Various formulas commonly used in clinical practice
1.Sodium supplementation calculator
The following formula can be used for men
Total sodium supplementation (mmol) = [142 – patient’s blood Na+ (mmol/L)] × body weight (kg) × 0.6
Total amount of sodium chloride (g) = [142 – patient’s blood Na+ (mmol/L)] × body weight (kg) × 0.035
Should be supplemented with saline (ml) = [142 – patient’s blood Na+ (mmol/L)] × body weight (kg) × 3.888
Should be supplemented with 3% sodium chloride = [142 – patient’s blood Na+ (mmol/L)] × body weight (kg) × 1.1666
Should be supplemented with 5% NaCl (ml) = [142 – patient’s blood Na+ (mmol/L)] × body weight (kg) × 0.7
The following formula can be used for women
Total sodium supplementation (mmol) = [142 – patient’s blood Na+ (mmol/L)] × body weight (kg) × 0.5
Total amount of sodium chloride (g) = [142 – patient’s blood Na+ (mmol/L)] × body weight (kg) × 0.03
Should be supplemented with saline (ml) = [142 – patient’s blood Na+ (mmol/L)] × body weight (kg) × 3.311
Should be supplemented with 3% sodium chloride (ml) = [142 – patient’s blood Na+ (mmol/L)] × body weight (kg) × 3.311
Should be supplemented with 5% sodium chloride (ml) = [142 – patient’s blood Na+ (mmol/L)] × weight (kg) × 0.596
Note: ①142 in the above formula is the normal blood Na+ value in mmol/L.
②The results obtained according to the formula can generally be 1/2 to 1/3 of the total amount first, and then the next treatment plan can be adjusted according to the clinical situation and test results.
③Unit conversion.
Sodium: mEq/L×2.299=mg/dlmg/dl×0.435=mEq/L
mEq/L×1/chemical valence=mmol/L
Sodium chloride: g×17=mmol or mEq, (mmol)×0.0585=g/L
2.Rehydration calculator
(1) Determine the nature of dehydration based on serum sodium.
Nature of dehydration blood Na+mmol/L
Hypotonic dehydration >130
Isotonic dehydration 130 to 150
Hyperosmolar dehydration >150.
(2) Judgment of infusion volume based on hematocrit.
Infusion volume = normal blood volume × (normal erythrocyte specific volume / patient erythrocyte specific volume)
(3) Calculate the volume of rehydration according to the body surface area.
800～1200ml/(m2?d) in the early stage of shock.
1000～1400ml (m2?d) in the late stage of body shock.
After the correction of shock rehydration physiological needs of 50 ~ 70%.
(4) General rehydration formula.
Rehydration amount = 1/2 cumulative loss + additional loss of the day + normal daily requirement
2.Iron supplementation calculator
Total iron deficiency [mg] = body weight [kg] x (Hb target value – Hb actual value) [g/l] x 0.238 + stored iron [ mg]
Stored iron = 10mg/kg body weight (<700mg)
If the total requirement exceeds the maximum single dose administered, the dose should be administered in divided doses. If no change in hematological parameters is observed 1-2 weeks after administration, the initial diagnosis should be reconsidered.
Calculating the dose of iron supplementation in patients with blood loss and support for autologous blood donation
Amount of iron to be supplemented [mg] = amount of blood loss units x 200
4. Electrolyte supplementation calculator
Total amount of an electrolyte deficiency.
mmol/L = (normal mmol/L-measured mmol/L) × body weight (kg) × 0.6
(normal mmol/L – measured mmol/L) × body weight (kg) × 0.6
Grams = mmol contained in 1g of electrolytes
5. Resting energy expenditure calculator
Harris-Benedict calculation formula.
Female: REE (Kcal/d)=655+9.6W+1.7H-4.7A
Male: REE (Kcal/d)=66+13.7W+5.0H-6.8A
[W=weight (Kg); H=height (cm); A=age (years)]
6. Drug infusion rate calculator
(1) Intravenous infusion speed and time reference data
Volume of liquid (ml) Drip rate (gtt/min) Time (h)
500 30 4
500 40 3
500 60 2
(2) Infusion speed determination
Input volume per hour (ml) = number of drops per minute × 4
Drops per minute (gtt/min) = total ml of fluid input ÷ [total infusion time (h) × 4]
Infusion time required (h) = total ml of fluid input ÷ (number of drops per minute × 4)
(3) Intravenous infusion drip into the number of calculation method
Input volume per h × number of drops per ml (15 gtt)
① Known input volume per h, then the number of drops per min = 60 (min)
Number of drops per min × 60 (min)
② Known number of drops per min, then input per h = equivalent number of drops per min (15gtt)
7. Creatinine clearance calculator
(1) Cockcroft formula.
Ccr=(140-age)×weight(k g)/[72×Scr(mg/dl) ] or
Ccr=[(140-age)×body weight(k g)]/[0.818×Scr(umol/L)
Note the units of creatinine, calculated for women × 0.85
(2) Simplified MDRD formula.
GFR(ml/min1.73m2)=186×(Sc)-1.154×(age)-0.203×(0.742 female)
Note: Ccr is creatinine clearance; GFR is glomerular filtration rate; Scr is serum creatinine (mg/dl); age is in years; weight is in kg.
(3) Standard 24-hour urine retention calculation method.
Urine creatinine concentration (μmol/L) × urine volume per minute (ml/min)
Ccr = plasma creatinine concentration (μmol/L)
8.Body surface area calculator
Chinese adult male BSA=0.00607H+0.0127W-0.0698
Chinese adult female BSA=0.00586H+0.0126W-0.0461
Pediatric body surface area calculation formula: BSA=0.0061H+0.0128W-0.1529
9.Blood gas analysis
(1) acid-base (pH), reference value 7.35-7.45. <7.35 is acidemia, >7.45 is alkalemia. However, normal pH does not completely exclude the absence of acid-base imbalance.
(2) The reference value of partial pressure of carbon dioxide (PCO2) is 4.65~5.98kPa (35~45mmHg) multiplied by 0.03, which is the H2CO3 content. Exceeding or falling below the reference value is called hypercapnia or hypocapnia. >55mmHg has the danger of inhibiting the respiratory center. It is the main indicator to judge each type of acid-base poisoning.
(3) Total carbon dioxide (TCO2), reference value 24-32mmHg, represents the sum of CO2 and HCO3 in blood, which is affected by both respiration and metabolism in the body. It decreases significantly in metabolic acidosis and increases significantly in alkalosis.
(4) Oxygen partial pressure (PO2) reference value 10.64~13.3kpa (80~100mmHg). Below 55mmHg is respiratory failure, <30mmHg can be life-threatening.
(5) Oxygen saturation (SatO2), reference value 3.5kPa (26.6mmHg).
(6) Actual bicarbonate (AB), reference value 21.4~27.3mmHg, standard bicarbonate (SB) reference value 21.3~24.8mmol/L. AB is an important indicator of metabolic acid-base imbalance in the body, and SB also reflects metabolic factors when calculated under specific conditions. A normal AB is an important indicator of metabolic acid-base imbalance in the body. Both are low for metabolic acidosis (uncompensated), both are high for metabolic alkalosis (uncompensated), AB>SB for respiratory acidosis, AB
(8) Anion gap (AG), reference value 8 to 16 mmol/L, is an important indicator for early detection of mixed acid-base toxicity.
To determine the acid-base imbalance, we should first understand the clinical situation, generally based on pH, PaCO2, BE (or AB) to determine the acid-base imbalance, and PaO2 and PaCO2 to determine the hypoxia and ventilation. pH beyond the normal range indicates the existence of imbalance. A normal pH may still indicate an acid-base imbalance, a normal PaCO2 may indicate a respiratory acid-base imbalance, and a normal BE may indicate a metabolic acid imbalance. However, blood gas and acid-base analyses are sometimes combined with other tests and clinical dynamics in order to make a correct diagnosis.
10.Diabetes Diet Calculator
The total daily dietary calories are determined by the patient’s body weight and activity intensity. According to nutrition, 1 kcal (1 kcal is 4.2 joules) is often used as the unit of calories, and each gram of carbohydrate or protein produces 4 kcal in the body, and each gram of fat produces 9 kcal of calories.
(1) weight refers to the ideal weight, simple calculation formula: ideal weight (kg) = height (cm) – 105 according to this formula, more than 20% of the ideal weight for obesity, less than the standard 20% for wasting, obesity or wasting are not conducive to health.
(2) activity intensity: the human body’s caloric needs are most affected by the intensity of labor, different body types of diabetics per kilogram of body weight required caloric table.
Labor intensity Lean (kcal/kg) Normal (kcal/kg) Obese (kcal/kg)
Bed rest 20~25 15~20 15
Light physical labor 35 30 20~25
Medium physical labor 40 35 30
Heavy physical labor 45~50 40 35
11. Assessment of hemodialysis adequacy
Kt/V is the most widely used parameter of urodynamic model to evaluate the adequacy of dialysis in dialysis units at home and abroad. Therefore, Kt/V can be regarded as an indicator of the volume of a dialysis treatment.
Daugirdas second generation logarithmic equation.
Kt/V=-In(R-0.008×t) + (4-3.5×R)×UF/W
where In is the natural logarithm; R is (post-dialysis BUN) ÷ (pre-dialysis BUN); t is the duration of a dialysis session, expressed in hours; UF is the ultrafiltration volume, expressed in liters; and W is the patient’s post-dialysis weight expressed in kilograms.
12. Assessment of peritoneal dialysis adequacy
Peritoneal dialysis therapy is an effective treatment for both acute and chronic renal failure. Although a great deal of clinical experience has been gained with peritoneal dialysis, there is no clear uniformity in the objective criteria and perception patterns of dialysis “adequacy”. Previously, dialysis prescriptions were set empirically, and the therapeutic amount of “adequate” dialysis was to keep the patient alive and relatively asymptomatic, but because of the subjective unreliability and the inconsistency between clinical performance and severity of the disease, it is important to give a quantitative evaluation and its relationship to clinical outcomes. It will not only determine the relationship between clinical presentation, prognosis and biochemical parameters. It also guides the setting of dialysis prescriptions and evaluates the therapeutic efficacy of dialysis treatment.
Urea clearance (KT/V): A parameter reflecting the decrease in blood urea nitrogen on dialysis assuming no weight gain between dialysis sessions. k represents the urea clearance on dialysis (liters/week), T is the duration of dialysis (days per week of dialysis), and V is the volume of urea distribution. It is used to reflect the total level of dialysis treatment or to guide the “dose” of dialysis as an index.
The most common method for calculating the urea volume of distribution (V) is as follows
Male (weight (kg)*0.6) Female (weight (kg)*0.55.
However, there are other methods such as
watson&watson method:
Male (2.447-0.09516*age + 0.1074*height (cm) + 0.3362*weight (kg)).
Females (-2.097+0.1069*height(cm)+0.2466*weight(kg)).
Modified hume and weyers method:
Males (0.19678*height(cm)+0.29571*weight(kg)-14.249).
Females (0.17003*height(cm)+0. 21371*weight(kg)-9.926).
Children: (0.135*height(cm)^0.535*weight(kg)^0.666).
Some formulas for pediatrics.
Weight calculation method :
<6 months or less: birth weight + months of age x 0.7
7 to 12.
6 + month age x 0.25
>7.
Months of age x 2 + 7 (8)
Body length calculation.
Age x 5 + 75 cm (≥ 2 years)
Blood pressure.
Systolic blood pressure = age × 2 + 80 mmHg
Diastolic blood pressure = 2/3 × systolic blood pressure
Cuff: width = upper arm circumference × 1/2, pediatric patients should cover the upper arm length 2/3, infants should only use 2.5cm cuff
Pediatric lumbar puncture depth calculation formula.
The first: (cm) = 1.29 + 0.082 × weight (kg)
The second: (cm) = 0.77 + 2.56 × body surface area (m )
Sacral canal volume (ml) = ( D -15)/2+4
(D = distance from C7 to sacral fissure)
Axillary sheath volume (ml) = age × 2 + 4
Internal diameter of tracheal tube (mm).
Child’s age/4+4.0 (or 4.5)
Pediatric fluid maintenance volume per hour
Body weight Fluid maintenance volume (ml/h)
<4´10kg kg
2+20´10~20kg kg
21kg or more kg+40
The concept and calculation of solution tension
1.Definition and calculation of tension is the attraction of particles of solution solute to water, the greater the concentration of the solution, the greater the attraction to water. The tension of a solution is judged by its osmolarity compared with the normal value of plasma osmolarity (280-320 mosm/L, calculated by taking the average value of 300 m osm/L) compared to the ratio obtained, it is a value that has no units but reflects the concentration of the substance.
Solution osmotic pressure = (percentage concentration × 10 × 1000 × the number of ions per molecule can be dissociated) / molecular weight. For example, the osmotic pressure of 0.9% NaCl solution = (0.9×10×1000×2)/58.5=308mOs m / L (794.2kPa) the osmolarity and plasma normal osmolarity compared to the ratio of about 1, so the solution tension is 1 Zhang. Another example is 5% NaHCO3 solution osmotic pressure = (5 × 10 × 1000 × 2) / 84 = 1190.4mO sm / L (3069.7kPa) the osmolarity and plasma normal osmolarity, the ratio is about 4, so the solution tension is 4 sheets.
2, the tension of several commonly used solutions.
10% (NaCl) 11 sheets (clinically it can be calculated by 10 sheets)
0.9% (NaCl) 1 sheet
5 % (NaHCO3) 4 sheets
10% (KCl) 9 sheets
10% (GS) 0 sheets (no tension, equivalent to water)
In most clinical cases, the above solutions are used to prepare other required liquids for treatment, and it is only necessary to remember the tensions of these solutions to be able to prepare and calculate the required solutions and tensions flexibly and freely; there is no need to investigate why 10% NaC l tension is 10 sheets of this complex calculation process.
3, examples to illustrate the calculation of mixed solution tension
Example 1, 10% NaCl (10ml) + 10% GS (90 ml), ask the tension of the group of solutions. According to C1 × V1 = C2 × V2 listed in the formula: 10 × 10 = X × 100, X = 1 sheet
Example 2, 10% NaCl (20 ml) + 5% NaH CO3 (25ml) + 10% GS (255ml), ask the tension of the group of solutions. 10 × 20 + 4 × 25 = X × 300,X = 1 sheet.
Example 3, want to prepare a group of 300ml, 2/3 sheets of liquid, now using 5% NaHCO3 (15 ml), how many ml of 10% NaCl is still needed. 10×X+4×15=2/3×300. X = 14 ml then, and then add 10% GS 271 (270) ml after the required liquid can be prepared (300-15- 14 = 271ml, GS for 0 sheets)
2:1 isotonic solution is the preferred solution for volume expansion in resuscitation shock, which has fixed components and is prepared from 2 parts of isotonic salt solution + 1 part of isotonic base solution. Students feel very difficult to prepare 2:1 solution, in order to facilitate students’ memory, rapid calculation, preparation, it gives a simple formula (derivation process is more complex, do not need to elaborate) to prepare 2:1 solution Mml, then need
10% NaCl = M / 15ml —-a
5% NaHCO3=M/12ml —b
10% GS = M-a-bml
Example 4: To prepare 300ml of 2:1 solution, 10% NaCl, 5% Na HCO3, 10% GS how many ml each. 10% NaC l=300/15=20ml5% NaHCO3=300/12=25 ml10%GS=300-20-25=255ml so that 2:1 solution can be prepared quickly by a simple formula
Diuretics Tachyphylaxis is more suitable for the treatment of pulmonary edema and cerebral edema. Tachyphylaxis can also reduce the preload of the heart through vasodilatation. The effect on the heart starts 5 minutes after intravenous administration, while the diuretic effect starts about 20 minutes later.
Dose: Inject 20-40mg intravenously at one time, if it is not effective, the dose can be increased and injected intravenously again after 15 minutes.
Precautions: to prevent electrolyte disturbances, especially hypokalemia.
(H) Intensive treatment of cerebral resuscitation drugs used for cerebral resuscitation are also beneficial to the resuscitation of the heart muscle and other tissues. Many years of clinical practice have concluded that cerebral resuscitation is the key to successful resuscitation of cardiac arrest. Although there are various measures for brain resuscitation, drugs are very important, but it is still in the laboratory and clinical observation stage, there is no drug as a routine drug for brain resuscitation or cardiac, pulmonary and brain resuscitation. For example, in 1986, the National Institutes of Health (NIH) sponsored a trial of Lidoflazine (Lidoflazine, a powerful Ca2+ channel blocker) in 25 hospitals in 12 countries to improve the effectiveness of brain tissue recovery function. There are also clinicians in China who are conducting research efforts in this area. Several drugs that are currently receiving more attention are discussed below.
1, calcium 2 + channel blockers after cardiac arrest, Ca2 + play a destructive role, especially the reperfusion of the role of destruction of cell structure, has been described in the pathophysiology section. Therefore, it has been advocated that Ca2+ channel blockers should be added during reperfusion, but most of them are currently used orally in our clinic and are not applicable. Although isoptin (Verapamil) is available as an intravenous agent, it has vasodilator and acute force-modifying effects and is not suitable for those with poor cardiac function. It is also known to cause conduction block by its action on the atrioventricular junction. The final conclusion of lidofloxacin is not yet available, and it is not easily available in our market.
2, thromboxane antagonist In the laboratory, the use of anti-inflammatory pain (Indomethacin) can antagonize thromboxane, prostacycline (Prostacycline) also achieved good results in the experiment against thromboxane, but has not yet achieved a positive clinical conclusion.
3, Fe2+ chelating agent Desferrioxamine can combine with Fe2+ and become a compound that does not work, thus preventing the destructive effect of free Fe2+ in the cell. It is also only in the clinical observation stage. Use infusion pump, day 1 intravenous drip 15-50mg/kg body weight, 6-12h drip; day 2 appropriate to reduce the amount.
4.Oxygen free radical scavenger The normal body peroxisomal enzymes play a role in scavenging such highly reactive substances. After cardiac arrest, these substances are produced in the body in excess and are very destructive. Although a variety of scavengers such as anticyclic acid, vitamin E, and peroxisomalase have attracted the interest of clinicians, no definite conclusions have been obtained.