(PC-1500) Databook of Anaesthesia & Critical Care Medicine

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An excerpt from Databook of Anaesthesia & Critical Care Medicine, 4^th Revised and Enlarged Edition, 1987, pages 188-201

P. Simple Hand-Held Computer Programs
The majority of readers will have little understanding of computer pro-
gramming, but can use the computing ability of hand-held units in every-
day operating room and intensive care routines. There are several small
models available which are programmable in BASIC (of which there are
dialects). The simple programs that follow are written for the SHARP
PC 1500, 1500A, 1600, and its printer; they are also available under other
trademarks. The programs are easily adaptable to other computers using
BASIC.
  The SHARP applications manual contains statistical programs, stop
watch and timer programs, and a program that may be used to test reaction
time and motor coordination during anaesthetic recovery (mole banging).
  In the listings that follow, < LN: > signifies a new line number that
must be entered by the user in an ascending sequence; usually steps of 5 or
10 are used between numbers, e.g. 10,20,30,40, etc. Where a line number
is an address referred to in another part of the program, it is given a num-
ber - L1, L2, etc. The input of data into these programs follows the com-
mands <INPUT> or <INKEY$>: after <INPUT> the data is first
displayed on the screen and entered by pressing < ENTER>, whereas
with < INKEY$ > the data is immediately entered. Refer to the user's
manual of your machine for details of entering and running programs.

1. Deriving body sUlface area (BSA). This program uses the Du Bois equation,
given elsewhere in this book, for adults [6] and for infants and small
children [10].
(BSA = kg· 0.5378· cm· 0.3964·0.024265).
The address "A" is given to the program.

2. Deriving Ventilation volume. This can be determined from BSA assuming
that oxygen consumption is 136 ml/m² at 37°C, that minute volume can be
derived from oxygen consumption and a target expired pCO₂. A minute
volume is derived based on maintaining a constant expired pCO₂ in the
presence of adequate oxygen. The fractional increase of basal metabolic
rate (BMR) above 37°C is taken as 8% per degree (LN +), and as 7.5%
below 37°C (LN - ).
The address "V" is given.

3. This program uses the Radford nomogram to derive a minute volume and
respiratory rate by "drawing a horizontal line" across the nomogram at a
selected body weight. Using the derived minute volume other breathing
rate/tidal volume combinations can be chosen. The following symbols are
used: TV, tidal volume; RR, respiratory rate. Leave the program by enter-
ing a respiratory rate of 0.
The address "G" is given.

4. A program for entering the date and time on any printed material. It is
accessed from the program being printed by the GOSUB command, and
returns to the same program. There is no address given here; address the
first program line you allocate to this small program. For this to run you
must enter the current date and time into the memory by typing:
TIME = MMDDHH.MMSS < RETURN>
using a 0 prefix to single figure entries (e.g. 2nd January at 11 o'clock
exactly would be 010211.0000).

5. This program uses the data obtained from a Swan Ganz catheter to cal-
culate the derived parameters, and to print them if required. The printed
slip includes the date and time, thus giving the sequence when a number of
results are obtained from one patient. Actual line numbers are used
because of its complexity. WL and WR are calculations of the work of the
left and right heart.
The address is given as "S".

6. A programme using Antoine numbers to derive the vapour pressure of
water and anaesthetics at a given temperature [25]. Line numbers are again
included. Data lines are written in sequence: drug name; mol. wt.; density
of liquid; minimum alveolar concentration (MAC) value; Antoine num-
bers A, B, C. The programme allows a single value to be determined
(Range = 0, Interval = 0), or a series of values from which a vapour pres-
sure vs temperature curve can be drawn. For this a starting temperature is
entered, thereafter the range of temperature, either increasing (+) or
decreasing ( - ), with the intervals also either ( + ) or ( - ), at which the data
points are to calculated. Knowing the vapour pressure allows the calcula-
tion of the usage of liquid anaesthetic drug at a given flow rate. In this pro-
gramme the delivered concentration is taken as the MAC for the drug.
An address of "Z" is assigned.

7. A programme giving dilutions and drip rates of potent drugs in IV infusions
in 60 drops per ml giving sets. Doses are calculated on a body weight
basis. The data lines are written in the sequence: drug name; mg to dis-
solve in 200/250 ml solution; starting dose (μg/kg/min); normal maxi-
mum dose (μg/kg/min); loading dose. The abbreviations NNP and TNT
are for sodium nitroprusside and nitroglycerine, along with lignocaine, ket-
amine and adrenaline.
An address of "D" is assigned.

8. A programme for calculating parameters when using cardiopulmonary
bypass. Calculations are based mainly on BSA so that this programme may
be linked to no.1 above using that data for age and sex. With further data
input of pre-bypass (Hct) haematocrit and machine prime volume (clear
fluid and blood), it is possible to predict the post-bypass Hct and the effect
that a unit of blood would have in raising the level: it is not possible to pre-
dict the volume of blood that must be transfused for full correction of the
Hct without taking other variables into account. Hypokalaemia is some-
times a problem during cardiopulmonary bypass, and thus there is provi-
sion for calculating what a safe bolus of 15% potassium chloride (2 mEq/
ml) would be, based upon its dilution in the combined patient and
machine blood volumes. The user must decided by how many mEq/l the
serum level must be raised, possibly taking the upper limit of normal
(approx. 6 mEq/l) as a target. This is not a measure of the potassium defi-
cit, meaning that such a bolus may have to be repeated. The standard cal-
culation for the correction of metabolic acidosis is included. The pro-
gramme is written so that it stops whenever a result is presented. To move
to the next step, press < ENTER>.
The label "H" is used.

9. A running clock programme that updates each second. The TIME string
must have been entered.
The label "K" is used: pressing "K" whilst running ends the program.

10. Patients vary in their response to full doses of heparin (2-3 mg· kg^-1).
Using the accelerated clotting time (ACT) in seconds as a measure of the
anticoagulant effect of heparin, the response of a given dose can be quanti-
fied (s/mg per kg dose) for individual patients in order to predict follow-
up doses. The user defines a heparin dose based on body weight. An
"ideal" target ACT is taken as 450 s, and the program offers a supplement
if this is not reached with the original bolus, based on a figure for heparin
"activity" in the patient. On the assumption that heparin breakdown fol-
lows a single compartment exponential, and using the peak ACT, the next
ACT reading and the time to this reading from the initial bolus, a "half-
life" of heparin activity is calculated. Finally, by calculating the heparin
activity at a given ACT reading, a neutralizing dose of protamine of 0.6 mg
per mg heparin is calculated. This is less than the 1.0-2.0 mg per kg some-
times recommended, but found to give accurate reversal in the authors'
hands. These concepts are described by Bull et al. [2]. There is an option to
repeat the top up heparin doses using data already in the programme
which can also be entered at hourly intervals. This is done by leaving the
computer to switch off automatically. It later switches on at the same pro-
gram step. This program has been written to run with the Time Lapse Pro-
gram no. 12 so that by entering the time of the initial heparin dose and two
subsequent times, the half-life of heparin and the total time of hepariniza-
tion will be calculated and printed out. This may be left out without affect-
ing the running. Finally, the results may be printed out with name, date
and time.
The program address is given as "C".

11. A variation of the vapour pressure programme can be used for closed cir-
cuit anaesthesia using a liquid injection technique. The method is that first
described by Lin and Mostert [15]. They propose that, provided wash-in of
an anaesthetic mixture is rapid (10 l/min for 5-10 min), uptake of the vola-
tile agent is constant from an early stage, possibly because of rate limiting
across the alveolus. From a knowledge of the alveolar minute volume,
desired inspired concentration and fraction of this concentration absorbed,
the minute consumption of vapour is calculated. This is easily converted to
ml liquid per h (Avogadro's hypothesis - 1 g molecular weight occupies
24l at RTP). Data from the data lines in programme 6 are repeated here
with the addition of uptake ratios for the three drugs. Using the Radford
nomogram programme (3) an alveolar minute volume at 10 breaths per
minute is proposed on which to base uptake calculations. The authors use
a basal flow of about 350 ml of a N₂O/O₂ mixture with 50 ml/min more
oxygen than nitrous oxide and advise using an oxygen analyser in circuit
(see also Lin and Mostert [16]).
The label "L/ is assigned.

12. This short program will calculate the interval in minutes between any
two time entries in a 24-h period. Entries must be made using the 24-h day
system, entries being 1 or more figures, i. e. 5 min past midnight can be
written as 5, 0S, 005 or 0005. Elapsed time periods of less than 1h may be
entered as the clock minute hand readings even if the start time is greater
than the stop time, i. e. starting at 45 and stopping at 15 will give an elapsed
time of 30 min.
This unit may be used to calculate the duration of an anaesthetic, the
duration of action of a drug, peak response times, etc. It has not been
labelled, as it will probably be accessed by a GOSUB/RETURN routine
as is the calendar/time program no.4. In the version given here starting
time is ST$ and stopping time is TS$. The time lapse is TL which is printed
out and may be used in the programme returned to. The times from a start-
ing point to various stages in a procedure can be calculated by re-entering
the value for TS$ and deriving a new TL value. The first two lines are
redundant unless used as an independent program.

13. Finding what is stored in computer memory is made easy by creating a
menu that runs automatically when switched on. It starts with line 1 and
the command ARUN. When using this program make sure that sub-
sequent programs start on a line number above 20.
1: ARUN:CLS:BEEP 2, 50, 250:BEEP 1, 21, 500: WAIT 0
2: PRINT"LIST PROGRAMS - Y/N"
3: Z$=INKEY$:IF Z$="" GOTO 2
4: IF Z$="N" GOTO 20
5: WAIT 150:PRINT"A:B.S.A"
6: PRINT"S:SWAN GANZ"
7: PRINT"D:IV DRUG DRIPS"
8: PRINT"G:RADFORD NOMOGRAM"
9: PRINT"H:H-L BYPASS"
10: PRINT"K:CLOCK"
11: PRINT"Z:VAPOUR PRESSURES"
12: PRINT"C:HEPARIN"
13: PRINT"V:SET VENTILATOR"
14: PRINT"L:LIQUID INJECTION"
20: END

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[Gene]

Thanks for finding all these sources of past info !

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(03-30-2024 01:50 PM)Gene Wrote:  Thanks for finding all these sources of past info !

Happy to contribute.

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