Browsing by Author "Smith, Johan"
Now showing 1 - 7 of 7
Results Per Page
Sort Options
- ItemA comparison of synthetic surfactants : evaluation of a novel surfactant (1,2-dipalmitoyl-sn-phosphatidycholine and trehalose [C12H22O11]) and comparison with other synthetic formulations(Stellenbosch : Stellenbosch University, 2002-12) Smith, Johan; Coetzee, Andre; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Anaesthesiology and Critical Care .ENGLISH ABSTRACT: The aim of this study was to test a synthetic protein-free surfactant preparation, LPM-l, with the same chemical composition as commercially available Exosurf (Glaxo Wellcome), but containing in addition, a sugar, trehalose (TRE). Towards this end, a study was designed to firstly test the hypothesis that the true difference in acute physiological effects between a mixture of oppe, tyloxapol, hexadecanol and trehalose (LPM-l), and Exosurf, (Oppe, tyloxapol and hexadecanol) is zero, in a surfactantdeficient animal model. A second study addressed the physiological effects of oppe, hexadecanol, tyloxapol and trehalose (LPM-l) compared to treatment with trehalose (TRE) or saline, in order to determine (1) the contribution of TRE to the mixture of oppe, hexadecanol and tyloxapol, and (2) to assess the effect of the LPM-l surfactant replacement on the epithelial lining fluid composition by means of analysing bronchoalveolar lavage fluid. Thirdly, the effects of TRE and / or calcium were studied on the surface properties of oppe suspensions, by in vitro analysis using the ring detachment method of Du Nouy The in vivo research comprised of two studies, performed in randomised controlled fashion. In the first study, 24 New Zealand White adult rabbits were randomised into 4 groups, while in the second study, 15 animals were randomised into 3 groups. In the first in vivo study, three synthetic surfactants, LPM-l, Exosurf and LPM-2, and a saline group were tested. LPM-l is a new formulation that consists ofa mixture of Df'PC, TRE, hexadecanol and tyloxapol. LPM-2 is a formulation with a composition equivalent to that of commercially available Exosurf, prepared on site. In both studies animals were subjected to repeated lavage with large volumes of warm saline (25 ml/kg) in order to establish surfactant deficiency and acute lung injury. Five minutes after the last lavage, vehicle, i.e. surfactants LPM-l, Exosurf, or LPM-2, or saline, in the first in vivo study, and LPM-l, TRE or saline in the second in vivo study, was instilled, and the course of the animals followed over the next 3 hours. Ventilator settings were standardized before and after lavage. The effects of surfactant treatment on gas exchange (arterial Pa02, oxygenation index (Ol), arterial-alveolar oxygen (a/A) ratio), percentage calculated shunt, and total dynamic respiratory compliance (CRSdyn), and histopathological changes were compared with changes in saline treated controls. Arterial blood gases in 100% oxygen and CRSdynwere measured before and after lavage, at 15 minute intervals for the first 30 min, then at 60, 90, 120, and 180 min after vehicle instillation. Oxygenation improved to a similar extent after LPM-l and Exosurf instillation, surpassing that of LPM-2 or saline. Overall, intratracheal instillation of both Exosurf and LPM-l, rapidly improved the gas exchange and reduced the intrapulmonary shunt, but did not restore the lung to its pre-lavage condition. From the 2nd in vivo study it was evident that trehalose-only, was inefficient as a lung surfactant, failing to improve oxygenation indices or the calculated percentage shunt, or influencing respiratory compliance. The addition of the sugar, trehalose (TRE), to the on-site 'Exosurf mixture (LPM-2) brought the activity of the resultant LPM-l to the same level as that of commercial Exosurf, but failed to raise the activity above that of Exosurf. These physiological improvements were sustained for up to 3 hours. Saline-treated animals had no improvement in gas exchange despite management with variable PIP (to maintain a tidal volume of -1 0 ml / kg) and constant PEEP of 5 cm H20. In-vitro results, obtained by the Ou Nouy tensiometer, showed higher mean ordinate surface tension values for the OPPC-only and DPPC + TRE mixtures, and the slopes of their respective graphs smaller in magnitude than those of the other formulations, suggesting that these formulations had less surface tension-lowering capability than the other surfactants. At 20°C (20 mg / ml DPPC-surfactants) the mean ordinate values of OPPC and OPPC + TRE, 70.13 and 69.47 dyne / cm, respectively, were not significantly different from each other. The mean ordinate values of LPM-l and the formulation containing OPPC + TRE + tyloxapol + CaCh were lower, but similar, as were the values of LPM-2 (on-site Exosurf) and LPM-2 + CaCho Thus, three internally homogeneous subgroups could be identified which differed significantly, namely: DPPC and DPPC + TRE, LPM-2 and LPM-2 + CaCh, and DPPC + TRE + tyloxapol + CaCh and LPM-l. Similar conclusions apply to the ordinate values of the surfactants at 37°C, and to the mean slope values at 20°C, with the exception that the subgroups, LPM-2 and LPM-2 + CaCh, and LPM-l and OPPC + TRE + tyloxapol + CaCh are not so clearly separated. A similar analysis of mean slope values was performed. Here too a significant difference between substances was found, OPPC alone or in combination with TRE, again being significantly different from the other surfactants. The most prominent light microscopy findings of the lungs of animals included general lymphatic dilatation, congestion and lung polymorphonuclear infiltration, with no difference between study groups. Hyaline membranes were present in all surfactant groups, but significantly more so in the saline treated group. In the first in vivo study, the presence of neutrophils in the lung interstitiwn as well as alveoli, was a common finding in all of the study groups towards the end of the study protocol. A significant increase in the BAL-fluid neutrophil count occurred in all animals, concurrent with a significant decrease in the BAL macrophage count. No significant change occurred in the peripheral neutrophil count during the 3-hour study, suggesting recruitment of neutrophils from storage pools. Treatment with synthetic surfactant (LPM -1) did not have a significant effect on modifying the inflammatory response, since there was no significant difference in the BAL-derived cell counts between the LPM-1 and -saline groups. Epithelial damage was a consistent finding in all groups. The damage was more evident by electron microscopy examination and included hydropic changes, most readily observed in the mitochondria. The airspaces of study subjects showed the presence of oedema fluid. This luminal oedema appeared to be more prominent in the control group and LPM-2 (on site 'Exosurf') group. Organellar debris, probably originating from lysis of epithelial cells, was present, despite treatment with synthetic surfactant. The electron microscopical appearance of the epithelial-lined substance ("hyaline membranes") in the present study showed a marked variability within groups as well as within the same case. The majority of cases showed a mix of membrane types with both granular and fibrillar materials present within the same membrane. In some cases there were layering of the membranes into distinct bands. The instillation of LPM-l resulted in the formation of a slightly different type of epithelial lining fluid after lavage, when compared to the prelavage composition. The most pronounced changes occurred within the fatty acids, whilst the phosphatidylcholine values remained unchanged. Palmitic acid concentrations (C16:0) increased significantly, suggesting enrichment of the epithelial lining fluid after instillation of LPM-l. This increase in C16:0 was concurrent with significant decreases in the percentage C16:1, C18:0, and C18:2. In contrast to previous studies, we describe higher levels for phosphatidyldimethylethanolarnine (PEA). An explanation may be that the lipid identified as PEA, was in fact partly phosphatidylglycerol (PG)-a lipid whose accurate identification was precluded for technical reasons. After surfactant instillation, the PC/SM ratio, a reflection of the lecithin / sphingomyelin (LIS), decreased significantly in the TRE-group between the first and final lavage, but remained statistically unchanged in the animals treated with LPM-l or saline. The change in ratio was mainly accounted for by a decrease in BAL-fluid PC content together with a rise in SM content. A poor correlation existed between the BAL-derived PC/SM ratio and indices reflecting oxygenation status (a/A ratio, Ol), as well as the CRSdynat the time of the final lavage. In conclusion, the primary hypothesis was accepted, LPM-l performed similarly to Exosurf in vivo, improving oxygenation, but not CRSdyn.None was clearly superior to the other. Some questions remain. The reason why LPM-l (LPM-2 + TRE) did not behave in a superior manner, in vivo, to Exosurf, is partly unclear. This finding was somewhat surprising since the chemical composition of Exosurf and LPM-2 did not differ, and the addition of TRE to LPM-2 (on-site Exosurf), did improve the in vivo activity of the resultant LPM-l, above that of LPM-2. A possible explanation for observed differences in performance include methodological issues, i.e. the preparation of the on-site formulations, especially that of LPM-2 (on-site Exosurf), may differ from the way in which true commercial Exosurf is prepared.
- ItemDeposition and transport of linezolid mediated by a synthetic surfactant Synsurf® within a pressurized metered dose inhaler : a Calu-3 model(Dove Medical Press, 2018) Van Rensburg, Lyne; Van Zyl, Johann M.; Smith, JohanBackground: Previous studies in our laboratory demonstrated that a synthetic peptide containing lung surfactant enhances the permeability of chemical compounds through bronchial epithelium. The purpose of this study was to test two formulations of Synsurf® combined with linezolid as respirable compounds using a pressurized metered dose inhaler (pMDI). Methods: Aerosolization efficiency of the surfactant-drug microparticles onto Calu-3 monolayers as an air interface culture was analyzed using a Next Generation Impactor™. Results: The delivered particles and drug dose showed a high dependency from the preparation that was aerosolized. Scanning electron microscopy imaging allowed for visualization of the deposited particles, establishing them as liposomal-type structures (diameter 500 nm to 2 µm) with filamentous features. Conclusion: The different surfactant drug combinations allow for an evaluation of the significance of the experimental model system, as well as assessment of the formulations providing a possible noninvasive, site-specific, delivery model via pMDI.
- ItemEffect of exogenous surfactant on Paediatric Bronchoalveolar lavage derived macrophages’ cytokine secretion(BMC (part of Springer Nature), 2019-12-05) Van Rensburg, Lyne; Van Zyl, Johann M,; Smith, Johan; Goussard, PierreBackground: Bronchoalveolar lavage is a useful bronchoscopy technique. However, studies in “normal” children populations are few. Furthermore, the anti-inflammatory effects of exogenous pulmonary surfactants on the bronchoalveolar cellular components are limited. Methods: Thirty children, aged 3 to 14 years, underwent diagnostic bronchoscopy and bronchoalveolar lavage. Differential cytology, cytokine and chemokine measurements were performed on the fluid after exogenous surfactant exposure. The aim of the study was to investigate the potential anti-inflammatory effects of exogenous surfactants on the bronchoalveolar lavage fluid, specifically alveolar macrophages of healthy South African children. Results: Alveolar macrophages were the predominant cellular population in normal children. Patients with inflammatory pneumonopathies had significantly more neutrophils. Levels of inflammatory cytokines were significantly lower after exogenous surfactant exposure. Moreover, IL-10 and IL-12 cytokine secretion increased after exogenous surfactant exposure. Conclusion: This study provides the first data on bronchoalveolar lavage of healthy South African children. Bronchoalveolar lavage fluid from patients with pulmonary inflammation was characterised by neutrophilia. Finally, we propose that exogenous surfactant treatment could help alleviate inflammation in diseased states where it occurs in the tracheobronchial tree.
- ItemImpact of pulsed xenon ultraviolet disinfection on surface contamination in a hospital facility’s expressed human milk feed preparation area(BioMed Central, 2018-02-23) Dippenaar, Ricky; Smith, JohanBackground; Expressed human milk (EHM) feed preparation areas represent a potential source of unintentional nosocomial infection. Daily disinfection of environmental surfaces remains an essential intervention to mitigate nosocomial infections. The inefficiency of conventional cleaning and disinfection contributes to an increased risk for the acquisition of multi-drug resistant pathogens. “Non touch” technologies such as the pulsed xenon ultraviolet (PX-UVD) light device have documented sustained reduction in surface bacterial colonization and reduced cross contamination. Methods: The impact of a PX-UVD on surface colony forming units per square centimeter (cfu/cm2) in feed preparation areas was evaluated following its implementation as standard care. A quasi-experimental study was performed documenting bacterial colonization from 6 high risk feed preparation areas in a community care hospital in South Africa. Pre and post conventional cleaning neutralizing rinse swabs were collected fortnightly over a 16 week control period prior to the introduction of the PX-UVD and compared to a matching set of samples for the PX-UVD period. Results: A 90% reduction in total surface bioburden was noted from the control period (544 cfu/cm2) compared to the corresponding PX-UVD period (50 cfu/cm2). Sub -analysis of both the Pre-clean Control: Pre-clean PX-UVD counts as well as the Post-clean Control: Post-clean PX-UVD counts noted significant improvements (p < 0.001). A statistically significant improvement was noted between pre-and post-cleaning total surface bioburden following exposure to the PX-UVD (p = 0.0004). The introduction of the PX-UVD was associated with a sustained reduction in the pre clean bioburden counts with a risk trend (per week) 0.19, (95% CI [0.056, 0.67], p = 0.01). Discussion: The use of a PX-UVD as adjunct to standard cleaning protocols was associated with a significant decrease in surface bioburden. The study demonstrated the inefficiency of conventional cleaning. Persistence of potentially pathological species in both periods highlights current health sector challenges.
- ItemIntracardiac air - the 'hospital killer' identified? Case reports and review of the literature(Health & Medical Publishing Group, 2003) Smith, Johan; Els, IlseVenous access is an essential part of caring for the sick neonate. The primary problem with catheters, whether peripherally or centrally placed, is the difficulty in maintaining them, the development of phlebitis and systemic infection, and fluid extravasation. A lesser known complication is the development of venous air embolism (VAE), as described in the 4 cases presented. We agree with others that VAE in newborn infants may occur more frequently than expected and emphasise the fact that it is preventable and that careful attention must be given to the techniques of preparing venous infusions. As health professionals (medical and nursing) we should take a harder line and regard these events as medically negligent until proven otherwise. We should take full responsibility for equipment, the connections, the infusate and the monitoring thereof. Unfortunately, the prognosis for this condition remains poor and it is unclear whether an increased awareness of this condition would influence outcome. Manufacturers of intravenous fluids should produce products devoid of air in order to reduce the risk of venous air embolism.
- ItemIntracranial complications of Serratia marcescens infection in neonates(Health & Medical Publishing Group, 2016) Madide, Ayanda; Smith, JohanEven though Serratia marcescens is not one of the most common causes of infection in neonates, it is associated with grave morbidity and mortality. We describe the evolution of brain parenchymal affectation observed in association with S. marcescens infection in neonates. This retrospective case series details brain ultrasound findings of five neonates with hospital-acquired S. marcescens infection. Neonatal S. marcescens infection with or without associated meningitis can be complicated by brain parenchymal affectation, leading to cerebral abscess formation. It is recommended that all neonates with this infection should undergo neuro-imaging more than once before discharge from hospital; this can be achieved using bedside ultrasonography.
- ItemThe management of persistent pulmonary hypertension of the newborn : a review(Health & Medical Publishing Group, 2016-12-14) Lloyd, Lizel Georgi; Smith, JohanPersistent pulmonary hypertension of the newborn is a neonatal emergency with a high mortality rate in spite of several advances in the management thereof. The underlying pathophysiology is complex and multifactorial. The gold standard of treatment is inhaled nitric oxide, yet up to a third of patients will not respond to standard treatment. This article reviews treatment modalities available, as well as the evidence to support the use of these treatment options.