UNIVERSITY OF AGRICULTURAL SCIENCES AND VETERINARY MEDICINE

CLUJ-NAPOCA

DOCTORAL SCHOOL

VETERINARY MEDICINE FACULTY

COSMIN S. MUREŞAN

PHD THESIS SUMMARY

HEMODYNAMICS IN RESUSCITATED CARDIAC ARREST WITH

NEUROPROTECTION THROUGH THERAPEUTIC HYPOTHERMIA

AND MEMANTINE IN SWINE

SCIENTIFICAL ADVISOR

Prof. univ. Dr. LIVIU IOAN OANA

CLUJ-NAPOCA

2014

Table of contents

Keywords ...................................................................................................................... iii

1. Research motivation ..................................................................................................... iii

2. Thesis originality .......................................................................................................... iii

3. Research objectives ...................................................................................................... iii

4. Materials and method ................................................................................................... iv

5. Results and discussions ................................................................................................ vii

6. Conclusions and recommendations .............................................................................. xiv

iii

KEYWORDS: hemodynamic parameters, hemodynamic monitoring, cardiopulmonary arrest,

resuscitation, neuroprotection, therapeutic hypothermia, memantine.

1. RESEARCH MOTIVATION

Hemodynamic monitoring in cardiac arrest and resuscitation under neuroprotection is a

topical issue in emergency medicine and intensive care, which tries to bring more light on the

elucidation of pathophysiological mechanisms of cardiopulmonary arrest and consecutive

neuronal injury, on identification and update therapies with neuroprotective effects post

cardiopulmonary resuscitation, and on hemodynamic monitoring optimization and identification

of hemodynamic reference parameters in resuscitation and early goal-directed therapy.

In human medicine, post-resuscitation brain injury remains a professional challenge

requiring huge financial and human resources, and neuroprotective therapies devised or tested in

various preclinical studies and animal models still generate disappointing results. Controlled

hypothermia initiated post-resuscitation, although it has proven its neuroprotective effect in

comatose survivors of ventricular fibrillation, still raises some reticence about its usefulness on a

larger scale. In this context, the identification of new neuroprotective therapies or

complementary to hypothermia, once proven efficient, can be used in the usual clinical practice

(Gillies et al., 2010).

In veterinary medicine, the number of conclusive studies aimed at resuscitation, cerebral

ischemia and reperfusion neuronal injury, as well as hemodynamic monitoring in resuscitation

and post-resuscitation syndrome, is still very small. In addition, some of these studies are

performed on patients with often diversified pathology, others are experimental studies in

healthy patients, with hemodynamic parameters being chosen according to the addressed species,

the availability of monitoring equipment and preferences of the clinical staff involved, lacking an

overall hemodynamic monitoring which enables the identification of reference

methods/parameters and unequivocal demonstration of any correlation/non-correlations between

relevant parameters.

Thus it is necessary to further investigate the implementation of an updated strategy for

advanced hemodynamic monitoring during cardiopulmonary arrest and ischemia/reperfusion

injury in animals with experimental cardiac arrest, based on the findings of prospective clinical

trials.

2. THESIS ORIGINALITY

This study contributes to a better understanding of the evolution of hemodynamic

parameters during cardiopulmonary arrest, resuscitation and immediate post-resuscitation period,

potential correlations between them, the patient's response to resuscitation and influence of

neuroprotective therapy on the studied hemodynamic variables.

We believe that the findings in our study are significant, considering the following: the

study is based on cardiopulmonary arrest consecutive to induced ventricular fibrillation; there are

no differences between groups regarding CPR protocol or resuscitation medication; an essential

component of the study is the neuroprotection protocol (hypothermia and memantine); different

approach of categories of evaluated hemodynamic parameters; hemodynamic assessment from

post-ROSC to 120 minutes, etc.

3. RESEARCH OBJECTIVES

This paper aims to assess hemodynamic parameters during cardiac arrest, resuscitation

with neuroprotection, and during the return to spontaneous circulation, based on an experimental

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protocol of cardiac arrest by induction of ventricular fibrillation using an electric current of 50

Hz.

The study has the following objectives: to assess the dynamics of monitored

hemodynamic parameters; to identify potential correlations between monitored hemodynamic

parameters; to evaluate the influence of neuroprotection medication on monitored parameters.

To accomplish the objectives we monitored hemodynamic parameters using the

following classification (Edwards, 2002; Galli et al., 2000; Lopez-Herce et al., 2011a, 2011b;

LiDCO, 2003):

Global hemodynamic parameters – heart rate (HR), mean arterial pressure (MAP), central

venous pressure (CVP), pulmonary capillary wedge pressure (PWPC), cardiac output

(CO), stroke volume (SV), stroke volume variation (SVV), systemic vascular resistance

(SVR).

Oxygenation status parameters – partial pressure of oxygen (PO2) (arterial, venous and

jugular bulb blood), oxygen delivery (DO2), hematocrit (HCT – arterial, venous and

jugular bulb blood).

Acid-base status parameters – pH, base excess (BE(B)), bicarbonate (HCO3) and the

partial pressure of carbon dioxide (PCO2) – in arterial, venous and jugular bulb blood,

and the end tidal carbon dioxide (EtCO2).

Metabolic and tissue perfusion status parameters – glucose (GLU), serum potassium

(K+), lactatemia (LAC) and ionized calcium (Ca++) – in arterial, venous and jugular bulb

blood.

Hemodynamic parameters were assessed and recorded during four consecutive periods:

the period of stability (basal), during ventricular fibrillation (VF), during resuscitation (CPR) and

post resuscitation period (post-ROSC).

4. MATERIALS AND METHODS

Biological materials. The animals studied were the 25 pigs (Landrace/Large-White),

male and female, with an average weight of 65 ± 5 kg, all from the same breeder, a pig farm

from Cluj county. The pigs were brought to FMV Cluj-Napoca three days before the experiment

and hospitalized in separate boxes, with food and water regime ad libitum (fed a commercial diet

similar to that fed in the farm), and a normal lighting regimen (compliance of the day and night

cycle).

Equipment. Draeger Infinity Delta multiparameter monitor and Draeger Evita 1

ventilator (Dragerwerk AG Lubeck, Germany); Vigileo monitor, used with FloTrac sensor

(Edwards Life Sciences, USA); Primedic Defi Monitor XD1 defibrillator (Metrax GmbH,

Rottweil, Germany); Gem Premier 3000 blood gas and electrolyte analyzer (Instrumentation

Laboratory Company, Lexington, MA, USA); Infusomat B Braun FM and Injectomat B Braun

Compact S (B Braun Melsungen AG, Melsungen, Germany); Nikon D40, with a 18-55 mm

objective (Japan).

Working method. The experimental protocol was reviewed and approved for the project

PN-II/09.10.2007, „The development through interdisciplinary research of a new drug therapy

meant to ensure neuroprotection in cerebral ischemia (NEUROPROTER)” by the Committee on

Bioethics of UMF Iuliu Haţieganu Cluj-Napoca, and was in accordance with the European

legislation and also with the international guidelines on animal welfare involved in experimental

procedures, and is based on similar protocols found in several studies (Brücken et al., 2010;

Jeung et al., 2011; Wu et al., 2008; Koudouna et al., 2007; Liao et al., 2010; Lopez-Herce et al.,

2011a; 2011b; Schratter et al., 2010; Schwarzl et al., 2011; Xanthos et al., 2007a; 2007b; 2010;

Yannopoulos et al., 2011). Before being studied, the animals were diagnosed as clinically

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healthy on a prior clinical consultation. 12 hours before the experiment they were subjected to

fasting, fluid administration remaining unchanged.

Anesthesia protocol. The anesthetic protocol used consisted in the administration of

atropine (0.04 mg/kg IM) and azaperone (4 mg kg IM) (premedication); propofol (3 mg/kg) i.v.

bolus (induction of anesthesia); sufentanil (0.2-0.3 mcg/kg IV every 20-30 minutes), Tracrium

(0.6 ml/kg IV every 30 minutes) and propofol (8-10 mg/kg/h) (maintenance). Ventilation was

maintained in a controlled manner with TV of 12-15 ml/kg I/E ratio of 2.1, 21% FiO2,

respiratory rate being adjusted to maintain EtCO2 between 30-40 mmHg and PaCO2 between 35-

45 mmHg.

Auxiliary protocol. Fluid therapy consisted of Hartmann's solution at a dose of 30 ml/kg

IV during the first hour, then 10 ml/kg/h, with interruption during ventricular fibrillation. 15 min.

before inducing the cardiac arrest all animals received heparin in order to prevent the potential

risk of thromboembolism.

Catheter placement. The marginal ear vein was catheterized with a 20G venous

catheter. The right carotid artery was surgically isolated and catheterized with a 20G arterial

catheter for continuous assessment of blood pressure, cardiac output and cardiac output derived

parameters. The pulmonary artery was catheterized with a 7F Swan-Ganz catheter, introduced

through the right jugular vein, right atrium, right ventricle, pulmonary artery and finally the

pulmonary capillary, the catheter position being monitored by visualizing the characteristic

waves on the monitor screen. For assessing central venous pressure, a central venous catheter

was inserted into the right jugular vein. The right internal jugular vein was also catheterized as

close as possible to the jugular bulb with a 22G intravenous catheter for blood gas and

electrolyte sampling. Bladder catheterization was performed using a urinary probe.

Monitoring of hemodynamic parameters. The following hemodynamic parameters

were monitored: HR, MAP, CVP, PWPC, CO, SV, SVV, SVR, PO2, DO2, HCT, pH, BE(B),

HCO3-, PCO2, EtCO2, GLU, K+, LAC and Ca++. Additionally, for quality purposes of the

experimental protocol, the following parameters were also monitored until patient extubation:

ECG in DII derivation, SpO2 and body temperature. After completing implementation of

catheters and monitoring, each animal was allowed to stabilize for 20 minutes before recording

baseline hemodynamic variables.

Registration of hemodynamic parameters was performed according to the following

protocol: baseline, 3 minutes from resuscitation; 5, 15, 30, 60 minutes and 120 minutes after

ROSC. The order of registration of these parameters was not random. For every measurement

set, blood sampling was performed after recording parameters on the screens of both monitors.

Blood samples for the analysis of blood gases, electrolytes and lactate were obtained at the same

time from the carotid artery, pulmonary artery and jugular bulb, according to the same protocol

applied for the rest of the hemodynamic variables. Analysis of blood gases, electrolytes, glucose

and lactate was performed immediately after blood sampling.

Methodology for the induction of cardiac arrest. Cardiac arrest was achieved by

induction of ventricular fibrillation (VF) by applying an alternating current of 40-60 V at a

frequency of 50 Hz, by means of two subcutaneous electrodes. The duration of cardiac arrest was

8 minutes, while mechanical ventilation and fluid therapy were stopped and the animals were left

without any treatment. The presence of ventricular fibrillation was confirmed by visualization of

the ECG characteristic waves and a significant drop in blood pressure.

Resuscitation protocol. After eight minutes of VF, resuscitation maneuvers were

initiated according to the human medicine ALS protocol. The CPCR protocol consisted of

manual external cardiac massage (standard) – chest compressions – at a rate of 100 per minute,

with the length of compression being equal to full relaxation, and the depth of compressions on

the anterior-posterior diameter being 25% of the height of the thorax, and controlled ventilation,

with a frequency of seven breaths per minute, 100% FiO2, and 30/2 ratio of chest

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compressions/breaths. After one minute of CPR, an IV bolus of vasopressin (0.5 IU/kg) was

administered. After five minutes of CPCR the patient was defibrillated by applying an electric

biphasic shock of 150 J. The success of resuscitation, ROSC (restoration of spontaneous

circulation), was considered a restoration of heart rate with an invasive SBP greater than 50-60

mmHg for more than 10 consecutive minutes. If ROSC was not achieved after the first shock, we

continued the CPCR with a minute of external cardiac massage and two electric shocks 150 J,

followed by another 2 minutes of ECM, a bolus of 30 mcg of epinephrine (0.02 mg/ kg) and after

another minute of ECM, two consecutive shocks of 200 J were applied. The absence of ROSC

after these shocks defines inefficiency of resuscitation. The resuscitation protocol was stopped

when ROSC was achieved or after 20 minutes of ineffective resuscitation. After restoring ROSC,

ventilation (i.e. maintaining PaCO2 and EtCO2 values before VF) fluid therapy and

hemodynamic monitoring were restarted. In addition, FiO2 was gradually decreased, so that after

60 minutes after ROSC, this parameter was reduced to 30%, and later maintained until patient

extubation. If SBP was less than 70 mmHg after ROSC, inotropic support with dobutamine was

initiated. At the end of the monitoring period extubation was performed. Before being transferred

to the box, each animal was observed for 20 minutes under SpO2 monitoring to ensure adequate

spontaneous breathing.

Neuroprotection protocol. Neuroprotection protocol was achieved through two distinct

methods, therapeutic hypothermia and administration of memantine.

Therapeutic hypothermia. Therapeutic hypothermia (32-34°C) (mild hypothermia), a

classical method in neuroprotection, was induced and maintained by a combination of two

methods, the endovascular method and the surface cooling method. The internal endovascular

method – "endovascular cooling" – was carried out by rapid intravenous bolus administration

(15-30 ml/kg) of cold crystalloid solution (Hartmann's solution at 4°C). The external method –

"surface cooling" – was carried out by placing cold compresses (wet towels) and polythene ice

packs on the ventral and lateral sides of the neck, thorax and abdomen (Gillies et al., 2010). The

duration of therapeutic hypothermia was 12 hours, and it was established in a single lot, starting

in the 1st minute post-ROSC. Throughout its length, the internal body temperature was measured

continuously at esophagus level (the lower third). Prevention of shivering was performed by

anesthetic management, neuromuscular blocking being added as needed. Finally, the reheating

procedure has been carried out by passive methods using hot blankets, and the room temperature

was adjusted to 22-23°C.

Administration of memantine. Two lots received memantine for neuroprotection – 5

mg/kg and 10 mg/kg i.v. in the 1st minute post-ROSC (in the Swan-Ganz introducer catheter).

Studied lots

Lot I (5 pigs) – anesthesia without cardiac arrest, without CPCR, without

neuroprotection;

Lot II (5 pigs) – anesthesia, cardiac arrest, CPCR, without neuroprotection;

Lot III (5 pigs) – anesthesia, cardiac arrest, CPCR, memantine 10 mg/kg;

Lot IV (5 pigs) – anesthesia, cardiac arrest, CPCR, therapeutic hypothermia;

Lot V (5 pigs) – anesthesia, cardiac arrest, CPCR, memantine 5 mg/kg.

After complete registration of the studied hemodynamic variables, animals that achieved

ROSC were kept alive for three days, during which they were examined neurologically at 24, 48

and 72 hours. Daily therapeutic protocol during this period consisted of antibiotic and analgesic/

anti-inflammatory drugs; diet and fluid intake remained unchanged. At the end of the

experiment, the animals were euthanized and necropsied, with sampling for histopathologic

examination.

Statistical analysis of the results. Recorded hemodynamic variables are presented as

mean ± SD. As we found in the literature only separate assessments of the dynamics and

potential correlations of blood variables (arterial, central venous, jugular bulb), in our study we

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preferred the combined appraisal, and therefore we introduced these hemodynamic variables in

the statistical analysis as an arithmetic mean.

Statistical interpretation of the test results was based on ANOVA (Analysis of Variance

One-way) and Tuckey Kramer for the dynamic evolution and the comparative evolution of

monitored hemodynamic parameters. A p value of <0.001 indicates highly significant differences

(marked with ***); a p value of <0.01 indicates significant differences (marked with **); a p

value of <0.05 was indicative for significant differences (marked with *); a p value of ≥0.05 was

indicative for differences statistically insignificant (marked with ns).

To assess the relationship between recorded hemodynamic variables we used Pearson's

correlation (Pearson Product Moment Correlation Coefficient (r) – correlation coefficient). A

correlation coefficient equal to 0 was an indicator for the absence of linear relationship, while a

correlation coefficient equal to 1 (±) has been an indicator for a perfect linear relationship

(positive/ negative). Correlation coefficient values between 0 and 0.3 (±) are indicators for a low

linear relationship (positive/negative); r values between 0.3 and 0.7 (±) were indicators for

moderate linear relationship (positive/negative) (significant error of prediction); r values between

0.7 and 0.9 (±) were indicators for a strong linear relationship (positive/negative) (moderate error

of prediction); correlation coefficient values between 0.9 and 1.0 (±) were indicators for a very

strong linear relationship (positive/negative) (with good accuracy of prediction) (Marion, 2004;

Stockburger, 1996; Dean et Illowsky, 2012). Additionally, for a correct interpretation of the

correlation coefficient we determined the linear regression between the same hemodynamic

variables by calculating the coefficient of determination (R2) (Brown, 2003; Dean et Illowsky,

2012; Roberts, 2014).

5. RESULTS AND DISCUSSIONS

DYNAMIC EVOLUTION OF HEMODYNAMIC PARAMETERS

Global hemodynamic parameters. In the control group, heart rate, blood pressure,

central venous pressure and pulmonary capillary wedge pressure remained relatively constant

throughout the experiment. Cardiac output and stroke volume were constant around 6 L/min. and

65 mL/beat. In addition, stroke volume variation had a similar pattern. In the resuscitated groups,

compared to basal period, heart rate dropped to 0 during the ventricular fibrillation period (Fig.

1), and simultaneously extreme hypotension was noticed (10% of basal value). During

resuscitation, heart rate increased sharply, as determined practically by cardiac massage, with

concomitant arterial hypotension (maximum 50% of basal value), even if resuscitation was

instituted accordingly. During the return of spontaneous circulation we recorded tachycardia,

heart rate values being the highest in the first 30 minutes, after which they had a tendency to

decrease and normalize. After 5 minutes of ROSC we observed a peak of hypertension, with a

subsequent trend of normalization, and at the end of the experiment the mean arterial pressure

was slightly increased compared to baseline. Central venous pressure and pulmonary capillary

wedge pressure were increased within 30 min after ROSC, after which there was a tendency to

normalization, baseline values being the smallest recorded. Due to technical reasons, CVP was

not recorded during ventricular fibrillation and CPR. The highest cardiac output was recorded in

resuscitated lots immediately after return to spontaneous circulation (5-15 min); at the end of the

experiment CO was lower than baseline; post-ROSC stroke volume variation had a downward

trend towards the end of the monitoring period, the values during ROSC 120 being superior to

baseline. However, during ventricular fibrillation and resuscitation periods, values generated by

the Vigileo monitor for CO, SV and SVV were identical with basal values, since the monitor

sensor could not detect an interpretable pulse wave, and we therefore believe that they do not

reflect the clinical reality of those moments, and were erroneously overestimated. Systemic

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vascular resistance was decreased during baseline and had a tendency to increase towards 120

min. post-ROSC; its values were not influenced by resuscitation.

Acid-base status parameters. In the control group, acid-base status parameters had a

linear trend which was constant throughout the experimental period - the base excess between

8.1 mmol/L, SD = 1.89 and 9.35 mmol/L, SD = 3.11; end-tidal carbon dioxide between 24.33

mmHg, SD = 1.08 and 29 mmHg, SD = 1.41; blood bicarbonate concentration between 31.45

mmol/L (SD = 1.7) and 33.74 mmol/L (SD = 3.87); partial pressure of carbon dioxide in the

range of 35.77 mmHg (SD = 3.16) and 44 mmHg (SD = 14.07); blood pH in the range of 7.48

(SD = 0.07) and 7.53 (SD = 0.02, 0.03, 0.005). In the lots where we induced ventricular

fibrillation, as compared to the basal values base excess and blood bicarbonate concentrations

were normal, but they decreased during CPR and return to spontaneous circulation, suggesting a

base deficit (metabolic compensation). Base excess had a negative peak 15 minutes after ROSC

(-6.1, SD = 0.73 and -10.32, SD = 4.1), and, starting 30 minutes post-ROSC, HCO3- and BE(B)

had recorded an upward trend in all resuscitated lots; as a whole, the recorded values for these

two parameters were lower than baseline (statistically insignificant) at the end of monitoring

(Fig. 2). End-tidal carbon dioxide decreased sharply up to 0 during ventricular fibrillation, then

rose sharply during resuscitation, reaching values of nearly 50% of baseline values, and

continued to grow during ROSC 5, when we registered values approximately equal to baseline.

Maximum values were found 15 minutes after return to spontaneous circulation, subsequently

we recorded a downward slope, where values recorded at the end of the monitoring period were

being almost similar to baseline. Basically EtCO2 showed an inversely proportional relationship

to BE(B) 15 minutes after return to spontaneous circulation. Partial pressure of carbon dioxide

showed almost identical values at the beginning and end of monitoring in resuscitated groups,

being increased in 15 minutes after ROSC. Basically PCO2 and EtCO2 were maximally increased

at the same time, 15 minutes after ROSC. Compared to baseline, the blood pH in resuscitated

lots decreased until 15 minutes after return to spontaneous circulation, at which point metabolic

acidosis was maximal. Subsequently it has registered an improvement, baseline pH and final pH

being quite similar.

Oxygenation status parameters. In the control group, oxygenation status parameters

had a linear trend throughout the experimental period. Oxygen delivery was between 661

mL/min (SD = 18.7) and 843 mL/min (SD = 180.71); partial pressure of oxygen in the blood

between 109.44 and 256.33 mmHg and hematocrit – between 25.44% (SD = 2.13) and 27.33%

(SD = 3.52). In resuscitated groups, during VF, these parameters were not registered. During

CPR, compared to baseline, PO2 and HCT increased. DO2 was maximally increased up to 5-15

minutes after return to spontaneous circulation, after which the declining trend was gradual-

minimum values were found at the end of the monitoring period (Fig. 3). Generally, the PO2

registered an increasing trend from baseline up to 60 minutes post-ROSC (hyperoxia), followed

by a sharp decline until the end of the monitoring period, ROSC 120 values did remain higher

than baseline. DO2 and PO2 were directly influenced by FiO2 evolution during resuscitation,

respectively 100% during CPR and then gradually reduced to 30% at 60 minutes. HCT in

resuscitated lots increased from baseline until 5 minutes post-ROSC, followed by a slow decline

within the next 60 minutes, the final values (ROSC 120) remaining similar to baseline.

Metabolism and tissue perfusion status parameters. In the control group, the

metabolic and tissue perfusion status markers remained constant throughout the experiment.

Glycaemia – between 5.22 mmol/L (SD = 0.92) and 6.05 mmol/L (SD = 1.84); blood lactate –

from 1.92 mmol/L (SD = 0.43) to 3.15 mmol/L (SD = 0.67); blood potassium – between 3.67

mmol/L (SD = 0.05) and 3.83 mmol/L (SD = 0.16); ionized calcium – between 1.37 mmol/L and

1.39 mmol/L during baseline. In resuscitated lots, compared to baseline, glycaemia and

lactatemia increased during CPR, and potassium levels reached a maximum peak. Post-ROSC,

blood glucose peaked at 5 minutes, blood lactate only after 5-15 minutes (Fig. 4), while

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potassium levels returned to baseline 15 minutes after return to spontaneous circulation. Serum

calcium was minimal 60 minutes after ROSC, but the evolution of this parameter was still

modest compared with other metabolic and tissue perfusion parameters.

CORRELATIONS BETWEEN HEMODYNAMIC PARAMETERS

Correlations between the global hemodynamic parameters. In the five studied lots,

few correlations were observed between monitored global hemodynamic parameters. Thus, we

identified a strong positive correlation between heart rate and mean arterial pressure in terms of

hemodynamic stability, but the correlation was inconstant in terms of hemodynamic instability.

In groups resuscitated under neuroprotection, we identified a strong positive correlation between

heart rate and cardiac output. Only in the lots resuscitated with memantine we have identified a

strong negative correlation between systemic vascular resistance and two other variables – heart

rate and cardiac output. In the group with hypothermia, we have identified a strong positive

correlation between cardiac output and mean arterial pressure, which remained very strong in the

group with memantine 10 mg/ kg, but not in the other groups. Cardiac output was not correlated

with global pressure parameters, such as central venous pressure and pulmonary capillary wedge

pressure.

Correlations between acid-base status parameters. Among the acid-base parameters

there are few strong correlations. In all groups we identified a strong positive correlation

between blood base excess and bicarbonate, both in terms of hemodynamic stability and

instability. We observed that during hemodynamic stability conditions, there was a strong

positive correlation between the partial pressure of carbon dioxide and base excess (blood), and

between partial pressure of carbon dioxide and blood bicarbonate, but the correlation becomes

strongly negative in all groups resuscitated under neuroprotection. Inconstantly, in the

hypothermic group and the group with memantine 10 mg/kg we found a strong positive

correlation between pH and base excess, and respectively bicarbonate. Only in the lots treated

with memantine, and in no other lots, we identified a strong positive correlation between the

partial pressure of carbon dioxide in the blood and the end-tidal carbon dioxide.

Correlations between oxygenation status parameters. Within the parameters of

oxygenation status there are no strong correlations. Inconstantly, in the hypothermic group and

the group with memantine 10 mg/kg we found a strong positive correlation between oxygen

delivery and hematocrit.

Correlations between metabolism and tissue perfusion status parameters. In the

metabolism and tissue perfusion status parameters there are little correlations. In all resuscitated

lots (with/without neuroprotection) we identified a strong positive correlation between blood

glucose and lactate.

Correlations between global hemodynamic parameters, acid-base status

parameters, oxygenation status parameters and metabolic and tissue perfusion status

parameters. Overall, taking into account all hemodynamic parameters in all lots studied, we

identified potential correlations which describes from a pathophysiological point of view

cardiopulmonary arrest, resuscitation period and the return to spontaneous circulation.

Between global hemodynamic variables and oxygenation status variables, we found a

strong positive correlation only between cardiac output and oxygen delivery in terms of

hemodynamic stability, which becomes very strong in the groups resuscitated under

neuroprotection.

In all 4 resuscitated lots, we noticed a strong positive correlation between heart rate and

glycaemia, a strong negative correlation between blood base excess and blood lactate (Fig. 5, 6,

7, 8), and a very strong negative correlation between hydrogen ion concentration and blood

lactate. Additionally, in terms of hemodynamic stability, we revealed a strong negative

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correlation between heart rate and blood lactate, which becomes very strong positive correlation

in resuscitated lots, except the hypothermic lot where this relationship was not maintained. We

identified a strong positive correlation between base excess and glycaemia, and between blood

bicarbonate and glycaemia in the lot without cardiac arrest and without neuroprotection (during

hemodynamic stability), but this correlation becomes reversed (negative) in all resuscitated lots.

Comparing hemodynamic variables in resuscitated lots, we found a strong negative

correlation between heart rate and base excess (blood), which becomes very strong in the groups

resuscitated under memantine. This correlation is not maintained in the group with hypothermia.

Also in resuscitated lots we identified a strong positive correlation between glucose and oxygen

delivery, between blood lactate and oxygen delivery, and a very strong correlation between heart

rate and oxygen delivery with one exception – the lot with therapeutic hypothermia. Similarly,

we found a strong negative correlation between blood base excess and oxygen delivery, between

bicarbonate ion concentration and oxygen delivery, and a very strong correlation between blood

bicarbonate concentration and heart rate in all resuscitated lots, but with the same exception – the

lot with hypothermia.

In lots resuscitated under neuroprotection, we have identified a strong positive correlation

only between cardiac output and glycaemia, and between the partial pressure of carbon dioxide

and blood lactate.

Only in the lots with memantine we noticed a strong positive correlation between heart

rate and end-tidal carbon dioxide, between cardiac output and blood lactate, and between oxygen

delivery and end-tidal carbon dioxide, but a strong negative correlation between cardiac output

and base excess and between cardiac output and blood bicarbonate concentration.

Through the fact that we found only a few correlations between monitored hemodynamic

parameters, our study confirms on the one hand the possibility that neuroprotective (hypothermia

and memantine) and resuscitation (epinephrine and vasopressin) medication might influence

hemodynamics. On the other hand, we must bear in mind that cardiopulmonary arrest and

resuscitation represent, in essence, a state of shock and consecutive hemodynamic instability,

with altered dynamics and interrelationships between hemodynamic variables, supplemented by

the influence of other external factors such as artificial ventilation, cardiac massage, etc.

Additionally, we mention the possibility of a correlation between two hemodynamic variables

without a causal relationship. On the other hand, the absence of monitored hemodynamic

parameter values during certain moments (especially VF) may mask or influence the dynamics

and interrelations between certain variables studied in this thesis. However, we believe that

further studies are needed to evaluate these hypotheses.

NEUROPROTECTIVE MEDICATION INFLUENCE ON MONITORED PARAMETERS

From a hemodynamic point of view, the neuroprotection strategy used yielded results that

are comparable to those from previous studies. Compared with other lots, hypothermia resulted

in lower heart rate and increased mean blood pressure starting from 5 minutes from the return to

spontaneous circulation. Throughout ROSC period, cardiac output and stroke volume variability

were more constant, and systemic vascular resistance was increased, the highest values being

found 5 to 30 minutes from ROSC. Hypothermia triggered the lowest values of EtCO2 and PCO2

of all resuscitated groups and less severe degree of metabolic acidosis, hyperlactataemia being

the lowest among all groups (15 to 30 minutes post-ROSC). Throughout CPR and ROSC,

hematocrit had the lowest values in hypothermic pigs, and compared with the other resuscitated

lots oxygen delivery was lower within 15-60 post-ROSC.

Resuscitation under memantine involved elevated heart rates post-ROSC, and with the

dose of 10 mg/ kg, cardiac output and stroke volume peaked (compared to other resuscitated

lots); base excess had the lowest values within 5-30 minutes post-ROSC. Metabolic acidosis was

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the most serious in the range of 5-30 min post-ROSC, with an elevated lactate level when

compared with the hypothermic lot. Only in the memantine receiving lots we identified a strong

positive correlation between the partial pressure of carbon dioxide and end-tidal carbon dioxide,

strong positive correlations between heart rate and end-tidal carbon dioxide, between cardiac

output and blood lactate and between the oxygen delivery and the end-tidal carbon dioxide. Also

we identified strong negative correlations between cardiac output and base excess, and between

cardiac output and bicarbonate ion concentration.

The hypothermic lot was an exception for many correlations. Thus, among the

resuscitated lots we identified strong positive correlations between glycaemia and oxygen

delivery, between blood lactate and oxygen delivery, as well as a very strong correlation between

heart rate and oxygen delivery in lots with hemodynamic instability, with one exception – the lot

with therapeutic hypothermia. Similarly, we found strong negative correlations between blood

base excess and oxygen delivery, between bicarbonate ion concentration and oxygen delivery,

and a very strong correlation between blood bicarbonate ion concentration and heart rate in lots

with hemodynamic instability with the same exception, the lot resuscitated with therapeutic

hypothermia.

Potential limitations of the study. This study also has some limitations. First, the rather

small number of pigs per lot, which still constitutes minimum requirements in terms of statistics,

to which the costs of related material are added. The experiment was based on healthy pigs,

where we induced VF to study hemodynamics in resuscitation and post resuscitation with

neuroprotection, in contrast to patients entering cardiac arrest consecutive to underlying

pathologies, who present by default pathophysiological particularities and specific hemodynamic

particularities. On the other hand, such a study provides a basis for comparison targeting the

development of hemodynamic variables in patients with specific pathologies, and simultaneously

the possibility of hemodynamic guidance of therapeutic maneuvers. Anesthesia and controlled

ventilation may influence certain hemodynamic parameters values, leading to significant changes

compared to normal patients, unsedated and with spontaneous breathing. However, they

represent an important goal to meet welfare of animals used in these experimental studies. We

have not reviewed CPP (coronary perfusion pressure) although other studies have successfully

rated this parameter, but our study did not initially propose to study hemodynamic differences

between successfully resuscitated animals versus unsuccessfully resuscitated animals (animals

with no return to spontaneous circulation). We evaluated the dynamics and potential correlations

of blood variables (arterial, central venous, jugular bulb) as average, and from a statistical point

of view we consider that it is necessary to supplement the research with a separate distinct

assessment. We used a method of determining cardiac output validated only in humans

(FloTrac/Vigileo), and still not yet validated in pigs, therefore we believe that it would be

necessary that values obtained by this method should be compared with a validated method (e.g.

transpulmonary thermodilution or LiDCO). However, given that cardiovascular physiology in

pigs is similar to the human model, we believe that the values obtained in this study may be

considered.

xii

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xiii

Exam

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4

xiv

6. CONCLUSIONS AND RECOMMENDATIONS

Conclusions regarding dynamic evaluation of monitored hemodynamic parameters

The studied hemodynamic parameters had a constant linear evolution during all four pre-

established experimental moments in the control group, and only during baseline in the

four resuscitated lots.

Ventricular fibrillation period was characterized by the collapse of blood flow

parameters – heart rate was 0, extreme arterial hypotension (10% of baseline value), low

cardiac output and end-tidal carbon dioxide abruptly decreasing to 0.

Resuscitation period involved heart rate and cardiac output dependent on resuscitation

maneuvers, arterial hypotension (maximum 50% of baseline value), decreased base

excess and bicarbonate, increasing end-tidal carbon dioxide (nearly to 50% of baseline

values), increased partial pressure of oxygen, glycaemia, hematocrit, hyperlactatemia as

well as hyperkalemia.

The return to spontaneous circulation period was characterized by an initial growth of

most global hemodynamic parameters – tachycardia and hypertension, cardiac output,

central venous pressure and pulmonary capillary wedge pressure were all increased –

after which the trend was towards normalization.

15 minutes post-ROSC base deficit was greatly accentuated (15 minutes after ROSC) and

bicarbonate ion concentration minimal, and starting with 30 minutes post-ROSC their

evolution was ascending and became normal at the end of monitoring.

Immediately post-ROSC mixed acidosis (metabolic and respiratory) was severe, and end-

tidal carbon dioxide and partial pressure of carbon dioxide were elevated, but both

become normal after 120 minutes post-ROSC.

Partial pressure of oxygen and oxygen delivery were highly elevated (hyperoxia

consecutive 100% FiO2, gradual decreased to 30%); hematocrit, glycaemia and

lactatemia were increased immediate post-ROSC, with a decreasing trend towards

normalization after 120 minutes.

15 minutes after ROSC, there was an inverse proportional relationship between EtCO2

and BE(B). At the same time, PCO2 and EtCO2 peaked, and metabolic acidosis was the

most severe.

Although still not validated in pigs, Vigileo FloTrac method has potential for an accurate

assessment of CO in terms of hemodynamic stability; under extreme hemodynamic

instability – ventricular fibrillation and then resuscitation – it is less accurate, since it is

virtually impossible to assess the arterial pressure wave.

Conclusions regarding correlations between monitored hemodynamic parameters

During ventricullar fibrillation, CPR and ROSC periods, significant correlations were

disturbed.

Among monitored global hemodynamic parameters, only heart rate and mean arterial

pressure were positively correlated in terms of hemodynamic stability.

Between acid-base parameters only base excess and blood bicarbonate correlate

positively under hemodynamic stability and also instability; however, most existing

correlations during hemodynamic stability conditions were not maintained during

ventricular fibrillation, resuscitation and return to spontaneous circulation.

We have not identified correlations within the oxygenation status parameters.

xv

Within metabolic and tissue perfusion parameters there was only one strong positive

correlation – blood glucose and blood lactate in all resuscitated lots (with and without

neuroprotection).

Overall, taking into account all studied hemodynamic parameters in the four periods, we

identified few strong correlations:

Between cardiac output and oxygen delivery – a strong positive correlation in conditions

of hemodynamic stability, which became very strong in the groups resuscitated under

neuroprotection.

In all four resuscitated lots – strong negative correlations between blood lactate and base

excess, as well as with bicarbonate ion concentration.

In lots resuscitated with neuroprotection – strong positive correlations between cardiac

output and glycaemia, and between partial pressure of carbon dioxide and blood lactate.

Conclusions regarding the influence of neuroprotective medication on monitored

parameters

The dynamic of assessed variables and the identified correlations were influenced by

neuroprotective medication (therapeutic hypothermia and memantine).

Therapeutic hypothermia had a beneficial effect on the development of studied

hemodynamic variables, favorably influencing the evolution of resuscitated animals.

Therapeutic hypothermia influenced the evolution of hemodynamic parameters, leading

to a change of relations between them (correlations are not maintained).

Resuscitation under memantine directly influenced cardiac activity (positive

cronotropism, increased cardiac output and stroke volume), emphasized blood lactate

level and exacerbated metabolic acidosis immediately post-ROSC.

Because at certain moments (especially during induced ventricular fibrillation), due to

technical reasons, some hemodynamic parameters were not recorded, we cannot exclude the

possibility of a partial interpretation from a statistical point of view.

We consider it necessary to continue studies on hemodynamics during resuscitation in

order to confirm the results and to evaluation of these hypotheses.

Recommendations. Since we have identified only a few strong correlations (with good

predictive accuracy) between studied hemodynamic parameters in the four distinct periods, we

recommend:

Cautionary interpretation of the patient's hemodynamic status in each of the three

critical periods – cardio-pulmonary arrest period, resuscitation period, and return

to spontaneous circulation period;

Complex approach of the hemodynamic variables as a whole in the deployment of

the resuscitation strategy and post cardio-pulmonary arrest hemodynamic

optimization.

As neuroprotective therapy, given the beneficial effects on the evolution of studied

hemodynamic variables, we suggest using both therapeutic hypothermia as well as memantine.

However, we do consider supplemental clinical investigations necessary, in order to complete

the study of hemodynamic effects of the two neuroprotective strategies.