PHARMACOKINETICS OF SINGLE-DOSE I.V.MORPHINE IN NORMAL VOLUNTEERS AND PATIENTS WITH END-STAGE RENAL FAILURE

Morphine 0.125 mgkg^–1 was administered i.v. to 11 normalsubjects and nine patients with chronic renal failure requiringregular haemodialysis. Plasma morphine concentrations were measuredusing high pressure liquid chromatography (HPLC). Although therewas considerable individual variation in both groups, mean plasmaconcentrations of morphine were significantly higher in thepatients with renal failure for 15 min after administration.The decay of plasma concentration fitted a three-compartmentmamillary pharmacokinetic model in all subjects. Derived values(mean $ SEM) of T^x, volume of distribution of the second compartment(V₂), total volume of distribution at steady state ( V^ss1) andtransfer rate constant from the first to the second compartment(k₁₂) were significantly different between groups. Mean valuesof terminal elimination half-life (T⁷) and total body clearancewere similar in the two groups. It was concluded that eliminationof unchanged morphine is not impaired significantly in patientswith chronic renal failure, although accumulation of morphine-3-glucuronideprobably occurs. Although the pharmacological effect of morphineis not related temporally to plasma morphine concentrations,the higher values in patients with renal failure may be implicatedin their increased sensitivity to the drug     

EFFECTS OF SUBARACHNOID SPINAL NERVE BLOCK AND ARTERIAL PCO2 ON COLON BLOOD FLOW IN THE DOG

Changes in colon blood flow in greyhounds were measured in responseto acute changes in arterial PCO₂, before and after spinal nerveblock. Colon blood flow increased significantly after spinalnerve block, irrespective of PCO₂. The findings may be of clinicalimportance in man. ^*University Department of Anaesthesia, The General Hospital,Gwendolen Road, Leicester. Department of Surgery, Royal Infirmary, Glasgow. Victoria Infirmary, Glasgow.     

HYPOXAEMIA AFTER INHALATION OF 50% NITROUS OXIDE AND OXYGEN

We have investigated, in volunteers, the effect of inhaling50% nitrous oxide in oxygen on subsequent oxygenation. Subjectsbreathed either 50% nitrous oxide in oxygen or 50% nitrogenin oxygen during hyperventilation and normal ventilation. Arterialoxygen saturation and end-expired oxygen concentrations werelower after 50% nitrous oxide in oxygen than after the othermixture with both patterns of ventilation and were lowest afterhyperventilation with 50% nitrous oxide in oxygen.     

Incidence of awareness with recall during general anaesthesia

One thousand patients who were anaesthetised between February and April 1990 at University Hospital, Nottingham were interviewed between 20 and 36 hours after their operation. Patients under 16 years of age, those who had undergone obstetric or intracranial surgery, those who were unable to communicate and patients who were discharged from hospital before the postoperative visit were not interviewed. A standard set of questions was used to determine the incidences of recall of events and dreams during the operation. These incidences were 0.2% and 0.9% respectively, considerably lower than reported in previous comparable studies.     

Quantitative effects of respired helium and oxygen mixtures on gas flow using conventional oxygen masks

A model lung system with a variable artificial constriction was used to quantify the changes in flow produced by the addition of helium to the gas mixture in the system. The tracheal concentration of helium obtained when administering 79% helium/21% oxygen to the system via conventional, disposable face masks was determined using a resuscitation dummy. The greatest proportion of the increase in flow through the orifice occurred at concentrations of helium up to 40%. A tracheal concentration of 40% helium could be obtained with all oxygen masks at fresh gas flow rates greater than 8 litres/minute. These findings will help to rationalise the administration of 79% helium/21% oxygen to patients with upper respiratory tract obstruction.     

HIGH SPINAL NERVE BLOCK FOR LARGE BOWEL ANASTOMOSIS: A retrospective study

In a retrospective study, 68 large bowel anastomoses carriedout on patients under subarachnoid or extradural spinal nerveblock with light general anaesthesia were compared with 26 anastomoseson patients receiving general anaesthesia alone. Dehiscenceoccurred in 7.4% of anastomoses performed under spinal nerveblock compared with 23.1 % in the control group. In patientsreceiving morphine, anastomotic dehiscence occurred after 15.2%of operations, compared with 5.9% in patients receiving pethidine.These differences are not statistically significant. However,the findings indicate the need for larger prospective studies. ^* Present address, University Department of Surgery, WesternInfirmary, Glasgow G11 6NT.     

THERAPEUTIC SUGGESTIONS DURING GENERAL ANAESTHESIA IN PATIENTS UNDERGOING HYSTERECTOMY

In a double-blind, randomized study, we have examined the influenceof positive therapeutic suggestions, presented to anaesthetizedpatients undergoing total abdominal hysterectomy, on postoperativemorbidity and duration of hospital stay. Seventy-five patientswere allocated randomly to be exposed to one of three tapescontaining positive therapeutic suggestions, a modified historyof the Queen's Medical Centre, or no message. We found thatneither therapeutic suggestions nor the presence of a voiceduring anaesthesia improved postoperative outcome or reducedduration of hospital stay after total abdominal hysterectomy.     

Dual dimpling in the dog

Indentation of the dura has been proposed as the cause of subatmospheric pressure in the extradural space, but has never been demonstrated directly in humans. In this study, radiographs have been produced showing dimpling of the dura by a needle tip lying in the extradural space in the dog. Pressure tracings demonstrate that advancement of the needle tip produces a progressive decrease in extradural pressure, and observations made using an image intensifier have confirmed that the pressure changes are proportional to the degree of dural indentation.