Biomedical subjects
Publications and source records attributed to T Treasure.
Of the practical procedures in a general physician's repertoire, pericardiocentesis is one of the less commonly performed and perhaps among the most worrying. The advent of echocardiography has made the procedure safer but it must be appreciated that the risk of developing a life-threatening complication is probably still higher than during cardiac catheterization or coronary angiography.
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The effects of dopamine and dobutamine on plasma potassium were investigated in dogs using continuous, multi-channel, intravascular ion-selective potassium electrodes situated in the aorta and abdominal and thoracic inferior vena cavae. Doses of 10 and 30 micrograms kg-1 min-1 of each drug were used, and the effects on potassium compared with isoprenaline 0.07 and 0.2 microgram kg-1 min-1. Both the drugs caused a biphasic pattern of potassium change consisting of an initial small rise in the potassium level, followed by a sustained period of hypokalaemia. The changes were greater with the higher dose of each drug compared with the lower dose, but there were no significant differences between the drugs. Comparison of the potassium changes between the three vascular sites studied suggested that the rise in potassium may be a result of release of the ion from the liver, and that the liver may also be the principle site of potassium uptake during the hypokalaemic phase.
The effect of beta 1 and beta 2 blockade on dopamine and dobutamine induced hypokalaemia was investigated in dogs. Arterial plasma potassium was continuously monitored using a potassium-sensitive electrode sited in the abdominal aorta. Dopamine and dobutamine were infused at 15 micrograms kg-1 min-1 into animals pre-treated with atenolol (0.5 mg kg-1) or ICI 118551 (0.5 mg kg-1) and the potassium changes compared to those seen in control animals. The inotrope infusions caused a small and transient rise in plasma potassium (p less than 0.05) followed by a more profound hypokalaemia (p less than 0.05) sustained for the duration of the infusion. The potassium falls in the control animals were similar to those in the beta 1 and beta 2 blockade groups. The results suggest that beta 2 receptor stimulation cannot alone be responsible for dopamine and dobutamine induced hypokalaemia and a multiple receptor activation is postulated.
Evidence has accumulated to indicate that a proportion of patients who undergo coronary artery bypass surgery (CABS) do develop significant cognitive deficits. This study examines whether those patients who report cognitive deterioration after CABS do show cognitive changes as assessed by neuropsychological testing. The patients who considered that aspects of their cognitive function had deteriorated, were not found to have reduced functions as assessed on appropriate neuropsychological tests. When mood state was examined, it was found that those who report a deterioration in a particular cognitive function, tended to have significantly higher levels of depression as assessed by the Beck Depression Inventory and, to a lesser extent, have higher levels of state anxiety. These findings emphasise that subjective reports of cognitive function following CABS do not reflect actual changes in cognition but rather appear to be sensitive to mood state.
Patients undergoing routine coronary artery surgery (N = 76) were compared with those undergoing other major operations (N = 29) in a prospective multidisciplinary study designed to define the incidence of neurological and psychological sequelae. The preoperative state of the carotid and vertebral arteries was defined by digital subtraction angiography. Changes in clinical neurological examination, detailed neuropsychological testing, psychiatric assessment and cerebral blood flow were measured. All preoperative studies were repeated 8 days and 8 weeks after surgery. Clinical neurological examination was repeated in addition on the 1st postoperative day. New focal neurological signs were found in 8% of the cardiac patients and none of the comparison group 24 h after operation (P = 0.9). Global transient neurological dysfunction occurred in 59% of the coronary group in the 1st postoperative day compared with 21% in other forms of surgery (P = 0.0007) but this correlated with postoperative narcotic and sedative drugs. A deterioration in neuropsychological performance was detectable in 73% of coronary cases at 8 days which was more likely to occur with increasing age, longer bypass time and lower perfusion pressure, but similar neuropsychological changes also occurred in 50% of the comparison group. By 8 weeks, there was a significant improvement in the cardiac patients (37%, P less than 0.001) but not in the other group. Cerebral blood flow was reduced at 8 days in the coronary bypass patients but not in the comparison group suggesting that the mechanism of cerebral change may be different in the two groups.
Low energy level internal direct current shocks were used to defibrillate the hearts of 168 patients during procedures performed on cardiopulmonary bypass. In all cases, the core temperature was greater than 32 degrees C and care was taken to correct hypokalaemia and acid-base balance prior to defibrillation. In 78 patients (46%), defibrillation required 2 joules or less, and in 139 (82.7%) cases, defibrillation was effected with 4 joules or less. Only 4 patients required more than 10 joules to defibrillate the heart. This study shows that it is possible to defibrillate hearts during cardiopulmonary bypass with energy levels well below the 20-30 joule shocks commonly used.
To observe and quantify cerebrovascular microembolic events in the central nervous system during cardiopulmonary bypass, 40 patients having elective uncomplicated coronary surgery had retinal fluorescein angiograms 5 min before bypass was discontinued. Each patient also had 10 neuropsychological tests before and after surgery. A Harvey H1700 bubble oxygenator was used for 23 patients and a Cobe CML sheet membrane oxygenator was used for 17 patients. All 23 (100%) of patients in the bubble oxygenator group had retinal microvascular occlusions consistent with microembolism compared to 8/17 (47%) in the membrane oxygenator group (P less than 0.001). In those retinas with occlusions, the mean resultant area of non-perfusion was less in the membrane oxygenator group (0.11 mm2; n = 8) than in the bubble oxygenator group (0.29 mm2; P less than 0.01). Arterial PO2 levels during bypass were similar in both groups at moderate hypothermia, but the mean PaO2 during rewarming was higher in the bubble oxygenator group (27 kPa) than in the membrane group (13 kPa; P less than 0.001). Neuropsychological deficits were more common and more severe after bubble oxygenation than after membrane oxygenation, but in this small patient group, the difference was not statistically significant. We conclude that flat sheet membrane oxygenation during cardiopulmonary bypass may confer significant protection against cerebrovascular microembolism.
This case study reports on the neuropsychological consequences of prolonged circulatory arrest with hypothermia and barbiturate "protection". Measurements performed during surgery showed a prolonged absence of EEG. The neuropsychological assessment revealed a remarkable preservation of function, with the exception of delayed verbal memory and performance on the Trial Making Test. The findings are discussed in relation to the safe duration of circulatory arrest and the protection afforded the brain by hypothermia and barbiturate.
Two prospective trials suggested that teicoplanin was less effective in preventing Gram-positive wound infections after cardiac surgery than a combination of flucloxacillin and an aminoglycoside. The initial dose of 400 mg was associated with a subinhibitory concentration of teicoplanin in fat at the end of operation. In this study, the behaviour of a higher initial dose (12 mg/kg) was investigated in ten patients during coronary artery surgery. As in the earlier trials, a second dose (400 mg) was given after 24 h. The mean concentration at the end of cardiopulmonary bypass was 15 mg/l in serum, 6 mg/kg in fat and 9 mg/kg in skin, all in excess of the expected break-point for staphylococci (4 mg/l). The higher dose regimen might be more successful in surgical prophylaxis.
A series of patients undergoing coronary artery bypass surgery was studied prospectively to see if angiographic evidence of cerebrovascular disease proved predictive of the incidence of neuropsychological deficit 8 days or 8 weeks after surgery. In 47 patients, intravenous digital subtraction angiography was carried out preoperatively to assess the presence and severity of atheromatous changes in the carotid arteries; 51% had evidence of vessel wall disease and 17% had stenosis of at least one carotid artery in the neck, although only one patient had severe narrowing. Overall, 77% of these 47 patients showed a neuropsychological deficit as defined by a significantly reduced score in at least two of 10 tests administered 8 days after surgery. Eight weeks after surgery 36% still showed a deficit. The incidence of neuropsychological deficit was not significantly greater among those patients with angiographically visible carotid artery disease. The mechanism of surgery-related cognitive impairment is briefly discussed in the light of these findings.
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A total of 12 patients underwent surgical repair for thoracic aortic dissections with a technique which included cardiopulmonary bypass, profound hypothermia, high-dose thiopentone and circulatory arrest. Seven of nine early postoperative survivors made a complete recovery on clinical criteria. There were three perioperative deaths and there was one late postoperative death from chronic renal disease. There were no deaths among those operated on electively. Neuropsychological testing may help to define the consequences of circulatory arrest on higher function.
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