Friday April 20, 2007
Quick way of differentiating non-gap metabolic acidosis


Once you determine from serum chemistry that you have a non-gap metabolic acidosis,

• Check the urine anion gap (UNa + UK – UCl)
• If urine anion gap is positive, it is a renal cause (e.g. RTA; in reality only validated for types I, IV)
• If urine anion gap is negative, the cause is extra-renal.

Mnemonic to remember non gap metabolic acidosis is

HARD UP

Hyperalimentation

Acetazolamide
RTA (Renal)

Diarrhea

Ureterosigmoidostomy

Pancreatic fistula

Related previous pearl: Metabolic acidosis from HIV meds

Wednesday April 18, 2007
(arginine vasopressin) AVP-Receptor Antagonists

Hyponatremia may be caused by a number of conditions, including infections, heart disease, surgery, malignancy, and medication use. Clinical signs and symptoms such as hallucinations, lethargy, weakness, bradycardia, respiratory depression, seizures, coma, and death have been reported. Conventional treatment consists of fluid restriction and administration of hypertonic saline and pharmacologic agents, such as demeclocycline, lithium carbonate, and urea. These treatment options are often of limited effectiveness or difficult for patients to tolerate.

AVP (arginine vasopressin) promotes the reabsorption of water in the renal collecting ducts by activation of V2 receptors, resulting in water retention and dilution of serum solutes. The AVP-receptor antagonists, Conivaptan, Lixivaptan, and Tolvaptan, are being studied for the treatment of hyponatremia.

Conivaptan (Vaprisol) has been shown in clinical trials to increase freewater excretion and safely normalize serum sodium concentrations in patients with hyponatremia and is well tolerated. Also in clinical trials, Lixivaptan and Tolvaptan have safely improved serum sodium concentrations in patients with hyponatremia.

Saturday April 14, 2007
HYPERTONIC SALINE THERAPY

Hypertonic saline is administered for a wide variety of conditions, and this multitude of indications can sometimes seem confusing. Currently, there are 3 primary indications for the use of hypertonic saline in critically ill patients:

• hyponatremic states,
• volume resuscitation in shock,
• brain injury and
• Miscellaneous

Hyponatremic states

1. Syndrome of inappropriate antidiuretic hormone (occasionally indicated)
2. Cerebral salt-wasting syndrome (indicated if hyponatremia
is significant)

3. Other causes (rarely indicated)

• Psychogenic polydipsia
• Diuretic overuse/abuse
• Addison disease
• Excessive losses of gastrointestinal secretions
• Late-stage cirrhosis, congestive heart failure, or renal disease

Volume resuscitation in shock (may be beneficial)

• Hemorrhagic shock
• Septic shock
• Major burns
  

Brain injury (may be beneficial) Traumatic or nontraumatic


Miscellaneous uses

Oral (largely historical)

• Heat-related disorders
• Orthostatic hypotension
• Cystic fibrosis

Parenteral uses

• Sclerotherapy (injected directly into affected vein)
• After coronary artery bypass surgery (intravenous)
• Leishmaniasis (intradermal)
• Midtrimester abortion (intra-amniotic)
  

Related previous pearl:
Hypertonic Solution (3% NS) in cerebral edema and intracranial hypertension