| Weight conversion |
Weight kg = weight g ÷ 1000 |
Use grams for birth weight and current weight; convert to kg before calculations |
Almost all NICU dosing, fluids, calories, urine output, GIR, and ventilator volumes should be normalized to kg so that tiny weight differences in VLBW and ELBW infants are handled safely. |
Pitfall: mixing grams and kilograms in dosage equations. Always double-check units, especially for small VLBW infants where a 1000x error is lethal. |
| Total daily fluid intake |
mL/kg/day = total fluid mL/day ÷ weight kg |
Fluids in mL/day; weight in kg |
This calculates total fluid exposure from IV fluids, TPN, lipids, feeds, flushes, and medication carriers, which is essential for assessing dehydration, fluid overload, sodium balance, PDA physiology, renal status, and weight change. |
RCH advises using birth weight as the working weight if the neonate is still below birth weight, unless the medical team specifies otherwise. Do not forget to count medication infusion volumes and replacement fluids, because “hidden” fluid often explains unexpected weight gain or hyponatremia. |
| Hourly IV rate from daily fluid goal |
mL/hr = target mL/kg/day × weight kg ÷ 24 |
Target in mL/kg/day; weight in kg; result in mL/hr |
This converts a daily NICU fluid prescription into the pump rate that nurses can administer each hour. |
Round cautiously in very small infants; even 0.1–0.2 mL/hr matters. Recalculate whenever feeds are advanced, infusions are added, phototherapy increases insensible loss, or replacement volumes change. |
| Net fluid balance |
Net balance mL/kg/day = total intake mL/kg/day − total output mL/kg/day |
Intake and output both in mL/kg/day |
This helps teach whether the baby is retaining or losing fluid after accounting for urine, drains, stool estimates if used, and other measurable losses. |
Insensible loss is often the missing part of the picture, especially in extremely preterm infants, under phototherapy, with radiant warmers, or in dry environmental conditions. Repeated weights are among the most useful objective checks. |
| Urine output |
Urine output mL/kg/hr = urine volume mL ÷ weight kg ÷ hours collected |
Urine in mL; weight in kg; time in hours |
This is one of the most important NICU bedside formulas because low urine output can reflect poor renal perfusion, AKI, dehydration, obstruction, or hemodynamic compromise. |
Interpret trends, not isolated numbers. Diuretics, glucosuria, post-obstructive diuresis, caffeine, and prematurity can all change urine output meaningfully. Bag weights and diaper subtraction errors are common. |
| Glucose infusion rate from IV rate |
GIR mg/kg/min = dextrose % × IV rate mL/hr × 0.167 ÷ weight kg |
Dextrose as percent, IV rate in mL/hr, weight in kg |
GIR describes the exact glucose delivery rate, and common starting values are about 4–6 mg/kg/min for term infants and 6–8 mg/kg/min for premature infants, with titration based on glucose and clinical status. |
Common errors: entering FiO2-style percentages incorrectly, forgetting current weight, ignoring glucose from other infusions, or mixing mL/hr with mL/kg/day. Hyperglycemia management should not start with insulin before confirming that GIR is not excessive and that sepsis, stress, medications, or iatrogenic calculation error are not the cause. |
| Glucose infusion rate from daily fluid volume |
GIR mg/kg/min = mL/kg/day × dextrose % ÷ 144 |
Fluid in mL/kg/day; dextrose as percent |
This is the fastest educational bedside version when the IV fluid is already written as mL/kg/day instead of mL/hr. |
Verify with institutional NICU protocol, patient condition, gestational age, and clinical guidelines. |
| Calories from enteral feeds |
kcal/kg/day = feed volume mL/kg/day × kcal/oz ÷ 29.57 |
Feed volume in mL/kg/day; milk concentration in kcal/oz |
This converts human milk, fortified milk, or formula concentration into daily energy intake, and AAP notes that preterm infants often require calorically dense nutrition because unfortified human milk alone is usually insufficient for VLBW growth. |
Never interpret volume as nutrition without composition. A 150 mL/kg/day feed plan is not the same nutritional plan across products. Fortification changes energy, protein, minerals, and osmolality simultaneously. |
| Daily feed volume needed for calorie target |
mL/kg/day = target kcal/kg/day × 29.57 ÷ kcal/oz |
Target in kcal/kg/day; concentration in kcal/oz |
This helps estimate how much feed volume is needed to achieve an energy goal, but the final plan must consider feeding tolerance, respiratory status, NEC risk, fortification strategy, and fluid restriction. |
Preterm growth targets are 15-20 g/kg/day; feeding advancement must be customized based on feeding tolerance, abdominal exams, and risk for necrotizing enterocolitis (NEC). |
| Volume per feed |
mL/feed = total daily feed volume mL/day ÷ number of feeds/day |
Daily volume in mL/day; number of feeds per day |
This changes the daily feeding plan into practical q2h, q3h, q4h, bolus, or pump-feed volumes. |
Very small volumes may require syringe accuracy, dead-space awareness, and checking whether bolus versus continuous feeding is intended. If the infant is on mixed feed + TPN support, the feed advance should automatically recalculate the TPN rate downward to preserve TFI. |
| Protein intake from feeds |
Protein g/kg/day = protein g/100 mL × feed volume mL/day ÷ 100 ÷ weight kg |
Protein in g/100 mL; volume in mL/day; weight in kg |
This is important because protein delivery strongly affects lean growth, and many preterm nutrition references target roughly 3.5–4.5 g/kg/day depending on birth weight and clinical condition. |
Low BUN can suggest inadequate protein intake, but BUN must be interpreted with hydration, energy intake, renal function, and tolerance. Overly simple “high protein is always better” messaging is misleading; protein-energy balance matters. |
| Any nutrient intake from milk, formula, fortifier, or TPN |
Nutrient/kg/day = nutrient amount per 100 mL × total mL/day ÷ 100 ÷ weight kg |
Nutrient can be mg, mEq, mmol, IU, or g per 100 mL |
This universal formula can calculate calcium, phosphorus, sodium, potassium, iron, vitamin D, zinc, fat, carbohydrate, and protein exposure from labels or TPN components. |
Verify if values on labels are per 100 mL or per 100 kcal. Fortification changes osmolality and renal solute load. |
| Sodium deficit |
Na deficit mEq = (desired Na − current Na) × 0.6 × weight kg |
Sodium in mEq/L; weight in kg; result in mEq |
The factor 0.6 L/kg estimates the sodium distribution space, but correction speed must be individualized because rapid sodium correction can be dangerous. |
Correct sodium slowly and use disease-specific guidance for acute symptomatic hyponatremia or hypernatremia. A “deficit” formula does not replace monitoring of glucose, tonicity, urine output, and ongoing losses. |
| Daily sodium intake |
Na mEq/kg/day = total Na mEq/day ÷ weight kg |
Sodium in mEq/day; weight in kg |
This helps account for sodium from TPN, IV fluids, medications, saline flushes, arterial line fluids, enteral supplements, and feeds. |
Verify with institutional NICU protocol, patient condition, gestational age, and clinical guidelines. |
| Daily potassium intake |
K mEq/kg/day = total K mEq/day ÷ weight kg |
Potassium in mEq/day; weight in kg |
This is useful during renal immaturity, AKI, diuretic therapy, amphotericin exposure, insulin therapy, refeeding, or TPN adjustment. |
Verify with institutional NICU protocol, patient condition, gestational age, and clinical guidelines. |
| Anion gap |
AG = Na − (Cl + HCO₃) |
Na, Cl, and HCO₃ in mEq/L |
This helps classify metabolic acidosis and teaches whether acidosis is mainly due to unmeasured anions or bicarbonate loss. |
Always check whether your lab includes potassium. Always interpret AG with albumin, lactate, ketones, perfusion status, and blood gas data. In NICU practice, low albumin can mask an elevated gap. |
| Albumin-corrected anion gap |
Corrected AG = measured AG + 2.5 × (4.0 − albumin g/dL) |
Albumin in g/dL |
Low albumin can hide an elevated anion gap, so this correction is useful when interpreting metabolic acidosis in hypoalbuminemic infants. |
Use this to improve interpretation, not to replace clinical assessment. Lactate, ketones, renal failure, and toxic exposures still require direct evaluation. |
| Calculated plasma osmolality |
Osmolality mOsm/kg = 2 × Na + glucose/18 + BUN/2.8 |
Na in mEq/L; glucose and BUN in mg/dL |
This estimates serum osmolality during hypernatremia, dehydration, renal dysfunction, hyperglycemia, or evaluation of an osmolar gap. |
Do not confuse osmolality with tonicity. In hyperglycemia, tonicity is often more clinically informative for water shifts. If a measured osmolality is available, comparing measured and calculated values can suggest an osmolar gap. |
| Percent weight loss |
% weight loss = (birth weight − current weight) ÷ birth weight × 100 |
Use the same unit for both weights, usually grams |
This quantifies early postnatal weight loss and helps distinguish expected physiologic contraction from excessive fluid loss or inadequate intake. |
Expected physiologic weight loss in the first 3-5 days is up to 10% for term and 15% for preterm infants due to contraction of extracellular water. Red flag: loss exceeding 3% per day or failure to regain birth weight by 10-14 days. |
| Simple daily weight gain |
g/day = (current weight g − previous weight g) ÷ days between weights |
Weight in grams; time in days |
This is easy for parents and trainees to understand, but it is less accurate than g/kg/day when comparing infants of different sizes. |
Weight gain fluctuates daily due to fluid shifts. Look at 3-day and 7-day rolling averages for true nutritional progress. |
| Exponential growth velocity |
g/kg/day = 1000 × ln(current weight ÷ previous weight) ÷ days |
Both weights in grams; time in days |
This is a better growth-velocity method for preterm infants because it accounts for proportional growth rather than using only absolute grams per day. |
Do not interpret weight velocity during the expected early postnatal diuresis as “nutrition failure.” Timing matters. Growth is best interpreted with head circumference and length, not weight alone. |
| Ponderal index |
PI = weight g × 100 ÷ length cm³ |
Weight in grams; length in cm |
This describes proportionality and may help teach symmetric versus asymmetric growth restriction. |
Birth length measurement error is common and can distort PI substantially because length is cubed. Interpret with fetal growth charts and antenatal history, not in isolation. |
| Postmenstrual age |
PMA weeks = gestational age at birth weeks + chronological age weeks |
Use weeks and days consistently |
PMA is essential for NICU education because apnea maturity, feeding readiness, ROP screening timing, thermoregulation, discharge planning, and developmental expectations depend on maturity. |
Essential for determining the onset of ROP screening (typically 31 weeks PMA or 4 weeks postnatal age, whichever is later), feeding readiness, and apnea of prematurity resolution. |
| Corrected age |
Corrected age = chronological age − (40 weeks − gestational age at birth) |
Use weeks or months consistently |
Corrected age adjusts developmental and growth interpretation for prematurity after discharge. |
Be consistent on the website about whether “full term” is defined by 39 weeks for parental counseling or 40 weeks for arithmetic correction; if you use 40 in the calculator, explain it explicitly. |
| Alveolar gas equation |
PAO₂ = FiO₂ × (Pb − PH₂O) − PaCO₂/R |
FiO₂ as decimal; Pb, PH₂O, PaCO₂ in mmHg; R usually 0.8 |
This estimates alveolar oxygen tension and teaches why hypoxemia depends on inspired oxygen, barometric pressure, water vapor pressure, CO₂, and gas exchange. |
Common mistakes are using FiO2 as a percent rather than a decimal, omitting water-vapor pressure, or ignoring altitude. If the website serves international users, show a note that kPa users need consistent units. |
| A–a oxygen gradient |
A–a gradient = PAO₂ − PaO₂ |
PAO₂ and PaO₂ in mmHg |
This separates low alveolar oxygen from impaired transfer of oxygen from alveoli to arterial blood. |
Interpretation depends on FiO2, altitude, and blood-gas reliability. Very high FiO2 changes the meaning of the number, so trend plots are often more informative than single cutoffs. |
| Minute ventilation |
VE = tidal volume × respiratory rate |
Tidal volume in mL; RR in breaths/min |
This calculates the total gas moved each minute, but it does not subtract dead space. |
High V̇E does not guarantee good CO2 clearance if VT is very small or dead space is large. Always integrate blood gases or transcutaneous CO2. |
| Alveolar ventilation |
VA = (tidal volume − dead space) × respiratory rate |
Volumes in mL; RR in breaths/min |
This estimates the gas that actually reaches functioning alveoli and participates in CO₂ removal. |
An infant can have a “normal” minute ventilation but inadequate alveolar ventilation if dead space is large. This is a strong candidate for a website flowchart or animated diagram. |
| Physiologic dead space, Bohr equation |
VD/VT = (PaCO₂ − PeCO₂) ÷ PaCO₂ |
PaCO₂ and PeCO₂ in the same unit, usually mmHg |
This teaches the fraction of each breath that does not eliminate CO₂ effectively. |
Be explicit on the website whether you are using the classic Bohr form or the Enghoff modification with PaCO2. Mixed expired CO2 is not routinely available in every NICU. |
| Compliance |
Compliance = change in volume ÷ change in pressure |
Volume in mL; pressure in cmH₂O; optional normalization as mL/kg/cmH₂O |
Low compliance means a stiff lung or respiratory system, as seen with RDS, atelectasis, edema, pulmonary hypoplasia, or abdominal restriction. |
Specify whether the website means lung compliance, chest-wall compliance, or total respiratory-system compliance. Neonates have especially compliant chest walls, so isolated numbers may mislead if the concept is not defined. search2turn17search1 |
| Elastance |
Elastance = change in pressure ÷ change in volume |
Pressure in cmH₂O; volume in mL |
Elastance is the inverse of compliance, so higher elastance means the lung is harder to inflate. |
Do not display compliance and elastance as independent phenomena; they are reciprocals. The website will be clearer if the two rows cross-link. |
| Airway resistance |
Resistance = change in pressure ÷ flow |
Pressure in cmH₂O; flow in L/sec |
High resistance suggests ETT obstruction, secretions, bronchospasm, airway edema, small ETT size, or circuit problems. |
State flow units clearly because resistance units change if you use L/sec versus L/min. In neonates, ETT size itself can dominate measured/observed resistance. |
| Time constant |
Time constant = resistance × compliance |
Use compatible respiratory mechanics units |
This explains how quickly the lung fills and empties, which matters when adjusting inspiratory time, expiratory time, rate, and avoiding air trapping. |
High resistance or high compliance lengthens τ. This row is ideal for a small ventilator diagram because it explains why long expiratory times matter in obstructive physiology and why stiff RDS lungs behave differently. |
| Mean airway pressure on conventional ventilation |
MAP ≈ [(PIP − PEEP) × Ti ÷ (Ti + Te)] + PEEP |
PIP and PEEP in cmH₂O; Ti and Te in seconds |
MAP reflects average distending pressure and is strongly related to oxygenation, lung recruitment, and barotrauma risk. |
This equation is mode-dependent and simplified. HFOV, flow-cycled modes, and spontaneous effort complicate the relationship. Higher MAP may improve oxygenation but can also worsen venous return or overdistend fragile lungs. search0turn17search1 |
| Tidal volume per kg |
VT mL/kg = exhaled VT mL ÷ weight kg |
Exhaled VT in mL; weight in kg |
This is important for volume-targeted ventilation because excessive tidal volume increases volutrauma risk in preterm lungs. |
Target tidal volume in volume-guaranteed ventilation is typically 4–6 mL/kg for RDS and 5–7 mL/kg for BPD. Excessive tidal volume increases volutrauma risk in preterm lungs. |
| Oxygenation index |
OI = MAP × FiO₂ × 100 ÷ PaO₂ |
MAP in cmH₂O; FiO₂ as decimal; PaO₂ in mmHg |
OI combines oxygen requirement, ventilator pressure, and arterial oxygenation, and neonatal HRF is often classified as mild, moderate, severe, or very severe by OI range. |
Interpret OI as a trend and in conjunction with shunt physiology, radiology, hemodynamics, and pulmonary hypertension assessment. The denominator requires an arterial sample; if none is available, OSI may be a practical adjunct. search0 |
| Oxygen saturation index |
OSI = MAP × FiO₂ × 100 ÷ SpO₂ |
MAP in cmH₂O; FiO₂ as decimal; SpO₂ as percent |
OSI is a noninvasive surrogate for OI when arterial PaO₂ is unavailable, although it is less reliable when SpO₂ is near the flat upper part of the oxyhemoglobin curve. |
OSI is less robust when saturation is near the flat upper part of the oxyhemoglobin curve or when perfusion is poor. It is a surrogate, not a replacement for arterial gas analysis. search1 |
| PaO₂/FiO₂ ratio |
P/F ratio = PaO₂ ÷ FiO₂ |
PaO₂ in mmHg; FiO₂ as decimal |
This measures how much arterial oxygen tension is achieved for the amount of oxygen delivered, with lower values indicating worse oxygen transfer. |
Verify with institutional NICU protocol, patient condition, gestational age, and clinical guidelines. |
| SpO₂/FiO₂ ratio |
S/F ratio = SpO₂ ÷ FiO₂ |
SpO₂ as percent; FiO₂ as decimal |
This provides a noninvasive oxygenation estimate when an arterial blood gas is not available. |
Verify with institutional NICU protocol, patient condition, gestational age, and clinical guidelines. |
| Arterial oxygen content |
CaO₂ = 1.34 × Hb × SaO₂ + 0.003 × PaO₂ |
Hb in g/dL; SaO₂ as decimal; PaO₂ in mmHg |
This teaches that most blood oxygen content comes from hemoglobin-bound oxygen rather than dissolved oxygen. |
Use measured co-oximetry saturation when available. SpO2 can mislead in poor perfusion, dyshemoglobinemia, or motion artifact. search1 |
| Oxygen delivery |
DO₂ = cardiac output × CaO₂ |
CO in L/min or mL/kg/min; CaO₂ in compatible oxygen-content units |
This explains why oxygen delivery depends on cardiac output, hemoglobin, saturation, and PaO₂ together. |
This is a conceptual/teaching formula more often than a routine bedside NICU calculation. Avoid implying that a single ḊO2 number can by itself define perfusion adequacy in neonates. |
| Oxygen consumption, Fick principle |
VO₂ = CO × (arterial O₂ content − venous O₂ content) |
CO and oxygen content must use compatible units |
This teaches tissue oxygen extraction and helps explain shock, anemia, sepsis, PPHN, and low cardiac output physiology. |
Verify with institutional NICU protocol, patient condition, gestational age, and clinical guidelines. |
| Cardiac output |
CO = heart rate × stroke volume |
HR in beats/min; SV in mL/beat |
Neonates are highly heart-rate dependent because their ability to increase stroke volume is limited compared with older patients. |
Stroke volume is not easily measured at the bedside without echo or advanced monitoring. Use this mainly as a conceptual calculator unless measurement inputs are actually available. |
| Cerebral perfusion pressure |
CPP = MAP − intracranial pressure |
MAP and ICP in mmHg |
This explains why hypotension or elevated intracranial pressure can reduce cerebral blood flow. |
ICP is seldom measured directly in routine NICU care. Avoid implying false numeric precision; the main value for the website is conceptual understanding. |
| Cerebral blood flow concept |
CBF = cerebral perfusion pressure ÷ cerebral vascular resistance |
CPP in mmHg; resistance in compatible vascular-resistance units |
This is a physiology teaching formula showing that cerebral blood flow depends on perfusion pressure and vascular tone. |
In neonates, CBF is rarely measured directly in bedside units and autoregulation may be impaired, especially in very preterm infants. Treat this as a conceptual physiology identity. |
| Systemic vascular resistance |
SVR = (mean aortic pressure − mean right atrial pressure) ÷ systemic blood flow |
Pressure in mmHg; flow in L/min or mL/kg/min |
SVR explains afterload and systemic circulation changes after birth. |
Low CO makes calculated resistance unstable and misleading. If you present this on the website, also show Wood units and explain the conversion. |
| Pulmonary vascular resistance |
PVR = (mean pulmonary artery pressure − mean left atrial pressure) ÷ pulmonary blood flow |
Pressure in mmHg; flow in compatible units |
PVR is central to understanding normal transition, PPHN, right-to-left shunting, oxygen response, ventilation strategy, and pulmonary vasodilator therapy. |
Do not confuse pulmonary vascular resistance with pulmonary artery pressure; they are related but not identical. Echo, shunt direction, septal position, and oxygenation response all matter clinically. search7 |
| Qp/Qs ratio |
Qp/Qs = pulmonary blood flow ÷ systemic blood flow |
Unitless ratio |
Qp/Qs above 1 suggests net left-to-right shunting, while Qp/Qs below 1 suggests net right-to-left shunting. |
The saturation version assumes several things, including reliable pulmonary venous saturation. Spell that out. In real neonatal cardiology work, echocardiography and full hemodynamic context matter more than a stand-alone number. |
| Intrapulmonary shunt fraction |
Qs/Qt = (CcO₂ − CaO₂) ÷ (CcO₂ − CvO₂) |
Oxygen contents in same units |
This estimates the fraction of blood that passes through the lung without being fully oxygenated. |
Requires assumptions and measurements that are often not fully available in everyday NICU practice. Make sure the website explains that this is a physiology formula, not a standard casual bedside monitor value. |
| Fractional excretion of sodium |
FENa % = 100 × urine Na × plasma Cr ÷ (plasma Na × urine Cr) |
Na in mEq/L; creatinine values in the same concentration unit |
FENa may support AKI evaluation, but neonatal interpretation is limited by gestational age, renal immaturity, diuretics, sodium administration, and changing creatinine after birth. |
Do not apply adult cutoffs rigidly in preterm infants or after diuretics. Use alongside urine output, creatinine trend, gestation, day of life, and overall fluid/electrolyte context. |
| Neonatal estimated GFR |
eGFR = 0.31 × height cm ÷ serum creatinine mg/dL |
Height in cm; serum creatinine in mg/dL; result in mL/min/1.73 m² |
NIDDK describes this neonatal eGFR equation for term-born infants up to 4 weeks of age and emphasizes that eGFR is an estimate best interpreted by trend. |
Do not apply this equation indiscriminately to preterm infants or older infants. Neonatal creatinine early after birth is strongly influenced by maternal creatinine and rapidly changing physiology. |
| Renal clearance |
Clearance = urine concentration × urine flow rate ÷ plasma concentration |
Urine and plasma concentration in same unit; urine flow in mL/min |
This is the basic renal formula for how much plasma is cleared of a solute per unit time. |
In neonates, timed urine collections are difficult and inaccurate collections can make results misleading. For bedside clinical use, trend-based interpretation usually outperforms a one-off “exact” number. |
| Weight-based medication dose |
Dose mg = ordered mg/kg/dose × weight kg |
Ordered dose in mg/kg/dose; weight in kg |
This is the basic NICU medication dose calculation, but neonatal dosing must also account for gestational age, postnatal age, postmenstrual age, renal function, hepatic function, drug level monitoring, and maximum dose. |
Always cross-reference with neonatal-specific drug registries (e.g., Neofax or Lexicomp) because renal and hepatic clearance change rapidly during the first week of life. |
| Continuous medication infusion rate |
mL/hr = dose mcg/kg/min × weight kg × 60 ÷ concentration mcg/mL |
Dose in mcg/kg/min; weight in kg; concentration in mcg/mL |
This converts vasoactive, sedative, insulin, prostaglandin, or other continuous infusion dosing into a pump rate. |
Double-check 'smart pump' concentration settings. Vasoactive infusions should be administered through a dedicated line to avoid accidental boluses during flushes. |
| Loading dose |
Loading dose = Vd × target concentration ÷ bioavailability |
Vd in L or L/kg; target concentration in mg/L; bioavailability unitless |
Loading dose is mainly determined by volume of distribution and the desired plasma concentration, and IV bioavailability is usually treated as 1. |
Preterm infants have a higher proportion of total body water, requiring larger loading doses per kg for water-soluble drugs (e.g., gentamicin), despite having lower clearance. |
| Maintenance dose |
Maintenance dose = target concentration × clearance × dosing interval ÷ bioavailability |
Concentration in mg/L; clearance in L/hr; interval in hr |
Maintenance dose is mainly determined by clearance because it replaces the amount of drug eliminated during the dosing interval. |
Maintenance intervals must be prolonged in extremely premature infants or those with HIE undergoing therapeutic hypothermia due to reduced GFR. |
| Drug half-life |
t½ = 0.693 × Vd ÷ clearance |
Vd in L; clearance in L/hr; result in hours |
Half-life increases when volume of distribution increases or clearance decreases. |
Half-life is highly prolonged at birth and decreases over the first weeks of life as GFR and hepatic enzyme systems mature. |
| Elimination rate constant |
Kel = clearance ÷ Vd |
Clearance and Vd in compatible units; result often hr⁻¹ |
Kel describes the fraction of drug eliminated per unit time and is related to half-life by t½ = 0.693/Kel. |
Kel describes the percentage of drug cleared per unit time. A low Kel translates to a long half-life, necessitating wider dosing intervals. |
| Volume of distribution |
Vd = amount of drug in body ÷ plasma concentration |
Drug amount in mg; concentration in mg/L; result in L or L/kg |
Vd is an apparent space that helps explain why some drugs distribute widely into tissues and require larger loading doses. |
Apparent volume of distribution of hydrophilic drugs is significantly higher in neonates than adults due to their high extracellular fluid volume. |
| Bilirubin rate of rise |
Rate mg/dL/hr = (new bilirubin − old bilirubin) ÷ hours between levels |
Bilirubin in mg/dL; time in hours |
AAP guidance for infants ≥35 weeks states that a rapid rise of ≥0.3 mg/dL/hr in the first 24 hours or ≥0.2 mg/dL/hr afterward suggests hemolysis. |
Hemolytic disease (e.g., Rh or ABO incompatibility) is highly suspected if TSB rises >0.3 mg/dL/hr in first 24h. Prompt Coombs test and serial checks are indicated. |
| Difference from phototherapy threshold |
Δ-TSB = phototherapy threshold − measured TSB |
TSB and threshold in mg/dL |
AAP hyperbilirubinemia management for infants ≥35 weeks uses age in hours, gestational age, neurotoxicity risk factors, and distance from the treatment threshold. |
Initiate phototherapy immediately if TSB meets or exceeds the threshold. For infants close to the threshold, serial tracking and hydration assessment are critical. |
| Sensitivity |
Sensitivity = TP ÷ (TP + FN) |
Use raw counts; result as decimal or percent |
Sensitivity tells how often the test is positive when disease is truly present, so high sensitivity is useful for screening. |
High sensitivity is crucial for screening tests (e.g., newborn screening) to minimize false negatives, but positive results must be confirmed with more specific diagnostic tests. |
| Specificity |
Specificity = TN ÷ (FP + TN) |
Use raw counts; result as decimal or percent |
Specificity tells how often the test is negative when disease is truly absent, so high specificity is useful for confirming disease. |
High specificity minimizes false positives, preventing unnecessary anxiety and invasive diagnostic testing in healthy neonates. |
| Positive predictive value |
PPV = TP ÷ (TP + FP) |
Use raw counts; result as decimal or percent |
PPV tells the chance that a baby truly has the disease when the test is positive, and it changes strongly with disease prevalence. |
PPV is highly dependent on disease prevalence. In low-prevalence populations, even a highly specific test will yield many false positives. |
| Negative predictive value |
NPV = TN ÷ (FN + TN) |
Use raw counts; result as decimal or percent |
NPV tells the chance that a baby truly does not have the disease when the test is negative, and it also changes strongly with disease prevalence. |
NPV is also prevalence-dependent. A high NPV gives clinical confidence to rule out a condition (e.g., ruling out early-onset sepsis with a negative blood culture). |
| Likelihood ratios |
LR+ = sensitivity ÷ (1 − specificity) and LR− = (1 − sensitivity) ÷ specificity |
Sensitivity and specificity as decimals |
LR+ helps rule in disease when high, and LR− helps rule out disease when low. |
LR+ > 10 strongly confirms a diagnosis; LR- < 0.1 strongly rules it out. LRs are independent of disease prevalence, unlike PPV and NPV. |
| Relative risk |
RR = [a/(a+b)] ÷ [c/(c+d)] |
Use 2×2 table counts |
RR compares the probability of an outcome in the exposed group with the probability in the non-exposed group. |
RR compares risk between exposed and unexposed groups. A ratio of 1 indicates no difference; RR < 1 indicates a protective effect of the exposure/intervention. |
| Odds ratio |
OR = a×d ÷ b×c |
Use 2×2 table counts |
OR compares odds rather than direct risk and is common in case-control studies and logistic regression. |
OR compares odds of exposure between cases and controls. It approximates relative risk only when the disease prevalence is low (rare disease assumption). |
| Number needed to treat |
NNT = 1 ÷ absolute risk reduction |
ARR as decimal, not percent |
NNT estimates how many infants need an intervention to prevent one additional adverse outcome. |
NNT represents the number of patients who must receive the treatment to prevent one adverse event. A lower NNT indicates a highly effective intervention. |
| Executive summary |
N/A |
Website design row |
This table converts the uploaded NICU formula sheet into display-ready formulas with explicit units, neonatal caveats, and website-facing explanations. I kept the formulas that were present in your uploaded table, clarified ambiguous constants, standardized units, and added high-yield NICU rows for fluids, glucose, enteral feeding, TPN, electrolytes, growth, and practical bedside calculators. Neonatal interpretation is emphasized because many “generic pediatric” formulas behave differently in preterm infants, during the first postnatal days, and under respiratory support. |
For the website, the safest pattern is: show the formula, then show assumptions, then show a “when not to trust this” note. Many row formulas are mathematically correct but clinically unsafe if applied without gestational age, day of life, urine output, renal function, hemodynamics, or blood-gas context. Primary neonatal fluid and nutrition background comes from RCH, NIDDK, NCBI Bookshelf, Health Canada, and AAP-family material. |
| Assumptions and constants used across formulas |
Common defaults:
FiO2 as a decimal; Pb = local barometric pressure (sea level ≈ 760 mmHg); PH2O = 47 mmHg at 37°C; respiratory quotient R ≈ 0.8; glucose D% means g/100 mL; for monovalent ions, mmol = mEq. |
Pb in mmHg; glucose concentration in %; electrolytes in mmol/L or mEq/L; FiO2 unitless decimal. |
These constants make formulas internally consistent. The most important bedside clarification is GIR: D10 contains 10 g/100 mL = 100 mg/mL, so the famous bedside constant 0.167 is simply 10/60 when using D% and mL/hr. For altitude, the rigorous method is not a crude “altitude factor”; it is substituting the local barometric pressure into the alveolar gas equation. |
Always show the assumptions next to the formula on the website. If you hide them, users will mix % glucose, mg/mL, FiO2 in percent versus decimal, and mmHg versus kPa. Original formula inventory from the uploaded table. |
| Typical neonatal targets cheat sheet |
Common bedside targets:
GIR: term 4–6 mg/kg/min; preterm 6–8 mg/kg/min.
Urine output: about 1–5 mL/kg/hr in many NICU contexts.
Early NICU TFI example: day 1 about 60 mL/kg/day, day 2 about 80, day 3 about 100, day 4–5 about 120, but adjust for GA, IWL, phototherapy, PDA, renal status, and disease.
Reasonable growth target for many preterm infants: weight gain 15–20 g/kg/day. |
Gestational age; day of life; weight; clinical condition; urine output; serum electrolytes; glucose. |
These are reference targets, not prescriptions. They are useful for educational comparison tables on a website because they let the reader interpret a calculator result immediately. In practice, the same numerical result can be appropriate, low, or unsafe depending on whether the infant is a 24‑week ELBW infant under radiant warmer, a term infant with HIE under fluid restriction, or a recovering feeder-grower. |
Never present these as universal “normal values.” RCH explicitly notes that neonatal fluid needs depend on birth weight, gestation, corrected age, illness, and insensible losses; Health Canada and international expert tables emphasize individualized preterm nutrition needs. |
| Enteral feed volume per day |
Enteral volume (mL/day) = enteral prescription (mL/kg/day) × weight (kg) |
Enteral goal in mL/kg/day; current working weight in kg. |
This is the basic feed-volume calculator used for trophic feeds, feed advancement, and full enteral goal setting. It is the quickest way to translate neonatal nutrition plans into actual measurable milk volumes. |
For nutritional interpretation, volume alone is incomplete. Human milk, fortified human milk, term formula, and preterm formula deliver very different calories, protein, sodium, calcium, and phosphorus at the same mL/kg/day. |
| Enteral feeding advancement rate |
Advance (mL/kg/day) = new target − previous target
New total daily feed volume (mL/day) = new target × weight |
Previous and new enteral prescriptions in mL/kg/day; weight in kg. |
This is the simplest display-friendly calculator for feed advancement. It is less about one universal “correct” rate and more about transparently showing the step increase and its daily/feed-level consequence. For a website, this row works well when paired with unit-specific local protocols and a note that advancement depends on gestation, NEC risk, growth, hemodynamic stability, and tolerance. Nutritional goals for preterm feeding aim to support fetal-like growth and reduce extrauterine growth failure. |
Do not embed a single mandatory advancement rate unless you explicitly label it as local practice. Evidence-based nutrition sources emphasize individualized feeding strategy rather than one universal step size. |
| Sodium intake |
Sodium intake (mg/kg/day) = [sodium concentration (mg/100 mL) × volume (mL/kg/day)] ÷ 100 |
Sodium content in mg/100 mL or mg/100 kcal; feed or formula volume in mL/kg/day. |
This formula converts product composition into actual sodium exposure. Health Canada’s international tables show that preterm products contain more sodium than standard products because preterm infants have distinct growth and renal physiology needs. |
Do not confuse sodium intake with serum sodium. Hyponatremia in the NICU is often a water-balance problem rather than simply a sodium-intake problem, and hyperglycemia can lower measured sodium by translocational dilution. |
| Potassium intake |
Potassium intake (mg/kg/day) = [potassium concentration (mg/100 mL) × volume (mL/kg/day)] ÷ 100 |
Potassium content in mg/100 mL or mg/100 kcal; feed or PN volume in mL/kg/day. |
This is the potassium parallel to sodium-intake calculation. It is useful for calculating total intake from formula, fortified milk, PN, and additives. Health Canada’s summarized expert recommendations show meaningful potassium content in preterm nutritional products and emphasize composition awareness. |
Interpret serum potassium with hemolysis, renal function, acidosis, urine output, transfusions, and sample quality in mind. Intake is only one part of potassium balance. |
| Calcium intake |
Calcium intake (mg/kg/day) = [calcium concentration (mg/100 mL or mg/100 kcal) × intake] ÷ 100 |
Calcium concentration in mg/100 mL or mg/100 kcal; corresponding volume or kcal intake. |
Preterm nutritional products are intentionally mineral-enriched to better approximate fetal mineral accretion. Health Canada’s expert tables list calcium and phosphorus targets per 100 kcal and emphasize that metabolic monitoring is part of assessing nutritional adequacy. |
Calcium should be interpreted together with phosphorus, alkaline phosphatase, vitamin D exposure, and bone-mineralization context. Intake calculators are useful, but ionized calcium and clinical signs remain important in sick neonates. |
| Phosphorus intake |
Phosphorus intake (mg/kg/day) = [phosphorus concentration (mg/100 mL or mg/100 kcal) × intake] ÷ 100 |
Phosphorus concentration in mg/100 mL or mg/100 kcal; corresponding volume or kcal intake. |
Phosphorus is central to bone mineralization and energy metabolism. A formula or fortifier can appear “adequate” by calories while still undersupplying phosphorus if composition is not examined. Health Canada’s expert table provides practical preterm phosphorus targets per 100 kcal. |
Always review calcium and phosphorus together. Isolated phosphorus interpretation is incomplete, and low phosphorus can worsen osteopenia risk or occur in refeeding-like states. |
| Calcium-to-phosphorus ratio |
Ca:P ratio = calcium intake ÷ phosphorus intake |
Calcium and phosphorus expressed in the same units, usually mg or mmol. |
The Ca:P ratio is a nutrition-quality check rather than a stand-alone clinical endpoint. Health Canada’s expert summary lists a typical calcium-to-phosphorus ratio around 1.2–2.0, reflecting the need for balanced mineral delivery rather than simply “more calcium.” |
A “normal” ratio does not prove adequate total mineral intake; both absolute delivery and the ratio matter. Also, serum calcium can look acceptable while total mineral support remains inadequate for bone accretion. |
| Fluid bolus calculation |
Bolus volume (mL) = dose (mL/kg) × weight (kg) |
Usual prescribed dose in mL/kg; weight in kg. |
This is the standard shock/resuscitation calculator. RCH neonatal and pediatric guidance uses 10–20 mL/kg isotonic crystalloid boluses, with reassessment after each bolus; packed red cells at 10 mL/kg are first-line in hemorrhagic scenarios in pediatric guidance, while neonatal management depends on cause and local protocols. |
Do not automatically “stack” boluses without reassessment in neonates. Consider shock phenotype, PDA, myocardial dysfunction, hemorrhage, pulmonary edema risk, and whether blood rather than crystalloid is needed. Glucose-containing fluids should not be used as shock boluses. |
| Maintenance fluid by Holliday–Segar adapted for neonates |
Classic Holliday–Segar:
0–10 kg: 100 mL/kg/day
10–20 kg: 1000 + 50 × (kg − 10)
>20 kg: 1500 + 20 × (kg − 20) |
Weight in kg. |
This formula is useful educationally because it remains the standard pediatric “maintenance fluid” rule, but it is not the right primary rule for NICU day-1/day-2/day-3 prescribing. RCH’s pediatric IV fluid guideline explicitly excludes neonates and premature babies from routine use of the calculation, while the neonatal guideline uses day-of-life total fluid plans and illness-specific adjustments. |
For Neonatology Academy, the clearest wording is: “Use neonatal TFI tables in NICU; Holliday–Segar is mainly for older infants/children or selected stable post-neonatal situations.” This prevents a common and important educational error. |
| Corrected sodium for hyperglycemia |
Nacorrected (mEq/L) ≈ Nameasured + 1.6 × [(glucose mg/dL − 100) ÷ 100]
SI form: Nacorrected ≈ Nameasured + 1.6 × [(glucose mmol/L − 5.6) ÷ 5.6] |
Measured sodium in mEq/L or mmol/L; glucose in mg/dL or mmol/L. |
This bedside correction estimates the translocational fall in serum sodium caused by hyperglycemia. For a neonatal website, it is useful as a conceptual aid: hyperglycemia can make sodium appear lower because glucose raises extracellular tonicity and shifts water extracellularly. |
This estimate is widely used, but neonatal-specific validation is limited and correction factors can differ in severe hyperglycemia. Present it as an estimate, not a definitive treatment target. Always interpret with measured tonicity/osmolality, fluid balance, and GIR. |
| Corrected calcium |
Corrected Ca (mmol/L) ≈ measured total Ca + 0.02 × [40 − albumin (g/L)]
Conventional form: Corrected Ca (mg/dL) ≈ measured total Ca + 0.8 × [4.0 − albumin (g/dL)] |
Total calcium in mmol/L or mg/dL; albumin in g/L or g/dL. |
This is a bedside estimate intended to adjust total calcium for hypoalbuminemia. It is useful for educational purposes because total calcium can underrepresent biologically active calcium when albumin is low. search2turn23search0 |
In sick neonates, ionized calcium is preferred whenever available, because albumin-corrected total calcium may misclassify physiologic calcium status. Present this row on the website as a surrogate estimator, not as a replacement for ionized calcium. search2turn23search1 |
| Altitude effect on PaO2 |
Rigorous approach: Use the alveolar gas equation with local barometric pressure:
PAO2 = FiO2 × (Pb − 47) − PaCO2/R |
FiO2 as decimal; Pb in mmHg; PaCO2 in mmHg; R ≈ 0.8. |
The uploaded sheet included an altitude-related row. For clarity and correctness, the website version is better expressed through the alveolar gas equation, because altitude changes alveolar oxygen mainly by lowering barometric pressure. This is more rigorous than a crude multiplicative “altitude factor.” |
Never interpret PaO2 altitude effects without stating Pb, FiO2, and PaCO2. For education, show a sea-level versus altitude example graph rather than a fixed shortcut factor. |
| Oxygen consumption by Fick principle |
V̇O2 (mL O2/min) = CO × [CaO2 − CvO2] × 10 |
Cardiac output in L/min; arterial and venous oxygen contents in mL/dL. |
This is the classic Fick oxygen-consumption relationship. It links systemic flow to arteriovenous oxygen extraction and is helpful for teaching shock, anemia, shunt physiology, and why tissue oxygen debt can coexist with apparently acceptable arterial oxygenation. Original formula present in your sheet. |
True mixed venous sampling is difficult in many neonates; central venous values are not identical. This is better as an educational physiology formula than a casual bedside shortcut. |
| Saturation threshold for visible cyanosis |
Approximate saturation at cyanosis = [(Hb − 5) ÷ Hb] × 100 |
Hemoglobin in g/dL; threshold assumes ~5 g/dL deoxygenated hemoglobin for visible cyanosis. |
This row explains why polycythemic infants can look cyanotic at higher oxygen saturations and anemic infants may look relatively pink despite dangerous hypoxemia. It is a very useful educational physiology pearl for a neonatal website. Original concept/formula present in your uploaded sheet. |
Visible cyanosis is an unreliable screening test. Lighting, skin pigmentation, perfusion, and hemoglobin concentration all affect recognition. Use pulse oximetry and blood gas evaluation when clinically indicated. search4turn16search1 |
| Laplace law |
For a sphere: P = 2T ÷ r
For a cylinder: P = T ÷ r |
Pressure P; surface tension T; radius r. |
Laplace law explains why small alveoli are prone to collapse when surface tension is high and why surfactant is so important in neonatal lung stability. This is one of the most neonatology-specific physiology formulas in the whole table. Original formula included in your sheet. |
Surfactant stabilizes alveoli by reducing surface tension (T) more in smaller alveoli than in larger ones. Without surfactant, smaller alveoli collapse and empty into larger ones (atelectasis). Interpret with clinical lung compliance and ETT size. |