Priti G. Dalal

Sedation and Anesthesia Protocols Used for Magnetic Resonance Imaging Studies in Infants: Provider and Pharmacologic Considerations

Most studies report the efficacy of only a single drug to achieve sedation in a broad age range of children. In clinical practice, a variety of sedative and anesthetic regimes are monitored by nurses and physicians. In this study we report the efficacy of a tiered approach to monitoring and sedation in infants. Two-hundred-fifty-eight infants who required magnetic resonance imaging (MRI) studies received either oral chloral hydrate (n = 102) or bolus doses of IV pentobarbital (n = 67) monitored by nurses or IV propofol infusion (n = 68) titrated by physicians. Fewer cardiorespiratory events were observed in the chloral hydrate group (2.9%) compared to pentobarbital (13.4%) and propofol groups (13.6%); P < 0.05, propofol versus chloral hydrate. Infants who received propofol were ready to begin MRI scanning earlier (mean 9.1 ± 6.7 min) than infants who received oral chloral hydrate (mean 23.5 ± 13.4 min; P < 0.05). The time to discharge was longest in the pentobarbital (mean 80.3 ± 39.2 min) and shortest in the propofol group (mean 53.9 ± 30.1 min; P < 0.05). Infants in the chloral hydrate group moved more frequently (22.5%) during MRI scanning (with four sedation failures of 102) compared to 12.2% in the pentobarbital group and 1.4% in the propofol group (P < 0.001).

Pediatric laryngeal dimensions: an age-based analysis.

BACKGROUND: In children, the cricoid is considered the narrowest portion of the “funnel-shaped” airway. Growth and development lead to a transition to the more cylindrical adult airway. A number of airway decisions in pediatric airway practice are based on this transition from the pediatric to the adult airway. Our primary aim in this study was to measure airway dimensions in children of various ages. The measures of the glottis and cricoid regions were used to determine whether a transition from the funnel-shaped pediatric airway to the cylindrical adult airway could be identified based on images obtained from video bronchoscopy. METHODS: One hundred thirty-five children (ASA physical status 1 or 2) aged 6 mo to 13 yr were enrolled for measurement of laryngeal dimensions, including cross-sectional area (G-CSA), anteroposterior and transverse diameters at the level of the glottis and the cricoid (C-CSA), using the video bronchoscopic technique under general anesthesia. RESULTS: Of the 135 children enrolled in the study, seven patients were excluded from the analysis mainly because of poor image quality. Of the 128 children studied (79 boys and 49 girls), mean values (±standard deviation) for the demographic data were age 5.9 (±3.3) yr, height 113.5 (±22.2) cm and weight 23.5 (±13) kg. Overall, the mean C-CSA was larger than the G-CSA (48.9 ± 15.5 mm2 vs 30 ± 16.5 mm2, respectively). This relationship was maintained throughout the study population starting from 6 mo of age (P < 0.001, r = 0.45, power = 1). The mean ratio for C-CSA: G-CSA was 2.1 ± 1.2. There was a positive correlation between G- and the C-CSA versus age (r = 0.36, P < 0.001; r = 0.27, P = 0.001, respectively), height (r = 0.34, P < 0.001; r = 0.29, P < 0.001, respectively), and weight (r = 0.35, P < 0.001; r = 0.25, P = 0.003, respectively). No significant gender differences in the mean values of the studied variables were observed. CONCLUSION: In this study of infants and children, the glottis rather than cricoid was the narrowest portion of the pediatric airway. Similar to adults, the pediatric airway is more cylindrical than funnel shaped based on these video bronchoscopic images. Further studies are needed to determine whether these static airway measurements in anesthetized and paralyzed children reflect the dynamic characteristics of the glottis and cricoid in children.

Fatal hyperammonemia after renal transplant due to late-onset urea cycle deficiency: a case report.

We present a case of severe hyperammonemia with subsequent brain herniation in an adult man after renal transplantation. After successful surgery and an initially uneventful postoperative course, the patient developed significant mental status changes associated with seizure activity. His condition rapidly deteriorated, requiring mechanical ventilation and cardiovascular support. Laboratory studies at that time demonstrated an increased serum ammonia level without evidence of liver or kidney dysfunction. Further investigation revealed an increased orotic acid level in the urine, suggesting a urea cycle disorder (UCD). Despite aggressive therapy, the patients condition continued to deteriorate. Magnetic resonance imaging demonstrated severe brain edema with no cerebral perfusion; after consultation with the family, care was withdrawn. The combination of hyperammonemia and elevated urine orotic acid with normal liver and kidney function suggested a UCD. It is important to note that patients with a UCD may be free of symptoms for many years. Several factors are able to trigger the disease in adulthood, leading to encephalopathy and death. In this case, the patients seizures were initially assumed to be a side effect of immunosuppressive therapy. Further diagnostic measures were only performed late in the course of the disease, which delayed the diagnosis of UCD.

Safety of the breast-feeding infant after maternal anesthesia.

There has been an increase in breast‐feeding supported by the recommendations of the American Academy of Pediatrics and the World Health Organization. An anesthesiologist may be presented with a well‐motivated breast‐feeding mother who wishes to breast‐feed her infant in the perioperative period. Administration of anesthesia entails acute administration of drugs with potential for sedation and respiratory effects on the nursing infant. The short‐term use of these drugs minimizes the possibility of these effects. The aim should be to minimize the use of narcotics and benzodiazepines, use shorter acting agents, use regional anesthesia where possible and avoid agents with active metabolites. Frequent clinical assessments of the nursing infant are important. Available literature does suggest that although the currently available anesthetic and analgesic drugs are transferred in the breast milk, the amounts transferred are almost always clinically insignificant and pose little or no risk to the nursing infant.

Upper airway dimensions in children using rigid video-bronchoscopy and a computer software: description of a measurement technique.

Background:  Pediatric airway management decisions are based primarily on results derived from indirect measures of laryngeal and tracheal dimensions. More recent methods could provide more direct information about absolute and relative changes in airway dimensions associated with growth and development.

Association Between Plasma Cyclic Guanosine Monophosphate Levels and Hemodynamic Instability During Liver Transplantation

The activation of cyclic guanosine monophosphate (cGMP) production in patients with end‐stage liver disease (ESLD) has been associated with hemodynamic instability during orthotopic liver transplantation (OLT). The aim of this prospective, observational study was to investigate the involvement of cGMP in the mediation of profound hypotension during liver graft reperfusion. An additional objective was to determine whether preoperative cGMP levels are associated with intraoperative hemodynamic instability. Forty‐four consecutive patients undergoing OLT were included in the study. Blood samples for cGMP analysis were obtained from (1) the radial artery before the surgical incision; (2) the radial artery, portal vein, and flush blood during the anhepatic phase; and (3) the radial artery 20 minutes after liver graft reperfusion. On the basis of a statistical analysis, the patients were divided into 2 groups: group 1 (preoperative cGMP level ≥ 0.05 μmol/L) and group 2 (preoperative cGMP level < 0.05 μmol/L). We demonstrated a significant correlation between the preoperative levels of cGMP and the amount of catecholamine required to maintain hemodynamic stability during reperfusion (r = 0.52, P < 0.001), the length of the hospital stay (r = 0.38, P = 0.01), and the length of the intensive care unit (ICU) stay (r = 0.44, P = 0.004). We also demonstrated a significantly higher intraoperative catecholamine requirement (P < 0.001) and a prolonged postoperative ICU stay (P = 0.02) in group 1 patients versus group 2 patients. In conclusion, this study demonstrates increased baseline cGMP production in patients with ESLD, which is significantly associated with severe hypotension during OLT. We suggest that preoperative levels of cGMP correlate with hemodynamic instability during liver graft reperfusion. Liver Transpl 19:191–198, 2013.

Analysis of acute pain scores and skin conductance measurements in infants

BACKGROUND Skin conductance (SC) has been previously used to measure acute post-operative pain in adults and older children (>1year old).We have investigated the ability of SC to predict the severity of post-operative pain scores in the exclusively infant population. METHODS Infants (ages 6-12months) scheduled for elective surgery were recruited for the study. Data for behavioral pain scores and SC values - frequency of electrodermal responses per second (EDR/s), peak and basal levels, were recorded in the post-anesthesia care unit (PACU). Blood samples were collected for genomic studies, including single nucleotide polymorphisms (SNP) in morphine opioid receptor (MOR) A118G and the catechol-O-methyltransferase (COMT) G1947A genes. RESULTS 31 infants, mean age 8.9months (±1.9); mean weight 8.5kg (±1.1) were included in the final study analysis. With every 0.1 unit increase in peak values noted on SC, the odds of higher pain scores were found to be 5% greater (p=0.03). For predictability of moderate to severe pain, the area under the curve, sensitivity and specificity were 0.64, 90.9% and 51.4% respectively for peak values and 0.66, 54.5% and 79.4% respectively for EDR/s values. Genotyping performed in 16 out of 31 infants demonstrated that the carriers of MOR 118G allele had consistently higher basal SC values in the PACU. CONCLUSION Peak SC values may serve as indicators of unmitigated pain. Further studies are needed to fully investigate the effect of MOR A118G SNP on the post operative pain scores and SC values in the larger infant population in order to validate both the clinical significance of the skin conductance for routine pain assessment in infants and the observed genetic effect.

Comparison of 2 techniques of laryngeal tube exchange in a randomized controlled simulation study

BACKGROUND Laryngeal tubes (LT) are often used as rescue airway devices. Among prehospital medical personnel, the success rates are high and significantly faster compared to an endotracheal tube (ETT). Therefore, LTs are increasingly used in the prehospital setting. The exchange of an LT for an ETT may often be desirable. Two fiberoptic bronchoscope-facilitated techniques have been described to exchange an LT for an ETT: an intraluminal technique using an Aintree intubating catheter and an extraluminal technique using a nasal route alongside the LT. In this randomized cross-over mannequin study, we compared the intraluminal with the extraluminal exchange technique. The primary outcome was time to achieve an effective airway through an ETT. We hypothesized that the intraluminal technique would be significantly faster. METHODS Thirty anesthesia providers were recruited to the study. Each participant attempted both techniques in an intubation simulation model. The tube exchange time was recorded from picking up the fiberoptic bronchoscope until confirmation of ventilation with the ETT. RESULTS Four participants in each group had a failed attempt at intubation. Time to establish an endotracheal intubation was significantly shorter with the intraluminal technique vs the extraluminal technique (77.5 vs 140 seconds; P=.03). CONCLUSION Based on the results of our study, we suggest that the intraluminal technique may be a suitable alternative for a fiberoptic-guided rapid exchange of an LT for an ETT to establish an effective airway in a challenging situation.

Adverse events and behavioral reactions related to ketamine based anesthesia for anorectal manometry in children

Background:  Pediatric patients undergoing anorectal manometry require ketamine anesthesia as other anesthetic agents affect the anorectal sphincter tone. The aim of this prospective observational audit was to evaluate our practice and report the occurrence of adverse events and behavioral reactions related to the use of ketamine, propofol, and midazolam combinations.

A quality improvement project to reduce hypothermia in infants undergoing MRI scanning

BackgroundHypothermia prevention strategies during MRI scanning under general anesthesia in infants may pose a challenge due to the MRI scanner’s technical constraints. Previous studies have demonstrated conflicting results related to increase or decrease in post-scan temperatures in children. We noted occurrences of post-scan hypothermia in anesthetized infants despite the use of routine passive warming techniques.ObjectiveThe aims of our quality improvement project were (a) to identify variables associated with post-scan hypothermia in infants and (b) to develop and implement processes to reduce occurrence of hypothermia in neonatal intensive care unit (NICU) infants undergoing MRI.Materials and methodsOne hundred sixty-four infants undergoing MRI scanning were prospectively audited for post-scan body temperatures. A multidisciplinary team identified potential variables associated with post-scan hypothermia and designed preventative strategies: protocol development, risk factor identification, vigilance and use of a vacuum immobilizer. Another audit was performed, specifically focusing on NICU infants.ResultsIn the initial phase, we found that younger age (P = 0.002), lower weight (P = 0.005), lower pre-scan temperature (P < 0.01), primary anesthetic technique with propofol (P < 0.01), advanced airway devices (P = 0.02) and being in the NICU (P < 0.01) were associated with higher odds for developing post-scan decrease in body temperature. Quality improvement processes decreased the occurrence of hypothermia in NICU infants undergoing MRI scanning from 65% to 18% (95% confidence interval for the difference, 26-70%, P < 0.001).ConclusionSeveral variables, including being in the NICU, are associated with a decrease in post-scan temperature in infants undergoing MRI scanning under sedation/general anesthesia. Implementation of strategies to prevent hypothermia in infants may be challenging in the high-risk MRI environment. We were able to minimize this problem in clinical practice by applying quality improvement principles.