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Biomedical subjects

A R Manara

Publications and source records attributed to A R Manara.

At least 37 records · Page 2Linked to original sources
PubMed1994

Experience with percutaneous tracheostomy in intensive care: the technique of choice?

The technique of percutaneous tracheostomy is described, the experience of 77 such procedures in a single intensive care unit over 2 years is reported, and the literature reviewed. Percutaneous tracheostomy is a safe, effective, simple and rapid technique for intubated patients receiving intensive care. It can be carried out by non-surgeons and has several advantages over conventional tracheostomy in these patients. It may in the future prove to be the technique of choice for elective tracheostomy in other groups of patients, including those undergoing faciomaxillary procedures.

Adolescent↗
PubMed1994

Near-infrared spectroscopy in adults: effects of extracranial ischaemia and intracranial hypoxia on estimation of cerebral oxygenation.

We have studied the effects of extracranial ischaemia and intracranial hypoxia on measurement of cerebral oxygenation using near-infrared, reflectance-mode, cerebral oximetry (Invos 3100 cerebral oximeter) in healthy adult subjects. Under stable systemic conditions, scalp ischaemia induced by a pneumatic tourniquet caused an apparent reduction in mean regional cerebral oxygenation (rSO2) from mean 72 (SD 6)% to 59 (7)% (n = 8, P < 0.001). rSO2 returned to control values within 1 min of release of the tourniquet. Local scalp ischaemia induced by rapid frontalis muscle exercise caused a significant reduction (4.5 (2)% in rSO2 (n = 12, P < 0.001). The effect of systemic hypoxia on rSO2 was examined during controlled scalp ischaemia. A decrease in mean SpO2 from 98 (2)% to 66 (6)% was associated with a decrease in mean rSO2 from 57 (4)% to 41 (6)%. There was a significant correlation between the percentage reduction in rSO2 and SpO2 during hypoxia (r = 0.81, P < 0.001). We conclude that the Invos cerebral oximeter was capable of detecting tissue hypoxia deep to the scalp under carefully controlled conditions but that it also was affected significantly by changes in extracranial blood flow and oxygenation which may affect its reliability in clinical practice. Further work is necessary to define those situations in which cerebral oximetric monitoring is useful and valid.

Adult↗
PubMed1993

Morphine elimination and hepatic blood flow--a study in patients with portal hypertension.

To investigate the influence of changes in portal venous blood flow on the clearance of morphine, the elimination of a single intravenous dose of morphine sulphate was studied in twelve patients with periportal fibrosis undergoing distal splenorenal shunt for portal hypertension. All patients had almost normal preoperative liver function. Six patients (Group A) received morphine after induction of anesthesia but before surgery; a further six patients (Group B) received morphine after completion of the splenorenal shunt and removal of all vascular clamps. Blood was sampled for 24 hours after morphine administration and analysed for plasma morphine concentration using high performance liquid chromatography. The maximum concentration of morphine was significantly greater in those patients in Group B who received morphine after the shunt (P < .002). Clearance of morphine during the operation was also significantly reduced in these patients compared with the initial clearance (before release of the clamps) in Group A (P < .004). As a consequence of these changes the AUC was greater in this group (P < 0.004). However, there were no differences with the elimination rates after surgery had finished. The results suggest that in individuals with normal liver function, the clearance of morphine is dependent on hepatic blood flow.

Adult↗
PubMed1991

Metoclopramide and renal vascular resistance.

We have studied the effect of i.v. metoclopramide on renal vascular resistance in nine healthy volunteers. Peak systolic and end-diastolic frequencies were measured using duplex Doppler ultrasound of a renal interlobar artery, before and after the administration of i.v. metoclopramide 10 mg, and the resistance index derived. There was no significant change in mean arterial pressure or resistance index following metoclopramide.

Adult↗
PubMed1991

Total i.v. anaesthesia with propofol and alfentanil for coronary artery bypass grafting.

The haemodynamic effects of total i.v. anaesthesia with a combination of propofol and alfentanil infusions were studied in eight patients with good left ventricular function undergoing coronary artery bypass surgery. Haemodynamic indices were measured before anaesthesia and at specified intervals before cardiopulmonary bypass. The technique resulted in haemodynamic changes comparable to those reported with opioid-based anaesthesia for coronary artery surgery, and has potential advantages.

Alfentanil↗
PubMed1990

Analgesic efficacy of perioperative buccal morphine.

We have studied the effect of regular perioperative administration of buccal morphine sulphate on postoperative analgesic consumption in female patients undergoing lower abdominal surgical procedures. Ten matched pairs of women were allocated randomly to receive either placebo or buccal morphine before operation and at 12-h intervals up to 44 h after operation. Pain was assessed using a visual analogue scale and taste assessed using evaluation forms. Postoperative analgesic requirements were compared using a patient-controlled analgesia system which was set to deliver bolus doses of pethidine without a background infusion. There was no significant difference in pain scores between the two groups. Compared with placebo, buccal morphine did not reduce significantly postoperative pethidine consumption. All patients receiving buccal morphine reported a taste which reduced its acceptability.

Administration, Buccal↗
PubMed1989

Pharmacokinetics of morphine following administration by the buccal route.

The pharmacokinetics of morphine administered via the buccal route as a controlled release formulation were assessed after the administration of three different doses and found to be linear in the dose range 10-30 mg. The plasma concentrations of morphine-3-glucuronide and morphine-6-glucuronide demonstrated considerable inter-subject variation and conclusions could not be drawn regarding their pharmacokinetics. These large differences may reflect not only variability in buccal absorption, but may have resulted from the preparation dissolving in saliva, followed by absorption from the gastrointestinal tract.

Absorption↗
PubMed1989

Sedation during spinal anaesthesia: a case for the routine administration of oxygen.

We have studied the effect of sedation with midazolam on arterial oxygen saturation during spinal anaesthesia in two groups of patients: one group received supplementary oxygen, the other group breathed room air. A significant reduction in oxygen saturation was observed in patients not receiving supplementary oxygen; six of 15 patients in this group developed hypoxaemia or severe hypoxaemia which was corrected immediately by administration of oxygen. There were no episodes of hypoxaemia in any patient in the group receiving supplementary oxygen. It is concluded that oxygen should be administered routinely to patients receiving sedatives during spinal anaesthesia.

Aged↗
PubMed1989

The pneuPAC ventilator with new patient valve and air compressors.

The pneuPAC Model 2-R pneumatic logic ventilator with a new air entrainment valve that offers the option of an FIO2 of 1.0 or 0.45 is described. Its robustness, portability, variable FIO2, choice of positive end expiratory pressure and pressure relief valves make it versatile and suitable for transporting critically ill patients, as well as for resuscitation use when adverse conditions may be encountered. Two new medical air compressors, one mains driven and the other battery powered, designed for use with the ventilator, are also described. The function of the ventilator with the new valve was assessed using a piped gas supply and then reassessed when powered by the compressors.

Equipment Design↗
PubMed1989

Extra-hepatic metabolism of midazolam.

Six patients received 10 mg of midazolam intravenously during the anhepatic period of liver transplantation. Arterial blood was sampled during this time and for a similar period following revascularisation. The plasma was analysed using gas chromatography and electron capture detection (GC-ECD) for midazolam alpha-hydroxymidazolam and alpha-hydroxymidazolam glucuronide. Five of the six patients had small but significant concentrations of metabolites detected during the anhepatic period, demonstrating the presence of extra-hepatic sites of metabolism for this drug. The remaining patient had plasma concentrations of metabolites below the lower limit of detection (2 micrograms l-1). This may represent a pharmacogenetic abnormality or a temporary failure of midazolam metabolism secondary to the patients illness affecting the extra-hepatic sites of metabolism.

Adult↗
PubMed1988

The effect of metoclopramide on the absorption of oral controlled release morphine.

The pharmacokinetics of oral controlled release morphine and metoclopramide were investigated in 20 patients in a double-blind, randomly allocated study. The concurrent administration of metoclopramide and oral controlled release morphine led to a faster onset and increased level of sedation compared with the administration of oral controlled release morphine alone. Whilst the increased sedation may be advantageous in anaesthetic practice, it may be a potential problem in patients starting longer term therapy with these drugs.

Administration, Oral↗