Centile-based early warning scores derived from statistical distributions of vital signs

Aim of study

To develop an early warning score (EWS) system based on the statistical properties of the vital signs in at-risk hospitalised patients.

Materials and methods

A large dataset comprising 64,622 h of vital-sign data, acquired from 863 acutely ill in-hospital patients using bedside monitors, was used to investigate the statistical properties of the four main vital signs. Normalised histograms and cumulative distribution functions were plotted for each of the four variables. A centile-based alerting system was modelled using the aggregated database.

Results

The means and standard deviations of our population's vital signs are very similar to those published in previous studies. When compared with EWS systems based on a future outcome, the cut-off values in our system are most different for respiratory rate and systolic blood pressure. With four-hourly observations in a 12-h shift, about 1 in 8 at-risk patients would trigger our alerting system during the shift.

Conclusions

A centile-based EWS system will identify patients with abnormal vital signs regardless of their eventual outcome and might therefore be more likely to generate an alert when presented with patients with redeemable morbidity or avoidable mortality. We are about to start a stepped-wedge clinical trial gradually introducing an electronic version of our EWS system on the trauma wards in a teaching hospital.     

Periapical surgery using CAD/CAM guidance: preclinical results

Apicoectomy is a surgical procedure requiring precise planning and access to locate apices and avoid vital anatomic structures. Traditional methods limit treatment because they rely on two-dimensional radiography and corrective actions during surgery. Surgical guidance, which uses computed tomography and computer-aided design and computer-aided manufacturing processing, has been utilized in dentistry, but not in endodontics. Therefore, the aim of this study was to introduce periapical surgical guidance using computed tomography and computer-aided design and computer-aided manufacturing surgical guides and to compare apical access accuracy using guidance versus a conventional method. Results showed that distance from the apex was 0.79 mm (+/-0.33 SD) using guidance and 2.27 mm (+/-1.46 SD) using freehand drilling. An error greater than 3 mm occurred over 22% of the time freehand, yet never occurred with guidance. This in vitro study suggests that greater accuracy and consistency can be achieved during endodontic surgery with surgical guidance. Advantages also include presurgical visualization in three dimensions.     

Heart-lung interactions

PURPOSE OF REVIEW: Assessment of cardiovascular stability using ventilation-induced changes in measured physiological variables, referred to as functional hemodynamic monitoring, usually requires measurement of ventilation-induced changes in venous return. Thus, it is important to understand the determinants of these complex heart-lung interactions. RECENT FINDINGS: Several animal and human studies have recently documented that ventricular interdependence plays an important role during positive-pressure breathing, causing acute cor pulmonale. With the use of lower tidal volume ventilation in patients with acute respiratory failure, the incidence of acute cor pulmonale is decreasing proportionally. When present, however, it induces a stroke volume variation that is 180 degrees out of phase with that seen in hypovolemic states, such that left ventricular stroke volume increases during inspiration rather than decreasing as seen in hypovolemia. Further, when either tidal volume or positive end-expiratory pressure levels are varied, both stroke volume variation and pulse pressure variation are affected in a predictable manner. The greater the swing in intrathoracic pressure, the greater the change in venous return. SUMMARY: Functional hemodynamic monitoring is becoming more prevalent. For it to be used effectively, the operator needs to have a solid understanding of how ventilation induces both pulse pressure variation and stroke volume variation in that specific patient.     

Pre-operative inspiratory muscle training preserves postoperative inspiratory muscle strength following major abdominal surgery �C a randomised pilot study

INTRODUCTION

The aim of this pilot study was to assess the effect of pre-operative inspiratory muscle training (IMT) on respiratory variables in patients undergoing major abdominal surgery.

PATIENTS AND METHODS

Respiratory muscle strength (maximum inspiratory [MIP] and expiratory [MEP] mouth pressure) and pulmonary functions were measured at least 2 weeks before surgery in 80 patients awaiting major abdominal surgery. Patients were then allocated randomly to one of four groups (Group A, control; Group B, deep breathing exercises; Group C, incentive spirometry; Group D, specific IMT). Patients in groups B, C and D were asked to train twice daily, each session lasting 15 min, for at least 2 weeks up to the day before surgery. Outcome measurements were made immediately pre-operatively and postop-eratively.

RESULTS

In groups A, B and C, MIP did not increase from baseline to pre-operative assessments. In group D, MIP increased from 51.5 cmH₂O (median) pre-training to 68.5 cmH₂O (median) post-training pre-operatively (P < 0.01). Postoperatively, groups A, B and C showed a fall in MIP from baseline (P < 0.01, P < 0.01) and P = 0.06, respectively). No such significant reduction in postoperative MIP was seen in group D (P = 0.36).

CONCLUSIONS

Pre-operative specific IMT improves MIP pre-operatively and preserves it postoperatively. Further studies are required to establish if this is associated with reduced pulmonary complications.     

Hemodynamic Effects of Synchronized High-frequency Jet Ventilation Compared with Low-frequency Intermittent Positive-pressure Ventilation after Myocardial Revascularization

Background: The purpose of this prospective study was to examine the effect on cardiac performance of selective increases in airway pressure at specific points of the cardiac cycle using synchronized high-frequency jet ventilation (sync-HFJV) delivered concomitantly with each single heart beat compared with controlled mechanical ventilation in 20 hemodynamically stable, deeply sedated patients immediately after coronary artery bypass graft.

Methods: Five 30-min sequential ventilation periods were used interspersing controlled mechanical ventilation with sync-HFJV twice to control for time and sequencing effects. Sync-HFJV was applied using a driving pressure, which generated a tidal volume resulting in gas exchanges close to those obtained on controlled mechanical ventilation and associated with the maximal mixed venous oxygen saturation. Hemodynamic variables including cardiac output, mixed venous oxygen saturation and vascular pressures were recorded at the end of each ventilation period.

Results: The authors found that in 20 patients, hemodynamic changes induced by controlled mechanical ventilation and by sync-HFJV were similar. Cardiac index did not change (mean +/- SD for controlled mechanical ventilation: 2.6 +/- 0.7 l [middle dot] min-1 [middle dot] m-2; for sync-HFJV: 2.7 +/- 0.7 l [middle dot] min-1 [middle dot] m-2;P value not significant). This observation persisted after stratification according to baseline left-ventricular contractility, as estimated by ejection fraction.     

Medical students can learn the basic application, analytic, evaluative, and psychomotor skills of critical care medicine

OBJECTIVE: To determine whether fourth-year medical students can learn the basic analytic, evaluative, and psychomotor skills needed to initially manage a critically ill patient. DESIGN: Student learning was evaluated using a performance examination, the objective structured clinical examination (OSCE). Students were randomly assigned to one of two clinical scenarios before the elective. After the elective, students completed the other scenario, using a crossover design. SETTING: Five surgical intensive care units in a tertiary care university teaching hospital. PARTICIPANTS: Forty fourth-year medical students enrolled in the critical care medicine (CCM) elective. INTERVENTIONS: All students evaluated a live "simulated critically ill" patient, requested physiologic data from a nurse, ordered laboratory tests, received data in real time, and intervened as they deemed appropriate. MEASUREMENTS AND MAIN RESULTS: Student performance of specific behavioral objectives was evaluated at five stations. They were expected to a) assess airway, breathing, and circulation in appropriate sequence; b) prepare a manikin for intubation, obtain an acceptable airway on the manikin, demonstrate bag-mouth ventilation, and perform acceptable laryngoscopy and intubation; c) provide appropriate mechanical ventilator settings; d) manage hypotension; and e) request and interpret pulmonary artery data and initiate appropriate therapy. OSCEs were videotaped and reviewed by two faculty members masked to time of examination. A checklist of key behaviors was used to evaluate performance. The primary outcome measure was the difference in examination score before and after the rotation. Secondary outcomes included the difference in scores at each rotation. The mean preelective score was 57.0%+/-8.3% compared with 85.9%+/-7.4% (p<.0001) after the elective. Significant improvement was demonstrated at each station except station I. CONCLUSION: Fourth-year medical students without a CCM elective do not possess the basic cognitive and psychomotor skills necessary to initially manage critically ill patients. After an appropriate 1-month CCM elective, students' thinking and application skills required to initially manage critically ill patients improved markedly, as demonstrated by an OSCE using a live simulated "patient" and manikin.     

Practice MRI: Reducing the need for sedation and general anaesthesia in children undergoing MRI

The aim of this study was to evaluate the effectiveness of a practice magnetic resonance unit, in preparing children to undergo magnetic resonance procedures without general anaesthesia (GA) or sedation. The records of children who attended the practice MRI between February 2002 and April 2004 were retrospectively reviewed. Each record was assessed as to whether the child had passed or failed the practice MRI intervention. Those children who were considered to have passed and were proceeded to a clinical non‐GA MRI had the report of the clinical scan reviewed. If the scan had been reported as non‐diagnostic because of movement artefact it was classified as a failed scan, otherwise it was considered a pass. One hundred and thirty‐four children undertook a practice MRI (age range 4.1–16.1 years, median age 7.7 years, 47% boys) and 120/134 (90%) passed the practice session. In all, 117/120 (98%) subsequently had a clinical non‐GA MRI and 110/117 (94%) passed (median age 7.8 years, 47% boys). Preparation is a safe and effective method to reduce the need for sedation and GA in children undergoing a clinical MRI scan. It provides a positive medical experience for children, parents and staff, and results in cost savings for the hospital.