Pre-oxygenation in healthy volunteers: a comparison of the supine and 45° seated positions*.

Pre-oxygenation in the seated (sitting) position has been associated with better oxygenation. This randomised, cross over study compared oxygenation in the supine position with that in the 45° seated position in 40 young, healthy volunteers. Oxygen was administered through a circle system and tight fitting facemask. Transcutaneous P(O)2 levels were recorded at 10-s intervals from two measurement points during 4 min of oxygenation in the two positions. The mean (SD) values of 12 measurements taken between the third and fourth minute were recorded. There was no difference in the increase in tissue oxygenation when comparing the supine and seated positions (32.7 (7.3) vs 32.6 (6.7) kPa, respectively). We conclude that there is no evidence that pre-oxygenation in the 45° seated position improves tissue oxygenation in young healthy volunteers compared with the supine position.

The cardiovascular effects of normobaric hyperoxia in patients with heart rate fixed by permanent pacemaker.

To investigate whether the established reductions in heart rate and cardiac output with hyperoxia in humans are primary effects or secondary to increases in systemic vascular resistance, we paced the hearts of nine patients with permanent pacemakers at a fixed rate when breathing either medical air (inspired O(2) fraction 0.21) or oxygen (inspired O(2) fraction 0.80) in a randomised, double-blind fashion. A thoracic bio-impedance machine was used to measure heart rate, stroke volume and blood pressure and calculate cardiac index and systemic vascular resistance index. Oxygen caused no change in cardiac index (p = 0.18), stroke index (p = 0.44) or blood pressure (p = 0.52) but caused a small (5.5%) increase in systemic vascular resistance index (p = 0.03). This suggests that hyperoxia has no direct myocardial depressant effects, but that the changes in cardiac output reported in previous studies are secondary to changes in systemic vascular resistance.

Effect of intraoperative fluid optimisation on renal function in patients undergoing emergency abdominal surgery: a randomised controlled pilot study (ISRCTN 11799696).

BACKGROUND: Emergency abdominal surgery carries a high risk of postoperative morbidity and mortality. Goal directed therapy has been advocated to improve outcome in high-risk surgery. The aim of the present pilot study was to examine the effect of goal directed therapy using fluid alone on postoperative renal function and organ failure score in patients undergoing emergency abdominal surgery. METHODS: This prospective randomised pilot study included patients over the age of 50 undergoing emergency abdominal surgery. In the intervention group pulse pressure variation measurements were used to guide fluid boluses of 6% Hydroxyethylstarch 130/0.4. The control group received standard care. Serum urea, creatinine and cystatin C levels were measured prior to and at the end of surgery and postoperatively on day 1, day 3 and day 5. RESULTS: Thirty patients were recruited. One patient died prior to surgery and was excluded from the analysis. The intervention group received a median of 750 ml of hydroxyethylstarch. The peak values of postoperative urea were 6.9 (2.7-31.8) vs. 6.4 (3.5-11.5)mmol/l (p=0.425), creatinine 100 (60-300) vs. 85 (65-150) micromol/l (p=0.085) and cystatin C 1.09 (0.66-4.94) vs. 1.01 (0.33-2.29)mg/dl (p=0.352) in the control and intervention group, respectively. CONCLUSIONS: In the present pilot study replacing the identified fluid deficit was not associated with a change in renal function. These results do not preclude that goal directed therapy using fluid alone may have an effect on renal function but they would suggest that the effect size of fluid optimisation alone on renal function is small.

Cardiovascular changes after achieving constant effect site concentration of propofol.

Target controlled infusions of propofol use a pharmacokinetic/pharmacodynamic model to calculate an effect site concentration of the drug. We assessed the cardiovascular stability of 10 healthy patients using non-invasive thoracic bioimpedance and their 'depth' of anaesthesia using the Bispectral index after they had been anaesthetised to a constant effect site concentration of propofol (6.5 min from starting). Each patient had no surgical stimulus and received no intravenous fluid during the study period. The patients also received effect site target controlled remifentanil (steady state 2.5 min from starting) and a bolus of vecuronium to facilitate intubation and ventilation. We mathematically calculated when each measured parameter would reach a state of stability (i.e. with 95% certainty). Heart rate levelled off at 20 min, Bispectral index at 32 min, and cardiac index and mean arterial pressure at 47 min after achieving effect site stability, the final levels being, respectively, 21%, 47%, 14% and 28% lower than those at effect site stability. We conclude that cardiovascular parameters continue to change to a clinically significant degree after achieving a constant effect site concentration of propofol via target controlled infusions.

Effects of normobaric hyperoxia on haemodynamic parameters of healthy full-term parturients.

Fifteen healthy, full-term women with singleton pregnancies were exposed to an increased F(I)o(2) of 0.4 and their haemodynamic responses measured with a non-invasive transthoracic bio-impedance monitor. There was a mean reduction in cardiac index from 3.18 to 3.03 l x min(-1) x m(-2) (4.7%, p = 0.004). The mean indexed systemic vascular resistance increased from 2049 to 2178 dynes x cm(-5) x m(-2) (5.7%, p = 0.005). There were no significant changes in stroke index, heart rate or mean arterial pressure. This study demonstrates that even a moderate increase in inspired oxygen fraction has significant effects on the cardiovascular system of the term parturient.

Postoperative serum urea is associated with 30-day mortality in patients undergoing emergency abdominal surgery.

BACKGROUND: Emergency abdominal surgery carries considerable postoperative morbidity and mortality. Hypovolaemia is considered to be a cause of renal hypoperfusion, which is associated with a decreased clearance of serum urea and creatinine. This study examines whether the perioperative serum urea and creatinine concentrations are predictors of mortality in patients undergoing emergency abdominal surgery. METHODS: Consecutive patients (n=300) who underwent emergency abdominal surgery were studied. Age- and sex-specific reference intervals were used for the data analysis. Patients with incomplete biochemical (n=51) or mortality data (n=31) or with pre-existing renal failure (n=9) were excluded from the analysis. RESULTS: 209 patients were analysed, of whom 162 (78%) remained alive and 47 (22%) died following surgery. The non-survivors were older (P<0.05), had undergone more extensive surgery (P<0.001) and were more likely to have been admitted to the intensive care unit (P<0.001). The serum urea concentration was higher preoperatively (P<0.05) and on day one postoperatively (P<0.001) in the non-survivors. On multivariate logistic regression analysis, age (odds ratio [OR] 3.27, 95% confidence interval [CI] 1.43-7.47, P<0.005), severity of surgery (OR 2.21, 95% CI 1.14-4.29, P<0.019), admission to intensive care (OR 0.54, 95% CI 0.11-0.54, P<0.001), seniority of anaesthetist (OR 0.50, 95% CI 0.27-0.90, P<0.022) and day one urea (OR 3.33, 95% CI 1.39-7.99, P<0.007) were independently associated with 30-day mortality. CONCLUSIONS: These results indicate that an increased serum urea concentration, but not serum creatinine concentration, in the postoperative period is associated with an increase in 30-day mortality in patients undergoing emergency abdominal surgery.

The cardiovascular effects of inspired oxygen fraction in anaesthetized patients.

BACKGROUND AND OBJECTIVE: Increased inspired oxygen fractions (FiO2) have significant haemodynamic effects in awake volunteers. We sought to establish whether these effects are also present in anaesthetized patients. METHODS: We prospectively studied 30 ASA I-II patients, 15 in each of a propofol and sevoflurane group. Their haemodynamic responses, awake and anaesthetized, when the FiO2 was changed between 0.3 and 1.0 were measured with a non-invasive transthoracic bio-impedance monitor. RESULTS: While preoxygenating awake patients in both groups the FiO2 was increased from 0.21 to 1.0. This reduced the mean cardiac index (3.38 +/- 0.5 to 3.03 +/- 0.5 L min(-1) m(-2); P < 0.001); reduced the heart rate (HR) (68.1 +/- 10.4 to 62.8 +/- 9.4 beats per minute (bpm); P < 0.001); and reduced the stroke index (50.4 +/- 9.6 to 48.5 +/- 8.6; P = 0.02). It increased the systemic vascular resistance index (2060 +/- 319 to 2220 +/- 382 dyn s(-1) cm(-5) m(-2); P = 0.002); but did not change mean arterial pressure. In the anaesthetized patients, when decreasing the FiO2 from 1.0 to 0.3, mean cardiac index (L min(-1) m(-2) increased (3.06 +/- 0.57 to 3.25 +/- 0.56, P = 0.008 for sevoflurane; 2.76 +/- 0.46 to 2.89 +/- 0.42, P = 0.002 for propofol). The mean HR (bpm) increased (65.1 +/- 7.8 to 69.1 +/- 7.5, P < 0.001 for sevoflurane; 67.5 +/- 11.8 to 72.7 +/- 11.6, P = 0.001 for propofol). The mean systemic vascular resistance (dyn s(-1) cm(-5) m(-2)) decreased (1883 +/- 329 to 1735 +/- 388, P = 0.008 for sevoflurane; 2015 +/- 369 to 1771 +/- 259, P = 0.003 for propofol). Mean arterial pressure (mmHg) decreased (74.8 +/- 8.7 to 71.4 +/- 8.7, P < 0.001 for sevoflurane; 72.1 +/- 8 to 66.5 +/- 6.8, P = 0.002 for propofol). CONCLUSION: O2 has haemodynamic effects in awake and anaesthetized patients. These effects were of overall similar magnitude for patients anaesthetized with propofol and sevoflurane.

Effects of a height and weight adjusted dose of local anaesthetic for spinal anaesthesia for elective Caesarean section.

In this prospective, randomised, double-blind study, we compared the effects of two dosage regimens. Pregnant patients at term were randomly assigned to two groups to be given diamorphine 0.4 mg in hyperbaric bupivacaine 0.5% 2.4 ml or diamorphine 0.4 mg in a volume of hyperbaric bupivacaine 0.5% adjusted according to the patient's height and weight. Adequate anaesthesia was provided in all patients in both groups. The onset of the sensory block for cold and pinprick was faster with the fixed dose regimen (p = 0.01). There were more spinal blocks to above the first thoracic dermatome in the fixed dose group (17.1% vs. 2.2%, p = 0.022). Hypotension occurred in 71.7% vs. 50.0% of patients in the fixed dose and adjusted dose groups respectively (p = 0.035). In the fixed dose group, more patients required ephedrine to treat hypotension (79.5% vs. 56.8%, p = 0.022) and a larger median dose was administered (9 mg vs. 6 mg, p = 0.042). The decrease in mean (SD) arterial pressure was less in the adjusted group (35.0 (16.4) mmHg vs. 28.0 (13.5) mmHg, p = 0.036).

The effect of normobaric hyperoxia on cardiac index in healthy awake volunteers.

Fifteen healthy volunteers were exposed to a stepwise increase in FIO2 between 0.21 and 1.0, and their haemodynamic responses were measured with a non-invasive transthoracic bio-impedance monitor. There was mean reduction in cardiac index from 3.44 to 3.08 l.min-1.m-2 (10.7%, p < 0.001). The mean reduction in heart rate was from 77.3 to 69.1 beats.min-1 (10.5%, p < 0.001) and the mean systemic vascular index increased from 2062 to 2221 dyne.s-1.cm-5.m-2 (7.7%, p < 0.025). There were no significant changes in stroke index or mean arterial pressure. These changes are similar quantitatively and qualitatively to those previously reported by dye dilution techniques.

Is enalapril adequate for the prevention of renal tissue damage caused by unilateral ureteral obstruction and/or hyperoxaluria?

Unilateral ureteral obstruction (UUO) and hyperoxaluria (HOX) can lead to end-stage renal disease with tubulointerstitial fibrosis. We investigated the effects of enalapril (E), an ACE-inhibitor, on rat kidneys with either UUO or HOX. Sham-operated, UUO, HOX, UUO+HOX, UUO+E and HOX+E rats were killed 14 days after UUO and/or HOX was initiated. Rat kidney sections were histologically scored for tissue damage and monocyte/macrophage infiltration was demonstrated with ED1 antibody and measured by computer image analysis software. Serious glomerular and tubulointerstitial damage was found for UUO and HOX, consisting of glomerular basement membrane thickening, tubular dilatation/collapse, tubular basement membrane thickening and the infiltration of mononuclear leucocytes (mainly macrophages). For HOX, calcium oxalate crystals were visible. Neither the scored histological parameters nor monocyte/macrophage infiltration was significantly decreased when E-treated were compared with untreated groups. We conclude that E did not ameliorate the parameters scored in either UUO or HOX. This being contrary to findings by other research groups, we hypothesize that E may be effective only in short-term UUO/HOX, with transforming growth factor, TGF-beta1, formation becoming partly independent of Ang II in late-stage UUO/HOX, or other fibrogenic cytokines than TGF-beta1 becoming predominant.

Interleukin-18 expression and modulation in human corneal epithelial cells.

PURPOSE: The interferon-gamma-inducing factor Interleukin-18 (IL-18) is a recently described cytokine that appears to have multiple important pro-inflammatory effects including the induction of interferon-gamma (IFN-gamma) by activated T-cells. The expression of IL-18 by human cornea has not been previously reported. In the present study, we examine the possibility that human corneal epithelial cells are capable of producing this leukocyte-activating factor which may play an important role in IFN-gamma-dependent inflammation responses in the cornea. METHODS: Northern blot analysis and ELISA were used to investigate the in vitro expression of IL-18 mRNA and protein respectively in primary (HCEC) and transformed human corneal epithelial cells (HCET). To determine if IL-18 expression was modulated by pro-inflammatory mediators, cells were treated with lipopolysaccharide (LPS), phorbol 12-myristate 13-acetate (PMA) or synthetic double stranded RNA (poly dI : dC). IL-18 bioactivity was determined in a leukocyte interferon-gamma induction assay and IL-18 was immunolocalized in whole human cornea by immunohistochemistry using a specific anti-IL-18 antibody. RESULTS: IL-18 mRNA and bioactive protein was constitutively expressed by human corneal epithelial cells and upregulated by PMA, LPS and poly dI : dC. The constitutive expression of IL-18 protein immunoreactivity was also demonstrated in the epithelial cells of whole human cornea tissue. CONCLUSIONS: This is the first study demonstrating that corneal epithelial cells are capable of producing the IFN-gamma inducing factor IL-18. Increased bioactive corneal IL-18 production can be induced by a number of pro-inflammatory agents and may play an important role in initiating gamma-interferon-mediated inflammatory responses in the cornea.

Blomstrand osteochondrodysplasia: three novel cases and histological evidence for heterogeneity.

Blomstrand osteochondrodysplasia (BOCD) is a rare, autosomal recessive, lethal skeletal dysplasia characterized by generalized osteosclerosis and advanced skeletal maturation. The histopathological characteristics of three novel cases (two isolated cases and a sib-pair) of BOCD are presented and correlated with the clinical and radiographical findings, and the relevant literature is reviewed. The results of our study confirm the existence of two separate types of BOCD, which we propose naming type I: the severe, 'classical' form, and type II: a less severe form.

Post partum pneumothorax: two case reports and discussion.

Pneumothorax is a rare event during pregnancy. We present two cases of pneumothorax occurring after caesarean section under general anaesthesia, including one tension pneumothorax. We summarise risk factors for developing a pneumothorax during pregnancy and discuss differential diagnosis and the anaesthetic management in the labour ward.

Subependymal nodular heterotopia in patients with encephalocele.

Only incidental mention has been made to date of the combined occurrence of subependymal heterotopia and posterior encephalocele. We evaluated the presence of disseminated nodular subependymal heterotopia in two series of patients with posterior encephalocele. The first series consisted of all six patients who were treated in our hospital for encephalocele during the last 11 years and who underwent magnetic resonance imaging (MRI). In three, subependymal nodular heterotopia was found by MRI. The second series consisted of eight autopsy cases with encephalocele, representing all cases of encephalocele that came to autopsy during a 10-year period on whom full microscopic examination could be performed. Nodular heterotopia was found in four. The combined occurrence of these two rare conditions may not be accidental.

Functional capacity evaluation.

The functional capacity evaluation (FCE) is a tool for assessing the extent of a patient's disability. Several factors help to determine whether an FCE should be conducted. Once underway, the evaluation includes an intake interview, musculoskeletal and functional assessments, validation of effort, and interpretation and recommendation.

Tracheal intubating conditions after induction with propofol, remifentanil and lignocaine.

We have studied the intubating conditions in 60 ASA I or II patients, after induction of anaesthesia with propofol 2 mg kg-1, allocated to one of the following three groups: group 1, remifentanil 1 microgram kg-1; group 2, remifentanil 1 microgram kg-1 and lignocaine 1 mg kg-1; group 3, remifentanil 2 micrograms kg-1. No neuromuscular blocking agents were administered. Intubating conditions were assessed using a four-point scoring system based on ease of laryngoscopy, jaw relaxation, position of vocal cords, degree of coughing and limb movement. Overall intubating conditions were acceptable in 35% of patients in group 1, 100% of patients in group 2 and 85% of patients in group 3. There was a statistically significant drop in blood pressure after induction in groups 2 and 3, and two patients in each group required ephedrine 6 mg i.v. boluses, as dictated by the intervention criteria (mean arterial pressure fall > 25% from baseline). Similarly, there was a drop in heart rate in groups 2 and 3, but this did not reach statistical or clinical significance, and no patient required atropine.