[The best of cardiac failure in 2005]

The year 2005 saw the validation of resynchronisation treatment of cardiac failure with improved mortality in certain symptomatic patients under optimal medical therapy with QRS duration >150 msec. The implantable defibrillator has ousted the last antiarrhythmic drug, amiodarone, on which hopes for a reduction in mortality had been based. The positive inotropic agents have thrown their last reserves into the fight against cardiac failure: the anti-endothelins have not yet been shown to have significant benefits. The year 2005 was also the year of recommendations: European in acute and chronic heart failure, and American. The importance of clinical practice has been emphasised by the role given to registers. Finally, the diseases change: cardiomyopathy of stress is recognised in this stressful era; the importance of polypathology is increasingly understood in the elderly; the importance of renal function has been underlined although the method of its evaluation is less clear. As usual, there have been many advances in 2005, difficult to summarise in just a few lines.

Preventing neurological complications from dysnatremias in children

Dysnatremias are among the most common electrolyte abnormalities encountered in hospitalized patients. In most cases, a dysnatremia results from improper fluid management. Dysnatremias can occasionally result in death or permanent neurological damage, a tragic complication that is usually preventable. In this manuscript, we discuss the epidemiology, pathogenesis and prevention and treatment of dysnatremias in children. We report on over 50 patients who have suffered death or neurological injury from hospital-acquired hyponatremia. The main factor contributing to hyponatremic encephalopathy in children is the routine use of hypotonic fluids in patients who have an impaired ability to excrete free-water, due to such causes as the postoperative state, volume depletion and pulmonary and central nervous system diseases. The appropriate use of 0.9% sodium chloride in parenteral fluids would likely prevent most cases of hospital-acquired hyponatremic encephalopathy. We report on 15 prospective studies in over 500 surgical patients that demonstrate that normal saline effectively prevents postoperative hyponatremia, and hypotonic fluids consistently result in a fall in serum sodium. Hyponatremic encephalopathy is a medical emergency that should be treated with hypertonic saline, and should never be managed with fluid restriction alone. Hospital-acquired hypernatremia occurs in patients who have restricted access to fluids in combination with ongoing free-water losses. Hypernatremia could largely be prevented by providing adequate free-water to patients who have ongoing free-water losses or when mild hypernatremia (Na>145 mE/l) develops. A group at high-risk for neurological damage from hypernatremia in the outpatient setting is that of the breastfed infant. Breastfed infants must be monitored closely for insufficient lactation and receive lactation support. Judicious use of infant formula supplementation may be called for until problems with lactation can be corrected.

A study of current fluid prescribing practice and measures to prevent hyponatraemia in Northern Ireland's paediatric departments

Guidance on the prevention of hyponatraemia in children was issued by DHSSPSNI in March 2002. Two years later Dr Henrietta Campbell, the Chief Medical Officer, wrote to the Chief Executives of acute and combined trusts to seek assurances that the guideline had been incorporated into clinical practice and its implementation monitored. This paper reports the findings of the first prospective study undertaken to examine practice following introduction of the guidance. The evidence suggests that implementation has so far been incomplete and highlights problem areas. The paper reflects on potential explanations for the findings and makes practical suggestions for improvement.

Nutritional considerations in triathlon

Triathlon combines three disciplines (swimming, cycling and running) and competitions last between 1 hour 50 minutes (Olympic distance) and 14 hours (Ironman distance). Independent of the distance, dehydration and carbohydrate (CHO) depletion are the most likely causes of fatigue in triathlon, whereas gastrointestinal (GI) problems, hyperthermia and hyponatraemia are potentially health threatening, especially in longer events. Although glycogen supercompensation may be beneficial for triathlon performance (even Olympic distance), this does not necessarily have to be achieved by the traditional supercompensation protocol. More recently, studies have revealed ways to increase muscle glycogen concentrations to very high levels with minimal modifications in diet and training. During competition, cycling provides the best opportunity to ingest fluids. The optimum CHO concentration seems to be in the range of 5-8% and triathletes should aim to achieve a CHO intake of 60-70 g/hour. Triathletes should attempt to limit body mass losses to 1% of body mass. In all cases, a drink should contain sodium (30-50 mmol/L) for optimal absorption and prevention of hyponatraemia.Post-exercise rehydration is best achieved by consuming beverages that have a high sodium content (>60 mmol/L) in a volume equivalent to 150% of body mass loss. GI problems occur frequently, especially in long-distance triathlon. Problems seem related to the intake of highly concentrated carbohydrate solutions, or hyperosmotic drinks, and the intake of fibre, fat and protein. Endotoxaemia has been suggested as an explanation for some of the GI problems, but this has not been confirmed by recent research. Although mild endotoxaemia may occur after an Ironman-distance triathlon, this does not seem to be related to the incidence of GI problems. Hyponatraemia has occasionally been reported, especially among slow competitors in triathlons and probably arises due to loss of sodium in sweat coupled with very high intakes (8-10 L) of water or other low-sodium drinks.

Sweat rate and fluid turnover in American football players compared with runners in a hot and humid environment

OBJECTIVES

To determine sweat rate (SwR) and fluid requirements for American footballers practicing in a hot, humid environment compared with cross country runners in the same conditions.

METHODS

Fifteen subjects, 10 footballers and five runners, participated. On the 4th and 8th day of preseason two a day practices, SwR during exercise was determined in both morning and afternoon practices/runs from the change in body mass adjusted for fluids consumed and urine produced. Unpaired t tests were used to determine differences between groups.

RESULTS

Overall SwR measured in litres/h was higher in the footballers than the cross country runners (2.14 (0.53) v 1.77 (0.4); p<0.01). Total sweat loss in both morning (4.83 (1.2) v 1.56 (0.39) litres) and afternoon (4.8 (1.2) v 1.97 (0.28) litres) practices/runs, and daily sweat losses (9.4 (2.2) v 3.53 (0.54) litres) were higher in the footballers (p<0.0001). The footballers consumed larger volumes of fluid during both morning and afternoon practices/runs (23.9 (8.9) v 5.5 (3.1) ml/min and 23.5 (7.3) v 13.6 (5.6) ml/min; p<0.01). For complete hydration, the necessary daily fluid consumption calculated as 130% of daily sweat loss in the footballers was 12.2 (2.9) litres compared with 4.6 (0.7) litres in the runners (p<0.0001). Calculated 24 hour fluid requirements in the footballers ranged from 8.8 to 19 litres.

CONCLUSIONS

The American footballers had a high SwR with large total daily sweat losses. Consuming large volumes of hypotonic fluid may promote sodium dilution. Recommendations for fluid and electrolyte replacement must be carefully considered and monitored in footballers to promote safe hydration and avoid hyponatraemia.

Sodium Status of Collapsed Marathon Runners

Context.—Recommendations for prevention and treatment of medical emergencies in participants in marathon races center on maintenance of adequate hydration status and administration of fluids. Recently, new recommendations for fluid replacement for marathon runners were promulgated by medical and athletic societies. These new guidelines encourage runners to drink ad libitum between 400 and 800 mL/h as opposed to the previous “as much as possible” advice.

Objective.—To assess the sodium and hydration (plasma osmolality) status of collapsed marathon runners after the promulgation of new hydration guidelines.

Design.—Plasma sodium and osmolality values of runners who presented to the medical tent at the finish line of the 2003 Boston Marathon were measured.

Results.—Using reference ranges derived from the general population, of 140 collapsed runners, 35 (25%) were hypernatremic (sodium, &gt;146 mEq/L) and 6 (12%) were hyperosmolar (osmolality, &gt;296 mOsm/kg H2O), whereas 9 (6%) were hyponatremic (sodium, &lt;135 mEq/L) and 8 (16%) were hypo-osmolar (osmolality, &lt;280 mOsm/kg H2O). Compared with a population of marathon runners who had experienced no medical difficulties, 9% of the runners were hypernatremic, 5% were hyponatremic, 8% were hypo-osmolar, and none were hyperosmolar.

Conclusions.—Our findings indicate a significant incidence of hypernatremia with hyperosmolality and hyponatremia with hypo-osmolality among collapsed runners despite the new fluid intake recommendations, suggesting that either further educational measures are required or that the new guidelines are not entirely adequate to prevent abnormalities in fluid balance. Furthermore, the immediate medical management of hypernatremia and hyponatremia is different. Administration of fluids to severely hyponatremic patients may result in fatal cerebral edema. Our findings caution against institution of treatment until laboratory tests determine the patient's sodium status.

Recommendations for treatment of hyponatraemia at endurance events

This review focuses on possible pathophysiology of exercise-associated hyponatraemia and its implication on evaluation and treatment of collapsed athletes during endurance events. Rehydration guidelines and field care have traditionally been based on the belief that endurance events create a state of significant fluid deficit in athletes, which must be corrected by liberal hydration. Beliefs in the necessity of liberal hydration may have contributed to cases of hyponatraemia. Assumptions that fluid loss accounts for the entire weight loss during exercise and that fluid ingestion is the only source of water gain during exercise may lead to an overestimation of the degree of volume depletion and the amount of fluid needed for replacement. Increasing evidence suggests that hyponatraemic athletes are fluid overloaded; ingestion of large amount of hypotonic fluid in combination with inappropriate or inadequate physiological responses leads to excessive retention of free fluid. Risk factors include hot weather, female sex, slower finishing time, and possibly the use of nonsteroidal anti-inflammatory medications. Symptoms of hyponatraemia can be subtle and can mimic those of other exercise-related illnesses, thereby complicating its diagnosis and leading to possible inappropriate treatment. Most athletes who collapse at the finish line experience exercise-associated collapse, a benign and transient form of postural hypotension that can be treated simply by continued ambulation after finishing or elevation of legs while in a supine position for those who cannot walk. Care providers should consider the use of intravenous hydration with normal saline carefully since it is not needed by most collapsed athletes and may worsen the condition of patients with unsuspected hyponatraemia. Historic information and clinical signs of volume depletion should be elicited prior to its use. Most hyponatraemic athletes will recover uneventfully with careful observation while awaiting spontaneous diuresis. Use of hypertonic saline should be reserved for patients with severe symptoms. Moderate consumption of carbohydrate-electrolyte solution during exercise may allow the maintenance of adequate hydration and the prevention of hyponatraemia.

[Changes in serum Na+ and blood hemoglobin levels during three types of transurethral procedures for the treatment of benign prostatic hypertrophy]

BACKGROUND

Transurethral holmium YAG laser resection of the prostate (HoLR-P) and transurethral electrovaporization of the prostate (TUV-P) have recently received increasing attention as an effective minimally invasive approach for the treatment of prostatic hypertrophy. However, less information is available regarding the intraoperative changes in the serum Na+ and blood hemoglobin levels during either HoLR-P or TUV-P.

METHODS

Intraoperative changes in serum Na+ and blood hemoglobin levels were investigated in 17 patients undergoing transurethral resection of the prostate (TUR-P, n = 7), HoLR-P (n = 7) or TUV-P (n = 3). The 3% D-sorbitol solution was used as the irrigating fluid in all the patients.

RESULTS

In three patients, severe hyponatremia (118-123 mEq x l(-1)) developed abruptly (< or = 15 min) at various time points during TUR-P with (n = 1) or without (n = 2) cystostomy. However, no clinical symptoms were observed after development of the hyponatremia in those awake patients. No large (> 10 mEq x l(-1)) decreases in the Na+ level were observed in any of the patients undergoing HoLR-P or TUV-P. In patients undergoing TUR-P and HoLR-P, percent changes in serum Na+ level significantly correlated with those in blood hemoglobin level, but not with the resection time; the slopes were significantly larger than unity.

CONCLUSIONS

The TUR syndrome is less likely to occur during HoLR-P or TUV-P. During TUR-P, the onset of severe hyponatremia appears to be unpredictable, and may not necessarily be accompanied by clinical symptoms. Frequent measurements of the serum Na+ level appear essential for early detection of severe hyponatremia.

Acute hyponatremia related to intravenous fluid administration in hospitalized children: an observational study

OBJECTIVE

To develop hyponatremia (plasma sodium concentration [P(Na)] <136 mmol/L), one needs a source of water input and antidiuretic hormone secretion release to diminish its excretion. The administration of hypotonic maintenance fluids is common practice in hospitalized children. The objective of this study was to identify risk factors for the development of hospital-acquired, acute hyponatremia in a tertiary care hospital using a retrospective analysis.

METHODS

All children who presented to the emergency department in a 3-month period and had at least 1 P(Na) measured (n = 1586) were evaluated. Those who were admitted were followed for the next 48 hours to identify patients with hospital-acquired hyponatremia. An age- and gender-matched case-control (1:3) analysis was performed with patients who did not become hyponatremic.

RESULTS

Hyponatremia (P(Na) <136 mmol/L) was documented in 131 of 1586 patients with > or = 1 P(Na) measurements. Although 96 patients were hyponatremic on presentation, our study group consisted of 40 patients who developed hyponatremia in hospital. The case-control study showed that the patients in the hospital-acquired hyponatremia group received significantly more EFW and had a higher positive water balance. With respect to outcomes, 2 patients had major neurologic sequelae and 1 died.

CONCLUSION

The most important factor for hospital-acquired hyponatremia is the administration of hypotonic fluid. We suggest that hypotonic fluid not be given to children when they have a P(Na) <138 mmol/L.

Iatrogenic prescribing in acute care: learning from our mistakes

1. The pharmacokinetics of medications (i.e., absorption, distribution, metabolism, elimination) are altered in older adults because of age-related changes in body composition, diminished vascularity, and atrophy of end-organs. 2. The result of altered pharmacokinetics is often a stronger drug effect than seen in younger adults, a longer duration of drug action, and higher risk of adverse drug effects and drug-drug interactions. 3. Nurses working with older adults should be aware of measures to prevent potential adverse drug effects, including being aware of adverse effects of drugs and that the effects of drugs in older adults are atypical; being aware that changing more than one medication or dosage at a time may make interpretation of the response more difficult; being aware that many drugs with narrow therapeutic windows can and should be monitored via serum levels, and that renal insufficiency will increase the chance of adverse drug effects for renally excreted drugs.

Hyponatremia and the nursing implications

Serum sodium concentration plays a major role in the body's volume status. Low serum sodium levels can be dangerous and even fatal if hyponatremia is severe. The key to understanding hyponatremia is relating it to volume status. Hyponatremia is frequently associated with hypovolemia or fluid overload. Sharp assessment skills and client teaching can prove invaluable in the prevention and treatment of hyponatremia.

Gender differences of sodium metabolism and hyponatremia as an adverse drug effect

Gender-related differences in sodium (Na+) metabolism, Na+ transport through cell membrane, intracellular Na+ concentration, and Na+ urinary excretion review is presented in the article. Literature data on gender-related differences in the occurrence of hyponatremia and related neurology are overviewed. Some of the drugs used in neurology (carbamazepine, oxcarbazepine, thiazides, antidepressants) are pointed out as eventual sources of hyponatremia. This disorder shows a clear-cut preference of the feminine gender. The authors present literature data on gender-related differences in the mechanisms of Na+ transport (Na+/H+ exchange, Na+/K+/2Cl- cotransport, Na+, K+-ATPase). The reasons for such differences are not yet known. Investigative tests with animals of both genders, cellular studies and clinical investigations with human males and females could help to answer question why females are more prone to hyponatremia, to select more efficient measures for prevention of hyponatremia and to differentiate specific peculiarities of treatment for patients of either sex.