Controlled hypotension during operation for coarctation of the aorta.

Since 1948 61 patients have been operated on for coarctation of the aorta at the University Hospital, Copenhagen. The technical problems of this operation are largely due to the high blood pressure proximal to the stenosis and in the highly developed and dilated collaterals which are forced to act as a by-pass round the stenosis. These dilated and fragile vessels, particularly the intercostal arteries, may bleed profusely, making it difficult to obtain haemostasis. Moreover, since the blood pressure often increases in the course of the operation a considerable amount of blood may be lost. In a high proportion of the cases the obstruction to flow at the narrowing is almost complete. For this reason there is seldom any material increase in blood pressure when the stenosed part of the aorta is clamped off, unless the subclavian artery has to be clamped too. On the other hand, the blood pressure usually falls quite precipitously when the anastomosis is completed and the flow through the aorta re-established. In order to compensate for this fall, a large volume of blood has to be administered in the course of a short time. In some cases, intra-arterial transfusion may be required. In an endeavour to avoid this sudden fall in pressure, the forceps clamping off the aorta should be released gradually once the anastomosis is completed. This is illustrated by the blood pressure curve in Fig. 1. The introduction of controlled hypotension by ganglion-blocking agents (Davison, 1950; Enderby, 1950) offers considerable advantages in surgery generally, and in fact the immediate advantages of controlled hypotension in these operations are great. Haemostasis is facilitated, haemorrhage is reduced, and the otherwise inevitable increase in blood pressure when the collateral circulation is ligatured is avoided. Moreover, there is practically no further fall in blood pressure when the clamps are removed from the aorta. The time required for the operation is materially cut down. Owing to the slight haemorrhage, less blood has to be administered, and the rapid transfusions required because of the major decrease in blood pressure are avoided. Controlled hypotension during surgery for the relief of the aorta has been advocated by Lucas (1954), Griffith (1954), and Lundskog (1954), but they have not yet published their actual results. During controlled hypotension particular attention has to be paid to haemostasis, since negligible oozing may be transformed into brisk haemorrhage when the blood pressure rises again. Eighteen patients have been operated on using this technique in Rigshospitalet, 17 with resection of the stenosed area. In the remaining instance, the intervention was exploratory. In the major group one patient died shortly after the operation (see later), and another died after re-operation due to thrombosis.