Mary Lieh-Lai

Drug complexation, in vitro release and cellular entry of dendrimers and hyperbranched polymers

Highly branched, functionalized polymers have potential to act as efficient drug carrier systems. Dendrimers are ideal candidates among model hyperbranched polymers because of their well-defined structure and high density of functional groups. Using ibuprofen as a model drug, we studied the interaction between the drug and Polyamidoamine (PAMAM) dendrimers (generations 3 and 4 with --NH2 functionality) and Perstrop Polyol (generation 5, hyperbranched polyester with --OH functionality). FTIR and NMR studies suggest that ibuprofen predominantly forms a complex with PAMAM dendrimers because of the ionic interaction between the --NH2 end groups and the carboxyl group of ibuprofen. On an average, up to 78 molecules of ibuprofen could be incorporated into one molecule of PAMAM-G4-NH2 with 64 end groups. This complex is stable in deionized water and methanol. The in vitro release of ibuprofen from drug-dendrimer complex is appreciably slower compared to pure ibuprofen. The complexed drug enters A549 cells much more rapidly than pure drug suggesting that dendrimers may be able to carry the complexed drug inside cells efficiently. Hyperbranched Polyol (with 128 --OH end groups) appears to encapsulate approximately 24 drug molecules. Perhaps the lack of strong interactions between the --OH end groups and the drugs prevents complex formation.

Aerosolized ribavirin in mechanically ventilated children with respiratory syncytial virus lower respiratory tract disease: a prospective, double-blind, randomized trial.

ObjectiveTo study the effect of ribavirin aerosol therapy on the immediate clinical course of mechanically ventilated children with respiratory syncytial virus lower respiratory tract disease. DesignProspective, randomized, double-blind, placebo-controlled study. SettingPediatric intensive care unit (ICU) of a university teaching hospital.Patients: Forty-one children requiring mechanical ventilation for respiratory syncytial virus lower respiratory tract disease. InterventionsPatients were stratified by the presence or absence of and underlying disease and then randomized to receive aerosolized ribavirin (20 mg/mL) or saline for 18 hrs/day for 5 days or until endotracheal extubation, whichever came first. Measurements and Main ResultsDependent variables included the time course of the illness and the change in FIO2, ventilatory rate, Pao2/FIO2A ratio, and ventilatory-efficiency index of patients while they received aerosol therapy. Ribavirin- and placebo-treated patient groups were not significantly different in the number of ventilator days (6.4 pL 6.9 vs. 8.2 pL 10.1; p = .5), oxygen days (10.8 pL 7.7 vs. 12.2 pL 11.8; p = .9), ICU days (7.9 pL 7.0 vs. 10.3 pL 11.0; p = .7), or hospitaldays (12.9 pL 9.7 vs. 16.2 pL 14.0; p = .6) after the initiation of aerosol therapy. The change in Fio2, ventilatory rate, Pao2/FIO2 ratio, or ventilatory-efficiency index did not differ between the two groups. No ventilator malfunction was observed. There were six deaths caused by intractable hypoxemia in patients with underlying cardio-pulmonary disease. Four of these deaths were in the placebo group and two in the ribavirin group (p = .5). ConclusionsRibavirin aerosol therapy can be safely administered to mechanically ventilated children with severe respiratory syncytial virus lower respiratory tract disease. However, this therapy does not appear to affect immediate clinical outcome in such patients. (Crit Care Med 1994; 22:566–572)

Limitations of the Glasgow Coma Scale in predicting outcome in children with traumatic brain injury

OBJECTIVE To study the hypothesis that, in the absence of an ischemic-hypoxic state, children with severe traumatic brain injury and with unfavorable Glasgow Coma Scale scores may have good recovery. DESIGN Retrospective, observational, cross-sectional study with factorial design. SETTING Inpatient population in a university hospital. PATIENTS Seventy-nine children with traumatic brain injury admitted to the intensive care unit. INTERVENTIONS All patients received close monitoring and strict control of intracranial pressure (less than 20 mm Hg) and cerebral perfusion pressure (greater than 60 mm Hg). MEASUREMENTS AND RESULTS Admission Glasgow Coma Scale score, survival, need for cardiopulmonary resuscitation, presence of shock, peak intracranial pressure, duration of coma, Glasgow Outcome Scale score, and the results of neuropsychologic tests were analyzed. Of 79 children, 70 (89%) survived. Although the mortality rate was higher among patients with Glasgow Coma Scale scores of 3 to 5, 14 (64%) of 22 of these children survived. Nonsurvivors had a significantly higher incidence of shock and need for cardiopulmonary resuscitation. Except for two patients who had prolonged hypoxemia, all children, including those with Glasgow Coma Scale scores of 3 to 5, had a satisfactory outcome (Glasgow Outcome Scale scores of 4 or 5). Neuropsychologic outcome was not significantly different in the survivors with Glasgow Coma Scale scores of 3 to 5 and those with Glasgow Coma Scale scores of 6 or more. CONCLUSIONS A low Glasgow Coma Scale score does not always accurately predict the outcome of severe traumatic brain injury; in the absence of hypoxic-ischemic injury, children with traumatic brain injury and Glasgow Coma Scale scores of 3 to 5 can recover independent function.

Hyperbranched Polymer-Drug Conjugates with High Drug Payload for Enhanced Cellular Delivery

No HeadingPurpose.To synthesize and evaluate hyperbranched polymer (HBP)-drug conjugates with high drug payload for enhanced cellular delivery.Methods.Polyol- and polyglycerol-ibuprofen conjugates with or without imaging agent fluorescein isothiocyanate (FITC) were synthesized using dicyclohexilcarbodiimide (DCC) as a coupling agent. Drug-polymer conjugates were characterized using 13C NMR, 1H NMR, and gel permeation chromatography (GPC). Stability of the drug-conjugates was studied using free drug release through a dialysis membrane. Cellular entry of FITC-labeled HBP conjugates was studied using fluorescence activated cell sorter (FACS), and cell supernatant was analyzed by UV-visible spectrophotometer. The intracellular localization of FITC-labeled conjugates in A549 lung epithelial cells was imaged using fluorescence microscopy. Anti-inflammatory activity of the HBP-ibuprofen conjugates was estimated in vitro by measuring the concentration of prostaglandin (PGE2) using an ELISA kit.Results.The average number of ibuprofen molecules conjugated per molecule of HBP was estimated to be 50 for polyol and 53 for polyglycerol. The HBP-drug conjugates did not release the drug up to 72 h in methanol, indicating the presence of stable ester bonds. Both the polymer-drug conjugates entered the cells rapidly. The conjugates were localized in the cell cytosol as evidenced by fluorescence microscopy. Within 30 min, the HBP-drug conjugates showed rapid suppression of PGE2 synthesis, whereas free ibuprofen did not show any activity. At later times, the conjugates showed comparable activity.Conclusions.For the first time, we report HBP conjugates with a high drug payload. HBP-drug conjugates entered the cells rapidly and produced the desired pharmacological action. This study demonstrates that hyperbranched polyol and polyglycerol are promising nanovehicles for achieving enhanced cellular delivery of drugs.

Predicting outcome in children with severe acute respiratory failure treated with high-frequency ventilation

OBJECTIVES a) To demonstrate the effect of high-frequency ventilation on gas exchange in children with severe acute respiratory failure unresponsive to conventional ventilation; b) to identify patients at high risk of death early after institution of high-frequency ventilation. SETTING Tertiary care pediatric intensive care unit in a university hospital. DESIGN A cross-sectional, observational study with factorial design. PATIENTS Thirty-one patients with severe acute respiratory failure defined as a Pao2/F1o2 of < 150 torr (< 20 kPa) with a positive end-expiratory pressure of > or = 8 cm H2O and/or Paco2 of > 60 torr (> 8 kPa) with an arterial pH < 7.25. INTERVENTIONS Patients received either high-frequency oscillation or jet ventilation if respiratory failure was unresponsive to conventional ventilation and if the underlying disease process was deemed reversible. MEASUREMENTS AND MAIN RESULTS Thirty-one children were managed with high-frequency ventilation, 11 children with jet and 20 children with oscillator. Arterial blood gases and level of ventilatory support were recorded before and at 6, 24, 48, 72, and 96 hrs after institution of high-frequency ventilation. There was an improvement in an arterial pH, Paco2, Pao2, and Pao2/FID2 6 hrs after institution of high-frequency ventilation (p < .01). This improvement, along with decreased need for oxygen, was sustained through the subsequent course. Twenty-three (74%) of 31 children treated with high-frequency ventilation survived. Survivors showed an increase in an arterial pH, Pao2, Pao2/FIO2, and a decrease in Paco2 within 6 hrs, whereas nonsurvivors did not. Oxygenation index was the best predictor of outcome. A combination of an initial oxygenation index of > 20 and failure to decrease the oxygenation index by > 20% by 6 hrs after initiation of high-frequency ventilation predicted death with 88% (7/8) sensitivity and 83% (19/23) specificity, with an odds ratio of 33 (p = .0036, 95% confidence interval 3-365). CONCLUSIONS In patients with potentially reversible underlying diseases resulting in severe acute respiratory failure that is unresponsive to conventional ventilation, high-frequency ventilation improves gas exchange in a rapid and sustained fashion. The magnitude of impaired oxygenation and its improvement after high-frequency ventilation can predict outcome within 6 hrs.

Intracranial pressure and cerebral perfusion pressure in near-drowning

Intracranial pressure (ICP) and cerebral perfusion pressure (CPP) were strictly controlled in 11 pediatric victims of near-drowning. Three outcome groups were defined: complete recovery, persistent vegetative state, and death. In the early postimmersion phase (first 72 h), CPP was consistently above 50 mm Hg in all patients. There were occasional, nonrepetitive, and easily controllable ICP spikes above 15 mm Hg in three patients from each group. Repeated ICP spikes above 15 mm Hg were observed in some patients with adverse outcome only after 72 h. Successful control of ICP and CPP did not ensure intact survival, and sustained late intracranial hypertension is more likely a sign of pro-found neurologic insult rather than its cause.

A randomized comparison of ketorolac tromethamine and morphine for postoperative analgesia in critically ill children

OBJECTIVES To evaluate the efficacy of a single dose of ketorolac compared with morphine for the relief of pain in children, and to determine the safety of ketorolac. SETTING Tertiary pediatric intensive care unit in a university-affiliated hospital. DESIGN Prospective, randomized, double-blind, parallel, single-dose, positive control study. PATIENTS Children admitted to the intensive care unit with postoperative pain. INTERVENTIONS Patients received a single dose of either morphine or ketorolac as the first postoperative analgesic when the pain score indicated significant pain. Blood pressure, heart rate, and urine output were recorded, as well as blood urea nitrogen, creatinine, bleeding time, hematuria or proteinuria, and aspartate aminotransferase. Side effects such as nausea and vomiting were noted. Morphine was used for rescue treatment if the patient continued to have significant pain > or =30 mins after study drug administration. MEASUREMENTS AND MAIN RESULTS Of the 102 children studied, 48 received morphine and 54 received ketorolac. The percentage of patients reporting pain relief in the first and second hours after drug administration was not different between groups. Likewise, the proportion of patients who met the criteria for pain relief during the entire evaluation period was not different between groups. There was a trend toward fewer patients who received ketorolac requiring remedication in the first 4 hrs compared with those who received morphine, but this trend did not reach statistical significance. More patients in the morphine group failed to achieve pain relief at any time after the dose compared with those who received ketorolac. There were no differences between the two groups in physiologic or laboratory variables. Vomiting was more common in patients who received ketorolac. CONCLUSION Ketorolac is comparable to morphine in relief of postoperative pain in children. A single dose of ketorolac does not result in abnormal postoperative bleeding or alter renal function. However, ketorolac may cause nausea and vomiting in some patients.

Enantiomer‐selective pharmacokinetics and metabolism of ketorolac in children

To compare the pharmacokinetics and metabolism of R (+)‐ and S (−)‐ ketorolac in children.

In vivo efficacy of dendrimer–methylprednisolone conjugate formulation for the treatment of lung inflammation

Dendrimers are an emerging class of nanoscale intracellular drug delivery vehicles. Methylprednisolone (MP) is an important corticosteroid used in the treatment (through inhalation) of lung inflammation associated with asthma. The ability of MP-polyamidoamine (PAMAM) dendrimer conjugate to improve the airway delivery was evaluated in a pulmonary inflammatory murine model that was based on an 11-fold enhancement of eosinophil lung accumulation following five daily inhalation exposures of sensitized mice to the experimental allergen, ovalbumin. MP was successfully conjugated to PAMAM-G4-OH dendrimer yielding 12 MP molecules per dendrimer, and further solubilized in lysine carrier. Five daily trans-nasal treatments with the carrier alone, free MP, and MP-dendrimer at 5 mg kg(-1) (on a drug basis) did not induce additional lung inflammation, although free MP decreased baseline phagocytic cell recoveries by airway lavage and tissue collagenase dispersion. MP treatments alone decreased ovalbumin-associated airway and tissue eosinophil recoveries by 71 and 47%, respectively. Equivalent daily MP dosing with MP-dendrimer conjugate further diminished these values, with decreases of 87% and 67%, respectively. These findings demonstrate that conjugation of MP with a dendrimer enhances the ability of MP to decrease allergen-induced inflammation, perhaps by improving drug residence time in the lung. This is supported by the fact that only 24% of a single dose of dendrimer delivered to the peripheral lung is lost over a 3-day period. Therefore, conjugation of drugs to a dendrimer may provide an improved method for retaining drugs within the lung when treating such inflammatory disorders as asthma.

Pressure-controlled ventilation in children with severe status asthmaticus.

Objective The optimum strategy for mechanical ventilation in a child with status asthmaticus is not established. Volume-controlled ventilation continues to be the traditional approach in such children. Pressure-controlled ventilation may be theoretically more advantageous in allowing for more uniform ventilation. We describe our experience with pressure-controlled ventilation in children with severe respiratory failure from status asthmaticus. Design Retrospective review. Setting Pediatric intensive care unit in a university-affiliated children’s hospital. Patients All patients who received mechanical ventilation for status asthmaticus. Interventions Pressure-controlled ventilation was used as the initial ventilatory strategy. The optimum pressure control, rate, and inspiratory and expiratory time were determined based on blood gas values, flow waveform, and exhaled tidal volume. Measurement and Main Results Forty patients were admitted for 51 episodes of severe status asthmaticus requiring mechanical ventilation. Before the institution of pressure-controlled ventilation, median pH and Pco2 were 7.21 (range, 6.65–7.39) and 65 torr (29–264 torr), respectively. Four hours after pressure-controlled ventilation, median pH increased to 7.31 (6.98–7.45, p < .005), and Pco2 decreased to 41 torr (21–118 torr, p < .005). For patients with respiratory acidosis (Pco2 >45 torr) within 1 hr of starting pressure-controlled ventilation, the median length of time until Pco2 decreased to <45 torr was 5 hrs (1–51 hrs). Oxygen saturation was maintained >95% in all patients. Two patients had pneumomediastinum before pressure-controlled ventilation. One patient each developed pneumothorax and subcutaneous emphysema after initiation of pressure-controlled ventilation. All patients survived without any neurologic morbidity. Median duration of mechanical ventilation was 29 hrs (4–107 hrs), intensive care stay was 56 hrs (17–183 hrs), and hospitalization was 5 days (2–20 days). Conclusions Based on this retrospective study, we suggest that pressure-controlled ventilation is an effective ventilatory strategy in severe status asthmaticus in children. Pressure-controlled ventilation represents a therapeutic option in the management of such children.