Contrary to large population studies, our systematic review of the relationship between preoperative handgrip strength and postoperative outcome did not find compelling data to support the hypothesis that the results of studies in the general population translate to perioperative medicine. The majority of studies were considered to be of reasonable quality. Despite these quality scores, many studies contained important potential confounding factors which varied markedly between studies. A range of different instruments have been employed to measure grip strength, with other corroborative assessments of strength being frequently absent. Due to the substantial variation in the way in which each specified outcome had been defined between studies, plus the lack of analyses testing any one particular association, it was not possible to perform meta-analyses of results or formally test the heterogeneity (consistency) between studies. This marked heterogeneity between studies limits any definitive conclusions for the perioperative environment and renders this preoperative assessment largely unexplored. Nevertheless, several of these studies - albeit with the limitations as discussed above - suggest the role for preoperative handgrip strength assessment should be explored further.
Large epidemiological studies have shown that perioperative morbidity is associated with dramatic differences in post-discharge life expectancy across different operations and health systems . The cost and expertise required by certain preoperative tests, such as cardiopulmonary exercise testing, plus other limiting factors (e.g. dysmobility, acuity of surgery) necessitates an alternative approach to be developed for the objective assessment of perioperative risk in the substantial minority of patients who may sustain morbidity that impacts on their longer-term survival. The development of an inexpensive, mass screening preoperative assessment tool with high sensitivity and specificity to detect postoperative morbidity is clearly attractive. Handgrip strength is an easy, non-invasive, cheap, real-time and established independent "bedside" predictor of long-term all-cause mortality in more than 44,000 patients studied in the general population .
There are also compelling basic biological reasons for establishing the role of handgrip strength in preoperative assessment. Cardiopulmonary reserve is a long-established predictor of cardiovascular and all-cause mortality, in both asymptomatic individuals and patients with cardiovascular disease . Cardiac insufficiency has emerged as the commonest preoperative morbidity associated with increased morbidity and mortality [36, 37]. An important component of cardiac failure is dysfunctional skeletal muscle metabolism  and impaired strength - as reflected by handgrip strength . Skeletal muscle exerts important effects on the patterns of substrate use during periods of increased cardiopulmonary performance [40, 41]. Major alterations in skeletal muscle histology and biochemistry occur in patients with long-term heart failure [42, 43]. These skeletal muscle adaptations may underlie the early onset of anaerobic metabolism, increased lactate production and fatigue in heart failure. Handgrip strength improves following specific interventions that increase cardiopulmonary reserve [44, 45]. Muscle (handgrip) strength is also impaired in metabolic disease , which may in part explain its association with both poorer perioperative outcomes and all-cause mortality.
One limitation of this systematic review is that no original study data were retrieved, although given the heterogeneity of both study design and the surgical populations in question this would have been unlikely to alter the main conclusions. Because only published reports were examined (obtained from searches performed only on MEDLINE, EMBASE and Cochrane databases), a formal assessment of publication bias was not undertaken. It remains possible that not all relevant studies may have been identified since unpublished studies were not sought. There is very little perioperative demographic data provided in these studies, including cardiovascular risk and the identification of higher risk patients. Standards of postoperative care were not reported or apparently standardized. Since no interventions were conducted based on preoperative handgrip strength assessment, the studies only provide associative conclusions.
This systematic review has generated two significant clinical implications. Firstly, given the compelling general population data that predicts longevity, there is clearly a need for the further prospective assessment of whether preoperative handgrip strength can help stratify risk of adverse postoperative outcomes. Second, these studies demonstrate that handgrip strength is a feasible, pragmatic, real-time bedside tool that may enhance preoperative risk stratification.