Randomized clinical trial to determine the effect of nasogastric drainage on tracheal acid aspiration following oesophagectomy.

BACKGROUND: The aim of this study was to investigate tracheal acid aspiration after oesophagectomy and to determine whether it is influenced by nasogastric (NG) drainage. METHODS: Thirty-four patients undergoing oesophagectomy were randomized to one of three methods of NG drainage: a single-lumen tube with free drainage and 4-hourly aspiration, a sump-type tube on continuous suction drainage, or no NG tube. A tracheal pH probe was used to collect information on acid aspiration for 48 h after surgery. A pH < 5.5 was considered abnormal (normal pH 6.8-7.2). Total time with tracheal pH < 5.5, number of reflux episodes and longest reflux time were compared between groups. RESULTS: There was significant and persistent tracheal acid aspiration in all patients. Patients with a sump-type tube had a significantly shorter total time with tracheal pH < 5.5 than those in the other groups (sump-type tube versus single-lumen tube, P = 0.0069; sump-type tube versus no tube, P = 0.0071). Patients randomized to no NG tube experienced more respiratory complications after surgery than those who had either single-lumen or sump-type tubes (seven of 12 versus four of 22 patients; P = 0.023). Insertion of a NG tube was necessary in the first week after surgery in seven of 12 patients in this group. CONCLUSION: Routine NG drainage after oesophagectomy is necessary. A sump-type NG tube is better at preventing tracheal acid aspiration and may reduce the incidence of respiratory complications.

The effect of gel lubrication on cuff leakage of double lumen tubes during thoracic surgery.

High-volume, low-pressure tracheal cuffs of disposable double lumen tubes may offer limited protection to the dependent lung if fluid leaks through folds in the inflated cuffs. This study was undertaken to determine the incidence of fluid leakage past the tracheal cuff and whether gel lubrication reduces the incidence. Fifty-five patients were randomly assigned to receive a double lumen tube with or without gel lubrication. The dependent lung was intubated. With the patient in the lateral position, methylthionium chloride was administered above the tracheal cuff via a pre-attached catheter. Fibreoptic bronchoscopy was performed to determine if dye had passed the tracheal cuff. Three patients were excluded. Dye leakage was seen in 12/27 and 3/25 patients in the unlubricated and lubricated group, respectively (p = 0.014). Gel lubrication significantly reduces fluid leakage past the tracheal cuff of a double lumen tube and should be considered for all thoracic surgical patients requiring one-lung ventilation.

Double-blind comparison of intrapleural saline and 0.25% bupivacaine for ipsilateral shoulder pain after thoracotomy in patients receiving thoracic epidural analgesia.

BACKGROUND: The aim of this prospective double-blind randomized placebo-controlled study was to investigate the effect of intrapleural bupivacaine on ipsilateral post-thoracotomy shoulder pain in patients receiving thoracic epidural analgesia. METHODS: Of the 68 patients recruited to the study, 41(60%) developed ipsilateral shoulder pain within 2 h of surgery. These patients were randomly assigned to receive either 40 ml of intrapleural bupivacaine 0.25% with epinephrine 1:200 000 or 40 ml of intrapleural saline. The study solution was injected into the tube of a basal drain that had been clamped distal to the site of administration. Shoulder pain at rest and on coughing was assessed using a visual analogue scale (VAS) and an observer verbal rating score (OVRS) immediately before and 30 min, 1 h, 2 h, 3 h and 4 h after intrapleural bupivacaine/saline. The total volume of epidural solution administered was recorded. RESULTS: Thirty-nine patients completed the study and were included in the analysis. There were no significant differences in baseline characteristics between the two groups. There were no significant differences between groups for VAS or OVRS pain scores at rest or with cough at any of the six assessment times. The total volumes of epidural solution administered to the bupivacaine and saline groups were 56 ml and 48 ml, respectively. This difference was not significant. CONCLUSION: Intrapleural administration of 40 ml of bupivacaine 0.25% does not provide effective pain relief for ipsilateral post-thoracotomy shoulder pain.

A prospective, randomised, single-blind pilot study to determine the effect of anaesthetic technique on troponin T release after off-pump coronary artery surgery.

Ischaemic damage to the myocardium inevitably occurs during coronary artery surgery. However, the extent of the damage may be influenced by the anaesthetic technique used. The most sensitive and reliable marker of myocardial damage is currently thought to be troponin T. We conducted a prospective, randomised, single-blind pilot study to determine the baseline values of troponin T release after off-pump coronary artery bypass surgery in 30 patients randomly allocated to receive either propofol, isoflurane or isoflurane and high thoracic epidural analgesia. All other treatment was standardised. Patients undergoing emergency surgery and those with unstable angina were excluded. Blood samples were taken at 0, 3, 6, 12, 24 and 48 h after surgery for troponin T analysis. Mean troponin T levels at 24 h were not significantly different between the groups (p = 0.41). These data allows appropriate power calculations for further, large-scale studies to determine the anaesthetic technique that provides optimal myocardial protection.

Infection control measures for adult cardiac surgery in the UK--a survey of current practice.

The aim of the study was to define current UK practice for antimicrobial prophylaxis and preoperative screening for bloodborne viruses and methicillin-resistant Staphylococcus aureus (MRSA) before routine cardiac surgery. An e-mail survey was sent to the Association of Cardiothoracic Anaesthetists (ACTA) Linkmen in all 36 UK adult cardiac surgical units, during May 2001. Questions were asked regarding MRSA, hepatitis B, C and human immunodeficiency virus (HIV) screening. Regarding antimicrobial prophylaxis questions were asked regarding agent(s), dose, frequency and duration of use for coronary artery and value surgery. Responses were received from 29 units (response rate 81%). There was a wide variety of practices for all units surveyed. For MRSA screening, 19 units (65%) screened all patients before surgery, but two (7%) screened none, with the remaining eight units (28%) screening selected high-risk groups. Regarding screening for bloodborne viruses: eight units (28%) tested all patients routinely for hepatitis B, 11 units (39%) selectively tested only high-risk patients and transplant recipients. No units tested for hepatitis C and HIV infection routinely. All units used prophylactic antibiotics routinely, but the type and number of agents, along with dose and duration of therapy all varied widely. For coronary artery bypass graft (CABG) surgery, a single agent was used by 16 units (55%), two agents by 12 units (41%) and three agents by one unit (4%). There is a wide variation in infection control practice in adult cardiac units throughout the UK. Rationalization of preoperative screening and use of prophylactic antibiotics, by adopting nationally agreed practice guidelines, could significantly reduce costs and potentially reduce the incidence of resistant organisms.

Gastric emptying in post-thoracotomy patients receiving a thoracic fentanyl-bupivacaine epidural infusion.

BACKGROUND AND OBJECTIVE: The effect of anaesthesia and surgery on gastric emptying is not constant, and this has not been previously studied in patients undergoing thoracotomy for lung resection with a bupivacaine-fentanyl epidural infusion for analgesia. There are important implications in this group of patients with regards to the recommencement of important oral medication as well as the risks of aspiration of gastric contents. The study examined gastric emptying in these patients until the second postoperative day. METHODS: In a prospective repeated measures study, the effect of fentanyl-bupivacaine epidural analgesia at the mid-thoracic level on gastric emptying was assessed in 11 patients undergoing thoracotomy for lung resection. Gastric emptying was measured using a paracetamol absorption technique. Patients acted as their preoperative controls and were assessed 4 h postoperatively and on the second postoperative day. RESULTS: The mean (SEM) maximum plasma paracetamol concentration was 204.6 (20.4) micromol L(-1) before operation, 61 (9.5) micromol L(-1) 4 h postoperatively and 114.3 (22.6) micromol L(-1) on the second postoperative day. Mean (SEM) paracetamol absorption at 120 min was 15,638 (1441) micromol min L(-1) preoperatively, 5731 (821) micromol min L(-1) 4 h postoperatively and 9325 (1759) micromol min L(-1) on the second postoperative day. Postoperative values were significantly (P < 0.005) less than the preoperative values. CONCLUSIONS: After thoracotomy, gastric emptying was delayed until at least the second postoperative day in patients receiving mid-thoracic fentanyl-bupivacaine epidural analgesia.

Isoflurane and coronary heart disease.

Early studies indicated that isoflurane caused coronary steal and should therefore be avoided in patients with coronary heart disease. Subsequently, more detailed trials have disputed this and have shown that as long as coronary perfusion pressure is maintained, isoflurane does not cause coronary steal or myocardial ischaemia. There is now growing evidence, initially in animal work but more recently in human studies, that isoflurane has myocardial protective properties, limiting infarct size and improving functional recovery from myocardial ischaemia. The mechanism for this protection mimics ischaemic preconditioning and involves the opening of adenosine triphosphate-dependent potassium channels. The few studies comparing the myocardial protection offered by individual anaesthetic agents indicate that isoflurane represents the anaesthetic agent of choice for patients with coronary heart disease.

Induction of anaesthesia in patients with coronary artery disease: a comparison between sevoflurane-remifentanil and fentanyl-etomidate.

In a prospective, randomized study, sevoflurane-remifentanil (Group SR) was compared with fentanyl-etomidate (Group FE) for induction of anaesthesia in patients with ischaemic heart disease. Cardiovascular stability, heart rate, mean arterial pressure, rate pressure product, rescue medications and associated myocardial ischaemia were measured. For Group SR (n = 20), anaesthesia was induced with vital capacity breaths of sevoflurane 5% in oxygen. After loss of consciousness, the inspired sevoflurane was reduced to 3% and remifentanil was administered as a 0.5 microgram.kg-1 bolus over 90 seconds (0.33 microgram.kg-1.min-1) followed by a 0.025 microgram.kg-1.min-1 infusion. After intubation, the inspired sevoflurane was reduced to 2%. For Group FE (n = 20), anaesthesia was induced with fentanyl 10.5 micrograms.kg-1 and etomidate 0.2 mg.kg-1 given 60 seconds later. Isoflurane 1% in oxygen was administered after loss of consciousness. Both groups received rocuronium and the trachea was intubated two minutes later. Sevoflurane gaseous induction was smooth, with cardiovascular stability comparable to fentanyl-etomidate. Significantly more patients in Group SR (P < 0.05) were on beta-blocking medication, and, overall, the HR and RPP was lower pre-intubation in Group SR. Remifentanil administration was associated with severe bradycardia in three patients and asystole in a fourth. All four patients were on beta-blocking medication and three of the four were on diltiazem. The study was terminated due to the high incidence of bradycardic/asystolic complications in Group SR.

Myocardial ischaemia after coronary artery bypass grafting: early vs late extubation.

The technique of early extubation after coronary artery bypass grafting is increasing in popularity, but its safety and effect on myocardial ischaemia remain to be established. In a randomized, prospective study, patients undergoing routine elective coronary artery bypass grafting were managed with either early or late tracheal extubation. The incidence and severity of electrocardiographic myocardial ischaemia were compared. Data were analysed from 85 patients (43 early extubation; 42 late extubation). Median time to extubation was 110 min in the early extubation patients and 757 min in the late extubation patients. After correction for randomization bias, there were no significant differences between groups in ischaemic burden, maximal ST-segment deviation, incidence of ischaemia and area under the ST deviation-time curve (integral of ST deviation and time). Similarly, there were no differences between groups in postoperative creatine kinase MB-isoenzyme concentrations and duration of stay in the ICU or hospital. Therefore, this study provides evidence for the safety of early extubation after routine coronary artery bypass grafting.

Gastroesophageal reflux and tracheobronchial contamination after cardiac surgery: should a nasogastric tube be routine?

Nasogastric (NG) tubes are routinely used in patients undergoing cardiac surgery. This randomized study was designed to assess gastroesophageal reflux (GER) without a NG tube (control) compared with a NG tube managed either by gravity drainage (gravity) or continuous low-grade suction (suction). Antimony pH probes were placed in the lower esophagus and trachea after induction of anesthesia in 51 patients, and pH was recorded every 5 s until the time of tracheal extubation. GER was defined as reversible decrease in esophageal pH to less than 4.0. No significant difference was found between groups in age, weight, gender, duration of postoperative ventilation, morphine use, or antiemetic use. All indicators of GER were seen more frequently in the gravity group compared with the two other groups (P < 0.001). One episode of sudden decrease in tracheal pH was observed in a patient in the gravity group, indicating tracheal aspiration, which was associated with delayed extubation and postoperative pneumonia. The absence of a NG tube is not associated with reflux, probably since the gastroesophageal sphincter remains competent. NG tubes are not routinely necessary for cardiac surgery in patients without risk factors for GER, and increase reflux risk if managed without low-grade suction.

Is this patient fit for thoracotomy and resection of lung tissue?

Central to risk assessment for lung resection is the fact that surgery offers the only chance of long-term survival and cure in non-small carcinoma of the lung. The challenge is, therefore, to offer surgery to as many patients as possible, whilst avoiding the risk of death from postoperative respiratory failure. Risk assessment is based on careful evaluation of the patient's existing cardiac and respiratory disease. The use of a cardiac risk index, such as that described by Detsky, will ensure that cardiac risk factors are recognised and, where possible, ameliorated prior to surgery. Pre-existing respiratory disease may be assessed by arterial blood gas analysis, exercise testing, whole and regional lung function tests. Criteria based on these tests have been proposed to aid patient selection prior to lung resection. However, these criteria take no account of the beneficial influence on outcome of modern anaesthesia and postoperative care. The elimination of postoperative pain, along with techniques such as minitracheostomy and incentive spirometry have allowed surgery to be offered to many patients who would have been deemed unsuitable by standard criteria. Patients with potentially resectable lung cancer must never be arbitrarily excluded from surgery on the basis of any single criteria or test. Referral for assessment by an experienced team consisting of a thoracic physician, surgeon and anaesthetist will maximise the number of patients offered surgery for this otherwise incurable disease.

Pancuronium or vecuronium for treatment of shivering after cardiac surgery.

This randomized double-blind study compared the hemodynamic and metabolic effects of pancuronium and vecuronium during treatment of shivering after cardiac surgery with hypothermic cardiopulmonary bypass. Thirty sedated and pain-free patients who shivered after cardiac surgery were treated with pancuronium (n = 15) or vecuronium (n = 15) 0.08 mg/kg. Baseline values of heart rate (HR), mean arterial pressure, arterial and venous blood gases, total body oxygen consumption indexed to body surface area (VO2-I), and pressure work index (PWI, an estimate of myocardial oxygen consumption) were measured on arrival in the intensive care unit, at onset of shivering, and repeatedly for 2 h after treatment. Continuous ST segment analysis of leads II and V5 were used for detection of myocardial ischemia. Treatment of shivering with pancuronium decreased VO2-I by 32% (P = 0.0001). This was accompanied by a 14% increase in HR (P = 0.001) and a 10% increase in PWI (P = 0.03). Vecuronium decreased VO2-I by 36% (P = 0.003) with a 4% decrease in HR (P = 0.04) and a 6% decrease in PWI (P = 0.06). Myocardial ischemia (n = 3) and ventricular arrhythmias (n = 3) occurred in five patients treated with pancuronium. Only one patient treated with vecuronium had ventricular arrhythmia (P = 0.08). Seven patients treated with pancuronium and eight treated with vecuronium were taking beta-adrenergic blockers preoperatively which was associated with lower HR (96 +/- 16 vs 109 +/- 15 bpm; P = 0.025) and lower PWI (8.8 +/- 1.2 vs 10.7 +/- 1.92 mL.min-1 x 100 g-1; P = 0.003) at onset of shivering. However, beta-adrenergic blockers did not attenuate the relative HR increase induced by pancuronium. No relationship was found between hypercapnia and tachycardia or hypertension. These results suggest that, when compared to pancuronium for treatment of postoperative shivering, vecuronium may be advantageous because it does not increase myocardial work. The disproportionate relationship between VO2-I and PWI after treatment with muscle relaxants indicates that increased VO2-I does not contribute significantly to the hemodynamic disturbances associated with shivering. These disturbances are more likely the results of increased adrenergic activity related to pain and recovery from anesthesia. Shivering and its associated hemodynamic disturbances appear to be concomitant but independent signs of awakening.

Variation in the arterial to end-tidal PCO2 difference during one-lung thoracic anaesthesia.

We have measured the arterial to end-tidal PCO2 difference (PaCO2-PE'CO2) in 22 patients undergoing pulmonary resection in the lateral thoracotomy position during two-lung ventilation (TLV) and after transition to one-lung ventilation (OLV). With OLV for each patient, the practice of correcting the estimate by an initial measurement of (PaCO2-PE'CO2) was evaluated by subtracting the initial (PaCO2-PE'CO2) from subsequent values measured at 10-min intervals. Net (uncorrected) and corrected differences during OLV were analysed using ANOVA. (PaCO2-PE'CO2) values during TLV and OLV were similar: mean (SD) 1.3 (0.6) kPa and 1.2 (0.7) kPa, respectively (ns). Mean (PaCO2-PE'CO2) varied in the range 0.2-2.5 kPa, while maximum (PaCO2-PE'CO2) was 0.3-2.8 kPa. The mean (SD) of 133 pairs of measurements with OLV was 1.1 (0.7) kPa. Even after correction, mean (PaCO2-PE'CO2) varied in the range -0.7 to 0.8 kPa; individual extreme values were from -1.3 to 1.7 kPa. Variation between patients was found to be greater than variation within patients for both net and corrected differences (F ratio = 37.0 and 10.9, respectively), although calculating a corrected difference did reduce variation between patients from a mean square value of 2.44 to 0.61. The wide variation in (PaCO2-PE'CO2) suggests that the accuracy of estimation of PaCO2 by monitoring PE'CO2, although improved by the use of a corrected difference, remains questionable during OLV.

The effect of cardiopulmonary bypass on cholinesterase activity.

Cholinesterase activity was determined in 18 patients who had undergone either hypothermic (n = 9) or normothermic (n = 9) cardiopulmonary bypass. The anaesthetic technique was standardised to avoid agents known to affect cholinesterase. Activity was determined in blood samples taken before the induction of anaesthesia, during cardiopulmonary bypass and for at least 7 days postoperatively. In six patients cholinesterase activity was also measured at 6 weeks postoperatively. All the patients were of normal cholinesterase genotype. In both groups cholinesterase activity fell by approximately 60% coinciding with the start of cardiopulmonary bypass, from a mean of 5976 to 2636 IU.l-1 in the hypothermic group, and from 5901 to 2615 IU.l-1 in the normothermic group (p < 0.001 in both instances) (normal range 4300-10,500 IU.l-1). Cholinesterase activity remained at this reduced level for at least 7 days postoperatively. By 6 weeks, activity had returned to within 7% of pre-induction values. There were no differences in cholinesterase activity between the hypothermic and normothermic groups at any of the sampling times.

Hard-shell cardiotomy reservoir for reinfusion of shed mediastinal blood.

We conducted a prospective, randomized, controlled trial comparing homologous blood consumption between groups of patients receiving conventional mediastinal drainage (group 1) or reinfusion of shed mediastinal blood (group 2) using hard-shell cardiotomy reservoir. One hundred consecutive patients who had elective coronary artery or valvular operations were studied. The two groups were comparable with regard to age, sex, weight, preoperative and postoperative hemoglobin levels, and surgical procedure. Group 2 patients had their shed mediastinal blood reinfused for up to 18 hours postoperatively; otherwise, the two groups were treated identically. For groups 1 and 2, average mediastinal blood losses were 705 +/- 522 and 822 +/- 445 mL and homologous blood consumption was 3.83 +/- 2.58 and 3.15 +/- 2.05 U, respectively (neither measure was significantly different). However, if blood losses exceeded 500 mL, there was a statistically significant reduction in homologous blood requirements in group 2 as compared with matched controls in group 1. This difference was most significant in patients with the greatest mediastinal losses.

Propofol-fentanyl anaesthesia for coronary artery surgery and cardiopulmonary bypass.

A two-stage propofol infusion combined with fentanyl was used to maintain anaesthesia during coronary artery surgery in patients with good ventricular function. Whole blood propofol concentrations were measured at frequent intervals; plasma protein binding was measured before, during and after cardiopulmonary bypass. An initial infusion rate of 10 mg/kg/hour provided good protection from the pressor response to sternotomy. A predictable steady state concentration was achieved in the prebypass period with a maintenance infusion rate of 3 mg/kg/hour. The onset of bypass resulted in a small decrease in propofol concentration as a result of haemodilution. Induced hypothermia resulted in an increase in propofol concentration which returned rapidly to the prebypass steady state value during rewarming. The free propofol fraction increased during cardiopulmonary bypass. No patient had any recall of operative events or required inotropic support during weaning from bypass.

Homologous blood use and conservation techniques for cardiac surgery in the United Kingdom.

The transfusion laboratories of 32 cardiothoracic surgical centres for adults were surveyed to determine the donor blood requirement for open heart surgery in the United Kingdom. Details of the transfusion practice and the use of blood conservation techniques were sought from a representative senior cardiac anaesthetist at each centre. Suitable data were received from 24 transfusion laboratories (75%) and 29 anaesthetists (90%). The mean (SD) blood use was 5.07 (1.53) units per operation. Seven centres routinely transfused fresh frozen plasma to all patients postoperatively. Experience with autologous deposit (three centres), "cell separators" (four centres), and the reinfusion of shed mediastinal blood (four centres) was limited. Prebypass phlebotomy for postbypass reinfusion (14 centres) and the infusion of residual oxygenator blood (27 centres) were the conservation techniques most commonly applied. In only nine centres was a postoperative normovolaemic anaemia to a haemoglobin concentration of less than 100 g/l accepted. Applying blood conservation techniques more widely would help to maintain blood supplies and reduce morbidity and mortality related to transfusion.