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A.31

COMPARATIVE ASSESSMENT OF THE BIOCOMPA TIBILITY OF 4 TYPES OF TUBING FOR CARDIOPULMONARY BYPASS

F.Briquet, M.F Hannand, C.Isetta DOW CORNING Sophia Antipolis 06904 FRANCE

INTRODUCTION: The contact of blood with the wall of tubing for extracorporeal circulation (ECC), gives rise to many interactions at the interface of the material and its bioenvironment. This activation involves different plasmatic systems and may even provoke a generalized inflammatory reaction syndrome during cardiopulmonary bypass (CPB). A comparative assessment has been initiated with 4 types of tubing used in CPB applications. The methodology consisted of in vitro static-dynamic and in vivo tests to determine if these products could lead to clinical differences. This paper addresses the first in vitro part of this global study. Parameters tested are biomarkers of the coagulation-fibrinolytic cascades, the complement system and leukocyte activation. METHOD: Tubing materials were represented by 2 cross­linked silicones using a platinum catalyst (RX Pump­DowComing) or a peroxide initiator (Raumedic ECC-Rehau), a polyvinyl-chloride (PVC) (Medituub-Draka Plastics) and a heparin-coated PVC (Bentley Bypass 70-Baxter). The same production batch was used throughout the study for each of the materials. Static tests were performed according to ISO 10993-4 and by direct material contact or by filling a defined length of tubing with one or several fresh samples of human blood. Dynamic tests were performed simultaneously with heparinized fresh human blood circulating by a set of rotative pumps. A CPH circuit was recreated to reproduce the clinical conditions and the tests made with two different bloods. RESUL TS: In static conditions, no significant differences were found by testing the cytotoxicity, haemolysis and the CH50, C3a and C5a. Leukocyte adhesion evaluated by light microscopy, showed a significantly lower count for both silicone tubings at 5 min. The same cell adhesion at 15 min remained constantly low with the silicone platinum whereas it increased with the silicone peroxide and disappeared for both PVc. In dynamic conditions, fibrinogen adhesion tested by chronometry, was lower with both silicones at 60 min, but equivalent values were found after 120 min for all materials. Complement activation, with the CH50 value assessed by using the technique of Mayer, was lower for the silicones at any sampling time and contrary to both PVC. DISCUSSION: Results obtained by in vitro static as well dynamic conditions showed that both silicone tubings had less effect on some parameters linked to the coagulation equilibrium and the complement system which are acting in the CPB syndrome. REFERENCES l.Kirklin JK Westaby S, Blackstone EH, et al. Complement and the damaging effects of cardiopulmonary bypass. J Thorac Cardiovasc Surg 1983; 86: 845-857 2.Kirklin JK, George IF, Holman W. The inflammatory response to cardiopulmonary bypass .. In: Gravlee GP, Davis RF, eds. Cardiopulmonary Bypass: Principles and Practice. Baltimore: Williams Wilkins, 1993; 233-248.

CARDIOPULMONARY BYPASS MANAGEMENT

A.32

PERI OPERA TIVE CHANGES IN RECEPTORS FOR ICAM-1/CD54 & IMMUNGLOBULIN G ON MONOCYTES BY EXTRACORPOREAL CIRCULATION (ECC)

Hiesmayr M, Spittler A, LaBnigg A, Berger R, Boltz G, Roth E Dept. of Cardiothoracic and Vascular Anaesthesia and Intensive Care and Dept. of Surgical Research, University of Vienna, Austria

INTRODUCTION: Circulating monocytes partiCipate in the unspecific as well as specific immunologic functions. Monocytes interact with activated endothelial cells 1 and partiCipate in the inflammatory response to injury. After cardiac surgery with use of a heart-lung machine (HLM) a 'post perfusion syndrome' is common2

• The aim of this study is to evaluate the changes in monocytes phenotype due to EGC and surgery.

METHODS: After approval of the ethical committee and informed consent 17 patients were included: ECC (8) had cardiac surgery with HLM while THOR (9) had cardiac or thoracic surgery. The anaesthetic technique included etomidate, midazolam, pancuronium and fentanyl, and ventilation with oxygen in air. The HLM was primed with Ringer's Lactate, mannitol 20 g and aprotinin 500,000 IE. The Monocyte receptors for IgG (Fey RIICD64, Fey RII/CD32, Fey Rill! CD16), IGAM-1/CD54 and GD14 were determined in whole blood by FACS analysiS. The 4 timepoints were before anaesthesia (awake), before skin incision (anaesthesia), at the end of operation (operation) and on the morning after surgery (post OP + 1d). Statistical analYSis was done by repeated measurement analysis of variance (Systat 5.0). Data are given as mean ±SD.

RESULTS: There was no difference in age, weight, height, sex and ASA score between groups. The duration of the operation was 301 ±110 (EGG) and 175 ±42 (THOR). The dose of midazolam and fentanyl were similar as was the postoperative dose of opioids. There was no change in CD16. There was no difference in the time course of CD64 (Fig.1 a) between groups, but CD64 fell with anaesthesia (p<0.001) and increased after surgery (p<0.001). CD32 and CD54 (Fig.1b) fall both (p<O.01) due to the HLM.

LL ~ECC

~_THORAX

I, ~ i i ••

awake operation awake operation aruesthesia post OP+1d aruesthesla post OP+ld

DISCUSSION: The use of a HLM induces a depreSSion in the immunglobin receptor CD32 and the receptor for ICAM1 that may be related to the inflammatory syndrome after cardiac surgery. '

REFERENCES: 1 Wang J, Beekhuizen H, van Furth R. Surface mOlecules involved in the adherence of recombinant interferon-gamma (rIFN-gamma)-stimulated human monocytes to vascular endothelial cells. Clin Exp Immunol 1994; 95: 263-269. 2 Boldt J, Osmer C, Linke L et al. Circulating adhesion molecules in pediatric cardiac surgery. Anesth Analg 1995; 80: 1129-1135.

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A.33

BLOOD LACTATE DURING CARDIOPULMONARY BYPASS WITH A LACTATED PRIMING SOLUTION.

David Hett. Sally Pilkington, Ellen Janke, Stuart Sheppard, David Smith.

Wessex Cardiothoracic Unit, Southampton General Hospital, Southampton, United Kingdom.

Introduction. Diabetic patients have a low pyruvate dehydrogenase activity with reduced metabolism of lactate in extra-hepatic tissues [I]. Hartmann's solution (Ringers-Lactate solution) is not recommended for diabetic patients [2].

Methods. We studied 100 adult patients (40 non-insulin dependent diabetics, 20 insulin dependent diabetics and 40 non­diabetics) having elective cardiac surgery. Patients in each group were randomly allocated to receive either Hartmann's solution 21 plus heparin 6000 iu (H) or Ringer's solution 21 plus heparin 6000 iu (R) as prime. The same solution was used if any additional fluids given during bypass, and blood glucose was controlled with an insulin infusion. Blood was taken for baseline glucose and whole blood lactate estimations at induction of anaesthesia and at aortic cannulation. Further measurements of lactate were made every 15 minutes during bypass, and glucose was measured hourly. Lactate and glucose were measured again at skin closure. Results were analyzed by Student's t-test.

Results. The lactate concentrations are in the table below (normal value in our laboratory <2.0 mmon\ The glucose concentrations did not differ significantly between the groups.

Cannulation 30 min CPB Skin closure Normal R 0.9(0.6-2.3) 1.0 (0.8-2.S) 1.4 (0.6-3.3) Normal H 1.3 (0.6-3 9) 1.9 (1.1-3.1) 1.6 (0.8-2.S)

NIDDM R 1.4 (0.8-2.2) 1.3 (0.8-2.l) 1.6 (0.7-3.6) NIDDM H 1.6 (0.3-3.l) 2.5 (1.0-S.1)* 2.3 (0.8-6.1)*

IDDM R 1.0 (0.7-1.6) 1.1 (0.8-1.6) 1.9 (0.9-3.2)* IDDM H 1.3 (0.6-2.9) 2.2 (1.6-3.0)* 2.1 (1.1-3.9)*

Mean (range) whole blood lactate in mmoll-1.

IDDM = insulin dependent, NIDDM = non insulin dependent. *p < 0.05 compared to cannulation baseline

Discussion. Although mean values were not excessive, some diabetics had high lactate concentrations after bypass. Half the cardiac centres in Britain use a lactated prime [3] but our results suggest that a lactate-free prime is preferable for diabetics.

References. I. Mukherjee C, Jungas RL. Activation of pyruvate

dehydrogenase in adipose tissue by insulin. Evidence for an effect of insulin on pyruvate dehydrogenase phosphate. Biochemical Journal 1975; 148: 229.

2. Alberti KGMM, Thomas DJB. The management of diabetes during surgery. British Journal of Anaesthesia 1979; 51: 693-710.

3. Hett DA, Smith DC. A survey of priming solutions used for cardiopulmonary bypass. Perfusion 1994; 9: 19-22.

A.34

STANDARD PUMP FLOW RATE AND SVO, ABOVE 60% DO NOT IMPLY ADEQUATE OXYGEN DELIVERY DURING CPO

F Ryckwaert, P Colson, G Brunat, P Wintrebert

Service d' Anesthesie Reanimation R Montpellier, France.

17

Introduction: Mixed venous oxygen saturation (SV02) is generally accepted as an indicator of adequacy of systemic oxygen delivery; However, cardiopulmonary bypass (CPB) may alter this relationship) Lactate production commonly found in patients undergoing CPB, is a marker of this alteration. The aim of this study was to determine the causes of this alteration during hypothermic CPR Methods: In routine coronary artery bypass graft surgery (CABG) at our institution, CPB is initiated while completing the proximal anastomosis with a side-clamped aorta. Cooling is initiated at the end of this period, then the aorta is cross-clamped and the heart is arrested by infusion of hypothermic hyperkalaemic cardioplegia, and the distal anastomoses are sutured in place. As the grafting process approaches 75% completion, core temperature is gradually increased to 37°C. SV02 during CPB is held above 60%. Pump flow rate (PF) is maintained above 2.41 min,1 m-2 during non hypothermic CPE. Time between the onset of CPB and the end of cooling ("time to n ") was noted. Arterial and venous blood gases, oxygen extraction (02-Extr), ~C02 (defined as PvC02-PaC02 mmHg), lactate level and core temperature were studied during CPB and at arrival in ICU in 20 patients undergoing CABG, The variables were measured after induction of anaesthesia (TO), after cooling to 27°C (Tl), after aortic cross declamping (T2), after rewarming to 37°C (T3) and 1 hour after arrival in ICU (T4). Data are expressed as mean ± SO; linear regression analysis, ANOVA and Student'S t-test for repeated measures were used when appropriate. Results: Lactate level increased significantly (p<O.OS) at n, remained stable at T2 and T3, and decreased significantly (p<O.OS) at T4 (Figure 1). Lactate level at Tl was correlated with "time to Tl" (r= 0.47, p=0.035) Lactate level at T4 was correlated with PF during rewarming (r=0,72, p=0,006), During the hypothermic period, O2-Extr and ~C02 decreased significantly (p<O.OS) «10% and <3.5 respectively) and increased (p<0.05) during rewarming.

Figure 1 : Lactate level during CPO

4 ~~----~----~-----L----~--r 3,5

3

2,5

2

1,5

mmol.l-l

TO

*p<o.os

T1 T2 T3 T4

Conclusion: Meaningful changes in regional oxygen kinetics occur during CPE. These effects, possibly related to increased production of endogenous vasoconstrictors, are lightened by lowering core temperature. However, during non hypothermic CPB, SV02 and pump flow of more than 60% and 2.41 min-) m-2 respectively, do not imply adequate systemic o":ygen delivery. Reference: 1.- McDaniel LB, et al. Mixed venous oxygen saturation during cardiopulmonary bypass poorly predicts regional venous saturation. Anesth Analg 1995: 80: 466-72.

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A.35

CEREBRAL BLOOD FLOW RESPONSE TO CHANGES IN CO2 AT HYPOTHERMIA AND NORMOTHERMIA. A

CONTROLLED, RANDOMIZED CROSS-OVER STUDY

Weyland A, Grune F, Stephan H, von der Veldt J, Kazmaier S, Sonntag H

Zentrum Anaesthesiologie, Rettungs- und Intensivmedizin Georg-August-Universitat Gottingen, Germany

Introduction: The understanding and application of optimal acid­base management during hypothermic cardiopulmonary bypass (CPB) IS still a subject of controversy. Brain hyperperfusion has been considered as a consequence of pH-stat management. Beside the cerebral response to changes in arterial PC02 (paCOz), other factors have been suggested as additional reasons for this phenomenon (I). We investigated the cerebral haemodynamic consequences of Ct-stat versus pH-stat management and compared these effects with the respective flow response to variations in PaC02 during normothermia in a prospective cross-over study. Method: With ethical committee approval and written informed consent, we investigated 20 patients undergoing coronary artery bypass surgery. First, measurements were performed during spontaneous circulation and normothermia at two different PaC02

levels in a random sequence (control period). During hypothermic CPB (30 DC), measurements were repeated under Ct-stat and pH-stat management, respectively. Each patient served as his own control. PaCOz was measured at 37DC. Measurements of global cerebral blood flow (eBF) were performed with the Kety-Schmidt technique using 70% argon as a tracer. Calculations of cerebral perfusion pressure (CPP) and cerebral vascular resistance (CVR) were based on jugular bulb pressure. Cerebral metabolic rate for lactate (CMR,,,t) was calculated according to the Fick principle. To assess the effects of hypothermic CPB and PaC02, two-way analysis of variance (MANOVA) was performed using a repeated measures design. Results:

Hypocapnia Hypercapnia a.-stat pH·stat PaCOz*"- 33.3±2.9 47.5±5.4 37.2±2.6 50.5±2.8 [mmHg]

HctN 38.1±3.0 38.1±3.0 24.6±2.5 24.9±2.5 [%]

T' '" 35.3±0.3 35.3±0.3 30.2±0.5 30 1±0.5 ['C]

CBF"'# 3h5 55±13 38±lO 63±21 [ml-min-1·lOOg"lj

CtviR1act '" ·1.8±2.2 ·0.8±1.5 ·1.7±3.1 0.0±2.5 [fUIlol.min·'.IOOg"] CPP' 70±12 66±1I 76±16 69±18 [mmHg]

CVR' 2.3tO.6 1.2±0.3 2.2±0.8 1.2±0.5 [mmHg·mr1

min·IOOg]

* sigruficant influence of PaCOl level. • significant influence of hypothennic CPB (MANOV A, p<O.05). Values are mean ± SD.

The periods of different PaC02 levels were comparable with respect to haematocrit (Hct) and nasopharyngeal temperature (T np)' At both levels of PaC02, mean CBF during hypothermic CPB was slightly higher than during the control period. This small increase, however, could be explained by the slight difference in PaC02 levels between the control and the CPB period: CBF values during hypothermic CPB did not show any difference when compared to CO2-adjusted values during the control period (38 vs. 36 and 63 vs. 62 ml.min·'·IOOg·l, respectively). Similarly, cerebrovascular CO2 reactivity of CBF did not differ between the two periods of measurement (4.1 vs. 4.5%/mmHg change in PaC02).

Discussion: This study demonstrates that under moderate hypothermia cerebral haemodynamic differences between Ct-stat and pH-stat management can completely be explained by respective differences in non temperature-corrected PaC02 . Increased CBF during pH-stat acid-base management thus only reflects normal cerebral vasoreactivity to CO2 . The agreement in CBF and in CMR'aoi between the control and the CPB period suggests that the 35% reduction in Hct was counterbalanced by hypothermia-induced reduction in cerebral oxygen demand. References: I. Henriksen L. Brain luxury perfusion during cardiopulmonary bypass in humans J Cereb Blood Flow Metab 1986; 6:366-378

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A.36

SPLANCHNIC BLOOD FLOW DURING CARDIOPULMONARY BYPASS ASSESSED BY INDICATOR DILUTION TECHNIQUE.

Gardeback M*, Settergren G*, Wahren J**, Ekberg K**, Barr G*, Department 0/ Cardiothoracic Anaesthetics and Intensive Care*, and Section o/Clinical Physiology**, Karolinska Hospital, Sweden

Hepatic and gastrointestinal dysfunction following cardiopulmonary bypass (CPB) is an infrequent but serious complication, probably related to low splanchnic blood flow (SBF) in the peri operative period. The incidence of clinically overt gastrointestinal disease following heart surgery may be as low as 0.6 %, but the incidence is probably underestimated in most retrospective studies I There are few studies of SBF during CPB and only one clinical study is published2 The present ongoing study examines SBF using the indicator dilution technique and constant rate infusion of indocyanine green (ICG), compared with echo-Doppler estimations of hepatic blood flow. In the following, only the ICG results are reported. Methods: Ten adult patients were studied, 7 coronary bypass grafting (CABG), I aortic valve replacement (A VR) and 2 combined procedures. Mean age was 64 years (range 40-75). CPB time 86 minutes (58-129) and aortic cross-clamp time 52 minutes (29-98). Following anaesthetic induction the hepatic vein and the pulmonary artery were catheterized. Cardiac output (CO) was measured by thermodilution. ICG was infused at a constant rate of 0.6 mg.min·1

during the study period. After 50 min of ICG infusion arterial and hepatic vein blood samples were drawn every 5th min: I, before surgery (3 paired samples) n, during surgery before CPB (2 samples) and Ill, during hypothermic CPB (33°C)(3 samples). Oxygenation and ICG concentration were measured. Splanchnic oxygen uptake (V02sp) and systemic oxygen uptake (V02), SBF and CO were calculated. Gastric mucosal pH (PHJ was measured with a gastric tonometer. Statistical analysis was performed using t­test and Wilcoxon rank sum test Results: Mean values and standard error of the mean were:

Anaesthesia Surgery CPB SBF (mLmin·1) 765 ± 44 911 ± 88 789 ± 91 SBF in %ofCO 24 ± 0.8 24 ± 2.2 19 ± 1.6' CO (L min· l

) 3.4 ± 0.2 3.9 ± 0.4 4.1 ±O.Z** V02sp (mL min") 52 ±7.8 63 ± 9.3 28 ± 2.6" V02 (mL min·l) 150 ± 16.8 119± 11.8 pHi 7.32 ± 0.03 7.35 ± 0.02 7.33 ± o.oz

(*=p<O.05, ·*=p<O.OI, different from 1st measurement)

The I CG concentrations before and after the extracorporeal circuit were identical and hence there was no extracorporeal dye elimination. The required steady state of arterial I CG concentration was established. Conclusion: CPB did not cause a reduction in SBF. Splanchnic blood flow following anaesthetic was only approx. 50% of the flow in awake subjects3

. V02sp was normal following anaesthetic induction but reduced during CPB. References: I Ohri S, Bowles C. Gastrointestinal complications of cardiopulmonary bypass. In Yacoub M, ed. Annual of Cardiac Surgery. London: 1995; 74-86. 2 Hampton WW, Townsend MC, Schirmer WJ, et al: Effective hepatic blood flow during cardiopulmonary bypass. Arch Surg 1989; 124:458-459. 3 Bmndin T, Wahren J Effects of Lv. amino acids on human splanchnic and whole body oxygen consumption, blood flow and blood temperature. Am J Physiol 1994; 266 (3 Pt I): E396-E402.

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ASSESSMENT OF RIGHT AND LEFT HEART VOLUME INDICES

IN PATIENTS UNDERGOING CORONARY ARTERY BYPASS

SURGERY

W BUHRE, *B SCHORN, S KAzMAIER, A WEYLAND, *S GIAm;ARls,

A HOEFT AND H SONNTAG

Zentrum Anaesthesiologie, Rettungs- und Intensivmedizin, *Klinik jur Herzchirurgie der Universitat Gottingen,

G6ttingen, Germany

Introduction: The value of central venous and pulmonary capillary wedge pressure (CVP, PCWP) as indices for cardiac preload has been questioned during the past years, particularly in patients undergomg cardiac surgery]. Thus, more direct measurements of intravascular volume status have gained increasing interest. The double indicator-dilution-techni~ue enables bedside assessment of intravascular volume status 2

Discrimination of sub compartments like right ventricular end­diastolic (RVEDVi) and left heart volume (LHVi) is available. The objective of this study was to compare the perioperative time course of CVP and PCWP and cardiac volume indices, estimated by indicator dilution, in patients undergoing CABO­surgery. Methods: After ethical committee approval and written informed consent, ten patients were investigated. Cardiac output (CI) was determined by thermodilution. CVP as well as PCWP were determined by standard technique. Additionally, a fibreoptic-thermistor catheter was placed in the aorta]. Ice­cooled indocyanine green dye was injected into the right atrium and resulting thermo-dye curves were detected in the pulmonary artery and aorta. RVEDVi was calculated from the expOilential decay time of the pulmonary artery thermodilution curve according to Newman3 LHVi was calculated from the difference of central blood volume (CBV) and pulmonary blood volume (PBV)1.2 Measurements were performed before (control) and I, 6 and 24 hours after surgery. Statistical analysis was done by one-way analysis of variance using a repeated measures design. Results: Postoperatively, CVP significantly increased, whereas R VED Vi showed a smaller insignificant increase [Tab. I]. Similarly, PCWP was increased during the postoperative time course. In contrast, LHVi decreased. CI was increased in all patients I, 6 and 24h after surgery, whereas stroke volume index (SVI) significantly decreased Ih after surgery.

LHVi RVEDVi CI SVI CVP [ml m") [ml m") [I m") [ml m") [mmHg)

control 272±59 99±16 2.2±O.7 34±9 6±5 Ih 202±44* I09±28 3.2±l.O* 28±6* 11±2* 6h 210±59 I 24±26 3.8±l.O* 35±11 12±2* 24h 215±54 118±18 3.2±1.l* 32±9 9±4*

Table 1: * significant vs. control (p<O.05)

PCWP [mmHg)

9±4 13±3 12±2 lId

Discussion In our patients, RVEDVi, CVP, PCWP and CI increased, whereas LHVi and SVI decreased. The rise in filling pressure may be due to changes in myocardial compliance, since the increase in CI can be explained by an increase in heart rate and catecholamine support after CPB Our results suggest, that after CABO-surgery, cardiac filling pressures are of limited value as a guide for postoperative volume therapy. References: 1. Hoeft A etal. Bedside assessment of intravascular volume status in patients undergoing coronary bypass surgery. Anesthesiology 1994; 81: 76-86 2. Hachenberg T et al. Thoracic intravascular and extravascular t1uid volumes in cardiac surgical patients. Anesthesiology 1993; 79: 976-984 3. Newman EV at al. The dye dilution method lor describing the central circulation: An analysis of factors shaping the time concentrations curves Circulation 1951;4: 735-746

A.38

THE HEMOPUMP AS LEFT VENTRICULAR ASSIST DEVICE IN POSTCARDIOTOMY HEART FAILURE.

Meyns B, Sergeant P, Demeyere R, Vandommele J, Lauwers p. Ferdtnande p. Verwaest C, Daenen Wand Flameng W Gasthuisberg University Hospital Leuven, Belgium

Introduction: Postcardiotomy heart failure is the most· serious complication in cardiac surgery. Even with the use of assist devices survival does not exceed 25%.(1) The Hemopump is a miniature rotary blood pump for intraventricular use. We have used this device since 1989 as a left ventricular assist device in postcardiotomy heart failure. Patients: In this 6-year period 9585 patients underwent cardiac surgery in our hospital. 2.2% were assisted with intra-aortic balloon pumping and 0.6% (57 patients) were assisted with a more powerful assist device for postcardiotomy heart failure. Patients were considered to have a low cardiac output due to left ventricular failure if the cardiac index was less than 2 I min" m,2 or systolic arterial pressure was less than 90 mmHg with left atrial pressure greater than 20 mHg, despite maximal pharmacological support and the intra-aortic balloon pump. In 39 cases we used the Hemopump as left ventricular assist device with the intention to salvage the heart. Mean age was 64.8 (t7) years; 51% needed cardio-pulmonary rescucitation prior to the Hemopump insertion; 41% were anuric and all of these patients were excluded for transplantation because of age or underlying diseases (diabetes, COPD, vascular disease, hypertension). Methods: In a first period, until 31-12-1992, the 21F cannula for introduction through the femoral artery was used in 13 patients. From 1-1-1993 we used the 31 F transthoracic cannula in 26 patients. Results: Immediate haemodynamic improvement was obvious (Table shows mean.:!:SD; paired Student's t-test for significance)

pre-assist assisted p-value LAP (mmHg) 20±4.8 10±3.3 <0.0001 mean ASP (mmHg) 53±11 72±10 <0.0001 Cardiac index 1.7±0.7 3.3±0.7 <0.0001 (I min" m,2) lactate (mmolll) 6.4±4.7 3.1±1.4 =0.0002

56.4% of these patients were weaned and 28.2% were discharged home. Deaths occurred in two clusters: one early phase within 24 hours of commencement of the Hemopump, and one later phase, after one week. Causes of death in the first group were right ventricular heart failure and severe low cardiac output. Immediate haemodynamic improvement was worse in these patients. All patients with a cardiac index < 2.5 I min" m,2 , despite the Hemopump support, died rapidly. Fatalities in the second, late group, were caused by the consequences of multiple organ failure. Device related problems were far more frequent with the femoral cannula (53%) then with the transthoracic cannula (3%). Discussion: The Hemopump is an effective assist device and became our first choice in left ventricular failure. The transthoracic cannula is reliable and easy to use. A 'cardiac index < 2.5 I min" m,2 in the assisted situation carries a bad prognosis. References: 1. Pae WE Jr, Miller CA, Matthews Y, Pierce WS. Ventricular assist devices for postcardiotomy cardiogenic shock. A combined registry experience. J Thorac Cardiovasc Surg 1992; 104: 541-553.

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A.39

EFFECT OF 8-BLOCKERS VERSUS CALCIUM CHANNEL BLOCKERS IN MYOCARDIAL REVASCULARIZATION

WITHOUT CARDIO-PULMONARY BYPASS IN PIGS

Rajek A Podesser R Kupilik N, Hiesmayr M, Moritz A, Haider W, Dept of Anaesthesiology and Intensive Medicine, Dept of Cardiothoracic Surgery, University of Vienna, Austria

Introduction: To develop the surgical technique for internal mammary artery grafting (lMA) on a beating heart, we combined a reduction in heart rate with intraoperative myocardial protection. Therefore we compared intravenous administration of the ~-blocker esmolol (es) and the Ca-channel blocker verapamiI (ver) during the ischaemic period. Methods: After approval of the animal care committee, IMA grafting was done without CPB in 10 pigs (mean weight 21 kg). Anaesthesia was induced and maintained with pancuronium, fentanyl, oxygen and nitrous oxide (50%). Cardiac output (CO), heart rate (HR), mean arterial pressure (MAP) and mixed venous oxygen saturation (SV02) were measured and stroke volume (SV) was calculated. Left ventricular function and wall motion abnormalities were investigated by echocardiography before pericardiotomy (baseline, TO), after drug administration (TI), at the end of ischaemia (T2), (by local clamping of the left anterior descending artery, LAD) and 5 (T3), 15 (T4), 30 (T5), 90 (T6), minutes after the end of ischaemia. Five pigs received esmolol (es-group) and the other 5 pigs received verapamil (ver-group) intravenously during the ischaemic period. Drug dose was increased until heart rate was below 80 beats/min. Results: There were no differences in pre-ischaemic haemodynamics, echocardiography and in ischaemic clamping time of the LAD in both groups. At T2 (end of ischaemia) CO, SV02 and SV were lower in the es-group «0.05). At TI, T2, T3 and T4 there was an increase in wall motion abnormalities and a decrease in left ventricular function in both groups. In the ver­group one pig died because of ventricular fibrillation during ischaemia and in one pig ventricular fibrillation occurred 2 minutes after the end of ischaemia (2/5, 40% incidence of ventricular fibrillation, p<O.OI). Coronary angiography showed all anastomoses to be open. Data are presented as mean ± SEM and *p<O.05. Analysis was done by Student'S t-test.

TO T1 T2 T3 T4 T5 T6 MAP as 109,111:10 85,6±10, 66,4±7,4 81,111:12,1 100,111:8,.2 96,4:t13,~ 105:t82

ImmHa ... 116,8t11 57:t7,7 55,~,3 66,3:t15,E 75,5:t14,E 85,2:t18] 75,5:tl0, CO as 3,QlO,3 2,1:tD,07 l,&:tO,l· 1,7:tO,2 2.2:tO,13 2:tO,2 3,1:tO,4 IImIn ... 3,4:tO," 3:tO,5 2,&:tO," 2,7:tO,6 2,4:tD,5 3,2:tO,7 2,9:tO,3 Hr as 106,111:13 ao,4:t5,7 78,2:t4,6 79,4:t6,l 84,7:1:9,1 95,111:13 121,2:t18, min - 108,2i9.i 90.2:1:9,8 91,2±12 89:t12 105:t15,4 l06,6:t20 96,5:t10,7

SV02 as 84,111:5,7 46,4:t3,4 27,111:5,6 32,3:t6,8 38,7:t5,8 51,111:5,7 60,4:t5,2 '110 .. r 65,5:t3,6 6O:t7,3 SO,5:t4,O 55,3:t4,9 55:t9 542±7,3 53±7,8

Discussion: We found that an infusion of esmolol provides stable MAP values while the other measured haemodynamic parameters were significantly reduced compared to the ver-group. Echocardiography did not show any differences between the two groups. However, there was no case of ventricular fibrillation in the es-group indicating superior antiarrhythmic protection. References: 1. Pfister AI. et al. Coronary artery bypass without cardio­pulmonary bypass. Ann Thorac Surg 1992; 54: J085-1092. 2. Benetti Fl. Direct myocardial revascularization without extracorporeal circulation. Experience in 700 patients. Chest 1991; 100: 312-316.

CARDIOPULMONARY BYPASS MANAGEMENT

A.40

CONTINUOUS TEMPERATURE and 0 2 SATURATION MONITORING of JUGULAR BLOOD during DHCA

PROCEDURES for AORTIC SURGERY

R. Paino, F. Milazzo, B. Amari, M. VisigalJi, M Ferrante, M. Mer[i. Department of Cardiothoracic Anaesthesia and Intensive Care

Ospeda[e Niguarda Ca' Granda - Mi[ano ([ta[y)

There is no consensus concerning adequate monitoring to predict brain protection during deep hypothermic circulatory arrest (DHCA)'. We studied the effects of cardiopulmonary bypass (CPS) with DHCA on temperature (Tjv) and oxygen saturation (Sjv02) of jugular blood. Methods: After Ethical Committee approval and patients' informed consent, 11 patients (pts), (10 M, 1 F) aged 53±11 years, without evident neurological damage, scheduled for aortic surgery, were anaesthetized with isoflurane and fentanyl. Temperatures were obtained by rectal (Tr), nasopharyngeal (Tnp) probes and by a percutaneous thermic probe (Thermod Probe 2.5F, Edwards Lab.) advanced into the right jugular bulb (Tjv) together with a fibreoptic catheter (Opticath Catheter U 425C 4F, Abbott Lab.). All parameters were recorded every minute (min). CPS was performed with a roller pump and hollow fibre oxygenator. Cooling and rewarming were managed according to Tnp (15°C for DHCA and 3rC for complete rewarming) with alpha-stat acid base management. Data (mean±SD) were analyzed by linear regression with p < 0.05 being significant. Results: The table shows values of SjV02. Tr, Tjv and Tnp. Cooling: Cooling time was 59±20 min. Tjv and Tnp were not different at any time, while Tr showed a foreseeable delay. Sjv02 increased until the end of cooling but did not always reach full saturation (86.3±13%). SjV02 did not show any correlation with Tjv, Tnp, Tr, pump flow (CI) and rate of cooling at any time. Mean values of PaC02, Pa02, mean AP (mmHg), pH, CI (I min·' m~2) were 36.2±5, 347±75, 41±13, 7.41±0.05, 2.18±0.5 respectively DHCA: DHCA time was 33.4±17 min. Tjv, Tnp, Tr were stable. SjV02 slightly decreased at mean rate of O.17%/min. Rewarming: Rewarming time was 85.8±26 min. Restarting CPS was associated with immediate Tjv increase (2°C). Tr change showed a forseeable delay during the cooling phase. Restarting CPS was also associated with transient Sjv02 drop (Sjv02=24-87%). Sjv02 drop was significantly correlated with DHCA time (y=0.75 x, r=0.936, p<O. 001). SjV02 under 50% was observed 19 times in pt 1 and 36 times in pt 9. Sjv02 did not show any correlation with Tjv, Tnp, Tr, CI or rewarming rate at any time. Mean values of PaC02, Pa02, mean AP (mmHg), pH, CI (I min" m·2) were 30.1±3.8, 293±100, 49.4±24, 7.47±0.07, 2.4±0.3 respectively. Outcome: 9 pts showed no clinical evidence of neurological dysfunction. 1 pt died while in the operating room, due to heart failure after CPS. 1 pt who showed the lowest Sjv02 (24%) at start of rewarming and several episodes of Sjv02 desaturation, suffered transient postop. coma. Discussion: a) During DHCA procedures Tnp reflects the temperature of blood from the brain as measured by Tjv. b) Tnp 15°C is associated with a variable Sjv02, not always nearing 100%. c) Slight Sjv02 decrease during DHCA implies stagnant blood. d) Restarting CPS moves this stagnant blood: the observed transient low Sjv02 and its significant. correlation with DHCA time suggest persistent brain 02 consumption despite deep hypothermia. It remains to be clarified whether this phenomenon relates to different clinical outcomes and whether reaching 100% Sjv02 before DHCA h 2 as a protective effects .

SjvO,(%) Tjv(OC} Tnp (0G) Tr("QL Start!n>! CPB 70.3+16.2 34.4+1.7 34.8+1.5 35.4t1.5 Durin!L cooling 78.9+17.1

End cooling 86.3+13.3 15.8±1.4 15.4±1.6 19.9±3.6 Startill!lDHCA 87.8t9.5 15.3±1.4 15.4±1.4 19.6:1:3,6 During DHCA 87.7:1:8.9 16.1:1:1.3 15.6:1:1.3 19.7:1:2.8

EndDHCA 85.6±8,O 16.3:1:1.3 16.2:1:1.5 20.2:1:3.3 Startingrewarm. 62.6±21.5 18.3t2.3 17.0±2.4 20.0±3.0 During rewarm. 73.3±14.4

End rewarm. 66.6±16.8 37.5±1.7 36.8±1.8 33.3±3.4

References: 1 Steven JM, Nicolson SC. Pro: Monitoring of nasopharyngeal and rectal

temperatures is an adequate guide of brain cooling before deep hypothermic circulatory arrest. J Cardioth Vasc Anesth 1994; 8: 360-362.

2. Kern FH et al. Temperature monitoring during CPB. in infants: Does it predict efficient brain cooling? Ann Thorac Surg 1992; 54: 749-54.

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CARDIOPCLMO~ARY BYPASS MA:\AGEME~T

A.41

A COMPARISON OF CORE TEMPERATURE WITH THERMAL ENERGY BALANCE IN PREDICTING ADEQUACY OF REWARMING }'ROM HYPOTHERMIC CARDIOPULMONARY BYPASS CD Deakin, AC Sewell, F Clewlowt, JMT Pierce, Departments of Anaesthetics, and Medical Enginccnngt, Southampton General Hospital, Southampton, England,

Introduction: Hypothennic cardiopulmonary bypass (CPB) IS

invariably associated with a significant period of post-opClauve hypothennia despite achieving nonnal or above nonnal core temperatures on tennination of bypass, Thennal energy b:llance on tennination of CPB may provide a better indicator of the adequacy ofrewanning, Methods: We prospectively studied the thennal energy balance and core temperature of cardiac surgical patients at the end of cardiopulmonary bypass and compared them in relation (0 the postoperative temperature profile, Using a thennal energy balance (TEB) meterl, temperature of arterial and venOU5 blood in the bypass circuit was recorded every minute together Wtth pump flow, to allow continuous calculation of thennal energy flux during CPS. Themlal energy balance on tennInatLon of CPB was recorded prospectIvely in 53 sequential patients undergoing cardiac surgery for coronary artery bypass gJ aftmg and/or valve replacement Tympanic temperature was used as an accurate measure of core temperature' Results were analyzed using linear regression with statistical slgmficance taken as PsO,05, Results: Core temperature on tennination of CPB did not correlate with the degree of post-operative hypothem1ia as judged by time to rewann to 37,0°C (r'=0,002, P=O 651) and correlated poorly with the coldest post -operative tempcI'ature (r2=0,244, P=O,OII) Thennal energy balance provided a better indicator of the adequacy of rewanning than core tempelature, as judged by time to rewarm to 37,0°C (r2=0, 150, P=O,OLl) and coldest post-operative temperature (r2=0,333, P=O,OOOI), Discussion Thennal energy balance provides a better Indicator of the adequacy of rewanning from hypothennic CPB than core temperature measurements, Estin1ation of adequate rewarming from hypothennic CPB using thennal energy balance may be of use;: in minimizing the degree of post-operative hypothennia

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Reference: l. Sansome AJ. Apparatus for the real-time calculation of thermal energy flux during cardiopulmonary bypass, British Journal of Hospital Medicine 1989; 42: 494, 2, Davis FM, Barnes PK, Bailey JS, Aural thermometry during profound hypothermia, Anesthesia and Intensive Care 1981; 9 124-128,

A.42

CONVECTIVE WARMING OVERCOMES EFFECTS OF COOLING AFTER CARDIOPULMONARY BYPASS

Knowles PRo Moshal DC, Djaiani GN, Gopinath S. Duthie DJR

Papworth Hospital, Cambridge, CB3 8RE, UX

Introduction: During cardiac surgery with hypothcnnic cardiopulmonary bypass (CPB), strategies to rewann patients may be invalidated by heat loss from the chest and body after weaning from CPB, Convective wanning after surgery in the intensive care unit (ICU) may reverse these effects,

Methods: Heat transferred between body and CBP pump was measured III 23 patients undergoing myocardial revascularization [I], In ICU, patients were randomly allocated to be nursed with sheets and cotton blankets (Control) or convective Warming (WannTouch CareQuilt, Mallinckrodt, Northampton), Core temperatures were measured with thennocouples applied to tympanic membrane and nasopharynx and logged to computer every minute Linear regression analysis and the Mann-Whitney U test were used to assess statistical significance, which was accepted when P<O,05.

Results: On CPB, during cooling 608 (247 (SD» kJ were removed from the body and 850 (259) kJ replaced dunng wanning, Core temperatures were 37,2 (0.7)OC comIng off CPB and 34,6 (0,5)OC on admission to ICU, 58 (10) minutes later. In all patients, core temperatures fell no further after admission to ICU, The time to regain core temperature of 37°C was shorter (P=0,042) in the Wanning group, 160 (52) minutes (n=ll) than the Control group, 233 (103) minutes (n=12), The- time to core 37°C was related directly to the lowest core temperature (on admission to ICU) recorded in the Control group (P=0,007) but not the Wanning group, Time to extubation in ICU was related directly to the time from weaning from CPB to admission to ICU in the Control group (P=0,016), but not the Wanning group,

Discussion: Convective warming after hypothennlc CPB shortens the tin1e taken for core temperature to return [0 37°C It removes the influence of heat lost from the body after weaning from CPB, on time to return to core 37°C, and time to extubation, Heat transfer from and to the body during CPB could not be related to core temperature changes ill ICU, nor time to extubation. Strategies to prevent heat loss after weaning from CPB deserve further study,

Reference: I, Sansome AJ, Apparatus for the real-tin1e caJculauDn of thennal energy flux during cardiopulmonary bypass. Br J Hosp Med 1989: 42 494, 2, Sessler 01, Rubinstein EH, Eger EL Core temperature changes during N20 fentanyl and halothane 0, anesthesia. Anesthesiology 1987; 67: \37-139.

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