Comparison of commonly used clinical indicators of hypovolaemia with gastrointestinal tonometry

Objective: The gastrointestinal tonometer, which allows measurement of gastrointestinal mucosal CO₂ and subsequent derivation of gut intramucosal pH (pHi), has been demonstrated to be a sensitive predictor of outcome following major surgery. Current theory suggests that the origin of the low pH may be hypovolaemia. This study was designed to compare the temporal sequence of changes in tonometric readings with invasive blood pressure, stroke volume, heart rate, lactate and arterial blood gas measurements during progressive haemorrhage. Design: Observational healthy volunteer study. Setting: Intensive care unit at University College London Hospitals. Subjects: Six healthy, medically qualified volunteers. Interventions: After obtaining baseline measurements, the subjects were progressively bled 25 % (range = 21–31 %) of their blood volume over a period of 1 h in two approximately equal aliquots. Equilibration was allowed for 30 min following the bleed, after which further measurements were made and the blood was then retransfused over 30 min. Measurements and main results: There was no consistent change in any of the haemodynamic variables other than gastric intramucosal CO₂ : arterial CO₂ gap (PiCO₂− PaCO₂) after removal of the first aliquot of blood, although five of the six subjects also demonstrated a fall in pHi. After removal of the second aliquot of blood, PiCO₂− PaCO₂ gap and pHi continued to indicate a worsening gastric intramucosal acidosis; stroke volume, as measured by suprasternal Doppler, demonstrated a marked fall, while all other variables measured had not altered consistently or to such a degree as to elicit a clinical response or cause suspicion of a hypovolaemic state. On retransfusion, all variables returned towards baseline. Conclusions: This study demonstrates the value of tonometry as an early monitor of hypovolaemia and highlights the shortcomings of other more commonly measured clinical variables. Received: 18 January 1996 Accepted: 4 December 1996     

Risk of bleeding after dentoalveolar surgery in patients taking anticoagulants

To avoid increasing the risk of thromboembolic events, it is recommended that treatment with anticoagulants should be continued during dentoalveolar operations. We have evaluated the incidence of bleeding after dentoalveolar operations in a prospective study of 206 patients, 103 who were, and 103 who were not, taking anticoagulants. Seventy-one were taking thrombocyte aggregation inhibitors and 32 vitamin K antagonists. Patients were treated according to guidelines developed at the Academic Centre for Dentistry Amsterdam (ACTA), The Netherlands. The operations studied included surgical extraction (when the surgeon had to incise the gingiva before extraction), non-surgical extraction, apicectomy, and placement of implants. Patients were given standard postoperative care and those taking vitamin K antagonists used tranexamic acid mouthwash postoperatively.     

Improvement of blood loss volume estimation by paramedics using a pictorial nomogram: A developmental study

IntroductionTo propose and evaluate a nomogram to assist paramedics to visually estimate the external blood loss on a non-absorbent surface and to identify whether the nomogram improves visual estimation.MethodsThe study was a prospective, paired-control design (pre-training control group & post-training group), utilizing Emergency Medical Assistant (EMA) I and II trainees from the Hong Kong Fire Services Ambulance Command Training School. A nomogram (blood loss volume to area on a non-absorbent surface) was prepared to aid blood loss estimation. All participants estimated four scenarios of blood pools twice (A: 180 mL; B: 470 mL; C: 940 mL; D: 1550 mL) before and after using the nomogram. Every participant received two-minute training on how to use the nomogram correctly. The difference between the estimations and the actual volume in each scenario was calculated. The absolute percentage errors were used for direct comparison and identification of improvement between visual estimation and the use of the nomogram.ResultsSixty-one participants with an average of 3-year paramedic field experience were recruited by convenience sampling. In combining all scenarios, the median of absolute percentage error of 61 participants was 43% (95%CI 38.0–50.9%) in visual estimation, while it was 23% (95%CI 17.4–27.0%) when using the nomogram. There was a significant reduction in absolute percentage error between visual estimation and the use of the nomogram (p < 0.0001).ConclusionThe nomogram significantly improved the estimation of external blood loss volume.     

The effects of hypotension and hypovolaemia on the liberation of vasopressin during haemorrhage in the unanaesthetized monkey (Macaca Mulatta)

Summary Using unanaesthetized monkeys, experiments were performed to examine the effects of haemorrhage on the liberation of arginine vasopressin (AVP). Haemorrhages of 10%, 15% or 20% total blood volume were performed via a catheter with its tip in the abdominal vena cava. A catheter in the left internal jugular vein was used for blood sampling. Arterial blood pressure was monitored via a catheter whose tip rested in an iliac artery. The monkeys showed no signs of discomfort from this catheterisation. Blood samples for AVP assay were taken at different times from 0–90 min after the end of the haemorrhage. At the end of the experiment, blood removed was reinfused. Results show that haemorrhage resulted in liberation of AVP, but only if there was a fall in arterial blood pressure. AVP release occured more readily as the total volume of blood withdrawn increased, but the absolute rise in hormone concentration was not related to the total volume of blood withdrawn. However, comparing the area under the curve of mean arterial blood pressure with that for AVP concentration showed the two to have a significant exponential relationship. It is concluded that, as in other species, haemorrhage is a potent stimulus for AVP liberation in the monkey. However, in contrast to some other species, the fall in arterial pressure seems to be the prime stimulus rather than hypovolemia per se.     

Vasopressin and oxytocin in CSF and plasma of patients with aneurysmal subarachnoid haemorrhage

Objective

Clinicopathological studies on patients succumbing to subarachnoid haemorrhage (SAH) demonstrated hypothalamic lesions. The implication of the hypothalamic neuropeptides arginine-vasopressin (AVP) and oxytocin (OXT) has not been linked to aneurysmal SAH yet. This study investigates AVP and OXT in CSF and plasma of patients with spontaneous aneurysmal SAH and their association with outcome.

Methods

CSF and plasma samples of 12 patients with aneurysmal SAH were prospectively studied for 2 weeks. AVP and OXT were measured by radioimmunoassay. Outcome was assessed on Glasgow-Outcome-Scale. Twenty-nine patients without neuropsychiatric disturbances served as controls. Differences in neuropeptide concentration time courses were assessed by regression models. Group comparisons were performed by Kruskal–Wallis and correlations by Spearman tests.

Results

Regression of CSF levels between patients with poor and good outcome revealed significantly lower levels of AVP in patients with poor outcome (p = 0.012) while OXT showed a trend towards lower levels (p = 0.063). In plasma, no significant differences between outcome groups were found. Group comparisons between poor outcome patients and controls revealed significant differences in CSF for AVP (p = 0.001) and OXT (p = 0.015). In plasma, AVP yielded significantly different results while OXT did not. No differences were found between the good outcome group and controls. Plasma and CSF concentrations showed no significant correlation.

Conclusion

Patients with poor outcome after aneurysmal SAH have lower AVP and OXT levels in CSF than patients with good outcome while neuropeptide levels in plasma failed to reflect differences in outcome. The data indicate hypothalamic damage as an aetiologic factor for outcome after aneurysmal SAH.     

Intraparenchymal blood-fluid levels in traumatic intracerebral haematomas

Summary Blood-fluid levels within the cerebral parenchyma are observed more frequently on CT and MRI in traumatic intracerebral haematomas than in those of other aetiologies. The intraparenchymal blood-fluid interface can be formed without a fluid cavity. It is suggested that the blood-fluid levels represent layering of red blood cells within areas of contusion necrosis as well as extensive contusion oedema. The more extensive the damage to brain tissue, the more often blood-fluid levels formed. A poorer outcome can be therefore predicted when an intraparenchymal blood-fluid interface is seen.     

The iTClamp in the management of prehospital haemorrhage

IntroductionBleeding remains a leading cause of death in trauma patients. The iTClamp is a temporary wound closure device designed to control external bleeding within seconds of injury. We describe our experience using this device on 10 patients in the prehospital environment.MethodsWe have implemented the iTClamp for prehospital use through our physician-staffed helicopter emergency medical service (HEMS). Indications were massive bleeding that could not be controlled with an ordinary compressive bandage or a haemostatic bandage.ResultsTen patients were treated with the iTClamp. Seven patients had a severe head injury due to various traumas, one patient had a neck injury from a disk cutter, one patient had an open chest wound and one patient had an open femur fracture. After applying the iTClamp, bleeding was controlled in 90% of these patients (n = 9), with complete cessation reported in 60% (n = 6), partial cessation with adequate control reported in 30% (n = 3); in one patient, the bleeding could not be controlled with the iTClamp alone. It took an average of 10 s to apply the iTClamp, and the average usage satisfaction score was 7.7.ConclusionWe conclude that the iTClamp is a safe, fast and useful tool for stopping or controlling external blood loss in our series of prehospital patients. Further studies of the iTClamp are needed to determine which patients might benefit from this device.     

Emergency peripartum hysterectomy in a tertiary London hospital

Objective The objective was to review all emergency peripartum hysterectomies performed at a tertiary hospital in London, UK, and to identify the risk factors for emergency peripartum hysterectomy.Method A retrospective case control study. The cases consisted of all women who had emergency peripartum hysterectomy between 1 January 1993 and 31 December 2003. Controls were women who delivered immediately before and after the indexed case. Demographic data, medical and surgical histories, pregnancy, intrapartum and postpartum data were collected. Differences between cases and controls were compared with ², Fisher exact and Student t tests. Multiple logistic regression analysis was performed to identify independent risk factors for emergency peripartum hysterectomy.Results There were 15 cases of emergency peripartum hysterectomy in 31,079 deliveries, giving a rate of 0.48 per 1,000. Women who had emergency peripartum hysterectomy were significantly older (mean age 37 years vs. 29 years, P<0.001) and multiparous (P=0.02). More of the cases had a history of uterine surgery (67 vs. 30%, P=0.01), placenta praevia (60 vs. 3%, P<0.0001) and were delivered by caesarean section (86.7 vs. 30%, P=0.003). Eighty percent of the hysterectomies were performed in the daytime and all were done by consultants. Haemorrhage due to placenta praevia was the main indication for emergency peripartum hysterectomy (47%). Independent risk factors for emergency peripartum hysterectomy were older age (odds ratios [OR] 1.2, 95% confidence interval [95% CI] 1.2–1.6), multiparity (OR 2.6, 95% CI 1.3–10.2), history of previous caesarean section (OR 13.5, 95% CI 2.7–65.4), caesarean delivery in index pregnancy (OR 11.6, 95% CI 2.1–68.6) and caesarean delivery in index pregnancy for placenta praevia (OR 18, 95% CI 3.6–69).Conclusion Caesarean deliveries, especially repeat caesareans in women with placenta praevia, significantly increase the risk of emergency peripartum hysterectomy.