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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)
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