A long-term stable normothermic cardiopulmonary bypass model in neonatal swine.

BACKGROUND: An appropriate animal model of cardiopulmonary bypass (CPB) is critical in order to study the morbidity and mortality in newborn children undergoing long-term cardiac surgery. Since this has been reported to be technically difficult, this paper describes a neonatal porcine CPB model (3 days old, n = 18) for up to 8 h to study long-term bypass. METHODS: After anesthesia, neonates had arterial/venous monitoring lines inserted, they were heparinized (300 IU/kg), the aorta was cannulated for arterial retroperfusion, and a two-stage venous drainage catheter was placed in the right atrium. A Medtronic Minimax Plus oxygenator and the bypass circuit were primed with donor blood and CPB was instituted. RESULTS: Line and mean arterial pressures were kept at 147.7 +/- 73 and 62.7 +/- 9 mm Hg, respectively. Myocardial (38.1 +/- 1.0 degrees C) and rectal temperatures (37.7 +/- 1.0 degrees C) were maintained. Heart rate was 184.8 +/- 34.5 bpm. Hematocrits were 29.6 +/- 6.0%, activated clotting time was sustained above 400 s throughout bypass, blood gas parameters were maintained in the normal range (pH, 7.39 +/- 0.1; PO(2), 123.1 +/- 65.2 mm Hg; PCO(2), 37.2 +/- 8.5 mm Hg; and HCO(3)(-), 21.5 +/- 3.6 mmol/L). CPB was terminated after 8 h and no visceral edema or other imbalances normally associated with swine on bypass were observed. CONCLUSIONS: Results demonstrate a model of stable long-term bypass in neonatal swine which can be used to study issues critical to children requiring surgical correction and CPB at a young age. Overall effects of surgery and bypass on these younger patients have yet to be explored and therefore a stable long-term normothermic model of CPB would allow the study of numerous parameters associated with this complicated procedure.

A high-performance liquid chromatographic (HPLC) method for the simultaneous determination of nitrite and formaldehyde from foods.

A high-performance liquid chromatographic (HPLC) procedure with fluorometric detector has been developed for the determination of nitrite and formaldehyde from foods by the use of hydralazine. Hydralazine reacts with nitrite and formaldehyde under acidic conditions in boiling water-bath for 15 min to form tetrazolo-(5,1-a)-phthalazine (Tetra-P) and triazolo-(3,4-a)-phthalazine (Tri-P) quantitatively. Without extraction, the determination of Tetra-P and Tri-P was simple, specific, sensitive and reliable over the range of 0.003-0.3 ppm of sodium nitrite and 0.02-0.4 ppm of formaldehyde. This procedure using hydralazine is one of the most useful methods for routine analysis of nitrite and formaldehyde in foods, biological fluids and ambient waters.

Determinants of low systemic vascular resistance during cardiopulmonary bypass.

Although low systemic vascular resistance occurs during normothermic and hypothermic cardiopulmonary bypass, the determinants of depressed systemic vascular resistance and its effect on outcomes are unknown. To assess the predictors and clinical effects of low systemic vascular resistance, 555 patients undergoing isolated coronary artery bypass grafting were evaluated prospectively. The extent of low systemic vascular resistance during bypass was estimated by the amount of the vasoconstrictor phenylephrine administered: group 1, 0 to 160 micrograms; group 2, 161 to 800 micrograms; group 3, more than 800 micrograms. Multivariate analysis identified bypass temperature, bypass time, and ventricular function as determinants of low systemic vascular resistance. Patients on normothermic bypass accounted for 65% of the patients in group 3 and only 34% of the patients in group 1 (p < 0.0001). The bypass time was longer in the patients in group 3 (97 +/- 28 minutes) than in the patients in group 1 (89 +/- 24 minutes; p < 0.006). Patients with a preoperative left ventricular ejection fraction of 0.40 or less required less phenylephrine during cardiopulmonary bypass (498 +/- 68 micrograms) than did patients with a fraction exceeding 0.40 (1,087 +/- 88 micrograms; p < 0.001). By multivariate analysis, advanced age and the presence of peripheral vascular disease were found to decrease the likelihood of low systemic vascular resistance during normothermic bypass. Diabetes, the left ventricular ejection fraction, the bypass time, and the total cardioplegia infused were found to influence the likelihood of low systemic vascular resistance during hypothermic bypass. Patients in group 3 had a higher cardiac index and lower-mean arterial pressure and systemic vascular resistance postoperatively. In those patients who received a left internal mammary artery graft, the incidences of the low-output syndrome (group 1, 4.9%; group 3, 2.7%; p = not significant) and myocardial infarction (group 1, 1.4%; group 3, 1.8%; p = not significant) were not influenced by the amount of phenylephrine infused during cardiopulmonary bypass. In those patients who were at high risk of suffering a stroke preoperatively, the hypotension induced by the low systemic vascular resistance and its treatment with phenylephrine was not associated with an increased incidence of stroke (group 1, 5.8%; group 3, 2.8%; p = not significant).

Haemodialysis during cardiopulmonary bypass using a haemofilter.

The decision to employ haemofiltration and/or haemodialysis is based on various criteria depending on institutional protocol. Cardiac surgical patients, especially those with renal failure, often require fluid and electrolyte intervention. In the past haemodialysis patients were closely monitored and often delayed for surgery depending on their electrolyte status. Operative technique was changed to accommodate the impending sequelae of cardioplegic solutions, blood transfusions and fluid administration. Although haemofiltration has been used successfully in the management of hypervolaemia and anaemia due to haemodilution, the rate of uraemic toxins and solute removal may not be adequate. The use of haemodialysis helps in the treatment of these difficult and often unpredictable cases. The type of dialysate and method of administration has simplied the technique of haemodialysis, during CPB, allowing effective solute and toxin removal while being able to control the amount of fluid removed.

Gas chromatographic characterization of the relationship between some Mycobacterium avium and Mycobacterium paratuberculosis strains.

Mycobacterium avium strain P-55 and M. avium strain DENT differ from M. avium strain 16909-338 on the basis of their fatty acid spectra (C14:0, C18:0 and tuberculostearic [TBS] acids) studied by multivariate statistical analyses. Strains P-55 and DENT are closer to M. paratuberculosis strain 5889 than to M. avium strain 16909-338, a finding which is in harmony with earlier immunological observations. The recently isolated M. paratuberculosis strain 385 has proved different from M. paratuberculosis strain 5889.

In vitro testing of the anti-mycoplasma effect of some anti-coccidial drugs.

The anti-mycoplasma effects of the ionophores (lasalocid sodium, monensin and nigericin) were compared with that of tylosin tartrate and tiamulin in vitro. Forty-four strains representing 14 avian and 10 mammalian Mycoplasma species and serotypes and 5 Acholeplasma species were tested. The ionophores showed average minimal inhibitory concentration (MIC) values between 3.65 and 4.93 micrograms ml-1 for all strains, the MIC values for glucose-fermenting strains were between 2.26 and 3.75 micrograms ml-1, significantly lower than for arginine-hydrolysing strains (9.27-13.12 micrograms ml-1). These values were significantly higher than those obtained with tylosin tartrate (0.45 micrograms ml-1) or tiamulin (0.13 micrograms ml-1). The ionophores were more efficacious against acholeplasmas (0.06-0.25 micrograms ml-1) than against mycoplasmas.

A protease inhibitor of Nippostrongylus brasiliensis.

Somatic extracts of Nippostrongylus brasiliensis contain protease inhibitor(s) capable of inhibiting the activity of trypsin and chymotrypsin A and B. This inhibitor was partially purified by affinity chromatography. Its molecular weight is in the range of 9500-10 000. The inhibition of both trypsin and chymotrypsin depends on the same or closely adjacent active sites of the inhibitor molecule. The inhibitor is unaffected by heating, pH changes or urea, but is sensitive to 2-mercaptoethanol The formation of the enzyme-inhibitor complex is time-dependent. The complex does not dissociate with KC1. The inhibitor has no effect on the activity of elastase, subtilisin, pepsin, rennin, papain and collagenase.

A trypsin and chymotrypsin inhibitor from the metacestodes of Taenia pisiformis.

The metacestodes of Taenia pisiformis have been shown to contain a protease inhibitor capable of inactivating the esterolysis of N-alpha-benzoyl-L-arginine ethyl ester (BAEE) and N-benzoyl-L-tyrosine ethyl ester (BTEE) by trypsin and chymotrypsin, respectively, of bovine, dog and rabbit origin, but not affecting the hydrolytic activity of subtilisin, elastase, collagenase, pepsin, rennin and papain. This inhibitor has been demonstrated in whole worm extracts and in the incubation medium of in vitro-maintained, intact living metacestodes. The protease inhibitor which was purified by trichloroacetic acid precipitation, Sephadex G-100 chromatography and affinity chromatography on CNBr-activated Sepharose 4B-bovine, chymotrypsin conjugate was soluble in 5% trichloroacetic acid, withstood heat up to 80 degrees C, tolerated the pH range 1.5 to 9.0, was unaffected by 8 M urea or 0.2 M 2-mercaptoethanol and had a molecular weight of about 7000 to 7200, as calculated from its gel chromatographic behaviour. Complex formation between the inhibitor and the enzymes required 3--4 min for completion. The enzyme-inhibitor complex was not dissociated by 4 M KCl. Activity determinations on bovine TPCK-trypsin and bovine chymotrypsin with BAEE and BTEE assays revealed that the inhibitory actions toward both enzymes are functions of the same or closely adjacent sites of the inhibitor molecule. The supposed function of the inhibitor is discussed.