1. Diagnosis: Intrathoracic large airway obstruction / Tracheal compression.
2. CT scan finding: Vascular sling (e.g., pulmonary artery sling / double aortic arch) around the trachea causing extrinsic compression and severe luminal narrowing.
3. Initial management:
   • Position of comfort, gentle handling, humidified oxygen.
   • Minimal sedation if agitated.
   • If intubation is needed, perform under controlled anesthesia using the smallest appropriate endotracheal tube with ENT/surgical backup.
4. Definitive treatment: Cardiovascular surgical repair/reconstruction to relieve the vascular ring/sling compression.

• 1. Cingulate (Subfalcine) herniation
• 2. Central (Transtentorial) herniation
• 3. Uncal (Transtentorial) herniation
• 4. Transcalvarial (External) herniation
• 5. Upward (Cerebellar / Transtentorial) herniation
• 6. Tonsillar herniation (Downward cerebellar / foramen magnum herniation)

1. Metabolic disorder: High Anion Gap Metabolic Acidosis (HAGMA) with high osmolar gap.
   • $\text{Anion Gap}={\text{Na}}^{+}-({\text{Cl}}^{-}+{\text{HCO}}_3^{-})=138-(96+10)=32\text{ mEq/L}$ (High).
2. Cause: Propylene glycol toxicity (propylene glycol is used as a vehicle/solvent in parenteral midazolam, lorazepam, and phenytoin infusions).
3. Supporting evidence:
   • $\text{Calculated Osmolality}=2\times \text{Na}+\frac{\text{Glucose}}{18}+\frac{\text{BUN}}{2.8}=2(138)+4.4+1.4=282\text{ mOsm/kg}$.
   • $\text{Osmolal Gap}=\text{Measured}-\text{Calculated}=346-282=64\text{ mOsm/kg}$ (Normal $<10\text{ mOsm/kg}$).
4. Other causes of high osmolar gap metabolic acidosis:
   • Toxic alcohols: Methanol, Ethylene glycol, Isopropanol
   • Drugs/Solvents: Salicylates, IV Phenytoin, IV Melphalan, IV Lorazepam
   • Alcoholic or diabetic ketoacidosis, severe lactic acidosis

Correct Answer: Only (e) — Lung disease with intra-pulmonary shunting.

Explanation:

• (a) Anemia: Lowers total oxygen content (${\text{CaO}}_2$), but arterial ${\text{paO}}_2$ (dissolved oxygen) and ${\text{SaO}}_2$ are normal.
• (b) Carbon monoxide poisoning: Decreases ${\text{SaO}}_2$ and shifts curve to the left, but dissolved ${\text{paO}}_2$ remains normal.
• (c) and (d) Abnormal hemoglobins (affinity shifts): Shift the oxyhemoglobin dissociation curve affecting ${\text{SaO}}_2$ and ${\text{P}}_{50}$, but do not alter dissolved arterial ${\text{paO}}_2$.
• (e) Intra-pulmonary shunting: Directly results in venous admixture and decreased arterial ${\text{paO}}_2$.

Patient A is more hypoxemic.

Reasoning:
Hypoxemia reflects inadequate oxygen carriage in blood. Total arterial oxygen content (${\text{CaO}}_2$) is calculated as:
${\text{CaO}}_2=(1.34\times \text{Hb}\times {\text{SaO}}_2)+(0.003\times {\text{paO}}_2)$

• Patient A:
  ${\text{CaO}}_2\approx 1.34\times 7\times 0.95=8.91\text{ mL }{\text{O}}_2/\text{dL}$
• Patient B:
  ${\text{CaO}}_2\approx 1.34\times 15\times 0.85=17.08\text{ mL }{\text{O}}_2/\text{dL}$

Although Patient A has a higher ${\text{paO}}_2$ ($85\text{ mmHg}$ vs $55\text{ mmHg}$), the severe anemia in Patient A results in nearly half the oxygen carrying capacity of Patient B.

1. CXR finding: Massive cardiomegaly ("water-bottle" heart / globular cardiac shadow) suggestive of massive pericardial effusion with right mid-zone consolidation.
2. Acute emergency therapy: Pericardiocentesis.
   • Technique: Subxiphoid approach — insert needle at a $30\text{–}{45}^{\circ }$ angle between the xiphoid process and left costal margin aiming towards the left shoulder under continuous aspiration and echocardiographic / ECG guidance.
3. Indications:
   • Clinical features of cardiac tamponade / obstructive cardiogenic shock (Beck's triad, pulsus paradoxus).
   • Echocardiographic signs of tamponade (diastolic collapse/buckling of right atrium or right ventricle).
   • Diagnostic aspiration in purulent/suspected tubercular pericarditis.

1. CT scan finding: Acute right-sided crescentic subdural hematoma with significant midline shift and mass effect.
2. Immediate management:
   • Airway, Breathing, Circulation (ABC): Endotracheal intubation with in-line cervical stabilization.
   • Controlled ventilation to prevent hypoxia and hypercapnia (target ${\text{pCO}}_2$ 35–38 mmHg).
   • Acute neuroprotective measures: Head end elevation ${30}^{\circ }$, neutral neck position, analgesia/sedation.
3. Further management:
   • Urgent neurosurgical consultation for craniotomy and surgical evacuation of the hematoma.
   • Osmotherapy: Mannitol ($0.25\text{–}1\text{ g/kg}$) or 3% Hypertonic Saline ($3\text{–}5\text{ mL/kg}$).
   • Maintain Cerebral Perfusion Pressure ($\text{CPP}=\text{MAP}-\text{ICP}\ge 50\text{–}60\text{ mmHg}$).
4. Electrolyte disturbance: Hyponatremia (due to SIADH or Cerebral Salt Wasting syndrome).

1. Diagnosis: Diabetic Ketoacidosis (DKA) in newly presenting Type 1 Diabetes Mellitus.
2. First hour therapy: Fluid resuscitation with Normal Saline ($0.9\mathrm{\%}\text{ NaCl}$) at $10\text{–}20\text{ mL/kg}$ over 1 hour (no insulin bolus in the first hour).
3. Actions for ${\text{K}}^{+}=2.8\text{ mEq/L}$:
   • Temporarily pause or reduce regular insulin infusion (to $0.05\text{ U/kg/hr}$).
   • Increase potassium replacement in IV fluids up to $40\text{–}60\text{ mEq/L}$ (as KCl/KPO4).
   • Monitor continuous ECG and recheck serum potassium hourly.
4. Risk factors for cerebral edema:
   • Younger age ($<3\text{–}5\text{ years}$), new-onset T1DM, longer duration of symptoms.
   • Severe acidosis ($\text{pH}<7.1$), lower ${\text{pCO}}_2$, elevated initial BUN.
   • Administration of sodium bicarbonate.
   • Rapid infusion of hypotonic fluids or excessive fluid volume ($>4{\text{ L/m}}^2/\text{day}$).
   • Attenuated or failing rise in serum sodium during therapy.
5. Mortality predictors: Cerebral edema and severe refractory hypokalemia / cardiac arrhythmias.

1. Condition: Acute Respiratory Distress Syndrome (ARDS) / Acute Lung Injury (ALI).
2. Diagnostic Criteria (AECC / Berlin Criteria):
   • Timing: Acute onset within 1 week of a known clinical insult or new/worsening respiratory symptoms.
   • Chest Imaging: Bilateral opacities/pulmonary infiltrates on CXR or CT not fully explained by effusions, atelectasis, or nodules.
   • Origin of Edema: Respiratory failure not fully explained by cardiac failure or fluid overload (PAOP $\le 18\text{ mmHg}$ or no left atrial hypertension).
   • Oxygenation (on PEEP $\ge 5{\text{ cmH}}_2\text{O}$):
     • Mild ARDS: ${\text{paO}}_2/{\text{FiO}}_2=201\text{–}300\text{ mmHg}$ (formerly ALI)
     • Moderate ARDS: ${\text{paO}}_2/{\text{FiO}}_2=101\text{–}200\text{ mmHg}$
     • Severe ARDS: ${\text{paO}}_2/{\text{FiO}}_2\le 100\text{ mmHg}$

1. Diagram: Left Ventricular Pressure-Volume Loop (or Wiggers diagram of cardiac cycle).
2. Axes:
   • X-axis: Left Ventricular Volume ($\text{mL}$)
   • Y-axis: Left Ventricular Pressure ($\text{mmHg}$)
3. Phases:
   • Isovolumetric contraction
   • Rapid ventricular ejection
   • Isovolumetric relaxation
   • Ventricular filling period

1. Graph: Michaelis-Menten / Capacity-limited saturation pharmacokinetics (transition from first-order to zero-order elimination kinetics as drug concentration rises).
2. Definitions:
   • First-order kinetics: The rate of drug elimination is directly proportional to plasma drug concentration (constant fraction or percentage of drug eliminated per unit time; constant half-life).
   • Zero-order kinetics: The rate of drug elimination is constant and independent of plasma drug concentration (constant amount of drug eliminated per unit time; enzyme pathways are saturated).
3. Drug example: Phenytoin (also Aspirin/Salicylates, Alcohol/Ethanol).

1. Diagnosis: Acute Tumor Lysis Syndrome (TLS).
2. Initial therapeutic doses:
   • Hydration: $3000{\text{ mL/m}}^2/\text{day}$ (or $1.5\text{–}2\times$ maintenance) without potassium.
   • Allopurinol: $10\text{ mg/kg/day}$ (or $300\text{–}400{\text{ mg/m}}^2/\text{day}$) divided tid.
   • ${\text{NaHCO}}_3$: $50\text{–}80\text{ mEq/L}$ (routine alkalization is controversial and generally avoided if hyperphosphatemia/hypocalcemia is present).
3. Monitoring: Urine output ($>3\text{ mL/kg/hr}$ or $>100{\text{ mL/m}}^2/\text{hr}$), urine specific gravity/pH, daily weights, serum electrolytes (${\text{K}}^{+},{\text{Ca}}^{2+},{\text{PO}}_4^{3-}$), uric acid, BUN/Creatinine every 4–6 hours, and ECG for hyperkalemia.
4. Choice of dialysis: Hemodialysis (or Continuous Renal Replacement Therapy / CRRT).
5. Newer modality: Rasburicase (recombinant urate oxidase) — directly converts insoluble uric acid to highly soluble allantoin.

1. Abnormality: Malpositioned umbilical arterial catheter (e.g., tip coursing abnormally into the subclavian artery or carotid artery).
2. Ideal Positions:
   • UAC (Umbilical Arterial Catheter):
     • High line: T6 to T9 (thoracic aorta, above diaphragm, between ductus arteriosus and celiac axis).
     • Low line: L3 to L4/L5 (abdominal aorta, between inferior mesenteric artery and aortic bifurcation).
   • UVC (Umbilical Venous Catheter): Inferior vena cava (IVC) at the junction with the right atrium (just above diaphragm, level T8–T9).
3. Management of pale lower limb (vasospasm/thrombosis):
   • Reflex vasodilation: Warm the contralateral (opposite) limb.
   • If pallor persists $>15\text{–}30\text{ minutes}$, immediately remove the umbilical arterial catheter.
4. Level of renal arteries: L1–L2 vertebral level.
5. Maintenance of UAC: Continuous flush with heparinized saline ($0.5\text{–}1.0\text{ U/mL}$) at $0.5\text{–}1.0\text{ mL/hr}$, strict asepsis, and avoid administering vasoactive drugs/blood products through UAC.

1. Immediate complication: Upper airway obstruction and inhalational injury.
   • Identification: Singed facial/nasal hairs, soot/carbonaceous sputum in oropharynx, hoarseness of voice, stridor, tachypnea, severe burns to the face and neck.
2. Key management steps:
   • Airway maintenance with early endotracheal intubation (before airway edema worsens).
   • High-flow 100% humidified oxygen.
   • Establish large-bore IV access (avoid burnt skin if possible) and start prompt fluid resuscitation.
   • Analgesia/pain control and prevention of hypothermia.
3. Fluid resuscitation (Parkland Formula):
   • Burn Resuscitation Fluid:
     $\text{Volume}=4\text{ mL}\times 16\text{ kg}\times 60=3840\text{ mL of Ringer’s Lactate}$
     • First 8 hours: $1920\text{ mL}$
     • Next 16 hours: $1920\text{ mL}$
   • Plus Maintenance Fluid:
     • For $16\text{ kg}=1000+(6\times 50)=1300\text{ mL/24 hr}$
   • Total 24-hr fluid: $3840+1300=5140\text{ mL}$.

1. Diagnosis: Infantile Hypertrophic Pyloric Stenosis (IHPS).
2. ABG and Electrolytes: Hypochloremic, Hypokalemic Metabolic Alkalosis with elevated ${\text{HCO}}_3^{-}$ and compensatory elevated ${\text{pCO}}_2$ (paradoxical aciduria may be seen).

1. Reactive NST: Baseline heart rate 120–160 bpm with normal baseline variability and $\ge 2$ fetal heart rate accelerations of $\ge 15\text{ bpm}$ lasting $\ge 15\text{ seconds}$ over a 20-minute recording window.
2. Chronic Lung Disease (CLD / BPD): Requirement for supplemental oxygen $\ge 28\text{ days}$ in infants born $<32$ weeks PMA assessed at 36 weeks post-menstrual age (or $>28$ days of life for infants $\ge 32$ weeks).
3. Permissive Hypercapnia: A ventilatory strategy where mild-to-moderate respiratory acidosis (${\text{pCO}}_2=55\text{–}65\text{ mmHg}$, $\text{pH}\ge 7.20\text{–}7.25$) is accepted to minimize ventilator-induced lung injury (barotrauma/volutrauma).
4. Modified Bell's Staging for NEC:
   • Stage I (Suspect NEC): Temperature instability, lethargy, abdominal distension, heme-positive stools, normal/ileus X-ray.
   • Stage II (Definite NEC): Absent bowel sounds, abdominal tenderness, metabolic acidosis, thrombocytopenia, pneumatosis intestinalis / portal venous gas on X-ray.
   • Stage III (Advanced NEC): Shock, DIC, peritonitis, impending/proven perforation (pneumoperitoneum).
5. Threshold ROP: $\ge 5$ contiguous or $\ge 8$ cumulative clock hours of Stage 3 ROP in Zone I or Zone II in the presence of "plus" disease.