A gelatin plasma expander (Haemaccel) was used as a priming fluid in 10 cases of mitral valve replacement. Measurements of acid-base, coagulation, electrolytes, platelets, urinary output and oxygenation were comparable to those with other priming solutions.S. Afr. Med. J., 48, 1615 (1974

Moyes, D.G.

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10 Augustus 1974 S.-A. MEDIESE TYDSKRIF 1615Haemodilution with a Plasma Expander asPriming Solution in CardiopulmonaryBypassD. G. MOYESSUMMARYA gelatin plasma expander (Haemaccel) was used as apriming fluid in 10 cases of mitral valve replacement.Measurements of acid-base, coagulation, electrolytes,platelets, urinary output and oxygenation were comparableto those with other priming solutions.S. Air. Med. J., 48, 1615 (1974).Haemodilution has become accepted practice in the con-duct of cardiopulmonary bypass in recent years, and 5%dextrose in water or a balanced salt solution is commonlyused to prime cardiopulmonary bypass apparatus. Duri~gbypass and in the immediate period thereafter the flUIdand electrolyte load is redistributed extravascularly andexcreted in the urine. This often necessitates frequent'topping up' of the bypass apparatus, and the need. tomake decisions regarding the choice of 'top-up' fluids.The use of blood in bypass procedures presents the prob-lems of availability, considerable use of skilled time inproviding accurate matching, and in large amounts theproduction of homologous blood syndrome.Consequently we decided to investigate the place of aplasma expander as a priming solution. There is so.meevidence that dextrans have the ability to promote lffi-proved flow in the microcirculation and thereby preventstagnation. However, they have the disadvantage of inter-fering with coagulation mechanisms when used in lar~eamounts. This could lead to difficulties in haemostasIsafter bypass in the heparinised patient. Haemaccel, amodified gelatin, has been shown to be free of adverseeffects on coagulation mechanism. In a comparison withdextrans, Eichler and Stephan I showed that factor V isincreased with Haemaccel, but reduced with dextrans,whereas factors VIII and IX are unaffected by the gelatins,but decreased with the dextrans.The osmolarity of the agent is slightly greater than thatof blood, and for this reason it has been recommendedin the management of hypovolaemic shock. The limits ofhaemodilution have not been precisely defined in man,althou<>h there is a wealth of clinical experience whichindicat~s that haematocrits of between 20% and 30% areDepartment of Anaesthetics, University of Natal, DurbanD. G. MOYES, M.B. CH.B., M.R.C.S., L.R.C.P., F.F.A.P-rincipal Anaesthetist/Senior LecturerDate received: 1 May 1974.13best tolerated during cardiopulmonary bypass. Evidencehas shown that a progressive acidosis. develops during per-fusion with very low haematocrits. 'Haemaccel has been investigated as a diluent for donorblood. In a series of mock perfusions 50 0 dextrose/waterhas been compared with Haemaccel and polyvinylpyrol-lidine (periston-N; Bayer). Leutschaff' demonstrated thatthe in vitro haemolysis was higher with dextrose and sug-gested that the acidic pH of dextrose/water may have beenthe cause. He demonstrated changes in the erythrocytediameter and volume during haemodilution, which wasmore pronounced with glucose and with the presence ofacidic pH. Silvay et al.' demonstrated the effect of dilutingblood with Haemaccel, both in animals and in man, as adiluent at cardiopulmonary bypass. Haemaccel, a modifiedgelatin preparation, is slightly hypertonic and has anosmolarity of 350 - 390 mmHg. The sodium, potassium andcalcium levels are 145, 5,1 and 12,5 mEq/litre, respective-ly. Anions are provided in the form of chloride and poly-peptide. The solution thus has a high calcium and highchloride content. The pH is between 7,2 and 7,3 and thesolution has a relative viscosity (1,7) similar to that ofplasma.PATIENTS AND METHODSTen adult patients selected for mitral valve replacementwere studied. They were selected at random and theclinical status of each patient was comparable; they hadall received digitalis and diuretics as part of the presurgi-cal preparation. The standard practice is to discontinuedigitalis 48 hours before surgery. The Temptrol oxygenatorused in these studies has a priming volume of 2,2 litres. Inthis study the prime was made up of 1,5 litres of Haemac-cel and 0,7 litres of Ringer's lactate. The premedicationused was papaveretum and hyoscine.The anaesthetic sequence followed in this study wasthiopentone, muscle relaxant, nitrous oxide/ oxygen, andcontrolled moderate hyperventilation. In addition, smalldoses of droperidol and fentanyl were u~ d. The bypassprocedures were carried out at normothermia. The fol-lowing parameters were monitored as a routine during theprocedure: radial artery pressure, central venous pressure,ECG, nasopharyngeal temperature, urine volume, acid-base status, coagulation studies, and serum electrolytes.The last 4 measurements were taken after induction ofanaesthesia, before bypass, at half-hourly intervals on by-pass, and hourly after bypass. The parameters weremeasured finally at 24 hours.1616 S.A. MEDICAL JOURNAL 10 August 1974RESULTSCoagulation: The prothrombin index, thrombotest, clot-ting time, thrombin time, fibrin index, recalcification test,fibrinolysis, and prothrombin consumption index weremeasured regularly as described. Values obtained weresimilar to those noted in association with bypass proce-dures in which dextrose/water or Ringer's lactate wasused as priming solution. There was no clinical evidenceof deficient haemostasis, and no evidence of anaenUa inthe postoperative stage at 24 hours.Urinary output: Pre-operatively the glomerular filtrationratios varied from 35% to 88%, with a mean of 58%.During cardiopulmonary bypass the lowest output was2,5 rnl/kg/hour. In the postoperative phase output wasin general good, and with one exception exceeded 60 rnl/hour. This patient required two incremental doses offurosemide.Electrolytes: Sodium, potassium, chloride and totalserum calcium were measured throughout this procedure.Two patients required intravenous potassium after bypassto counteract hypokalaemic dysrhythmia. The levels ofchloride and calcium remained within normal limits.Platelets: In our experience with other priming solutions,cardiopulmonary bypass depresses the platelet count toabout 50% of control values, recovering to about 67°(, at24 hours. The platelet values in the patients receivingHaemaccel followed this pattern.Acid-base status: The use of Haemaccel tended to causea slight metabolic alkalosis, and sodium bicarbonate wasnot required. The lowest base deficit recorded was -1,5mEqjlitre.Oxygenation: There was no difference in the arterialoxygen level in this study compared with others in whichdextrose/water or Ringer's lactate were used as primingmedia.Blood loss: The mean recorded blood loss in the first24 hours was 2,5 litres. Haematocrits returned to pre-by-pass levels 2 - 3 hours after bypass in every patient. In alarge series of mitral valve replacements with other primingmedia the mean loss was 2,9 litres.DISCUSSIONHaemaccel can be recommended theoretically as a primingfluid at cardiopulmonary bypass by virtue of its pH,flow characteristics, absence of effect on coagulationmechanisms, absence of antigenic propensities, and stabi-lity in storage. The molecular size of Haemaccel rangesfrom 5 000 to 50 000, with a mean molecular weight ofbetween 30000 and 35000 and a half-life of between 8and 10 hours.Extensive clinical experience has indicated that haemo-dilution to a haematocrit of 20 - 30°(, produces the bestresults in terms of tissue respiration and electrolyte andcoagulation haemostasis. It is desirable that the diluentchosen will not challenge these ends. For ease of manage-ment, it is desirable that the diluent will stay within thevascular space for the duration of cardiopulmonary by-pass, and that renal elimination should occur to restorethe haematocrit to within 10% of normal in the immediatepostoperative period. Haemaccel appeared in this shortstudy to fulfil the criteria outlined above, and meritsfurther intensive clinical trial.REFERENCESJ. Eichler, J. and Slephan, G. (1969): Bib!. haemal. (Base!), 33, 452.2. Leutschaff, R. (1969): Ibid., 33, 569.3. Silvay, J., Sujansky, E., SchnoITer, M., Hrubiskov:i, K., Slez:ik. J.,Gabauer, I. and Slyk, J. (1968): J. Thorac. Cardiovasc. Surg., 55, 3.

Haemodilution with a plasma expander as priming solution in cardiopulmonary

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Haemodilution with a plasma expander as priming solution in cardiopulmonary

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