Therapeutic hypothermia: basic definitions, methodology, application experience.

Causes of death of full-term children
  • Meconial aspiration
  • Birth trauma
  • Severe intranatal asphyxia

Terminology
Severe asphyxia at birth is a condition characterized by a low assessment on the Apgar scale and a complex of clinical and laboratory signs of a violation of the child's condition

Apgar score
  • In the first minute 1-3 points
  • At 5 minutes less than 5 points
  • At 10 minutes less than 5 points
Terminology
  • Hypoxic-ischemic encephalopathy is characterized by a complex of neurological disorders of varying severity resulting from asphyxia at birth
  • Stages/degrees of GIE in full-term infants according to Sarnat (N.,Sarnat M., 1976 in modification Stoll B., Kliegman R., 2004)
Indicator Stage I Stage II Stage III
The level of consciousness Anxiety Lethargy Sopor, coma
Muscle tone Standard Hypotension Lethargy
Pose Mild distal inflection Significant distal inflection Decerebration
Periotsal reflexes Increased Increased Reduced or depressed
Myoclonuses There are There are Missing
The Moreau Reflex Strong Weak No
Pupil Mydriasis Myosis Reduced photoreaction
EEG Standard Low-voltage changes, convulsive activity Periodic pattern with isopatential phases
Duration Less than 24 hours 24 hours-14 days Hours-weeks
Forecast Good Variable Death, severe violations

Epidemiology

Intranatal hypoxia is diagnosed in 1-4/1000 full-term newborns (WHO data)

Pathogenesis
    The phase of primary damage to the nervous tissue develops at the time of exposure to asphyxia and is characterized by irreversible death of brain cells, the volume of which depends on the depth and duration of hypoxia.
  • The secondary damage phase is activated in the reoxygenation – reperfusion phase 2-12 hours after the primary damage.

Hypothermia is the only method that has an inhibitory effect on all destructive processes that are the consequences of asphyxia.

       


Criteria for therapeutic hypothermia

 (protocol in the Russian Federation)
  • General criteria: gestational age more than 35 weeks; birth weight more than 1800 grams.
  • Further, the selection criteria are divided into three groups: A, B and C. The presence of at least one criterion in each of the three groups is an indication for therapeutic hypothermia.

Criteria of group A
  • Apgar score ≤ 5 at 10 minutes
  • The continuing need for a ventilator at 10 minutes of life
  • In the first blood test (umbilical cord, capillary or venous) taken during the first 60 minutes of life, pH 7.0 or in the first blood test (umbilical cord, capillary or venous) taken during 60 minutes of life, the base deficiency (VE) ≥16 mol/L.

Criteria of group B
  • Clinically pronounced seizures (tonic, clonic, mixed) Muscular hypotension and hyporeflexia
  • Pronounced hypertonia and hyporeflexia
  • Violations of the pupillary reflex (narrowed and does not respond to dimming, dilated and does not respond to light, weak pupil response to changes in lighting).

Criteria of Group C
  • The criteria of group "C" are based on the results of amplitude-integrated electroencephalography (AEG);
  • A pattern with a normal amplitude (the upper edge of the trend is the maximum amplitude, more than 10 mv, the lower edge of the trend is the minimum amplitude, more than 5 mv), combined with repeated convulsions

  • An intermittent pattern with a maximum amplitude of more than 10 mv, a minimum amplitude of less than 5 mv. There is no cyclic variability

  • A constant low-amplitude pattern with a maximum amplitude of less than 10 MV, a minimum amplitude of less than 5 mv. There is no cyclic variability

  • Convulsive status (continuous convulsive activity for 20 minutes or more) against the background of any of the listed patterns


Contraindications
  • Birth weight less than 1800 grams, gestational age less than 35 weeks.
  • The age of the child at the time of the decision on hypothermia is more than six hours.
  • Severe congenital malformations requiring emergency/urgent surgical intervention.
  • Severe birth defects incompatible with life.
  • Detection of intracranial hemorrhage during examination.
  • Refusal to carry out the procedure of the child's legal representatives.

Phases

  • Induction - to reach the target temperature (33.5 C in 1-3 hours). If cooling is started in the first 1.5 hours, the number of dead cells decreases by 70%; if after 5.5 hours, by 50%; if after 6-8 hours, it is not significant.
  • The temperature maintenance phase is 72 hours, the target temperature is 33.5 C. The level of metabolism in the central nervous system decreases by 6-10% when the temperature drops by 1C. At a temperature of 33.5 C, metabolism is reduced by 25-40%.
  • The warming phase is no more than 0.3–0.5 C per hour to a temperature of 37C for 7-9 hours.

Indicators during hypothermia
  • Average blood pressure is 45-65 mmHg;
  • Saturation of hemoglobin with oxygen SpO2 - 90-95%;
  • PCO2 = 35-55 mmHg;
  • PO2 = 60-80 mm Hg;
  • Electrolytes within normal limits;
  • Glucose within normal limits;
  • Heart rate = 80-120 per minute, with a decrease in heart rate of less than 80 per minute, it is necessary to exclude excessive administration of sedatives and painkillers
  • Concomitant intensive therapy in the process of therapeutic hypothermia should be carried out according to generally accepted rules and indications

Complications
  • sinus bradycardia;
  • prolongation of the QT interval;
  • thrombocytopenia; hypocoagulation;


  • violations of the level of glycemia;
  • subcutaneous fat necrosis;
  • arterial hypotension;

  • increased oxygen consumption;
  • reduction of surfactant production;
  • increased resistance of pulmonary vessels;
  • increased risk of jaundice;
  • reduced resistance to infections


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