ICU - V/Q mismatch: iNO vs. other pulmonary vasodilators

Since inhaled nitric oxide (iNO) dilates only the ventilated areas of the lung, it enhances the matching of ventilation and perfusion. Whereas, other pulmonary vasodilators - Sildenafil, Prostacycline, etc. dilate all the pulmonary vessels leading to worsening V/Q mismatch.

If there is deterioration in oxygenation after starting one of those latter pulmonary vasodilators, this phenomenon should be considered. Also consider this phenomenon when conversion of iNO to one of these dilators.


CathLab - Microcoil & Catheters

Renegade catheter (now, "Target Catheter"):
?150 cm, Goes over 0.021" guide wire.
Initially, 3 Fr (1 mm). Decreases to 2.5 Fr (0.83 mm) in the last 20 cm at the tip.
Distal 60 cm is also hydrophilic.
Recommended guide catheter lumen 0.042" (1.1 mm). But, this goes through our 4 Fr RCA catheter which is rated for 0.038" wire ("snug fit").

Microcoil comes loaded in a "plastic needle" with hub. There is short plunger for initial transfer to delivery catheter. After transfer of coil to the catheter, the "Pusher wire" is used for deployment.

Rapid Transit catheter: (Cordis)
150 cm, Goes over 0.021" guide wire
Initially 2.8 Fr (for 100 cm from the hub, Double-braided)
Distally, 2.3 Fr (for the last 50 cm, Single-braided)
Recommended guide catheter lumen 0.042" (1.1 mm). But, it goes through our 4 Fr RCA catheter which is rated for 0.038" wire ("snug fit").

LV Non-Compaction by Angiogram

4 wk old; Presented with arrhythmia, Circulatory shock and respiratory distress.

Images from Hughes et al. Cardiology in the Young 2007;17:56-63

See also the other posting on this subject.


ICU: Blood Lactate Level

Monitoring blood lactate level helps to monitor tissue oxygenation during critical illness.
Below 2 mmol/L is normal.
Above 4 mmol/L is abnormal.
Between 2 & 4 mmol/L is gray zone.

Reasons for elevated Lactate level:
1) Anerobic metabolism is activated - presumably due to oxygen demand exceeding oxygen delivery at tissue level. In other words, VO2 is less than the metabolic rate. (Treatement will be to either decrease metabolic demand - Sedation/stopping feeds or increase VO2 above 160 ml/min/m2.
2) Hepatic insufficiency (Impaired clearance)
3) Gram negative sepsis with endotoxemia. Endotoxin inhibits pyruvate dehydrogenase, the enzyme that initiates pyruvate oxidation in mitochondria. So, endotoxemia causes hyperlactatemia without  cellular oxygen deprivation in gram-negative sepsis.
3) Thiamine deficiency (Blocks pyruvate entry into mitochondria)
4) Alkalosis (both metabolic and respiratory) causes increased activity of pH-dependent enzymes in glycolytic pathway that promotes lactate production. pH has to exceed 7.6 for this effect to show. However, in the presence of liver dysfunction, the lactate clearance will be less than normal and therefore, this effect may result in hyperlactatemia at lower pH. (Alkalosis induced hyperlactatemia is an undesirable consequence of alkali therapy for lactic acidosis).
5) Other causes of hyperlactatemia:
    (a) Epinephrine infusion (enhanced glycogenolysis with increased production of lactate)
    (b) Nitroprusside infusion (from cyanide accumulation, sign of cyanide intoxication and therefore, is an ominous sign)
    (c) Acute asthma (possibly increased lactate production from respiratory muscles)
    (d) Seizures (transient)
6) Increased production by enteric microbes (D-lactic acid). ...usual lactate the we talk about is L-isomer of lactate (levo). D-lactate is not measured in usual lab tests. Therefore, this will manifest as widened Anion gap with normal L-lactate level. Some labs can perform D-lactate estimation upon request.

From: The ICU book. Paul Marino (2nd Ed. 1997)


Gen: Segmental formulae

Dr. Richard van Praagh's formulae for description of cardiac segments
(Circulation 1977;56:139-143)

CathLab: Lung segments

CathLab/ICU: Cardiac Tamponade/Pericardiocentesis

Netter diagrams:

CathLab: Access

Groin Anatomy:

SVT - Onset, Termination - Rentry Mechanism

Abrupt onset and termination

EKG trace of onset of SVT

Onset EKG alone...an ectopy starts the SVT


ICU: Methemoglobin (Nitric oxide and Methylene blue) & CyanmetHb (Nitroprusside & Nitroglycerin)

Methemoglobin forms when iron in ferrous form in Hb is oxidized to ferric form. Nitric oxide does that. If metHb level exceeds 1.5 g% (10% of a presumed normal 15 g% i.e. 15 g/dL), it needs to be treated.
Patient may appear cyanotic. Oxygen saturations fall.

Methylene blue 1-2 mg/kg/dose IV is the treatment.

Beware, when you use methylene blue infusion in patients receiving inotropes/vasopressor agents such as Norepinephrine or Dopamine. Methylene blue is MAOI and therefore, potentiates effect of these medications by several folds by decreasing the reuptake of NE or Dopamine at the nerve synapses.

Methylene blue is also serotonin reuptake inhibitor. So, can cause serotonin crisis in patients receiving SSRIs (e.g. anti-depressive agents) esp. at doses > 5 mg/kg.

Methylene blue - Wikipedia, the free encyclopedia: "Methylene blue also blocks accumulation of cyclic guanosine monophosphate (cGMP) by inhibiting the enzyme guanylate cyclase: this action results in reduced responsiveness of vessels to cGMP-dependent vasodilators like nitric oxide and carbon monoxide."...and ?Milrinone!

CyanmetHb forms from the cyanide which is part of Nitroprusside molecular structure. This is more common in postop. cardiac patient because of availability of more Hb in plasma due to hemolysis during cardiopulmonary bypass. Antidote: Sodium thiosulphate or Sodium nitrite.