Anaesthesia and Intensive Care

Postoperative changes in procoagulant, anticoagulant, and antifibrinolytic factors were compared in patients undergoing abdominal aortic surgery, carotid endarterectomy, and femoro-popliteal bypass. There were increases in plasma fibrinogen (P<0.01) and factor VIII coagulant (P<0.01) levels following all three procedures. There were decreases in antithromhin III (P<0.01) and protein C (P<0.01), and increases in thrombin-antithrombin complex levels (P<0.01) in the abdominal aortic group only. There were no significant changes in type 1 plasminogen activator inhibitor levels following any of the procedures. The results indicate that all three procedures are associated with an increased potential for thrombosis due to increases in procoagulant factors. However, patients undergoing abdominal aortic surgery are particularly at risk due to concurrent decreases in natural anticoagulant factors. Specific antithrombotic therapy should be considered for all patients undergoing vascular surgery, but particularly for those undergoing major procedures such as abdominal aortic surgery.

We aimed to evaluate the tonometer in the assessment of gastrointestinal ischaemia induced by an infrarenal aortic cross-clamp. Nine anaesthetized pigs were cannulated for haemodynamic monitoring and radionuclide labelled microsphere (RLM) injection. Gastric and sigmoid tonometers were positioned. After haemodynamic stabilization an infrarenal aortic cross-clamp was applied. Animals were sacrificed at the completion of the study and tissue sampled from the stomach and sigmoid colon for regional blood flow measurements. Measurements were made pre-clamp, post-clamp, pre-release and post-release. Haemodynamic parameters, gastric intramucosal pH (pHi) and blood flow did not change throughout the experiment. Arterial pH increased during cross-clamp and returned to baseline post-release. Arterial bicarbonate fell post release. Sigmoid blood flow fell during cross-clamp. The sigmoid pHi fall, delayed until pre-release, remained low post-release. Although there was a consistent fall in sigmoid pHi, 63% of post-clamp values remained within the baseline range. We conclude that maintaining haemodynamic parameters around baseline values resulted in maintenance of gastric mucosal perfusion as indicated by a steady gastric pHi. However, below the aortic cross-clamp, delay between change in sigmoid colon blood flow and change in pHi and wide variation in sigmoid pHi limits the value of an individual pHi measurement in detecting ischaemia.

Thrombelastographic evidence of hypercoagulability, including shortening of r-time (P< 0.01); shortening of k-time (P<0.01); and widening of trace angle (P<0.01) were observed in a group of 21 Chinese surgical patients when (a) the amount of blood loss was at an estimated 10% of total blood volume and (b) the amount of blood loss was at an estimated 15% of blood volume. The amount of blood loss was documented by haemoglobin measurements. No evidence of hypercoagulability was observed at around one hour into the operation in the absence of bleeding. We conclude that a mild to moderate degree of surgical blood loss with haemodilution is associated with the development of hypercoagulability as measured by thrombelastography. Further studies looking at the thrombebolic outcome in such groups of patients is warranted. It is also suggested that caution should be exercuised in the use of intraoperative isovolaemic haemoldilution until the phenomenon is further investigated.

The effects of bolus administration of propofol (50 mg, 100 mg and 200 mg) on cerebral blood flow and cerebral metabolic rate for oxygen were examined in a chronically catheterized sheep preparation. Depth of anaesthesia was simultaneously measured using a withdrawal response to a noxious electrical stimulus and it was demonstrated that the 100 mg dose induced moderate sedation while the 200 mg dose induced relatively deep anaesthesia. Propofol caused transient dose-dependent decreases in cerebral blood flow, despite minimal changes in blood pressure. These were accompanied by parallel decreases in cerebral metabolic rate but no change in cerebral oxygen extraction. As cerebrovascular responses in the sheep appear similar to those in man, the parallel changes in cerebral blood flow and metabolic rate demonstrated in this study supports the suitability of propofol as a neuroanaesthetic agent.

Low-dose ketamine by subcutaneous infusion (0.1 mg/kg/h) was compared in double-blind fashion with intermittent morphine (0.1 mg/kg intravenously, four-hourly) as analgesic regimen in 40 ASA-I adults after acute musculoskeletal trauma. Pain was assessed using visual analogue scales and sedation was graded on a four point rank drowsiness score. Objective cardiovascular and respiratory parameters and patient acceptability in terms of supplementary analgesia and early mobilization were also recorded. Pain relief was better with the ketamine infusion than with intermittent morphine (P< 0.001). Patients were more awake and alert with ketamine infusion as evidenced by the drowsiness score (P<0.001). Peak expiratory flow rate improved significantly with the ketamine infusion (P<0.05). None of the patients in ketamine group required supplementary analgesia (P<0.001) and the patients could be easily mobilized for traction/splintage as compared with patients in the control group (P<0.001). The incidence of nausea and vomiting in the morphine group was high (P<0.01). The study shows that subcutaneous infusion of ketamine provides safe and effective analgesia in acute musculoskeletal trauma.

We studied the effects of intraoperative use of air in oxygen (O₂) (FiO₂ = 0.33) versus nitrous oxide (N₂O) in O₂ (FiO₂ = 0.33) on the degree of postoperative hypoxaemia in 30 patients undergoing laparoscopic cholecystectomy. Patients were randomly allocated to receive either general anaesthesia with air (Group A, n=15) or with N₂O (Group N, n=15). Arterial gas tensions were measured before, 24h and 48h after surgery while breathing room air. The mean P_aO₂ 24h and 48h postoperatively decreased significantly in both groups compared with the preoperative values. The mean P_aO₂ 24h postoperatively in Group N (74.6±6.4 mmHg) tended to be lower than that in Group A (78.1±8.3 mmHg). The mean P_aO₂ 48h postoperatively in Group N (75.0± 7.8 mmHg) was significantly lower than that in Group A (83.5±7.9 mmHg) (P<0.05). On the contrary, the mean P_aCO₂ did not show any significant change during 48h postoperatively in either group. Our results suggest that ventilation with N₂O and O₂ during laparoscopic cholecystectomy is associated with a lower degree of postoperative hypoxaemia.

Pethidine and fentanyl have both been used to provide patient-controlled epidural analgesia (PCEA) following caesarean delivery. Both have been compared with epidural morphine but these drugs have not been compared with each other. Patient-controlled epidural analgesia was used in a prospective, randomized, double-blind, cross-over trial to compare fentanyl and pethidine for postoperative epidural analgesia in women having elective caesarean deliveries. Two groups received either PCEA fentanyl or pethidine with a cross-over to the other drug after 24 hours. Results from 45 patients showed no difference in pain level outcomes, but pethidine scored better in all side-effects except for drowsiness at 48 hours. Patients were more satisfied with pethidine (P=0.015) and overall 65% of patients preferred pethidine. We conclude that pethidine is a suitable drug for patient-controlled epidural analgesia and leads to greater patient satisfaction than does fentanyl.

We evaluated a disposable device (Baxter PCA Infusor) for patient-controlled epidural analgesia (PCEA) using pethidine in twenty women after lower segment caesarean section. Efficacy, as measured by visual analogue pain scores, was comparable with historical controls from PCEA studies using electronic devices. Three patients reported inadequate analgesia, attributable in two cases to problems with the epidural catheter. PCEA was stopped in one patient because of side-effects. Pethidine consumption ranged from 125 to 1500 mg (median 575 mg) in 48 hours. Plasma concentrations of pethidine varied widely. Disposable devices for PCEA after caesarean section provide an alternative to bolus administration or PCEA using more expensive and cumbersome electronic devices, although we suggest currently available apparatus requires modifications to improve clinical performance.

Percutaneous dilational tracheostomy (PDT), first described in the 1950s, has become a common bedside technique in the Intensive Care Unit (ICU). This study compares the early complications associated with the use of the Ciaglia PDT (Cook Critical Care, Bloomington, USA) technique, with the newly available Portex PDT technique (Portex Ltd., UK). The Ciaglia technique was adopted in this ICU in July 1994 and twenty-nine patients had a tracheostomy using this set until January 1995. Complications during the procedure were collected prospectively. When the Portex PDT set became available in January 1995, it was decided to assess the complication rate of this technique and compare them to the previously-collected data using the Ciaglia PDT set. Twenty-five patients have had a tracheostomy using the Portex PDT set. There has been no mortality associated with either PDT set. Bleeding requiring intervention occurred in two patients in the Ciaglia group and three patients in the Portex Group. All these patients had a bleeding diathesis. Loss of airway control occurred on one occasion in the Ciaglia group due to premature removal of the endotracheal tube. The first routine tracheostomy tube change at day 7 was complicated in four cases in the Ciaglia group. One infected stoma was noted in the Ciaglia group at day 7. Both techniques result in rapid, safe placement of a tracheostomy tube in critically ill patients in the ICU, obviating the need for surgical referral and transport to the operating room.

Echocardiography is fast becoming the technique of choice for noninvasive evaluation of left ventricular function in the critically ill patient. Current technology allows for assessment of overall left ventricular performance and for diastolic and systolic function. Doppler technology has greatly enhanced the diagnostic capability of two-dimensional echocardiography. The critical care physician should be aware not only of currently available techniques, but also those which will be used in the routine care of the critically ill subject in the foreseeable future.

The New South Wales Special Committee Investigating Deaths Under Anaesthesia classified 1503 deaths before full recovery from anaesthesia occurring between 1984 and 1990. 172 deaths were attributed to anaesthesia, including 11 in which the anaesthetic choice or management could not be criticized. In the remaining 161 an average of 1.8 errors per case were identified, the most frequent being inadequate preparation of the patient (in 72 cases), inadequate postoperative care (52 cases), the technique of anaesthesia chosen (44 cases) and overdose (43 cases). Death was most commonly attributed to anaesthesia in elderly patients (modal age group 70–79), in males (1.9:1) and was most commonly associated with abdominal and orthopaedic operations. Urgent non-emergency cases, 10% of the 1503 cases classified, constituted 26% of those deaths attributed to anaesthesia. One death attributable to anaesthesia occurred per 20,000 operations and the rate of such deaths was 0.44 per 100,000 population per annum.

A pilot study was performed in eight Australasian day surgery facilities with a purpose of identifying common trends and differences. A prospective study was designed in which information was collected on 826 patients over a two-week period. Patients were well matched for age, anaesthetic type and mean surgical time. Three facility types were identified and results were statistically corrected for any differences that ASA status, age and surgical time may have made. Patient preoperative waiting time, recovery room times, delayed discharge time and unanticipated admission rates showed favourable outcome trends for free-standing facilities compared with hospital-integrated facilities where day patients had a shared recovery with inpatients. Similar trends were seen with patient opinions of waiting times and recovery periods. In summary, this pilot study has demonstrated the impact of different facility types on efficiencies and patient satisfaction both of which have important cost implications and relevance to those involved in continuous quality improvement processes in day surgery.

A survey was conducted among 259 New Zealand specialist anaesthetists to assess attitudes and practices with regard to epidural or subarachnoid anaesthesia (ESA). Ninety-four per cent replied and virtually all of the respondents indicated that they performed ESA at some time. ESA was used by most anaesthetists for most patients undergoing major hip or knee surgery, abdomino-perineal resection, cystectomy, caesarean section or transurethral resection of the prostate. ESA was used in about half of patients undergoing abdominal aortic aneurysm repair, femoro-popliteal bypass or thoracotomy and there was marked variation between anaethetists in the frequency of using ESA for these procedures. There was broad consensus about the importance of a number of factors that might influence the decision to employ ESA; in particular that systemic sepsis and prolonged bleeding time were important contraindications and that patient preference and chronic lung disease were important indications. However respondents were equally divided as to whether they felt that recent myocardial infarction or congestive heart failure constituted indications or contraindications to ESA.

Two case reports are presented where inhaled aerosolized prostacyclin (IAP) was used to good effect as a selective pulmonary vasodilator. It was used in the treatment of a patient with severe hypoxaemia secondary to amniotic fluid embolism and for hypoxaemia secondary to the acute respiratory distress syndrome (ARDS) in a patient with acute on chronic liver failure and intra-abdominal sepsis. An apparent dose-response curve is demonstrated in the second case. A dose of IAP of 30–40 ng/kg/min produced an effect on oxygenation in the patient with liver failure equal to that seen at the maximal dose of (50 ng/kg/min). Reduction in dose below 30 ng/kg/min resulted in a deterioration in oxygenation towards baseline/pre-treatment levels. Inhaled aerosolized prostacyclin is a potent pulmonary vasodilator with little or no systemic hypotensive effect. It is simple to administer and would appear to be a viable alternative to inhaled nitric oxide.