Instillation of 5% Povidone-Iodine Ophthalmic Drops Decreases the Respiratory Rate in Children Undergoing Strabismus Surgery: A Randomized Controlled Trial.

PURPOSE: To investigate the effects of topical application of ophthalmic 5% povidone-iodine eye drops, which has been reported to cause apnea in spontaneously breathing children during general anesthesia. METHODS: The authors conducted a randomized, controlled, single-blinded study comparing the effect of balanced salt solution eye drops and povidone-iodine eye drops on respiration in spontaneously breathing children during general anesthesia with sevoflurane via a laryngeal mask airway. Fifty patients received balanced salt solution eye drops and 50 patients received 5% povidone-iodine eye drops. RESULTS: None of the control patients had a significant change in respiration. Thirty of the 50 (60%) povidone-iodine patients had a slowing of respiration within the first 6 breaths after eye drop instillation (P < .001). The median time of respiratory pause in those 30 patients was 18.5 seconds (range: 4.36 to 96.2 seconds). Among the povidone-iodine patients, children with a history of a prior tonsillectomy and adenoidectomy and/or bilateral myringotomy had a 7.2 times greater chance of experiencing a change in respiration after instillation of the povidone-iodine eye drops. CONCLUSIONS: Topical application of 5% povidone-iodine eye drops causes a slowing and pause in spontaneous ventilation in a majority of children prior to strabismus surgery. This may represent activation of the diving reflex. [J Pediatr Ophthalmol Strabismus. 2019;56(6):378-382.].

Hypercapnia in diving: a review of CO2 retention in submersed exercise at depth.

Carbon dioxide (CO2) retention, or hypercapnia, is a known risk of diving that can cause mental and physical impairments leading to life-threatening accidents. Often, such accidents occur due to elevated inspired carbon dioxide. For instance, in cases of CO2 elimination system failures during rebreather dives, elevated inspired partial pressure of carbon dioxide (PCO2) can rapidly lead to dangerous levels of hypercapnia. Elevations in PaCO2 (arterial pressure of PCO2) can also occur in divers without a change in inspired PCO2. In such cases, hypercapnia occurs due to alveolar hypoventilation. Several factors of the dive environment contribute to this effect through changes in minute ventilation and dead space. Predominantly, minute ventilation is reduced in diving due to changes in respiratory load and associated changes in respiratory control. Minute ventilation is further reduced by hyperoxic attenuation of chemosensitivity. Physiologic dead space is also increased due to elevated breathing gas density and to hyperoxia. The Haldane effect, a reduction in CO2 solubility in blood due to hyperoxia, may contribute indirectly to hypercapnia through an increase in mixed venous PCO2. In some individuals, low ventilatory response to hypercapnia may also contribute to carbon dioxide retention. This review outlines what is currently known about hypercapnia in diving, including its measurement, cause, mental and physical effects, and areas for future study.

Assessment Tools for Use During Anesthesia-Centric Pediatric Advanced Life Support Training and Evaluation.

BACKGROUND: Pediatric perioperative cardiac arrests are rare events that require rapid, skilled and coordinated efforts to optimize outcomes. We developed an assessment tool for assessing clinician performance during perioperative critical events termed Anesthesia-centric Pediatric Advanced Life Support (A-PALS). Here, we describe the development and evaluation of the A-PALS scoring instrument. METHODS: A group of raters scored videos of a perioperative team managing simulated events representing a range of scenarios and competency. We assessed agreement with the reference standard grading, as well as interrater and intrarater reliability. RESULTS: Overall, raters agreed with the reference standard 86.2% of the time. Rater scores concerning scenarios that depicted highly competent performance correlated better with the reference standard than scores from scenarios that depicted low clinical competence (P < 0.0001). Agreement with the reference standard was significantly (P < 0.0001) associated with scenario type, item category, level of competency displayed in the scenario, correct versus incorrect actions and whether the action was performed versus not performed. Kappa values were significantly (P < 0.0001) higher for highly competent performances as compared to lesser competent performances (good: mean = 0.83 [standard deviation = 0.07] versus poor: mean = 0.61 [standard deviation = 0.14]). The intraclass correlation coefficient (interrater reliability) was 0.97 for the raters' composite scores on correct actions and 0.98 for their composite scores on incorrect actions. CONCLUSIONS: This study provides evidence for the validity of the A-PALS scoring instrument and demonstrates that the scoring instrument can provide reliable scores, although clinician performance affects reliability.

Swimming-Induced Pulmonary Edema: Pathophysiology and Risk Reduction With Sildenafil.

BACKGROUND: Swimming-induced pulmonary edema (SIPE) occurs during swimming or scuba diving, often in young individuals with no predisposing conditions, and its pathophysiology is poorly understood. This study tested the hypothesis that pulmonary artery and pulmonary artery wedge pressures are higher in SIPE-susceptible individuals during submerged exercise than in the general population and are reduced by sildenafil. METHODS AND RESULTS: Ten study subjects with a history of SIPE (mean age, 41.6 years) and 20 control subjects (mean age, 36.2 years) were instrumented with radial artery and pulmonary artery catheters and performed moderate cycle ergometer exercise for 6 to 7 minutes while submersed in 20°C water. SIPE-susceptible subjects repeated the exercise 150 minutes after oral administration of 50 mg sildenafil. Work rate and mean arterial pressure during exercise were similar in controls and SIPE-susceptible subjects. Average o2 and cardiac output in controls and SIPE-susceptible subjects were: o2 2.42 L·min(-1) versus 1.95 L·min(-1), P=0.2; and cardiac output 17.9 L·min(-1) versus 13.8 L·min(-1), P=0.01. Accounting for differences in cardiac output between groups, mean pulmonary artery pressure at cardiac output=13.8 L·min(-1) was 22.5 mm Hg in controls versus 34.0 mm Hg in SIPE-susceptible subjects (P=0.004), and the corresponding pulmonary artery wedge pressure was 11.0 mm Hg versus 18.8 mm Hg (P=0.028). After sildenafil, there were no statistically significant differences in mean pulmonary artery pressure or pulmonary artery wedge pressure between SIPE-susceptible subjects and controls. CONCLUSIONS: These observations confirm that SIPE is a form of hemodynamic pulmonary edema. The reduction in pulmonary vascular pressures after sildenafil with no adverse effect on exercise hemodynamics suggests that it may be useful in SIPE prevention. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00815646.

Immersion pulmonary edema and comorbidities: case series and updated review.

PURPOSE: Immersion pulmonary edema (IPE) occurs in swimmers (especially triathletes) and scuba divers. Its pathophysiology and risk factors are incompletely understood. This study was designed to establish the prevalence of preexisting comorbidities in individuals who experience IPE. METHODS: From 2008 to May 2010, individuals who had experienced IPE were identified via recruitment for a physiological study. Past medical history and subject characteristics were compared with those available in the current body of literature. RESULTS: At Duke University Medical Center, Durham, NC, 36 subjects were identified (mean age = 50.11 ± 10.8 yr), of whom 72.2% had one or more significant medical conditions at the time of IPE incident (e.g., hypertension, cardiac dysrhythmias or structural abnormality or dysfunction, asthma, diabetes mellitus, overweight or obesity, obstructive sleep apnea, hypothyroidism). Forty-five articles were included, containing 292 cases of IPE, of which 24.0% had identifiable cardiopulmonary risk factors. Within the recreational population, cases with identifiable risk factors comprised 44.9%. Mean age was 47.8 ± 11.3 yr in recreational divers/swimmers and 23.3 ± 6.4 yr in military divers/swimmers. CONCLUSIONS: Cardiopulmonary disease may be a common predisposing factor in IPE in the recreational swimming/diving population, whereas pulmonary hypertension due to extreme exertion may be more important in military cases. Individuals with past history of IPE in our case series had a greater proportion of comorbidities compared to published cases. The role of underlying cardiopulmonary dysfunction may be underestimated, especially in older swimmers and divers. We conclude that an episode of IPE should prompt the evaluation of cardiac and pulmonary function.