Biomedical subjects
R C Freebairn
Publications and source records attributed to R C Freebairn.
Resuscitation of critically ill patients based on the results of gastric tonometry: a prospective, randomized, controlled trial.
OBJECTIVE: To determine whether additional therapy aimed at correcting low gastric intramucosal pH (pHi) improves outcome in conventionally resuscitated, critically ill patients. DESIGN: Prospective, randomized, controlled study. SETTING: General intensive care unit (ICU) of a university teaching hospital. PATIENTS: A total of 210 adult patients, with a median Acute Physiology and Chronic Health Evaluation II score of 24 (range, 8-51). INTERVENTIONS: All patients were resuscitated according to standard guidelines. After resuscitation, those patients in the intervention group with a pHi of <7.35 were treated with additional colloid and then dobutamine (5 microg/kg/min then 10 microg/kg min) until 24 hrs after enrollment. MEASUREMENTS AND MAIN RESULTS: There were no significant differences (p > .05) in ICU mortality (39.6% in the control group vs. 38.5% in the intervention group), hospital mortality (45.3% in the control group vs. 42.3% in the intervention group), and 30-day mortality (43.7% in the control group vs. 40.2 in the intervention group); survival curves; median modified maximal multiorgan dysfunction score (10 points in the control group vs. 13 points in the intervention group); median modified duration of ICU stay (12 days in the control group vs. 11.5 days in the intervention group); or median modified duration of hospital stay (60 days in the control group vs. 42 days in the intervention group). A subgroup analysis of those patients with gastric mucosal pH of > or =7.35 at admission revealed no difference in ICU mortality (10.3% in the control group vs. 14.8% in the intervention group), hospital mortality (13.8% in the control group vs. 29.6% in the intervention group), or 30-day mortality (10.3% in the control group vs. 26.9% in the intervention group). CONCLUSIONS: The routine use of treatment titrated against pHi in the management of critically ill patients cannot be supported. Failure to improve outcome may be caused by an inability to produce a clinically significant change in pHi or because pHi is simply a marker of disease rather than a factor in the pathogenesis of multiorgan failure.
Oxygen delivery, oxygen consumption, and gastric intramucosal pH are not improved by a computer-controlled, closed-loop, vecuronium infusion in severe sepsis and septic shock.
OBJECTIVE: To investigate the influence of the neuromuscular blocking agent vecuronium on oxygen delivery (DO2), oxygen consumption (VO2), oxygen extraction ratio, and gastric intramucosal pH in heavily sedated patients with severe sepsis or septic shock. DESIGN: Prospective, randomized, placebo-controlled, cross-over trial. SETTING: University hospital intensive care unit. PATIENTS: Eighteen mechanically ventilated patients with severe sepsis or septic shock. INTERVENTIONS: All patients were heavily sedated. After baseline measurement, a computer-controlled, closed-loop infusion of either vecuronium or saline was initiated and further measurements were made at 40 and 60 mins. The procedure was repeated with the alternative agent after return of neuromuscular function. MEASUREMENTS AND MAIN RESULTS: DO2, VO2, intramucosal pH were monitored using pulmonary artery catheters, a gas exchange monitor, and gastric tonometers. Changes from baseline were compared (paired t-test, p = .05). The vecuronium closed-loop infusion achieved T1 between 5% and 15% at 40 mins. There was a significant difference in the changes from baseline for static respiratory compliance in the vecuronium closed-loop infusion group compared with the saline closed-loop infusion group. There was no significant difference in the change from baseline for systemic or pulmonary vascular resistance, DO2, VO2, oxygen extraction ratio, or intramucosal pH. CONCLUSIONS: In these patients, vecuronium infusion achieved the targeted level of paralysis and improved respiratory compliance but did not alter intramucosal pH, VO2, DO2, or oxygen extraction ratios. With deep sedation, neuromuscular blockade in severe sepsis/septic shock does not significantly influence oxygen flux and should be abandoned as a routine method of improving tissue oxygenation in these patients.
Failure of the INVOS 3100 cerebral oximeter to detect complete absence of cerebral blood flow.
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Comparison of intrathoracic and intra-abdominal measurements of central venous pressure.
BACKGROUND: Complications can arise from standard intrathoracic central venous pressure (CVP) measurements in critically ill, mechanically ventilated patients. We have assessed the feasibility of catheterisation by the femoral route to measure CVP in the abdomen (ACVP). We compared measurements by the standard jugular or subclavian route (TCVP) with simultaneous ACVP measurements by the femoral route. METHODS: Between June, 1994 and May, 1995, we recruited 20 critically ill adult patients with various disorders; all patients already had a TCVP line in situ. We placed a femoral catheter in the inferior vena cava close to the right atrium under electrocardiographic guidance. The catheter position was confirmed (and corrected if necessary) by chest radiography. CVP was measured from both sites hourly for 6 h. Positive end-expiratory pressure, mean airway pressure, and intra-abdominal pressure were recorded simultaneously. FINDINGS: One patient was excluded because radiography showed that the catheter position was incorrect. For 133 paired measurements of ACVP and TCVP in the remaining 19 patients, the mean difference was 0.45 mm Hg (SD 0.89: 95% Cl 0.30-0.60); the limits of agreement were -1.33 to 2.23 mm Hg (-1.63 to 2.53). We found a small tendency for the difference between ACVP and TCVP to increase as positive end-expiratory pressure and mean airway pressure increased; the difference was statistically, but not clinically, significant. INTERPRETATION: Our study showed that for clinical purposes CVP can be measured by a femoral catheter placed in the abdominal inferior vena cava near the right atrium. This approach can replace standard TCVP measurements in critically ill, mechanically ventilated patients.
A comparison of the haemodynamic effects of intrathecal meperidine, meperidine-bupivacaine mixture and hyperbaric bupivacaine.
PURPOSE: To study the haemodynamic effects of intrathecal meperidine, administered either alone or mixed with bupivacaine. METHODS: We studied 42 Chinese patients, aged 59-87 yr, scheduled for transurethral bladder or prostate surgery, randomized into three equals groups, that received either meperidine 0.8 mg.kg-1, meperidine 0.4 mg.kg-1 plus 1.5 ml of 0.5% heavy bupivacaine or 3 ml of heavy bupivacaine 0.5%. Non-invasive systolic (SAP) and mean (MAP) arterial pressures, central venous pressure and cardiac index, stroke index and heart rate (HR) measured by the BoMed NCCOM3-R7S bioimpedance device, were recorded over the first 25 min. Systemic vascular resistance index (SVRI) was derived. Onset of sensory and motor block was also measured. Decreases in MAP of 25% were treated with colloid and metaraminol. RESULTS: The onset of block was slower in the meperidine group (P < 0.05). Decreases in SAP, MAP and SVRI (all; P < 0.001) occurred within five minutes in all three groups. The HR was increased in the bupivacaine group (P = 0.03), but bradycardias treated with atropine occurred in six patients receiving meperidine and four patients receiving the mixture. Six patients receiving meperidine and two patients receiving the mixture required general anaesthesia for inadequate block. The incidence of nausea and vomiting was higher in the patients receiving meperidine (P < 0.05). No other complications were encountered. CONCLUSIONS: Intrathecal meperidine used alone or mixed with bupivacaine has no intra-operative advantage over heavy bupivacaine 0.5%.
Fatal acute hepatorenal failure following potassium permanganate ingestion.
Potassium permanganate (KMnO4), a powerful oxidizing agent, is readily available without prescription. Tissue contact produces coagulation necrosis and the lethal consequences of oral ingestion are well described, with most deaths because of airway oedema and obstruction or circulatory collapse. Whilst systemic toxicity is reported, its mechanism is unclear. We describe a case of suicidal ingestion of KMnO4 followed by acute hepatorenal toxicity resulting in the death of the patient. The clinical course bore close resemblance to that of severe paracetamol overdose. We discuss the pathogenesis of the systemic toxicity of KMnO4 and postulate that it is due to oxidative injury from free radicals generated by the absorbed permanganate ion. We recommend that N-acetyl cysteine be given within the first few hours to all patients with potassium permanganate poisoning.
Accidental intra-arterial adrenaline administration.
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Successful treatment of carbimazole-induced agranulocytosis and severe sepsis with granulocyte macrophage colony stimulating factor.
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Accuracy of the tonometric function of recycled gastric tonometer catheters.
We investigated the accuracy of recycled gastric tonometer catheters, using a prospective laboratory model, within the Intensive Care Unit of a University teaching hospital. Ten used tonometer catheters and three new catheters were exposed to known constant PCO2 levels between 23-65 torr (3.06-8.66 kPa) in a gas mixing chamber, at a temperature of 35.5-38 degrees C and a relative humidity > 95%. The tonometer balloons were primed with normal saline, and after a 30-minute equilibration time, the saline was sampled for PCO2 measurements. Steady-state PCO2 (PCO2(SS)) and gastric mucosal pH (pHi) values were derived using a correction factor and the Henderson-Hasselbalch equation. There was no difference in the mean or distribution of PCO2(SS) values between recycled and new catheters. The PCO2(SS) values of recycled catheters were within the 95% confidence limits of those of new catheters. Individual catheter values did not differ significantly from each other (ANOVA P = 0.05). Using an arterial HCO3- value of 21 mmol/l, the calculated pHi values of used catheters varied < 1.5% of the mean pHi of new catheters. The tonometric performance of recycled gastric tonometer catheters was similar to that of new catheters when tested in vitro.
Paediatric acute renal failure. A report on 2 cases successfully managed with continuous venovenous haemodiafiltration.
In critically ill patients continuous venovenous haemodiafiltration (CVVHD) is a method of renal replacement therapy gaining popularity. The advantage of CVVHD over intermittent haemodialysis and peritoneal dialysis lies in the accurate control of ultrafiltration and of solute clearance. Two paediatric patients with acute renal failure treated successfully with CVVHD are described. The role of CVVHD in renal supportive therapy in South African paediatric intensive care units is discussed.
Continuous venovenous haemodiafiltration--an audit demonstrating control of electrolytes with haemodynamic stability in the critically ill.
OBJECTIVE: Renal replacement therapy has evolved significantly in the last 15 years, resulting in a large diversity of techniques with differing attributes. Theoretical advantages of the continuous over intermittent techniques in critically ill patients include haemodynamic stability and a reduction in disequilibrium syndrome. Limited clinical evidence supports this, but a clear reduction in mortality or morbidity has yet to be shown. The technique of renal replacement therapy in the Intensive Care Unit at Baragwanath Hospital was recently revised and a retrospective study of the haemodynamic and electrolyte changes associated with implementing continuous venovenous haemodiafiltration (CVVHD) was carried out. METHOD: A retrospective analysis of demographic data, haemodynamic and physiological parameters in 10 consecutive patients receiving CVVHD during a 10-week period was conducted. Patients' systolic (SBP), and mean (MAP) arterial blood pressures, heart rates (HR), and central venous pressures (CVP) during the first 36 hours after the implementation of CVVHD were reviewed. Serum creatinine, urea and potassium values were also collated. Other organ system failures and outcomes were noted. RESULTS: HR decreased by 6.1% (SD 1.5) and average MAP rose (12.1%; SD 7.8) as did SBP (12.4%; SD 6.3), compared with the values immediately before CVVHD: CVP was unchanged. Control of hyperkalaemia was effected in all cases. Serum urea and creatinine levels were well controlled, and clearances were closely related to the dialysate flow. Although the mortality rate was high, it was lower than predicted. No deaths were directly attributable to acute renal failure or complications of CVVHD: CONCLUSION: In the critically ill, CVVHD provides excellent serum urea and creatinine clearance and control of electrolytes without further compromise of haemodynamics. The low associated morbidity, the ease of implementation and the efficacy of the technique may make CVVHD the technique of choice for ARF in the intensive care unit.
Successful use of continuous veno-venous haemofiltration to treat profound fluid retention in severe peripartum cardiomyopathy.
The use of continuous veno-venous haemofiltration after failure of conventional treatment in a patient with severe peripartum cardiomyopathy is described. Treatment with inotropes and diuretics failed to produce a diuresis despite the presence of severe fluid overload. Haemofiltration over a 9-day period allowed removal of 171 of fluid with a concomitant improvement in haemodynamic function and a spontaneous diuresis.
Renal replacement therapy for the critically ill--precarious progress. Part II. Technical aspects and clinical application.
Renal replacement therapy has evolved significantly in the last 15 years. Evolution has produced diversity in both techniques and terminology. Theoretical advantages of the continuous over intermittent techniques in critically ill patients exist. Limited clinical evidence supports this, but a clear reduction in mortality or morbidity has yet to be shown. In Part I of this review the terms and techniques used were defined and the physiological aspects of renal replacement therapy discussed. In this part the technical aspects and associated problems are discussed and a prescription for an effective application of the technique in critically ill patients is provided.
Renal replacement therapy for the critically ill--precarious progress. Part I. Definitions and physiological aspects.
Renal replacement therapy has evolved significantly in the last 15 years. Evolution has produced diversity in both techniques and terminology, leading to considerable ambiguity and confusion. Theoretical advantages of the continuous over intermittent techniques in critically ill patients exist. These include haemodynamic stability, expedient correction of metabolic derangement, accurate fluid control, cytokine clearance, and improved respiratory function. Limited clinical evidence supports this, but a clear reduction in mortality or morbidity has yet to be shown. In Part I of this review the terms and techniques used are defined and the physiological aspects of renal replacement therapy are discussed. In Part II the technical aspects will be discussed and a prescription for an effective technique in critically ill patients will be provided.