Frequency Analysis of Ventricular Fibrillation and Resuscitation Success

SUMMARY In 56 patients, frequency analysis of the electrocardiogramof ventricular fibrillation exhibited power spectra with a distinctdominant frequency. The greatest success for resuscitation fromventricular fibrillation is recorded when ventricular fibrillationdevelops after the patient comes under coronary care. Of the41 patients in whom the onset and first 8 s of ventricular fibrillationwere artefact-free the mean dominant frequency of primary ventricularfibrillation (no cardiogenic shock or cardiac failure) in 21patients was 6.2±0.2 Hz, significantly higher than themean dominant frequency of the first 8 s of secondary ventricularfibrillation (cardiogenic shock or heart failure) (4.0±0.2Hz, 20 patients, p =0.0001). In these patients the peak-to-troughamplitude (ECG) of the first 8 s of ventricular fibrillationwas similar in both primary and secondary ventricular fibrillationas was the mean duration of ventricular fibrillation prior tothe first DC shock. There was a significantly lower successrate for resuscitation from secondary ventricular fibrillation(6 of 20 patients) compared with resuscitation from primaryventricular fibrillation (18 of 21 patients, x² 17.8, p=0.001).Of the remaining 15 patients who were collapsed between 3 and20 min before the arrival of the mobile coronary care unit,the dominant frequency of the first 8 s of ventricular fibrillationfell with increased duration of collapse (from 5.5 Hz at 3 minto a mean of 2.1 Hz at 20 min). Four of these 15 patients whosurvived the initial arrest had a mean dominant frequency of5.2±0.3 Hz, which was significantly higher than the meandominant frequency (3.1±0.3 Hz, p<0.01) of the 11patients who were not resuscitated. This study shows that low frequency ventricular fibrillationis indicative of a poor chance of successful resuscitation.Alteration of the frequency may increase resuscitation success.     

Impact of an infection consultation service for bacteraemia on clinical management and use of resources

Since 1993, the infection consultation service for bacteraemia has seen 310 patients in the Medical and Surgical Directorates at Ninewells Hospital and Kings Cross Hospital. A random sample of 100 was audited. Case-notes were incomplete for five patients, leaving 95 fully-audited patients. Clinical outcome measures were death from infection, and readmission within 2 weeks of discharge. Initial treatment was inconsistent with antibiotic policy in 46 patients (48%). Antibiotic treatment was changed in 37 (80%) of these patients: increased in intensity in 19 (41%) and decreased in 18 (39%). Changes were also made in 30 (61%) of the 49 patients whose initial treatment was consistent with sepsis policy-increased in seven (14%) and decreased in 23 (47%). Median daily antibiotic costs were lowered in patients whose initial treatment was consistent with sepsis policy (pounds 10.10 vs. pounds 7.28, p = 0.0274). However, in the other patients, savings were balanced by increases (p = 0.7696). Consultation required one consultant session per week (3.5 h) and the audit required an additional 16 consultant sessions. Seven patients died, but only one death was directly related to infection. Six patients were readmitted to hospital within 2 weeks, in three due to recurrence of infection. Changes to treatment were recommended in the majority of patients, regardless of whether initial treatment complied with the sepsis policy. The service primarily redistributed resources rather than reducing costs. A fully audited service requires considerable consultant time, but we believe such time is well spent.      

How much would the safety of blood transfusion be improved by including p24 antigen in the battery of tests?

BACKGROUND: Because p24 antigen may be detectable during seroconversion, before antibodies, some of the infected blood undetected by antibody screening could be identified through antigen screening. STUDY DESIGN AND METHODS: The potential benefit of antigen screening was evaluated in a simulation model incorporating present knowledge of the time sequence from antigen exposure to antibody development during seroconversion and the incidence of seroconversion among repeat donors. The model was designed so that the results were consistent with the observed rate of antibody-positive blood donations and the CIs of surveys that did not find any antibody-negative/antigen- positive donated blood. RESULTS: In the United States in 1990, the number of expected, undetected, contaminated blood components was estimated at 68; of these 8 to 17 could have been identified by antigen screening, depending on the hypothesis explored. (In 1992, 20 undetected, contaminated blood components were expected according to this model, of which 2 to 5 could have been identified by antigen screening.) In France, the comparable figures were 1 to 4 of 13 in 1990 and 1 to 2 of 7 in 1992. CONCLUSION: The projected benefit must be weighted against possible negative consequences, including 1) an increase in recently infected persons seeking p24 antigen screening at blood banks (assuming this test is not incorporated into screening in non-blood bank settings) and 2) the need for additional quality assurance procedures to avoid operational flaws associated with the increase in the donor screening test battery. In any case, the best way of increasing the safety of blood is improvement in the selection of donors, which can diminish the residual risk of transmission of any viruses.     

Polycystic Kidney Disease Re-evaluated: A Population-based Study

A genetic register of all known cases of autosomal dominantpolycystic kidney disease occurring in South and Mid-Wales hasbeen established. In a population of 2.1 million, 209 familieswith affected members were identified, 303 of whom are currentlyalive, 70 on renal replacement therapy. An additional 551 caseswould be predicted amongst family members at 50 per cent and25 per cent risk, giving an apparent prevalence of 1:2459 inthe general population. Five possible new mutations were seenwhere adults with phenotypic autosomal dominant polycystic kidneydisease had both parents alive, age > 55 years with no cystsvisible on ultrasound. The take-on rate for renal replacementtherapy increased during 1970–79 but has apparently reacheda plateau of 4.8 cases per million population per year overthe last 8 years, despite a rapidly increasing acceptance ofuraemic patients as a whole (72/10⁶/year in 1988–89).Considerably more patients with autosomal dominant polycystickidney disease aged over 50 years were started on treatmentin 1980–89 than in 1970–79, but the survival overallimproved with time. All cases of autosomal dominant polycystickidney disease reaching end-stage renal disease are now beingtreated, but the apparent clinical prevalence of this conditionin our region is less than half the supposed gene frequency,suggesting that undiagnosed cases have a benign prognosis.     

National Comparative Audit of Blood Use in Elective Primary Unilateral Total Hip Replacement Surgery in the UK

INTRODUCTION

Blood is a scarce and expensive product. Although it may be life-saving, in recent years there has been an increased emphasis on the potential hazards of transfusion as well as evidence supporting the use of lower transfusion thresholds. Orthopaedic surgery accounts for some 10% of transfused red blood cells and evidence suggests that there is considerable variation in transfusion practice.

PATIENTS AND METHODS

NHS Blood and Transplant, in collaboration with the Royal College of Physicians, undertook a national audit on transfusion practice. Each hospital was asked to provide information relating to 40 consecutive patients undergoing elective, primary unilateral total hip replacement surgery. The results were compared to indicators and standards.

RESULTS

Information was analysed relating to 7465 operations performed in 223 hospitals. Almost all hospitals had a system for referring abnormal pre-operative blood results to a doctor and 73% performed a group-and-save rather than a cross-match before surgery. Of hospitals, 47% had a transfusion policy. In 73%, the policy recommended a transfusion threshold at a haemoglobin concentration of 8 g/dl or less. There was a wide variation in transfusion rate among hospitals. Of patients, 15% had a haemoglobin concentration less than 12 g/dl recorded in the 28 days before surgery and 57% of these patients were transfused compared to 20% with higher pre-operative values. Of those who were transfused, 7% were given a single unit and 67% two units. Of patients transfused two or more units during days 1–14 after surgery, 65% had a post transfusion haemoglobin concentration of 10 g/dl or more.

CONCLUSIONS

Pre-operative anaemia, lack of availability of transfusion protocols and use of different thresholds for transfusion may have contributed to the wide variation in transfusion rate. Effective measures to identify and correct pre-operative anaemia may decrease the need for transfusion. A consistent, evidence-based, transfusion threshold should be used and transfusion of more than one unit should only be given if essential to maintain haemoglobin concentrations above this threshold.     

Gestalt Perception and Local-Global Processing in High-Functioning Autism

This study examined gestalt perception in high-functioning autism (HFA) and its relation to tasks indicative of local visual processing. Data on of gestalt perception, visual illusions (VI), hierarchical letters (HL), Block Design (BD) and the Embedded Figures Test (EFT) were collected in adult males with HFA, schizophrenia, depression and normative controls. Individuals with HFA processed gestalt stimuli less in accord with gestalt laws, particularly regarding the principle of similarity. Gestalt processing correlated positively with global processing of the HL. EFT and BD performance correlated negatively with VI susceptibility in HFA. All clinical groups succumbed less to VI than the normative sample. Results suggest decreased gestalt perception in HFA, being associated with a more general local visual processing bias.