Rapid fluid administration is the single most important initial step in the treatment of DKA. 3 Fluid helps restore intravascular volume and normal tonicity, perfuse vital organs, improve glomerular filtration rate (GFR), and lower serum glucose and ketones. The average adult patient has a water deficit of 100 mL/kg (5 to 10 L) and a sodium deficit of 7 to 10 meq/kg.3 NS is the most frequently recommended fluid for initial rehydration even though the extracellular fluid of the patient is initially hypertonic. NS does not provide "free water" to correct intracellular dehydration, but it does prevent an excessively rapid fall in extracellular osmolarity and excessive transfer of water into the central nervous system (CNS). After initial resuscitation with NS, most authors favor alternating the administration of NS with half-normal saline, or utilizing two intravenous lines—one NS and one-half NS.
Based on clinical suspicion alone and prior to initial electrolyte results, the first liter of NS should be administered well within the first 30 min unless there are mitigating circumstances. In general, the first 2 L are administered rapidly over 0 to 2 h, the next 2 L over 2 to 6 h, and 2 L more over 6 to 12 h. This replaces approximately 50 percent of the total water deficit over the first 12 h, with the remaining 50 percent water deficit to be replaced over the subsequent 12 h. The blood glucose and ketone body concentration begin to fall after fluid administration and before implementation of any other therapeutic modality. 13 Hydration alone will reduce the glucose concentration by 17 to 80 percent over 12 to 14 h.14 Tissue perfusion is restored with rehydration, improving the effectiveness of insulin. The subsequent rise in GFR allows for glucose and ketone body clearance, lowering serum glucose concentration and osmolarity. The patient's blood glucose needs to be carefully monitored, and 5% dextrose added to the rehydration solution when the glucose is 250 to 300 mg/dL.
The fluid should be changed to a hypotonic solution after the initial replacement of intravascular volume with normal saline. Patients presenting without extreme volume depletion can be safely managed with a modest fluid replacement regimen (500 cc/h for 4 h).15 Monitoring central venous pressure or pulmonary artery wedge pressure should be considered during fluid replacement in elderly patients or in those with heart disease. Although the most common pitfall is failure to give adequate volume replacement,3 excess fluid may contribute to the development of adult respiratory distress syndrome and cerebral edema.
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