Anaesthetic management of phaeochromocytoma associated with tricuspid atresia

The anaesthetic management of a patient with phaeochromocytoma, tricuspid atresia and pulmonary vascular stenosis is reported. The patient received no preoperative preparation with adrenergic blockers. Anaesthesia was induced and maintained with fentanyl, diazepam and sevoflurane. Intraoperative blood pressure was controlled with sodium nitroprusside, sevoflurane, phentolamine, and propranolol. For hypotension after resection of the tumour norepinephrine was required. This patient did not have a systemic to pulmonary shunt procedure performed, so the maintenance of pulmonary blood flow in the presence of haemodynamic instability during operation for phaeochromocytoma was a major concern. Monitoring of oxyhaemoglobin saturation (SpO2) with a pulse oximeter was considered to be useful because SpO2 may reflect pulmonary flow. During serious haemodynamic disturbances due to the manipulation of the tumour, the heart rate was inversely correlated with SpO2, but the relationship between mean arterial pressure and SpO2 was weak. Therefore, control of heart rate appeared to be more important than control of blood pressure in this case.

Dexmedetomidine prevents epinephrine-induced arrhythmias through stimulation of central alpha 2 adrenoceptors in halothane-anesthetized dogs

Since alpha 2-adrenergic agonists have important effects on the adrenergic system that have recently been applied to the anesthetic setting, we investigated the effect of stimulation of alpha 2 adrenoceptors on epinephrine-induced arrhythmias in halothane-anesthetized dogs. The arrhythmogenic threshold for epinephrine was determined during halothane anesthesia in the presence of dexmedetomidine, a selective alpha 2 agonist, and L-medetomidine, a stereoisomer of medetomidine that lacks alpha 2-agonist activity. Dexmedetomidine increased the arrhythmogenic threshold for epinephrine in a dose-dependent manner during halothane anesthesia. At the highest dose of dexmedetomidine, 0.5 microgram.kg-1.min-1, there was a three-fold increase in both the arrhythmogenic dose of epinephrine and the plasma epinephrine concentration that was reached at this dose. On the other hand, L-medetomidine over the same dose range did not effect the arrhythmogenic dose of epinephrine. Atipamezole, a central alpha 2 antagonist that crossed the blood-brain barrier, blocked the antiarrhythmic action of dexmedetomidine. L-659,066 a peripheral alpha 2 antagonist that does not penetrate the blood-brain barrier, did not affect the antiarrhythmic action of dexmedetomidine. Thus, dexmedetomidine's antiarrhythmic effect on epinephrine-induced arrhythmias during halothane anesthesia appears to be mediated at least in part by stimulation of central alpha 2 adrenoceptors.

[The effects of thromboxane receptor antagonist on hemodynamic responses after neutralization of heparin by protamine]

In a double blind test, the effects of ONO 3708, thromboxane A2 (TXA2) receptor antagonist, on hemodynamic responses after neutralization of heparin by protamine, were evaluated in 19 patients undergoing coronary artery bypass graft. Severe circulatory disturbances were not observed in all patients after intravenous administration of protamine (3 mg.kg-1) over 5 minutes, and in particular ONO 3708 (2.5 micrograms.kg-1.min-1 given with continuous infusion) group (n = 10) showed no deleterious hemodynamic responses to protamine. On the other hand, in placebo group (n = 9) the mean pulmonary artery pressure (mPAP) and the mean pulmonary/systemic artery pressure ratio (Pp/Ps) increased significantly, immediately following protamine administration, compared with the baseline values and ONO 3708 group. The results suggest that pulmonary hypertension after protamine is associated with TXA2 release and that ONO 3708 is useful to avoid this reaction.

Roles of beta 1- and beta 2-adrenoceptors in the mechanism of halothane myocardial sensitization in dogs

The authors investigated the comparative roles of beta 1- and beta 2-adrenoceptors in myocardial sensitization by halothane in dogs. The arrhythmogenic dose (AD) of isoproterenol was determined in the presence of various doses of phenylephrine during halothane anesthesia in dogs, and the influences of 1-metoprolol (beta 1-antagonist) and ICI-118,551 (beta 2-antagonist) on the AD were examined. In the presence of 1-metoprolol, the AD of isoproterenol was significantly greater than the control, but in the presence of ICI-118,551, the AD of isoproterenol was lower. Blood pressure during the arrhythmias was higher in the presence of ICI-118,551 than that in controls. In addition, the AD of ritodrine (beta 2-agonist) was also determined at various doses of phenylephrine. The interaction between phenylephrine and ritodrine in inducing arrhythmias showed hyperbolic isoboles. However, 1-metoprolol completely inhibited the occurrence of arrhythmias induced by ritodrine and phenylephrine. The results suggest that myocardial beta 1-adrenoceptors play an essential role in the genesis of arrhythmias during halothane anesthesia in dogs, whereas beta 2-adrenoceptors do not.

[Response to CO2 and autoregulation of cortical cerebral blood flow during isoflurane anesthesia]

Response to CO2 and autoregulation of cortical cerebral blood flow (CBF) during isoflurane anesthesia were studied in 10 patients undergoing neurosurgery. The patients were anesthetized with 0.5 to 1.2% end-tidal isoflurane and 66% nitrous oxide in oxygen. The CBF was measured by thermal diffusion using a flow probe with a Peltier stack. PaCO2 was controlled to produce hypocarbia, normocarbia and hypercarbia by changing tidal volume and respiratory rate. Arterial blood pressure was altered. Hypotension was achieved by intravenous infusion of trimetaphan and hypertension was induced by intravenous administration of metaraminol. During isoflurane anesthesia the response to CO2 of CBF was kept at PaCO2 between 27.8 and 53.9 mmHg. The following relationship was obtained. CBF = 2.54 x PaCO2-53.0, r = 0.59, n = 131 The autoregulation of CBF was evaluated in 7 patients, and in 2 patients, the autoregulation of CBF was abolished.

[Impaired B lymphocyte function during open heart surgery]

Sequential in vitro lymphocyte function tests in 13 patients undergoing cardiac operation were performed to study B lymphocyte function following operation. Lymphocytes were stimulated with phytohemagglutinin (PHA), pokeweed mitogen (PWM) and Staphylococcus aureus Cowan 1 (SAC). Mitogen responses were measured by 3H-labeled thymidine incorporation. The SAC responses were significantly depressed following operation. Immunoglobulin secreting cells were measured by protein A plaque forming cell assay. The numbers of immunoglobulin secreting cells induced by PWM or SAC decreased remarkably at least as long as 3 day after the operation. The percentage of circulating B lymphocytes increased significantly postoperatively. This indicates that the B lymphocytes remaining after the operation were functionally impaired.

[Monitoring system of cerebral blood flow and cerebral metabolism. Part II. Relationship between internal jugular O2 tention and cerebral blood flow (author's transl)]

Changes of PjO2 values of internal jugular vein were monitored in patients with various types of cerebrovascular disease. The significance of PjO2 monitoring was evaluated. 1) Control value of PjO2 in thirteen normal control cases was 36.7 +/- 1.9 mmHg (mean +/- SD). 2) Limit of brain hypoxia showing no neurological sign and symptom in patients with occlusive cerebrovascular disease was studied by the stepwise reduction of arterial blood pressure, using drip infusion of trymetaphan camsylate, under the careful monitoring of signs and symptoms and monitoring of PjO2 and EEG. Appearance of signs and symptoms of brain hypoxia were checked by yawning and EEG slowing. At the time of the appearance of brain hypoxia PjO2 was 28.6 +/- 3.2 mmHg. 3) CO2 reactivity of CBF was studied in patients with occlusive cerebrovascular disease. Relation between PaCO2 and PjO2 was as follows; PjO2 = 0.68 . PaCO2 + 7.55 4) Within 24 hours after the onset of stroke, ipsilateral PjO2 of the cases with disturbance of consciousness was lower than that of the cases without disturbance of consciousness, which might indicate the significant decrease of CBF in the former cases. During 3rd to 7th day after the onset the cases with disturbance of consciousness showed the significant elevation of PjO2, which might indicate the reduction of cerebral metabolism. 5) The elevation of ipsilateral PjO2 were well correlated to the degree of hemispheric brain swelling. 6) During general convulsion, high level of PjO2 values were observed. 7) PjO2 values were inversely correlated to the hemoglobin values after blood transfusion, which was mainly due to the decrease of CBF by high content of hemoglobin.