Near-patient testing for coagulopathy after cardiac surgery.

BACKGROUND: We assessed the accuracy and precision of a new near-patient testing system (Hemochron Response) by measuring prothrombin time and activated partial thromboplastin time (PT and APTT) in 50 patients undergoing cardiac surgery using cardiopulmonary bypass and comparing the results with laboratory assays. METHODS: Blood samples were taken at the beginning of surgery and the PT and APTT was measured both in the laboratory and by the Hemochron Response. The tests were repeated 30 min after reversal of heparin with protamine. RESULTS: Before bypass, the bias for PT was only +0.34, with small 95% limits of agreement. Making the same measurements after bypass, the Hemochron Response under-read and the bias was -3.27, with an increase of the 95% limits of agreement. With the APTT, the bias and the 95% limits of agreement were greater before bypass, and became even wider after bypass. CONCLUSIONS: We found good agreement in the PT and clinically acceptable levels of agreement in the APTT during the pre-bypass period. After bypass, bias became greater for both PT and APTT and the limits of agreement could be clinically unacceptable.

Anaesthesia for cardioversion: a comparison of sevoflurane and propofol.

This study compared the induction time, haemodynamic changes, recovery characteristics and patient satisfaction for sevoflurane and propofol when used as the main anaesthetic agents for cardioversion. Sixty-one unpremedicated patients scheduled for elective cardioversion were anaesthetised with either inhaled sevoflurane 8% or an intravenous propofol target-controlled infusion set at 6 microg.ml(-1). There was no significant difference in induction time between the two groups: mean (SD) = 90.1(40) s in the sevoflurane group vs. 83.7(35) s in the propofol group. Mean (SD) time to recovery was significantly shorter in the sevoflurane group than in the propofol group: 318 (127) s vs.738 (355) s, respectively, p < 0.001. At recovery, the patients in the propofol group had significantly lower systolic and diastolic blood pressures than those in the sevoflurane group, p < 0.001. The incidence of complications was low in both groups, with similar patient satisfaction expressed after the procedure. We conclude that sevoflurane is a suitable choice for anaesthesia for cardioversion and may provide greater haemodynamic stability than a target-controlled infusion of propofol.

No response to trigger agents in a malignant hyperthermia-susceptible patient.

Malignant hyperthermia susceptibility is an inherited disorder, where a life-threatening condition can result from exposure to a trigger agent or agents. Succinylcholine and volatile anaesthetic agents are well established to be trigger agents in anaesthetic practice. We describe a case of a previously investigated malignant hyperthermia-susceptible patient who did not declare his status and was exposed to both succinylcholine and isoflurane, without any detectable reaction. Possible explanations for the lack of reaction include a subnormal temperature when exposed to isoflurane, and a significant interval between exposure to succinylcholine and isoflurane. Absence of a reaction to trigger agents on this occasion is not thought to indicate an incorrect diagnosis and labelling.

Incremental spinal anaesthesia for elective Caesarean section in a patient with Eisenmenger's syndrome.

We describe a new approach to anaesthesia for elective Caesarean section in a woman with Eisenmenger's syndrome. Incremental regional anaesthesia was performed using a microspinal catheter and haemodynamic monitoring included transthoracic bioimpedance cardiography. This approach allowed the disadvantages of general anaesthesia and invasive cardiac output monitoring to be avoided.

Autotransfusion in cardiac surgery.

There are a number of problems with allogeneic blood transfusion. Some of these problems are defined and can be quantified, such as the problem of rising cost or the risk of viral infection, but some of the problems are not well defined and it is only outcome data that point to allogeneic blood transfusion contributing to patient mortality and morbidity. Autotransfusion includes any technique in which the patient's own blood is collected, processed and stored, followed by reinfusion when circumstances dictate. In the perioperative period of cardiac surgery, a number of techniques are recognized as useful in this context. Preoperative autologous donation, with or without erythropoietin supplementation, intraoperative acute normovolaemic haemodilution, intraoperative cell salvage, postoperative cell salvage (reinfusion of shed mediastinal blood) and platelet rich plasmapheresis are all techniques which are used with more or less enthusiasm to reduce the need for an allogeneic blood transfusion. Modification of the priming technique of the cardiopulmonary bypass circuit using an autologous blood prime is included in this review even though it does not fall strictly within the definition of autotransfusion. Although autotransfusion is not the answer to every problem, there is no doubt that it should play a significant part in the strategy of blood conservation.

Cell salvage and leucodepletion.

Cell salvage has been used as a method of blood conservation for more than three decades. Although the principles and development of the Latham bowl had occurred in the 1960s, it was not until the early 1970s that washing of the concentrated red cells was introduced and a product that was universally acceptable was obtained. The last 25 years have seen little in the way of development of cell salvage, although significant refinement has taken place. Although the simple picture of cell salvage involves removal of the buffy coat, including platelets and leucocytes, in practice there are reports of great variation in the removal of these cells. Most recent studies suggest that there is very little removal of leucocytes by cell salvage. The leucocytes that remain in the red cell suspension following cell salvage have undergone significant morphological changes and the surface expression of leucocyte adhesion receptors increases dramatically during the process. There is little evidence that removal of these activated leucocytes has any significant clinical benefit. Although leucofiltration of blood before storage has been shown to be an extremely safe process, 'bedside leucofiltration', including leucofiltration of cell salvage blood, may not be without problems. Reports of hypotensive events while receiving blood products through a bedside leucocyte reduction filter have emerged during the last few years. This may be due to bradykinin production following platelet exposure to negatively charged leucocyte filters.

Redo cardiac surgery in a Jehovah's Witness, the importance of a multidisciplinary approach to blood conservation.

Although Jehovah's Witnesses present a particular problem when undergoing surgery because of their refusal to accept stored blood, it is now quite common to undertake uncomplicated cardiac surgery in these patients. Complex or redo cardiac surgery however, is often associated with major blood loss, and is conventionally contraindicated in Jehovah's Witnesses. We describe the perioperative management of a Jehovah's Witness who underwent a resternotomy for mitral valve replacement and coronary artery bypass grafting having previously had an aortic valve replacement and mitral valve repair. The importance of a multidisciplinary approach to blood conservation is discussed.

Cardiovascular responses to pulmonary artery catheterization.

This study compares prospectively the cardiovascular and catecholamine responses to central venous and pulmonary artery catheterization before and after induction of general anaesthesia. Twenty patients for elective coronary artery surgery were randomized into two groups. One group had central venous and pulmonary artery catheterization performed awake using local anaesthesia. The other group had these catheters inserted following induction of general anesthesia. In all patients heart rate, arterial blood pressure, ST segment analysis and epinephrine and norepinephrine levels were measured prior to central venous cannulation and at 2-min intervals until placement of the lines was achieved. There were no statistically significant changes in any cardiovascular or catecholamine variable with time compared with the base-line measurements. There were no statistically significant differences in plasma catecholamine levels between the awake and the anaesthetized groups.

Blood glucose reagent strip tests in the operating room: influence of hematocrit, partial pressure of oxygen, and blood glucose level--a comparison of the BM-test 1-44, BM-Accutest, and Satellite G reagent strip systems.

OBJECTIVE: The objective of our study was to assess the influence of hematocrit (HCT), partial pressure of oxygen (PO2), and blood glucose level upon results obtained with three different blood glucose reagent strip tests used in conjunction with the appropriate meter: BM-Test 1-44, BM-Accutest, and Satellite G. METHODS: Our study was designed as a consecutive sample study of patients undergoing coronary artery surgery. The setting was the hospital theater and intensive care unit. We conducted blood analysis for HCT, PO2 and blood glucose on 20 consecutive patients undergoing coronary artery surgery using three blood glucose reagent strip testing systems and a laboratory analysis of plasma glucose. RESULTS: All three blood glucose reagent strip tests showed a significant bias when compared with plasma glucose: BM-Test 1-44, 0.89 mmol/L; BM-Accutest, -1.27 mmol/L; Satellite G, 0.75 mmol/L (p < 0.05). The error found when using the Satellite G system was worse than that of either of the other two systems. Results obtained with the BM-Accutest strips were unaffected by PO2 (p = 0.745). Blood glucose value and HCT both had an influence on the results of all three blood glucose strip systems. CONCLUSIONS: Caution must be taken when using reagent strip systems in the operating room or intensive care setting because, of the three systems tested, all showed a significant bias, all were influenced by blood glucose level and HCT, and only the BM-Accutest reagent strips used with the Accutrend meter was unaffected by PO2.

Hormonal effects of thoracic extradural analgesia for cardiac surgery.

We have investigated the hormonal and metabolic effects of thoracic extradural analgesia with bupivacaine in addition to sufentanil 20 micrograms kg-1 in nine patients undergoing coronary artery bypass surgery. A control group received general anaesthesia alone. The catecholamine response was inhibited for 24 h after surgery in patients who had received extradural analgesia, and the cortisol response was suppressed during cardiopulmonary bypass. Blood glucose values were unchanged until 24 h after surgery in the extradural group. There were no significant differences in cardiac index between the two groups of patients, although heart rate and mean arterial pressure decreased before surgery in patients who received extradural analgesia. The benefits of this technique in terms of a reduction in postoperative morbidity remain to be determined.

Rhodium(III) as a potentiator of the effects of X-rays on cells.

A rhodium compound, Rh(NH3)3Cl3, does not sensitize the spores of Bacillus megaterium to X-rays. However, it is a very effective sensitizer of vegetative cells of Staphylococcus aureus, raising the sensitivity four times in O2 and over 100 times in anoxia. The inhibition by oxygen of the sensitizing action of Rh(III), which operates over a wide range of [O2], is noteworthy. These experiments were performed in saline-phosphate buffer using 50 kVp X-rays. The results are discussed in terms of the known radiation chemistry of this compound.