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Cardiovascular Physiology And Support 21
Cardiogenic Shock have similar management plans. The foundation of oxygen delivery to
Cardiogenic shock is defined as shock due to cardiac failure, which compensate for oxygen utilisation allows medical care providers a target
can be due to infections, trauma, drug overdose, cardiomyopathies, and to aim toward as they seek to resolve the hypovolaemia, identify the
congenital heart disease. Although cardiac failure may be present in organism in sepsis, search for the cardiac resolution of the shock, or treat
other forms of shock, this form is directly due to the cardiac function. In the acute spinal cord injury and associated implications of the physi-
the newborn period, cardiogenic shock can be caused by a hypoplastic ological implications of no sympathetic nervous system. Table 4.3 lists
left heart, which is difficult to manage in any environment. some common cardiovascular medications used in shock management.
The management of cardiogenic shock depends on the aetiology Clinical Correlations
of the hypotension, but the use of vasopressors such as dopamine
and epinephrine with the addition of 5–10 ml/kg boluses of fluids The following scenarios illustrate the clinical impact of alterations in
while monitoring cardiac volume indirectly may help temporarily. cardiovascular function and provide recommendations for management.
Arrhythmias may occur more commonly in this form of shock, and the Case Scenario #1
identification of the type of electrocardiogram (ECG) abnormality will Presentation
help as treatment options are considered. You are planning a posterior sagittal anorectoplasty (PSARP) on an
Cardiogenic shock carries a high mortality rate, and invasive 8-month-old male with high imperforate anus and unrepaired tetralogy
monitoring with mechanical circulatory assistance is sometimes of Fallot (TOF). The patient had a colostomy at one month of age and
difficult to obtain in resource-poor settings. Without surgical correction since that time has had approximately two episodes of central cyanosis,
of the correctable cardiac paediatric lesions, at times only palliative which resolve spontaneously per day. The patient is not on any medica-
care can be provided for these patients.
tions except for iron supplement, and the room air oxygen saturation is
Neurogenic Shock 90%. His preoperative haemoglobin level is 8.1. He is small for his age,
Cervical spinal cord injury is associated with dysfunction of the sym- at 5.1 kg, and has no known respiratory issues.
pathetic nervous system, resulting in such cardiovascular changes 1. What is the likely aetiology of his cyanotic episodes?
as severe bradycardia, asystole, and loss of peripheral vascular tone. 2. How should this patient be managed intraoperatively?
Cardiovascular problems known to arise from SNS dysfunction
include low resting blood pressure, orthostatic hypotension, autonomic Treatment
dysreflexia, reflex bradycardia, cardiac arrest, limited cardiovascular This patient has documented tetralogy of Fallot, a cardiac anomaly
response to exercise, and alterations in skin microcirculation. characterised by right ventricular outflow obstruction associated with a
Patients in neurogenic shock initially have warm extremities and ventricular septal defect (VSD), overriding aorta, and right ventricular
low diastolic pressure, which may eventually develop into a situation hypertrophy. Due to the obstruction of right ventricular outflow, blood
of acidosis and a decrease in perfusion pressure. With the sudden loss flow through the pulmonary circulation in most patients occurs through
of sympathetic tone, especially if the lesion is above T6, the patient persistence of the foetal connection between pulmonary and systemic
may demonstrate signs of bradycardia and other arrhythmias due to the circulations, the ductus arteriosus. Therefore, in these patients, oxygen-
effect of the cardioaccelerator fibers. Pulmonary oedema may develop ated blood returning from the lungs and unoxygenated blood returning
due to fluid resuscitation when the loss of sympathetic tone results from the peripheral tissues are mixed in the ventricles through the VSD.
in peripheral vasodilatation. The management of neurogenic shock The percentage of cardiac output passing through the pulmonary circu-
depends upon the level of injury and the involvement of the levels lation determines the severity of cyanosis.
for ventilation. If the level is below C8, then the diaphragm is intact Patients with TOF frequently experience episodes of worsening
and providing the necessary muscles of inspiration needed to maintain cyanosis (“tet” spells) associated with decreased pulmonary perfusion
oxygenation. Fluid resuscitation and monitoring for bradycardia may in response to stimuli that increase pulmonary outflow obstruction or
prompt the use of intravenous atropine and even vasopressors to decrease systemic vascular resistance. Options for treating cyanotic
maintain the appropriate blood pressure. episodes include IV fluid boluses, pressure on the abdominal aorta,
Management of Shock liver compression, morphine 0.1 mg/kg IV, or intravenous sodium
All forms of shock—hypovolaemic, septic, cardiogenic, and neuro- bicarbonate. Oxygen is seldom helpful during a ”tet” spell due to
genic—can have similar effects on the paediatric patient, and therefore decreased pulmonary perfusion. During an anaesthetic, it is important
to avoid a drop in systemic blood pressure, as this will worsen right-
Table 4.3: Common cardiovascular medications.
Drug Paediatric dosing Uses Classification Mechanism of action

Alpha- and beta1- agonist;
Dopamine 5–20 mcg/kg per min IV Shock Inotropes/ vasopressors stimulates dopaminergic
receptors
0.01 mg/kg IV q 3–5 min prn for arrhythmia; Asystole, VF, pulseless Sympathomimetic stimulation
Epinephrine Inotropes/ vasopressors;
(Adrenalin) SC/IM q 20 min–4 hr for anaphylaxis or VT, bradycardia, asthma, anti-arrhythmics; anaphylaxis of alpha- and beta- adrenergic
asthma anaphylaxis receptors
5–20 mcg/kg IV bolus, then 0.1–0.5 mcg/
kg/min IV; or 0.1 mg/kg SC/IM q 1–2 hr for
Phenylephrine mild hypotension; or 5–10 mcg/kg IV x 1 for Shock, hypotension, PSVT Inotropes/ Vasopressors Smooth muscle alpha-agonist
(Neo-Synephrine) conversion (vasoconstrictor)
paroxysmal supraventricular tachycardia
(PSVT) conversion

10- 50 mg IV (adults) prn hypotension Inotropes/ Vasopressors; Smooth muscle alpha-agonist
Ephedrine Hypotension
titrated to effect Decongestants (vasoconstrictor)