A prospective evaluation of pharmacokinetic model controlled infusion of propofol in paediatric patients

We have tested a published algorithm for pharmaco-kinetic modelcontrolled infusion of propofol to supplement 67% nitrous oxidefor general anaesthesia in Chinese children aged 4–10yr. Initially we studied 10 children undergoing minor procedureswith spontaneous ventilation; mean duration of surgery was 38min and mean propofol infusion rate 497 µg kg^–1min^–1. The precision of the model was 24.8% and bias –18.5%.The model was revised using an iterative linear least squaresregression procedure and the revised model tested prospectivelyin another 20 children. The precision of the revised model was21.5% (range in individuals 8.4–43.1%) and bias –0.1%(range –30 to 42%). Mean propofol infusion rate requiredto maintain anaesthesia was 474 µg kg^–1 min^–1(range 125–737 µg kg^–1 min^–1). The meanblood concentration required for satisfactory anaesthesia was6.6 µg ml^–1 (range 3–11 µg ml^–1)and the mean blood concentration at the time of waking, whichoccurred 40 min after switching off the infusion, 0.86 µgml^–1 (range 0.40–1.45 µg ml^–1). Ourpatient population required different pharmacokinetic variablesfrom those in the previous study. Recovery was slow becauseof the high infusion rates required to maintain satisfactoryanaesthesia and large difference between the blood concentrationrequired for anaesthesia and that at which waking occurred.(Br. J. Anaesth. 1994; 72: 302–306)     

Recovery after propofol infusion anaesthesia in children: comparision with propofol, thiopentone or halothane induction followed by halothane maintenance

We have compared the recovery profiles of 163 healthy Chinesechildren after general anaesthesia for minor surgical procedures.Patients were allocated randomly to receive one of four anaesthetictechniques: propofol infusion for induction and maintenanceusing a pharmacokinetic model-controlled syringe pump set initiallyat a target concentration of 8 µg ml^–1 and thenadjusted according to clinical requirements; propofol 2.5–3.5mg kg^–1, thiopentone 4–5 mg kg^–1 or 2–3%halothane for induction of anaesthesia followed by 1–2% halothane for maintenance of anaesthesia. All oatients breatheda mixture of 70% nitrous oxide in oxygen through a laryngealmask airway and received an appropriate regional anaestheticblock. Recovery was assessed using the time to achieve fullSteward score, open eyes on command, orientation and the timerequired to complete a simple ouzzle. Recovery was slowest withthe propofol infusion (mean 39.8 (SO 12.9) min when eyes openedon command). The recovery times were significantly shorter withthe three other techniques (propofol bolus 21.9 (9.9) min, thiopentone23.4 (11.3) min, halothane 20.1 (8.9) min), and the choice amongthese three methods had no significant influence on the recoveryprofile. (Br. J. Anaesth. 1994; 72: 554–558) ^*Present address: Department of Anaesthesia,Addenbrooke's Hospital,HillsRoad,Cambridge.     

Mycotic aneurysms of the aorta: radiologic features

Four patients with a total of six mycotic aneurysms of the aorta were examined with computed tomography (CT) after intravenous contrast material enhancement, and with abdominal or thoracic aortography. In the three patients with mycotic aneurysms involving the abdominal aorta, CT scans showed a vascular paraaortic structure without calcified walls adjacent to a nondilated aorta, and a large non-contrast-enhanced retroperitoneal mass representing inflammatory tissue and blood from a contained aortic rupture. A CT scan of one aneurysm of the thoracic aorta demonstrated an enhanced saccular mass originating from the aorta without paraspinal component. In three of four patients, the CT findings were corroborated by aortographic evidence of an eccentric aneurysmal sac in an atypical location for atheromatous disease. In four patients with clinical manifestations suggesting mycotic aneurysm of the aorta, a combination of CT and angiographic imaging provided accurate diagnostic information for planning adequate and early surgical treatment.     

Predictors of Positive Head-Up Tilt Test in Patients with Suspected Neurocardiogenic Syncope or Presyncope

OH, J.H., et al .: Predictors of Positive Head-Up Tilt Test in Patients with Suspected Neurocardiogenic Syncope or Presyncope. Neurocardiogenic syncope is the most common cause of syncope in patients who present in outpatient clinics. Head-up tilt test (HUT) has been widely used to diagnose neurocardiogenic syncope. However, the HUT does not always produce a positive response in patients with suspected neurocardiogenic syncope. The aim of the present study was to assess the clinical history and characteristics of patients with suspected neurocardiogenic syncope or presyncope who undertook HUT, and to identify prognostic factors of a positive HUT response. During the first phase of HUT, patients were tilted to a 70-degree angle for 30 minutes. If the first phase produced a negative response, the second phase was subsequently performed involving intravenous isoproterenol administration. Of 711 patients, 423 (59.5%) patients showed a positive HUT response. In contrast to previous studies, this study showed that the vasodepressive type (76.6%) was the most common pattern of positive response, and that the rate of positive response during the first phase was low (7.1%). By multivariate analysis, the occurrence of junctional rhythm was found to be a predictor of an impending positive response in HUT   (P < 0.001)   . The shorter time interval between the last episode and HUT was also a predictor of positive response   (P = 0.0015)   . Younger age   (P = 0.0003)   and a history of physical injury during a syncopal episode   (P = 0.019)   were found to be associated with a positive response in the first phase of HUT. (PACE 2003; 26[Pt. I]:593–598)     

Anaesthesia for bullectomy

A patient with a single large bulla occupying 50% of the right hemithorax was anaesthetised successfully with a combination of techniques not previously described. The technique consisted of extradural analgesia and intravenous infusion of propofol, while ventilation was maintained with high frequency jet ventilation through a single lumen tracheal tube. The advantages of this technique are a reduced risk of barotrauma, good operating conditions and good analgesia.     

Parathyroid variants: US evaluation

High-resolution (10-MHz) ultrasonography was performed in 181 patients with primary or secondary hyperparathyroidism during a 4-year period and evaluated retrospectively. Thirty-seven unusual-appearing parathyroid tumors were found among 235 parathyroid glands identified as abnormal. There was pathologic correlation in 36. The typical appearance of parathyroid adenoma was that of an oval hypoechoic or anechoic lesion in the neck, aligned in a craniocaudal direction and often posterior to the thyroid. Morphologic variations from the norm included giant size (n = 11) (4.6%), cystic changes in a solid tumor (n = 9) (3.8%), calcified glands (n = 6[in three patients]) (2.5%), a multilobulated configuration (n = 5) (2.1%), an inhomogeneous pattern (n = 5) (2.1%), and a parathyroid cyst (n = 1) (0.4%). Recognizing the abnormal parathyroid variants can increase the diagnostic accuracy of sonographic examination.