HEMOFILTRATION   Free access

Minerva Anestesiologica 1999 June;65(6):427-32

Copyright © 2000 EDIZIONI MINERVA MEDICA

language: English

Hemofiltration during cardiopulmonary bypass

Journois D.

Department of Anaesthesiology and Intensive Care Medicine, Hôpital Laennec - Paris

Several fac­tors com­bine to facil­i­tate the evo­lu­tion ­towards ­heart and mul­ti-­organ fail­ure fol­low­ing car­diac sur­gery. Some of ­these fac­tors are relat­ed to ­pure car­diac ­aspects ­like the exis­tence of a pre­op­er­a­tive ­heart dis­ease, the use of aor­tic ­cross clamp­ing or per­for­mance of car­di­ot­o­my. Cardiopulmonary ­bypass (CPB) ­also ­plays an impor­tant ­role in the occur­rence of post­op­er­a­tive ­organ dys­func­tions by two prin­ci­pal ­means: first­ly by induc­ing a pro­found hemo­di­lu­tion, ­which ­impairs oxy­gen trans­port ­through tis­sues. This phe­nom­e­non is point­ed out in the post­op­er­a­tive peri­od by the exis­tence of ­increased trans­pul­mo­nary O2 gra­dients, extra­vas­cu­lar ­lung ­water vol­ume and sub­se­quent impair­ments of O2 trans­port. Secondly CPB is del­e­ter­i­ous by trig­ger­ing an impor­tant inflam­ma­to­ry reac­tion. This reac­tion is large­ly relat­ed to the ­ratio of the cir­cuit ­area to the ­patient’s ­body sur­face ­area and is there­fore max­i­mal in chil­dren. It has ­been wide­ly dem­on­strat­ed ­that the ­very ear­ly ­paths of ­this reac­tion ­imply sev­er­al humo­ral fac­tors includ­ing ­kinins, coag­u­la­tion fac­tor-XII and com­ple­ment frag­ments. The acti­va­tion of ­these fac­tors is ­self-ampli­fied and trig­gers ­both expres­sion and ­release of numer­ous medi­a­tors by endo­the­lial ­cells and leu­ko­cytes. Finally, ­these medi­a­tors are respon­sible for the ­well ­described “­post-­bypass syn­drome” ­which is, ­from a clin­i­cal view­point, ­very ­close to hyper­ki­net­ic sep­tic ­shocks.
Several meth­ods ­have ­been pro­posed to ­reduce the del­e­ter­i­ous ­effects of ­both car­diac sur­gery and CPB. The old­er one is hypo­ther­mia ­that con­sid­er­ably reduc­es the trig­ger­ing of the inflam­ma­to­ry medi­a­tors net­work. Heparin-coat­ed cir­cuits may ­also ­reduce ­this reac­tion to ­some ­extent. Hemofiltration has ­been intro­duced in the 90’s in CPB man­age­ment. Because of its ­very ­high tol­er­ance in ­patients ­with com­pro­mised cir­cu­la­to­ry stat­us ­this tech­nique was ­already ­used in the post­op­er­a­tive peri­od to ­treat ­patients ­with ­acute ­renal fail­ure. Initially hemo­fil­tra­tion was intend­ed to cor­rect the accu­mu­la­tion of extra­vas­cu­lar ­water dur­ing or imme­di­ate­ly fol­low­ing the sur­gi­cal pro­ce­dure. Nevertheless sev­er­al of its “ ­side-­effects ” ­appeared to be use­ful ­like reduc­tion of post­op­er­a­tive ­blood ­loss and imme­di­ate hemo­dy­nam­ics improve­ment. Several stud­ies attempt­ed to ­point out the mech­a­nism of ­action of hemo­fil­tra­tion and ­although remov­al of inflam­ma­to­ry medi­a­tor ­occurs, ­there is cur­rent­ly no ­proofs ­that ­this remov­al is the actu­al mech­a­nism by ­which ­this tech­nique ­acts.
At the ear­ly begin­ning of the use of its util­iza­tion hemo­fil­tra­tion dur­ing car­diac sur­gery ­aimed ­either to con­cen­trate ­blood at the end of the pro­ce­dure or to rap­id­ly ­restore a nor­mal ­fluid and elec­tro­lytes bal­ance. Today ­some new imple­men­ta­tions of ­this tech­nique are pro­posed ­either to ­reduce the trig­ger­ing of the inflam­ma­to­ry reac­tion to CPB or to ­reduce the imme­di­ate post­op­er­a­tive ­drug sup­port.