Oxygen concentrators: a primary oxygen supply source.

PURPOSE: Efforts to harmonize the standards of the CSA and the ISO, as they relate to compressed medical gas supply and piping, prompted us to review ten years experience with oxygen concentrators (OCs) in Canada used as a primary hospital oxygen supply. The goals of this study were; 1) To document the number of Canadian OC Hospital sites, 2) to define what impact these units have had on medical practice and patient care, and 3) to explore trends in oxygen costing and utilization at the study sites. METHODS: Following a four part mail survey and telephone follow up, site surveys were conducted for all hospitals utilizing an OC. Installation and service records, operating costs, amortization detail, leasing records as well as patient safety were all detailed. RESULTS: Forty eight of 52 Canadian hospitals utilizing an OC participated. Clinical activity at the surveyed sites of 1996 included 30,642 surgical operations, 9,415 intensive care bed days and 364,529 emergency room visits. The cumulative survey represents 1,026,819 hr of OC operation. During a 24 hr day, OCs operate 55 +/- 3% of the time. Financial analysis was validated at 43 of the 48 hospital sites. During the study the unit cost of oxygen was reduced by 62% (P <.0001). An annual increase in oxygen consumption of 11.5 +/- 2% was documented (P <.0001). No patient care critical incidents related to OCs were reported. CONCLUSION: An OC installation which is CAN/CSA Z305.6-M92 compliant provides a safe, reliable, cost efficient primary hospital source of oxygen.

Do different heparin brands influence activated clotting times?

A change in brand suppliers of heparin at our institution resulted in a number of anecdotal reports of possible differences in potency. Both products are marketed as heparin sodium extracted from porcine intestinal mucosa. Heparin Leo is 1000 international units (British Pharmacopeia) per ml. while Hepalean is 10,000 United States Pharmacopeia (U.S.P) units per ml. Perfusion records were retrospectively reviewed for one month periods when Heparin Leo (n = 52) or Hepalean (n = 61) were used to provide anticoagulation therapy for cardiopulmonary bypass. Heparin Leo was found to be less clinically potent than Hepalean. While increasing the initial loading dose of Heparin Leo by 5% (378 vs 398 units/kg-1), the initial post load activated clotting time (ACT) was 17% lower (556 vs 666 seconds). Heparin units required per kilogram per minute of cardiopulmonary bypass were 23% higher for Heparin Leo. Additionally 8 of 52 Heparin Leo patients did not achieve an initial post load ACT of greater than 400 secs while this occurred in 2 of 61 patients treated with Hepalean. These results were statistically significant. British Pharmacopeia and United States Pharmacopeia heparin reference standards differences are insufficient to explain the discrepancies observed in this study.

The operating room--perceptions of a change in working environment.

The questionnaire surveyed OR staff on themes such as design, security, and workload. Surgical nurses had greater expectations for their roles and functions in the new facility. Levels of physical comfort improved; however, mood was not affected positively.

The upgrading and replacement of anaesthetic equipment: a provincial approach.

A formal on-site survey of all anaesthetizing locations in the Province of Manitoba was initiated in the Spring of 1988. Serious deficiencies of anaesthetic equipment previously noted on random survey were confirmed. Recognizing a need for improved standards for delivery of anaesthetic services through safe, functional anaesthetic equipment, the province undertook to fund the upgrading of all anaesthetic gas delivery systems under its jurisdiction. Sixty-six hospitals were surveyed for a total of 203 anaesthetic machines (111 urban, 92 rural). One hundred and sixty-seven machines had been used at least once in the previous year. After careful assessment 92 machines were replaced, 66 machines were upgraded and 45 machines were deleted from further service. Although the maintenance and upgrading of medical equipment is the individual health care facility's responsibility, substantial benefit was recognized by a provincial approach. The authors recommend a similar approach for other Canadian provinces.

Fentanyl oxygen anaesthesia for abdominal aortic surgery.

Patients who present for abdominal aortic surgery often have significant atherosclerotic disease which may involve the coronary arteries. Haemodynamic responses occurring during fentanyl (100 micrograms X kg-1) oxygen anaesthesia for abdominal aortic surgery were studied in 16 patients. Anaesthesia was induced with fentanyl 100 micrograms X kg-1 with no supplemental doses and metocurine-pancuronium mixture (4:1). In 13 of 16 patients hyperdynamic circulatory responses to surgical stimuli required treatment prior to aortic cross-clamping. Interventions instituted were sodium nitroprusside or nitroglycerin (n = 13), propranolol (n = 4), and diazepam (n = 4). The serum fentanyl concentration at time of response to surgical stimulus was 18.5 +/- 5.6 ng X ml-1 (range 7-27 ng X ml-1; time from induction 71 +/- 49 min, n = 9). Eleven of the 16 patients required treatment for postoperative hypertension. Five of the 16 patients developed myocardial ischaemia, defined as ST segment depression greater than 0.1 mV, at some time during the operative procedure. Unsupplemented fentanyl anaesthesia (100 micrograms X kg-1) was unable to maintain a hypodynamic circulation in patients having abdominal aortic operations.

Pharmacokinetics of fentanyl in patients undergoing abdominal aortic surgery.

The authors determined the pharmacokinetics of fentanyl 100 micrograms X kg-1 iv in patients undergoing elective abdominal aortic surgery. The mean (+/- SD) age of the ten patients was 67.2 +/- 8.7 yr; their mean weight was 78.5 +/- 13.7 kg. Seven patients had aortic aneurysm repair, and the other three patients had aortobifemoral grafts. Serum fentanyl concentrations were determined from samples drawn at increasing intervals over a 24-h period. A three-compartment pharmacokinetic model was fit to the concentration versus time data. Total drug clearance was 9.8 +/- 1.8 ml X min-1 X kg-1. The volume of distribution at steady-state (Vdss) was 5.4 +/- 1.9 X 1 kg-1. Elimination half-time was 8.7 +/- 2.5 h. There were no significant correlations between these pharmacokinetic parameters and patient's age, duration of aortic cross-clamping, duration of surgery, intraoperative blood loss, or volume of iv fluids given intraoperatively. In healthy volunteers or patients undergoing general surgery, other investigators report mean elimination half-times for fentanyl ranging from 1.7 to 4.4 h. The prolonged elimination half-time in patients having abdominal aortic surgery has important clinical implications. In particular, recovery from large doses will take much longer than would have been anticipated from previously published fentanyl pharmacokinetic data.

The antiarrhythmic effects of verapamil and propranolol in aminophylline toxic dogs.

The antiarrhythmic effects of the calcium blocker verapamil and the beta adrenoreceptor blocker propranolol were examined in aminophylline toxic dogs. Eighteen dogs were intubated and ventilated after induction of anaesthesia (pentobarbitone 30 mg/kg and paccuronium 0.1 mg/kg). All animals were rendered toxic by aminophylline infusion; an initial dose of 50 mg/kg over five minutes with subsequent doses of 10 mg/kg over 30 seconds. Twenty minutes after each aminophylline infusion, the dog was challenged with phenylephrine (10 to 20 micrograms/kg). This resulted in short duration hypertension and reproducible emergence of ventricular arrhythmias. The dogs were divided into three groups of six animals each. Group I (control) received no antiarrhythmics whereas Group II received verapamil 0.2 mg/kg and Group III received propranolol 0.1 mg/kg for the treatment of persistent ventricular arrhythmias. Both verapamil and propranolol exerted an antiarrhythmic effect in aminophylline induced ventricular arrhythmias. The efficacy of verapamil was independent of the accompanying reduction in blood pressure and systemic vascular resistance as subsequent phenylephrine induced hypertension could not reinstitute these arrhythmias. Propranolol appeared less effective since it did not completely suppress the arrhythmias in three dogs and could not prevent emergence of PVC's in four following repeat phenylephrine challenge. Further development of this animal model may be useful for the better understanding of ventricular arrhythmias.

Appraisal of pediatric cardiopulmonary resuscitation.

Sixty-six patients more than 30 days and less thant 16 years of age suffering an unexpected cardiac arrest in an 18-month period were included in a study of resuscitative measures in children. Six children survived to be discharged from hospital. Respiratory disease accounted for most (29%) of the cardiac arrests, but it also had the most favourable prognosis, 21% of the 19 patients surviving. None of the patients survived whose cardiac arrest was secondary to sepsis or trauma, even when the resuscitative efforts were initially successful. Only 1 of the 41 patients who had a cardiac arrest outside of hospital survived, and only 1 of the 34 patients who presented with asystole survived, and then with considerable damage to the central nervous system. The interval between cardiac arrest and application of basic life support was substantially shorter among the survivors. Also, most of the survivors did not present with asystole. The results of this study suggest that survival among resuscitated children is no better than that among adults but can be improved with early recognition and monitoring of children at risk. earlier application of basic and advanced life support, improved education of medical and lay personnel, and further research into pediatric resuscitative techniques.

Fetal monitoring during maternal cardiac surgery with cardiopulmonary bypass.

Fetal cardiac activity was monitored with an external ultrasound transducer in two patients with clinical class III heart disease due to severe mitral stenosis complicated by pulmonary hypertension, undergoing open heart surgery with cardiopulmonary bypass in the 2nd trimester of pregnancy. Fetal distress was detected in one patient, who had mitral valvuloplasty, and was corrected by increasing the rate of blood flow, and the other patient had a mitral valve replacement but no fetal distress was noted. The postoperative course of both mothers and fetuses was uneventful.