The effect of acute hypercapnia on skeletal muscle contractility and relaxation rate was investigated. The contractile force of fresh and fatigued quadriceps femoris (QF) and adductor pollicis (AP) was studied in normal humans by use of electrical stimulation. Maximum relaxation rate from stimulated contractions was measured for both muscles. Acute hypercapnia led to a rapid substantial reduction of contraction force. The respiratory acidosis after 9% CO2 was breathed for 20 min [mean venous blood pH 7.26 and end-tidal PCO2 (PETCO2) 65.1 Torr] reduced 20- and 100-Hz stimulated contractions of QF to 72.8 +/- 4.4 and 80.0 +/- 5.1% of control values, respectively. After 8 and 9% CO2 were breathed for 12 min, AP forces at 20- and 50-Hz stimulation were also reduced. Twitch tension of AP was reduced by a mean of 25.5% when subjects breathed 9% CO2 for 12 min [mean arterialized venous blood pH (pHav) 7.25 and PETCO2 66 Torr]. Over the range of 5% (pHav 7.38 and PETCO2 47 Torr) to 9% CO2, there was a linear relationship between twitch tension loss and pHav, arterialized venous blood PCO2, and PETCO2. Acute respiratory acidosis (mean PETCO2 61 Torr) increased the severity of low-frequency fatigue after intermittent voluntary contractions of AP. At 20 min of recovery, twitch tension was 63.2 +/- 13.4 and 46.8 +/- 16.4% of control value after exercise breathing air and 8% CO2, respectively. Acute hypercapnia (mean PETCO2 65.1 and 60.5 Torr) did not alter the maximum relaxation rate from tetanic contractions of fresh QF and from twitch tensions of AP.

SummaryAcute renal failure is a frequent complication of critical illness and optimal preventive therapy remains elusive. There is increasing evidence from animal models and some human studies that adenosine receptor antagonism by aminophylline may reduce the severity of renal impairment caused by a variety of aetiologies. We studied the renal effects of intravenous aminophylline in an unblinded, within-patient study of 20 patients admitted to a general intensive care unit following major surgery. We demonstrated that there were no adverse cardiovascular complications related to aminophylline therapy. Renal sodium and osmolar clearance increased with a non-significant trend towards increased diuresis during treatment. Creatinine clearance, however, was unchanged but the study was not designed and did not have the power to test whether aminophylline increased renal blood flow or glomerular filtration rate. We suggest the renal actions of aminophylline in critical illness merit further investigation. Acute renal failure is a frequent complication of critical illness, major surgery and in particular sepsis. Renal replacement therapy is associated with prolongation of intensive care and increased mortality. Factors that increase the risk of renal impairment include pre-existing renal impairment, insulin-and non-insulin-dependent diabetes, hypertension, atherosclerosis, particularly renal arterial disease, jaundice and increasing age [1].The pathophysiology of acute renal failure is not fully understood and hence optimum therapies for prevention of acute renal failure in patients at risk remain elusive. Animal-based research has suggested that adenosineinduced renal vasoconstriction may have an important role in the pathophysiology of acute renal failure and that adenosine receptor antagonists are protective.In major abdominal surgery and critical illness where ischaemic renal impairment may result, we hypothesised that theophylline, an adenosine A1 and A2 receptor antagonist, may have renal protective action. This was a study to investigate the renal actions of theophylline following major surgery. Methods Study designThe trial was an open, within-patient controlled study of 20 consecutive patients fulfilling the admission criteria. Patients were recruited at The Bristol Royal Infirmary general intensive care unit. The study had local ethics committee approval. Informed consent was obtained if possible, or assent was obtained from a near relative of those patients unable to give consent. Patients and methodsEligible patients were over 18 years of age and had undergone major abdominal surgery requiring admission to the ICU for postoperative management. Patients were haemodynamically stable, defined as in sinus rhythm with a pulse less than 120 beat.min 21 , systolic arterial blood pressure . 100 mmHg without the use of inotropic medication, central venous blood pressure . 8 mmHg and less than 20% variation in these parameters for 3 h before the start of the study. Patients had not received diuretics or dopamine for 6...

SummaryInadvertent cross-connection of epidural local anaesthetic delivery systems with intravenous lines can cause significant morbidity and even death. Inadvertent intrathecal injection of toxic intravenous drugs has already led to many deaths. If epidural and spinal systems had the standard Luer lock connection reversed the problem would be prevented. The practical implications of this idea are explored. Patient safety would be enhanced if this system were adopted.

of 80 to 90 1 min-' through a mixing box to which argon (Ar, 250 ml min-') was added as a tracer for measurement of flow. The fractional differences between oxygen and carbon dioxide in air and in the outflow from the chamber, measured at six second intervals, were multiplied by flow through the system to produce Vo2, VC02, and RQ (Vco2/Vo2). The resolution, tested by methanol combustion, was 8 ml min-1 for Vo2 and 6 ml min-1 for Vco2.Patients' medication was unaltered; all subjects had at least 30 minutes' rest within the chamber before the study started and listened to music throughout the 20 minutes' continuous gas exchange measurement (200 data points) that followed. DATA ANALYSIS Gas analysis was corrected for instrument drift and methanol combustion tests and converted to STPD. The mean and SD for two consecutive 10 minute periods were calculated, and the lower of the two subsequently included in the analysis. Vo2 values were standardised for body surface area (BSA) and calculated as follows9: Log BSA = log weight x 0 425 + log height x 0 725 + 1-8564. Resting energy expenditure (kJ/day) was compared with predicted values'0 on the basis of an oxygen equivalent of 4-83 kJ/ml. Differences between groups were analysed by means of the Wilcoxon signed rank test (p < 0 05). ResultsThere were more men in the patient group, but there were no significant differences in terms of 388 on 12 May 2018 by guest. Protected by copyright.

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