Ischemic preconditioning suppresses the noradrenaline turnover in the rat heart

OBJECTIVE

The mechanism by which ischemic preconditioning protects the heart is presumed to be related to the reduction of energy consumption during a subsequent myocardial infarction. Since the sympathetic nervous system enhances cardiac function and energy consumption, we investigated the relation between ischemic preconditioning and the turnover rate of noradrenaline (NA) in the rat heart.

METHODS

The effect of 3 cycles of 5-min occlusions of the rat left coronary artery on changes in arterial blood pressure and heart rate provoked by a subsequent 30 min of ischemia were examined until 60 min after reperfusion. The effect of 3 cycles of occlusions on the infarct size was also evaluated 60 min after reperfusion by comparing the infarcted area with the area at risk in these animals (6 per preconditioned and sham-operated group). The tissue concentration of NA during sustained ischemia was determined in the left ventricle, the intraventricular septum, and the right ventricle in the preconditioned and sham-operated groups. Changes in the turnover rate of NA after 3 cycles of occlusions were also evaluated by assessing the alpha-methyl-p-tyrosine-induced depletion of NA (n = 7 per group).

RESULTS

A series of transient occlusions reduced the infarct size 60 min after a sustained ischemia for 30 min. Arterial pressure and heart rate were not affected. The concentration of NA was decreased in the left ventricle 60 min after the onset of sustained ischemia in both the preconditioned and sham-operated groups. The treatment with alpha-methyl-p-tyrosine decreased the NA concentration in all regions of the heart in the sham-operated group after 60 min. However, the treatment with alpha-methyl-p-tyrosine did not deplete the NA concentration in both the occluded and nonoccluded regions in the preconditioned group.

CONCLUSIONS

Transient ischemia ameliorated the heart injury induced by a subsequent sustained ischemia, as assessed histologically. The activity of the sympathetic nervous system in all regions of the heart was reduced by transient ischemia in the left coronary vascular bed. These findings suggest that the inhibition of the sympathetic nervous system by the treatment of ischemic preconditioning takes part in the cardiac protection.

Hypothermia increases the threshold for ischemic preconditioning

OBJECTIVES

Both hypothermia and ischemic preconditioning are known to provide tolerance to myocardial ischemia and reperfusion. The aim of this study was to determine whether hypothermia during the ischemic preconditioning period attenuates the protective effect of ischemic preconditioning.

METHODS

Experiments were performed in buffer-perfused isolated rabbit hearts. All hearts underwent 45 minutes of regional ischemia, followed by 2 hours of reperfusion. Ischemic preconditioning was elicited by either one or four periods of 5 minutes of regional ischemia. Hypothermia (25 degrees C) was induced beginning either 20 or 50 minutes before the 45-minute period of regional ischemia; normothermia (38 degrees C) was restored 10 minutes before the 45-minute period of regional ischemia. Except for the hypothermic periods noted, hearts were maintained at 38 degrees C.

RESULTS

Normothermic ischemic preconditioning with either one or four cycles of 5 minutes of coronary occlusion resulted in a profound reduction of infarct size (58% reduction with one cycle, p < 0.05; 95% reduction with four cycles, p < 0.01). Hypothermic ischemic preconditioning with one cycle of 5-minute coronary occlusion resulted in no reduction of infarct size but hypothermic ischemic preconditioning with four cycles of 5-minute coronary occlusions resulted in a 94% reduction of infarct size (p < 0.01). Myocardial glycogen and lactate levels were maintained near control levels during hypothermic ischemia.

CONCLUSIONS

From these data we conclude that hypothermia during the preconditioning period increases the threshold for eliciting the infarct limitation of ischemic preconditioning.

[Percutaneous drainage of a bulla with tuberculous infection in a patient]

A 63-year-old man complaining of low grade fever and dry cough was admitted to our hospital. Chest X-ray showed infiltrative shadows and a bulla with a fluid level in the left upper lung field. Bacteriological examination of sputum and bronchoalveolar lavage fluid did not yield any diagnostic results. Percutaneous aspiration of the bulla under fluoroscopy was performed. Bulla with tuberculous infection was considered because a high ADA level was detected in the fluid of the bulla. A culture of the bulla fluid was positive for mycobacterium tuberculosis (TB), which was sensitive to all anti-mycobacterial drugs. The fluid in the bulla gradually increased, and occupied the entire space of the bulla three months later. Percutaneous aspiration of the bulla was performed again and a fluid smear was positive for TB. It was thought that systemic administration of anti-mycobacterial drugs had been ineffective, so percutaneous drainage and subsequent injection of anti-mycobacterial drugs into the bulla was performed. The fluid in the bulla subsequently disappeared and the bulla shrank gradually. Percutaneous drainage of a bulla with tuberculous infection should be considered in those who do not respond to medical management.

[Clinical characteristics of pulmonary embolism without definitive predisposing factors]

Patients with pulmonary embolism may have no definitive predisposing factors for thrombi. The clinical entity of chronic pulmonary embolism is also uncertain. This study clarified the clinical characteristics of pulmonary embolism without definitive predisposing factors. During the last 10 years, 36 consecutive patients were diagnosed as having pulmonary embolism (mean age 61 years, female 75%). Twenty-four patients (67%) had definitive predisposing factors ("definitive" group). Patients without definitive predisposing factors had the following characteristics. The onset of symptoms was out-hospital and insidious. The main symptom was exertional dyspnea without acute episode compatible with an embolism. In four patients (33%) there was a delay of over 2 years form the onset of symptoms to the diagnosis. Three patients had been treated for depression. Thrombolytic therapy caused an inadequate fall in mean pulmonary artery pressure from 41 +/- 11 to 24 +/- 8 mmHg and in three patients it remained over 30 mmHg. Deep vein thrombosis were found in four of nine patients in whom venography were performed 10 days after thrombolytic therapy, but only one patient showed thrombus in the "definitive" group. During the convalescent stage, all patients were treated with prophylactic warfarin. Home oxygen therapy was indicated in three patients and an inferior vena caval filter was implanted in two patients. One third of patients with pulmonary embolism in our institute had no definitive predisposing factors. In these patients, even with thrombolytic therapy, recovery of pulmonary hypertension was often insufficient and deep vein thrombosis persisted. Clinicians should be aware of this disease to avoid undue delay in its diagnosis.

[Two cases of tubercle bacilli infected pulmonary bulla]

Two cases of tubercle bacilli infected bulla are reported. Case 1; A 78-year-old man visited our hospital complaining of fever and chest pain. The chest radiograph revealed the bulla with air fluid level in the left upper lung field. Mycobacterium tuberculosis was detected in the fluid obtained by percutaneous lung aspiration. He was treated with anti-mycobacterial drugs and showed improvement. Case 2; A 66-year-old man visited our hospital complaining of fever, chest pain and dry cough. The chest radiograph revealed the bulla with air fluid level in the left upper lung field. A diagnosis of tubercle bacilli infected bulla was considered because of high level of ADA in the fluid obtained by percutaneous lung aspiration, and anti-mycobacterial drugs were administered. His symptoms were improved and the frequent chest radiograph showed gradual absorption of the fluid. It is suggested that ADA and bacteriological examinations of the fluid obtained by percutaneous lung aspiration are useful for early diagnosis of tubercle bacilli infected bulla.

[Predictors for the massive thrombi occurring in the right coronary artery related to acute myocardial infarction]

Acute myocardial infarction (AMI) related to the right coronary artery (RCA) is associated with a lower reperfusion rate and higher reocclusion rate in the acute phase than AMI related to the left coronary artery. The greater susceptibility of the RCA to development of large thrombi makes successful reperfusion more difficult to achieve. This study investigated predictive factors for massive thrombus in the RCA before the selection of the treatment to achieve better rates of reperfusion. We classified 51 patients with AMI related to RCA into the massive (linear intraluminal radiolucency > 3 cm) thrombus group (9 patients) and the non-massive thrombus group (42 patients). 1) HISTORY: Patients in the massive thrombus group had a greater incidence of hypertension than the non-massive thrombus group, with more left ventricular hypertrophy (p < 0.05). There were no significant differences in other coronary risk factors. 2) RCA morphology: The maximum RCA diameter was significantly greater in the massive thrombus group than that in the non-massive thrombus group [proximal to the right ventricular branch, 4.2 vs 3.2 mm (median); distal to the right ventricular branch, 4.2 vs 3.4 mm, p < 0.05]. 3) Conditions of onset: The elapsed time was significantly longer in the massive thrombus group (15 hours) than that in the non-massive thrombus group (2.5 hours, p < 0.05). More massive thrombus cases were observed in summer (p < 0.05), but there was no evident correlation between massive thrombus formation and the onset time of day, weather, Hct and coagulation factor at the onset, left ventricular ejection fraction or left ventricular end-diastolic pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

[Estimation of respiratory functions by analysis of expired gas and blood gas during artificial ventilation and general anesthesia]

One-hundred and seven patients undergoing elective surgery were studied to analyze the correlations between preoperative spirometric values and respiratory parameters during general anesthesia. They were grouped according to 3 criterions; preoperative %VC of less than 80%, FEV1.0% of less than 70%, V50/V25 exceeding 4.0. Following the induction of general anesthesia and of mechanical ventilation, expiratory flow (VE), FECO2, PaCO2 and PaO2 were measured to calculate respiratory parameters including VCO2-SR, VD/VT-Bohr, VD/VT-physiological (phys), a-ETDCO2, Volume Pressure Index (VPI) and A-aDO2. Six respiratory parameters were compared between the groups, and correlations between preoperative spirometric values were studied. Those with lower %VC had higher values in VCO2-SR and in VPI, and those with lower FEV1.0% had higher values in VCO2-SR, in VD/VT-phys and in a-ETDCO2. Significant correlations were also observed between these parameters. Preoperative V50/V25 and A-aDO2 during general anesthesia did not correlate with any of the parameters studied. We conclude that VCO2-SR, VD/VT-phys, a-ETDCO2 and VPI during general anesthesia are useful to detect the patients with restrictive and/or obstructive lung dysfunction, although they are not sensitive enough to detect those with small airway disease.

Intraaortic balloon pumping as the postangioplasty strategy in acute myocardial infarction

To assess the usefulness of intraaortic balloon pumping (IABP) in acute myocardial infarction (AMI), 114 patients with anterior AMI undergoing emergency percutaneous transluminal coronary angioplasty (PTCA) for total occlusion of the left anterior descending artery were studied. After successful PTCA 66 patients were treated with conventional therapy (group I), and 48 patients were treated with IABP for 25 +/- 8 hours (group II). The reocclusion rate was significantly lower in group II (2.4% vs 17.7% p less than 0.05). An increase in ejection fraction in group II compared with group I was marginally significant (4.5 +/- 12.2% vs 9.2 +/- 13.0%, p = 0.08). Vascular complications occurred in two patients, but there were no deaths from IABP. These results suggest that after successful PTCA for acute myocardial infarction, IABP prevents reocclusion and may add strength to reperfusion in the improvement of left ventricular function.

[A clinical study of the relation between time to reperfusion and infarct size]

Observations made in animal models of reperfusion in acute myocardial infarction have shown that early reperfusion results in myocardial salvage. But the relation between the time of reperfusion and myocardial salvage is not clear in human patients. If earlier reperfusion provides smaller infarct size, reperfusion therapy initiated in the first 1 hour should be the most beneficial. In this study, we compared the results of therapy initiated in the first 1 hour (group A, n = 19) with treatment started 1 to 24 hours after the onset of chest pain (group B, n = 652). The infarct location, development of collateral vessels, number of diseased vessels and reperfusion rate of thrombolysis in the two groups didn't differ. There was a statistically insignificant trend towards total occlusion of the infarct artery in group A (89.5% vs 69.7%, p less than 0.1). Peak CPK and changes in left ventricular ejection fraction (delta EF) were assessed in patients with total occlusion of the left anterior descending artery and successful reperfusion (n = 8 in group A, n = 120 in group B). There was no difference in peak CPK (3281 +/- 2192Iu/l vs 3490 +/- 1811Iu/l) and delta EF (6.3 +/- 17.1% vs 5.8 +/- 11.9%). These findings suggest that there is no relation between the time of reperfusion and myocardial salvage in human patients.

Evaluation of preload reserve during isometric exercise testing in patients with old myocardial infarction: Doppler echocardiographic study

To estimate the preload reserve in response to an increase in afterload in patients with old myocardial infarction, the relation between the Doppler echocardiographic inflow velocity pattern and left ventricular end-diastolic pressure was investigated during isometric handgrip exercise testing. The study population consisted of 16 normal subjects and 40 patients with old myocardial infarction. The 40 patients were subdivided into two groups according to left ventricular end-diastolic pressure at rest: group I (22 patients), less than 18 mm Hg; group II (18 patients), 18 mm Hg or more. At rest, the ratio of peak velocity in atrial contraction phase to peak velocity in early diastolic filling phase (A/E) was significantly higher in the patients with old myocardial infarction than in normal subjects; values in the two subgroups of myocardial infarction did not differ significantly. The A/E ratio and left ventricular end-diastolic pressure increased significantly during exercise in group I. Conversely, the change in left ventricular end-diastolic pressure during exercise in group II was significantly greater than that in group I, and was associated with a decrease in the A/E ratio. Thus, an atrial compensatory mechanism operated effectively in response to the increase in afterload in patients with a normal left ventricular filling pressure, whereas this compensatory mechanism deteriorated in patients with elevated left ventricular filling pressure due to a limited preload reserve.

[Distinctive response of coronary artery compared acute myocardial infarction with angina pectoris associated with angioplasty]

There has been much controversy over the mechanism of successful percutaneous transluminal coronary angioplasty (PTCA). To examine clinical and angiographic factors that might be related to a successful PTCA, we assessed 224 branches treated with emergent or elective angioplasty in evolving acute myocardial infarction (AMI) and angina pectoris (AP). The patients were divided into three groups; group 1 (G1): AP (n = 113), group 2 (G2): AMI with complete obstruction of infarct-related artery (IRA) (n = 79), group 3 (G3): AMI with incomplete obstruction of IRA (n = 32). The morphology of stenotic lesion was classified into smooth type and irregular type. The former shows concentric smooth border, the latter shows eccentric irregular border and multiple irregular border according to the Ambrose classification. Regarding the severity of the stenosis immediately after successful PTCA, there was no significant differences between G2 and G3, however in G1 it was significantly higher than in other groups (G1 vs G2 vs G3, 56% vs 81% vs 78%, p less than 0.001). Irregular type at stenotic lesions before PTCA were present in 72 of 113 branches in G1 vs 60 of 69 in G2 and G3. Regarding the incidence of acute coronary obstruction during PTCA, there was no significant differences between G1 and G2. However, in G3 it was significantly higher than in other groups (G1 vs G2 vs G3, 8% vs 9% vs 38%, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

[The effects of post-ischemic delayed hypoperfusion on the process of recovery of brain function]

The author studied the effect of post-ischemic delayed hypoperfusion on the recovery process of brain function after complete cerebral ischemia in a dog model in which the existence of PDH had been shown previously by the author, using nicardipine as a tool to ameliorate the PDH, the effect of the drug also having been demonstrated by the author in the previous study. Twenty-four dogs underwent 15 min complete cerebral ischemia using aortic clamping method with aorto-atrial bypass formation. EEG (for 16 h) and brain functions, awakening, cranial nerve reflexes, motor functions, behaviors and respiratory functions were evaluated using neurological deficit score (NDS) periodically (for 120 h) after ischemia. Eight dogs (1 microgram group) received nicardipine 1 microgram.kg-1.min-1 for 4 h following 10 micrograms bolus iv injection 5 min after declamping of aorta, another 8 dogs (2 micrograms group) received 10 micrograms + 2 micrograms.kg-1.min-1 nicardipine in the same manner as group 1, and the remaining 8 served as controls. In 1 microgram group the first appearance of EEG activities after ischemia was earlier than control group (41 +/- 11 vs 80 +/- 33 min), and also the appearance rate of alpha waves was higher than the controls (87.5% vs 25%) 16 h after declamping of aorta. NDS scores for awakening, behavior, and respiratory functions were better in 1 microgram than the controls between 36 and 48 h post-ischemia, but there were no significant changes in the scores between the two groups 120 h after ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

[Cerebral hemodynamics of post-ischemic delayed hypoperfusion (PDH) and the effects of nicardipine on the PDH]

Post-ischemic delayed cerebral hypoperfusion (PDH) is considered to be one of the most critical factors limiting brain recovery after cerebral ischemia. This experiment was designed to determine the characteristics of PDH and the effects of nicardipine on the PDH. Twenty-four dogs underwent complete cerebral ischemia for 15 min using aortic clamping method with aorto-atrial bypass formation, and cerebral cortical blood flow (c-CBF), brain stem blood flow (s-CBF), intracranial pressure (ICP), and perfusion pressure (PP) were measured for 48h. Eight dogs (1 microgram group) received nicardipine 1 microgram.kg-1.min-1 for 4 h following 10 micrograms bolus iv injection 5 min after declamping of aorta. Another 8 dogs (2 micrograms group) received 10 micrograms + 2 micrograms.kg-1.min-1 nicardipine in the same manner as in group 1. The remaining 8 served as controls. In the control group c-CBF and s-CBF decreased to 60% and 55% of pre-ischemic values, respectively 1 hour after declamping of aorta, and returned to pre-ischemic values 10 and 6 h later, respectively, in spite of no significant changes in PP's. 1 microgram group and 2 micrograms group maintained pre-ischemic CBF value throughout the experimental period, and the values were significantly higher than in control group between 1st and 5th h post-ischemia. There were no significant differences in ICP's among the 3 groups throughout the experiment. In conclusion, PDH appears to be a phenomenon always accompanying transient complete cerebral ischemia, and it is assumed to be caused by constriction of cerebral vessels. Nicardipine improved PDH, indicating that the underlying mechanism of PDH must be related to a disorder in Ca2+ metabolism of cerebral vessels after ischemia.

[Secundum atrial septal defect in two families]

Two families having secundum atrial septal defect (ASD) were reported. In one family, a 31-year-old male and his 60-year-old mother had secundum ASD without PR prolongation. His 38-year-old brother was diagnosed as having ASD. His grandmother, who had died at the age of 51, was suspected of having congenital heart disease. From early childhood she was noticed to have heart murmur. It was suspected that this was a case of familial ASD without PR prolongation, because it was consistent with the dominant trait of the defect. In the other family, a 16-year-old female had secundum ASD and her 18-year-old brother was also suspected of having ASD. Her 25-year-old brother had been operated on for tetralogy of Fallot, and her sister had died of an unknown congenital heart disease. All of these family members had mental retardation. Her 22-year-old brother was suspected of having a congenital heart disease, because of heart murmur from his early childhood. The parents, who were blood relations (cousins), had neither heart disease nor mental retardation. The children of this family were considered to be cases of congenital heart disease with ASD, associated with mental retardation. It was also suspected that the cause of the defect was a deleterious autosomal recessive gene.

[Clinical features of patients with spontaneous recanalization of the infarct-related artery during evolving acute myocardial infarction]

The clinical features of 124 patients with incompletely obstructed infarct-related arteries during the early stages of myocardial infarction (Group 1) were compared with those of 212 patients having completely occluded coronary arteries (Group 2). Coronary angiography was performed within 12 hours after onset of symptoms in all cases. Patients treated with emergency coronary angioplasty were excluded from the study. Thrombolytic therapy, performed in both groups whenever intracoronary thrombi were detected, was successful in 61% of Group 2. Results were as follows: 1. In Group 1, three-vessel disease was observed more frequently than one-vessel disease (49 vs 27%, p less than 0.005). 2. The peak level of CPK was higher in Group 2 (p less than 0.001), and left ventricular ejection fraction was higher in Group 1 (66 +/- 16 vs 56 +/- 14%, p less than 0.01). 3. Either significant ST elevation or the Q wave was more commonly absent in Group 1 (31 vs 12%, p less than 0.01; 49 vs 12%, p less than 0.001). 4. Improvement of ejection fraction was observed in Group 1, but not in Group 2 even if the infarct-related artery was recanalized within six hours. 5. Extension of an infarct area was more common in Group 1 compared to Group 2 which was successfully treated with thrombolytic therapy (12 vs 3.9%, p less than 0.05). 6. The most important cause of death was extension of an infarct area in Group 1 and pump failure in Group 2, though hospital mortality rates were similar in both groups. It was concluded that patients with myocardial infarction having incompletely obstructed infarct-related coronary arteries have better left ventricular function and higher rates of non-Q myocardial infarction compared with those who had completely obstructed coronary arteries. However, extensions of infarcted areas commonly occur in these patients.

[Effect of isometric hand-grip exercise on left ventricular diastolic filling in patients with effort angina: a pulsed Doppler echocardiographic study]

To detect myocardial ischemia and to estimate cardiac reserve in patients with effort angina pectoris without history of myocardial infarction, left ventricular diastolic filling was measured using Doppler echocardiography during isometric handgrip exercise. Nineteen patients with effort angina pectoris undergoing coronary angiography and 16 normal subjects were studied. The angina patients were categorized in two groups: 12 with single vessel disease (SVD) and seven with multiple vessel disease (MVD). Fifty percent maximum voluntary contraction isometric handgrip exercise was performed for two minutes. 1. The resting A/R in the angina group was significantly greater than that of the normal subjects (SVD: 1.20 +/- 0.24, MVD: 1.21 +/- 0.27, normal 0.85 +/- 0.10) (p less than 0.001). However, the values of many cases in these three groups overlapped. 2. In SVD, the A/R increased significantly during isometric handgrip exercise (1.20 +/- 0.24 to 1.96 +/- 0.66: p less than 0.001). The delta A/R (0.76 +/- 0.15) was significantly greater than that of patients in other groups (MVD: 0.10 +/- 0.13, normal: 0.09 +/- 0.01) (p less than 0.001). Consequently, the A/R after exercise clearly distinguished the SVD from the normal subjects. 3. In MVD, the A/R did not change significantly during exercise (1.21 +/- 0.27 to 1.31 +/- 0.41), and there were no significant differences in delta A/R as compared to the normal subjects (p less than 0.01). The A/R decreased during exercise in three of the seven patients, and this was markedly different from that of the normal subjects. These findings suggest that assessment of changes in left ventricular diastolic filling during isometric handgrip exercise is useful in detecting myocardial ischemia and in estimating cardiac reserve in patients with effort angina pectoris.

Acute myocardial infarction in the elderly

Cardiovascular disease is the most common cause of death in the elderly. In fact, the cardiovascular disease is the number one cause of death in women and the number two cause in men of 65 years or over in Japan. We studied the clinical characteristics and significances of acute myocardial infarction as they relate to the aged.

A new model for total cerebral ischemia in dogs

We have developed a new method producing total cerebral ischemia (TCI) in dogs; clamping ascending aorta with aorto-atrial bypass formation. Clamping ascending aorta provides TCI, the duration of which can be controlled up to the periods of 10 min. Beyond this interval, it is difficult to maintain TCI because of heart failure from high afterload. Blood outflow from left ventricle is completely obstructed except for coronary circulation which is small relative to the blood volume expelled from left ventricle, even if venous return to the heart is reduced. Aorto-atrial bypass formation during aortic clamping provides two distinctive advantages. First, adjusting aortic pressure in an appropriate level low enough not to overload myocardium but still high enough to maintain sufficient coronary blood flow is possible by regulating the blood flow through the bypass tubing, and secondly drug administration and blood volume control is possible through the tubing. These result in better preservation of myocardium, enabling longer TCI and longer survivals after TCI. We were successful in having up to 18 min of TCI with this method. Seventy-five percent of dogs of 12 min TCI and 40% of 15 min TCI survived 7 days, limit of experiment, after TCI, but no dogs of 18 min TCI survived for more than 3 days.

Cerebral blood flow during conventional, new and open-chest cardio-pulmonary resuscitation in dogs

The following parameters were monitored simultaneously in 15 dogs, in order to evaluate the efficacy of conventional CPR (C-CPR), new CPR (N-CPR), and open-chest CPR (O-CPR) on cerebral perfusion: arterial blood pressure (BP), central venous pressure (CVP), intrathoracic airway pressure, blood flow in carotid artery, intracranial pressure (ICP), sagittal sinus blood flow (sinus BF) and pressure (sinus P), and blood flow in cerebral cortex (cortical BF). The sinus blood flow was measured by the direct-method and with a cannulating electromagnetic flowmeter. The cortical blood flow was measured with a termocouple tissue flowmeter. Intracranial pressure was obtained by measuring subarachnoid cerebrospinal fluid pressure. Ventricular fibrillation was induced electrically. Chest compression and ventilation were always done manually in all cardiopulmonary resuscitation. The mean blood pressures during C-CPR, N-CPR and O-CPR were 52, 68 and 95 mmHg, respectively, and mean carotid blood flows per stroke were 36, 71 and 131% of the control values, respectively. The intracranial pressures were 30, 42 and 36 mmHg, respectively, giving the calculated cerebral perfusion pressures (BP-ICP) of 22, 27 and 60 mmHg, respectively. This should have been reflected in cerebral blood flow. Sinus blood flows/min were 18, 18 and 42%, and sinus blood flows per stroke were 55, 45 and 127% of control values, respectively; the differences between C-CPR and N-CPR were not significant. This was also true for cortical blood flow. From this we conclude that, firstly, N-CPR is not significantly better than C-CPR in cerebral perfusion because of its accompanying high intracranial pressure, secondly, O-CPR is far superior to the other two methods in respect of cerebral perfusion.