Propofol sedation after open heart surgery A clinical and pharmacokinetic study

One hundred adult patients who required mechanical ventilation after open heart surgery for coronary revascularisation were studied. All received a standard premedication and a high dose opioid anaesthetic. On arrival in the intensive care unit they were allocated randomly to receive either propofol or midazolam to maintain sedation within a predetermined range. Patients who received propofol underwent extubation of the trachea, using standard criteria, after a mean time (log-transformed) of 7.6 minutes after sedation for approximately 17 hours. The corresponding time was 125 minutes in those given midazolam. There were significantly higher morphine requirements during sedation, and higher arterial carbon dioxide tensions 30 minutes after extubation of the trachea, in patients who received midazolam. Pharmacokinetic analysis in 20 patients showed that the elimination half-life of propofol was prolonged (470 minutes) and clearance was reduced (1.14 litres/minute) compared with subjects who had not undergone cardiopulmonary bypass. The rapid clinical recovery was reflected in a rapid redistribution half-life (13.4 minutes), but this was also longer than the redistribution time of 2-4 minutes in other patients.     

Dopexamine hydrochloride does not modify hemodynamic response or tissue oxygenation or gut permeability during abdominal aortic surgery

PURPOSE: To assess the effects of intraoperative infusion of dopexamine (a DA-1 and B2 adrenoreceptor agonist) on hemodynamic function, tissue oxygen delivery and consumption, splanchnic perfusion and gut permeability following aortic cross- clamp and release. METHODS: In a randomised double blind controlled trial 24 patients scheduled for elective infrarenal abdominal aortic aneurysm repair were studied in two centres and were assigned to one of two treatment groups. Group I received a dopexamine infusion starting at 0.5 microg x kg(-1) x min(-1) increased to 2 microg x kg(-1) x min(-1) maintaining a stable heart rate; Group II received a placebo infusion titrated in the same volumes following induction of anesthesia. Measured and derived hemodynamic data, tissue oxygen delivery and extraction and gut permeability were recorded at set time points throughout the procedure. RESULTS: Dopexamine infusion (0.5 -2 microg x kg x min(-1)) was associated with enhanced hemodynamic function (MAP 65 +/- 5.5 vs 92 +/- 5.7 mm Hg, P = <0.05) only during the period of aortic cross clamping. However, during the most part of infrarenal abdominal aortic surgery, dopexamine did not reduce systemic vascular resistance index, mean arterial pressure nor oxygen extraction compared with the control group. The lactulose/ rhamnose permeation ratio was elevated above normal in both groups (0.22 and 0.29 in groups I and II respectively). CONCLUSIONS: Dopexamine infusion (0.5 -2 microg x kg(-1) x min(-1)) did not enhance hemodynamic function and tissue oxygenation values during elective infrarenal abdominal aortic aneurysm repair.     

The attitude of the general public towards preoperative assessment and risks associated with general anesthesia

PURPOSE: To survey the general public's attitude towards preoperative assessment and commonly perceived fears about general anesthesia. METHODS: A province wide telephone survey was conducted in Alberta. General and regional anesthesia were defined, a scenario involving major knee surgery was described, and participants were asked to choose between regional and general anesthesia. Respondents used a seven-point scale to rate the importance of seeing an anesthesiologist preoperatively and were questioned about the timing of such a visit. Attitudes towards commonly perceived fears associated with anesthesia were also assessed. RESULTS: A total of 1,216 people were surveyed. Over 30% of respondents felt that it was very important to see an anesthesiologist preoperatively, with a total of over 60% attributing a high degree of importance to this. Fifty percent felt that this assessment should occur on the day prior to surgery. A preference for regional or general anesthesia was not expressed in the situation. Approximately 20% of respondents were very concerned about brain damage, waking up intraoperatively and memory loss. Twelve percent were concerned about dying intraoperatively. Nine percent expressed concern about postoperative pain, with 12% reporting being concerned about nausea and vomiting. CONCLUSIONS: The general public considers anesthetic assessment on the day prior to surgery an important part of preoperative preparation. Fears of brain damage, death and intraoperative awareness associated with general anesthesia remain prevalent, suggesting that preoperative education of patients should address these concerns. The general population was less concerned about realistic fears such as nausea, vomiting and postoperative discomfort.     

Tracheal intubation of outpatients with and without muscle relaxants

PURPOSE: To compare intubating conditions and postoperative myalgias in outpatients after intubation with propofol/alfentanil compared with propofol/alfentanil/succinylcholine with and without precurarisation with d-tubocurarine. METHODS: 144 ASA I-II ambulatory patients for dental extraction under anesthesia were studied. Subjects received either 3 mg d-tubocurarine (Group II) or saline (Groups I, III) i.v. prior to induction of anesthesia with 20 microg x kg(-1) alfentanil and 2.5 mg x kg(-1) propofol followed by 1.5 mg x kg(-1) succinylcholine (II and III) or saline 0.9% (I) for muscle relaxation. The ease of airway management and the postoperative incidence, severity and distribution of muscle pains were examined. RESULTS: Intubation was successful in all patients and there were no differences in jaw mobility, ease of bag-mask ventilation, visualization of the vocal cords or cord position. Limb movement was more common during intubation in Group I (37.5%) than in Group III (8.3%) or Group II (2%), P < 0.05. At home, VAS scores for myalgia were higher in Group III than in Group I and II. Neck myalgia was more common in Group II (72%) than in Groups II (44%) and I (41%), P < 0.05. Myalgias were also more common in Group III patients (P < 0.05). CONCLUSION: Acceptable intubating conditions were achieved with propofol and alfentanil alone. Succinylcholine reduced limb movement during intubation but was associated with postoperative myalgias for up to five days. Precurarisation with tubocurarine reduced the severity of succinylcholine myalgia.     

Spinal anaesthesia in infants born prematurely

Spinal anaesthesia was used for 25 infants who were born prematurely and who subsequently required inguinal herniotomy. Hyperbaric bupivacaine 0.5% was administered in a dose of 0.3 mg/kg. Satisfactory surgical anaesthesia was achieved in 22 patients and there were no episodes of haemodynamic instability. The technique was not associated with postoperative apnoea. Spinal anaesthesia is a safe and effective alternative to general anaesthesia in these high-risk infants. However, postoperative apnoea monitoring is still essential for all infants born prematurely.     

The effects of halothane and isoflurane on hand blood flow in children. (As determined by venous occlusion plethysmography)

The effects of increasing concentrations of halothane and isoflurane were studied in two groups of twenty children aged from 2.9 to 9.8 years using the technique of water filled venous occlusion plethysmography. Halothane significantly increased hand blood flow and reduced vascular resistance only at a concentration of 0.5 MAC. However, isoflurane caused significant dose related increases in hand blood flow and reductions in hand vascular resistance at 0.5, 1.0 and 1.5 MAC. These findings suggest that in children isoflurane has a more potent vasodilator effect on the skin circulation than halothane.     

Oxygen delivery Systems–a comparison of two devices

Two low-volume, variable performance oxygen delivery systems were compared in conscious spontaneously breathing volunteers. Oropharyngeal oxygen concentrations were measured during periods of nose and mouth breathing. The systems were studied at oxygen flow rates of 2 or 4 litres/minute. The performance of both systems was similar under the test conditions but the nasal catheter is preferable in terms of cost.