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Biomedical subjects

N M Gibbs

Publications and source records attributed to N M Gibbs.

At least 19 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

Halothane induces depressor responses to noxious stimuli in the rat.

The effect of halothane on hemodynamic responses to noxious stimuli was investigated in anesthetized male Sprague-Dawley rats. It was found that increasing the end-tidal halothane concentration from sub-MAC to supra-MAC levels was frequently associated with a reversal of the mean arterial pressure response to a noxious stimulus from a pressor response to depressor response. The depressor responses could be produced by noxious stimuli at several sites but were of greatest frequency (100%) and magnitude (up to -80 mmHg) after clamp application at the base of the tail. The depressor responses were often, but not always, accompanied by decreases in heart rate. The correlation coefficient between the changes in heart rate and the changes in mean arterial pressure caused by noxious stimuli was +0.61 (n = 9). The authors further characterized the depressor responses in an additional 18 rats. The depressor responses were not influenced by vagotomy or muscarinic cholinergic blockade and were associated with concurrent decreases in both cardiac output and systemic vascular resistance. The hemodynamic changes associated with the depressor responses were consistent with a centrally mediated withdrawal of sympathetic tone. Knowledge of this effect of halothane on the arterial blood pressure and heart rate responses to noxious stimuli may be important for correctly interpreting animal responses to noxious stimuli in the presence of general anesthetic agents, particularly because animals are frequently used to characterize both the potency and the hemodynamic effects of anesthetic agents. The presence of depressor responses also indicates that mean arterial pressure responses to noxious stimuli cannot be used as a linear index of anesthetic depth in rats anesthetized with halothane.

Anesthesia, General↗
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↗
PubMed1988

Immunohistochemical distribution of c-erbB-2 in infiltrating and in situ breast cancer.

An immunohistochemical study of c-erbB-2 expression was performed on invasive and in situ breast cancer. Strong membrane staining was seen in 16% of the infiltrating ductal carcinomas and 44% of the in situ lesions. c-erbB-2 was overexpressed in ductal rather than lobular tumours. Our results indicate that a small sub-group of breast carcinomas are associated with over-expression of this oncogene which may define an important subgroup of in situ and infiltrating ductal carcinomas.

Breast Neoplasms↗
PubMed1988

c-erbB-2 expression in benign and malignant breast disease.

An antibody, 21N, raised against a synthetic peptide from the predicted sequence of the c-erbB-2 protein has been used immunocytochemically in a retrospective study of formalin fixed paraffin embedded breast biopsies. Fourteen out of 103 infiltrating ductal carcinomas exhibited positive membrane staining. Fifty-four of these tumours had lymph node involvement of which nine contained stained cells. These were all cases where the primary tumour was positive. In this series there was no correlation between c-erbB-2 overexpression and lymph node status. In five of the positive cases studied there was an associated in situ component which was also positively stained. Ten out of 24 pure intraduct carcinomas showed membrane staining, but none of the 149 benign conditions studied, which included 22 radial scars and 13 cases of atypical ductal proliferation, demonstrated the pattern of staining associated with overexpression. It is concluded that the c-erbB-2 protein is overexpressed in a minority (approximately 14%) of infiltrating ductal carcinomas and only in cells that are cytologically malignant. Overexpression of c-erbB-2 is considered in relation to pathogenesis.

Breast Neoplasms↗
PubMed1988

Topographical and histological presentation of mammographic pathology in breast cancer.

Between 1979 and 1985 surgical resections from 680 cases of primary breast cancer were examined histologically. The patients were divided into four groups: (i) patients aged between 45 and 69 years who had been screened (n = 316); (ii) those younger than 45 who had not been screened (n = 55); (iii) those aged between 45 and 69 who had not been screened (n = 104); and (iv) those older than 69 who had not been screened (n = 205). The material was compared in terms of the association between in situ and invasive carcinoma. There was a low incidence of lobular carcinoma in situ (LCIS) in all groups and a high incidence of ductal carcinoma in situ (DCIS) which declined with age. Ninety nine group i patients had in situ carcinoma or early invasive carcinoma (less than 1 cm in diameter) compared with 19 of group iii cases. Screened patients had fewer multicentric cancers and a lower incidence of large invasive cancer compared with unscreened patients. Group ii patients had a higher incidence of whole quadrant in situ carcinoma, multiple cancer, and lymph node metastases. Group iv patients had a lower incidence of in situ cancer, and more low grade cancer than the other groups. Cases were divided into four types on the basis of this analysis.

Adult↗
PubMed1986

Clearance technique for the detection of lymph nodes in colorectal cancer.

Lymph node metastases are an important determinant of prognosis following surgery for colorectal cancer. A xylene alcohol clearance technique has been employed in Guildford to facilitate the identification of lymph nodes in the mesorectum of rectal cancer specimens. The numbers of lymph nodes and lymph node metastases were compared with seven other centres and St. Mark's Hospital, where clearance techniques were not employed in patients undergoing a randomized trial of pre-operative radiotherapy for rectal cancer. The total number of lymph nodes identified per patient in the mesorectum of patients at Guildford (mean = 23.1 +/- 1.18) was significantly higher when compared with patients at St. Mark's Hospital alone (mean = 13.1 +/- 0.86) and the seven combined "non-cleared' centres (mean = 10.5 +/- 0.6) (P less than 0.001). The number of lymph node metastases per patient was significantly higher in the Guildford series (mean = 3.21 +/- 0.58) when compared with the seven combined centres (mean = 1.9 +/- 0.3) (P less than 0.05). The numbers of lymph node metastases found in the lowest part of the specimen close to the levator ani were significantly higher in the Guildford patients (mean = 1.2 +/- 0.4) compared with St. Mark's Hospital (mean = 0.13 +/- 0.1) and the seven combined 'non-cleared' centres (mean = 0.56 +/- 0.1). This clearance technique identified not only a greater number of lymph nodes but also more metastases within those nodes, particularly in the supralevator area of the mesorectum.

Colonic Neoplasms↗
PubMed1985

Prevalence of polyps in an autopsy series from areas with varying incidence of large-bowel cancer.

The results of this multicentre autopsy study emphasize the relationship between the prevalence of adenomas and the incidence of large-bowel cancer. The highest proportion of autopsies with adenomas was observed in the area with the highest incidence of large-bowel cancer. The segmental distribution of adenomas within the colon was found to be similar to the site distribution of cancer. However, the lowest proportion of adenomas was found in the rectum, the segment in which cancer is most frequent. The latter finding suggests that either the adenoma-carcinoma sequence is a less important pathway in the pathogenesis of rectal cancer, or that more rectal than colonic adenomas become malignant. The high proportion of hyperplastic polyps in the rectum, and statistically significant regional differences following the same patterns as the incidence of rectal cancer suggest that there could be at least an indirect relationship between hyperplastic polyps and cancer of the rectum. Adenomas of both colon and rectum were more frequent in men than in women, contrary to findings with colon cancer. However, as for colon cancer, the sex ratio of adenomas changed with age, from slightly below unity in persons under 65, to above unity for those aged 65 and over. A major difficulty that emerged was the histological identification of "polyps" because of the degree of autolysis of epithelial cells in the mucous membrane, and this difficulty largely contributed to the poor consistency of histological reporting. Regular consistency surveys of histological preparations should be recommended in any type of multicentre study in which histological examination is included.

Adult↗