[Varicella vaccination in Germany. A provisional appraisal in the context of MMR vaccination]

In 2004, a general varicella immunization was introduced in Germany for infants from the age of 11 months, followed by the subsequent recommendation in 2009 of a second vaccine dose. The vaccination is carried out at the same time as the immunization against measles, mumps, and rubella (MMR). Results of the nationwide sentinel surveillance of varicella and herpes zoster implemented by the Varicella Working Group (Arbeitsgemeinschaft Varizellen, AGV) show that the defined goals for varicella immunization (reduction of varicella-related morbidity, complications and hospitalizations) have been reached within a few years owing to the advances in vaccine coverage. Although coverage rates for varicella have not yet reached the same levels as for MMR, varicella immunization seems to have benefited from the established MMR immunization schedule. Moreover, there is no evidence for an adverse effect on the use and acceptance of the MMR vaccine. Lessons learnt in measles epidemiology (such as trends in the incidence of the disease in adolescents and infants), as well as in the history of MMR recommendations, may be useful for the evaluation of future epidemiological changes with respect to varicella and herpes zoster. In view of a rapidly waning immunity against the varicella zoster virus after vaccination with one dose and the lifelong persistence of the virus, achieving a robust and sustainable immunity in the general population seems to be an ambitious goal. However, this accomplishment will be indispensable in preventing breakthrough infections and a shift of varicella to older ages and in avoiding an increase in herpes zoster incidence.

Estimating vaccination coverage in the absence of immunisation registers--the German experience

Immunisation registers are regarded as an appropriate solution to measure vaccination coverage on a population level. In Germany, a decentralised healthcare system and data protection regulations constrain such an approach. Moreover, shared responsibilities in the process of immunisation and multiple providers form the framework for public health interventions on vaccination issues. On the national level, those interventions consist mainly of conceptualising immunisation strategies, establishing vaccination programmes, and issuing recommendations. This paper provides an overview on sources and methods for collecting appropriate coverage data at national level and their public health relevance in Germany. Methods of data collection and available information on immunisations are described for three approaches: school entrance health examination, population surveys and insurance refund claim data. School entrance health examinations allow regional comparisons and estimation of trends for a specific cohort of children and for all recommended childhood vaccinations. Surveys deliver population based data on completeness and timeliness of selected vaccinations in populations defined by age or socio-demographic parameters and on knowledge and attitudes towards vaccination. Insurance refund claim data inform continuously on immunisation status (e.g. of children aged two years) or on vaccination incidence promptly after new or modified recommendations. In a complex healthcare system, the German National Public Health Institute (Robert Koch Institute, RKI) successfully compiles coverage data from different sources, which complement and validate one another. With the German approach of combining different data sources in the absence of immunisation registers, it is possible to gain solid and reliable data on the acceptance of vaccination programmes and target groups for immunisation. This approach might be of value for other countries with decentralised healthcare systems.

Potential benefits from currently available three pneumococcal vaccines for children--population-based evaluation

BACKGROUND

Currently there are 3 pneumococcal vaccines available in Germany. The aim of this study is to evaluate the potential of the three currently available pneumococcal vaccines to reduce the burden of invasive pneumococcal disease in children.

SUBJECTS

Children younger than 16 years who have been hospitalized because of IPD between July 2007 and June 2009 in a German pediatric hospitals.

METHOD

Surveillance of IPD in German pediatric hospitals and laboratories serving these hospitals. The case definition is isolation of Streptococcus pneumoniae from any normally sterile body site. The actual number of IPD cases is based on the capture recapture method combining information from both reporting systems.

RESULTS

In the study period an estimated yearly number of 164 IPD cases occurred among children younger than 2 years compared to 144 and 116 cases among children aged 2-4 years and 5-15 years. Among children under 2 years of age, 69 cases were caused by serotypes covered by PCV10 compared to 103 cases potentially preventable by PCV13. Among children aged 2-4 years 94 IPD cases were caused by serotypes covered by PCV13 compared to 108 cases covered by PPV23.

CONCLUSION

The newly available pneumococcal conjugate vaccines with better serotype coverage have the potential to further reduce IPD burden in Germany. The additional benefit of vaccination of children aged 2-4 years at high risk for pneumococcal infections with PPV23 is questionable.

Impact of the routine varicella vaccination programme on varicella epidemiology in Germany

Routine varicella vaccination with one dose for children of 11 to 14 months was recommended in Germany in 2004 to reduce disease incidence and severe complications. A country-wide varicella sentinel surveillance system was initiated in 2005 to detect trends of disease frequency and vaccine uptake and to evaluate the vaccination programme. A convenient sample of about 1,000 paediatricians and general practitioners was recruited to report on a monthly basis on varicella cases by age groups seen in their practice, and on varicella vaccine doses administered. Sentinel data from April 2005 to March 2009 show a reduction of 55% of varicella cases in all ages; 63% in the age group 0-4 years and 38% in 5-9-year-olds. The number of vaccine doses per reporting unit in all regions and physician groups increased during the same period. The number of reported cases as well as administered vaccines differed between physician groups and regions with different reimbursement policies. Where reimbursement was settled early and vaccine doses were increasing varicella cases started to decrease early as well. Besides reimbursement policies the availability and vaccination schedules influenced vaccine uptake. Sentinel surveillance provided valid data on trends for varicella associated morbidity, vaccine uptake and the age distribution of cases. The results confirm that following the introduction of routine varicella vaccination, varicella morbidity started to decline in Germany.

Spotlight on measles 2010: preliminary report of an ongoing measles outbreak in a subpopulation with low vaccination coverage in Berlin, Germany, January-March 2010

Since early January 2010, Berlin has been experiencing a measles outbreak with 62 cases as of 31 March. The index case acquired the infection in India. In recent years, measles incidence in Berlin has been lower than the German average and vaccination coverage in school children has increased since 2001. However, this outbreak involves schools and kindergartens with low vaccination coverage and parents with critical attitudes towards vaccination, which makes the implementation of public health interventions challenging.

Impact of the routine varicella vaccination programme on varicella epidemiology in Germany

Routine varicella vaccination with one dose for children of 11 to 14 months was recommended in Germany in 2004 to reduce disease incidence and severe complications. A country-wide varicella sentinel surveillance system was initiated in 2005 to detect trends of disease frequency and vaccine uptake and to evaluate the vaccination programme. A convenient sample of about 1,000 paediatricians and general practitioners was recruited to report on a monthly basis on varicella cases by age groups seen in their practice, and on varicella vaccine doses administered. Sentinel data from April 2005 to March 2009 show a reduction of 55% of varicella cases in all ages; 63% in the age group 0-4 years and 38% in 5-9 year-olds. The number of vaccine doses per reporting unit in all regions and physician groups increased during the same period. The number of reported cases as well as administered vaccines differed between physician groups and regions with different reimbursement policies. Where reimbursement was settled early and vaccine doses were increasing varicella cases started to decrease early as well. Besides reimbursement policies the availability and vaccination schedules influenced vaccine uptake. Sentinel surveillance provided valid data on trends for varicella associated morbidity, vaccine uptake and the age distribution of cases. The results confirm that following the introduction of routine varicella vaccination, varicella morbidity started to decline in Germany.

Spotlight on measles 2010: Preliminary report of an ongoing measles outbreak in a subpopulation with low vaccination coverage in Berlin, Germany, January-March 2010

Since early January 2010, Berlin has been experiencing a measles outbreak with 62 cases as of 31 March. The index case acquired the infection in India. In recent years, measles incidence in Berlin has been lower than the German average and vaccination coverage in school children has increased since 2001. However, this outbreak involves schools and kindergartens with low vaccination coverage and parents with critical attitudes towards vaccination, which makes the implementation of public health interventions challenging.

[Overview and assessment of available data sources to determine incidence of vaccine preventable diseases, vaccination coverage, and immune status in Germany]

The surveillance of vaccine preventable diseases and vaccination coverage is necessary in order to deliver epidemiological data with respect to national vaccination recommendations and control targets. The data available on the incidence of vaccine preventable diseases, vaccination coverage, and immune status of the population are fragmentary and do not allow the epidemiological situation to be fully assessed. Although the majority of vaccine preventable diseases are under surveillance nationwide (by statutory reporting or sentinel surveillance), data are not available for some diseases. In addition, data on vaccination coverage are not collected centrally. Nationwide data on vaccination coverage are only available for children at school entry. Use of secondary data such as data from health insurance companies or associations of statutory health insurance physicians provides an opportunity to close gaps in knowledge and to improve the surveillance of vaccine preventable diseases.

Comparative varicella vaccine effectiveness during outbreaks in day-care centres

BACKGROUND

Routine varicella vaccination for children >11 months was introduced in Germany in 2004 with three different vaccine brands available. In 2008 and 2009, we investigated seven varicella outbreaks in day-care centres (DCC).

METHODS

Varicella disease and vaccination status of 1084 children was reviewed to evaluate vaccination coverage (VC), brand-specific varicella vaccine effectiveness (VE), and risk factors of breakthrough varicella (BV, >42 days after vaccination). A case was defined as a child with acute onset of varicella attending one of the respective DCC at the time of outbreak. Children with a previous history of varicella, age<11 months, vaccinated at age<11 months or <42 days before disease onset or during the outbreak were excluded from VE and BV risk factors analyses (adjusted for gender, age and DCC).

FINDINGS

Of 631 children with available vaccination information, 392 (62%) were vaccinated at least once. Overall VE among 352 children eligible was 71% (95% confidence interval (CI) 57-81, p<0.001) and differed significantly by disease severity and number of doses administered. Risk for BV was higher for 1 dose of Varilrix (RR=2.8, 95%CI 1.0-7.8, p=0.05) or Priorix-Tetra (RR=2.4, 95%CI 0.7-8.3, p=0.18) but lower for 2 doses of Priorix-Tetra (RR=0.5, 95%CI 0.1-2.7, p=0.41) than for 1 dose of Varivax.

INTERPRETATION

Enhanced efforts to increase VC in Germany and 2 doses varicella vaccine might be successful to reduce the risk for BV. The evidence that VE and risk of BV are associated with vaccine brand needs further investigation.

An ongoing multi-state outbreak of measles linked to non-immune anthroposophic communities in Austria, Germany, and Norway, March-April 2008

From the second week of March 2008, public health authorities in the province of Salzburg observed an increased number of measles cases compared to previous years. Twenty cases of measles had been were notified Austria-wide in 2007, 24 in 2006, 10 in 2005, and 14 in 2004. The current outbreak has affected, as of 14 April, 202 people in Austria, 53 in Germany, and four in Norway, bringing the total number of cases related to this outbreak to 259. The initial case series investigation revealed that the common link was attendance of an anthroposophic school and day care centre in Salzburg city. The majority of the pupils were not vaccinated against measles.

Measles in south-west Germany imported from Switzerland - a preliminary outbreak description

Binary file ES_Abstracts_Final_ECDC.txt matches

An outbreak of measles in Lower Bavaria, Germany, January-June 2007

Between January and June 2007, a total of 90 cases of measles were notified in Passau and Rottal-Inn, two districts of Lower Bavaria in south-east Germany sharing a border with Austria.

Molecular epidemiology of penicillin-non-susceptible Streptococcus pneumoniae isolates from children with invasive pneumococcal disease in Germany

A population-based nationwide surveillance of antibiotic resistance associated with invasive pneumococcal disease (IPD) in children and adolescents (aged<16 years) was performed in Germany between 1997 and 2004. In total, 1517 isolates were collected, of which 5.1% and 1.1% were intermediately- or fully-resistant, respectively, to penicillin G. During the 8-year study period, an increase in resistance to both penicillin G and erythromycin A was observed, and the frequency of isolates exhibiting reduced susceptibility to penicillin G or erythromycin A increased from 1.4% and 11.1%, respectively, in 1997, to 8.7% and 29.0%, respectively, in 2004. Among the penicillin non-susceptible pneumococcal isolates, serotypes 14 (24.5% of isolates), 23F (16.0%) and 6B (16.0%) were found most frequently. Multilocus sequence typing of 58 (62%) penicillin G non-susceptible isolates revealed that sequence type (ST) 156 (Spain9V-3 clone) and its single-locus variant ST 557 were widespread in Germany. Moreover, 17 new penicillin G non-susceptible STs were defined for the first time. The study illustrated the genetic heterogeneity of antibiotic-resistant pneumococcal isolates in Germany.

Universal childhood immunisation with pneumococcal vaccine and meningococcal serogroup C vaccine introduced in Germany

In July 2006, vaccination against meningococcal C and pneumococcal disease was added to the routine childhood immunisation programme in Germany

Measles vaccination advised before travel to World Cup in Germany, but risk of measles infection low

The 2006 FIFA World Cup football tournament began in Germany on 9 June

Two outbreaks of measles in Germany 2005

Measles re-emerged in some counties in Germany in 2005, despite increasing vaccination coverage rates in children at school entry in recent years, which had led to decreasing incidence (with the lowest incidence ever recorded, 0.2 cases per 100 000 inhabitants in 2004). Regional outbreaks have been detected by the mandatory reporting system in the states of Hesse and Bavaria. Although both outbreaks led to similar incidences in the affected areas (14 and 12 cases respectively per 100 000 inhabitants) they differed in age distribution, transmission patterns and measles virus genotype. In Hesse, 223 cases were submitted, from which 160 belonged to 41 clusters mainly defined by family or household contacts. Attack rate was highest in children aged between 1-4 years (102 cases per 100 000). Results of measles virus diagnosis showed genotype D4 and identical nucleotide sequences for all analysed cases from Hesse. In Bavaria, 279 cases were submitted, most of which had occurred in schools and preschool facilities. Age-specific attack rate was highest in children aged between 5-9 years (129 per 100 000). Laboratory diagnosed viruses were identified as genotype D6 and were identical at the nucleotide level. In both outbreaks the vast majority of cases (95% in Hesse and 98% in Bavaria) were in unvaccinated children, but vaccination coverage differed in the affected areas and was slightly lower in Bavaria than in Hesse. Local accumulation of unvaccinated children and their concentration in schools and kindergarten preceded the outbreak in Bavaria. Despite high average vaccination coverage levels, local variations may lead to regionally limited outbreaks.

Two outbreaks of measles in Germany 2005

Measles re-emerged in some counties in Germany in 2005, despite increasing vaccination coverage rates in children at school entry in recent years, which had led to decreasing incidence (with the lowest incidence ever recorded, 0.2 cases per 100,000 inhabitants in 2004). Regional outbreaks have been detected by the mandatory reporting system in the states of Hesse and Bavaria. Although both outbreaks led to similar incidences in the affected areas (14 and 12 cases respectively per 100,000 inhabitants) they differed in age distribution, transmission patterns and measles virus genotype. In Hesse, 223 cases were submitted, from which 160 belonged to 41 clusters mainly defined by ,000). Results of measles virus diagnosis showed genotype D4 and identical nucleotide sequences for all analysed cases from Hesse. In Bavaria, 279 cases were submitted, most of which had occurred in schools and preschool facilities. Age-specific attack rate was highest in children aged between 5-9 years (129 per 100,000). Laboratory diagnosed viruses were identified as genotype D6 and were identical at the nucleotide level. In both outbreaks the vast majority of cases (95% in Hesse and 98% in Bavaria) were in unvaccinated children, but vaccination coverage differed in the affected areas and was slightly lower in Bavaria than in Hesse. Local accumulation of unvaccinated children and their concentration in schools and kindergarten preceded the outbreak in Bavaria. Despite high average vaccination coverage levels, local variations may lead to regionally limited outbreaks.

Die Bedeutung von Sentinels f�r die Implementierung und Evaluation von Impfstrategien

In sentinel surveillance a prearranged sample of reporting sources-often healthcare providers-agrees to report all cases of defined conditions. The German "Protection Against Infection Act" (IfSG) provides a mandate to the Robert Koch-Institute (RKI) to establish sentinel surveillance of not notifiable diseases relevant to public health. Sentinel systems with RKI involvement include two networks of private practitioners reporting cases of influenza and measles (within the Working Groups on Influenza and Measles, respectively). In addition a laboratory-based sentinel system reports cases of certain bacterial infections in children. Results from these systems serve as a basis for framing vaccination recommendations and goals as well as for the evaluation, adjustment and promotion of vaccination strategies. The data indicate time trends (e. g. number of cases by season, age and region) and supply specific information (e. g. for determination of risk factors, distribution of pathogens). Methodological problems of sentinel surveys (e. g. selection of appropriate samples, population-based estimates) can be accounted for with appropriate methods of analysis. More effective implementation of sentinel surveillance in Germany could be achieved through better coordination of existing structures. This would make more effective use of limited resources and better enable timely and flexible investigation of conceptual and organisational questions.

Measles outbreaks in Germany

Since November 2001, as in the previous year, several outbreaks of measles have been reported to the German notification system for infectious diseases. These outbreaks have been reported from the states of Bavaria, Lower Saxony, and North Rhine Westphalia.

[Surveillance of measles in Germany]

In Germany, as in the entire WHO Region Europe, the goal has been set to eliminate measles by the year 2007. In order to achieve this, high vaccination rates of >/= 95 % are necessary as well as an intensive surveillance consisting of a continuous record of the age and region-specific incidence, vaccination rates and the seroprevalence. Data on the vaccination status, recorded in the districts at the time of school entry, are collected centrally and evaluated at the RKI since 1998. The vaccination rate for the 1(st) dose against measles is on the average 84.6 % and for the 2(nd) dose 14.3 %. A nationwide sentinel established in 1999 with over 1200 medical practitioners permits an estimate of the country-wide measles incidence on the basis of the registered measles cases. Results from the year 2000 showed a very big difference between the old Federal States (mean incidence of 46.8 illness per 100 000) and the new Federal States (0.9 per 100 000). Most of those falling sick were unvaccinated (85.4 %), where 35 % refused the vaccination. Thirty-nine percent of the cases were examined in the laboratory and from these 58 % were clinically confirmed; 10 % of the cases occurred in those receiving one dose of vaccine and none in those receiving 2 doses. The age peak of the sick children was between 1 to 4 years of age. Measles notification is obligatory in Germany since January 2001. From these data, the incidence of the 1(st) quarter has been calculated. It varies widely depending on the State (e. g. Bavaria 5.7 / 100.000 vs < 0.5 % in new Federal States). The seroprevalance studies conducted in 1993 and in 1995/96 show large gaps in immunity of small children and suggests that the MMR vaccination may have been carried out too late. The elimination of measles in Germany can only be achieved if the vaccination rates are increased and the 1(st) MMR vaccination is performed as early as possible. In particular, the vaccination rates for the 2(nd) dose are inadequate to be able to reach those with vaccine failures in a greater proportion and to close the gaps of vaccination.

Haemophilus influenzae type b disease: impact and effectiveness of diphtheria-tetanus toxoids-acellular pertussis (-inactivated poliovirus)/H. influenzae type b combination vaccines

BACKGROUND

Since 1996 in Germany primary infant immunization against Haemophilus influenzae has been most commonly given in the form of diphtheria-tetanus toxoids-acellular pertussis/H. influenzae type b (DTaP/Hib) or diphtheria-tetanus toxoids-acellular pertussis (-inactivated poliovirus)/H. influenzae type b (DTaP-IPV/Hib) combination vaccines. These combination vaccines elicit lower anti-Hib antibody concentrations than the equivalent Hib conjugate administered as a separate injection, but the clinical relevance of this phenomenon is unknown.

METHODS AND FINDINGS

To assess the impact of DTaP/Hib combination vaccines on the incidence of invasive Hib disease in Germany, two independent surveillance systems, one hospital- and one laboratory-based, were used during 1998 and 1999 for detection of cases. Vaccination histories of all cases detected were obtained by telephone contact with parents or health care providers. During the 2-year study period invasive H. influenzae disease in the <5-year age group continued to fall, with a mean annual incidence of 1.01/100 000 children. National vaccination coverage rates revealed that only 70% of children given DTaP/Hib or DTaP-IPV/Hib received the recommended three doses in their first year of life, but the overall effectiveness of these vaccines was high at 97.5% (95% confidence interval, 96.3 to 98.4) for those who had received at least one dose. In subjects who received the full 3-dose schedule, effectiveness was 98.8% (95% confidence interval, 98.2 to 99.3).

CONCLUSION

Although it is well-documented that DTaP/Hib vaccines elicit lower anti-Hib titers than separate vaccines, such combinations are effective in reducing the incidence of invasive H. influenzae type b disease.

Epidemiology of pneumococcal disease in children in Germany

Recently published and as yet unpublished data allow a reasonable estimate of the annual burden of pneumococcal disease in Germany. At least 277,000 episodes of otitis media and at least 2,000 episodes of sinusitis occur in children under the age of 5 y. Pneumococcal meningitis was found in 200 children under the age of 16 y; the estimate for all age groups ranges from 450 to 1100 cases. Of approximately 150,000 cases of ambulatory pneumococcal pneumonia, at least 63,000-105,000 patients are hospitalized each year.

CONCLUSION

Further studies of pneumococcal epidemiology in Germany are needed, and continued surveillance will be necessary for a better understanding of the overall burden of pneumococcal disease in children as well as adults.

Proportion of invasive pneumococcal infections in German children preventable by pneumococcal conjugate vaccines

The incidence and serotype distribution of Streptococcus pneumoniae as a cause of invasive diseases are unknown with regard to most European countries. From January 1997 through December 1998, population-based nationwide prospective surveillance was undertaken for invasive pneumococcal disease (IPD) in children in Germany, based on monthly independent reports from all pediatric hospitals and from clinical microbiology laboratories. On the basis of 896 reported IPD cases (including 404 with meningitis), the incidences per 10(5) children in different age groups were as follows: children aged <1 year, 18.9 (9.7 for meningitis); children aged <2 years, 16. 0 (7.2 for meningitis); for children aged <5 years, 8.9 (3.9 for meningitis); and for children aged <16 years, 3.2 (1.4 for meningitis). The proportions of cases involving strains (304 serotyped) included in conjugate vaccines were as follows: for the 7-valent vaccine, 52%; for the 9-valent, 62%; and for the 11-valent, 71%. None of the isolates were resistant to penicillin or cefotaxime. Although the rate for meningitis is similar, other manifestations of IPD are less commonly diagnosed in Germany than in other countries. The serotype distribution only partially matched that used in the recent development of pneumococcal conjugate vaccines.

Anonymous unlinked testing as a sentinel approach: experience in Germany

STUDY OBJECTIVE

To establish a laboratory sentinel as a supplementary instrument for monitoring the seroprevalence of HIV among childbearing women as a proxy to the heterosexually active population.

DESIGN/SETTING

Anonymous unlinked testing of neonatal dried blood spots has been performed in central laboratories of three federal states since 1993. The survey uses residual dried blood spots collected on Guthrie cards for screening of infants for metabolic disorders. These are eluted and tested for HIV antibodies. Data retained with the specimen are only district of residence along with year and month of birth.

PARTICIPANTS

Because maternal IgG crosses the placenta before birth, the presence of antibodies in newborns reflects the infection status of the mother. Childbearing women are fairly representative for the heterosexually active general population.

MAIN RESULTS

The observed HIV prevalence in childbearing women of less than 1 per thousand confirms the assumption of a low rate of HIV infection in the general population. Significant time trends could not be detected, but HIV prevalence was higher in metropolitan compared with rural areas.

CONCLUSIONS

Laboratory sentinels in general and the anonymous unlinked testing of neonatal dried blood spots in particular can supply additional information on HIV seroprevalence. This surveillance system could be expanded to utilise residual samples of other sources as well as to monitor the immunity against specific vaccine preventable diseases and other infectious diseases of public health relevance.

Perioperative platelet reactivity and the effects of clonidine

BACKGROUND

Increased postoperative platelet reactivity may contribute to arterial thrombotic complications following surgery. alpha 2 Agonists, which are being used increasingly to blunt the stress response of surgery, increase platelet aggregation in vitro. We compared perioperative changes in platelet reactivity in 21 patients receiving either clonidine or placebo.

METHODS

Patients undergoing major abdominal surgery were randomized to receive oral and transdermal clonidine (n = 11) or placebo (n = 10). All patients received similar perioperative management, including preoperative sedation, general anesthesia without neuraxial opioids, or local anesthetics and postoperative patient-controlled intravenous morphine. Blood was obtained for measurement of clonidine level, fibrinogen concentration, platelet count, and platelet reactivity (impedance aggregometry and dense granule release) before induction and 24, 48, and 72 h postoperatively.

RESULTS

Thirteen of the 21 patients had biopsy-proven cancer at surgery, 5 of 11 received clonidine and 8 of 10 received placebo (NS). Clonidine levels were therapeutic (1-2 ng/ml) throughout the study period. Clonidine administration had no effect on platelet count or platelet reactivity. Therefore, the groups were combined for further analysis. In this group (n = 21), compared to preoperative values, fibrinogen levels rose maximally (36%) at 72 h postoperatively and platelet counts decreased 22% at 48 h. Platelet reactivity (aggregation and degranulation) to collagen, adenosine diphosphate, arachidonic acid, and ristocetin, increased at 24, 48, and 72 h postoperatively. Thrombin-induced (supramaximal stimulus) dense granule release did not change from preoperative values.

CONCLUSIONS

These data indicate that major abdominal surgery causes increased platelet reactivity postoperatively but does not effect maximal degranulation. This increased platelet reactivity occurs within 48 h of surgery, coinciding with the peak incidence of postoperative arterial thrombotic complications. Clonidine administration has no effect on surgically induced changes in platelet reactivity. In this surgical patient population, the use of clonidine should not increase the risk of platelet-induced perioperative arterial thrombosis.