Clinical symptoms, signs and tests for identification of impending and current water-loss dehydration in older people.

BACKGROUND: There is evidence that water-loss dehydration is common in older people and associated with many causes of morbidity and mortality. However, it is unclear what clinical symptoms, signs and tests may be used to identify early dehydration in older people, so that support can be mobilised to improve hydration before health and well-being are compromised. OBJECTIVES: To determine the diagnostic accuracy of state (one time), minimally invasive clinical symptoms, signs and tests to be used as screening tests for detecting water-loss dehydration in older people by systematically reviewing studies that have measured a reference standard and at least one index test in people aged 65 years and over. Water-loss dehydration was defined primarily as including everyone with either impending or current water-loss dehydration (including all those with serum osmolality ≥ 295 mOsm/kg as being dehydrated). SEARCH METHODS: Structured search strategies were developed for MEDLINE (OvidSP), EMBASE (OvidSP), CINAHL, LILACS, DARE and HTA databases (The Cochrane Library), and the International Clinical Trials Registry Platform (ICTRP). Reference lists of included studies and identified relevant reviews were checked. Authors of included studies were contacted for details of further studies. SELECTION CRITERIA: Titles and abstracts were scanned and all potentially relevant studies obtained in full text. Inclusion of full text studies was assessed independently in duplicate, and disagreements resolved by a third author. We wrote to authors of all studies that appeared to have collected data on at least one reference standard and at least one index test, and in at least 10 people aged ≥ 65 years, even where no comparative analysis has been published, requesting original dataset so we could create 2 x 2 tables. DATA COLLECTION AND ANALYSIS: Diagnostic accuracy of each test was assessed against the best available reference standard for water-loss dehydration (serum or plasma osmolality cut-off ≥ 295 mOsm/kg, serum osmolarity or weight change) within each study. For each index test study data were presented in forest plots of sensitivity and specificity. The primary target condition was water-loss dehydration (including either impending or current water-loss dehydration). Secondary target conditions were intended as current (> 300 mOsm/kg) and impending (295 to 300 mOsm/kg) water-loss dehydration, but restricted to current dehydration in the final review.We conducted bivariate random-effects meta-analyses (Stata/IC, StataCorp) for index tests where there were at least four studies and study datasets could be pooled to construct sensitivity and specificity summary estimates. We assigned the same approach for index tests with continuous outcome data for each of three pre-specified cut-off points investigated.Pre-set minimum sensitivity of a useful test was 60%, minimum specificity 75%. As pre-specifying three cut-offs for each continuous test may have led to missing a cut-off with useful sensitivity and specificity, we conducted post-hoc exploratory analyses to create receiver operating characteristic (ROC) curves where there appeared some possibility of a useful cut-off missed by the original three. These analyses enabled assessment of which tests may be worth assessing in further research. A further exploratory analysis assessed the value of combining the best two index tests where each had some individual predictive ability. MAIN RESULTS: There were few published studies of the diagnostic accuracy of state (one time), minimally invasive clinical symptoms, signs or tests to be used as screening tests for detecting water-loss dehydration in older people. Therefore, to complete this review we sought, analysed and included raw datasets that included a reference standard and an index test in people aged ≥ 65 years.We included three studies with published diagnostic accuracy data and a further 21 studies provided datasets that we analysed. We assessed 67 tests (at three cut-offs for each continuous outcome) for diagnostic accuracy of water-loss dehydration (primary target condition) and of current dehydration (secondary target condition).Only three tests showed any ability to diagnose water-loss dehydration (including both impending and current water-loss dehydration) as stand-alone tests: expressing fatigue (sensitivity 0.71 (95% CI 0.29 to 0.96), specificity 0.75 (95% CI 0.63 to 0.85), in one study with 71 participants, but two additional studies had lower sensitivity); missing drinks between meals (sensitivity 1.00 (95% CI 0.59 to 1.00), specificity 0.77 (95% CI 0.64 to 0.86), in one study with 71 participants) and BIA resistance at 50 kHz (sensitivities 1.00 (95% CI 0.48 to 1.00) and 0.71 (95% CI 0.44 to 0.90) and specificities of 1.00 (95% CI 0.69 to 1.00) and 0.80 (95% CI 0.28 to 0.99) in 15 and 22 people respectively for two studies, but with sensitivities of 0.54 (95% CI 0.25 to 0.81) and 0.69 (95% CI 0.56 to 0.79) and specificities of 0.50 (95% CI 0.16 to 0.84) and 0.19 (95% CI 0.17 to 0.21) in 21 and 1947 people respectively in two other studies). In post-hoc ROC plots drinks intake, urine osmolality and axillial moisture also showed limited diagnostic accuracy. No test was consistently useful in more than one study.Combining two tests so that an individual both missed some drinks between meals and expressed fatigue was sensitive at 0.71 (95% CI 0.29 to 0.96) and specific at 0.92 (95% CI 0.83 to 0.97).There was sufficient evidence to suggest that several stand-alone tests often used to assess dehydration in older people (including fluid intake, urine specific gravity, urine colour, urine volume, heart rate, dry mouth, feeling thirsty and BIA assessment of intracellular water or extracellular water) are not useful, and should not be relied on individually as ways of assessing presence or absence of dehydration in older people.No tests were found consistently useful in diagnosing current water-loss dehydration. AUTHORS' CONCLUSIONS: There is limited evidence of the diagnostic utility of any individual clinical symptom, sign or test or combination of tests to indicate water-loss dehydration in older people. Individual tests should not be used in this population to indicate dehydration; they miss a high proportion of people with dehydration, and wrongly label those who are adequately hydrated.Promising tests identified by this review need to be further assessed, as do new methods in development. Combining several tests may improve diagnostic accuracy.

Diagnostic accuracy of a pH stick, modified to detect gastric lipase, to confirm the correct placement of nasogastric tubes.

OBJECTIVE: The correct placement of a nasogastric feeding tube is usually confirmed by establishing that an aspirate is acidic using a pH stick. However, antacid medication and achlorhydria can cause false negative pH tests that may delay feeding and increase resource use. The purpose of this study was to evaluate a modified pH stick designed to detect gastric lipase and therefore reduce false negative tests. METHODS: In this prospective observational study, a convenience sample of adult patients who had either gastric and oesophageal samples taken during routine diagnostic gastroscopy (n=97) or bronchial and saliva samples taken during a bronchoscopy (n=106). The samples were tested by blinded observers using the modified and standard pH sticks. The sensitivities and specificities of the two pH sticks in identifying gastric and non-gastric aspirates were compared using the pH cut-off ≤5.5. RESULTS: The sensitivities of a pH≤5.5 to correctly identify gastric samples were 66% (95% CI 56 to 75) and 68% (95% CI 57 to 77) for the modified and the standard pH, respectively. The specificities were 81% (95% CI 76 to 85) and 79% (95% CI 74 to 84). There were no significant differences in the distribution of the discordant results between the paired gastric and non-gastric samples for both the modified and standard pH sticks at pH≤5.5 (both McNemar's tests, p≥0.05). CONCLUSIONS: There were no significant differences between the paired modified and standard pH tests for the gastric samples. Due to the limited accuracy of pH sticks, further research is required to identify accurate and cost-effective bedside methods to confirm the correct placement of nasogastric tubes.

Study to determine the likely accuracy of pH testing to confirm nasogastric tube placement.

OBJECTIVE: To establish the likely accuracy of pH testing to identify gastric aspirates at different pH cut-offs to confirm nasogastric tube placement. METHODS: This prospective observational study included a convenience sample of adult patients who had two (one fresh and one frozen) gastric and oesophageal samples taken during gastroscopy or two bronchial and saliva samples taken during bronchoscopy. The degree of observer agreement for the pH of fresh and frozen samples was indicted by kappa (k) statistics. The sensitivities and specificities at pH ≤5.5 and the area under the receiver operating characteristics (ROC) curve at different pH cut-offs were calculated to identify gastric and non-gastric aspirates. RESULTS: Ninety-seven patients had a gastroscopy, 106 a bronchoscopy. There was complete agreement between observers in 57/92 (62%) of the paired fresh and frozen gastric samples (k=0.496, 95% CI 0.364 to 0.627). The sensitivity of a pH ≤5.5 to correctly identify gastric samples was 68% (95% CI 57 to 77) and the specificity was 79% (95% CI 74 to 84). The overall accuracy to correctly classify samples was between 76% and 77%, regardless of whether patients were taking antacids or not. The area under the ROC curve at different pH cut-offs was 0.74. CONCLUSION: The diagnostic accuracy of pH ≤5.5 to differentiate gastric from non-gastric samples was low, regardless of whether patients were taking antacids or not. Due to the limited accuracy of the pH sticks and the operators' ability to differentiate colorimetric results, there is an urgent need to identify more accurate and safer methods to confirm correct placement of nasogastric tubes.

Abnormal breathing patterns in stroke: relationship with location of acute stroke lesion and prior cerebrovascular disease.

OBJECTIVE: To determine whether central periodic breathing (CPB) is associated with acute involvement of any particular part of the brain, or the extent of total damage in patients with acute stroke. METHODS: CPB was identified using portable monitoring equipment in patients with stroke on admission. A neuroradiologist classified acute stroke lesions and prior cerebrovascular disease on brain images. RESULTS: Among 134 patients with acute stroke, those with CPB were more likely to have a large acute stroke lesion in a cerebral hemisphere (p = 0.01) and more mass effect (p = 0.03). There was no association between CPB and severe prior cerebrovascular disease on imaging (p = 0.76). CONCLUSION: CPB is related to the acute (not old) lesions, particularly large acute cerebral hemispheric lesions with mass effect. A relationship between lesions in any discrete brain location (unilateral or bilateral) and CPB could not be shown.

Hypoxaemia in acute stroke is frequent and worsens outcome.

BACKGROUND: Hypoxaemia in the acute phase of stroke might damage the ischaemic penumbra and worsen clinical outcome. We determined the frequency of hypoxaemia on admission with stroke and assessed whether it was related to outcome. METHODS: We measured arterial oxygen saturation (SaO2) and breathing effort with portable monitoring equipment in a large cohort of acute stroke patients, continually from arrival at hospital, during interdepartment transfer, in imaging and on the ward. Patients received best medical care according to current guidelines. Baseline neurological examination and 3-month outcome (Modified Rankin Scale) were assessed blind to other data. Hypoxaemia was defined as SaO2 <90% for >or=10% of each assessment stage. RESULTS: Mean SaO2 was lowest during transfers (p < 0.01), but hypoxaemia was common in all assessment stages. Patients with hypoxaemia (30/153, 20%) were more likely to have a pre-existing respiratory disease on admission than those without hypoxaemia (p < 0.04). More patients with hypoxaemia (40%) died than those without hypoxaemia (20%) (hazard ratio, 2.0; 95% CI, 1.0-4.1), though after adjusting for National Institute of Health Stroke Scale and age this association was not statistically significant (hazard ratio, 1.5; 95% CI, 0.7-3.1). There were similar numbers of dependent survivors in both groups. CONCLUSION: Hypoxaemia during acute stroke assessment was associated with increased risk of death. Although SaO2 is lower during transfers, hypoxaemia occurs in all stages of the admission process. Further research is necessary to determine whether strategies to avoid hypoxaemia during acute assessment improve stroke survival.

Central periodic breathing observed on hospital admission is associated with an adverse prognosis in conscious acute stroke patients.

BACKGROUND: Central periodic breathing (CPB) is common following acute stroke, but its prognostic significance is uncertain. We determined the frequency of CPB on admission with stroke and assessed whether it was related to outcome. METHODS: We measured arterial oxygen saturation (SaO2), chest wall movements and nasal airflow continually with portable monitoring equipment in a large cohort of acute stroke patients, from arrival at hospital through acute assessment to reaching the ward. Baseline neurological examination and 3-month outcome (modified Rankin scale, MRS) were assessed blind to recordings. CPB was defined as cyclical rises and falls in ventilation, with intermittent reduced respiratory airflow or total apnoea. RESULTS: CPB was common in acute stroke (33/138, 24%), but was poorly recognised by clinical staff. Patients with CPB were more likely to have a total anterior circulation syndrome and higher National Institutes of Health Stroke Scale scores than those without (both p<0.01). Patients with CPB had significantly higher median SaO2 than those without (p<0.01), unrelated to whether they received oxygen or not. At 3-month follow-up: 91% of patients with CPB were dead or dependent (MRS>or=3) compared with 53% of those without (OR 8.8; 95% CI 2.5-30.5); the association remained statistically significant after adjusting for covariates (OR 5.9; 95% CI 1.4-25.4). CONCLUSION: CPB is independently associated with poor outcome after stroke, but is not by association with hypoxia. Further work is required to identify causes, effects and interventions that might improve effects of CPB.