperative variables that predict patient survival and could aid in patient selection. Charts, intraoperative anesthesia records, blood bank records, flow sheets, outpatient records, and autopsy reports were examined in 45 pediatric and 15 adult patients who underwent primary orthotopic liver transplantation. Analysis of the data can be summarized as follows: (1) Pediatric patients whose coagulation parameters could not be corrected prior to operation and who consequently required preoperative exchange transfusion had poorer outcomes than those not requiring an exchange to correct coagulation parameters. (2) The rapid infusion technique for massive blood transfusion resulted in significantly decreased blood loss and intraoperative blood product replacement. (3) Twenty-four hour postoperative factor V levels were good predictors of survival. Patients with poor factor V levels required rigorous replacement of coagulation factors. (4) Pediatric patients with uncorrectable coagulopathies requiring immediate postoperative exchange transfusion had extremely high mortality.

Automated data acquisition and analysis in muscle physiology research.

Research in muscle physiology has progressed in both the volume and complexity of data examined. Dependence on manual methods to analyze and condense this amount of information can present a narrow bottleneck to the efficient completion of a study, and can compromise the reliability of the results. We designed a general purpose computerized system for data acquisition in experiments in our cardiovascular physiology laboratory. In addition, we developed a software program specifically for the analysis of data from studies of isolated, isometrically contracting myocardium. This system has reduced the time for analysis of such data by approximately 50-fold over that of manual techniques, and has contributed significantly to our confidence in the measured results.

The aponeurotic repair of inguinal hernia.

Inguinal hernia repair has relied on sewing supporting structures to a fixed ligament, and suture line tension has been recognized as a cause of operative failure. Aponeurotic inguinal hernia repair does not rely on suturing fasciae to ligaments; it is a tension-free repair that does not require relaxing incisions to relieve tension. Aponeurotic repair can be performed for primary or recurrent hernias. It use will enlarge the choices of procedures best suited to the needs of a specific hernia.