188 - Digitalis toxicity

*Reduced tolerance of digoxin may be seen in (factors predisposing to digitalis toxicity) :
 - Advanced age
- Acute Myocardial Infarction/ Ischemia/ Hypoxemia
- Magnesium depletion (hypomagnesemia)

- Hypercalcemia (Calcium synergises with digitalis and precipitates its toxicity)
- Hypothyroidism (Both hyperthyroidism and hypothyroidism enhance digitalis toxicity. Thyrotoxicosis patients are more prone to develop digitalis arrhythmias and Myxedema enhances responsiveness to digitalis. Myxedema patients eliminate digoxin more slowly)
- Renal insufficiency (Digoxin is mainly excreted by kidneys)

- Electrical cardioversion 

* Digitalis toxicity causes hyperkalemia, but hypokalemia enhances digitalis toxicity (by increasing its binding to Na+/K+ ATPase.

*The administration of the following drugs raises the serum concentration of digoxin :
- Quinidine
- Verapamil
- Procainamide
- Amiodarone

*MANAGEMENT OF DIGITALIS OVERDOSE :

- Withdrawl of the drug
- Potassium (administer cautiously and by oral route whenever possible if hypokalemia is present. Potassium must not be employed in the presence of A-V block or hyperkalemia.
- Phenytoin/Beta blocker or Lidocaine : Lidocaine is effective in treatment of digitalis induced ventricular tachyarrythmias.
- Cardiac pacemaker : may be required in digitalis induced A-V block.
- Electrical conversion : may be life saving in digitalis induced ventricular fibrillation 
- FAB fragments/ digitalis antibodies : are potentially life saving in severe intoxication 
- Hemodialysis is not useful in digoxin toxicity .

(Other conditions where hemodialysis is ineffective is Digoxin poisoning, Kerosene poisoning, Benzodiazepine poisoning and Organophosphate poisoning)

(Remember that Digoxin and Digitoxin are two different drugs, both derived from digitalis, But digitoxin is mainly excreted by liver and digoxin is mainly excreted by kidneys. Hence digoxin dosage need not be adjusted in liver failure and digitoxin dosage need not be adjusted in renal failure)

*The most lipid soluble cardiac glycoside is Digitoxin.
*The most rapidly absorbed oral glycoside is digitoxin.

187 - Metabolic syndrome - Clinical identification

Clinical Identification of the Metabolic Syndrome—Any Three Risk Factors

Risk Factor Defining Level Abdominal obesitya   Men (waist circumference)b >102 cm (>40 in.)   Women >88 cm (>35 in.) Triglycerides >1.7 mmol/L (>150 mg/dL) HDL cholesterol   Men <1.0 mmol/L (<40 mg/dL)   Women <1.3 mmol/L (<50 mg/dL) Blood pressure greater than or equal to 130/greater than or equal to 85 mmHg Fasting glucose >6.1 mmol/L (>110 mg/dL)

aOverweight and obesity are associated with insulin resistance and the metabolic syndrome. However, the presence of abdominal obesity is more highly correlated with the metabolic risk factors than is an elevated body-mass index (BMI). Therefore, the simple measure of waist circumference is recommended to identify the BMI component of the metabolic syndrome. bSome male patients can develop multiple metabolic risk factors when the waist circumference is only marginally increased, e.g., 94–102 cm (37–39 in.). Such patients may have a strong genetic contribution to insulin resistance. They should benefit from life-style changes, similarly to men with categorical increases in waist circumference.