Cardiology Flashcards
Determinant of cardiac output
heart rate (HR) and stroke volume (SV). It is expressed as follows:
CO = HR × SV
What is stroke volume and its determinants
Stroke volume is the difference between end-diastolic volume (EDV) and end-systolic volume (ESV)
Affected by preload, contractility and afterload.
What is the definition of physiologic hypotension
Cerebrovascular autoregulation is lost leading to cerebral function compromise and tissue ischemia
What is expected MBP after 72 hours regardless of gestional age
MBP > 30 mmHg
Factors in the fetus that ensures most oxygentated blood goes to the heart and brain (4)
- Low SVR
- High PVR
- PDA
- PFO
What are the transition from fetal to neonate circulation (4)
- Cord clamping: removal of placenta result in inc in SVR
- First breath: reduce PVR, inc pulm blood flow
- Inc LA pressure: functional closure of PFO
- Inc PaO2: PDA closes
Factors contributing to hypotension in preterm neonates (7)
- Immature myocardium: dec contractility
- Maladaptive transition: may not overcome the inc SVR (common in neonates <30 wks)
- PDA: steal syndrome
- Perinatal hypoxia/ asyphyxia: inc catecholamine, RAA axis, vasopressin, myocardial dysfunction
- PPV: inc intrathoracic pressure
- Sepsis and inflamatory response: TNF and IL-1: vasodilation and permeability
- Relative adrenal insufficiency
Adverse effect of hypotension
- Impaired cerbral blood flow (immature autoregulation)
- Ischemia: low BP
- Hemorrhage: high BP
Avoid fluctations in BP to prevent IVH
Permissive hypotension: MAP less than gestational age but good perfusion (CRT, HR, UO, no acidosis)
Indication to treat hypotension
- prolonged
- associated with:
- metabolic acidosis
- hypoxia
- hypocapnia/ hypercapnia
Treatment for hypotension (8)
- Volume expander: PRBC for anemia, crystalloid
- Dopamine
- Dobutamine
- Epinephrine
- Vasopressin
- Milirone
- Hydrocortisone
- Dexamethasone
What is the MOA of dopamine
Release of stored norepinephirne from terminal nerve ending (stores last for 8-12 hrs)
- for hypotension cause by vasodilation- inc afterload
What are the dose and effect of dopamine
- Low dose (2-4): dopaminergic receptor- dilate renal and splanchnic vessels
- moderate (5-10): beta1&2, alpha 1 and dopa- inc cardiac contractility and HR
- high (>10-20) alpha 2 receptor- inc SVR
MOA of dobutamine
cardioselective inotrope (limited chronotrope)
- limited effect on BP and afterload
- preferred for myocardial dysfunction
- not dependent on endogenous catecholamine
What are dose and effect of epinephrine drip
- Low dose (0.01-0.1 ug/kg/min)- (beta) myocardial contractility and peripheral vasodialtion
- Higher dose: >0.1 ug/kg/min)- (alpha) increase heart rate, peripheral vasoconstriction and inc PVR
Side effect of epinephrine
- risk for hyperglycemia and inc lactate
Indication for vasopressin in hypotension
- vasodilatory shock resistant to catecholamine
- to be used as infusion
Dopa vs vasopressin: lower pCO2, received fewer doses surf, no tachycardia
MOA of milrinone
- inc cAMP (via phosphodiesterase III inhibitor)
- enhances myocardial contractility without inc mycardial O2 or inc afterload
- dec vas tone both systemic and pulm
Adverse effect of milrinone
thrombocytopenia and hypotension
Cardiovascular action of hydrocortisone (5)
- Upregulation of cardiovascular adrenergic receptor
- upregulation angiotensin II
- Inhibition of NO synthase and vasodilatory PG
- Inhibition of catecholamine metab
- Inc intracellular Ca
Concentration reduced hemoglobin for cyanosis to be visible
3-5 g/dl
Ex:
Hgb 15, de-ox 10/15= 70-80% O2 sat
Hgb 20, de-ox 15/20= 80-85% O2 sat
True or false Hgb F has a lower p50
true- bec Hgb F is more avid to O2
What amino acid is substituted in Hgb F
histidine to serine
True or false central cyanosis in Hgb F is seen at a lower pO2
True- cyanosis a pO2 40 vs pO2 50 with adult Hgb
Factor that Hgb love O2 (shift to the left)
- Low H (alkalosis)
- Low CO2
- Low temp
- Low 2,3BPG- as in fetal Hgb
Cyanosis presenting at rest and improves with crying
Choanal atresia
- inability to pass catheter thru the nares
- Confirm CT
- Improve: oral airway
Cyanosis more pronounced in supine
Micrognathia, retrognathia, pierre robin
- Obtruction from tongue
- reduce at prone
- may require tracheostomy
Cyanosis that worsens with crying, feeding, supine or resp infection
Laryngomalacia/ tracheomalacia
- inspiratory stridor
- presents at several weeks
- temporary elevation of head
- Improves with time
Presents as expiratory stridor, resp distress, wheezing, persistent cough
Tracheal stenosis
- dx: direct bronchoscopy
- assoc with complete tracheal rings
- Tx: surgical repair
Stridor associated with birth or surgical injury
Vocal cord paralysis
- Unilarteral: hoarse cry
- Bilateral respiratory distress and cyanosis
What are the congenital lung abnormalities presenting with resp distress and cyanosis unresponsive to standard vent
- diaphragmatic hernia
- CPAM
- Pulm sequest
- Lobar emphysema
- Arteriovenous fistula
Condition with hypoventilation, apnea, cyanosis
ICH, seizure, encephalopathy
Diagnosis: infant with cyanosis without resp distress, dec O2 sats but N PaO2
Methemoglobinemia
Differential dx after O2 admi based pO2
- <100- cardiac with parallel circ/mixing lesion with restricted PBF
- 100-150- PPHN, mixing lesion with inc PBF
- 150-300- Pulm d/o, CNS, meth
- >300 N
Primary screening target of CCHD (12)
- Truncus
- TGA
- Tricupsid atresia
- TOF
- Total anomalous pulmonary venous return
- Hypoplastic left heart syndrome
- Double outlet right ventricle
- Ebstein anomaly
- Interrupted aortic arch
- Single ventricle complex
- Coarctation of the aorta
- pulm atresia with intact septum
The most common neonatal cardaic tumor
Rhabdomyoma
- associated with tuberous sclerosis