Neonatal shock

Introduction to neonatal shock Neonatal shock is an acute microcirculatory insufficiency syndrome caused by a variety of causes. Neonatal shock is somewhat more specific than older children. It is characterized by a more complicated cause, rapid progression of the disease, inconspicuous symptoms, and difficulty in diagnosis. When blood pressure drops, the symptoms are obvious, the condition is often irreversible, and the mortality rate is high. Therefore, understanding the characteristics of neonatal shock, early diagnosis is extremely important. basic knowledge Sickness ratio: 0.0001% Susceptible people: children Mode of infection: non-infectious Complications: metabolic acidosis

Neonatal shock cause

(1) Causes of the disease

The primary disease that causes neonatal shock can be divided into three categories, namely, cardiogenic, infectious, and hypovolemic shock.

Cardiogenic shock (39%):

(1) Hypoxic myocardial damage: asphyxia, pneumonia, respiratory distress, apnea. (2) Metabolic myocardial damage: hypoglycemia, hypocalcemia, etc. (3) severe arrhythmia: paroxysmal supraventricular or ventricular tachycardia, severe heart block. (4) Congenital heart disease. (5) Neonatal persistent pulmonary hypertension. (6) hypothermia and scleredema.

Hypovolemic shock (27%):

Dehydration caused by various causes, diarrhea and vomiting, although low blood volume shock accounted for a small number of hospitalization, but the incidence of shock is high, should be paid attention to. (1) Loss of blood at birth: placenta previa, placental rupture, placental abruption, umbilical cord tear, fetal-placenta, fetus-mother, fetus-fetal transfusion. (2) neonatal bleeding: intracranial hemorrhage, pulmonary hemorrhage, gastrointestinal bleeding, adrenal hemorrhage, abdominal visceral rupture. (3) Dehydration: vomiting, diarrhea, necrotizing enterocolitis, non-dominant water loss during phototherapy, and fever syndrome.

Septic shock, others (16%):

Sepsis, severe pneumonia, intrauterine or postnatal viral infection. Neurogenic shock such as childbirth injury, drug-induced shock, such as improper application of vasodilators.

(two) pathogenesis

Neonatal shock is caused by a variety of causes of acute microcirculatory dysfunction leading to insufficient vital organ perfusion and multiple organ dysfunction, causing microcirculatory insufficiency in the cause of hypovolemic shock, cardiogenic shock, asphyxia shock The mechanism of occurrence is relatively clear. As mentioned above, the mechanism of septic shock is more complicated, and there are many studies. The brief is as follows:

1. Microcirculatory disorders: After serious infection, bacteria or other pathogenic microorganisms and their produced toxins act on the body to cause microcirculation disturbances, which are generally divided into compensation period and decompensation period.

(1) Compensation period: This period is the compensation stage of shock, also known as the microcirculation cycle. Under the action of bacteria and its toxins, the body's sympathetic nervous system is excited, vasoconstriction, due to the sympathetic nerves in the blood vessels of the brain. The distribution is less, the blood vessels do not shrink, and the blood vessels of the skin and abdominal viscera are contracted, so that the blood circulation is reduced, so as to ensure the blood supply of important organs such as the heart and brain, and the renal blood flow is reduced, and the renal blood flow is reduced. The paracellular cells release renin into the blood, convert the angiotensinogen in plasma into angiotensin I, and then convert to angiotensin II by conversion enzyme. Angiotensin II has a strong contractile vasoactive effect, and its concentration during shock The increase is an important compensatory mechanism for maintaining blood pressure and blood supply to important organs during shock, and it plays a temporary role in maintaining life.

(2) Decompensation period: also known as microcirculation congestion stage, is the decompensation stage of shock, due to long-term microvascular contraction, tissue hypoxia, increased anaerobic metabolism, excessive lactic acid production, in this acidic environment, pre-capillary The vaso-sphincter relaxes, the capillaries are open, and the venous end is more resistant to the acidic environment and is still in a contracted state, causing a large amount of blood to stagnate in the microcirculation. As the blood flow stagnates, the intravascular pressure increases and the vascular permeability increases. , plasma exudation, decreased blood volume, reduced blood volume, reduced effective circulation, due to plasma extravasation, blood concentration, increased viscosity, red blood cell aggregation and endothelial cell damage, release of procoagulant substances, initiation of internal and external coagulation system Disseminated intravascular coagulation (DIC).

2. Oxygen free radical damage: In recent years, oxygen free radicals have deepened their understanding of cell damage and disease, and they believe that oxygen free radicals are involved in the occurrence and development of shock. Under normal circumstances, oxygen free radicals are produced and cleared in the body. Dynamic balance, this balance is maintained by superoxide dismutase (SOD), catalase (CAT), etc., the role of free radical scavengers SOD and CAT is reduced during shock, free radicals are excessively increased, and oxygen radicals have strong chemical activity and performance. Unstable, easy to lose electrons (oxidation) or capture electrons (reduction), especially its oxidation is very strong, can attack and destroy nucleic acids, proteins, sugars and lipids, oxygen free radicals and membrane lipid phospholipids The reaction produces lipid peroxide, which destroys the cell membrane and the organelle membrane, which is easy to cause a series of tissue damage, such as damage to the mitochondrial membrane-induced energy production; damage to the lysosomal membrane to release lysosomal damaged tissue; damage to platelet membrane production Lipid peroxide; causing platelet aggregation to cause DIC; increasing capillary permeability increases shock.

3. Changes in -endorphin (-EP) in blood during shock -endorphin is an important endogenous opioid. Since 1978, Holoday and Faden applied the opioid receptor antagonist naloxone (naloxone). In the treatment of endotoxin shock in animals, it has been proved that endogenous opioids may be involved in the pathological process of shock. In recent years, the role of -EP in shock development has progressed rapidly. -EP exists in the pituitary and between the brains. Leaves, spinal sympathetic ganglia and adrenal medulla, which inhibit the cardiovascular effects of prostaglandins and catecholamines, inhibit cardiovascular center and peripheral blood vessels and heart, reduce cardiac output, vasodilation, increased permeability, blood pressure, etc. When the shock occurs, the body undergoes a stress reaction, and -EP is released in a large amount, causing the above series of changes, which makes the shock worse.

4. Multiple organ system dysfunction: If the duration of shock is too long, it may cause damage to multiple organ systems, such as renal cortical and medulla damage or necrosis due to insufficient renal blood perfusion; cerebral hemorrhage caused by cerebral microcirculation disorders Oxygen brain damage; alveolar epithelial cell ischemia and pulmonary edema, leading to pulmonary insufficiency and shock lung, ischemia during hypoxia, hypoxia can also cause myocardial damage to cardiac insufficiency, damage to liver-induced liver dysfunction.

Neonatal shock prevention

Mainly to prevent various causes of shock, active diagnosis and treatment of primary diseases, such as control of infection, sepsis, dehydration, allergic reactions, myocardial damage, arrhythmia, tension pneumothorax, severe anemia, etc., if timely control of the above conditions, And promote recovery, it can effectively prevent the occurrence of shock.

Neonatal shock complications Complications metabolic acidosis

Severe metabolic acidosis, multiple organ failure and DIC.

Neonatal shock symptoms common symptoms cyanosis, lethargy, blood pressure, pale skin, conscious disorder, coma, muscle tension, tachycardia, shortness of breath, lung snoring

The clinical manifestations of shock vary in different stages of shock. In addition to the aforementioned hypotension and decreased urine output, tachycardia can occur, capillary filling time is prolonged, skin spots are fine, limbs are cold, but the central temperature is normal. Small pressure difference, apnea, shortness of breath, metabolic acidosis, weak pulse and other performance.

Neonatal shock can be divided into compensation period (early stage), decompensation period (interim period) and irreversible period (late stage). Due to poor compensatory ability of newborns, early performance is often atypical, rapid development, and soon entered by early stage. Medium, late.

1. Early: This period is the compensatory stage of shock, also known as the microcirculation cycle. Under the action of bacteria and its toxins, the body's sympathetic nervous system is excited, vasoconstriction, blood vessels in the skin and abdominal viscera are contracted, making blood circulation The amount is reduced to ensure the blood supply of important organs such as the heart and brain, and it plays a temporary role in maintaining life. This period is mainly caused by vasoconstriction such as pale skin, cold extremities, upper limbs up to the elbow, and lower limbs up to the knee. Increased heart rate, >160/min when quiet, cerebral hypoxia such as low response (sleepiness, dullness), decreased limb muscle tone, examination of the forearm skin capillary refill time, >2s is abnormal, combined with skin color and limb The coldness at the end indicates that the microcirculatory disorder is important for early diagnosis of shock.

2. Interim : It is the decompensation stage of shock, also known as microcirculation and congestion. Due to long-term microvascular contraction, tissue hypoxia, anaerobic metabolism increases, and lactic acid production is excessive. In this acidic environment, the anterior capillary sphincter relaxes. The capillaries are open, and the venous end is more resistant to the acidic environment, and is still in a contracted state, causing a large amount of blood to stagnate in the microcirculation. Due to stagnant blood flow, increased intravascular pressure, increased vascular permeability, and plasma infiltration Out, the blood volume is reduced, the blood volume is reduced, the effective circulation blood volume is reduced, the skin color changes from pale to bun and even patterns appear. The limbs are colder than the knees and elbows, the consciousness disorder is further aggravated, the performance is drowsy or coma, and the heart rate is reduced. Slow to <120/min, heart sounds are low and blunt, blood pressure may drop, full-term infants fall below 6.67 kPa (50 mmHg), premature infants fall below 5.33 kPa (40 mmHg), pulse pressure difference is reduced (<4.0 kPa), inner forearm Skin refill time> 3s, first increase in breathing, slow down, irregular rhythm, respiratory failure [lung snoring, chest inhalation and/or apnea], often accompanied by decreased urine output ,even 8h <2ml / kg, or edema occurs hypothermia, hard skin swelling.

3. Late stage : mainly manifested as multiple organ dysfunction and DIC, pulmonary hemorrhage is the most common, and more died of pulmonary hemorrhage and respiratory failure, which can be manifested as intracranial hemorrhage, acute renal failure, electrolyte imbalance, severe metabolic acidosis.

Neonatal shock examination

1. Blood gas analysis: First, metabolic acidosis occurs, which is positively correlated with shock. Due to poor peripheral perfusion, the actual arterial oxygen pressure in children with shock is higher than that of arterialized peripheral blood and percutaneous measurement. Oxygen partial pressure, the heavier the shock, the greater the gap. If the child with shock has no lung disease, the partial pressure of carbon dioxide does not increase. If the partial pressure of carbon dioxide is increased, and the partial pressure of oxygen is lowered, the lung of the shock should be considered. Possibly, the value is 0.3920.696kPa (47.1cmH2O), the central venous pressure of cardiogenic and septic shock is increased, hypovolemic shock, central venous pressure is reduced, indicating metabolic acidosis, pH<7.0 is severe shock , pH < 6.8 shows poor prognosis.

2. DIC examination: DIC screening should be done when the platelet count is lower than 100×109/L, and moderate shock should be done for DIC.

3. Serum electrolyte examination: tissue hypoxia during shock, impaired cell membrane sodium pump function, increased permeability, causing Na to enter the cell, causing hyponatremia, and easy to cause hypokalemia after supplementation with alkaline drugs, so Serum electrolytes should be checked promptly.

4. Other laboratory tests: liver and kidney function tests should be performed; those with convulsions should measure blood sugar, blood calcium, and blood magnesium.

5. Chest X-ray examination: observe the size of the heart, pulmonary edema, primary lung lesions, pulmonary hemorrhage in the late stage.

6. Electrocardiogram, echocardiography: for arrhythmia, cardiac function judgment.

7. Central venous pressure (CVP examination) can distinguish the type of shock, cardiopulmonary shock CVP increased, hypovolemic shock CVP decreased, septic shock CVP normal or slightly higher.

Diagnosis of neonatal shock

diagnosis

The diagnosis of neonatal shock mainly includes the following aspects:

1. Correct blood pressure measurement: If the cuff is used for blood pressure measurement, the width of the cuff should be noted. The width of the cuff should be 2/3 of the length of the upper arm. If the width is too wide, the measured blood pressure value is lower than the actual one. The measured blood pressure value is higher than the actual value. If the arterial indwelling tube is used for pressure measurement, it should be ensured that the transducer has been correctly zeroed, the waveform is not damped, and the transducer should be at the right atrium level.

Once suspected of shock, blood pressure should be monitored in time, such as systolic blood pressure <50mmHg in full-term children, systolic blood pressure <40mmHg in premature infants is hypotension, and pulse pressure difference is reduced. It should be noted that sympathetic nerve excitability is strong in neonatal shock and can be maintained longer. The vasoconstriction of time, so the blood pressure in the early stage of shock can be normal, the blood pressure drop has been in the middle and late performance, so the blood pressure drop can not be used as an early diagnostic indicator of neonatal shock.

2. Urine volume: After 24 hours, the normal urine volume is about 2ml/(kg·h). In the first few hours after birth, the individual urine volume is not a reliable indicator for determining shock, but it is generally considered that the urine volume is less than 0.5~1ml. / (kg · d) should consider renal hypoperfusion, decreased renal perfusion during shock, and decreased urine output.

3. Clinical manifestations: The clinical manifestations of shock vary in different stages of shock. In addition to the aforementioned hypotension and decreased urine output, tachycardia may occur, capillary filling time is prolonged, skin spots, limbs are cool but the center Normal temperature, small pulse pressure difference, apnea, shortness of breath, performance of metabolic acidosis, weak pulse, etc.

4. Laboratory inspection

(1) blood routine examination: including white blood cell differential count, platelet count, hematocrit and hemoglobin content, if the series of tests can be more meaningful.

(2) Glucose screening test: blood urea nitrogen, creatinine and blood magnesium, blood calcium level check, if abnormal, appropriate treatment should be appropriate.

(3) Blood should be drawn before the application of antibiotics.

(4) Arterial blood gas analysis, capillary blood gas analysis is not reliable in neonatal shock.

(5) If DIC is suspected, a coagulation test should be performed.

(6) Other special tests to determine or rule out the cause of shock.

(7) Regular chest radiographs.

(8) If intracranial hemorrhage is suspected, head ultrasound or CT examination should be performed.

(9) Echocardiography to evaluate the structure and function of the heart.

(10) An electrocardiogram should be performed for suspected arrhythmia.

(11) When necessary, the central venous pressure measurement is performed to help the diagnosis and treatment of shock.

5. Scoring method for neonatal shock: Because the clinical manifestations of neonatal shock are not typical, the severity of shock can not be judged by one or two clinical manifestations. A scoring method of shock staging and indexing should be established to become the diagnostic criteria for neonatal shock. .

The Gabal Shock Score is an earlier shock diagnosis score method adopted by many clinicians. On this basis, the Ministry of Health proposed five diagnostic scores for neonatal shock in 1985. Wu Yubin et al. modified these methods and shocked them. After the stepwise regression analysis of various clinical indicators, a new method for the diagnosis of newborn shock diagnosis was proposed.

The neonatal shock score is meaningful for diagnosis. In the three consecutive shock diagnosis scoring methods, the main diagnostic indicators of shock are 5, namely blood pressure, pulse, limb temperature, skin color and capillary filling time, Wu Yubin, etc. Analysis, in neonatal shock, the abnormal rates of these five indicators are: capillaries filling time is the highest rate of 100%; skin color is 96%; limb temperature is 84%; pulse is 78%; and abnormal blood pressure The lowest rate is 45%.

Differential diagnosis

1. Characteristics of various types of shock

(1) hypovolemic shock: visible pale skin, central venous pressure decreased, blood loss caused by anemia, hematocrit decreased, such as acute blood loss is 10% to 15% of systemic blood loss, blood pressure decreased slightly, blood loss When the amount reaches 20% to 25%, the symptoms of shock are obvious.

(2) septic shock: there is a clear serious infection of the primary disease, the symptoms of infection poisoning are obvious, or high fever, or body temperature does not rise, acidosis is obvious, blood lactic acid is significantly increased, and central venous pressure is elevated.

(3) cardiogenic shock: there is a primary heart disease, often with cardiac dysfunction such as enlarged heart, liver, difficulty breathing, fast heart rate, gallop, etc., ECG, echocardiography, X-ray and other cardiac examinations often There are abnormal findings.

(4) Asphyxia shock: There is a history of severe asphyxia, rapid heart rate, shortness of breath, enlarged heart, ECG with ST-T changes of myocardial ischemia, and elevated central venous pressure.

2. Performance of multiple organ system failure

(1) Pulmonary insufficiency: Also known as shock lung or adult respiratory distress syndrome (ARDS), showing dyspnea, cyanosis, severe hypoxemia and hypercapnia.

(2) Brain failure: convulsions, coma, central respiratory failure.

(3) Heart failure: rapid heart rate, fast breathing, enlarged heart, liver and other manifestations of heart failure.

(4) Renal failure: oliguria, no urine, serum creatinine, elevated urea nitrogen, elevated blood potassium.

(5) Liver failure: jaundice, liver, abnormal liver function, gastrointestinal bleeding.

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