How much reduced hemoglobin is necessary to generate central cyanosis?

Failing with Cyanosis-Heart Failure in End-Stage Unrepaired or Partially Palliated Congenital Heart Disease

Heart failure in cyanotic congenital heart disease (CHD) is diagnosed clinically rather than relying solely on ventricular function assessments. Patients with cyanosis often present with clinical features indicative of heart failure. Although myocardial injury and dysfunction likely contribute to cyanotic CHD, the primary concern is the reduced delivery of oxygen to tissues. Symptoms such as fatigue, lassitude, dyspnea, headaches, myalgias, and a cold sensation underscore inadequate tissue oxygen delivery, forming the basis for defining heart failure in cyanotic CHD. Thus, it is pertinent to delve into the components of oxygen delivery in this context.

Cyanotic congenital heart disease - Not always blue to provide a clue: Time to replace cyanosis with arterial desaturation!

Despite right-to-left shunt, not all patients with so-called cyanotic congenital heart disease (CHD) are cyanosed at all times. Moreover, despite undisputed clinical utility, cyanosis is unreliable for the detection of arterial desaturation. Pulse oximetry, on the other hand, provides a much easier, reliable, and accurate method for detecting arterial desaturation. For optimal detection, therefore, it is perhaps sensible to replace cyanosis with pulse oximetry-based detection of arterial desaturation in all cases with suspected CHD.

Cardiac emergencies in neonates and young infants

Cardiac emergencies in children are not infrequent. Early recognition and management are essential to save life and prevent any comorbidity. The presentation of cardiac emergencies and etiologies is variable depending on the age of child at the time of presentation and type of cardiac lesion. Cyanotic and noncyanotic congenital heart diseases are the main causes in neonates and infants. Acquired heart diseases and dysrhythmia are more common causes for cardiac emergencies in toddler and childhood. In this review, we discuss the most common causes for cardiac emergencies in neonates and young infants highlighting important points in the presentation and management that are essential for early recognition and timely management of infants presenting with these conditions.

Perinatal Cardiovascular Physiology and Recognition of Critical Congenital Heart Defects

Understanding the perinatal cardiovascular physiology is essential for timely diagnosis and management of congenital heart defects (CHDs) in neonatal period. The incidence of CHDs is reported in 7 to 9 out of 1000 live births, with around 25% of them being critical congenital heart disease, defined as a congenital heart condition needing surgery/intervention or leading to death within 1 month after birth. Around 50% to 60% of the critical CHDs are detected on fetal anomaly screening. The signs and symptoms of critical congenital heart defects are often nonspecific during early neonatal period. The routine newborn physical examination often fails to detect many of these critical CHDs during the transitional circulation because of lack of signs soon after birth. While routine pulse oximetry screening typically performed at 24 to 48 hours after birth may help in detecting cyanotic heart conditions, noncyanotic CHDs such as coarctation of aorta may go undetected on pulse oximetry screening in asymptomatic infants. Some infants may deteriorate early while waiting for pulse oximetry screening, and this risk is much higher if the pulse oximetry screening is not performed to detect congenital heart conditions. There should be high degree of suspicion of critical CHDs in infants presenting with shock or hypoxia. Delay in diagnosis of CHDs has been reported to be associated with poor outcomes, and hence, it is extremely important to detect them in asymptomatic well-infants. Timely recognition and therapy with prostaglandin E1 infusion can be lifesaving in neonatal cardiac emergencies, and they should be urgently discussed with a pediatric cardiologist. This article reviews diagnosis and management of CHD in the delivery room and before surgery in the NICU.

Case Report: Phenazopyridine-Induced Sulfhemoglobinemia in an 83-Year-Old Presenting with Dyspnea

BACKGROUND

Sulfhemoglobinemia is a rare dyshemoglobinemia that presents similarly to methemoglobinemia.

CASE REPORT

An 83-year-old woman with stage IV ovarian cancer presented to the Emergency Department after a near syncopal spell and was found to be cyanotic with a pulse oximetry reading of 71%. Pulse oximetry improved to only the mid-80s range with administration of high-flow oxygen. Her arterial blood gas on supplemental high-flow oxygen demonstrated a PaO₂ of 413 mm Hg and methemoglobin of 1.2%, but also noted the interference of the co-oximetry with sulfhemoglobinemia. Further history revealed that the patient had recently been started on phenazopyridine. The phenazopyridine was stopped, an exchange transfusion was offered but declined, and the patient was discharged to home hospice. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: The diagnosis of sulfhemoglobinemia can be challenging given that routine co-oximetry does not identify it. The clue to the diagnosis is that the cyanotic-appearing patient has a normal or elevated PaO₂ and seems to be less ill than expected, given the degree of cyanosis. Sulfhemoglobinemia does not reverse with the administration of methylene blue.

Colour analysis of the equine endometrium: comparison of spectrophotometry and computer-assisted analysis of photographs within the L*a*b* colour space system

The aims of this study were to compare two different methods of quantifying the colour of the luminal surface of the equine endometrium and to relate the results to histopathological evidence of inflammation and fibrosis. The mucosal surfaces of 17 equine uteri obtained from an abattoir were assessed using a spectrophotometer and by computer-assisted analysis of photographs. Values were converted into L(*)a(*)b(*) colour space. Although there was significant correlation between the two methods of quantification, variations in 'brightness', 'red' and 'yellow' values were noted. Within a given uterus, measurements using the spectrophotometer did not differ significantly. Using photographic analysis, brightness differed between horns, although no differences in chromaticity were found. Histopathological classification of changes within endometria corresponded to measured differences in colour. Extensive fibrosis was associated with increased brightness and decreased chromaticity using both methods. Inflammation correlated with reduced chromaticity, when measured by spectrophotometry, and with reduced brightness and yellow values, when assessed photographically. For this technique to gain wider acceptance as a diagnostic tool, e.g. for the endoscopic evaluation of uterine mucosae in vivo, standardised illumination techniques will be required so that colours can be compared and interpreted accurately.

Critical care in the ED: potentially fatal asthma and acute lung injury syndrome

Emergency department clinicians are frequently called upon to assess, diagnose, and stabilize patients who present with acute respiratory failure. This review describes a rapid initial approach to acute respiratory failure in adults, illustrated by two common examples: (1) an airway disease - acute potentially fatal asthma, and (2) a pulmonary parenchymal disease - acute lung injury/acute respiratory distress syndrome. As such patients are usually admitted to hospital, discussion will be focused on those initial management aspects most relevant to the emergency department clinician.

Pulse oximetry in pediatric practice

The introduction of pulse oximetry in clinical practice has allowed for simple, noninvasive, and reasonably accurate estimation of arterial oxygen saturation. Pulse oximetry is routinely used in the emergency department, the pediatric ward, and in pediatric intensive and perioperative care. However, clinically relevant principles and inherent limitations of the method are not always well understood by health care professionals caring for children. The calculation of the percentage of arterial oxyhemoglobin is based on the distinct characteristics of light absorption in the red and infrared spectra by oxygenated versus deoxygenated hemoglobin and takes advantage of the variation in light absorption caused by the pulsatility of arterial blood. Computation of oxygen saturation is achieved with the use of calibration algorithms. Safe use of pulse oximetry requires knowledge of its limitations, which include motion artifacts, poor perfusion at the site of measurement, irregular rhythms, ambient light or electromagnetic interference, skin pigmentation, nail polish, calibration assumptions, probe positioning, time lag in detecting hypoxic events, venous pulsation, intravenous dyes, and presence of abnormal hemoglobin molecules. In this review we describe the physiologic principles and limitations of pulse oximetry, discuss normal values, and highlight its importance in common pediatric diseases, in which the principle mechanism of hypoxemia is ventilation/perfusion mismatch (eg, asthma exacerbation, acute bronchiolitis, pneumonia) versus hypoventilation (eg, laryngotracheitis, vocal cord dysfunction, foreign-body aspiration in the larynx or trachea). Additional technologic advancements in pulse oximetry and its incorporation into evidence-based clinical algorithms will improve the efficiency of the method in daily pediatric practice.

Surgical inflammation: a pathophysiological rainbow

Tetrapyrrole molecules are distributed in virtually all living organisms on Earth. In mammals, tetrapyrrole end products are closely linked to oxygen metabolism. Since increasingly complex trophic functional systems for using oxygen are considered in the post-traumatic inflammatory response, it can be suggested that tetrapyrrole molecules and, particularly their derived pigments, play a key role in modulating inflammation.

In this way, the diverse colorfulness that the inflammatory response triggers during its evolution would reflect the major pathophysiological importance of these pigments in each one of its phases. Therefore, the need of exploiting this color resource could be considered for both the diagnosis and treatment of the inflammation.

Discordance between data acquired by history and findings of physical examination: a phenomenal paradox

BACKGROUND

History and physical examination are the basis of any diagnosis. The findings of the physical examination usually corroborate the thoughts generated by the medical history. However, it is not uncommon for the physician to note discrepancies between the history and the physical examination.

METHODS

Two physicians provided a list of diseases they have encountered in which there is occasionally discordance between the data retrieved from the patient's medical history and the findings of the physical examination. To verify the data from knowledge and experience, we resorted to two main medical textbooks and relevant articles from PubMed.

RESULTS

We identified 25 diseases where a discordance between history and physical examination may frequently be observed. These diseases cover a wide spectrum of systems (i.e., neurological, cardiological, respiratory, and gastrointestinal).

DISCUSSION

A variety of diseases are associated with a discordance between the findings one might expect based on the medical history and the actual findings of the physical examination. Physicians need to be aware of this paradox, as misdiagnosis can be detrimental in some of these diseases. We acknowledge that this is just a sample, and not an exhaustive list, of all diseases with such a discordance.

Cardiac emergencies in the first year of life

Cardiac emergencies in the first year of life can be anxiety provoking for the health care provider. An understanding of the pathophysiology involved in the most common emergency department presentations is crucial to the development of appropriate treatment plans. This article discusses the most common causes of cyanotic and acyanotic heart disease in infants.

Cardiovascular Emergencies in the Pediatric Patient

Children who have heart disease may present to the emergency department (ED) in many stages of life with a range of cardiovascular manifestions, from minimally irritating palpitations to the life-threatening derangements of shock or lethal dysrhythmia. They can present with congenital heart disease, after a temporizing procedure has been performed or after their definitive repair. Children can also present with fever, weakness, dyspnea, syncope, or chest pain; alternatively, children may present to the ED with active dysrhythmia, pulmonary edema, or cardiogenic shock . These symptoms and presentations may result from Kawasaki disease,hypertrophic cardiomyopathy, or arrhythmia; therefore, emergency physicians must also be comfortable with the most common types of heart disease associated with these symptoms and presentations. The purpose of this article is to describe the physiology and presentation of undiagnosed congenital heart disease, to describe the complications that can occur after a staged or definitive repair,and to discuss acquired heart disease in children.

Impact of clinical experience on quantification of clinical signs at physical examination

PURPOSE

Although physical examination is a fundamental component of medical decision making, relatively few studies have evaluated how physicians quantify clinical signs and whether different methods of assessment have different effects on clinical practice.

OBJECTIVES

To evaluate a possible impact of clinical experience when attending physicians, medical residents and medical students quantify qualitative signs of physical examination in a teaching hospital.

SETTING

Hospital das Clínicas, University of São Paulo, Brazil.

SUBJECTS

A total of 244 randomly selected physicians and medical students completed a reliable and consistent eight-item questionnaire.

MAIN OUTCOME MEASURES

To compare how they quantified clinical signs of cyanosis, anaemia, jaundice, oedema and dehydration, why they used the method(s) they described, and whether the method used could affect diagnosis, further testing or patient management. A chi-square test was used to calculate differences between the groups.

RESULTS

Whilst the majority of those surveyed tended to use a four-level evaluation for these clinical signs, attending staff physicians were more likely to employ two-level evaluations than were residents or medical students. For all five signs, attending physicians' use of dichotomous evaluations was significantly higher than that of residents or medical students: anaemia (P = 0.004), cyanosis (P < 0.001), oedema (P = 0.005), dehydration (P < 0.001) and jaundice (P = 0.002).

CONCLUSION

Although medical students and residents are routinely taught to use a four-level evaluation for these clinical signs, many of those surveyed tend to abandon this experience for a dichotomous approach. Given that the clinicians in this survey tended not to change their initial approach to a patient based on the intensity of this semi-quantitative method, increased emphasis on teaching dichotomous approach evaluations in medical school should be encouraged.

Pulse oximeter analysis of peripheral cyanosis distal to an AV fistula

Arteriovenous (AV) fistulas are routinely constructed for hemodialysis in patients with renal failure. The case of a hemodialysis patient with cyanosis of the hand distal to an AV fistula is described. Pulse oximeter analysis found a saturation of 72% in the cyanotic hand with a normal saturation of 97% in the opposing hand. Evaluation of 11 additional patients with AV fistulas and no cyanosis or symptoms found no difference in oxygen saturation between extremities. Pulse oximetry was found to be useful for evaluating the oxygenation status distal to an AV fistula, and in asymptomatic patients with an AV fistula, the oxygenation status distal to the fistula should be no different from that of the opposing extremity.

Management of acute asthma

Patients with acute asthma experience increased airway obstruction, increased work of breathing, and ventilation-perfusion mismatch. Careful observation and assessment of the patient are fundamental for successful treatment. Therapy is dictated by the severity of the acute episode. Prevention of subsequent flares of asthma needs to be initiated as the patient convalesces.