Effect of pentobarbital anesthesia on vulnerability to ventricular fibrillation

Ventricular fibrillation threshold (VFT), frequently determined in dogs during pentobarbital sodium anesthesia, usually is replaced by a single repetitive extrasystole threshold (SRET) or a multiple repetitive extrasystole threshold (MRET) determination in conscious animals and in the human being. In the present study SRET, MRET, and VFT were determined initially in 39 pentobarbital sodium-anesthetized dogs. One week later these three thresholds were redetermined during anesthesia in 13 of the 39 dogs (control group). In the remaining 26 dogs (experimental group), thresholds were redetermined while the dogs were conscious. Significant changes in threshold values occurred only in the experimental group for VFT (P < 0.001) and MRET (P < 0.02). The square of the linear correlation coefficient showed conscious state MRET to be a good predictor of conscious state VFT (R2 = 0.90). Conscious state SRET and anesthetized state VFT showed less predictiveness for the conscious VFT (R2 = 0.72 and 0.51, respectively). These data indicate that MRET may be preferable to SRET as an index of VFT. The SRET, MRET, and VFT determined during pentobarbital anesthesia may not accurately reflect the value of these parameters in the conscious animal.

Effect of submaximal exercise on vulnerability to fibrillation in the canine ventricle

The risk of instantaneous death due to ventricular fibrillation was compared in resting and exercised dogs. Three weeks before testing, all dogs had bipolar left ventricular stimulating electrodes implanted and a reversible snare was placed around the anterior descending coronary artery. The dogs were randomly assigned to either an exercise (13 dogs) or a control (12 dogs) group. We measured ventricular fibrillation thresholds (VFTs) in all dogs before and after inducing ischemia by tightening the snare while the dogs stood at rest. The next day, nonischemic and ischemic VFTs were redetermined for control dogs at rest and for the exercise group during a treadmill run. No statistically significant changes were noted within and between groups in nonischemic or in ischemic VFTs at rest. In five exercise dogs, spontaneous ventricular fibrillation occurred during the first 8 minutes of the ischemic run, For the eight other exercise dogs, running increased the mean drop in VFTs during coronary occlusion by 23% (p less than 0.01). These data suggest that moderate dynamic exercise may greatly enhance the risk of ventricular fibrillation and sudden death in the presence of myocardial ischemia. In the absence of ischemia, exercise does not appear to increase vulnerability to ventricular fibrillation.

A method for assessing volunteer bias and its application to a cardiovascular disease prevention progamme involving physical activity

Studies of chronic disease may require long-term observation of volunteer participants. This is a characteristic of investigations of primary or secondary prevention of cardiovascular disease by increased level of physical activity. Activation of sedentary, middle-aged, high risk men requires a substantial personal commitment on their part to a long-term programme. Because of self-selection, individuals who volunteer for such programmes cannot be assumed to be representative of the populations from which they come. To the best of our knowledge, there has been no systematic investigation of such self-selection based upon a study designed for that purpose. We found little consistent tendency for vouunteering behaviour to be associated with serum cholesterol, blood pressure, relative weight, level of activity at work, or Type A hehaviour variables.

Plant antitumor agents. XVI. 6alpha-Senecioyloxy-chaparrinone, a new antileukemic quassinoid from Simaba multiflora

Fractionation of Simaba multiflora A. Juss. guided by bioassay has resulted in the isolation of a new antileukemic quassinoid 6alpha-senecioyloxychaparrinone (2) and the previously reported quassinoid chaparrinone (3). The structure of the former has been established by spectral and chemical methods. Compound 2 has high anti-neoplastic activity against several mouse leukemia systems (P-388, L-1210 and in solid-tumor B-16 melanoma). This demonstrates for the first time that the presence of a C-15 ester function is not required for antineoplastic activity in the quassinoids.

Hemolytic disease of the newborn due to anti-Jsb

A case of hemolytic disease of the newborn due to anti-Jsb is described. The immunohematologic status of the mother and her offspring is presented.

Acute ethanol poisoning: a two-year study of deaths in North Carolina

A 24-month study of fatalities in North Carolina with high blood ethanol levels (300 mg/100 ml or over) revealed 502 cases with either acute alcoholism or the effects of this range of blood ethanol concentration having caused or contributed to death. This investigation reassessed the criteria for ethanol poisoning, including its cause and manner of death, and revealed recurrent patterns common to this syndrome. This inquiry also contrasted the frequency of ethanol poisoning in different areas of the country.

Chronic measurement of epidural pressure with an induction-powered oscillator transducer

An induction-powered oscillator transducer (IPOT) was designed for the chronic measurement of epidural pressure. The transducer was completely implantable so all pressure measurements were made through the intact skin. The IPOT had a linear pressure range from -50 to +200 cm H2O, was sensitive to 1 mm H2O and had a zero drift of less than 1 mm H2O/day under full load. Zero drift was minimized by using a hermetically-sealed metal bellows transducing element which was chemically treated to prevent corrosion and creep. The correlation between epidural pressure and intraventricular pressure was determined during the first 24 hours after implantation in six dogs. Epidural pressure was found to be a linear function of intraventricular fluid pressure. Epidural pressure and intraventricular pressure were essential equal provided the epidural wedge pressure was minimized by proper insertion of the transducer. The correlation between epidural pressure and intraventricular pressure was determined after chronic implantation in five dogs. Epidural pressure was a linear function of intraventricular pressure in the chronically implanted dogs, but epidural pressure was not equal to intraventricular pressure. After chronic implantation, the epidural pressure transducer was not responsive to changes in intraventricular pressure because of mechanical changes in the dura. The dura became stiff and non-compliant. Maximum correlation between epidural pressure and intraventricular fluid pressure in chronic implantations will depend on judicious material selection and mechanical design at the transducer-dura interface.

Ventricular premature beats in a population sample. Frequency and associations with coronary risk characteristics

In a large epidemiological survey, 10,880 men aged 35 to 57 years were screened for ectopic ventricular activity and estimated risk of future coronary heart disease death. A 2-minute lead I electrocardiogram (ECG) was recorded for each man, together with measurement of serum cholesterol, blood pressure, and the number of cigarettes currently smoked. Ventricular premature beats (VPB) occurred in 540 (4.96%) men; of these 459 (4.21%) were uniform, while complex forms were detected in only 7/1000 men. VPB occurring with a frequency of greater than or equal to 10 in the 2-min recording were also rare, occurring in 9/1000 men. No relation was found between the frequency of simple or complex VPB and estimated coronary risk status or between the prevalence of VPB and the individual risk factors of diastolic blood pressure, cholesterol, or cigarette smoking. There was, however, a strong positive association between VPB and the level of systolic blood pressure, and between VPB and increasing age. The lack of association between VPB and overall coronary risk status indicates that myocardial "ischemic" changes in high-risk men may not have progressed sufficiently to alter ventricular excitability or to increase the frequency of VPB.

Vascular access for hemodialysis by bovine graft arteriovenous fistulas

A technique has been developed for vascular access in chronic dialysis using bovine graft arteriovenous fistulas in the forearm. Indications for use of bovine arteriovenous fistulas are failures of arteriovenous shunts and standard arteriovenous fistulas at the wrist or as a primary procedure in the event that arterial inflow or venous outflow are inadequate. Choice of either a straight or loop graft is dictated by the vascular anatomy. Loop grafts, orginating from the brachial artery, should be used for inflow problems; straight grafts, originating from an artery at the wrist, should be used for outflow problems. Results have been excellent in this series of 39 grafts in 36 patients observed from two months to one year with a follow-up average of six months. Ninety per cent of the grafts continue to function or functioned until successful transplantation or the death of the patient. Advantages of bovine graft arteriovenous fistulas compared with other fistulas include ease of access, high flows and decreased incidence of hematomas. The major complication has been thrombosis, and this incidence, most likely, can be decreased by more careful selection of the type of graft placement according to the vascular anatomy.

Hemodynamic predictors of myocardial oxygen consumption during static and dynamic exercise

Hemodynamic predictors of myocardial oxygen consumption (MVO 2 ) during static and dynamic exercise were examined in ten normal subjects. Studies were done under the following circumstances: 1) during upright bicycle exercise at an average heart rate of 147 beats/min, 2) during static exercise with an isometric load in the left hand equal to 17% of the maximal voluntary contraction (MVC), and 3) during combined dynamic exercise (average heart rate 147 beats/min) and static exercise using 17% MVC of the left hand. Mean myocardial blood flow (MBF) was 181 ml/100 gm LV/min during dynamic exercise, 98 ml/100 gm LV/min during static exercise, and 201 ml/100 gm LV/min during combined static and dynamic exercise. Addition of a static load to the dynamic load resulted in a higher blood pressure (average 12 mm Hg), MVO 2 and MBF than during dynamic exercise alone. MVO 2 correlated best with products of heart rate and blood pressure regardless of whether the blood pressure was obtained by a central aortic catheter ( r = 0.88) or by a blood pressure cuff ( r = 0.85).

When the current data were combined with previous data, 82 determinations of MVO 2 and MBF in 29 normal subjects during several levels of upright exercise were available for analysis. Forty-four determinations were done during dynamic upright exercise, 18 during exercise after propranolol, ten during combined static and dynamic work, and ten during static work alone. MVO 2 correlated best with the product of heart rate and blood pressure ( r = 0.86). Heart rate alone correlated better with MVO 2 ( r = 0.82) than did the tension time index ( r = 0.65) or the product of systolic blood pressure, heart rate, and ejection time ( r = 0.68). The readily measured variables of heart rate and of heart rate x blood pressure correlated well with MVO 2 in normal young men during exercise under a wide variety of circumstances.