Biomedical subjects
Publications and source records attributed to J F Hardy.
A patient is presented in whom a pulmonary artery catheter (PAC) formed a knot which was fixed in the region of the tricuspid valve chordea. The PAC was successfully and nonsurgically freed from its attachment and removed. A guide wire was introduced by the distal port of the PAC and under fluoroscopy the PAC was manipulated free and then extracted easily.
In an effort to reduce morbidity associated with transfusion of blood products, the use of antifibrinolytics to decrease bleeding and transfusions after cardiopulmonary bypass (CPB) is receiving widespread attention. The predominant haemostatic defect induced by CPB and, therefore, the mechanisms by which natural (aprotinin) or synthetic antifibrinolytics (sigma-amino-caproic acid, tranexamic acid) exert their effects have been difficult to define. Nonetheless, all three substances appear to be effective in the treatment or in the prevention of excessive bleeding associated with cardiac surgery. However, the administration of these drugs should not attempt to replace meticulous surgical and anaesthetic care. In particular, the importance of an appropriate transfusion practice cannot be overemphasized. The efficient use of these, sometimes expensive, drugs must take into account not only the initial cost, but also the short- and long-term economic consequences for the health care provider of using, or not using, a given medication. Unfortunately, the comprehensive data on which authoritative conclusions may be reached are not yet available. Pending availability of these data, the present use of antifibrinolytics at the Montreal Heart Institute is the following: (1) patients undergoing elective primary myocardial revascularization or valve surgery do not receive prophylactic antifibrinolytics; (2) patients undergoing repeat myocardial revascularization, repeat valve surgery, or primary or repeat combined procedures, receive prophylactic sigma-aminocaproic acid; (3) sigma-aminocaproic acid may be used to treat excessive chest drainage in the postoperative period; (4) the prophylactic and the therapeutic uses of low doses of aprotinin are currently under investigation.
The use of blood products in 1480 consecutive cases of adult cardiac surgical procedures over a period of 15 mth was studied retrospectively using the database of the Department of Anaesthesia of the Institut de Cardiologie de Montréal. Use of blood products was compared in patients having (1) coronary artery bypass grafting, (2) valvular surgery, (3) or a combination of 1 and 2. First operations were compared with reoperations. Overall, the use of homologous blood products was greatest in patients of Group 3, intermediate in patients of Group 2, and smallest in patients of Group 1. Reoperations were associated with an increase in intraoperative transfusion of packed red blood cells, but postoperative chest drainage was similar to first operations. When all blood products (packed red blood cells, fresh frozen plasma and platelets) were taken into consideration, patients undergoing primary CABG or valve surgery were the least exposed to homologous blood donors (five and six units transfused respectively). Repeat CABG was associated with an intermediate exposure to homologous blood products (eight units). Finally, primary and repeat combined procedures, and repeat valve surgery were associated with the greatest exposure to foreign blood products (10, 13 and 10 units respectively). The data presented in this study provide a rational basis for stratification of procedures according to the expected use of blood products, particularly in view of future studies which may be planned to examine the efficiency of blood conservation strategies.
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The purpose of the study was to determine intubating conditions after administration of either succinylcholine or vecuronium in a rapid induction sequence. Patients received either succinylcholine 1.5 mg.kg-1 (Groups I and II) after d-tubocurarine 0.05 mg.kg-1 four minutes earlier, or vecuronium (Groups III and IV) in an initial dose of 0.01 mg.kg-1 followed four minutes later by 0.1 mg.kg-1. In Groups I and III an apnoeic delay of one minute was allowed before intubation whereas in Groups II and IV the delay was 90 sec. There was no significant difference in intubating conditions between Groups I and IV. Intubating conditions in Group III (vecuronium-delay of one minute) were statistically worse than in any of the three other groups. A delay of 90 sec after succinylcholine improved intubating conditions in male patients. Considering that intubating conditions obtained after 90 sec in patients given a priming sequence with vecuronium (Group IV) were not different from those obtained 60 sec after succinylcholine (Group I), the authors conclude that vecuronium is an acceptable alternative for rapid tracheal intubation. In the doses used in this study, intubating conditions 60 sec after vecuronium were unacceptable for rapid induction of anaesthesia.
In an attempt to explain the discrepancy between the high number of patients said to be at risk of aspiration pneumonitis and the low reported incidence of this anaesthetic complication, 100 ASA physical status I-II elective surgical patients were studied. The volume of fluid present in the stomach at the time of induction of anaesthesia was correlated with gastroesophageal reflux (GER) detected by visual inspection of the pharynx and by continuous measurement of upper oesophageal pH. Mean gastric volume was 30 +/- 28 ml (range 0-210 ml). Gastric fluid volume greater than or equal to 0.4 ml.kg-1 at pH less than or equal to 2.5 was present in 46 patients. No GER was detected during induction of anaesthesia in our sample of 100 patients. Furthermore, patient age, duration of preoperative fasting, body mass index, cigarette smoking, alcohol consumption, preoperative anxiety, and a history of preoperative GER were not correlated with significant modifications of gastric volume or pH. We conclude that the low incidence of aspiration pneumonitis in elective surgical patients may be explained in part by the very low risk of GER, despite gastric fluid volumes of more than 0.4 ml.kg-1 in a high proportion of this patient population.
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In a general hospital over a period of 6 years 57 infants with congenital hypertrophic stenosis underwent a Ramstedt pylorotomy. In most cases a surgical resident-in-training performed the operation under the direct supervision of a general surgeon. There were no complications of anesthesia, no deaths and no substantial morbidity. The majority of infants left the hospital within 48 hours. The results in this series compared favourably with those reported from more specialized centres.
In an attempt to reduce the dose of local anaesthetic agent during intravenous regional anaesthesia (IVRA) of the upper limb, we have used a forearm tourniquet in 12 adult volunteers. The volume of the forearm venous system was predetermined angiographically. We performed IVRA with three solutions of lidocaine (0.25, 0.375, 0.5 per cent) administered in a volume equal to the forearm venous system. Angiographic results indicate that: a forearm tourniquet provides adequate vascular isolation; the volume of the forearm venous system can be correlated with body weight; the progression of the fluid in the venous system follows a pattern that is similar for all patients with the small veins of the distal forearm and proximal hand being filled last. With this technique, lidocaine 0.5 per cent resulted in a dose of 1.5 mg.kg-1 and provided excellent analgesia. Lower concentrations were unsatisfactory. We conclude that the use of a forearm tourniquet allows reduction of the local anaesthetic dose to a non-toxic level and thus increases the safety of IVRA.
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High concentrations (70-80 per cent) of nitrous oxide (N2O) have been shown to cause distension of gas-containing distensible structures such as the intestines and are, for this reason, avoided by some during elective abdominal operations on the GI tract. We undertook this study to determine if N2O was responsible of a measurable change in intestinal diameter or of clinical difficulty in closing the abdomen in patients undergoing elective intestinal surgery of intermediate duration. Twenty patients scheduled for elective abdominal surgery were studied. Premedication and induction were identical in all patients. Maintenance of anesthesia in Group I was with enflurane in air/oxygen, and fentanyl. Patients in Group II received enflurane in N2O/oxygen, and fentanyl. FIO2 was 0.4 in both groups and monitored neuromuscular blockade with pancuronium was kept optimal throughout the operation. The surgeon was blinded as to the random distribution of patients to either group. Girth measurements at the level of the umbilicus were recorded before induction and after surgery. The circumferences of the terminal ileum and of the transverse colon were measured at the beginning and at the end of surgery. The surgeon was asked to rate the difficulty in closing the abdomen as 0 = none, 1 = slight, 2 = moderate, 3 = severe, 4 = impossible. Data were analysed using Student's paired t test, unpaired t test and Fisher's exact test. P less than 0.05 was considered statistically significant. There was no significant difference between groups in age, sex distribution, weight and duration of surgery (approximately 90 minutes in both groups).(ABSTRACT TRUNCATED AT 250 WORDS)
Two methods used to measure the volume of gastric contents were evaluated in 24 supine anaesthetized adults. Methods compared were: (1) aspiration of stomach contents through a large, vented, multi-orificed gastric tube, and (2) indirect determination by a dye dilution method using polyethylene glycol (PEG) as the marker. The volumes determined by these methods (Vasp and Vpeg respectively) were compared to the total volume (Vtot) present in the stomach, determined by direct inspection of the gastric pouch by the surgeon at the beginning of surgery. The results show that the volume of aspirated gastric fluid, using this type of tube, is a very good estimate of the total volume of gastric residue. The PEG dilution method yields similar results. However, correlation between Vpeg and Vtot was not as close-fitting as the correlation between Vasp and Vtot. PEG dilution is more complicated, time-consuming and offers no advantage over aspiration.
Depending on the population characteristics, 12 to 80 per cent of patients undergoing elective surgery exceed the current risk criteria for aspiration pneumonitis (gastric volume greater than or equal to 0.4 ml.kg-1 and pH less than or equal to 2.5), in sharp contrast to the actual incidence of the disorder, estimated at 0.01 per cent. Improved specificity would likely result if the risk of regurgitation was also considered, in addition to the volume and pH criteria. As a first attempt to assess the risk of regurgitation under general anaesthesia, we measured the minimal gastric volume (VR) required to produce regurgitation in cats anaesthetized with ketamine. The mean was 20.8 ml.kg-1 (n = 7, range: 8-41, SD = 7.8). We conclude that the residual gastric volume needed to produce a regurgitation under general anaesthesia is at least 20 times greater than the volume required to produce pulmonary damage by intratracheal injection (0.3 ml.kg-1, assuming a pH of 2.5 or less).
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