INVASIVE CENTRAL HEMODYNAMICS MONITORING IN ACUTEPERIOD OF SEVERE BURN TRAUMA AS A METHOD OF INTENSIVE CARE OPTIMIZATION

Samatov I.Yu., Veynberg A.L., Vereshchagin E.I.

Novosibirsk State Medical University, Novosibirsk State Regional Clinical Hospital, Novosibirsk, Russia

INVASIVE CENTRAL HEMODYNAMICS MONITORING IN ACUTEPERIOD OF SEVERE BURN TRAUMA AS A METHOD OF INTENSIVE CARE OPTIMIZATION

Development of burn shock (BS) in severe thermal injury is promoted by intense hypovolemia, acute toxemia and, as result, intense systemic inflammatory response. Therefore, burn shock is a unique combination of distributive and hypovolemic types of shock [1, 2] which manifests in view of decrease in circulating blood volume (CBV), decreasing pulmonary artery pressure (PAP), increasing peripheral vascular resistance and decreasing cardiac output (CO). In its turn, decreasing CO is associated with decreasing preload and increasing postload at the background of decreasing myocardial contractility [3]. A precise mechanism of decreasing mechanical function of the heart is still unclear. Multi-factorial nature of heart disease in BS [4, 5].
According to the features of pathogenesis of BS, the calculation of required volumes of infusion therapy is still actual. The known formulae of calculation do not consider the comorbid background and individual features of patients. The use of big dosages of narcotic analgetics worsens the problem [6]. As result, most authors indicate the necessity of correction of infusion therapy volumes, which are calculated with the classic formula by Parkland, often towards high increase in volumes [7, 8].
From other side, the increase in infusion therapy volumes increases the risk of respiratory and cardiac insufficiency, abdominal compartment syndrome and, finally, multiple organ dysfunction and increasing mortality at the background of altered pulmonary vascular permeability and decreasing myocardial contractile function.
One of the ways for decreasing the infusion therapy volumes (restrictive strategy of IT) is invasive monitoring of central hemodynamics and selection of the optimal scheme of use of vasopressor and inotropic agents with consideration of changes in hemodynamics [11]. In case of BS, one of most informative techniques is PiCCO-monitoring [12].
Objective – to determine the hemodynamic profile of severe burn shock (BS), and estimate abilities of PiCCO-monitoring for infusion therapy volume optimization and choice of vaso- and inotropic agent in treatment of BS.

MATERIALS AND METHODS

The study included 78 male and female patients at the age of 70, with total square of burns of degrees 2-3 > 40 %, who were admitted to burn ICU of Novosibirsk State Regional Clinical Hospital (Novosibirsk, Russia) in 2016-2017. The study corresponds to The Rules for Clinical Practice in the Russian Federation (the Order of Russian Health Ministry, 19 June 2003, No.266) and was approved by the ethical committee.
PiCCO-monitoring was performed with use of the thermodilution catheter (the approach through the femoral artery) for 78 patient with severe BS. PiCCO-monitoring was initiated 8.8 ± 2.7 hours after the moment of injury. With use of cold saline bolus and wave form analysis, the following values were monitored: myocardial contractility, volemic status, lung compliance, free fluid. The mean duration of PiCCO-monitoring was 8.3 ± 1.2 days.
ALV was performed according to indications. Most patients (92 %) received the vasopressor support with noradrenaline. If indicated, dobutamine was prescribed. For prevention of arrhythmogenic effect and increasing lactacidosis, the use of dobutamine was initiated with the dose of 1 µg/kg/min, with transition to the dose of 5 µg/kg/min within 60 minutes.  
The statistical analysis was conducted with use of STATISTICA 10. The critical level of significance was 0.05.

RESULTS

The results of PiCCO-monitoring in severe burn shock are in the table 1. The following changes were presented:
1. A reliable decrease in CI, SV and glycosilated phosphatidylinositol, also by means of two-fold decrease in left ventricle contractility.
2. Venous return decreased (evident decrease in global end-diastolic volume index, increasing variability of SV).
3. The common thing is an evident increase in systemic vascular resistance index with subsequent normalization in 48 hours.
4. There is a trend to increase in lung vascular permeability, free pulmonary water and, as result, evident worsening of respiratory biomechanics (two-fold decrease in lung compliance) and gas exchange.

In this situation, the issue of optimization of infusion therapy (rate/volume), namely restrictive strategy, is very important. The received results show the necessity of use of dobutamine as the agent, which increases the preload by means of venous tonic effect, and decreases the peripheral vascular resistance. Moreover, the reliable cardiac output in the first day, despite of massive infusion therapy, also testifies the necessity of dobutamine as the inotropic agent. Generally, the use of PiCCO-monitoring gives the possibility correct volumes of infusion, agents and dosages of vasopressor and inotrops, and, finally, decreases the volume of infusion therapy up to 3-3.5 ml × % of a burn × MT, with 2-2.5 l/day as absolute figures.

A CLINICAL CASE

The patient K., age of 50. The diagnosis: “A burn from hot water, IIIAB-IV degree, S = 55 %. Burn shock of degree 3. Alcohol intoxication”. He was admitted one hour after the injury. Objective status: conscious, hypothermia. RR – 16-18, harsh breathing in all regions. HR – 92 per min., AP – 165/90 mm Hg, CVP – negative, SpO2 = 96 %, PaO2/FiO2 = 387 mm Hg, pH – 7.28, BE – 7 mmol/l. Respiratory support was initiated at admission. One hour after admission, invasive hemodynamic monitoring was initiated. The following results were received: cardiac index – 2.6 l/min./m2, ejection fraction – 14 %, peripheral resistance index – 5858 dyn*sec*cm-5/m2.
On the basis of the received data, IT was initiated – 3 ml × BMI ×% of burn (11.250 ml). Simultaneously, considering the low CO and high total peripheral vascular resistance index (TPVRI), dobutamine was prescribed with initial dose of 1 µg/kg/min with transition to 5 µg/kg/min within an hour. Therefore, IT was 6,600 ml over 8 hours. Diuresis was 600 ml (1 ml/kg/h). Within 24 hours, IT volume was 12,400 with dieresis of 2,600 (1.5 ml/kg/h). On the second day, IT was reduced to 10,500, with dieresis of 2,200 or 1.2 ml/kg/h.
On the day 48 after admission, MAP decreased from 122 to 98 mm Hg. CVP increased from 0 to 4 mm Hg. In it turn, the cardiac index increased from 2.6 to 3.6; ejection fraction showed 1.6-fold increase (from 14 to 23 %). Peripheral resistance decreased three (!) times.
Therefore, the use of PiCCO-monitoring allowed the following: (1) selection of optimal volume and rate of infusion therapy, (2) substantiation of selection of dobutamine as the vaso- and inotropic agent, which is indicated in decreasing CO at the background of low preload and high peripheral resistance.                                     

DISCUSSION

A reliable decrease in cardiac output in the first day, despite of massive infusion therapy, testifies the necessity for the inotropic agent. The PiCCO-monitoring data of hemodynamic profile of severe BS shows the necessity for the inotropic agent, which increases the preload by means of venotonic effect, and decreases the postload. Among the available tools, only dobutamine fulfills these criteria.
According to the modern ideas of circulatory shock, a disorder of vascular tone is noted in all types of circulatory shock. Therefore, the use of vasopressor is the basis for restrictive strategy of infusion therapy that significantly decreases the volumes of infusion media, reduces the risk of organ injuries and improves the outcomes of critical conditions [13]. Moreover, the study by E. Rivers et al. (2001) showed that the simultaneous use of dobutamine and noradrenaline significantly improved the results of therapy in patients with septic shock. According to the received results, dobutamine was used 15 times more often in the group with favorable results as compared to the group with negative outcomes of treatment [14]. The attempts to explain these positive effects of dobutamine only by means of inotropic action did not give any reliable results. Therefore, these results can be considered as underestimated.
It is known that synthetic catecholamine is able to increase the cardiac output both in healthy volunteers and in patients with cardiac insufficiency. However action of dobutamine is not limited by influence on myocardium and can be increased by impact on vascular tone. One of the well-known experimental studies of artificial heart evaluated the effect on cardiac output. It was shown that dobutamine influenced on cardiac output and increased it from 7.0 +/- 1.8 to 8.2 +/- 1.8 l/min (!). Peripheral resistance decreased (p = 0.0001) from 1.224 +/- 559 to 745 +/- 317 dyn*s/cm2. Along with increase in venous return, the pressure increased evidently both in right and left atrium. These findings show that the dobutamine-induced increase in cardiac output happens not only by means of increasing contractility, but also due to the increase in venous return at the background of decreasing peripheral resistance [15].
In vitro experimental studies of dobutamine in isolated vessels also demonstrated the selective vasoconstrictor influence on veins (venoselective action). Moreover, venous return elevated more than 3 times after dobutamine use as compared to noradrenaline (49 +/- 10 ml vs. 14 +/-  6 ml correspondingly). Dobutamine showed the evident dose-dependent 2-3-fold increase in blood flow in epicardial regions and 1.5-2-fold increase in endocardial region of left ventricle. Conversely, constrictor influence on arteries was significantly less intense than noradrenaline and did not exceed 7 (low doses), 25 (middle) and 45 % (maximal) of efficiency of noradrenaline with different doses [16].
The results show the positive influence of dobutamine on venous tone, with decreasing preload at the background of stable cardiac output and AP. These effects can be exclusively important for burn shock. Regarding noradrenaline and other vasopressor, they realize the effect mainly on resistive vessels without influence on venous return. The volume of repository blood in venous region in septic or burn shock can exceed the volume of circulating blood. It is necessary to consider the increase in permeability of vessels of lesser circulation, and the increase in pulmonary free water. In such conditions, the high doses of crystalloids will make the negative influence on pulmonary gas exchange and will increase multiple organ disorders [13].
Therefore, PiCCO-monitoring and selection of dobutamine as the inotropic and venotonic agent allowed the restrictive strategy of infusion therapy in burn shock.

CONCLUSION

1. PiCCO-monitoring is indicated for patients with severe BS since it allows the individual approach to anti-shock measures and prevention of complications of massive infusion therapy.
2. The use of PiCCO-monitoring allowed the realization of restrictive strategy of infusion therapy in patients in the acutest and acute periods, and the decrease in infusion volume up to 3-3.5 ml × % of burn surface ×MT in the first day.
3. A proper analysis of PiCCO-monitoring in acute period of burn injury substantiated the necessity for use of dobutamine as the agent of both inotropic and venotonic action.

Information on financing and conflict of interests

The study was conducted without sponsorship.
The authors declare the absence of any clear or potential conflicts of interests relating to publication of this article.

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