You will be presented with the full text of a biomedical research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
hyperkalemia affects the myocardial tissue producing electrocardiographic abnormalities , such as prolongation of p - r interval , tall peaked t waves , a reduction in the amplitude and an increase in the duration of p wave , and atrial and ventricular arrhythmias , including variable degree heart blocks .
a 97-year - old female presented to the emergency department complaining of dizziness and syncope .
the syncope occurred at rest , without incontinence , tongue bite or residual neurological deficit .
it was not precipitated by chest pain , difficulty in breathing or any other symptoms . the patient s medical history included diabetes mellitus , hypertension and asthma .
on initial examination , her blood pressure was 100/62 mm / hg , heart rate 56 beats - per - minute and regular with no orthostatic changes in vital signs .
cardiovascular examination revealed normal first and second heart sounds with grade 2 systolic murmur in the mitral and pulmonary auscultation areas .
laboratory findings included hemoglobin 13.1 g / dl , troponin 0.029 , urea nitrogen 19 mg / dl , creatinine 1.6 mg / dl , potassium 6.3 meq / l , sodium 128
meq / l , chloride 97 mm / l , glucose 262 mg / dl .
echocardiogram ( ecg ) showed sinus arrest and ventricular escape rhythm at a rate of 30 beats per minute with left axis deviation ( figure 1a ) . 

( b ) a 97-year old female with syncope : heart block resolved within 24 h. a ) 97-year - old female with syncope , initial ecg .
( b ) a 97-year old female with syncope : heart block resolved within 24 h. the patient was initially treated with intravenous calcium chloride , and intravenous infusion of normal saline , insulin and glucose . serum potassium subsequently decreased to 3.8
meq / l within a 24 h period and the ecg showed normal sinus rhythm at a rate of 68 with no signs of heart block ( figure 1b ) .
altered atrioventricular conduction was attributed to the presence of mild hyperkalemia with decreased creatinine clearance and this was most likely the cause of the syncope .
the resolution of the hyperkalemia was achieved after withdrawal of valsartan therapy suggesting that this drug was responsible for the electrolyte disturbance in conjunction with diabetes and an age - related reduction in glomerular filtration rate ( gfr ) .
an 86-year old female with medical history significant for hypertension , asthma and atrial fibrillation was brought to the emergency department by her family after they had noticed changes in her mental status .
initial blood pressure was 70/46 mmhg , and heart rate 30 beats - per - minute . on physical examination , the patient was diaphoretic and in mild respiratory distress .
cardiovascular examination revealed normal heart sounds with no murmurs , lung sounds were clear bilaterally , and mucosa membranes were dry .
laboratory findings were significant for hemoglobin 11.4 g / dl , troponin 0.035 ng / ml , urea nitrogen 67 mg / dl , creatinine 2.2 mg / dl , potassium 5.7 meq / l , sodium 137 meq / l , chloride 101 mm / l , glucose 170 mg / dl .
the patient was given 1 mg of atropine and 2 l of normal saline followed by transvenous pacemaker due to refractory hypotension with bradycardia .
her treatment also included insulin with dextrose and continuous administration of normal saline for presumptive dehydration .
potassium levels normalized to 4.2 over the next two days and no further heart block was observed .
dehydration and acute renal failure were determined to be the cause of the patient s hyperkalemia .
the patient s family was advised to monitor her volume status and oral intake of food containing potassium .
a 70-year old male with significant medical history of diabetes , hypertension and atrial fibrillation was admitted to the hospital for difficulties in breathing and weakness .
blood pressure on presentation was 86/50 mmhg , heart rate 38 beats - per - minute , respiration 24 times a minute , and temperature 96.4 f. on physical examination , he was in mild respiratory distress .
cardiovascular examination revealed normal heart sounds , bibasilar crackles , and ( + 1 ) pitting edema . laboratory findings included : hemoglobin 10.8 g / dl , troponin 0.020 ng / ml , urea nitrogen 47 mg / dl , creatinine 2.1 mg / dl , potassium 6.1 meq / l , sodium 136 meq / l , chloride 105 mm / l , glucose 226 mg / dl .
ecg revealed sinus arrest with high - grade heart block and a junctional escape rhythm ( figure 2a ) . 

the patient was treated with calcium chloride 1 gm i.v . , insulin 10 units i.v . and dextrose 50 ml of 50% solution .
meq / l within 24 h , and follow - up ecg revealed normal sinus rhythm ( figure 2b ) with no signs of a heart block .
complete heart block was attributed to the presence of mild hyperkalemia caused by the patient s medication in the setting of renal insufficiency and was most likely the cause of the patient s symptoms .
early in the 19 century , prior to the introduction of more acceptable antiarrhythmics , potassium salts were used clinically to treat atrial and ventricular arrhythmias .
it was hypothesized that such an alteration could terminate an arrhythmia by suppressing ectopic foci .
however , the use of this agent fell out of favor , as potassium on its own can provoke arrhythmia and heart blocks .
it is worth noting that the occurrence of hyperkalemia in hospitalized patients is close to 8% and untreated hyperkalemia - associated mortality can reach up to 67% .
acute renal failure complicates about 5% of hospital admissions but this percentage is much higher in elderly patients and probably contributes to renal hypoperfusion ( prerenal azotemia ) which is rapidly reversible upon restoration of renal blood flow .
elderly patients are principally predisposed to developing hyperkalemia due to age - related decline in their renal function , environmental challenges leading to volume depletion , the presence of diabetes mellitus , cardiovascular diseases , obstructive nephropathy , the use of certain medications and overzealous potassium diets ( table 1 ) .
drug induced hyperkalemia is of clinical importance as the concept of polypharmacy is more common in the geriatric population because of the presence of multiple co - morbidities .
usually causes of hyperkalemia can be identified by taking a careful detailed history and evaluating relevant laboratory findings .
it is not uncommon to see a geriatric patient with a heart block or a presentation of syncope due to the presence of multiple medical problems and lower tolerance for electrolyte disturbances .
however , it is imperative to make an attempt to correct the underlying disorder causing electrolyte imbalance prior to making a decision which could subject the patient to a more invasive workup .
most of the total body potassium is present in the intracellular space and is estimated to be close to 98% , with the rest of the potassium found in the extracellular space . under normal circumstances , almost 90% of potassium is eliminated by renal excretion and the rest by the colon .
nevertheless , age - related decline in egfr impairs renal potassium excretion which is mainly associated with loss of nephron mass , as the process involves renal tubular secretion . the number of collecting ducts is directly related to the egfr and renal potassium excretion .
therefore , geriatric patients are more prone to electrolyte disturbances causing abnormal conduction through the heart tissue . 

table 1causes of hyperkalemia in the elderly.drugspotassium sparing diuretics ( spironolactone , eplerenone , triamterene , amiloride ) , nsaids , ace inhibitors , arbs , beta blockers , heparin , digoxin intoxication , trimethoprim , succinylcholinepseudohyperkalemialeukocytosis , thrombocytosis , hemolysis , rheumatoid arthritis , mononucleosis.renal failureacute or chronic ( dehydration , obstructive nephropathy , atn , etc.).mineralocorticoid deficiencyaddison s disease , hyporeninemic hypoaldosteronism.tissue necrosiscrush injury , tumor lysis , burns.metabolic derangementacidosis , insulin deficiency.potassium intakesupplements , e.g. kdur , food ( orange , banana , mango , etc . ) , salt substitutes , enteral nutritions ( ensure , pulmocare , glucerna ) , blood transfusions 
  the presence of hyperkalemia causes a reduction in the resting transmembrane potential , a decrease in the rate of rise of the action potential , and a decrease in myocardial cell conduction velocity , with an increase in the rate of repolarization . as the action potential shortens with increasing potassium levels and the conduction velocity decreases , the pr - interval is prolonged , the p - wave ultimately disappears , t - waves become peaked , qrs widens and r - r intervals become irregular . consequently , electrocardiographic findings include the changes in the underlining atrioventricular junctional rhythm accompanied by acceleration of junctional pacemaker , leading to conduction delays in the his - purkinje system with generation of heart blocks .
a rapid increase in potassium levels can lead to bradycardia and depression of contractile force , and could be associated with ventricular fibrillation . on the other hand , a slow increase in potassium levels are more likely to cause conduction prolongation followed by asystole , as reported by ettinger in 1974 . in one study of 26 patients with mild to moderate hyperkalemia ,
81% presented with third degree heart block , with 50% of these patients requiring temporary pacing .
prevention of hyperkalemia can be achieved by adjusting the medication regimen and taking into consideration reduced renal function .
for example , potassium sparing diuretics can lead to dehydration and volume depletion , in addition to impairment of potassium secretion , and should be used with caution in patients with a history of diabetes or urinary tract obstruction .
use of non - steroidal anti - inflammatory drugs ( nsaids ) should be avoided in geriatric patients with renal insufficiency , heart failure or liver cirrhosis as it can exacerbate pre - existing condition and electrolyte balance .
therefore , any dose increase must be managed with caution as hyperkalemia can occur ( table 2 ) .
management of hyperkalemia includes stabilizing the myocardium to prevent deadly arrhythmias and shifting of potassium into the cells .
calcium gluconate 10% solution or calcium chloride can rapidly antagonize the toxic effect of hyperkalemia by lowering the threshold potential , and its onset of action is usually within a few minutes . reducing plasma potassium concentrations by increasing intracellular movement of potassium can be achieved by using regular insulin 10 units with dextrose 50% solution intravenously .
also , beta agonist such as albuterol 1020 mg when administered by a nebulizer can decrease potassium within two hours by cellular potassium uptake .
sodium polystyrene 3060 gm binds to potassium in the colon and can prevent further absorption of potassium ; hence , removing excess potassium .
intravenous hydration with the use of loop diuretics is also an efficient way of removing potassium from the body .
sodium bicarbonate therapy is controversial and should be reserved for patients with academia . in patients presenting with severe hyperkalemia and decreased renal function , hemodialysis should be considered as this would be the fastest way to correct hyperkalemia . in geriatric patients presenting with renal failure and hyperkalemia , urinary tract obstruction investigation should be included in the initial workup and a high emphasis should be placed on the evaluation of the medications which can disrupt potassium balance in the context of the clinical picture and pre - existing medical problems such as diabetes , chronic kidney disease , hypertension , hypoaldosteronism and excessive potassium intake . 

table 2mechanism of action for drug - induced hyperkalemia.spironolactone , eplerenonealdosterone antagonist by binding to cytoplasmic aldosterone 
 receptors , inhibits potassium secretion and sodium reabsorption.triamterine/amilorideblocks na channels in principal cells.nsaidsreduce renal blood flow , inhibit renal prostaglandin synthesis , decrease renal blood perfusion.beta blockerssuppress catecholamine stimulated rennin release , decrease aldosterone levels and impair cellular uptake of potassium.angiotensin converting enzyme inhibitorsdecrease renal blood perfusion , decreases gfr , aldosterone.heparininhibits adrenal aldosterone production.trimethoprim ( component of bactrim)blocks potassium secretion by blocking na channels in principal cells.digoxin intoxicationdisrupts na k atpase transporter , prevents intracellular potassium uptake . 

in our patients , mild hyperkalemia secondary to the use of ace inhibitor and dehydration , generated depression of the excitability and conduction velocity of the pacemaker cells causing variable degree heart blocks , hypotension and cardiogenic syncope .
elderly patients should be monitored closely as hyperkalemia and reduced renal function can predispose them to complete heart blocks , cardiac syncope and sudden cardiac death .
consequently , physicians should be more vigilant even in the case of a mild rise of potassium in the geriatric population presenting with heart blocks since sinus rhythm can be appropriately restored without subjecting the patient to further invasive workup .
hyperkalemia affects the myocardial tissue producing electrocardiographic abnormalities , such as prolongation of the p - r interval , tall peaked t waves , a reduction in the amplitude and an increase in the duration of p wave , and atrial and ventricular arrhythmias , including variable degree heart blocks . 
 elderly patients are particularly predisposed to developing hyperkalemia and the associated abnormalities due to an age - related reduction in glomerular filtration rate and pre - existing medical problems . 
 therefore , the impact of aging on potassium homeostasis must be taken into consideration , and preventive measures , such as early recognition of possible hyperkalemia in the geriatric population treated with certain medications or supplements must be investigated . 
 the threshold for cardiac arrhythmias in the elderly can be lower than the general population . 
 we report 3 unusual cases of mild hyperkalemia in elderly patients presenting with hypotension , syncope and variable degree heart blocks which resolved spontaneously with the correction of hyperkalemia .