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Biomedical subjects

N M Gibbs

Publications and source records attributed to N M Gibbs.

16 recordsLinked to original sources
PubMed1992

Postoperative changes in coagulant and anticoagulant factors following abdominal aortic surgery.

The extent and time course of changes in selected procoagulant and anticoagulant factors were investigated in 19 patients undergoing elective abdominal aortic surgery. The coagulation factors were measured preoperatively, and on days two, four, and six postoperatively. It was found that there were no significant changes outside the normal range in prothrombin time, partial thromboplastin time, or thrombin clotting time. However, there were large increases in the procoagulants, fibrinogen, factor VIII coagulant, factor VIIIRag/von Willebrand factor, and in alpha 1-antitrypsin. Over the same time there were marked decreases in the naturally occurring anticoagulants, protein C and antithrombin III, and in alpha 2-macroglobulin. These changes implied that the patients were "hypercoagulable" in the postoperative period. The maximum changes in the procoagulants occurred on either postoperative day two or day four. The maximum changes in the natural anticoagulants occurred on postoperative day two. There were no significant changes in factor V, factor X, alpha 2-antiplasmin, or platelet aggregability. The timing of the changes coincided with a period of high risk of perioperative myocardial infarction in this group of patients. Thus, it is possible that postoperative hypercoagulability contributes to the development of coronary artery thrombosis and myocardial infarction following abdominal aortic surgery.

Aged↗
PubMed1992

The effect of epidural blockade on postoperative hypercoagulability following abdominal aortic bypass surgery.

The effect of epidural blockade on postoperative hypercoagulability was assessed in patients undergoing elective abdominal aortic bypass surgery. Twenty patients were randomised to receive general anaesthesia alone, or general anaesthesia plus thoracic epidural blockade with 0.5% bupivacaine. It was found that the addition of epidural blockade did not alter the postoperative increase in plasma fibrinogen, factor VIII coagulant, or alpha 1-antitrypsin. Similarly, epidural blockade did not affect the postoperative decrease in antithrombin III. The results suggest that epidural blockade with local anaesthetic agents does not prevent the postoperative hypercoagulability response following abdominal aortic bypass surgery.

Aged↗
PubMed1991

The accuracy of Finapres noninvasive mean arterial pressure measurements in anesthetized patients.

The Finapres (FIN) is a new noninvasive blood pressure monitor that provides continuous arterial waveform display with the use of a finger cuff. The authors assessed the accuracy of FIN mean arterial pressure (MAP) measurements relative to simultaneous direct radial arterial pressures in 20 patients undergoing general anesthesia for major elective surgery. Data were collected digitally with the use of RS-232 communications over a total of 16.2 h. The data were processed into 6012 interference-free time samples, each spanning 6 s. The authors determined the difference between FIN and direct MAPs during each time sample. The authors calculated not only the bias of FIN measurements, but also the frequency, magnitude, and duration of discrepancies between simultaneous FIN and direct MAPs. The overall bias of the FIN MAP was -0.5 +/- 1.0 mmHg, which was not significantly different from zero. However, 32.3 +/- 6.2% of all MAP comparisons differed by greater than +/- 10 mmHg, and 5.0 +/- 1.1% differed by greater than +/- 20 mmHg. Moreover, there was an average of one episode every 2 patient-hours when the FIN MAP differed by greater than +/- 20 mmHg for more than 1 min. Although the MAP measured by FIN accurately reflected direct MAPs most of the time, there were occasional discrepancies of different magnitude such that clinical usefulness may be limited in patients in whom continuous accurate blood pressure measurements are essential.

Anesthesia, General↗
PubMed1991

The effect of the depth of neuromuscular blockade on the haemodynamic response to tracheal intubation.

The effect of two different doses of vecuronium on the heart rate and mean arterial pressure response to tracheal intubation was compared in 32 adult ASA class I patients. It was found that the higher dose of vecuronium (2.5 X ED95) produced greater depression of the evoked electromyogram (P less than 0.01), and provided better intubating conditions (P less than 0.01) than the lower dose of vecuronium (1 X ED95). However, the heart rate and the mean arterial pressure response to tracheal intubation was similar with both doses. The results indicate that, within the range of neuromuscular blockade commonly used to facilitate tracheal intubation, the depth of neuromuscular blockade per se does not affect the haemodynamic response to intubation.

Adult↗
PubMed1991

The onset and duration of neuromuscular blockade using combinations of atracurium and vecuronium.

The effect of atracurium-vecuronium combinations on the onset and duration of neuromuscular blockade was investigated in 30 adult patients undergoing general anaesthesia for elective surgery. The patients were randomized to receive either atracurium 0.6 mg.kg-1, vecuronium 0.1 mg.kg-1, or quarter-dose, half-dose, or full-dose combinations of the two drugs. Neuromuscular blockade was assessed by measuring the evoked electromyographic response of the abductor digiti minimi to transcutaneous stimulation of the ulnar nerve. It was found that half-dose combinations of atracurium and vecuronium did not produce a shorter onset time, but did result in a longer duration of neuromuscular blockade than full-doses of either drug alone (P less than 0.01). The quarter-dose combinations did not reduce onset time or increase duration. The full-dose combinations produced both a shorter onset time (P less than 0.01) and a longer duration (P less than 0.001). The results indicate that atracurium-vecuronium combinations are supra-additive in terms of the duration of the neuromuscular blockade produced. However, the inability of atracurium-vecuronium combinations to reduce onset time without increasing duration suggests that there is little advantage in combining the two drugs in clinical practice.

Adult↗
PubMed1991

The effect of anaesthetic agents on platelet function.

This paper reviews studies which have investigated the effect of anaesthetic agents on platelet function. The results of these studies suggest that halothane is the only agent in current use which inhibits platelet function in concentrations used clinically. Nitrous oxide appears to cause only a modest inhibition, while enflurane and isoflurane appear to have minimal or negligible effects. There is no current evidence that intravenous induction agents, opiates, or muscle relaxants affect platelet function. Reports indicate that local anaesthetic agents inhibit platelet aggregation, but only at concentrations far greater than peak plasma concentrations found during clinical use. Epidural anaesthesia may be associated with a reduction in platelet aggregation through a mechanism unrelated to direct local anaesthetic inhibition. The clinical significance of the effect of halothane on platelet function is not known. However, it is possible that halothane may affect bleeding or thrombotic complications in a similar manner to other 'anti-platelet' drugs.

Anesthetics↗
PubMed1990

Extent of mesorectal spread and involvement of lateral resection margin as prognostic factors after surgery for rectal cancer.

The extent of tumour growth beyond the muscularis propria (mesorectal spread) was measured in specimens from 167 consecutive patients with rectal cancer. The 5-year survival was significantly greater in patients with slight mesorectal spread (4 mm or less) than in those with more extensive mesorectal spread (55% [95% confidence interval 42-66%] vs 25% [13-38%]). The prognostic value for survival of mesorectal spread was independent of the presence of lymphnode metastases. There were also significant differences in survival between patients with slight and extensive mesorectal spread among patients with Dukes' stage B tumours (66% [41-82%] vs 37% [14-60%]) and those with Dukes' stage C tumours (30% [12-52%] vs 18% [6-34%]). Thus mesorectal spread of rectal cancer is an important determinant of survival, and its accurate measurement may serve to subdivide Dukes' B and C cases. In this study tumour involvement of the lateral resection margin was not a useful predictor of local recurrence, but it did correlate with poor prognosis.

Actuarial Analysis↗
PubMed1989

Management of screen detected ductal carcinoma in situ of the female breast.

Thirty eight ductal carcinomas in situ of the female breast detected during the first 7 years of screening by the Guildford Breast Screening Unit have been treated by one surgeon. Twenty-eight cases were treated conservatively and ten by mastectomy. In the group treated conservatively there have been five local recurrences: four as ductal carcinoma in situ and one as node negative microinvasive carcinoma. There were no clinical or pathological features that predicted local recurrence, which was detected only by follow-up mammography. Based on these early results, an initially conservative approach to screen detected ductal carcinoma in situ is advocated.

Aged↗
PubMed1989

The effect of neuromuscular blockade with vecuronium on hemodynamic responses to noxious stimuli in the rat.

The effect of neuromuscular blockade with vecuronium on the hemodynamic responses to a noxious stimulus was investigated in male Sprague-Dawley rats. The rats were anesthetized with either halothane (group 1, n = 10), or isoflurane (group 2, n = 10). The maximum values for heart rate and mean arterial pressure during the noxious stimulus (base-tail clamp) were measured, and the maximum changes in these values (maximum minus prestimulation) were calculated. The responses were measured at two different anesthetic concentrations (0.6 X MAC, 0.75 X MAC), before and after vecuronium 1.0 mg.kg-1 iv. It was found that neuromuscular blockade with vecuronium did not reduce any of the hemodynamic responses measured, at either anesthetic concentration, in either the halothane or the isoflurane group. However, increasing the anesthetic concentration from 0.6 X MAC to 0.75 X MAC produced statistically significant (P less than 0.01) reductions in several of the responses measured. The inability of vecuronium to reduce hemodynamic responses to noxious stimuli in this study suggests that neuromuscular blockade does not alter anesthetic depth in the rat. A knowledge of this "absence of effect" may be important for investigators who need to induce muscle relaxation in laboratory animals prior to examining the effect of anesthetic agents on hemodynamic responses to noxious stimuli. The results also question the ability of neuromuscular blockade to reduce anesthetic requirement, and support the view that neuromuscular blockade does not contribute to the anesthetic state.

Anesthesia, Inhalation↗
PubMed1978

The relationship between microcalcification and in situ carcinoma of the breast.

The relationship of microcalcification to lobulo-ductal dysplasia and non-invasive carcinoma was studied in 20 women with in situ carcinoma of the breast. All had microcalcification on the mammogram and in half there was also mammographic evidence of disruption of the breast structure. Three-quarters of the women presented with breast symptoms. Multifocal carcinoma was found in seven patients and the histology suggested that not all foci may progess to extensive duct infiltration or invasion. Calcification was found to occur both in carcinoma and in adjacent benign breast lesions and in three cases no evidence of calcification was found in the carcinoma, but was present in adjacent epitheliosis. The origin and distribution of microcalcification appears to be the same in epithelial hyperplasia, non-invasive carcinoma and invasive carcinoma and there may be a relationship between the amount of calcification and the activity of the epithelial cells. Microcalcification is not specific to breast cancer, but is a product of increased cellular activity in the lobulo-ductal complex and may be extruded into the surrounding interstitial tissue. This implies that microcalcification on the mammogram, particularly if sparse, demonstrates a high risk area of breast rather than a certainty of the presence of carcinoma.

Adult↗
PubMed1977

Undifferentiated carcinoma of the large intestine.

Eight cases of the rare undifferented carcinoma of the large intestine are described. The histological distinction between undifferentiated and poorly differentiated colonic adenocarcinoma and malignant carcinoid is discussed. It is concluded that undifferented carcinoma is a variant of adenocarcinoma which tends to grow to a large size before symptoms are produced but which nevertheless has a good prognosis when locally resectable. Five patients survived between 6 and 28 years, one is well 6 months after operation and two cases where local removal could not be achieved, died within a year.

Adenocarcinoma↗