Cricoid ring: Shape, size, and variability in infants and children.

BACKGROUND: Knowledge regarding the shape, size, and variability of the cricoid ring is important to properly choose the correct endotracheal tube (ETT) in the pediatric patient. Studies have measured the size of the cricoid ring using methodologies such as moulages, magnetic resonance imaging, and video-bronchoscopy. In the present study, computed tomography (CT) -based images were used to determine the shape, size, and configuration of the cricoid ring in the pediatric population taking into considerations growth and development. METHODS: This is a retrospective review using 130 CT images of children ranging in age from 1 month to 10 years undergoing radiological evaluation unrelated to airway symptomatology. The CT scans were obtained in spontaneously breathing patients during either natural sleep or procedural sedation. Anteroposterior (AP) and transverse (T) diameters were measured at the cricoid ring using these images. RESULTS: The cricoid ring is generally round in children older than 1 year with a T/AP ratio ranging between 0.98 and 1.01. However, in infants (1-12 months of age), the cricoid ring is elliptical with the AP dimension an average of 0.31 mm larger than the T dimension with a T/AP ratio of 0.95. A statistically significant difference between the T and AP dimensions was only observed in infancy (P < 0.05). CONCLUSION: The cricoid ring is round in children older than 1 year of age. In infants, the cricoid shape presents a more elliptical configuration because the T-axis is narrower than the AP dimension. CT is recognized as the most accurate technique to study cricoid ring configuration, and the present data may help clinicians determine the appropriate type, size, and shape of ETTs, particularly in infants.

Estimation of the depth of the thoracic epidural space in children using magnetic resonance imaging.

BACKGROUND: The estimation of the distance from the skin to the thoracic epidural space or skin to epidural depth (SED) may increase the success rate and decrease the incidence of complications during placement of a thoracic epidural catheter. Magnetic resonance imaging (MRI) is the most comprehensive imaging modality of the spine, allowing for the accurate determination of tissue spaces and distances. The present study uses MRI-derived measurements to measure the SED and define the ratio between the straight and inclined SEDs at two thoracic levels (T6-7 and T9-10) in children. METHODS: The T2-weighed sagittal MRI images of 109 children, ranging in age from 1 month to 8 years, undergoing radiological evaluation unrelated to spine pathology were assessed. The SEDs (inclined and straight) were determined, and a comparison between the SEDs at two thoracic levels (T6-7 and T9-10) was made. Univariate and multivariate linear regression models were used to assess the relationship of the inclined thoracic T6-7 and T9-10 SED measurements with age, height, and weight. RESULTS: Body weight demonstrated a stronger association with the SED than did the age or height with R2 values of 0.6 for T6-7 and 0.5 for T9-10. The formulae describing the relationship between the weight and the inclined SED were T6-7 inclined (mm) = 7 + 0.9 × kg and T9-10 inclined (mm) = 7 + 0.8 × kg. CONCLUSION: The depth of the pediatric thoracic epidural space shows a stronger correlation with weight than with age or height. Based on the MRI data, the predictive weight-based formulas can serve as guide to clinicians for placement of thoracic epidural catheters.

Upper airway in infants-a computed tomography-based analysis.

BACKGROUND: Recent studies suggest that the pediatric airway is elliptical with the subglottis rather than the cricoid as the narrowest part contrary to the old belief of a funnel-shaped airway. The shape of the airway in neonates and infants has not been studied separately. This study seeks to define the shape of the upper airway in neonates and infants, and determine if there are differences in airway shape between infants and older children. METHODS: We studied 40 computed tomographic scans of children from birth to 12 months of age undergoing radiological evaluation unrelated to airway symptomatology. The computed tomographic scans were obtained during either natural sleep or with sedation and spontaneous ventilation without airway devices in place. Transverse and anteroposterior diameters were measured at the subglottic level and at the cricoid ring. RESULTS: The mean age was 5.9 ± 3.4 months. The mean transverse and anteroposterior diameters were 5.3 ± 0.83 mm and 7.2 ± 0.89 mm at the subglottic region and 6.1 ± 0.86 mm and 6.7 ± 0.79 mm at the cricoid level. An increase in the transverse dimension of the airway was observed from the subglottic region to the cricoid ring. Although the anteroposterior dimension decreased from the subglottis to the cricoid ring, the airway remained wider in the anteroposterior dimension compared to the transverse dimension from the subglottis to the cricoid ring. CONCLUSION: The present study demonstrates that the airway in neonates and infants between the subglottic area and the cricoid remains elliptical. The cricoid is not round as has been observed in older children. The airway is wider anteroposteriorly and narrows in the transverse dimension from the subglottis to the cricoid in infants.

Pediatric upper airway dimensions using three-dimensional computed tomography imaging.

INTRODUCTION: Computed tomography- (CT) and magnetic resonance imaging (MRI)-based measurements have recently suggested that the narrowest dimension of the pediatric airway is the subglottic region. These data are contrary to the previously held tenets of a funnel- or conical-shaped airway. The current study evaluates airway volumes and shapes using three-dimensional CT images of the air way column in spontaneously breathing children. METHODS: The study included CT-based radiological images of the neck in children who required imaging unrelated to airway symptomatology. The children were evaluated during spontaneous ventilation during natural sleep or with sedation without airway devices in place. The three-dimensional images of the airway column were evaluated, volumes calculated, and comparisons made between the subglottic, cricoid, and tracheal volumes and shapes. RESULTS: The study cohort included 54 children, ranging in age from 2 months to 8 years. An increase in the airway volumes was observed from the subglottic (0.17 ± 0.06 mm3 ) to the cricoid (0.19 ± 0.06 mm3 ) to the tracheal regions (0.22 ± 0.07 mm3 ). The volumes of the subglottic, cricoid, and tracheal regions demonstrated a linear relationship with age. CONCLUSION: This study confirms recent studies demonstrating that the subglottic region not the cricoid is the narrowest part of the airway.

Erythromelalgia in the pediatric patient: role of computed-tomography-guided lumbar sympathetic blockade.

Erythromelalgia (EM) is an uncommon condition characterized by erythema, increased skin temperature, and burning pain, most frequently occurring in the lower extremities. The pain is generally very severe and treatment can be extremely challenging, especially in the pediatric and adolescent population. We report a series of three cases of primary EM in pediatric patients involving the lower extremities, refractory to medical treatment that responded favorably to computed-tomography-guided lumbar sympathetic blockade. There was a significant improvement in pain scores, quality of life, and overall function as well as decreased analgesic requirements. Lumbar sympathetic blockade should be considered as a therapeutic modality in pediatric and adolescent patients with EM who are refractory to other treatments.

PERIOPERATIVE CARE OF A CHILD WITH CRISPONI SYNDROME.

Crisponi syndrome is an autosomal recessive disorder characterized by intermittent episodes of muscular contraction of the facial muscles with trismus and excessive salivation simulating a tetanic spasm. These episodes occur in response to tactile stimulation or during crying. Associated physical and constitutional findings include characteristic facial anomalies, camptodactyly, intermittent hyperthermia, and feeding difficulties. We present a 15-month-old girl who required anesthetic care during laparoscopic fundoplication and gastric tube insertion. The perioperative implications of the disorder are reviewed and suggestions for anesthetic management provided.

Oxymetazoline Metered Dose Spray: Factors Affecting Delivery Volume.

OBJECTIVES: The current study compared the amount of oxymetazoline delivered by various anesthesia providers when holding the bottle in the upright and inverted position. Additionally, the amount delivered from a full bottle and a half-full bottle was also investigated. METHODS: Using an analytical balance that was calibrated to zero, we evaluated the impact the position of the bottle and the volume of oxymetazoline in the bottle had on the amount being delivered by both anesthesia staff and trainees. RESULTS: When using both filled and half-filled bottles, the amount delivered increased significantly when comparing the upright versus inverted position. With a full bottle, the amount delivered when the bottle was inverted increased almost 10-fold from 62 ± 80 to 606 ± 366 µL (p < 0.0001). Similarly, even with a half-filled bottle, the amount delivered increased in the inverted positions from 41 ± 48 to 645 ± 393 µL. Regardless of the scenario, we also noted significant variation from provider to provider. CONCLUSIONS: Our results demonstrate that several factors may affect the amount of oxymetazoline delivered for metered dose bottles. Given the potential for severe end-organ effects with excessive dosage, alternative means of delivery are needed for its perioperative use.

Endotracheal tubes and the cricoid: Is there a good fit?

BACKGROUND: Choosing an appropriately sized endotracheal tube (ETT) is important in pediatric patients as an inappropriately sized ETT may result in multiple endotracheal intubation attempts or excessive pressure on the tracheal mucosa with the potential for airway damage. Although age-based formulas are generally used with choice of an ETT based on the internal diameter (ID), measurements of the outer diameter (OD) of the ETT would seem to be a more scientific approach to determine the proper size of an ETT. However, the variable OD of the ETT despite the same ID makes the selection of a proper sized ETT more difficult. The current study compares airway dimensions measured using computed tomography (CT) with the OD of ETTs from various manufacturers. METHODS: The outer diameter of commonly used ETTs (12 cuffed and 5 uncuffed) were measured and compared with CT-based cricoid measurements obtained from a previous study involving 130 pediatric patients, ranging in age from 1 month to 10 years. These data were used to determine the likelihood of a clinically acceptable match. RESULTS: The differences of the cricoid dimensions between the 5th and the 95th percentile in each group ranged from a minimum of 2.23mm to a maximum of 6.51mm. Depending on the manufacturer, there was significant variation in the OD of the ETTs with the same ID. These discrepancies, which varied according to manufacturer and were greater with uncuffed as compared to cuffed ETTs, impacted the chances of an acceptable fit with the cricoid diameters. CONCLUSION: When choosing an ETT, age-based formulas which use the ID may not be uniformly accurate in ensuring the appropriately-sized ETT given the variation in the OD despite the same ID. These issues further support the use of cuffed ETTs as the variation in fit can be adjusted by inflation of the cuff to provide an adequate tracheal seal.

Cricoid and left bronchial diameter in the pediatric population.

BACKGROUND: Lung isolation in the pediatric population can be problematic. The diameter and length of the right and left mainstem bronchi are not well described in young children. Information regarding these measurements may help determine the appropriate size of endotracheal tubes for endobronchial intubation as well as the development of lung isolation devices for the pediatric population. The present study is based on computed tomography (CT) measurements to evaluate airway dimensions. The goal of this study was to define the relationship between the diameters of the left mainstem bronchus (LMSB) and the cricoid ring, and to study the effect of age, weight, and height on these dimensions. METHODS: The two-dimensional CT images of 102 children, ranging in age from 1 month to 10 years, undergoing radiological evaluation unrelated to airway symptomatology were examined. The cricoid dimensions (anteroposterior and transverse diameters) were measured using transverse plane images. The LMSB diameter was measured below the carina along the long axis of left main bronchus. Univariate regression analysis was used to determine whether one or more of the variables (age, gender, height, weight) had a predictable relationship with the cricoid and the LMSB diameters. RESULTS: The cricoid as well as the LMSB diameters increase with age, height, and weight. The relationship between the cricoid diameter and the LMSB diameter remains constant across all ages with a ratio of 0.78 ± 0.14. This ratio was slightly larger for girls than boys (0.81 ± 0.16 vs 0.77 ± 0.13). CONCLUSION: The cricoid to LMSB ratio (relationship) remains constant with respect to age, height, and weight.

General anesthesia for the heaviest man in the world.

The prevalence of obesity has increased greatly over the last 20 years, resulting in an increase in the number of bariatric and nonbariatric surgeries in this population. We present the case of a 20-year-old male, weighing 610 kg (1345 lb), and believed to be the heaviest living man in the world. After 4 months of rigorous in-hospital weight reduction, now weighing 510 kg (1125 lb), he underwent a laparoscopic gastric sleeve procedure under general anesthesia. This report describes the management of his anesthetic and exemplifies the challenges associated with this patient population.