Biomedical subjects
D Royston
Publications and source records attributed to D Royston.
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.
Reduced blood loss following open heart surgery with aprotinin (Trasylol) is associated with an increase in intraoperative activated clotting time (ACT).
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Desmopressin and bleeding.
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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)
Effect of aprotinin on need for blood transfusion in patients with septic endocarditis having open-heart surgery.
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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.
Aprotinin decreases the need for post-operative blood transfusions in patients having open heart surgery.
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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.
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.
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.
Autopsy findings in two cases of liveborn triploidy (69XXX; 69XXY).
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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.
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.
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).
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.