van Gent, P.K.

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S.A. TYDSKRIF VIR GENEESKUNDE 3910/F:e~alLoss1651MaternalDeathsoo163184Ca~esTotal .. 347 0 119 34booked cases who have not received proper antenatal care.J"he excellent results which have been published by Macafee,Stallworthy and others have only been obtained throughthorough care of the patient both outside and inside thehospital.Finally, one must again stress the danger of vaginalexamination in the patient's home. That this danger is stillnot fully recognized is shown by the number of patientsadmitted for antepartum haemorrhage who have beensubjected to vaginal examination before admission.REFERE CESI. Stabler, F. (1955): Brit. Med. l., 2, 290.2. Donald, 1. (1955): Practical Obsterrical Problems, p. 207. London: Uoyd-Luke Ltd.3. Macafee. C. H. G. (1945): J. Obste!. Gynaec. Brit. Emp., 52, 313.4. Stallworthy, J. (1951): Proc. Roy. Soc. Med., 44, 121.Booked CasesEmergency CasesTABLE 1. CASES OF A1'.'TEPARTUM HAEMORRJiAGE DEALT WITH 11956 BY THE MATERNITY lNSTlTUTlO S UNDER THE AEGIS OF THErYERSITY OF CAPE TOWNTotalFoetalLoss26939 Mei 19;59CONCLUSIONCaeSarean section is carried out in those rare cases whichdo not respond to this treatment. As the foetal mortalityis so high, many authorities also advise its use if the foetalheart is still audible-particularly if the patient is a primi-gravida and the cervix only slightly dilated. It is hopedthat with our recently acquired knowledge of fibrinogentherapy, Caesarean hysterectomy for persistent bleeding,even after the uterus has been emptied, may very rarely benecessary.In all cases of antepartum haemorrhage the third stagemust be conducted with great care, for further haemorrhageat this stage may be the last straw. In the severer cases ofaccidental haemorrhage one must, after delivery, still be onthe watch for serious renal damage, as evidenced by oliguria.The value of good antenatal care must again be emphasized,and the early admission to hospital of all cases of ante-partum haemorrhage cannot be over-emphasized.The figures at our maternity hospitals in Cape Town(Table n, and figures elsewhere, all show the far higherincidence and higher foetal and maternal mortality in un-BLOOD-ALCOHOL CALCULATIO S BY INSTRUMENTP. K. VAN GENT, M.Sc., D.ING., Division of Chemical Services, Port Elizabeth1BODY NUMBER .WEIGHT (lb.) ofTOTS(SPIRITS )120A 8130120140150160170190220210200i120150130160G140190180170200 180220210.. r If: "T-'=0··67 O' 75BODYWEIGHT (Ib.)176524~~212019181716.5.141312111098·4EfOUMBE.RofTOTS(SPIRITS ).170·400·390'38O· 37O' 360·350.340.330·32.310.300.290·280·270·260·250·240·23·22.21.200'160.15oALe OM OL %VI/VBLOOOFig. 17c45619181 1711615141312I11098150140130I·.180140 120150170160220210200220 190210 180200 170190 160• ,,::::. • r "=O' 50 O' 60In previous articles1,2 I explained a comparatively simpleformula by means of which it is possible to calculate thevolume of alcohol absorbed in a human body from bodyweight (lb.) and blood-alcohol % w/v. A formula ~uch asthis which, in reality, is a derivation of the internationallyacknowledged Widmark formula,3,4 is liable to encountercertain obstacles in a court of law. Under cross-examinationthe district surgeon might be asked to explain its derivationin detail, and this requires memorizing of the facts and theapplication of algebraic equation.Even the original Widmark formula requires manipulation,because the concentration of alcohol is stated as 'mg. alcoholper g. blood', while analytical reports give this concentrationas 'blood-alcohol % w/v', i.e. g. alcohol per 100 ml. blood.(mg. alcohol per g. blood= 10 x blood-alcohol % wIv,• 1'056where 1·056 equals the average S.G. of blood.)Closer consideration of Widmark's formula is necessaryin order to clarify some of its aspects. It states that thenumber of g. of alcohol in a body equals the body weightin kg. multiplied by the concentration of alcohol in theblood, expres~d as mg. alcohol/g. blood, multipliedby a factor 'r', i.e. the ratio between the concentration ofalcohol in the body to that in the whole blood.4 It is alsostated3 that 'r' is the ratio in weight between soft tissuesand body. Herein then lies the true medical function ofthis formula, because it is the responsibility of the districtsurgeon to decide what the value of the factor 'r' is to be.For purposes of calculation, 'r' is generally taken tobe 2/3 or 0.67.3,4 In his research Widmark' found that forspirits this factor in males varies between O· 60 and 0·76and in females between O· 50 and O· 60. If these Widmarkfactors are taken into consideration, it would seem more392 S.A. MEDJCAL JOURNAL 9 May 1959Fig. 2appropriate to use the following values for spirits whencalculations are made:'r'= 0·60 (males); 'r'= O· 50 femalesBy so doing one is assured that only the absolute minimumamount of alcohol consumed is accounted for. This pointof view is by no means novel, for it is actually suggestedby the British Medical Association. 5 (For ease of calcula-tion, the following values for 'r' were suggested by theGovernment Pathologist: minimum t, average i and maxi-mum -!; in other words, 0'50, 0·67 and 0'75).For the purpose of rapid calculation it was realized thatvarious values could be placed in tabular form, i.e. plottingblood-alcohol % w/v against body weight (lb.), with thehorizontal and perpendicular lines of intersection crossingeach other at values denoting absorbed alcohol in weight4or in volume.2 But this would provide no compromisebetween the use of a formula already established and onederived from the former. Moreover, a similar tabulationwould have to keep count with 4 values for 'r', viz. O' 50,0'60,0'67 and 0'75, and would require 4 tables.By means of a nomogram (Fig. 1), it is possible to· avoidthe use of these 4 tables. Here a straight line between blood-alcohol % w/v (scale D) and body weight (scales A, B, Fand G respectively for 'r' values of 0'50, 0,60, 0·67 and0'75) will intersect scale C or E, indicating the number oftots (spirits) consumed, i.e. alcohol absorbed by the bodytissues and expressed in tots. Consider the following ex-amples:'r'= 0·50 (scale A); blood-alcohol= O' 23 % wIv (scale D); bodyweight= 170 lb. This line intersects scale D at a value which isslightly less than 7 tots.'r'=0·67 (scale F); blood-alcohol=0·27% w/v (scale D); bodyweight= 150 lb. This line intersects scale E at a value which isslightly less than 10 tots.However, it will be realized that the use of a nomogramfor the purpose of rapid calculation required in a witnessbox, is not very satisfactory and hence it was decided toconstruct a simple instrument as shown in the photograph.Verdix CalclIlatorThe 'Verdix' calculator (Fig. 2) resembling a small sliderule, has a size of only 7 X I t inches. The top scale, denotingblood-alcohol % w/v, is calibrated from 0·15 to 0·40because it was found that a large portion of results from thechemical analysis of blood gave values between O' 20 % and0'30% alcohol, w/v. The bottom scale is especially cali-brated for South Mrican conditions, because a 'tot' islegally defined as one-quarter gill or li ft. OZ.6 and spiritsas having a minimum alcoholic strength of 250 under proofor approximately 43 % alcohol by volume.' Similarly alight beer such as Lager or Pilsener contains about 3· 5 % ofalcohol by volume.4 In other countries this calibrationwould have to be changed; e.g. in Great Britain a 'whisky',i.e. a tot of whisky, has a volume of approximately 5/6fl. OZ.5The centre, or sliding, scale is calibrated in lb. body-weight from 120 to 220, which should cover the weight ofmost individuals. This calibration can also be changed tokg. for countries where the decimal system is in use. Further-more the sliding scale has 4 arrows, each of which representsa different value for 'r'.The reverse of the calculator-not shown in the photo-graph (Fig. 2)-gives instructions for operating. Mentionis made of the numbered arrows, as well as of the alcoholicstrengths of spirits and beer.Operation is carried out by bringing body weight intoline with the value for blood-alcohol % w/v. The relevant'r' arrow will then on the bottom scale show the number oftots of spirits or pints of beer containing the same weightof alcohol as that absorbed by the body at the time when theblood sample was taken. In the photograph one sees 0·24%blood alcohol wIv, in line with 210 lb. body-weight. Bycalculation it was found that such a body would then haveabsorbed an amount of alcohol equivalent to that containedin slightly more than 12 tots (taking 'r' as O· 67) or 9 tots(taking 'r' as O· 50). The readings given by the 'Verdix'agree with these values.An instrument of this type need not necessarily be con-structed so as to resemble a slide rule; a model, thin enoughto be inconspicuous between the pages of a book, has beenmade of cardboard. The ideal construction would probablybe a hexagonally shaped metal rod, about the thicknessof a pencil, partly surrounded by a metal sleeve, with bothsleeve and rod appr-opriately calibrated.REFERENCESI. van Gent, P. K. (1957): S. Afr. Med. J., 31, 728.2. Idem (1957): Ibid., 31,1304.3. Bamford, F. (1947): Poisons, their Identification aJ1d Isolation, p. 39. London:Cburchill.4. Gordon, I., Turner, R. and Price, T. W. (953): Medica! Jurisprudence,PP.. 765 and 768. Edinburgh: LivingslOne.5. British Medical Association (1954): Report on Recognition of In!rJxication.6. Weights and Measures Act, o. 32 of 1922,· amendment (1943): Go,'!.otice 0.2048. Union Govt. Ga'7_. 12 ovemper.7. Wine, Spirits and Vinegar Act, No. 25 ,1957, ch. 2, sec. 8

Blood alcohol calculations by instrument

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Blood alcohol calculations by instrument

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