Hamilton, MA; (2012) Development of a standardised forearm exercise model to predict surgical outcome. Doctoral thesis , UCL (University College London).

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Abstract

The prediction and measurement of surgical outcome is difficult. Current methods of perioperative risk prediction do not perform particularly well on an individual basis with guidelines suggesting a stepwise approach to perioperative risk assessment. Part of this stepwise approach is an assessment of functional capacity. Cardiopulmonary exercise testing has a body of evidence to support its use as a measurement of functional capacity and predictor of perioperative risk. In addition grip strength as assessed by handgrip dynamometry has been shown to be predictive of surgical outcome. This thesis examines the development and testing of a standardised forearm handgrip exercise model to predict mortality and morbidity in orthopaedic surgical patients. This thesis investigates the development of two standardised forearm handgrip exercise models, one using an intermittent (cyclical) exercise protocol and the other using a static (isometric) protocol. Having established reliable methods of using each as a preoperative test, the metabolic output i.e. the measurable venous products of metabolism; lactate, SO2, PO2, PCO2, pH and tissue oxygenation were compared. The comparison showed that the isometric exercise model was the stronger stimulus for anaerobic respiration. Each exercise model was also compared to an anaerobic threshold as measured by cardiopulmonary exercise testing in the same individuals. The isometric model showed a consistent and statistically significant relationship with the anaerobic threshold as measured by cardiopulmonary exercise testing but not the cyclical model.Finally the isometric forearm exercise model was prospectively tested in a pilot study of 21 orthopaedic patients undergoing joint replacement surgery for its ability to predict surgical outcome. The maximal voluntary contraction from handgrip dynamometry was predictive of complications and length of stay and although not statistically significant there was a clear trend for those with fewer complications and shorter lengths of hospital stay to produce more lactate during isometric forearm exercise testing.

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