Department of Anaesthesiology and Critical Care
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- ItemAbdominal ultrasound for diagnosing abdominal tuberculosis or disseminated tuberculosis with abdominal involvement in HIV-positive adults(John Wiley & Sons, Ltd. on behalf of The Cochrane Collaboration, 2017) Van Hoving, Daniel J.; Meintjes, Graeme; Takwoingi, Yemisi; Griesel, Rulan; Maartens, Gary; Ochodo, Eleanor A.This is a protocol for a Cochrane Review (Diagnostic test accuracy). The objectives are as follows: To determine the diagnostic accuracy of abdominal ultrasound as a standalone test for detecting abdominal TB or disseminated TB with abdominal involvement in HIV-positive adults. • To determine the diagnostic accuracy of combinations of abdominal ultrasound and existing tests (chest radiograph, full blood count) for detecting abdominal TB or disseminated TB with abdominal involvement in HIV-positive adults. • To investigate potential sources of heterogeneity in test accuracy, including clinical setting, ultrasound training level, and type of reference standard.
- ItemThe ability of the thromboelastogram (TEG® R-time difference between kaolin and heparinase) as a point of care test to predict residual heparin activity after in vitro protamine titration(Stellenbosch : Stellenbosch University, 2017-12) Joseph, Lauren Ann; Levin, Andrew I.; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Anaesthesiology and Critical Care.ENGLISH ABSTRACT: Background: Differentiation between surgical bleeding and coagulopathy is critical as re-exploration is associated with increases in mortality and morbidity. Adequate reversal of heparin with protamine at the end of cardiopulmonary bypass (CPB) is critical to prevent postoperative bleeding. Meticulous dosing of protamine is required as excessive dosages has deleterious side effects on clotting. Traditional methods make use of an activated clotting time (ACT) for evaluation of adequate heparin reversal. However, recent use of other point of care (POC) tests, the thromboelastogram (TEG®) has started challenging the utility and exclusive use of ACT to evaluate effective reversal. Differences between thromboelastographic Rkaolin and R-heparinase times is an indicator of residual heparin. However, the exact relationship between these parameters and the exact amount of residual heparin is unknown. The rationale for this study was to accurately determine the relationship between the magnitude of the R-kaolin and R-heparinase time difference and blood heparin concentrations. Aims: This study was performed to define the in-vitro relationship between the difference between the thromboelastographic R-kaolin and R-heparinase time difference (TEG® Delta-kh R-time) and plasma heparin concentrations. The primary outcome was to determined the relationship between the TEG® Delta-kh R-time difference and heparin concentrations. The secondary outcome was to determine the concentration of heparin at or below which R-kaolin times become measureable. Methods: This was a single centre, prospective, randomized laboratory study. Following institutional ethics approval and informed consent, sixty-two samples were taken during CPB from 20 patients meeting inclusion criteria. Samples were randomized to one of three groups which would dictate the protamine dose. The three groups were based on a protamine to heparin ratio (expressed as milligram protamine per milligram heparin administered to the patient) approximating 0.25, 0.5, and 0.75 mg/mg respectively. Each sample of blood was then administered a dose of protamine. The TEG® analysis entailed measuring the R-kaolin and R-heparinase time and noting the difference. Thereafter, each blood sample was sent for heparin concentration determination using an anti-Xa activity assay. Results: No relationship between the measurable R-kaolin time and heparin concentration could be demonstrated (p=0.80), as well as no relationship between measurable TEG® Delta-kh R- time difference and heparin activity (p=0.42). However, we did identify a high probability to be able to predict a measurable R-kaolin time (negative predictive value 90%, 95% CI 74% to 98%) when heparin concentration is less than 1.24IU/ml. Conclusions: We were unable to predict heparin concentration using TEG® in this study. It is likely that this was related to methodological problems. The protamine dose was a complex calculation and there is uncertainty with regard to the actual amounts used. There were also multiple laboratory technicians, with a possible loss of standardization. However, R-kaolin time will likely be measurable at heparin concentrations below 1.24 IU/ml, and not measurable above that value. This observation is immensely valuable for clinicians and researchers. Future studies should take this into account and attempt to determine the relationship between TEG® Delta-kh R- time differences and heparin activity only when heparin concentration are less than 1.24IU/ml.
- ItemAcute postoperative pain in 1 231 patients at a developing country referral hospital : incidence and risk factors(Medpharm Publications, 2016) Murray, Adriaan Albertus; Retief, Francois WilhelmBackground: Postoperative pain is poorly studied in developing countries. At a Western Cape referral hospital, it was aimed to determine the incidence of acute postoperative pain, to identify populations associated with a higher risk thereof (in order to guide resource allocation) and to investigate whether inexpensive analgesic modalities are currently utilised maximally. Methods: Patients completed visual analogue scales 24 h after surgery for pain immediately after surgery, maximum pain since surgery and current pain. The incidence of moderate or severe pain and median pain scores were calculated for each scale and for different patient populations. Post hoc logistic regression was performed. Morphine prescriptions were compared with the actual administration thereof. Results: Of 1 231 patients, 62% indicated their maximum pain as moderate or severe. Procedures with the highest incidences were caesarean section and lower limb orthopaedic surgery (> 80%). Younger age, female gender, emergency surgery, and surgery to the abdomen and lower limbs were associated with higher incidences. Patients experiencing moderate or severe pain received 46% of their prescribed morphine. Conclusion: In this institution, the incidence of postoperative pain is high as expected. Associations with postoperative pain are identified, which may guide resource allocation. At least one low-cost analgesic modality is currently underutilised.
- ItemAetiology of pulmonary dysfunction in total hip replacement operations: The influence of nifedipine on the factors involved(Health & Medical Publishing Group, 1987-05) Du Toit, H. J.; Macfarlane, C. M.; Taljaard, J. J. F.; King, J. B.; Cooper, R. C.ENGLISH ABSTRACT: Patients undergoing total hip replacement surgery who developed pulmonary dysfunction (PD) demonstrated evidence of a complement activation and increased thromboxane A2 (TXA2) synthesis. In a double-blind study nifedipine (Adalat; Bayer-Miles) was shown to inhibit complement activation and TXA2 synthesis and thus appears to offer protection against PD.
- ItemAirway management of a massive neonatal cervical teratoma : case report and review(Stellenbosch : Stellenbosch University, 2016-12) Von Steiger, Ilonka; Levin, A. I.; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Anaesthesiology and Critical Care.ENGLISH ABSTRACT: Congenital cervical teratomas are rare tumours notorious for causing neonatal airway embarrassment. We report the multidisciplinary management of a foetus with an antenatally diagnosed massive cervical teratoma. Initial management with an ex-utero intrapartum treatment (EXIT) procedure failed. The neonate was delivered and airway control was then achieved using a supraglottic airway device. Tracheal intubation was eventually accomplished using fibreoptic bronchoscopy via the supraglottic airway. The discussion addresses perinatal cervical teratoma with the emphasis on airway management and the use of supraglottic airway devices.
- ItemAkute postoperatiewe pyn opname in Tygerberg Hospitaal(Stellenbosch : Stellenbosch University, 2013-12) Murray, Albertus Adriaan; Retief, Francois Wilhelm; Stellenbosch University. Faculty of Medical and Health Sciences. Dept. of Anaesthesiology & Critical Care.AFRIKAANSE OPSOMMING: Doelwit: Om die voorkoms en erns van postoperatiewe pyn te bepaal gedurende die eerste 24 uur periode in 'n tersiëre hospitaal met beperkte hulpbronne. Om spesifieke groepe en risiko faktore wat verband hou met 'n hoër voorkoms van pyn te identifiseer. Ontwerp: Opname met behulp van 'n vraelys. Opset: Ontwikkelende land tersiëre staatshospitaal met alle chirurgiese dissiplines. Populasie: Pasiënte van alle chirurgiese dissilpines bo 12 jaar oud en toegelaat vir 'n minimum van 24 uur postoperatief. Metodiek: Opname 24 uur na die operasie met behulp van 'n vraelys met 3 visuele analoog pyn skale (VAS) en 'n vraag. Verdere data is ingesamel vanaf die narkose en voorskrif kaarte. Resultate: Postoperatiewe pyn is gerapporteer as matig in 25% en erg in 37% van pasiënte. Onafhanklike risikofaktore vir matige of erge postoperatiewe pyn was ‘n jonger ouderdom, vroulike geslag, nood en abdominale chirurgie. Prosedures met die hoogste voorkoms van matige of erge pyn was keisersnitte (87%) en ortopediese chirurgie van die onderste ledemate (80% - 85%). Morfien toediening was baie minder gereeld as voorgeskryf. Gevolgtrekking: Voorkoms van postoperatiewe pyn in hierdie hulpbron beperkte omgewing is hoog, maar vergelyk met ander instansies. Spesiale sorg moet geneem word in die geïdentifiseerde groepe wat verband hou met 'n hoër voorkoms van pyn. Roetine sistemiese analgesie moet meer tydig toegedien word, veral wanneer die effek van regionale narkose termineer.
- ItemAnaesthesia and the diabetic patient(HMPG, 1985) Roelofse, J. A.; Erasmus, F. R.Since it is estimated that 1 out of every 2 diabetic patients will require surgery at some point in his lifetime, it is imperative that the anaesthetist should understand the disease process as well as the anaesthetic problems associated with it. This article emphasizes the medical, surgical and anaesthetic aspects of the treatment of patients with diabetes mellitus.
- ItemAnaesthetic induction with propofol: How much? How fast? How slow? What determines anesthetic induction dose? It’s the Front-End Kinetics, Doctor!(Medpharm Publications, 2019) Coetzee, J. F.ENGLISH ABSTRACT: It has long been realised that linear dosing according to total body weight (TBW) results in overdosing obese patients and under-dosing small children. Injected drug doses calculated on a mg.kg-1 body weight basis work well only for patients of normal habitus. As long ago as 1969, in a study of induction doses of thiopentone, ulfsohn and Joshi2 concluded that thiopentone was better administered according to lean body mass (LBM) than to TBW. They reasoned that endomorphic somatotypes required less thiopentone than mesomorphs and ectomorphs of the same TBW, because they had less LBM. They pointed out that there is a strong association between LBM, cardiac output and basal metabolic rate, and suggested that the LBM contained the “pharmacologically active mass”. Obese patients can perhaps be loosely regarded as ordinary individuals entrapped in a cocoon of fat into which hardly any injected drug is distributed. However the LBM of obese persons also increases as they accumulate fat, mainly due to increased muscle mass, as well as enlargement of other organs and blood volume. The dilemma is that LBM does not increase at the same rate as the increase in fat. Thus, although we know that they need more drug than normal-weight patients, how much more is often uncertain.
- ItemAnaesthetic management of a three-month-old baby for cervical limited dorsal myeloschisis repair using propofol and alfentanil infusions guided by pharmacokinetic simulation software : case report(Medpharm Publications, 2019) Coetzee, E.; Gray, R.; Hollmann, C.; Enslin, N. J. M.; Coetzee, J. F.ENGLISH ABSTRACT: We present an uncommon case of limited dorsal myeloschisis in a 3-month-old infant requiring repair guided by intraoperative neuromonitoring (IONM) and therefore avoidance of volatile anaesthetic agents. The case presented challenges in positioning, airway management, a lack of age appropriate pharmacokinetic models in target-controlled infusion (TCI) syringe pumps and unavailability of remifentanil, considered to be an essential drug in this setting. We overcame these challenges using manually controlled infusions of propofol and alfentanil guided by pharmacokinetic simulation software (Stelsim).
- ItemAnaesthetic management of cerebral artery aneurysms at Tygerberg Hospital, 1980-1982(Health and Medical Publishing Group -- HMPG, 1984-05) Erasmus, F. R.; Du Toit, H. J.; Rose-Innes, A. P.Forty-seven patients were operated on for intracranial artery aneurysms at Tygerberg Hospital, Parowvallei, CP, between January 1980 and December 1982. Problems related to anaesthesia which are peculiar to this condition and the solution thereof are outlined. The importance of meticulous anaesthetic management in the successful recovery of these patients, the majority of whom are young and in the productive phase of their lives, is stressed. A plea is made for increased awareness, early diagnosis and surgical intervention to decrease the high mortality rate associated with this lethal condition.
- ItemThe anaesthetic management of distal (thoracic) tracheal resection in a quadriplegic patient(Health & Medical Publishing Group, 1980-06) De Roubaix, J. A. M.ENGLISH ABSTRACT: The anaesthetic management of distal tracheal resection in a quadriplegic patient is described. Ketamine, halothane, fentanyl and Entonox (50% N2O, 50% O2) were successfully employed. The major problems discussed include airway maintenance, cardiovascular instability and autonomic hyperreflexia, the dangers of depolarizers, and the need for monitoring temperature, blood pressure and fluid balance. The importance of team work is mentioned.
- ItemAn audit of the labour epidural analgesia service at a regional hospital in Gauteng Province, South Africa(Health and Medical Publishing Group, 2018) Leonard, T. G. A.; Perrie, H.; Scribante, J.; Chetty, S.Background. Neuraxial analgesia in the form of a labour epidural has been shown to be the most effective analgesic strategy for the labouring mother. In developed countries, data are readily available as to the number of women receiving labour epidural analgesia, as well as the complication rates of labour epidurals. However, data for South Africa (SA) on labour epidural analgesia services are limited, and there were no published data for Rahima Moosa Mother and Child Hospital (RMMCH), Johannesburg, SA. Objective. To describe the labour epidural analgesia service at RMMCH over the period of 1 year. Methods. A retrospective audit using consecutive convenience sampling was done reviewing all epidural records at RMMCH from 1 January to 31 December 2014. Results. During the study period, labour epidural analgesia was administered for 187 (1.6%) of 11 853 deliveries. Epidural records were collected for all administered labour epidurals. The most common indications documented were labour analgesia (41.7%) and primigravida (28.9%). Labour epidurals were not administered for specific medical conditions. The incidence of complications was 22.6%, and these were minor and self-limiting. Hypotension was the most common complication (12.3%). Patient satisfaction with labour epidural analgesia, where documented, was high (98.4%). Conclusion. This audit revealed a low incidence of labour epidural analgesia at RMMCH during the study period. The incidence of complications was in keeping with that seen in developed countries. Poor documentation was noted to be a problem.
- ItemBlood oxygen saturation levels during conscious sedation with midazolam. A report of 16 cases(Health & Medical Publishing Group, 1986) Roelofse, J. A.; Van der Bijl, P.; Joubert, J. J.; Breytenbach, H. S.In a double-blind randomized study on 16 healthy individuals, two groups of subjects (8 in each group) received either midazolam (Dormicum; Roche) 0,1 mg/kg or placebo intravenously for conscious sedation during oral surgical procedures. Oxygen saturation of the blood was measured at different stages. Ten minutes after administration of the drug, the percentage oxygen saturation was significantly lower (P<0.05) in the midazolam group than in the placebo group.
- ItemBlood pressure measurement in obese patients : non-invasive proximal forearm versus direct intra-arterial measurements(Taylor & Francis Group, 2018) Verkhovsky, A.; Smit, M.; Levin, A.; Coetzee, J. F.Background: In obesity, accurate perioperative blood pressure measurement using upper arm, non-invasive blood pressure (NIBP) is technically challenging. Proximal forearm NIBP may be an acceptable substitute. Mean arterial blood pressures (MAP) estimated by proximal forearm NIBP were compared with direct intra-arterial measurements. It was hypothesised that the measurement techniques would be interchangeable if between-technique MAP differed ≤ 20% and MAP ratios were < 1.2 and > 0.8. Method: A total of 30 adults with body mass index ≥ 30 kg/m2 in whom perioperative intra-arterial blood pressure measurement was considered mandatory were enrolled. MAP measurements using the two techniques were obtained at three random intervals in each patient. Bland–Altman analyses were employed. Results: Forearm mean NIBP MAP overestimated mean intra-arterial MAP by 2.2 (SD 8.1; range from 23.8 to –19.4 mmHg; p = 0.011, 95% CI 3.9 to 0.5). However, Bland–Altman analyses revealed a wide dispersion with several MAP differences and MAP ratios exceeding the pre-specified bounds for interchangeability. Conclusion: Forearm NIBP could not be considered interchangeable with direct intra-arterial MAP measurements in obese patients.
- ItemBlood pressure measurement in the obese patient: a comparison between non-invasive proximal forearm and radial arterial blood pressure measurement(Stellenbosch : Stellenbosch University, 2017-12) Verkhovsky, Anna; Smit, Marli; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Anesthesiology and Critical Care.ENGLISH ABSTRACT: ABSTRACT Background: South Africa has a high prevalence of obese adults. When these (obese) individuals present to a health care facility, blood pressure measurement will play an important role during routine medical evaluation. Accurate non-invasive blood pressure monitoring is a challenge in obese individuals secondary to inaccurate readings associated with inappropriate cuff size, structural differences of the upper arm as well as short upper arm length. Our aim was to identify an accurate, affordable, minimally invasive and low-risk blood pressure measurement modality in obese patients. Methods: This study included 30 patients with a body mass index of greater or equal to 30 kg/m2 presenting for surgery or staying in a High Care Unit at Tygerberg Hospital. In all of these patients, an intra-arterial line was included as part of their routine care. We compared the non-invasive (mean, systolic and diastolic) blood pressures readings from the proximal forearm, with the gold standard, being intra-arterial blood pressure readings. Results: There was poor agreement between the mean intra-arterial blood pressure measurement and the noninvasive blood pressure (NIBP) measured at the forearm. The mean NIBP measured at the forearm overestimated the intra-arterial blood pressure reading by 2% (±8.1 %. P 0.031). The computed upper and lower levels of agreement between the 2 methods ranged from -19.3 to 15.2%. Systolic NIBP measurements at the forearm over-estimated the IABP measurements by 0.9% (P 0.295). Upper and lower levels of agreement between the 2 methods ranged from -16.4 to 14.7%. Larger discrepancies between the two methods were observed for diastolic blood pressure measurements with a mean difference of -5.8% (P <0.0001). Conclusion: We cannot recommend that the forearm NIBP reading be used as an accurate, non-invasive and cost effective substitute to measure blood pressure in obese patients.
- ItemCaudal block for analgesia after paediatric inguinal surgery(Health & Medical Publishing Group, 1987) Payne, K.; Heydenrych, J. J.; Martins, M.; Samuels, G.Two hundred and eleven children aged 1 - 5 years were studied after undergoing herniorrhaphy or orchiopexy. In 111 cases a caudal block was used for postoperative analgesia. This was administered immediately after induction of anaesthesia, using bupivacaine 0,25% plain (0,7 ml/kg lean body mass), and was successful in 100 patients. A mean analgesic level (± SE) of T9,9 ± 0,47 was achieved (range L2-T6). In 5 cases no block occurred and in 6 the level was below T12. The other 100 children acted as controls. Behaviour patterns were more restful in the caudal block group on awakening and less opiate was required during the first 5 postoperative hours. No complications resulted.
- ItemCentral oxygen pipeline failure(Stellenbosch : Stellenbosch University, 2014-04) Mostert, Lelane; Coetzee, Andre; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Anaesthesiology and Critical Care.ENGLISH ABSTRACT: Case Report - A case is described of central oxygen pipeline failure that occurred at a large academic hospital and its subsequent implications for managing the situation. Literature review - The literature review undertaken focused on the current state of affairs with regards to anaesthetic staff's knowledge of and preparedness for the management implications of central oxygen pipeline failure. The events I describe below demonstrate a significant deficiency in the staff’s understanding of and training for the crisis, which should be remedied to improve patient safety. Specific measures are suggested in the literature to prevent such incidents and guidelines are available to manage central oxygen pipeline failure. These are reviewed in this study. Recommendations - This study attempts to bring together the most critical aspects that need to be addressed to safely manage similar future incidents. Prevention should include measures to implement clearly stated disaster management plans and increased awareness with regards to the medical gas pipeline system (MGPS), simulation training, efficient alarm systems, personally conducted routine evaluations of equipment and emergency backup systems by anaesthesiologists and effective communication between hospital staff. Careful planning and successful coordination during maintenance and modification of the medical gas pipeline system, using piston-type or air-driven, rather than oxygen-driven, ventilators and optimal design of the hospital bulk oxygen system can contribute to reduce risks. In the event of central oxygen pipeline failure a specific sequence of actions should be taken by the anaesthesiologist and a clear institutional operational policy is described.
- Item'Closed circuit' anaesthesia(Health & Medical Publishing Group, 1974) Foster, P. A.[No abstract available]
- ItemComparison of haemoglobin values measured at point of care with the standard laboratory value(Stellenbosch : Stellenbosch University, 2016-12) Johnson, Marianne; Marwick, Peter; Stellenbosch University. Faculty of Health Sciences. Dept. of Anaesthesiology and Critical Care.ENGLISH ABSTRACT: Point of care (POC) haemoglobin (Hb) concentration estimations guide acute decisions on red blood cell transfusion. We studied the accuracy of three POC devices when compared to central laboratory Hb testing and how between-method Hb disagreements could affect the decision to transfuse. The Health Research Ethics Committee of the University of Stellenbosch approved a method comparison study of perioperative Hb concentration measurement in arterial blood sampled from 58 adult cardiothoracic surgery patients. The Hb concentration was measured by using two Ilex GEM PremierTM 3500 blood gas analysers (Blood gas A and Blood gas B), a HemoCue® Hb 201+ System (HemoCue), and our central laboratory’s Siemens Advia® 2120 flow cytometry system (Laboratory haemoglobin). We regarded that a between-method Hb difference exceeding 10% (1 g/dL at an Hb value of 10 g/dL), would likely erroneously influence the transfusion decision. Furthermore, one unit of packed red blood cells will increase the Hb by ±1 g/dL and clinically represents the smallest transfusion associated risk that a patient will be exposed to. From the 58 patients included in the study, 70 central laboratory Hb concentration (Laboratory haemoglobin) measurements and 58, 72, and 71 measurements by the HemoCue, blood gas analyser A (Blood gas A) and blood gas analyser B (Blood gas B), respectively were taken. We found that the mean POC (HemoCue, Blood gas A, and Blood gas B) Hb levels underestimated the mean central laboratory Hb level by 0.79 g/dL, 0.81 g/dL, and 0.67 g/dL, respectively. The 95% confidence interval (CI) of the between-method difference revealed that unlike the Blood gas A (0.43 to 1.15 g/dL) and Blood gas B (0.46 to 1.16 g/dL) values, the HemoCue (0.47 to 0.87 g/dL) values did not breach the predetermined 1 g/dL limit. A Bland-Altman analysis revealed similar between-method mean Hb differences. However, the HemoCue upper and lower limits of agreement (LOA) were narrower, and the 95% CI of the LOAs do not overlap with those of Blood gas A and Blood gas B. Overall the HemoCue is more accurate. Also, the 95% CI of the HemoCue’s lower LOA was below 1 g/dL. This device does not give readings that clinically overestimate the Laboratory haemoglobin. Similarly, the mountain plot demonstrates the greater agreement and precision of the HemoCue device, as compared to Blood gas A and Blood gas B. An error grid analysis focused on the Hb 6 to 10 g/dL clinical decision-making range where only a 10% error was permitted. The error grid analysis revealed that the HemoCue and blood gas analysers had potential transfusion errors of less than 5% and more than 20%, respectively. However, none of the evaluated devices produced values in the major therapeutic error zone, where a decision to transfuse or not transfuse blood will be made erroneously.
- ItemComparison of minimally and more invasive methods of determining mixed venous oxygenation(Stellenbosch : Stellenbosch University, 2013-12) Smit, Marli; Levin, Andrew I.; Coetzee, J. F.; Stellenbosch University. Faculty of Medicine & Health Sciences. Dept. of Anesthesia and Critical Care.ENGLISH ABSTRACT: Circulatory efficiency is the relationship between oxygen consumption and global oxygen delivery. Manipulation of circulatory efficiency has been shown to be beneficial in critically ill surgical and medical adults, and in children. Circulatory efficiency is best assessed by measuring an index of mixed venous oxygenation (content, saturation and partial pressure) and viewing this in the context of oxygen consumption. Mixed venous oxygenation has until now required intermittent sampling via a pulmonary artery catheter, or by using a pulmonary artery catheter equipped with a fibre optic bundle for continuous mixed venous oxygen saturation monitoring. However, the use of the pulmonary artery catheter is declining as it has been (correctly or incorrectly) indicted of being an “invasive” tool. Attempts have been made to estimate mixed venous oxygenation non-invasively using the “NICO” monitor[6], near infrared spectroscopy[7], skeletal muscle oxygen saturation[8], thenar muscle oxygen saturation[9] and transtracheal pulse oximetry.[4]While all of them effectively trended mixed venous oxygen saturation, their accuracy and use as a resuscitation endpoint are in doubt. Sampling central venous as a surrogate of mixed venous oxygenation is fraught with problems, particularly in sicker patients. Significant differences in oxygenation can be demonstrated between the pulmonary arterial and central venous sampling sites in shock states,[3, 10] in acutely ill post-surgical patients [11] and under varying hemodynamic conditions.[12] With the decline in the use of the pulmonary artery catheter, minimally invasive cardiac output determination is becoming increasingly popular. Apart from that their accuracy (particularly un-calibrated devices) has been questioned; they also cannot determine mixed venous oxygen saturation. To obtain a more reliable and refined, but less invasive, estimate of mixed venous oxygenation would be beneficial. The primary aim of this study was therefore to investigate whether venous oxygenation (mixed venous oxygen content, saturation and partial pressure) could be accurately predicted by minimally invasive methods of determining cardiac output and non-invasive calorimetric methods of measuring oxygen consumption. The methods compared were the current invasive gold standard represented by direct sampling of mixed venous blood and thermodilution cardiac output using a pulmonary artery catheter, with a less invasive method of calculating mixed venous saturation, the latter comprised of 4 elements: 1. Cardiac output was measured using a minimally invasive technique, namely lithium dilution (LiDCo®). 2. Oxygen consumption was measured with a non-invasive calorimetric device (M-COVX™ module manufactured by General Electric Corporation). 3. Arterial oxygen content was estimated using blood sampled via an arterial catheter. 4. These 3 variables were inputted into Fick’s equation and solved for venous oxygen content (CvO2 = CaO2 –VO2/CO). Thereafter, using the calculated venous oxygen content as well as the haemoglobin concentration, mixed venous oxygen saturation and partial pressure was estimated using an Excel® spreadsheet (Appendix G) relating oxygen saturation and partial pressure using standard oxygen dissociation curve formula, and calculating oxygen content from various haemoglobin concentrations. Analysis of the data was performed predominantly using Bland Altman analysis. LiDCo® derived cardiac output overestimated that measured using intermittent thermodilution PAC by a clinically significant average of 0.82liters/minute or 26%. The pulmonary artery catheter derived oxygen consumption underestimated that measured by the metabolic module by 52 ml/minute or 27%. Oxygen consumption was the parameter having the largest percentage error (27%) and difference between the Bland Altman upper and lower limits of agreement. The difference between oxygen consumption measured by indirect calorimetry is expected to exceed that calculated using the indirect Fick method by 20 to 30% because intra-pulmonary oxygen consumption is excluded when using this method.[ 13] However, the scatter exhibited by the calorimetry estimations of oxygen consumption was probably the major reason for the discrepancy between the calculated and measured mixed venous oxygenation variables. Despite small (12.0 to 26.3 %) differences between measurements in individual patients, venous oxygenation variables measured by the invasive and less invasive techniques were statistically different. We also considered the magnitude of these differences to be clinically significant as we were of the opinion that relying on the calculated results could adversely impact clinical decision-making. In conclusion, we could not estimate venous oxygenation accurately enough using minimally invasive methods of determining cardiac output and non-invasive methods of measuring oxygen consumption to be clinically useful.