Introduction: Lactate is a marker of hypoperfusion and predictor of major complications after cardiac surgery. Morbidity and mortality after cardiac surgery are directly related to the preoperative status as well as to anesthetic, surgical and postoperative factors. Maintainance of stable perfusion and with that appropriate hemodynamic goals is needed to improve outcomes. Continuous lactate and glucose monitoring with Eirus intravascular microdialysis system (Maquet Critical Care, Solna, Sweden) in a 65 year old heart transplant patient was used to guide postoperative management.

Case presentation: Male, 65 year old, 90kg patient was referred from a regional hospital where he was admitted with symptoms of congestive heart failure that were progressing rapidly. Dilatative cardiomyopathy was diagnosed 11 years prior, but patient failed to proceed with further diagnostic and therapeutic measures. He was diagnosed with diabetes two years ago, and his glycemia was adequately treated with oral antidiabetics. Patient was admitted to our ICU following a heart transplant with prior being placed on high urgency transplant list because of the rapid hemodynamic deterioration. Preoperative LVEF was estimated at 15%, with pulmonary vascular resistance (PVR) calculated to be 1,72 wu (137,39 dynes) and 2,91 wu (232,69 dynes) subsequently. At the time of surgery he was hypotensive on 10 mcg/kg/min of dobutamine (DBT) with progressive renal failure and associated anasarca. Preoperative cardiac catheterization revealed progession of the PVR from 1,72 to 2,91 wu. Noradrenaline (NA) infusion was included on and off to keep MAP above 60.

Operation and anesthetic proceeded uneventfully with total cold ischaemia time of 235’ and total time on extracorporeal circulation (ECC) 236’. Upon being admitted to our ICU he was hemodynamically stabile on isoprenaline 0,02mcg/kg/min with base levels of lactate of 1,33 but anaemic and with low PT so he received 2 doses of packed RBC and 3 doses of FFP and began to deteriorate so infusion of DBT was commenced at 7mcg/kg/min. Continuous diuretic therapy was replaced with CVVHDF the following day and continuous lactate monitoring with Eirus intravascular microdialysis system was initiated. Because of the progressive rise in lactate levels and accompanying lowering of the SvO2, inotropic support was switched to milrinone which at first gave some improvement to the perfusion and reduction of the lactate levels but the following day due to progressive hypotension NA had to be included and later adrenaline which resulted in higher MAP but also higher levels of lactate. Because of that infusion of adrenaline was stopped. On the third postoperative day there was further hemodynamic deterioration noticeable with rise of lactate levels, and low values of Svo2 so we decided to change inotropic support to levosimendan and increase fluid removal with CVVHDF from 180ml/h to 250ml/h. That finally resulted in constantly low lactate levels and after a few hours vasoconstrictor infusion colud be excluded. Patient was in that steady hemodynamic state weaned from ventilator and extubated on postoperative day 5, but was still dependant on CVVHDF. On postoperative day 8 he was weaned from all inotropic and vasoactive support and remained hemodynamically stable (Table 1)

Discussion: Heart transplant remains the mainstay therapy for end stage congestive heart failure patients. Due to shortage of donated organs and long transplant waiting lists but also in some cases because of the late presentation of these patients to transplant teams, they are often in very poor condition at the time of surgery. In global hypoperfusion, imbalance between systemic oxygen delivery and tissue oxygen consumption results in anaerobic metabolism and lactate production increases in cells as a result of anaerobic glycolysis. In this setting, lactate is a sensible marker of the magnitude of anaerobic metabolism. Hyperlactatemia has been associated with worse outcomes during circulatory failure, regardless of the presence of acidosis or anion gap disturbances. It is common in cardiac surgery and is always associated with poor outcome. A threshold of 3 mmol/l is considered hyperlactatemia. Eirus intravascular microdialysis system continually monitors blood glucose and lactate levels. The system requires only calibration for the glucose monitoring and values of the parameters are quite comparable with the laboratory findings.

Conclusion: With Eirus intravascular microdialysis system we gained a crucial parameter present continuously at the bedside which enables us to modify and target certain values associated with better care of the patient which results in better outcomes as well as reducing the amount of blood samples sent to the lab. In our case it enabled us to more readily change inotropic agent of choice to achieve adequate perfusion of all tissues.

References:

  1. Schierenbeck F. Nijsten, MWN, Franco-Cereceda A, Liska J. Introducing intravascular microdialysis for continuous lactate monitoring in patients undergoing cardiac surgery: a prospective observational study. Crit Care 2014;18(2):R56
  2. Hajjar LA, Almeida JP, Fukushima JT, Rhodes A, Vincent JL, Osawa EA et al. High lactate levels are predictors of major complications after cardiac surgery. J Thorac Cardiovasc Surg 2013,146:455–60.
  3. Maillet JM, Le Besnerais P, Cantoni M, Nataf P, Ruffenach A, Lessana A et al. Frequency, risk factors, and outcome of hyperlactatemia after cardiac surgery. Chest 2003,123:1361–6.
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Table 1. Continuous lactate and mixed venous oxygen saturation (SvO2) monitoring

Hours DAY 1 DAY 2 DAY 3 DAY 4 DAY 5
Lactate (mM/L) SvO2 (%) Lactate (mM/L) SvO2 (%) Lactate (mM/L) SvO2 (%) Lactate (mM/L) SvO2 (%) Lactate (mM/L) SvO2 (%)
2 DBT 7- 6- – – – – – 5- – – – – – 4- – 6-7

ISO 0,04-0,02- – – – – – – – – – – – – – – –

2,887 27 DBT5-3 EX

ISO 0,04- – – – – – – – – – – -0,02 – – – – –

MIL 0,75 – – – – – – – – – – – – – – 0,5 – – –

NA 0,1- – -0,2- – – – – – – – – – – – – – –

2,253 66 MIL 0,5 – – -0,35 – – – – – -0,5 – – – EX

ISO 0,02- 0,025—0,03- – – – – – – – –

NA 0,2 – – – – – – – – – – – – – – – – – – – – –

ADR 0,01- – EX

1,888 LEVOSIMENDAN0,2- 0,1- – – – – – – –

NA 0,16-0,14- – – – -0,1- – – – – – – – – –

1,761 LEVOSIM EX

NA 0,08 – – EX 0,1- – – – – 0,08- –

DBT 3 – – – – – – – – – – – – –

4 67 3,31 64 2,362 58 1,799 1,652
6 62 3,317 66 2,577 60 1,649 53 1,765 63
8 60 3,062 61 2,999 52 1,988 1,838
10 54 3,066 56 3,84 58 2,152 59 1,482 52
12 2,887 51 3,072 48 4,194 37 3,027 1,655
14 3,317 55 3,086 66 5,395 44 2,675 1,148 46
16 3,066 46 3,166 60 5,709 1,869 1,326
18 3,086 51 3,109 60 4,822 2,72 60 1,251 59
20 3,109 45 2,368 62 3,064 2,867 1,323
22 2,343 56 2,343 54 2,392 2,15 65 1,157 76
24 2,065 59 2,341 55 2,215 1,991 1,227

Abbreviation:

DBT – dobutamine (mcg/kg/min), ISO – isoproterenole (mcg/kg/min), MIL – milrinone (mcg/kg/min)

NA – noradrenaline (mcg/kg/min), ADR – adrenaline (mcg/kg/min), LEVOSIM – levosimendane (mcg/kg/min)

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