Fluids, Electrolytes, Acid-Base Disorders, and Nutrition Support

Summary: The data are confusing because several studies have used different times for the definition

of early nutrition therapy: 24, 36, 48, and 72 hours. Most evidence-based clinicians would suggest that

enteral nutrition therapy be initiated for most patients within 48 hours of ICU admission and no later

than 72 hours. Surgical ICU patients, including those with trauma and thermal injury, have been more

consistently shown to benefit from early EN as opposed to medical ICU patients, for whom results are

more variable.

Glycemic Control

Definition of the appropriate BG target range

trigger initiation of insulin therapy to keep BG less than 150 mg/dL for most patients and maintain

BG absolutely less than 180 mg/dL.

ASPEN guidelines (2013) (JPEN J Parenter Enteral Nutr 2013;37:23-36): A target BG range of

140–180 mg/dL is recommended.

protocol to keep BG less than 180 mg/dL, rather than an upper target of 110 mg/dL, is recommended

when the patient has two consecutive BG measurements greater than 180 mg/dL.

infusion should be used to control hyperglycemia, starting with a threshold of greater than or equal

to 180 mg/dL. BG should be maintained between 140 and 180 mg/dL for most critically ill patients.

More stringent goals such as 110–140 mg/dL or 100–180 mg/dL may be more appropriate for

selected critically ill patients, as long as this can be accomplished without significant hypoglycemia.

to manage persistent hyperglycemia, defined as BG greater than 180 mg/dL. Continuous infusions

are preferred to subcutaneous insulin, especially in acute illness. The goal BG should be greater

than 140 mg/dL, rather than more stringent targets of 80 to 139 mg/dL, while receiving an insulin

infusion. Frequency of BG monitoring should be no less than every 1 hour while the patient is

receiving intravenous insulin.

Summary: Many evidence-based clinicians use a target BG range of 140–180 mg/dL when caring

for patients in a mixed medical-surgical ICU. A growing amount of evidence from smaller studies

shows that certain subpopulations such as trauma, traumatic brain injury, cardiothoracic surgery,

and thermal injury may benefit from tighter BG (e.g., less than 140–150 mg/dL) control if it can be

hours for most patients receiving an insulin infusion; monitoring every 4 hours is not recommended

because of the risk of unrecognized hypoglycemia.

monitored every 1–2 hours during the insulin infusion and then extended to every 4 hours thereafter

once stability in BG control is achieved.

American Diabetes Association (2023) (Diabetes Care 2023;46(suppl 1):S267-78): BG should be

monitored every ½–2 hours during the insulin infusion.

Hypoglycemia

Most guidelines define hypoglycemia as a BG less than 70 mg/dL because increased glucagon,

catecholamine, and growth hormone production occurs when the BG falls below this concentration.

Mild to moderate hypoglycemia is usually defined as a BG concentration of 40–60 mg/dL (because

autonomic symptoms often appear) and severe (life-threatening) hypoglycemia as less than 40

mg/dL.