Physiology of the Newborn Flashcards
What is the estimated blood volume of a newborn?
80-85 ml/kg
Medscape: Samir Gupta, 12/18/2020
The approximate degree of intravascular volume depletion in clinical shock?
Compensated shock: 25%
Uncompensated shock: 25-40%
Irreversible shock: >40%
(Medscape: Samir Gupta, 12/18/2020)
What are appropriate general supportive measures for a newborn in shock?
Secure the airway.
Supplemental oxygen and positive-pressure ventilation
Intravascular or intraosseous access.
10mL/kg colloid or crystalloid (if secondary to hemorrhage– blood should be instituted.)
Careful monitoring of coagulation profiles and management with FFP, platelets, cryoprecipitate (suspect DIC).
(Medscape: Samir Gupta, 12/18/2020)
What is shock?
Acute state of oxygen deficiency at the cellular level.
Shock is a state in which the cardiac output is insufficient to deliver adequate oxygen to meet metabolic demands of the tissues. Cardiovascular function is determined by preload, cardiac contractility, heart rate, and afterload. Shock may be classified broadly as hypovolemic, cardiogenic, or distributive (systemic inflammatory response syndrome [SIRS]—septic or neurogenic).
| Holcomb & Ashcraft
Pediatric Surgery Secrets
What physical signs are associated with shock?
Tachycardia Peripheral vasoconstriction (leading to delayed capillary refill, diminished pulses, decreased skin temperature Hypotension Tachypnea Decreased urine output
(Pediatric Surgery Secrets)
What is MODS?
Multiple Organ Dysfunction Syndrome. It may be associated with shock of any etiology.
Acute respiratory failure, renal failure, hepatic dysfunction, and endocrine and metabolic abnormalities may result from inadequate tissue oxygenation.
The diagnosis of MODS indicates organ dysfunction to the degree that homeostasis cannot be maintained without intervention. Older textbooks may use the acronym MOSF (multiple organ system failure).
(Pediatric Surgery Secrets)
What is SIRS?
SIRS, an acronym for systemic inflammatory response syndrome, is defined as a major inflammatory response to a variety of severe clinical insults such as sepsis, trauma and burns.
It results in activation of common pathogenic pathways, both the molecular and cellular, with common clinical manifestations. It is diagnosed by the presence of two or more of the following:
- Temperature <36C or >38C
- Heart rate > 90 beats/min (adults; variable increase in children)
- Respiratory rate > 20 breaths/min (adults) or partial pressure of carbon dioxide in arterial blood < 32mmHg
- WBC >12,000, <4,000, >10% bands
(Pediatric Surgery Secrets)
What is ARDS?
Acute Respiratory Distress Syndrome is acute respiratory failure due to injury to the alveolar capillary unit.
It results in increased permeability and pulmonary edema.
ARDS may be associated with a variety of insults but most frequently is associated with shock, sepsis, near-drowning, massive transfusions, or aspiration.
Clinical sequelae include metabolic acidosis, multiple organ dysfunction syndrome, disseminated intravascular coagulation, and death.
(Pediatric Surgery Secrets)
When and how is the metabolic acidosis from shock treated?
Metabolic acidosis in shock results from inadequate tissue perfusion, which causes cellular hypoxia. Hypoxia results in the accumulation of acid products of anaerobic metabolism (lactic acidosis).
It usually resolves as oxygenation of tissues and renal function improve.
However, correction with sodium bicarbonate (in addition to volume resuscitation is indicated when the arterial blood pH is less than 7.2.
To avoid over-correction, aggressive correction of the acidosis should stop when the pH is greater than 7.3.
The reason for quickly correcting the acidosis is to alleviate the myocardial depression and increased systemic and pulmonary vascular resistance that undermine resuscitative efforts in patients with shock.
(Pediatric Surgery Secrets)
What are four determinants of oxygen delivery (DO2)?
Heart rate (HR)
Stroke volume (SV)
Hemoglobin (Hgb)
Arterial oxygen saturation (SaO2)
Indicated by the following equations:
1) DO2 (O2 delivery) = CO (cardiac output) x CaO2 (arterial O2 content)
2) CO = HR x SV
3) CaO2 = (SaO2 x Hgb x 1.34) (Hgb x 1.39 x SaO2) + (0.003 x PaO2), where PaO2 = partial pressure of oxygen
(Pediatric Surgery Secrets)
What is SvO2? How is it helpful in monitoring the patient in shock?
SvO2 refers to mixed venous oxygen saturation in a sample taken from the right atrium. It is determined by the following equation:
SvO2 = 1 - VO2/DO2
where VO2 = volume of oxygen utilization. The determinants of SvO2 are oxygen consumption, hemoglobin, cardiac output, and oxygen saturation.
Other than oxygen consumption, these factors can be manipulated during resuscitation to maximize oxygen delivery to the tissues.
Monitoring of SvO2 allows minute to minute assessment of interventions in cardiorespiratory support and resuscitation.
SvO2 is affected by increasing Hgb with transfusions; support of cardiac output with volume, vasopressors, or cardiotropic drugs; and increased oxygen delivery.
(Pediatric Surgery Secrets)
What type of shock is encountered most frequently in children?
Hypovolemic shock.
It is defined as a clinical state characterized by decreased venous return to the heart and subsequent diminished left ventricle filling (decreased stroke volume), resulting in insufficient oxygen delivery to the tissues.
(Pediatric Surgery Secrets)
Initial order for resuscitation of patients with hypovolemic shock?
20mL/kg bolus
Pediatric Surgery Secrets
What percent of body weight must be lost as a result of dehydration before an average healthy child becomes hypotensive?
Decreased blood pressure usually is not seen until about 15% body weight is lost.
(Pediatric Surgery Secrets)
Calculate the fluid deficit for a child who is hypovolemic and now weighs 18kg, given that the previous weight was 20kg.
The patient has lost 2kg, and is therefore 10% dehydrated (2kg of 20kg).
One liter is 1kg. Therefore, a 2kg weight loss translates to a 2000mL deficit.
(Pediatric Surgery Secrets)
How should the fluids be administered to resuscitate the previous patient (2000mL deficit), assuming no ongoing losses?
The patient should be resuscitated over 24h. The usual rule of thumb for replacement of losses is one half of the deficit over the first 8 hours, and the other half over the next 16 hours.
The patient’s calculated deficit is 2000mL. In addition, the patient has a maintenance requirement of 60mL/h.
Every patient receives an initial bolus of 20mL/kg (=400mL). Therefore, the deficit to be replaced over the next 24 hours is now 1600mL.
The rate in mL/hour for the first 8 hours is 800mL/8 hours = 100mL/hr + maintenance = 160mL/hr.
The rate for the next 16 hours is 800mL/16 hours = 50 mL/h + maintenance = 110mL/hr.
Electrolyte composition after intravenous flush is determined and adjusted according to the results of serum electrolytes and laboratory tests.
(Pediatric Surgery Secrets)
What is the estimated blood volume for a term infant?
EBV for a Term infant: 90mL/kg
Pediatric Surgery Secrets
What is the estimated blood volume for a child?
EBV for a child: 80mL/kg
Pediatric Surgery Secrets
What are the clinical symptoms and signs of cardiogenic shock?
Symptoms: Tachycardia Diaphoresis Oliguria Acidosis Hypotension
Signs: Hepatomegaly Jugular venous distension Rales Peripheral edema Decreased cardiac output Elevated CVP, PAWP, SVR
(Pediatric Surgery Secrets)
What are the clinical signs of cardiac tamponade?
Low cardiac output Pulsus paradoxus Jugular venous distension Narrowed pulse pressure Muffled heart tones
(Pediatric Surgery Secrets)
What diagnostic testing should be done in a patient suspected of having cardiogenic shock?
Chest radiograph Electrocardiogram Echocardiogram CVP determination Urine output
(Pediatric Surgery Secrets)
What pathogens most often cause septic shock in neonates?
Neonates: Group B Beta-hemolytic streptococci Enterobacteriaceae Listeria monocytogenes Staphylococcus aureus Herpes simplex
(Pediatric Surgery Secrets)
What pathogens most often cause septic shock in infants?
Infants:
Haemophilus influenzae
Streptococcus pneumoniae
S. aureus
(Pediatric Surgery Secrets)
What pathogens most often cause septic shock in children?
S. pneumoniae Neisseria meningitidis S. aureus Enterobacteriaceae H. influenzae