Trauma Facts and Formulas

Abstract

Trauma results in a number of emergency department presentations and intensive care unit admissions around the world and a number of formulas, scores, and indices are available for the assessment and management of these patients.

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Trauma results in a number of emergency department presentations and intensive care unit admissions around the world and a number of formulas, scores, and indices are available for the assessment and management of these patients.

1 Hemorrhage

In order to assess the intravascular volume resuscitation needed in a trauma patient, normal blood volumes according to age need to be known (see Table 16.1):

Table 16.1 Normal blood volumes according to age

Severity of Hemorrhage

The severity of hemorrhage in a trauma patient can be classified as shown in Table 16.2:

Table 16.2 Severity of hemorrhage classification trauma patients

The following formula can be utilized to estimate how much whole blood or packed red blood cells (PRBCs) must be administered to change the hematocrit percentage to the desired amount in a trauma patient:

$$ \bf{Transfusion required(mL)}=\mbox{Desired change in Hct} \times \mbox{kg} \times \mbox{factor}$$

where

• Hct = hematocrit

• factor = varies with the volume of blood per body weight (adults and children >2 years, a factor of 1 will achieve a Hct of 70 % using PRBC and 1.75 to achieve a Hct of 40 % using whole blood)

2 Burns

Please refer also to Chap. 3.

There are several formulas that guide the initial fluid resuscitation after burn injuries. Below are the most common formulas used in clinical practice. In all these formulas, 50 % of calculated volume is given during the first 8 h, 25 % of calculated volume is given during the second 8 h, and 25 % of calculated volume is given during the third 8 h.

Fluids used for fluid management in major buns.

Parkland Formula

The Parkland formula can be calculated as:

$$\begin{array}{l}{\bf <24\ h}=\mbox{Ringer's lactated (RL) solution 4 mL /kg/}\%\ \mbox{burn}\\ \qquad\qquad\ \mbox{for adults and 3 mL /kg/}\%\ \mbox{burn for children}\end{array}$$

RL solution is added for maintenance for children:

• 4 mL/kg/h for children 0–10 kg

• 40 mL/h + 2 mL/h for children of 10–20 kg

• 60 mL/h + 1 mL/kg/h for children of ≥20 kg

This formula recommends no colloid in the initial 24 h.

$$ {\bf >24\ h}= \mbox{Colloids given as 20-60}\%\ \mbox{of calculated plasma volume}$$

No crystalloids. Glucose in water is added in amounts required to maintain a urinary output of 0.5–1 mL/h in adults and 1 mL/h in children.

Modified formula:

$${\bf <24\ h}=\mbox{RL 4 mL /kg/}\%\ \mbox{burn (adults)}$$

$${\bf >24\ h}=\mbox{Begin colloid infusion of 5}\%\ \mbox{albumin 0.3-1 mL /kg/}\%\ \mbox{burn / 16 /h}$$

Evans Formula

The Evans formula can be calculated as:

$$ \begin{array}{ll}{\bf <24h}=&\mbox{Crystalloids 1 mL /kg/}\%\ \mbox{burn plus colloids at 1 mL /kg/} \\ &\% {\rm burn plus 2,000 mL glucose in H_{2}O}\end{array}$$

$$ \begin{array}{l}{\bf >24h}=\mbox{Crystalloids at 0.5 mL /kg/}\%\ \mbox{burn, colloids at 0.5 mL /kg/}\% \mbox{burn,}\\ \qquad\qquad\ \ \mbox{and the same amount of glucose in water as in the first 24 h}\end{array}$$

Brooke Formula and the Modified Brooke Formula

The Brooke formula and the modified Brooke formula are calculated as:

$$ \begin{array}{l}{\bf <24h}=\mbox{RL solution 1.5 mL /kg/}\%\ \mbox{burn plus colloids 0.5 mL /kg/}\\ \qquad\qquad\% \mbox{burn plus 2,000 mL glucose in water}\end{array}$$

$$ \begin{array}{l}{\bf >24h}=\mbox{RL 0.5mL /kg/}\%\ \mbox{burn, colloids 0.25 mL /kg/}\%\ \mbox{burn,}\\ \qquad\qquad\ \mbox{and the same amount of glucose in water as in the first 24 h}\end{array}$$

Modified formula = 2 mL Ringer’s lactate/kg/% burn/24 h:

$$ {\bf <24h}=\mbox{No colloids}$$

RL solution 2 mL/kg/% burn in adults and 3 mL/kg/% burn in children.

$$ {\bf >24h}=\mbox{Colloids at 0.3-0.5 mL /kg/}\%\ \mbox{burn and no crystalloids are given}$$

Glucose in water is added in the amounts required to maintain good urinary output.

In addition to these formulas, the evaporative water losses in patients with burns need to be calculated and replaced.

Evaporative Water Loss

Evaporative water loss (EWL) is calculated as:

$$ {\bf EWL(mL/h)}=(25+\%\mbox{BSA burned})\times \mbox{BSA}$$

3 Trauma Scoring Systems

Out of the many used injury scoring systems, the abbreviated injury scale (AIS) is the most commonly used (see Table 16.3):

Table 16.3 The abbreviated injury scale

Trauma Score

The trauma score (TS) is another commonly utilized system and is depicted in Table 16.4:

Table 16.4 The trauma score

Revised Trauma Score

The revised trauma score (RTS) eliminates the assessment of capillary refill and respiratory effort and is calculated as:

$$\begin{array}{l}{\bf RTS}=\mbox{0.9368 GCS + 0.7326 SBP + 0.2908 RR coded values}\\ \qquad\quad\times \mbox{Revised score coefficient}\end{array}$$

where

• GCS = Glasgow coma scale

• SBP = systolic blood pressure

• RR = the respiratory rate

For children and infants, the pediatric trauma score is utilized (see Table 16.5):

Table 16.5 The pediatric trauma score

4 Neurological Trauma

AVPU Method

Within the primary survey, an early neurological trauma evaluation can be accomplished using the AVPU method:

• A = alert

• V = responds to verbal stimulation

• P = responds to painful stimulation

• U = unresponsive

Glasgow Coma Scale

The Glasgow coma scale (Table 16.6) is another frequently utilized method of assessment of the neurological status of the trauma patient:

Table 16.6 Glasgow coma scale

Cerebral Perfusion Pressure

In those patients with severe head injuries and intracranial pressure monitoring, cerebral perfusion pressure (CPP) is commonly utilized in management and is calculated as:

$$ {\bf CPP}=\mbox{MAP-ICP}$$

where

• MAP = mean arterial blood pressure

• ICP = intracranial pressure

Pressure–Volume Index

Another useful formula in neurological trauma is that of the calculation of the pressure–volume index (PVI), which is defined as the volume (in mL) necessary to raise the cerebrospinal fluid (CSF) pressure by a factor of 10:

$$ {\bf PVI}=\frac{\Delta V }{\mathrm{log}10({P}_{{p}}/{P}_{0})}$$

where

• Δ V = volume change in the lateral ventricle using a ventricular cannula

• P ₀ = initial ICP

• P _p = peak ICP