Continuous arterial blood gas monitoring during bilateral sequential lung transplantation.

OBJECTIVE: To determine the accuracy and clinical utility of a continuous arterial blood gas (ABG) monitor during lung transplantation. DESIGN: Prospective, observational cohort study. SETTING: University hospital. PARTICIPANTS: Eleven patients undergoing bilateral sequential lung transplantation (BSLTx). INTERVENTIONS: Repeated ABG sampling. MEASUREMENTS AND MAIN RESULTS: Agreement was measured by the bias (limits of agreement): pH, 0.006 (-0.10 to 0.10); PaO2, -22 mmHg (-130 to 86 mmHg); and PaCO2, -1.6 mmHg (-13.4 to 10.2 mmHg). Sensitivity and specificity of the Paratrend 7 (Biomedical Sensors, Ltd, Malvern, PA) PaO2 measurements (to detect PaO2 < 100 mmHg) were 84.6% and 97.6%, respectively. CONCLUSION: Continuous ABG monitoring with the Paratrend 7 shows sufficiently good agreement with laboratory blood gas analysis during BSLTx and thus is a convenient alternative to intermittent laboratory blood gas measurement. Because of the potential for significant (and sometimes rapid) acid-base disturbances, continuous ABG monitoring may have a role during most lung transplantation procedures.

Clonidine and cardiac surgery: haemodynamic and metabolic effects, myocardial ischaemia and recovery.

Clonidine may have beneficial effects in patients undergoing major surgery. We enrolled 156 patients having elective CABG surgery in a double-blind, randomized trial. Patients were randomized to receive either two doses of placebo (Group PP) or clonidine 5 micrograms/kg (Group CC). Perioperative measurements included haemodynamics, anaesthetic and analgesic drug usage, creatinine clearance, cortisol excretion, recovery times and quality of life (SF-36) after surgery. Overall, there was no significant difference with time to tracheal extubation (median [10-90 centile]): CC 7.1 (3.4-18) h vs PP 8.0 (4.3-17) h, P = 0.70; but there was a higher proportion of patients extubated within four hours: CC 20% vs. PP 8%, P = 0.038. Clonidine resulted in a number of significant (P < 0.05) haemodynamic changes, particularly pre-CPB: less tachycardia and hypertension, more bradycardia and hypotension. Clonidine was associated with a significant (P < 0.05) reduction in anaesthetic drug usage, higher creatinine clearance, lower cortisol excretion and improvement in some aspects of quality of life. This study lends support to consideration of clonidine therapy in patients undergoing CABG surgery.

Continuous measurement of arterial and end-tidal carbon dioxide during cardiac surgery: Pa-ETCO2 gradient.

There have been reports of a negative arterial to end-tidal CO2 gradient (Pa-ETCO2) during cardiac surgery, so we used capnometry and an intravascular blood gas sensor (Paratrend 7) to continuously monitor this gradient in 20 cardiac surgical patients. We also compared the values obtained from this sensor with those obtained from a standard blood gas analyser at seven time points. We found a significant change in Pa-ETCO2 after cardiopulmonary bypass (P < 0.001) though we were unable to demonstrate a negative Pa-ETCO2 at any time (95% CI 0-14%). There was clinically acceptable agreement between laboratory and Paratrend 7 measurements during and after cardiac surgery.

Mitral valve replacement via a right mini-thoracotomy in the dog: use of carbon dioxide to reduce intracardiac air.

OBJECTIVE: To develop a clinically applicable method of minimally invasive mitral valve replacement (MVR) with cardioplegia, and examine the ability of carbon dioxide (CO2) to improve de-airing. METHODS: MVR was performed via a 5 x 3-cm right lateral minithoracotomy in eight greyhounds. Peripheral cardiopulmonary bypass and an ascending aortic balloon catheter (endoaortic clamp) were used for cardioplegia and aortic root venting. The endoaortic clamp was inflated in the ascending aorta under fluoroscopy and cardioplegic solution was infused. In four dogs, CO2 at 2 l/min was used to displace air in the chest. A left atriotomy was made, the valve exposed and a mechanical valve implanted. After left atrial closure, retained intracardiac gas was aspirated from the aortic root and collected in a bubble-trap. The endoclamp was deflated and the animal weaned from bypass. RESULTS: A satisfactory MVR was performed in all cases. The clamp time was 64 +/- 13 min and all dogs were stable post-bypass. In the CO2 group, intrathoracic CO2 was maintained above 86% and 0.1 +/- 0.1 ml of gas was collected, compared to 1.3 +/- 0.8 ml in the non-CO2 group (P < 0.05). CONCLUSIONS: Femoro-femoral bypass and use of the endoaortic clamp allow a safe and efficacious MVR via a right minithoracotomy in the dog. A high intrathoracic CO2 concentration reduces the amount of retained intracardiac gas.

Comparison of 0.5% ropivacaine and 0.5% bupivacaine in lumbar epidural anaesthesia for lower limb orthopaedic surgery.

The purpose of this study was to compare the epidural use of 0.5% ropivacaine and 0.5% bupivacaine in patients undergoing lower limb orthopaedic surgery. In a double-blind, randomized, multi-centre study involving 67 patients, thirty-two patients received 20 ml of 0.5% ropivacaine and 35 patients received 20 ml of 0.5% bupivacaine at the L2,3 or L3,4 interspace. Parameters measured were the onset time, duration and spread of sensory block, the onset time, duration and degree of motor block, the quality of anaesthesia and the heart rate and blood pressure profile during block onset. Four patients (3 ropivacaine, 1 bupivacaine) were excluded from the study due to technical failure of the block. The onset and duration of analgesia at the T10 dermatome (median, interquartile range) was 10 (5-15) minutes and 3.5 (2.7-4.3) hours respectively for ropivacaine, and was 10 (6-15) minutes and 3.4 (2.5-3.8) hours respectively for bupivacaine. Maximum block height (median, range) was T6 (T2-T12) for ropivacaine and T6 (C7-T10) for bupivacaine. Nine patients receiving ropivacaine and eight patients receiving bupivacaine developed no apparent motor block. The incidence of complete motor block (Bromage grade 3) was low in both groups, being 4/27 for ropivacaine and 6/34 for bupivacaine. In the ropivacaine group, motor and sensory block were judged to be satisfactory in 78% of patients. In the bupivacaine group, motor and sensory block were judged to be satisfactory in 71% and 62% of patients respectively. Cardiovascular changes were similar in both groups. No statistical differences were found between the two groups regarding any of the study parameters.

Early hemodynamic effects of left atrial administration of epinephrine after cardiac transplantation.

We studied the hemodynamic effects of left atrial (LA) administration of epinephrine in 10 patients after cardiac transplantation, using a prospective, randomized, double-blind, cross-over design. After allograft implantation, a LA catheter was inserted and epinephrine infusion commenced at 100 ng.kg-1.min-1. Each trial period consisted of 20 min, with the LA and right atrial (RA) lines switched over between each period; hemodynamic measurements were taken after each time period. Whether epinephrine was administered via the RA or LA did not significantly alter hemodynamics (RA versus LA): mean (SD) arterial blood pressure 67 (7.5) vs 64 (9.5) mm Hg (P = 0.16), mean pulmonary artery pressure 22 (4.0) vs 21 (9.4) mm Hg (P = 0.67), cardiac index 3.2 (1.1) vs 3.2 (1.1) L.min-1.m-2 (P = 0.83), pulmonary vascular resistance index 308 (157) vs 345 (157) dynes.s.cm-5/m-2 (P = 0.30) or right ventricular ejection fraction 35% (11%) vs 32% (9.8%) (P = 0.23). Arterial epinephrine plasma levels were similar (P = 0.16). There was no significant pulmonary extraction of measured catecholamines. We observed no hemodynamic benefit of LA epinephrine administration. It may be that the cardiac transplantation population reacts differently compared with other cardiac surgical patients (possibly because pulmonary extraction of catecholamines is reduced). Because we did not observe a hemodynamic advantage in patients immediately after cardiac transplantation, we would not recommend the use of LA epinephrine at the dose studied.

Anesthesia for bilateral sequential lung transplantation: experience of 64 cases.

OBJECTIVES: To review the experience of anesthesia for bilateral sequential lung transplantation (BSLTx) and describe factors associated with outcome. DESIGN: Case series. SETTING: University hospital. PARTICIPANTS: Sixty-four adult patients undergoing BSLTx. INTERVENTIONS: Descriptive and inferential statistical analysis. MEASUREMENTS AND MAIN RESULTS: Details of anesthetic technique, patient, and perioperative characteristics are presented. Mean (SD) lung allograft ischemic times were 320 (81) minutes for the first lung and 446 (93) minutes for the second lung. Mean (SD) duration of surgery was 8.5(2) hours, and median time to extubation was 28 hours. There was a reduction in the use of cardiopulmonary bypass, from 10 of 19 (53%) in 1992 to 1993 to 10 of 45 (22%) in 1994 to 1996, p = 0.016. There was an association between time to extubation and duration of surgery (Spearman rank correlation, p = 0.33, p = 0.008), but no association with intraoperative fluid administration (p = 0.18, p = 0.16), or inotrope requirements (p = 0.06, p = 0.65). Predictors of in-hospital mortality were preoperative renal impairment (p = 0.034), early reoperation (p = 0.005), and delay in extubation (p = 0.013); and for 12-month mortality was patient age (p = 0.01). The actuarial survival rates were 90%, 73%, and 58% at 30 days, 1 year, and 2 years, respectively. CONCLUSIONS: Anesthesia for BSLTx is a most challenging procedure, for which maintenance of tissue oxygenation and right ventricular perfusion are essential. Recent advances include use of inhaled nitric oxide, ventilator management that reduces dynamic hyperinflation, and permissive hypercapnia. Analysis of outcome from a large case series such as this enables the anesthesiologist to be more aware of the important features of anesthesia for BSLTx, as well as identify potential areas of improvement.

Hemodynamic effects, myocardial ischemia, and timing of tracheal extubation with propofol-based anesthesia for cardiac surgery.

Recent interest in earlier tracheal extubation after coronary artery bypass graft (CABG) surgery has focused attention on the potential benefits of a propofol-based technique. We randomized 124 patients (34 with poor ventricular function) undergoing CABG surgery to receive either a propofol-based (5 mg.kg-1.h-1 prior to sternotomy, 3 mg.kg-1. h-1 thereafter; n = 58) or enflurane-based (0.2%-1.0%, n = 66) anesthetic. Induction of anesthesia consisted of fentanyl 15 micrograms/kg and midazolam 0.05 mg/kg intravenously in both groups. The enflurane group received an additional bolus of fentanyl 5 micrograms/kg prior to sternotomy and fentanyl 10 micrograms/kg with midazolam 0.1 mg/kg at commencement of cardiopulmonary bypass (CPB). Patients receiving propofol were extubated earlier (median 9.1 h versus 12.3 h, P = 0.006), although there was no difference in time to intensive care unit (ICU) discharge (both 22 h, P = 0.54). Both groups had similar hemodynamic changes throughout (all P > 0.10), as well as metaraminol (P = 0.49) and inotrope requirements (P > 0.10), intraoperative myocardial ischemia (P = 0.12) and perioperative myocardial infarction (P = 0.50). The results of this trial suggest that a propofol-based anesthetic, when compared to an enflurane-based anesthetic requiring additional dosing of fentanyl and midazolam for CPB, can lead to a significant reduction in time to extubation after CABG surgery, without adverse hemodynamic effects, increased risk of myocardial ischemia or infarction.

Association between oxygen delivery and consumption in patients undergoing cardiac surgery. Is there supply dependence?

We studied the relationship between oxygen delivery (DO2) and consumption (VO2) in twenty patients undergoing cardiac surgery, in order to determine if VO2 was dependent on DO2 (pathological oxygen supply dependence). We measured VO2 from expired gas analysis (VO2G) and compared this to that calculated using the reverse Fick method (VO2F). Both VO2G and VO2F increased after cardiopulmonary bypass (P < 0.001), without change in DO2 (i.e. oxygen extraction ration increased). There was a significant relationship between changes in DO2 and VO2F, both before bypass (r = 0.74, P < 0.001) and after bypass (r = 0.69, P < 0.001), while changes in DO2 and VO2G had no such relationship (pre-bypass: r = 0.38, P = 0.094; post-bypass: r = 0.10, P = 0.68). There was poor agreement between VO2F and VO2G perioperatively. We could not demonstrate supply dependence in elective cardiac surgical patients.

Postoperative nausea and vomiting. Propofol or thiopentone: does choice of induction agent affect outcome?

Postoperative nausea and vomiting (PONV) has many causes, including anaesthetic drugs. Choice of induction agent may affect the incidence of PONV, though the evidence is conflicting. We have analysed our database of outcome after surgery. Data on 4173 patients were analysed using multivariate logistic regression, with an overall incidence of PONV 21.3%. Propofol, when compared to thiopentone for induction of anaesthesia, resulted in an 18% reduction in PONV (OR = 0.82, P = 0.03). The likely postoperative benefits of propofol may outweigh concerns about its additional cost.

Serum lipid and glucose concentrations with a propofol infusion for cardiac surgery.

OBJECTIVE: To document changes in serum lipids and glucose with a propofol infusion technique for cardiac surgery. DESIGN: Prospective cohort. SETTING: University teaching hospital. PARTICIPANTS: 22 elective cardiac surgical patients. INTERVENTIONS: Frequent venous blood sampling. MEASUREMENTS AND MAIN RESULTS: Serum lipids and glucose were measured at 10 time periods perioperatively, from preinduction until 4 hours post-cardiopulmonary bypass. Plasma propofol concentrations were also measured in 10 of these patients. There was a significant increase in glucose (P < 0.0005) and decreases in cholesterol (P < 0.0005), high-density lipoprotein (P = 0.004), and low-density lipoprotein (P < 0.0005); there was no significant change in triglycerides (P = 0.39). The propofol infusion resulted in acceptable plasma levels throughout the procedure and allowed early extubation in the intensive care unit, after a mean (SD) of 7.14 (5.9) hours. There was a strong correlation between triglyceride and propofol levels at most time periods (r = 0.38 to 0.98). CONCLUSIONS: This study demonstrates that a propofol infusion technique does not result in elevation of serum lipids and supports its increased popularity in maintenance of anesthesia for cardiac surgery.

Anaesthesia for adults with cystic fibrosis.

Cystic fibrosis is an autosomal recessive disorder which affects one in 2500 live births. It is a multisystem disease and has a variety of presentations. The major clinical features affect the gastrointestinal and respiratory tracts. Severe respiratory disease, diabetes and gastroesophageal reflux are common features of concern to anaesthetists. Improved care of young patients has allowed many to survive into adulthood. Lung transplantation has significantly improved the outlook for many patients. At Alfred Hospital, 74 patients with cystic fibrosis underwent 149 procedures from January 1978 to January 1994, with a mortality of 0.6% (95% CI 0.4%-0.8%). This retrospective cohort study describes the anaesthetic management and perioperative care of these patients. Most of the anaesthetics were for procedures related to cystic fibrosis but 12% were for unrelated conditions. Cystic fibrosis related procedures include diagnostic, venous access, enteral feeding procedures, treatment of complications of cystic fibrosis and lung transplantation. Despite extremely poor respiratory function, these patients can be managed with acceptably low postoperative mortality (1%). Pre- and postoperative care must be directed towards optimal clearance of viscous respiratory secretions. Procedures need to be planned so that optimal care can be given by each member of the team caring for cystic fibrosis patients.

Comparison of patient-controlled analgesia and nurse-controlled infusion analgesia after cardiac surgery.

A randomized, controlled clinical trial was conducted on 72 patients undergoing elective cardiac surgery to compare patient-controlled analgesia (PCA) to nurse-titrated infusion of morphine. Pain and nausea scores were assessed at 5, 20, 32 and 44 hours after cardiopulmonary bypass. Serum cortisol estimations were performed at 24 and 48 hours, and morphine consumption was measured at 0-24 and 24-48 hours. There was no difference between pain scores (P = 0.72), nausea scores (P = 0.52), serum cortisol at 24 and 48 hours (P = 0.32 and P = 0.34), and morphine consumption at 0-24 and 24-48 hours (P = 0.16 and P = 0.12). There was also no difference in the time to tracheal extubation (P = 0.79) and discharge from ICU (P = 0.64). There was a significant association between pain and serum cortisol at 48 hours (P = 0.023). This study also found a tenfold difference in the amount of morphine used (range = 11 to 108 mg), with no significant association with patient age or sex. We could find no significant benefit from the routine use of PCA in cardiac surgical patients.

Chemical dependence in anaesthetic registrars in Australia and New Zealand.

The Supervisors of Anaesthetic Training in Australia and New Zealand were surveyed and asked to report any cases of chemical dependence from anaesthetic registrars at their hospital from 1981 to 1991. From 83 questionnaires there were 65 (78%) returned. There were 14 departments (22%) with experience of one or more cases during this interval. Only five (7%) reported conducting a lecture or tutorial on the problem. The departmental reports covered 4425 registrar years of training and there were 17 cases reported. Of these, 13 were complete and are considered in detail. It is estimated that 1.3% of those who entered anaesthetic training during the interval were recognised to become chemically dependent during their training. Follow-up was available on only six of the 13 registrars and only one was reported to have completed training. The results of this survey indicate that chemical dependence is already a major health problem amongst anaesthetic registrars in Australia and New Zealand.

Effect of "renal-dose" dopamine on renal function following cardiac surgery.

The efficacy of renal-dose dopamine to improve renal function or reduce renal impairment was studied in 52 patients undergoing elective coronary artery bypass surgery. The patients were prospectively randomised in a double-blind fashion to receive dopamine at 200 micrograms/min (group D) or placebo (group P) from induction for 24 hours. Although dopamine improved haemodynamics, there was no effect on urine output at 4 hours (D = 917, P = 1231 ml: P = 0.066); urine output at 24 hours (D = 3659, P = 3304 ml: P = 0.36); creatinine clearance at 0-4 hours (D = 104, P = 127 ml/min: P = 0.27); creatinine clearance on admission to ICU-4 hours (D = 94.8, P = 83.4 ml/min: P = 0.48); creatinine clearance at 20-24 hours (D = 91.2, P = 107 ml/min: P = 0.48); free-water clearance at 0-4 hours (D = 29.6, P = -59.8 ml/hr: P = 0.069); free-water clearance at 20-24 hours (D = 43.2, P = -48.9 ml/hr: P = 0.55). The incidence of transient renal impairment was similar in both groups (D = 36%, P = 50%: P = 0.65). Our study failed to demonstrate that routine prophylactic renal-dose dopamine is associated with improvement in renal function, or with prevention of transient renal impairment in patients undergoing coronary artery bypass surgery.

Single versus double occlusive dressing technique to minimize infusion thrombophlebitis: Vialon and Teflon cannulae reassessed.

Infusion thrombophlebitis is the commonest complication of intravenous cannulation. This study was undertaken to prospectively evaluate a double-occlusive dressing technique and a new cannula, bismuth oxide-Teflon (Critikon Inc., Aust.), comparing it to Vialon (Deseret Medical Inc., Utah, USA). The study group of two hundred patients had a 16 gauge intravenous cannula inserted in theatre using a standard technique. The incidence of thrombophlebitis was determined on a daily basis. Cannula tips were sent for culture on removal. Vialon was found to be superior to Teflon after day 1. Although a double-occlusive dressing technique increased the duration of cannulation (50.9 vs. 41.9 hours, P less than 0.05), there was no difference in the incidence of thrombophlebitis. Neither cannula material nor dressing technique had an influence on the results of cannula tip culture (6% incidence). There was no evidence of bacteraemia in any case.