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As discussed in the hazard characterization symptoms 7 days before period prochlorperazine 5 mg fast delivery, the exponential model was selected to describe the relationship between the dose of L medications ok to take while breastfeeding prochlorperazine 5mg amex. Dose-response curves were developed for both the healthy 136 Risk characterization: response to Codex questions population and the susceptible population and include the entire range of ingested doses medicine used to treat chlamydia cheap 5mg prochlorperazine free shipping. These curves are population based and describe the average dose-response relationship medicine 852 cheap prochlorperazine 5 mg. A specific outbreak that involves a strain with high virulence or an unusually susceptible population may still result in a significant number of cases from food containing comparatively low numbers of L. For the purposes of this example, only the dose-response curve for the susceptible population was used, and it was assumed that all cases of listeriosis were restricted to that population. The specific dose-response curve selected was the one where the maximum level to which L. The end result of these assumptions is that the most "conservative" dose-response model was used, i. By substituting different values for n, the likelihood of listeriosis at levels between 0. The overall affect on the number of cases of listeriosis was estimated by multiplying the likelihood of listeriosis per serving by the total number of servings. As a simple, worst-case scenario, the predicted risk per serving and predicted number of annual listeriosis cases were estimated by assuming that all 6. The effects on the incidence of listeriosis of six levels of pathogen were evaluated (0. The predicted annual numbers of listeriosis cases were calculated and summed, and the predicted number of cases for each maximum level is given in Table 5. While either set of predictions can be challenged on the basis of the assumptions used, such scenarios are useful in framing the extent of the risk likely to be encountered. In interpreting these results and in attempting to predict the actual effect of a change in the regulatory limits for L. The current example is based on data from the United States of America, where the current allowable limit for L. However, the baseline level for the United States of America population was 2130 cases (Mead et al. As a means of further examining this concept, a simple hypothetical "what-if" scenario was developed based on the information provided in Tables 5. As a means of simplifying the what-if scenario and dramatizing the impact of compliance, a single Risk Assessment of L. Conversely, if a serving of food was out of compliance, it was assumed to have a set level of L. The predicted number of cases as a function of the percentage of defective servings is provided in Table 5. As expected, the number of predicted cases increases with an increasing frequency of defective servings. A more detailed consideration of compliance could be achieved by incorporation of distributions reflecting the levels of L. However, such a detailed consideration of compliance rates was beyond the scope of the current risk assessment. Furthermore, the simple hypothetical what-if scenario presented adequately demonstrates key concepts related to how compliance rates can strongly influence the actual risk associated with a microbiological criterion. The what-if scenario also demonstrates the concept that a less stringent microbiological limit could lead to an improvement in public health if new criteria lead to a substantive decrease in defect rates. Thus, the current risk assessment had to develop de novo a means for addressing the request. The basic approach taken to developing the requested dose-response relations was to take advantage of epidemiological estimates of the relative rates of listeriosis for different subpopulations. These "relative susceptibility" values were generated by taking the total number of listeriosis cases for a subpopulation and dividing it by the estimated number of people in the total population that have that condition. Relating the relative susceptibility values to the dose-response relations for the different subpopulations requires a means of converting these point estimates to a dose-response curve. Being a single parameter model, the exponential model allows the entire dose-response curve to be generated once any point on the curve is known. Thus, the r-value for an exponential doseresponse curve can be estimated for a subpopulation using a relative susceptibility ratio and a reference r-value for the general population. Using the relative susceptibility value for cancer patients as an example (Table 5. Using the above equation, the r-values for different classes of patients were estimated based on epidemiological data from France (Tables 5. Relative susceptibilities for the different subpopulations are based on the incidence of listeriosis cases (outbreak and sporadic) in these groups in 1992. Relative susceptibilities for the different sub-populations are based on the incidences of listeriosis cases (outbreak and sporadic) in these groups. Condition Perinatal Elderly (60 years and older) Intermediate-age population (reference population) Relative susceptibility 14 2. The most compromised group in the French data, transplant patients, has an r-value approximately 4 orders of magnitude greater than the reference population. The relative susceptibility values for the elderly population showed close agreement, 7. The differences reflect, in part, the different definitions of the age corresponding to the category "elderly" and the reference population. The United States of America intermediate-age population includes the patients that are separated out from the less-than-65-years-of-age group in the French data and the two reference populations are not expected, therefore, to have the same r-values. Nevertheless, the two tables indicate the magnitude of the impact that the impairment of the immune system by the specific conditions and disease states has on susceptibility to listeriosis. The r-value for the Los Angeles outbreak in pregnant women from consumption of Hispanic cheese was very close to that estimated (Table 5. The r-value for the Finland outbreak from butter in hospitalized transplant patients differed from the values based on transplant patients by 1000fold (Table 5. This may have resulted from the smaller number of individuals exposed, the extremely compromised and highly variable immunological status of the population, or the involvement of a highly virulent strain of L. There is a clear need in future outbreaks for exposure levels, immune status of the patients and strain characteristics to all be investigated so that these dose-response models can be further refined and validated. Additional factors that affect the risk associated with any food, regardless of whether it does or does not support L. This question suggests a number of alternative approaches to a simple growth/no-growth evaluation, such as a consideration of the effect on consumer risk of limiting the storage temperature and shelf-life of a product that supports the growth of L. The risk assessment team has attempted to also consider these approaches while formulating its answer to the question. Also, as noted previously, it is clear that an increase in the total numbers of L. Furthermore, as bacterial growth is exponential, the risk might be expected to increase exponentially with storage time. Three approaches for answering this question are provided: (i) (ii) (iii) general consideration of the impact of the ingested dose on the risk of listeriosis; comparison of four foods that were selected, in part, to evaluate the effect of growth on risk; and comparison of what-if scenarios for the foods evaluated that do support L. These include product formulation, storage time and temperature, and interactions with other microorganisms present in the product. In vacuumpacked foods, lactic acid bacteria can reach stationary phase without causing product spoilage. For every three generations of growth, there is 144 Risk characterization: response to Codex questions approximately a 10-fold increase in the bacterial population. Combinations of suboptimal levels reduce the growth rate and can prevent growth at less extreme conditions than any of these factors acting alone. For example, fresh cut vegetables have a relatively short shelf-life and do not support as rapid growth of L. Thus, it would be expected that extent of growth in fresh cut vegetables would not be as great as those in other foods, resulting in a lower risk for given initial contamination rates and levels. The actual calculation of risk would also have to consider that different servings would be consumed at various times within the total product shelf-life, as typically only a small fraction of a product is consumed near the end of its declared shelflife.
The basis of uncertainty is twofold: information uncertainty and model uncertainty symptoms xanax withdrawal 5mg prochlorperazine with amex. Population characteristics must be inferred from observations made on a sample drawn from the population at a specific point in time ombrello glass treatment order prochlorperazine 5 mg free shipping, and observed phenomena must be extrapolated to the situation under study medicine bag order prochlorperazine 5 mg with mastercard. The assumptions on which the exposure estimates are based introduce uncertainty: simplification of complex processes into mathematical models for physical processes symptoms dizziness nausea buy prochlorperazine 5mg lowest price, inactivation and growth introduce uncertainty; small sets of scenarios are generalized to all scenarios of importance; and assumptions are made about how recognizable components of processes operate. Variability is an inherent property of all physical, chemical and biological systems. There is natural variability (heterogeneity) among the constituents of a population. In the case of the current risk assessment there are multiple factors influencing risk that each have inherent variability. Green vegetables or berry crops might be affected by contamination from soil, manure, irrigation, silage and the pathogens in them, for example. At each of the succeeding stages of production, changes in prevalence and concentration are likely to occur. However, unless actual measurements are taken at each these stages, they must be modelled based on the knowledge that already exists. Some of these steps increase, but most decrease, the prevalence and concentration of pathogens. Slicing operations appear to be common sources of re-contamination of cooked products. This can lead to an apparent increase in the frequency of contamination if the product was initially contaminated at a level below the limit of detection of the method used to enumerate L. The prevalence and levels of a pathogen may change through recontamination from portioning of the opened packaged products through slicing, chopping and then repackaging. Ambient temperatures can permit the growth of the pathogen on contaminated slicing equipment, cutting boards, etc. In the case of the current risk assessment, retail data were employed in conjunction with predictive microbiology models and data on storage times and temperatures to predict the levels ingested. The degree to which growth and inactivation occur is governed by the composition of the food, the conditions under which the food is stored or subject, and the time during which those different conditions apply. Conversely, heat treatments can effectively eliminate the microorganism in a matter of minutes. Consequently, if growth is possible in the product, the predicted risk resulting from that growth generally changes exponentially with time. Since predictive microbiology plays such an important role in the current microbiological risk assessment, it is important that the application of predictive microbiology methods and its limitations are well understood by risk assessors, stakeholders and risk managers. A review of predictive microbiology concepts and limitations, methods of assessing predictive model performance, and techniques for the application of predictive models in risk assessment is given is Appendix 3, including a compendium of published predictive models for L. The current section presents patterns of microbial behaviour in foods and food processing, and identifies unifying principles to aid understanding of the factors that affect the ecology of L. The following material is based on Ross, Baranyi and McMeekin (1999) and Ross, Dalgaard and Tienungoon (2000) who reviewed the microbial ecology of L. These limits are not absolute, however, as discussed below, but represent the widest range of that factor when all other factors are optimal for growth. When several factors are suboptimal for growth, the ranges of each that will permit growth of L. This is the basis of the Hurdle Concept, or "multiple barrier methods" in food preservation. While slightly elevated salt concentration may inhibit growth rate, it has also been reported to increase the high-temperature tolerance of many bacterial species, though the effect is not universal (Gould, 1989). In this context, yield is taken to represent the maximum cell biomass produced in a given (batch) environment. Many of these factors act independently and can be understood in terms of the relative inhibition of growth rate due to each factor. Under completely optimal conditions, each microbial strain has a unique maximum growth rate. As any environmental factor becomes less optimal, the growth rate declines in a predictable manner. The cumulative effect of many factors at suboptimal levels can be estimated by multiplying the relative inhibitory effect of each factor. The relative inhibitory effect can be determined from the "distance" between the optimal level of the factor and the minimum (or maximum) level that completely inhibits growth. This concept is embodied in the structure of a number of the square-root type models (Ratkowsksy et al. The inhibitory effect of organic acid is almost completely determined by the concentration of the undissociated form of the acid. The concentration of undissociated form can be readily calculated from the total concentration of the organic acid and the pH. If the inhibitory activity of organic acids is described in terms of the undissociated form of the acid the simple multiplicative rule (as described above) works well, as illustrated by Presser, Ross and Ratkowsky (1998) and by Tienungoon (1998) for L. The relative inhibition of a specific concentration of nitrite is equivalent at all experimental conditions of pH, temperature and water activity. That inhibition is approximately linearly related to the total nitrite concentration. Growth rate may also be affected by the presence of high levels of other microorganisms, in a phenomenon described as the "Jameson effect" by Stephens et al. Jameson (1962), in studies concerning the growth of Salmonella, reported the suppression of growth of 2. The same effect has been reported for Staphylococcus aureus in seafood (Ross and McMeekin, 1991), L. Strain L5; growth in the absence of lactic acid, and growth and no growth (+) in the presence of 50 mM lactic acid. Similar behaviour as a function of water activity, pH and lactic acid in broths was described by Tienungoon (1998). As pH decreased, or lactic acid concentration increased, or both, the final cell density began to be reduced at progressively higher water activities, suggesting that multiple hurdles to growth reduce the maximum population density. Hudson, 1993), which is usually ill-defined or unknown, affecting the duration of the lag time. The latter rate is presumed to respond to the environment in the same way, relatively, as generation time, i. Generally, the effect is more pronounced when cells are shifted away from optimal conditions rather than towards conditions more optimal for growth. Augustin and Carlier (2000a) presented similar information expressed as Risk Assessment of L. It has also been proposed that lag times may be a function of the concentration of cells present, with fewer cells leading to longer lag times (Zhao, Montville and Schaffner, 2000; Robinson et al. This may reflect the probability of a cell being ready to grow; with more cells present, it is more likely that at least one cell will have a short lag. The integration into a conceptual model of factors that may affect the rate and amount of growth of L. Inactivation has traditionally been considered to follow log-linear kinetics, characterized by D and z-values (see next section), although the actual kinetics may be complex and involve several distinct phases, each with its own log-linear rate (Cerf, 1977; Augustin, Carlier and Rozier, 1998; Humpheson et al. Until recently, D and z values were the primary methods of modelling thermal inactivation of microorganisms. Recent reports indicate that log-linear models are inadequate to describe the death kinetics of L.
There is no other preventive strategy for this cancer that can substitute for vaccination symptoms of dehydration order prochlorperazine 5 mg online. In maximal and enhanced resource settings: For which cohorts is routine vaccination recommended in maximal and enhanced resource settings Recommendation A1b Public health authorities may set the upper end of the target population higher than 14 years of age medicine assistance programs order prochlorperazine 5mg on-line, depending on local policies and resources (Type of recommendation: evidence based; Evidence quality: low; Strength of recommendation: moderate) medications epilepsy buy prochlorperazine 5mg without prescription. What numbers of doses and intervals are recommended in maximal and enhanced resource settings Recommendation A2a For girls 9 to 14 years of age who are immune competent medicine x ed generic prochlorperazine 5mg mastercard, a two-dose regimen is recommended (Type of recommendation: evidence based; Evidence quality: intermediate; Strength of recommendation: moderate). Recommendation A2b the interval between two doses should be at least 6 months and may be up to 12 to 15 months (6 months: Type of recommendation: evidence based; Evidence quality: high; Strength of recommendation: strong. Recommendation A2c Girls age > 15 years at the time of the first dose or initiation (outside of target population) who receive vaccine should receive three doses (Type: informal consensus-based; Evidence quality: intermediate; Strength of recommendation: moderate). For prevention of cervical cancer in maximal or enhanced resource settings where vaccine coverage of girls is > 50%, vaccination of boys is not recommended (Type of recommendation: evidence based; Evidence quality: insufficient; Strength of recommendation: weak). In limited resource settings: For which cohorts is routine vaccination recommended in limited resource settings Recommendation B2a For girls starting at 9 years of age who are immune competent, a two-dose regimen is recommended (Type of recommendation: evidence based; Evidence quality: intermediate; Strength of recommendation: moderate). Recommendation B2b the interval between the doses should be at least 6 months and may be up to 12 to 15 months (6 months: Type of recommendation: evidence based; Evidence for quality: high; Strength of recommendation: strong. Recommendation B3 If there are sufficient resources remaining after vaccinating high-priority populations with an adequate target (minimum recommended coverage is > 50% with two doses, with a target of 80%),53 for females who have received one dose and are age. For prevention of cervical cancer, if there is low vaccine coverage of the priority female target population (, 50%) in limited resource settings, vaccination may be extended to boys (Type of recommendation: evidence based; Evidence quality: intermediate; Strength of recommendation: moderate). Extending vaccination to boys to prevent cervical cancer is not cost effective, unless there is low vaccine coverage of the priority female target population (, 50%). In basic resource settings: For which cohorts is routine vaccination recommended in basic resource settings Recommendation C2a For girls starting at 9 years of age who are immune competent, a two-dose regimen is recommended (Type of recommendation: evidence based; Evidence quality: intermediate; Strength of recommendation: moderate). Recommendation C2b the interval between the doses should be at least 6 months and may be up to 12 to15 (6 months: Type of recommendation: evidence based; Evidence quality: high; Strength of recommendation: strong. Where coverage of the primary targeted group of females is high (> 50%) and resources allow, the age group may be expanded upward in catch-up efforts (Type of recommendation: evidence based; Evidence quality: high; Strength of recommendation: strong). Recommendation C4 For prevention of cervical cancer in basic resource settings where vaccine coverage of girls is > 50%, vaccination of boys is not recommended. What vaccination strategy is recommended for women who are pregnant (all resource settings) What vaccination strategy is recommended for women receiving treatment of cervical cancer precursor lesions (cervical intraepithelial neoplasia grade > 2; eg, conization, loop electrosurgical excision process, or cryotherapy; all resource settings) Qualifying Statements Additional qualifying statements: If boys are vaccinated, use the same age-related recommendations as for girls, according to resource settings. Recommendations regarding boys do not apply to men who have sex with men, and readers are referred to Centers for Disease Control and Prevention, Australian, and other guidelines. Additional Resources More information, including a Data Supplement, a Methodology Supplement, slide sets, and clinical tools and resources, is available at The American Society of Clinical Oncology believes that cancer and cancer prevention clinical trials are vital to inform medical decisions and improve cancer care and that all patients should have the opportunity to participate. As a partial result of failures within different health care systems at levels of prevention (eg, vaccination and screening) and disease treatment and management, there are large regional jgo. This article summarizes the results of that process and presents the practice resource-stratified recommendations, which are based in part on expert consensus and adaptation from existing guidelines (described in Results and Appendix Table A1, online only). The Expert Panel met via teleconference and in person and corresponded through e-mail. On the basis of consideration of the evidence, the authors were asked to contribute to the development of the guideline, provide critical review, and finalize the guideline recommendations. The entire membership of experts is referred to as the consensus panel (the Data Supplement provides a list of members). The Panel used literature searches (1966 to 2015, with additional searches for literature published in specific areas [date parameters, 2005 to 2015]), existing guidelines and expert consensus publications, some literature suggested by the Panel, and clinical experience as guides. For updates and the most recent information and to submit new evidence, please visit With the rapid development of scientific knowledge, new evidence may emerge between the time information is developed and when it is published or read. The information addresses only 617 Volume 3, Issue 5, October 2017 the topics specifically identified therein and is not applicable to other interventions, diseases, or stages of diseases. Furthermore, the information is not intended to substitute for the independent professional judgment of the treating provider, because the information does not account for individual variation among patients. Each recommendation indicates high, moderate, or low confidence that the recommendation reflects the net effect of a given course of action. The use of words like "must," "must not," "should," and "should not" indicates that a course of action is recommended or not recommended for either most or many patients, but there is latitude for the treating physician to select other courses of action in individual cases. In all cases, the selected course of action should be considered by the treating provider in the context of treating the individual patient. In accordance with the Policy, a majority of the members of the Expert Panel did not disclose any relationships constituting a conflict under the Policy. Inclusion criteria identified publications that were (1) on the primary prevention of cervical cancer, (2) developed by multidisciplinary content experts as part of a recognized organizational effort, and (3) published between 1966 and 2015. Articles were excluded from the systematic review if they were (1) meeting abstracts or (2) books, editorials, commentaries, letters, news articles, case reports, or narrative reviews. A total of nine guidelines and seven systematic reviews were found in the literature search, and their currency, content, and methodology were reviewed. The Data Supplement includes an overview of these guidelines, including information on the clinical questions, target populations, development methodologies, and key evidence. The clinical questions concerned the age of initial target populations and ages for older populations who had not previously received vaccinations. The summary was in English, and the full guideline was in German; the clinical questions were not explicitly stated in the Englishlanguage summary. The clinical questions were not available; however, the guideline target population was girls and boys age 12 to 13 years. The German guideline used mixed methods, including evidence based, clinical (informal) consensus, clinical experience, and formal consensus in a nominal group process. The Immunize Australia guideline recommendations were based on methods involving an evidence base, expert review, and public comment. The guideline refers to using the highestquality evidence available and other guidelines. The score for the Rigour of Development domain is calculated by summing the scores across individual items in the domain and standardizing the total score as a proportion of the maximum possible score. For which cohorts is routine vaccination recommended in maximal and enhanced resource settings Public health authorities, ministries of health, and primary care providers should routinely vaccinate girls, with the target age range being as early as possible, starting at 9 through 14 years of age (Type of recommendation: evidence based; Evidence quality: high; Strength of recommendation: strong). Public health authorities may set the upper end of the target population higher than 14 years of age, depending on local policies and resources (Type of recommendation: evidence based; Evidence quality: low; Strength of recommendation: moderate). Subsequently, research has investigated the use of two doses with immunogenicity end points. Research comparing the upper end of the interval of 12 months with other intervals has not been conclusive and is ongoing (eg, ClinicalTrials. For girls 9 to 14 years of age who are immune competent, a two-dose regimen is recommended (Type of recommendation: evidence based; Evidence quality: intermediate; Strength of recommendation: moderate). The interval between two doses should be at least 6 months and may be up to 12 to 15 months (6 months: Type of recommendation: evidence based; Evidence quality: high; Strength of recommendation: strong. The source guidelines reviewed safety data, and this subject is discussed in detail in Special Topic C. The purpose of catch-up strategies is to address the temporary situation in which some persons are older than the priority target populations. Included studies were conducted in the United States, Canada, South America, Europe, and Asia and compared the vaccine with placebo or no vaccine. Although the systematic review looked for studies with a variety of outcomes, there were limited data of the effect of vaccination on mortality. For prevention of cervical cancer, if there is low vaccine coverage of the priority female target population (, 50%) in maximal or enhanced resource settings, vaccination may be extended to boys (Type of recommendation: evidence based; Evidence quality: intermediate; Strength of recommendation: moderate).
If the history or the physical examination suggests that the intubation will be difficult (Box 8-2) treatment spinal stenosis generic prochlorperazine 5 mg overnight delivery, then the patient must be given a regional anesthetic or have an awake intubation or the operation must be started with the patient under local anesthesia medications similar to vyvanse discount prochlorperazine 5 mg free shipping. Acrystalloidpreloadbolusof10 to 15mL/kg over 30 to 60 minutes is typically given beforeregionalanesthesia treatment alternatives boca raton order prochlorperazine 5mg with visa. For elective or urgent cesarean delivery (nonemergency) treatment xanthelasma eyelid discount prochlorperazine 5 mg with mastercard, regional anesthesia is preferable because the airway is maintained. Complicationsinvolvinglossof theairwayaretheleadingcausesofanesthesia-related maternal mortality and are usually associated with general anesthesia. A comparison of the characteristics of spinalandepiduralanesthesiaisshowninTable8-8. General anesthesia is employed for cesarean delivery in three situations: (1) there is extreme urgency andnopreexistingepiduralcatheter,(2)thereisacontraindication to regional anesthesia, or (3) regional anesthesiahasfailed(1. The protocol for general anesthesia for cesarean delivery includes oral administration of nonparticulate antacid(sodiumcitrate),routinemonitoringand left uterine displacement, preoxygenationforatleast fourvitalcapacitybreaths,andrapid sequence induction of anesthesia with cricoid pressure followed by intubation to prevent passive regurgitation and pulmonary aspiration of gastric contents. Inductionagentsusedforgeneralanesthesiainclude propofol(mostcommonly),thiopental(notcurrently available in the United States), etomidate (when cardiovascularstabilityisparticularlydesirable),andketamine(forpatientswithhypovolemiaorasthma). Narcotics may be administered after the delivery of the babytoreducetheneedforinhalationalanesthesia and provide postoperative pain relief. The patient must be extubated only when fully awake to minimize the risk of aspiration. Such patients should be advised to get an epidural catheter early to avoid the risks of a crash cesarean under general anesthesia. These fetuses may also benefit from the improved uterinebloodflowandcontrolleddeliverythatepiduralanalgesiaallows. Mothers who are at particularly high anesthetic riskshouldreceiveaprelaborconsultationforknown significant preexisting medical conditions. Theaveragetemperatureincreaseissmall,and most women do not develop fever; however, a small subsetofwomenwhoarepredisposedtodevelopfever dosoafterepiduraladministration. The risk of headache is about 1-2% with spinal anesthesia, and it is less than 1% with an epidural. Postdural puncture headaches are selflimited, usually resolving within 5 to 7 days. The hallmark is a severe positional headache: little or no headache if supine, but sudden onset of severe headache when sitting uprightorstanding. There appears to be no association between newonset, long-term back pain and labor epidural analgesia. Theoretically, a prolongation of the second stagecouldarisefromeffectsonthereleaseofendogenousoxytocin,prostaglandinF2,andotherhormones responsibleforthepropagationoflabor. Prolongation of the second stage could also be due to impaired ability to push (unlikely as long as motor block is avoided by appropriate adjustment of the epidural infusion) or to decreased maternal urge to push causedbysensoryblockade. Thelattercanusuallybe overcome by appropriate coaching and decreasing or haltingtheepiduralinfusion. Other side effects and complications of regional anesthesia or analgesia include fever (0. Theassociationwithmater- Resuscitation of the Newborn Improved surveillance using antenatal and intrapartumfetalheartratemonitoring,real-timeultrasonography, amniocentesis, and umbilical artery Doppler assessmentshasallowedthecliniciantorecognizethe fetus at risk who may need special care at birth. The goalsofanorganizedapproachtoneonatalresuscitation are to reverse any intrauterine hypoxia and to preventpostnatalasphyxia,whichmayresultinacute majororgandamageandlifelonghandicaps. Preparation for Extrauterine Life Prematurity is the leading cause of poor neonatal outcome because the fetus has not yet progressed through complete stages of anatomic development and biochemical maturation. C H A PE R 8 Normal Labor, Delivery, and Postpartum Care 121 Duringpregnancy,fetalthyroxine(T4)isconverted toreversetriiodothyronine(T3),whichismetabolically inactive. Several days before the onset of term labor, cortisol levels increase in the fetus and induce a change in thyroid hormone dynamics. Cortisol induces the enzyme system, allowing the conversion of T4 to triiodothyronine (T3), which is metabolically more active and necessary for neonatal thermogenesis. At birth, there is a surge of thyroid-stimulating hormone,andatnotimeduringlifedoesthishormone reachsuchhighlevelsasitdoes30minutesafterbirth. This is followed by a hyperthyroid neonatal state for several days, which is necessary for the newborn to maintainitsbodytemperature. A second change that occurs with the onset of labor is a change in fetal breathing activity. Fetalbreathing, as observed by real-time ultrasonography, is rarely observed once labor is established. This is thought to be associated with a decrease in pulmonary fluid dynamicsthatmaybeimportantfortheonsetofrespiration after delivery, as well as with the retention of surfactantinthelungs. Finally, labor is a stress to the fetus that stimulates the release of catecholamines. Only at times of severe stress later in life are catecholamine levels as highasthoseatbirth. Initially, the mouth is suctioned before the nose so that no material is present to aspirate with the first breaths. Deep or vigorous suction should be avoided because posterior pharyngeal stimulation may cause bradycardia from a vagal reflex. Ifamoderate amount of meconium is present, placing a nasal tracheal catheter into the oropharynx and applying suction before delivering the body are thought to decrease the risk of meconium aspiration. If meconium is present and the baby is not vigorous (heart rate >100 beats/min, strong respiratory effort, and good muscular tone), intubation should be performed to suction the trachea after suction of the mouth. Dry the Newborn An important part of neonatal adaptation is the initiation of nonshivering thermogenesis. Excessive cooling from exposure of the wet skin is detrimental to all preterm infants and to depressed full-term infants. Clamp the Cord the umbilical arteries usually close spontaneously within45to60secondsafterbirth,whereastheumbilical vein remains patent for 3 to 5 minutes or longer. Ensure Onset of Respiration the onset of respiration normally occurs within a few seconds after birth. If respiration has not commenced by 30 seconds, or if the heart rate is less than 100 beats/min, after delayed cord clamping, the infant should be passed off to the resuscitation team to manage the apnea and low heart rate with stimulation, and positive pressure ventilation should be started. Ifthebabyisdeliveredatterm,21%oxygen (roomair)shouldbeusedinitiallyandadjustedupward asmeasuredbypulseoximetryorclinicallyassessedin terms of nonresponsiveness to resuscitation. If the infant is preterm, 30-40% oxygen should be used initially in association with pulse oximetry, and the oxygen concentration should be adjusted to the saturationexpectedrelativetothenumberofminutes after birth (Figure 8-18). A newborn normally starts withanoxygensaturationof60-65%atbirth(bypulse oximetry), and this increases to 85-95% saturation over the first 10 minutes of life. All nurses working in the delivery room should be trained in techniques of neonatal assessment and resuscitation. If risk factors increase the likelihood of deliveringaninfantwithcardiorespiratorydepression, apediatriciantrainedinneonatalresuscitationshould be present. Correct Surfactant Deficiency For the premature infant, surfactant deficiency is the basic defect responsible for the development of the respiratory distress syndrome. These substancescanbegivenbytrachealinjectionatbirth to prevent the respiratory distress syndrome, or they can be given after the syndrome has developed to reduceitsseverityandtopreventmortality. Color 0 Absent Absent Limp None Pale, blue 1 <100 beats/min Slow, weak cry Some flexion of extremities Grimace Body, pink; extremities, blue 2 123 >100 beats/min Good, strong cry Active motion Strong cry Completely pink Apgar Score the Apgar score is an excellent tool for assessing the overallstatusofthenewbornsoonafterbirth(1minute) andaftera5-minuteperiodofobservation(Table8-9). Initiate Breathing the indications for positive pressure ventilation include apnea, gasping, and a heart rate less than 100 beats/min. Withanestablishedairway,eitherbagmask ventilation or ventilation via an endotracheal tube should be initiated at a rate of 40 to 60breaths/ min. Usually,theheartrateincreasesrapidlyafterthe apneaiscorrected,andintermittentbag-maskventilation with supplemental oxygen can be given until spontaneous respiration commences. Resuscitation of the Asphyxiated Infant During the past 15 years, increasing emphasis has been placed on transferring the mother with a highrisk pregnancy to a tertiary care regional center before laborratherthantransferringthesickneonate afterdelivery. Ideally, at the time of delivery, a segment of cord should be doubly clamped to allow blood gas determinations on cord arterial and venous blood. Ensure Cardiac Performance If cardiac performance is poor (heart rate <60beats/ min after 30 seconds of positive pressure ventilation with oxygen titrated to saturation), external cardiac massage should be initiated. The best technique for cardiac massage in the newborn is to compress the lower third of the sternum with two thumbs with the hands around the chest. Acompressionshouldoccur everyhalf-second,withaninterposedventilationafter every third compression (3:1 ratio), resulting in 90 chest compressions and 30 ventilations per minute. Establish an Airway After placing the newborn in a preheated radiant warmer, the airway should be opened by slightly extending the neck.
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