Wednesday, September 12, 2012

Patient Presentation--Transposition of the Great Arteries

Patient Profile:
Age: 13 days
Sex: F
Bed: 06PE-13-01
MRN: 5882682
Height: 46.5 cm (BBL: 47 cm, 25-50th percentile)
Weight: 2.4 gm (BBW: 2374 gm, 10-25th percentile)
BHC: 32.3 cm, 50th percentile
Vaccinations: BCG (-), HBV (-), HBIG (-)

Chief complaint: prenatal congenital heart disease, cyanosis, respiratory distress after birth

Maternal history:
(1) Maternal disease:
arrhythmia without medication treatment, HBsAg(-), HBeAg(-), VDRL(-), GBS(not done), hyperthyroidism(-), hypothyroidism(-), DM(-), SLE(-), APS(-), hypertension(-), Rh-(-), pre-eclampsia(-), PIH(-), GDM(-), APH(-), placenta abruptio(-), infection(-)
(2) Prenatal exam:
congenital heart disease (suspect TGA) noted since GA 20wk, IUGR(-), oligohydramnios(-), polyhydramnios(-), thalassemia(-), chromosome anomaly(-), other inherited disease(-)
(3) Drug exposure:
MgSO4(-), ritodrine(-), steroid(-), antibiotics(-), others(-)
(4) Radiation exposure:

History of present illness:
Female baby was born to her mother, G2P2, GA 26+2 weeks (preterm), and delivered via NSD/CS.  Congenital heart disease, TGA was suspected on prenatal examination since GA 20 weeks.  Baby was delivered without complications and cyanosis and heart murmur were noted after birth (SpO2 80% on room air, 85% under free flow O2).  PGE1 started and tapered down gradually.
CVS specialist consulted.  Total correction performed (arterial switch operation, PDA division, ASD closure, VSD patch repair) and the patient was transferred to ICU for post op care.  Vancomycin and ceftazidime were started for infection prophylaxis.  Dopamine and milrinone started for hemodynamic support.
Sternum closure performed.
Phototherapy started for neonatal jaundice. 
Chylothorax discovered, patient NPO and TPN administered.

Systemic disease and Past medical history:

1.  Chylothorax
1.      Milky fluid in chest tube drainage
2.      Consolidation in right lung noted on several CXR’s
1.      Chylothorax occurs when lymph fluid accumulates in the pleural space due to disruption or obstruction of the thoracic duct.
2.      Traumatic vs nontraumatic; surgical procedures (traumatic) are commonly associated with chylothoraces
3.      Diagnosis: 
·         Chest radiograph
·         Milky fluid from thoracentesis or chest tube drainage
·         Pleural fluid analysis—predominance of lymphocytes, elevated TG (>110 mg/dL)
4.      Postsurgical chylothorax: 
·         Pleural drainage to control symptoms—monitor electrolytes, lymphocyte counts, albumin, total protein, weight
·         Fasting or reduced fat diet—decrease flow of chyle through thoracic duct allows spontaneous closure of a thoracic duct leak
·         Pleurodesis—not responding to thoracentesis, dietary control measures
·         Thoracic duct ligation—high volume chylothorax
5.     Current tx:
·        Chest tube drainage—drainage has become more clear, volume drained is trending down, mediastinal chest tube pulled last night
·        Patient NPO on 9/12
·        May start dextrose and taper down TPN today (9/14)
·         Resolve chylothorax
·         Prevent infection
·         Restart oral intake

·      Drainage volume, clarity
·      Signs and symptoms of infection:  leukocytosis, fever
·      Clinical signs of improvement
·      Electrolytes, CBC, protein, body weight

2.  Cardiovascular management
1.     UOP (4.15 mL/kg/hr on 9/12, 5.29 mL/kg/hr on 9/13)
2.     SCr elevated (0.8 on 9/12); should be <0.6
3.     HR (190’s on 9/7, trending down, 130-150 now)
4.     BP (70-80/50’s on 9/14)
1.     Pediatric patients are at high risk of being in a low cardiac output state post CV surgery.
·      Hypovolemia from operative/postoperative bleeding
·      Inflammatory cascade
·      Stunning of myocardium
2.     In the ICU:
·      Closely monitor heart ie HR, rhythm, perfusion to other organs
·      Pharmacological support—vasoactive agents are initiated post-op and tapered down gradually as cardiac output, perfusion improves
·      Mechanical support if needed
3.     Currently treating with:
·      Dopamine—preferred:  depressed CO, normal, moderately elevated PL, mod to severe hypotension; MOA:  dose-dependent positive inotropic and chronotropic effects on the myocardium
o   Dose:  conc:  80 mg/100 mL D5W, initial rate: 0.9 ml/h
80 mg/100 ml x 0.9 ml/hr x 1hr/60 min x 1/2.7 kg x 1000 ug/1mg = 4.44 ug/kg/min
reference range:  2-4 ug/kg/min, 4-8 ug/kg/min
o   4-8 ug/kg/min:  stimulation of b1, b2 receptors; increased renal blood flow, heart rate, cardiac contractility, cardiac output
smooth muscle contraction
smooth muscle, cardiac muscle relaxation
heart muscle contraction
smooth muscle relaxation

·      Milrinone—inhibiting PDE III, increases CO, lowers filling pressures, reduces pulmonary artery pressures
o   Dose:  conc: 10 mg/50mL D5W, initial rate: 0.4 ml/hr
10 mg/50 ml x 0.4 ml/hr x 1hr/60 min x 1/2.7 kg x 1000 ug/1mg=0.493 ug/kg/min
reference range: 0.25—1 ug/kg/min
o   0.25—1 ug/kg/min:  systemic and pulmonary vasodilator

·          Prevent cardiovascular collapse
·          Hemodynamic stability
·          Optimize preload
·          Control HR, rhythm and synchrony, perfusion
·          Prevent acidosis

·       HR
·       BP
·       UO
·       End organ function ie Scr, LFT’s
·       Temperature
·       Blood pH

1.  Jaundice ie yellow color of skin
2.  T. Bili levels (12.41 on 9/12, trending down, 10.27 9/14)

1.     Nonpathologic jaundice is caused by
·      Increased bilirubin production—more RBC’s than adults, increased turnover
·      Decreased bilirubin clearance—deficiency of enzyme UGT1A1 til week 14
·      Increased enterohepatic circulation
2.     Normally resolves within 1-2 weeks after birth
3.     Hyperbilirubinemia with T. Bili >25 to 30 mg/dL is associated with increased risk of neurologic dysfunction
4.     Risk factors:  GA <37 weeks, Asian race
5.     Guidelines from the AAP are not available for infants less than 35 weeks GA due to variability in clinical manifestations, spectrum, and lack of reliable and predive measures of bilirubin neurotoxicity.
6.     The guideline to initiate phototherapy from Norway is based on the BW and postnatal age of the preterm infant. In general, for infants > 4 days of age, the following thresholds of TB are used based on BW:
BW >2500 g, but GA between 34 and 37 weeks: 17.5 mg/dL (300 micromol/L)
BW between 1500 and 2500 g: 14.6 mg/dL (250 micromol/L)
BW between 1000 and 1499 g: 11.7 (200 micromol/L)
BW between <1000 g: 8.8 mg/dL (150 micromol/L)
7.     Treatment
·      Phototherapy—conversion of bilirubin to lumirubin, bilirubin isomer, polar molecules
·      Exchange transfusion—if phototherapy failes
·         T. Bili levels within normal limits
·         Resolve jaundice
·         Prevent neurological dysfunction, auditory
·      T. Bili levels
·      Skin discoloration

4. Infection
1.     WBC elevated
2.     afebrile
3.     peripheral blood cx (-) 9/4
4.     surgical wound site cx (-) 9/10
5.     sputum cx (-) 9/13
6.     CRP decreased since 9/11

1.     Patient has persistent leukocytosis despite treatment with antibiotics throughout course
2.     Patient has been afebrile throughout
3.     No cx’s have grown
4.     Currently being treated with Ceftazidime, Vancomycin (9 days)
5.     Ceftaz dose is appropriate
6.     Vanco dose is low, trough on 9/11 was 6.75
7.     Physician changed CVP line on 9/11, opted to stay with current doses of antibiotics
8.     Patient is at risk with many lines
·         Resolve infection
·         Reduce WBC count to normal
·         Next step: consider increase dose of antibiotics
·         Consider adding antifungal agent
·      WBC
·      Temperature
·      S/sx’s of sepsis ie vital signs

One of the most important things I have learned on rotations is to look at patients as a whole and individualize their treatment.  This concept is even more critical in pediatrics.  In adults, slightly overestimating a dose, in most cases, will not have fatal consequences.  In children, it very well can.  Children cannot be treated as miniature adults.  When I was working up patients on the PSICU, there were many things that I had to take into account in addition to the normal parameters, lab values, etc in an adult workup.  The most basic was the patient's size ie weight, height, and head circumference and the percentiles they fit into compared with others of their age.  Secondly, it was important to collect an extensive maternal history, given that the patient him/herself does not a considerable past medical history.  Thirdly, the normal ranges for many lab values (ie potassium, T. bili, albumin, serum creatinine) and vital signs (ie blood pressure, heart rate) changes with age.   Lastly, there was a bigger emphasis on documentation of urine output, especially in neonates where serum creatinine within the first few days of birth is actually indicative of the mother's serum creatinine rather than the child's.  

In this patient, the my concern during the workup was her antibiotic regimen.  Following the patient's cardiac surgery, she was started on ceftazidime and vancomycin for surgical prophylaxis.  Based on the patient's weight and age, she should have been started on q12 dosing of vancomycin at least.  She was treated with daily dosing of vancomycin for a period of 4 days before obtaining a trough that turned out to be 6.75.  After discussing this with my pharmacist, she made the recommendation to the attending physician.  However, he opted to stay with the underdosed vancomycin.  In class and on my ID rotation, I have always learned to "go big or go home" with antibiotics.  Underdosing is merely breeding a resistant strain of the organism.  In addition to the dosing error, the choice of antibiotics was also peculiar to me.  Based on the Antimicrobial Prophylaxis for Surgery guidelines from The Medical Letter, Inc., the common pathogens for a cardiac surgery include Staphylococcus aureus and Staphylococcus epidermidis.  Therefore, the recommended antimicrobials are ONE of the following:  cefazolin, cefuroxime, or vancomycin.  The patient was being treated with two drugs that have similar activity towards the likely pathogens.  

After talking to my preceptor, I found that it comes down to the difference in culture.  Even in the U.S., there are cases when older attendings are set in their ways and are more likely to follow their own experience based medicine rather than the evidence that is out there.  I feel that there is a greater degree of reverence in Taiwan for older generations, that medical residents, etc. do not feel it is their place to disagree with an attending physician.  Although NTUH as an institution preaches evidence based medicine, in some cases, this experience may outweigh evidence.  This is not to say one way better than the other; it merely places the spotlight on a difference in culture.  

Photo of the right and left pleural drainages.

 IV medications for this patient.
Crash cart, present in every patient room.

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