SU12.1-3 | Nutrition, Fluids and Electrolytes — Glossary

Isotonic crystalloid (Na 154, Cl 154 mmol/L) with no potassium or buffer; large volumes cause hyperchloraemic metabolic acidosis.

Crystalloid providing essentially free water once glucose is metabolised, with negligible electrolytes; not a resuscitation fluid.

Physical measurement of the body (weight, BMI, MUAC, skinfold thickness) to quantify nutritional stores and trend.

Passage of gut bacteria or their products across an atrophied, disused intestinal mucosa into the body, a source of systemic sepsis.

Weight (kg) divided by height squared (m²); <18.5 = underweight, <16 = severe undernutrition.

Sepsis arising from a central venous catheter, the most feared complication of total parenteral nutrition.

The volume a patient is already short of before therapy begins, estimated clinically from dehydration.

Feeding via the gastrointestinal tract (oral, nasogastric, nasojejunal, gastrostomy/PEG or jejunostomy), preferred whenever the gut works.

An abnormal communication between the gut and the skin that drains nutrient-rich fluid and bypasses absorptive surface, causing losses and malnutrition.

Fluid outside cells (interstitial + intravascular), about one-third of total body water; sodium is its principal cation.

A feeding tube placed directly into the stomach (often percutaneous endoscopic) for longer-term enteral feeding.

A maintenance fluid formula: 4 mL/kg/h for the first 10 kg, 2 mL/kg/h for the next 10 kg, 1 mL/kg/h for each kg above 20.

Acidosis from a high chloride load, classically caused by large-volume 0.9% saline infusion.

Fluid within cells, holding about two-thirds of total body water; potassium is its principal cation.

Predominantly protein deficiency causing hypoalbuminaemia and oedema, so the patient may look deceptively well-covered despite depletion.

The fluid and electrolytes needed to replace normal obligatory daily losses (urine, stool, sweat, insensible loss).

A state in which deficiency, excess or imbalance of energy, protein or other nutrients causes measurable adverse effects on body composition, function and clinical outcome.

A five-step admission screening tool scoring nutritional risk as 0 (low), 1 (medium) or ≥2 (high).

Mixed severe malnutrition with established wasting plus superimposed hypoalbuminaemia and oedema — common in sick surgical patients.

Chronic balanced deficiency of energy and protein causing severe wasting of fat and muscle, typically with a preserved serum albumin.

An anthropometric measure of muscle and fat stores used in nutritional assessment.

A plasma protein (e.g. albumin, prealbumin) whose level FALLS during inflammation, so it reflects illness severity more than nutritional intake.

State in which nitrogen (protein) loss exceeds intake, reflecting net catabolic breakdown of body protein.

Continuing abnormal fluid losses (nasogastric aspirate, fistula, stoma, drains, diarrhoea, third space) that must be measured and replaced.

Intravenous delivery of nutrients (peripheral PN or central total parenteral nutrition) when the gut cannot be used.

A plasma transport protein with a short half-life (~2 days) used as a more responsive but still inflammation-confounded nutritional marker.

Malnutrition due to inadequate energy and protein intake or utilisation, spanning marasmus, kwashiorkor and mixed forms.

Potentially fatal electrolyte and metabolic shift on re-feeding a chronically starved patient — hypophosphataemia (hallmark), hypokalaemia, hypomagnesaemia and thiamine deficiency, driven by an insulin surge.

A balanced crystalloid close to plasma composition (Na ~131, Cl ~111, K ~5, Ca ~2 mmol/L, lactate buffer), preferred for resuscitation and routine replacement.

Disease- or age-related loss of skeletal muscle mass and function, a strong predictor of poor surgical outcome.

Malabsorption resulting from loss of a critical length of small intestine after extensive resection.

A validated bedside tool grading nutritional status A (well-nourished), B (moderate/suspected) or C (severe) from history and examination; predicts outcome better than single biochemical markers.

Sequestration of extracellular fluid into inflamed/traumatised tissue or the gut lumen, lost to the circulation though still within the body.

The total volume of water in the body, approximately 60% of body weight in an adult.

Complete nutrition delivered intravenously via a central line for a non-functioning, inaccessible or inadequate gut.

Deficiency of energy and/or protein and micronutrients — the form of malnutrition usually meant in surgical practice.