Orthodeoxia--an uncommon presentation following bilateral thoracic sympathectomy.

We present a case of orthodeoxia (postural hypoxaemia) which resulted from a combination of lung collapse/consolidation and blunted hypoxic pulmonary vasoconstriction due to partial interruption of the sympathetic nerve supply to the lung by bilateral thoracic sympathectomy.

Tracheal foreign body following tube change during percutaneous dilational tracheostomy: a cautionary tale.

Although studies have shown percutaneous dilational tracheostomy to be a safe and cost-effective alternative to conventional surgical tracheostomy, there are inherent risks and complications. We report an incident occurring during percutaneous dilational tracheostomy using the Portex technique, in which a significant cuff leak occurring on insertion of the tracheostomy tube necessitated an immediate tube change. During this latter procedure, using a fresh Portex kit and guidewire, the guidewire introducer became dislodged from the guidewire assembly and inadvertently impacted in the trachea. Routine bronchoscopy identified the hazard and the foreign body was successfully removed via the bronchoscope with no adverse sequelae.

Validation of Tu's cardiac surgical risk prediction index in a Western Australian population.

Tu's cardiac surgical risk prediction index for a Western Australian population was examined in a prospective observational cohort study. Risk score and outcome data were collected for 367 consecutive patients. Logistic regression analysis for Tu score prediction of hospital mortality and linear regression analysis for prediction of ICU and hospital stays were performed. The Tu index accurately predicted mortality rates (P = 0.002, odds ratio 1.46). The linear regression analyses of Tu score on ICU and hospital stays showed an excellent fit (P = 0.0001). The area under the receiver-operating characteristic curve for prolonged ICU stay was 0.75. The Tu risk index is valid for a Western Australian cardiac surgical population and practice.

Contamination of propofol infusions in the intensive care unit: incidence and clinical significance.

Epidemics of bacteraemia and wound infection have been associated with the infusion of bacterially contaminated propofol administered during anaesthesia. We conducted an observational study to determine the incidence and clinical significance of administration of potentially contaminated propofol to patients in an ICU setting. One hundred patients received a total of 302 infusions of propofol. Eighteen episodes of possible contamination of propofol syringes were identified, but in all cases contamination was by a low-grade virulence pathogen. There were no episodes of clinical infection or colonization which could be attributed to the administration of contaminated propofol. During the routine use of propofol to provide sedation in ICU patients the risk of nosocomial infection secondary to contamination of propofol is extremely low.

Bronchoscopic insufflation of room air for the treatment of lobar atelectasis in mechanically ventilated patients.

Segmental and lobar pulmonary atelectasis is a common occurrence in mechanically ventilated patients. Standard therapy for atelectasis relies on positive pressure ventilation, positive and expiratory pressure (PEEP), tracheobronchial toilet and regular chest physiotherapy. Various adjuncts to physiotherapy such as bronchoscopic clearance of secretions have not proved to be of additional benefit. Bronchoscopic clearance of secretions followed by insufflation of room air at 30 cm H2O into the atelectatic segment was employed on ten occasions in mechanically ventilated patients. Rapid re-expansion of the collapsed segment or lobe occurred in seven out of the ten treatments.

Death by tanning--a case of fatal basic chromium sulphate poisoning.

A woman ingested 400 ml of leather tanning solution containing 48 g of basic chromium sulphate (CrOHSO4). This substance forms hydrogen ions and trivalent chromium when it reacts with tissue proteins. The patient died of cardiogenic shock, complicated by pancreatitis and gut mucosal necrosis and haemorrhage. There are no reported cases of toxicity due to oral ingestion of trivalent chromium. Toxicity of hexavalent and trivalent chromium is discussed and suggestions made for management of future cases.

Cerebrospinal fluid lactate in meningitis and meningococcaemia.

Cerebrospinal fluid (CSF) lactate values were measured in 26 children with meningitis (12 bacterial, 9 aseptic, 5 partially treated) and five children with meningococcaemia without meningitis. A reference range (0.5-3.2 mmol/l) was established from 100 control children. Amounts of lactate were significantly raised in bacterial meningitis (mean 6.5, range 4.5-10.2) compared with aseptic meningitis (mean 2.6, range 1.1-4.0) but this finding gave little practical help as the bacterial origin of the meningitis was clear from other CSF findings. High values (5.7) in a case of tuberculous meningitis (TBM) suggest that the test may be helpful when other CSF findings are inconclusive. Unless the CSF lactate is raised, the test is of minimal value in partially treated meningitis (mean 3.4, range 1.4-6.2). The previously unobserved finding of increased CSF lactate in meningococcaemia without meningitis (mean 3.9, range 3.1-5.0) supports the view that raised CSF lactate values in bacterial meningitis are not solely due to the presence of neutrophils. Literature relating to CSF lactate is reviewed.

Herpes simplex virus encephalitis: problems in diagnosis.

Six children aged 13 days to nine years with herpes simplex encephalitis (HSE) are presented. Institution of appropriate antiviral treatment was later than six days in three cases; original diagnosis in these cases were post-traumatic epilepsy, bacterial meningitis and febrile convulsion. Initially pyrexia was absent in two cases and cranial CT was normal in two cases. Encephalitic changes were observed on the EEGs of five children. Diagnosis was confirmed by paired serological titres, brain biopsy, vesicle culture and CSF titres. The outcome for all six children was poor. HSE should always be considered in children presenting with focal seizures, even when apyrexial and with normal CT findings. In such situations, saving CSF for antibody titres or antigen identification should be routine practice. Treatment with acyclovir is justified before precise virological diagnosis has been established.

Sialic acid storage disease.

A baby girl with coarse facial features, hepatosplenomegaly, and developmental delay had raised free sialic acid concentrations in her urine and cultured fibroblasts. She died aged 13 months. Sialic acid is an important constituent of many glycoproteins and glycolipids; impaired release from the lysosome may be the underlying biochemical defect.

Quantification of thoracic volumes by three-dimensional imaging.

End-expiratory thoracic cavity volume (Vthx) was measured in eight volunteers lying supine by three-dimensional X-ray computed tomography using the Dynamic Spatial Reconstructor. Untrapped end-expiratory pulmonary gas volume at functional residual capacity (FRC) was determined by nitrogen clearance. Both measurements were done before and after induction of anesthesia-paralysis. After induction of anesthesia-paralysis, Vthx and FRC were consistently and significantly (P less than 0.01) reduced by 0.28 +/- 0.22 (SD) and 0.59 +/- 0.24 liter, respectively. The reduction of FRC was larger than the reduction of Vthx (delta Vthx) in six of the eight subjects, a finding suggesting that intrathoracic fluid (blood) plus trapped gas volume (Vtt) increased. Changes in Vthx were partitioned into volume changes from the thoracic rib cage (delta Vrc) and from shape and/or position changes of the diaphragm (delta Vdi). delta Vrc contributed significantly (0.17 +/- 0.15 liter, P less than 0.02) to delta Vthx, whereas delta Vdi contributed only in four of the eight subjects. We conclude that delta Vrc, delta Vdi, and delta Vtt contribute to the reduction of FRC after induction of anesthesia-paralysis in humans; the relative contribution of them varies among subjects.

Newer modes of mechanical ventilatory support.

Recent modes of ventilatory support aim to facilitate weaning and minimise the physiological disadvantages of intermittent positive pressure ventilation (IPPV). Intermittent mandatory ventilation (IMV) allows the patient to breathe spontaneously in between ventilator breaths. Mandatory minute volume ventilation (MMV) ensures that the patient always receives a preset minute volume, made up of both spontaneous and ventilator breaths. Pressure supported (assisted) respiration is augmentation of a spontaneous breath up to a preset pressure level, and is different from 'triggering', which is a patient-initiated ventilator breath. Other modes or refinements of IPPV include high frequency ventilation, expiratory retard, differential lung ventilation, inversed ratio ventilation, 'sighs', varied inspiratory flow waveforms and extracorporeal membrane oxygenation. While these techniques have useful applications in selective situations, IPPV remains the mainstay of managing respiratory failure for most patients.

Pharmacokinetics of ranitidine in critically ill patients.

The plasma pharmacokinetics of ranitidine (50 mg i.v.) have been studied in 17 critically ill patients in an intensive care unit. Measurements of gastric aspirate pH were also made in 16 of these patients. Ranitidine therapy was part of the patients' normal drug regimen. Ranitidine plasma concentration was measured by high performance liquid chromatography and appropriate polyexponential equations were fitted to concentration-time data to enable calculation of relevant pharmacokinetic parameters. Values of the volume of the initial dilution space (median = 89 ml kg-1) and volume of distribution at steady state (median = 1.54 l kg-1) were about 60% of corresponding mean literature values for healthy controls. Plasma clearance (median = 4.22 ml min-1 kg-1) and terminal half-life (median = 4.7 h) were about 2-3 fold less and 2-3 fold greater, respectively, than values for healthy controls. There was wide interpatient variation in all the pharmacokinetic parameters. Renal impairment was considered to be largely responsible for the low plasma clearance. Gastric aspirate pH was measured at 0, 1 and 7 h after ranitidine administration and 58% of samples were found to be above pH 4. Four patients had gastric pH values which were consistently below pH 4 despite average trough plasma ranitidine concentrations equal to or greater than those required for a 50% suppression of gastric acid secretion in normal volunteers.

A comparison of continuous flush devices.

Six different makes of continuous flush device were compared for reliability of flow rate and ease of use. All of the devices tested were considered suitable for flushing of vascular pressure monitoring catheters. However, flow rates were considered too variable for control of drug infusions or flushing of intracranial pressure monitoring systems.

Pressure infusors: variability in delivered infusion pressure.

A pressure infusor was used to apply external pressures of 300, 250, 200, and 150 mm Hg to 500-ml plastic bags of saline. At constant applied pressure, 50-ml aliquots of saline were periodically withdrawn. The delivered pressures were less than the applied pressures, and the difference increased as the volume of saline within the bag decreased. This inherent pressure difference should be considered when the system is used with a continuous flush device.

Effect of long-term continuous infusion of alfathesin on clinical biochemical and haematological parameters.

Clinical biochemical and haematological parameters during long-term continuous infusion of alfathesin were studied in twelve neurosurgical patients who did not have multiple organ failure. Significant changes which were possibly caused by alfathesin were an alteration of blood film morphology, an elevation of plasma triglyceride and a reduction in plasma high-density lipids.

A multiple-purpose automatic pressure regulator.

The Gairdner Hospital Automatic Pressure Regulator was developed to deliver a constant pre-set gas pressure for the continuous inflation of infusion pump cuffs or pneumatic tourniquets. It has been found to be economical, safe, reliable and easy to use. The device facilitates both continuous flushing of catheters and rapid intravenous infusions especially during emergency situations. It may also be used in other clinical situations where a continuous gas supply at a pre-set constant pressure is required.