Influence of renal artery blood flow on renal function during aortic surgery.

BACKGROUND: This study was undertaken to determine the true incidence of renal impairment after aortic surgery and its association with intraoperative fluctuations in renal artery blood flow and cardiac output. METHODS: Direct measurements of renal artery blood flow were undertaken with electromagnetic flowmetry in 19 patients undergoing elective infrarenal aortic surgery. Renal function was assessed before and after operation by measurement of creatinine clearance. RESULTS: Twelve patients (63%) had renal impairment as defined by a 40% or greater reduction in creatinine clearance after operation. This group of patients had significantly lower renal artery blood flow during the period of aortic cross-clamping than had those who preserved their renal function (p < 0.001). CONCLUSIONS: Renal impairment is common after infrarenal aortic surgery and may be a result of intraoperative ischemia secondary to reduced renal artery blood flow.

The preservation of renal function by isovolemic hemodilution during aortic operations.

PURPOSE: In an investigation of the effects of isovolemic hemodilution, 39 consecutive patients undergoing elective infrarenal aortic operation had detailed measurements of renal function, renal artery blood flow, and cardiac hemodynamics. METHODS: The patients were randomly allocated to receive acute preoperative isovolemic hemodilution to a hematocrit of 28%, with 20 patients receiving hemodilution and 19 being control subjects. RESULTS: Twelve (63%) of the control group had renal impairment, compared with only four (20% in the group receiving hemodilution (p < 0.01). Hemodilution also prevented the fall in cardiac output induced by cross-clamping (p < 0.01) and significantly reduced the need for transfusion of donor blood (p < 0.01). CONCLUSIONS: Acute isovolemic hemodilution is clearly a useful adjunct in the management of patients undergoing elective aortic operation.

Dynamic preoperative assessment of cardiac reserve in elective aortic surgery.

Myocardial infarction accounts for over 50 per cent of mortality following elective abdominal aortic surgery. Previous history of ischaemic heart disease and abnormal ECGs, common in vascular patients, are unreliable parameters for predicting myocardial response to stress. Exercise ECGs are often valueless, as claudication may mask myocardial insufficiency. Myocardial performance was studied preoperatively in 29 consecutive patients undergoing elective aortic bifurcation grafting, using a Swann-Ganz catheter to measure the rise in pulmonary artery wedge pressure (PAWP) produced by rapid intravenous infusion of plasma (200-400 ml). A Frank-Starling Curve was obtained by plotting LVSWI against PAWP. Two important values were obtained: (a) 'Upslope' or gradient of the ascending portion of the curve. Low values identify patients most at risk from cardiac complications. Six patients who suffered from postoperative cardiac complications had a mean 'upslope' value of 1.568 +/- 0.681 (1 s.e.m.), whereas the 23 who did not, had a mean value of 7.094 +/- 0.745 (1 s.e.m.), a significant difference (P less than 0.001); (b) 'PAWPmax', the ventricular filling pressure above which work output dropped. Infusion beyond this may precipitate pulmonary oedema. PAWP was observed at levels greater than PAWPmax in all 6 patients who developed either pulmonary oedema or myocardial infarction. The myocardial performance curve can reliably identify high risk patients and permit control of intravenous therapy within individual safety limits, thereby preventing pulmonary oedema.

Ultrastructural changes occurring during germination and outgrowth of spores of the thermophile Bacillus acidocaldarius.

Spores of the thermophilic, acidophilic, Bacillus acidocaldarius were covered by a thick outer coat and a laminated inner coat (5.5 nm periodicity). Small membranous vesicles were present in the spore core and they disappeared as germination proceeded. After depolymerization of the cortex, and a 30% increase in spore diameter a localized gap appeared in the laminated inner coat only. This inner coat gap was narrow and could be the whole length of the spore. The germ cell appeared to grow, or to be pushed towards the inner coat gap, at which stage the outer coat disappeared in the same localized area. As the vegetative cell grew out the spore coat fell away, with loose cortical material still attached to it. The young germ cell developed a large spherical electron dense inclusion body in the cytoplasm, at the same time as the ribosomal and nuclear areas became distinct.