Vascular interface system for automation of haemodynamic monitoring and therapy.
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Sodium nitroprusside (SNP) is rarely used in cardiology. It is reserved traditionally for severe episodes of arterial hypertension. Certain states of refractory heart failure represent new indications for use, which implies a double haemodynamic monitoring system: continuous control of systemic blood pressure by intra-arterial catheterization; control of pulmonary pressure and repeated measurements of cardiac output. Prolonged treatment requires continuous biological monitoring of toxicity and careful control of kidney function. As a moderator of blood pressure, SNP is remarkably effective. The hypotensive effect is immediate, readily reversible and generally tachyphylaxis is not observed. The effect of SNP on cardiac work is one of double load reduction: mainly a reduction in afterload or pressure and systemic resistance and a reduction in preload or pressure of ventricular filling. In this respect, SNP can be used effectively for severe cases of heart failure intractable to traditional cardio-stimulatory and diuretic treatments and stemming from diverse causes: acute stage of myocardial infarction, ventricular dilatation, mitral papillary syndrome, heart failure, either subacute or chronic, of various causes. As a rule, the immediate results are positive. Taking the patient off the drug can be difficult and may cause a return to the previous haemodynamic situation.
A Swan-Ganz catheter, employed for haemodynamic monitoring, was put to a use not described previously. Pulmonary angiography was performed through the catheter at the bedside with minimal discomfort or complication. In this case it was possible to determine that a lung abscess was responsible for a translucency in the right lower lobe. This was subsequently confirmed at postmortem examination.
A 30-bed coronary care unit with facilities for fluoroscopy, haemodynamic monitoring, mechanical heart assistance, and long-term electrocardiographic monitoring operated at a reasonable cost over five years. Much of the work was entrusted to trained nurses, and there was close consultation with cardiac surgeons over those patients who needed catheterisation or surgery. New procedures greatly reduced the numbers of early deaths from cardiac arrest and cardiac failure but had less influence on late mortality. Hospital mortality for all 3353 patients was 6-8%, and for patients under 65 with definite infarction, who were admitted direct it was 5-7%.
Stroke volume was determined from the pulmonary artery pressure record by application of the pulse contour method. Pulmonary artery pressure records were obtained in 17 patients using a high fidelity catheter-tip pressure transducer and simultaneous measurements of cardiac output were obtained from indicator dilution curves. The formula used was SV = KP sa (i plus T s/Td) where Psa is the planimetered area beneath the systolic portion of the pulmonary artery pressure curve. Ts and Td are the durations of systole and diastole, and K is a constant. Stroke volume was altered by isometric handgrip exercise and/or pharmacological agents in 15 patients. Serial measurementswere made in 2 patients in acute pulmonary oedema after myocardial infarction. Comparison of a wide range of values of stroke volume by the pulse contour method with those obtained from dye dilution curves showed a good correlation (r plus 0.97, P smaller than 0.001) regression line y = 1.01 times - 0.47. Measurement of stroke volume from the pulmonary artery pressure contour is a technique of potential value in serial haemodynamic monitoring.
In cardiac failure unresponsive to digoxin and diuretics, afterload reduction brings about a dramatic increase in cardiac output, renal perfusion and responsiveness to diuretics; furthermore, the decrease in venous pressure relieves the dyspnoea. Intravenous vasodilators should only be used when sophisticated haemodynamic monitoring equipment and experienced physicians are at hand. Indications for the use of these agents are severe cardiac failure, acute myocardial infarction complicated by left ventricular failure, persistent ischaemic pain and limitation of infarct size. A wide variety of oral vasodilator agents is available, all having different sites of action; the choice of vasodilator agents should be tailored to the needs of the patient. Treatment with these agents is indicated in patients in whom cardiac failure becomes refractory to conventional therapy with digoxin and diuretics. The utmost care must be taken to avoid further impairment of cardiac output by excessive reduction of the left ventricular end-diastolic pressure (LVEDP) and hypotension, which will jeopardize myocardial, renal and cerebral perfusion.
In this article 2 cases of myocardial infarction with haemodynamically dominant right ventricular infarction are reported. The incidence and significance of the condition are discussed. The use of haemodynamic monitoring in diagnosis and management is stressed and the response to fluid therapy, either alone or together with inotropic drugs, is discussed.
INTRODUCTION: Pulmonary artery catheters are used widely in cardiac surgery despite observed associations with worse outcomes and guidelines that recommend against their routine use. No adequately powered randomised trials are available. METHODS: The PUMA Pilot was a multicentre, randomised, parallel assignment, open-label, pilot and feasibility trial conducted at three tertiary cardiac surgery centres. Eligible patients were adults undergoing coronary artery bypass grafting, aortic valve replacement or surgery on the aortic root or ascending aorta with or without aortic valve replacement, with a predicted surgical mortality of < 2%. Patients were allocated randomly to receive a pulmonary artery catheter or a central venous catheter inserted immediately before surgery. The primary feasibility outcome was protocol compliance, defined as receiving the assigned intervention without crossover. Secondary feasibility outcomes were eligibility rate; recruitment proportion and rate; data completeness; and rate of clinician refusal. RESULTS: We screened 480 patients and 206 (43%) were eligible; 150/203 (74%) approached provided informed consent. Three of 206 (1%) eligible patients were not included due to clinician refusal. Of 149 patients who were randomised, 76 were assigned to the pulmonary artery catheter group and 73 to the central venous catheter group. For the primary feasibility outcome, 147 patients (99%) received the allocated intervention. Data were complete for 144 (97%) patients. Median (IQR [range]) days alive and at home at 30 days was 23.7 (21.9-24.7 [7.0-26.0]) in the pulmonary artery catheter group and 22.9 (20.8-23.9 [8.6-25.8]) in the central venous catheter group. Acute kidney injury occurred in 26/76 (34%) patients in the pulmonary artery catheter group and 14/73 (19%) in the central venous catheter group. DISCUSSION: A randomised trial of pulmonary artery catheters compared with central venous catheters in low-risk cardiac surgery is feasible. Such a trial would address significant practice variability and inform international guidelines.
Advances in the conservative treatment of cardiogenic shock have been achieved by a combination of the use of drugs (dopamine, furosemide, prednisolone), artificial ventilation and parenteral nutrition (to avoid a negative energy situation). Basic requisites for such therapy are the continuous monitoring of haemodynamic parameters (pulmonary wedge pressure, cardiac index) and of laboratory results (blood gas analysis, pO2, pCO2, osmolarity, blood glucose level). Assisted circulation (IABP) should be started immediately if it becomes apparent that little or no effect has been achieved by medical treatment. Protection is provided by the IABP for further investigation of the patient by selective coronary angiography and surgical intervention whenever possible.
Haemodynamic parameters were monitored for one week (in greatest detail during the first 24 hours) in 35 severely injured persons who had been admitted for treatment within one hour after the accident and, as judged by the type of injury, had probably lost more than 1 1/2 litres of blood. The estimations included not only blood pressure, heart rate and shock index; but the cardiac index, pulmonary arterial pressure, pulmonary capillary pressure and parameters of oxygen transport were also determined with the aid of Swan-Ganz catheters. The importance of the data as guide-lines for the correct type of intensive therapy and their prognostic significance are discussed. The evidence provided by the cardiac index, pulmonary arterial and capillary pressure and the parameters of oxygen transport are of particular importance in these cases. A list is added of the values of some haemodynamic factors which should be taken into account in the initial treatment of severely injured persons.
In order to study the importance of atrial systole, the authors used different stimulus modalities at the same rate; they stimulated the right ventricle, the right atrium, and the two. The haemodynamic parameters were monitored by microcatheterisation of both right and left sides. A comparative study using controls and patients with left ventricular failure showed the improvement in the haemodynamic picture which was obtained in the latter group when the atrio-ventricular sequence was correct.
The catheter tips of 152 patients, who were haemodynamically supervised by pulmonary artery monitoring or continuous cardiac output determination, were bacteriologically examined. 106 cultures remained sterile, 21 cultures revealed a growth of non pathogenic organisms. Staphylococcus aureus was cultured 15 times, pseudomonas aeruginosa 4 times, Citrobacter as well as Escherichia coli twice, and Klebsiella and Enterobacter once each. There was no statistically significant connection between dwelling period and contamination. Also diabetes mellitus or corticoid medication in high dosage had no significant influence on contamination rate.
A clinical study was carried out to evaluate the usefulness of intravenous lorazepam, given for sedation instead of opiate narcotics or diazepam, in 25 seriously-ill patients being treated in a respiratory and intensive care unit. All but 3 patients were on assisted ventilation. Standard doses of 4 mg lorazepam were given at 4 or 6-hourly intervals for periods up to 25 days. ECG, haemodynamic stability and biological determinations were monitored constantly. Apart from some delay in onset of action, lorazepam proved to be a useful sedative with diminished recall on the part of the patients. No side-effects were reported, nor was there any local reaction to the injection. Cardiac output was measured in 9 patients following intravenous administration of a single-dose of either 4 mg or 8 mg lorazepam. No significant changes were recorded.
Having employed routinely the monitor of cerebral function in cardiac surgery operations for about a year, the authors now present an analysis of the variations in the traces of a group of 57 patients. They have found, when there is no major haemodynamic consequence associated with the induction of anaesthesia, and when there are no difficulties of a surgical or a technical nature accompanying the artificial extra-corporeal circulation, that the monitor curve stays perfectly stable. On the other hand, all sudden haemodynamic changes result in hypotension (haemorrhage, dysrhythmia, and a fall in flow in the extracorporeal circulation) that is reflected in the level of the monitor curve which also falls. They conclude, using examples of certain variations, that the monitor curve is a supplementary form of surveillance and that the trace recorded simultaneously with the anaesthetic sheet allows retrospective analysis of the haemodynamic events to be performed for each operation.
Phasic left circumflex coronary artery and aortic blood flow were monitored in six awake dogs during a control period and at several degrees of cardiac tamponade. A mean pericardial pressure of 24 plus or minus 3 mm Hg (mean plus or minus SEM) was attained at the maximum tamponade level. Total left circumflex coronary blood flow decreased 51% while the systolic portion of this flow became negative or retrograde. Following acute relief of the tamponade, a coronary hyperaemic response was noted. It it suggested that myocardial ischaemia may be partially responsible for the depressed cardiac function seen in this condition and that extravascular compression of the epicardial vessels may limit the coronary blood flow during systole.
Chloralose-anaesthesized dogs, starved for 24 hours, were used to determine the effects of 10 microgram/kg glucagon, administered i.v. as a single bolus injection, on liver substrates in situ (glycogen, glucose-1-phosphate, glucose-6-phosphate, glucose, fructose-6-phosphate, fructose-1,6-diphosphate, triose phosphates, glycerol-3-phosphate, phosphoenolypyruvate, pyruvate, lactate, citrate, malate, ATP, ADP, and AMP). liver samples were obtained by instant deep-freezing with Wollenberger clamps on four consecutive occasions at 10-minute intervals. Heart rate and blood pressure were continuously monitored. Serial liver sampling per se had no significant effects on liver metabolism or systemic haemodynamics in a group of control animals. In a second group glucagon, administered after the initial freeze-clamp sampling to obtain baseline values, led to a marked activation of the glycogenolytic pathway resulting in glucose release from the liver.