Anatomical In Vitro Investigations of the Pediatric Larynx: A Call for Manufacturer Redesign of Tracheal Tube Cuff Location and Perhaps a Call to Reconsider the Use of Uncuffed Tracheal Tubes.

BACKGROUND: Some in vivo studies question the traditional "funnel-shaped" infant larynx; further anatomic examinations were warranted. Examination of fixative free fresh autopsy laryngeal and upper tracheal specimens and multiple measurements was needed to determine consistency between current tracheal tube designs and anatomic observations. METHODS: Larynges from 19 males and 11 females (Caucasian term newborn to 126 months) were examined by the same forensic pathologist. Measurements included anterior/posterior (A/P) and transverse (T) diameters of the cricoid outlet (CO), interarytenoid diameter (IAD), cricothyroid membrane (CTM), distance from the vocal cords (VC) to CO (VC-CO), and calibration of the larynx lumen with uncuffed tracheal tubes as measuring rods. Assessment of "safe tracheal tube placement" was assessed using manufacturer recommended cuffed Microcuff (Kimberly-Clark, Koblenz, Germany) tubes. RESULTS: In 77% (95% confidence interval [CI], 58-90) of specimens, the proximal end of the cuff was within the CO and in 23% even with or close to the CO. The VC-CO varied from 9.1 to 13.17 mm in infants, 11.55 to 15.17 mm in toddlers, and 13.19 to 18.34 mm in children. The A-P/T ratio of the CO was nearly 0.99 in most larynges; the IAD was greater than CO in all specimens. The CTM could be minimally distended in all specimens. CONCLUSIONS: First, despite being marketed as a safer tracheal tube design, the proximal end of the Microcuff cuff rested within or close to the cricoid cartilage theoretically increasing potential cuff-induced injury when using the VC markings for positioning. Our data suggest that the optimal cuff free distance (VC-CO) would be ~13.5 mm for a Microcuff internal diameter (ID) size 3.0, ~15 mm for size 3.5, and ~16 to 19 mm for greater sizes.Second, the CO was virtually circular in all specimens, suggesting that appropriately sized uncuffed tubes should provide an adequate seal in most neonates and toddlers, thus avoiding the potential for cuff-related necrosis injury.Third, the IAD was always greater than CO confirming that the narrowest point of the infant larynx is the nondistensible cricoid cartilage and not the easily distended glottis.Fourth, appropriately sized Microcuff tubes with the cuff deflated completely filled the lumen of the CO and proximal trachea in all specimens. Our data suggest the need for all manufacturers to further evaluate tracheal tube cuff locations and lengths in relation to the VC safe insertion markings, particularly for neonates and toddlers.Fifth, the CTM is minimally distensible, thus having important implications for emergency surgical airway access with most currently available emergency airway devices.

The anatomy of the pediatric airway: Has our knowledge changed in 120 years? A review of historic and recent investigations of the anatomy of the pediatric larynx.

BACKGROUND: There is disagreement regarding the anatomy of the pediatric airway, particularly regarding the shape of the cricoid cartilage and the location of the narrowest portion of the larynx. AIMS: The aim of this review is to clarify the origin and the science behind these differing views. METHODS: We undertook a review of published literature, University Libraries, and authoritative textbooks with key search words and phrases. RESULTS: In vivo observations suggest that the narrowest portion of the airway is more proximal than the cricoid cartilage. However, in vitro studies of autopsy specimens measured with rods or calipers, confirm that the nondistensible and circular or near circular cricoid outlet is the narrowest level. These anatomic studies confirmed the classic "funnel" shape of the pediatric larynx. In vivo studies are potentially misleading as the aryepiglottic, vestibular, and true vocal folds are in constant motion with respiration. These studies also do not consider the effects of normal sleep, inhalation agents, and comorbidities such as adenoid or tonsil hypertrophy that cause some degree of pharyngeal collapse and alter the normal movement of the laryngeal tissues. Thus, the radiologic studies suggesting that the narrowest portion of the airway is not the cricoid cartilage may be the result of an artifact depending upon which phase of respiration was imaged. CONCLUSION: In vivo studies do not take into account the motion of the highly pliable laryngeal upper airway structures (aryepiglottic, vestibular, and vocal folds). Maximal abduction of these structures with tracheal tubes or bronchoscopes always demonstrates a larger opening of the glottis compared to the outlet of the cricoid ring. Injury to the larynx depends upon ease of tracheal tube or endoscope passage past the cricoid cartilage and not passage through the readily distensible more proximal structures. The infant larynx is funnel shaped with the narrowest portion the circular or near circular cricoid cartilage confirmed by multiple in vitro autopsy specimens carried out over the past century.

Tracheoscopic Findings and Their Impact on Respiratory Symptoms in Children with Esophageal Atresia.

INTRODUCTION: Esophageal atresia (EA) is often accompanied by tracheobronchial malformations leading to stridor, recurrent bronchitis, and occasionally to life-threatening obstructive apnea after surgical repair. The aim of this study was to identify the presence of tracheomalacia in patients with EA and tracheoesophageal fistula (TEF) pre- and postoperatively and to find endoscopic correlates leading to clinical airway symptoms. METHODS: In a cohort of 362 patients with EA-TEF who underwent 595 tracheoscopies at the Children's Hospital of Cologne between January 1983 and December 2002, impaired tracheal lumen, localization of TEF, tracheal pulsations, and corresponding clinical symptoms were retrospectively analyzed. RESULTS: The incidence of tracheomalacia was higher in patients with EA and TEF (Gross B-D) compared with patients with EA alone (Gross A) and average tracheal collapse does not significantly change before and after surgical repair of the esophagus in all types. Patients with cyanosis while eating and obstructive apnea presented with an average tracheal collapse of 89%. The presence of respiratory symptoms such as cough, stridor, or bronchitis was not associated with a higher grade of tracheal collapse compared with patients without any airway symptoms (average tracheal collapse of 37% in symptomatic patients vs. 33% in nonsymptomatic patients). CONCLUSION: Tracheomalacia tends to be present independently of surgical procedure. Tracheomalacia should be measured by tracheoscopy (in % of tracheal collapse). Patients with a tracheal collapse of >80%, a ventral pulsation, and obstructive apnea or cyanosis in combination, are at risk for life-threatening situations and further surgical treatment should be considered.

Iatrogenic damage to the pediatric airway. Mechanisms and scar development.

Iatrogenic damage to the pediatric airway occurs rather often. Most injuries will heal without any sequelae because larynx and trachea of children tolerate considerable trauma. However, sometimes the injury is penetrating the mucosa and scar formation can lead to an obstruction of the airway which is followed by a tracheostomy and long term surgery. A great problem is the early detection of trauma since noisy breathing develops often late when scar formation has occluded more than 50% of the airway. A selection of photo documents of airway endoscopy out of more than 5000 photos from the years 1987-2007 were used to explain the development of injuries from minor lesions to large areas of necrosis of the mucosa of larynx and trachea of infants and children. The visualization of airway lesions might help to prevent iatrogenic damage.

Stridor is not a scientifically valid outcome measure for assessing airway injury.

Since about a decade cuffed intubation is becoming more popular in pediatric anesthesia. Studies supporting cuffed intubation compared cuffed and uncuffed intubation by using stridor as main outcome measure after extubation. No differentiations were made between benign (oedema) and severe (ulceration of mucosa) lesions. Stridor was considered to represent all relevant injuries. Far reaching conclusions for daily practice were drawn from these studies. Pediatric endoscopists and - ENT-surgeons with extensive experience in this field have warned against this opinion because significant injury of the airway is not always accompanied by stridor! The symptom of stridor might develop weeks and months after injury when silent ulcerations of the mucosa retract to significant stenosis. Only endoscopy can evidently detect all airway injuries. Studies describing airway injury by endoscopic control are urgently needed to find the best way of preventing airway injury by intubation.

Recent advances in pediatric anesthesia.

Writing about advances in a field of medicine normally includes some pride about progress which one was witness to or even a participant in. The younger one is, the more enthusiastically every advance is lauded and welcomed. This is human nature and nothing to be complained about. However, when anesthesiologists, having worked and struggled in the field of pediatric anesthesia for about 40 years, look back to past advances, a more realistic, even painful picture comes to mind. There was a price which a considerable number of patients had to pay for progress, ruined health or even death. This experience of decades of practice is rarely presented in the literature but should not be forgotten when we proudly remember advances in pediatric anesthesia.

Life threatening unilateral pulmonary overinflation might be more successfully treated by contralateral selective intubation than by emergency pneumonectomy.

During a period of 3 years, three infants were admitted to our hospital for unilateral emergency pneumonectomy due to life threatening overinflation of one lung, preventing adequate ventilation of the unaffected contralateral side. All three patients were able to be stabilized by unilateral selective bronchial intubation of the unaffected lung after bronchoscopy, ruling out a flap valve mechanism. No emergency pneumonectomies were required. In one patient, lung function of the overinflated side (three lobes) recovered fully and, in the two remaining patients, one lobe of the overinflated side recovered. The overinflated lobes were removed later by elective surgery, thus not exposing the children to a potentially dangerous emergency operation. These results are in contrast with reports in the literature. Emergency pneumonectomy in neonates and infants due to overinflation of one lung may be avoided by selective unilateral intubation of the main stem bronchus of the compressed lung.

Death after re-exposure to propofol in a 3-year-old child: a case report.

This case report discusses the cause of death in a 3-year-old child who survived a high dose (20 mg x kg-1 x h-1) of propofol, infused over a period of 15 h, following which the patient developed a combined respiratory and metabolic acidosis, the oxygenation remaining normal. Bronchospasm was assumed to be the cause of hypercapnia. At this time the doctors in charge did not think of a possible side-effect of propofol. The administration of propofol was interrupted, the patient recovered within 13 h from the acidosis, woke up and required further sedation. A supposedly entirely safe infusion of 4 mg x kg-1 x h-1 propofol, as recommended in the literature for up to 48 h, was administered. After only 8 h intractable bradycardic dysrhythmias occurred. Although pharmacokinetic studies have pointed to a possible accumulation of propofol during continuous infusions, an interruption of an infusion for several hours has been considered sufficient for practically total clearance of the drug from the body. In this case re-exposure with a recommended dose of propofol was accompanied by bradycardia and dysrythmias that proved to be resistant to therapy and led to fatal cardiac insufficiency with a functioning artificial pacemaker in place. This case raises concerns about the safety of long-term infusions of propofol for sedation in children and possibly also in adults.

A randomized, controlled study of fluid management in infants and toddlers during surgery: hydroxyethyl starch 6% (HES 70/0.5) vs lactated Ringer's solution.

BACKGROUND: Volume replacement with hydroxyethyl starch (HES), a synthetic colloid, is widely accepted in adults, but only few data exist regarding its use in children. The aim of this study was to assess the effect of a low molecular weight HES solution (HES 70/0.5) compared with lactated Ringer's solution (LR) on haemoglobin levels as an indirect measure of plasma expansion in infants and toddlers, and its perioperative safety. METHODS: Sixty-four patients, aged 1-38 months, were allocated randomly to receive 20 ml x kg-1 body weight of either HES 70/0.5 or LR during the first hour of urological surgery lasting >2 h. Thereafter, only LR was infused to maintain haemodynamic stability. Intraoperative blood loss and administered fluid volumes were analysed. Haemoglobin levels were determined perioperatively and intraoperatively at completion of volume loading. Changes in body weight and the incidence of postoperative oedema were assessed 24 and 48 h after surgery. For the safety analysis, patients were monitored for 72 h. RESULTS: Intraoperative haemoglobin levels decreased significantly more with HES 70/0.5 (30 +/- 10 g.l-1) compared with LR (21 +/- 12 g.l-1) (P < 0.01). The overall administered fluid volumes during surgery did not differ between groups. The postoperative changes in body weight and incidence of postoperative oedema did not differ between groups. No anaphylactoid reactions, pruritus or adverse effects were observed during the study period. CONCLUSIONS: A larger decrease in haemoglobin levels in infants and toddlers after HES 70/0.5 (20 ml.kg-1) compared with LR indicates a more effective plasma expansion. HES might be considered as a volume expander in the paediatric population.

Functional upper airway obstruction in a child with Freeman-Sheldon syndrome.

Freeman-Sheldon syndrome is defined as a combination of microstomia, deep set eyes, small palpebral fissures, arthrogryposis with ulnar deviation of the hand, talipes equinovarus and generalized muscular hypertension. Respiratory and swallowing problems are frequently encountered in these patients due to small orifices of mouth and nose. Obstruction of the upper airway tract resulting in tracheostomy has only been described twice. The described child manifested the typical dysmorphic features of Freeman-Sheldon syndrome and suffered from serious respiratory distress and swallowing difficulties from birth. The boy died at the age of 7 months after accidental decannulation of the tracheostoma during sleep. He did not show anatomical or histopathological abnormalities in the pharyngeal, laryngeal or tracheal regions. We assume that the only explanation of the repeated obstructive episodes is a functional muscular obstruction.