Factors influencing decision-making processes for intensive care therapy goals: A systematic integrative review.

BACKGROUND: Delivering intensive care therapies concordant with patients' values and preferences is considered gold standard care. To achieve this, healthcare professionals must better understand decision-making processes and factors influencing them. AIM: The aim of this study was to explore factors influencing decision-making processes about implementing and limiting intensive care therapies. DESIGN: Systematic integrative review, synthesising quantitative, qualitative, and mixed-methods studies. METHODS: Five databases were searched (Medline, The Cochrane central register of controlled trials, Embase, PsycINFO, and CINAHL plus) for peer-reviewed, primary research published in English from 2010 to Oct 2022. Quantitative, qualitative, or mixed-methods studies focussing on intensive care decision-making were included for appraisal. Full-text review and quality screening included the Critical Appraisal Skills Program tool for qualitative and mixed methods and the Medical Education Research Quality Instrument for quantitative studies. Papers were reviewed by two authors independently, and a third author resolved disagreements. The primary author developed a thematic coding framework and performed coding and pattern identification using NVivo, with regular group discussions. RESULTS: Of the 83 studies, 44 were qualitative, 32 quantitative, and seven mixed-methods studies. Seven key themes were identified: what the decision is about; who is making the decision; characteristics of the decision-maker; factors influencing medical prognostication; clinician-patient/surrogate communication; factors affecting decisional concordance; and how interactions affect decisional concordance. Substantial thematic overlaps existed. The most reported decision was whether to withhold therapies, and the most common decision-maker was the clinician. Whether a treatment recommendation was concordant was influenced by multiple factors including institutional cultures and clinician continuity. CONCLUSION: Decision-making relating to intensive care unit therapy goals is complicated. The current review identifies that breadth of decision-makers, and the complexity of intersecting factors has not previously been incorporated into interventions or considered within a single review. Its findings provide a basis for future research and training to improve decisional concordance between clinicians and patients/surrogates with regards to intensive care unit therapies.

A Delphi study to obtain consensus on medical emergency team (MET) stand-down decision making.

AIM: A medical emergency team (MET) stand-down decision is the decision to end a MET response and hand responsibility for the patient back to ward staff for ongoing management. Little research has explored this decision. This study aimed to obtain expert consensus on the essential elements required to make optimal MET call stand-down decisions and the communication required before MET departure. DESIGN: A Delphi design was utilised. METHODS: An expert panel of 10 members were recruited based on their expert knowledge and recent clinical MET responder experience in acute hospital settings. Participants were emailed a consent form and an electronic interactive PDF for each survey. Two rounds were conducted with no attrition between rounds. The CREDES guidance on conducting and reporting Delphi studies was used to report this study. RESULTS: Consensus by an expert panel of 10 MET responders generated essential elements of MET stand-down decisions. Essential elements comprised of two steps: (1) the stand-down decision that was influenced by both the patient situation and the ward/organisational context; and (2) the communication required before actioning stand-down. Communication after the decision required both verbal discussions and written documentation to hand over patient responsibility. Specific patient information, a management plan and an escalation plan were considered essential. CONCLUSION: The Delphi surveys reached consensus on the actions and communication required to stand down a MET call. Passing responsibility back to ward staff after a MET call requires both patient and ward safety assessments, and a clearly articulated patient plan for ward staff. Observation of MET call stand-down decision-making is required to validate the essential elements. IMPLICATION FOR THE PROFESSION AND PATIENT/OR PATIENT CARE: In specifying the essential elements, this study offers clinical and MET staff a process to support the handing over of clinical responsibility from the MET to the ward staff, and clarification of management plans in order to reduce repeat MET calls and improve patient outcomes. IMPACT: Minimal research has been focussed on the decision to hand responsibility back to ward staff so the MET may leave the ward with safety plan in place. This study provided expert consensus to optimise MET stand-down decision-making and the ultimate decision to end a MET call. Communication of agreed patient treatment and escalation plans is recommended before leaving the ward. This study can be used as a checklist for MET responder staff making these decisions and ward staff responsible for post-MET call care. The aim being to reduce the likelihood of potentially preventable repeat deterioration in the MET patient population. REPORTING METHOD: The CREDES guidance on conducting and reporting Delphi studies. PATIENT OR PUBLIC CONTRIBUTION: None.

The adequacy of user seal checking for N95 respirators compared to formal fit testing: A multicentred observational study.

OBJECTIVE: The objective of this study was to evaluate the adequacy of the user seal check (USC) in predicting N95 respirator fit. DESIGN: This was a prospective, observational study conducted from May to September 2020. SETTING: The study setting included three private intensive care units (ICUs) in Victoria, Australia. PARTICIPANTS: ICU staff members in three private ICUs in Melbourne and regional Victoria participated in this study. MAIN OUTCOME MEASURES: The main outcome measure is the proportion of participants who passed a USC and subsequently failed fit testing of an N95 respirator. INTERVENTION: Three different respirators were available: two N95 respirator brands and CleanSpace HALO® powered air-purifying respirator. Participants were sequentially tested on N95 respirators followed by powered air-purifying respirators until either successful fit testing or failure of all three respirators. The first N95 tested was based on the availability on the day of testing. The primary outcome was failure rate of fit testing on the first N95 respirator type passing a USC. RESULTS: Of 189 participants, 22 failed USC on both respirators, leaving 167 available for the primary outcome. Fifty-one of 167 (30.5%, 95% confidence interval = 23.7-38.1) failed fit testing on the first respirator type used that had passed a USC. CONCLUSION: USC alone was inadequate in assessing N95 respirator fit and failed to detect inadequate fit in 30% of participants. Mandatory fit testing is essential to ensure adequate respiratory protection against COVID-19 and other airborne pathogens. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry: ACTRN12620001193965.

The impact of distance on post-ICU disability.

BACKGROUND: Nonurban residential living is associated with adverse outcomes for a number of chronic health conditions. However, it is unclear what effect it has amongst survivors of critical illness. OBJECTIVES: The purpose of this study is to determine whether patients living greater than 50 km from the treating intensive care unit (ICU) have disability outcomes at 6 months that differ from people living within 50 km. METHODS: This was a multicentre, prospective cohort study conducted in five metropolitan ICUs. Participants were adults admitted to the ICU, who received >24 h of mechanical ventilation and survived to hospital discharge. In a secondary analysis of these data, the cohort was dichotomised based on residential distance from the treating ICU: <50 km and ≥50 km. The primary outcome was patient-reported disability using the 12-item World Health Organization's Disability Assessment Schedule (WHODAS 2.0). This was recorded at 6 months after ICU admission by telephone interview. Secondary outcomes included health status as measured by EQ-5D-5L return to work and psychological function as measured by the Hospital Anxiety and Depression Scale (HADS). Multivariable logistic regression was used to assess the association between distance from the ICU and moderate to severe disability, adjusted for potential confounders. Variables included in the multivariable model were deemed to be clinically relevant and had baseline imbalance between groups (p < 0.10). These included marital status and hours of mechanical ventilation. Sensitivity analysis was also conducted using distance in kilometres as a continuous variable. RESULTS: A total of 262 patients were enrolled, and 169 (65%) lived within 50 km of the treating ICU and 93 (35%) lived ≥50 km from the treating ICU (interquartile range [IQR] 10-664 km). There was no difference in patient-reported disability at 6 months between patients living <50 km and those living ≥50 km (WHODAS total disability % [IQR] 10.4 [2.08-25] v 14.6 [2.08-20.8], P = 0.74). There was also no difference between groups for the six major life domains of the WHODAS. There was no difference in rates of anxiety or depression as measured by HADS score (HADS anxiety median [IQR] 4 [1-7] v 3 [1-7], P = 0.60) (HADS depression median [IQR] 3 [1-6] v 3 [1-6], P = 0.62); health status as measured by EQ-5D (mean [SD] 66.7 [20] v 69.8 [22.2], P = 0.24); or health-related unemployment (% (N) 39 [26] v 25 [29.1], P = 0.61). After adjusting for confounders, living ≥50 km from the treating ICU was not associated with increased disability (odds ratio 0.61, 95% confidence interval: 0.33-1.16; P = 0.13) CONCLUSIONS: Survivors of intensive care in Victoria, Australia, who live at least 50 km from the treating ICU did not have greater disability than people living less than 50 km at 6 months after discharge. Living 50 km or more from the treating ICU was not associated with disability, nor was it associated with anxiety or depression, health status, or unemployment due to health.

End-of-life care and intensive care unit clinician involvement in a private acute care hospital: A retrospective descriptive medical record audit.

INTRODUCTION: More Australians die in the hospital than in any other setting. This study aimed to (i) evaluate the quality of end-of-life (EOL) care in the hospital against an Australian National Standard, (ii) describe the characteristics of intensive care unit (ICU) clinician involvement in EOL care, and (iii) explore the demographic and clinical factors associated with quality of EOL care. METHOD: A retrospective descriptive medical record audit was conducted on 297 adult inpatients who died in 2017 in a private acute care hospital in Melbourne, Australia. Data collected related to 20 'Processes of Care', considered to contribute to the quality of EOL care. The decedent sample was separated into three cohorts as per ICU clinician involvement. RESULTS: The median age of the sample was 81 (25th-75th percentile = 72-88) years. The median tally for EOL care quality was 16 (25th-75th percentile = 13-17) of 20 care processes. ICU clinicians were involved in 65.7% (n = 195) of cases; however, contact with the ICU outreach team or an ICU admission during the final inpatient stay was negatively associated with quality of EOL care (coefficient = -1.51 and -2.07, respectively). Longer length of stay was positively associated with EOL care (coefficient = .05). Specialist palliative care was involved in 53% of cases, but this was less likely for those admitted to the ICU (p < .001). Evidence of social support, bereavement follow-up, and religious support were low across all cohorts. CONCLUSION: Statistically significant differences in the quality of EOL care and a negative association between ICU involvement and EOL care quality suggest opportunities for ICU outreach clinicians to facilitate discussion of care goals and the appropriateness of ICU admission. Advocating for inclusion of specialist palliative care and nonclinical support personnel in EOL care has merit. Future research is necessary to investigate the relationship between ICU intervention and EOL care quality.

Measuring the success of Medical Emergency Teams: potentially preventable deaths versus total cardiac arrest deaths. A single centre observational study.

BACKGROUND: Rapid response systems have been implemented with the aim of preventing patient deterioration, in-hospital cardiac arrests (IHCA) and related deaths. Not all 'unexpected deaths' are preventable, thus compromising the use of unexpected deaths as an outcome measure. AIMS: To assess temporal trends in potentially preventable deaths as a subset of total unexpected death rates over a 4-year period. METHODS: A single centre, cohort study of all unexpected deaths between 1 January 2010 and 31 December 2013. Unexpected deaths were identified from the rapid response systems database and patients' case histories were reviewed to reclassify the deaths into one of three categories: potentially preventable: if earlier MET activation may have prevented death; missed not for resuscitation opportunity; and not preventable. Total bed days were obtained from the hospital's patient administration system. RESULTS: The rate of potentially preventable deaths decreased from 5.3 to 0.7 per 100 000 bed days (incident rate ratio (IRR) 0.53 (95% CI 0.31-0.90), P = 0.02). The rate of total unexpected deaths was unchanged (IRR 0.96 (0.80-1.16), P = 0.70), as were the rates of non-preventable deaths (IRR 1.06 (0.78-1.42), P = 0.72) and missed NFR deaths (IRR 1.1 (0.83-1.42), P = 0.56). CONCLUSION: The rate of potentially preventable deaths has decreased by 47% per year over a 4-year period without any change in the overall rate of unexpected deaths. Distinguishing between potentially preventable deaths in contrast to total unexpected deaths enables more targeted evaluation of rapid response systems.

'Why didn't you write a not-for-cardiopulmonary resuscitation order?' Unexpected death or failure of process?

Objective The aim of the present study was to understand the reasons for the delivery of non-beneficial cardiopulmonary resuscitation (CPR) attempts in a tertiary private hospital over 12 months. We determined doctors' expectations of survival after CPR for their patient, whether they had considered a not-for-resuscitation (NFR) order and the barriers to completion of NFR orders. Methods Anonymous questionnaires were sent to the doctors primarily responsible for a given patient's care in the hospital within 2 weeks of the unsuccessful CPR attempt. The data were analysed quantitatively where appropriate and qualitatively for themes for open-text responses Results Most doctors surveyed in the present study understood the poor outcome after CPR in the older person. Most doctors had an expectation that their own patient had a poor prognosis and a poor likely predicted outcome after CPR. This implied that the patient's death was neither unexpected nor likely to be reversible. Some doctors considered NFR orders, but multiple barriers to completion were cited, including the family's wishes, being time poor and diffusion or deferral of responsibility. Conclusions It is likely that futile CPR is provided contrary to policy and legal documents relating to end-of-life care, with the potential for harms relating to both patient and family, and members of resuscitation teams. The failure appears to relate to process rather than recognition of poor patient outcome. What is known about the topic? Mandatory CPR has been established in Australian hospitals on the premise that it will save lives. The outcome from in-hospital cardiac arrest has not improved despite significant training and resources. The outcome for those acutely hospitalised patients aged over 80 years has been repeatedly demonstrated to be poor with significant morbidity in the survivors. There is emerging literature on the extent of the delivery of non-beneficial treatments at the end of life, including futile CPR, the recognition of harms incurred by patients, families and members of the resuscitation teams and on the opportunity cost of the inappropriate use of resources. What does this paper add? This is the first study, to our knowledge, that has demonstrated that doctors understood the outcomes for CPR, particularly in those aged 80 years and older, and that failure to recognise poor outcome and prognosis in their own patients is not a barrier to writing NFR orders. What are the implications for practitioners? Recognition of the poor outcomes from CPR for the elderly patient for whom the doctor has a duty of care should result in a discussion with the patients, allowing an exploration of values and expectations of treatment. This would promote shared decision making, which includes the use of CPR. Facilitation of these discussions should be the focus of health service review.

Early serum creatinine accurately predicts acute kidney injury post cardiac surgery.

BACKGROUND: Acute Kidney Injury (AKI) is a well recognized complication of cardiac surgery. It is associated with significant morbidity and mortality. The aims of our study are twofold; 1. To define the incidence of AKI post cardiac surgery. 2. To identify pre-morbid and operative risk factors for developing AKI and to determine if immediate post operative serum creatinine (IPOsCr) accurately predicts the development of AKI. METHODS: We prospectively studied 196 consecutive patients undergoing elective (on-pump) cardiac surgery. Baseline patient characteristics, including medical co-morbidities, proteinuria, procedural data and kidney function (serum creatinine (sCr) were collected. Internationally standardised criteria for AKI were used (sCr >1.5 times baseline, elevation in sCr >26.4 µmmol/L (0.3 mg/dl). Measurements were collected pre-operatively, within 2 h of surgical completion (IPOsCr) and daily for two days. Logistic regression was used to assess predictive factors for AKI including IPOsCr. Model discrimination was assessed using ROC AUC curves. RESULTS: Forty (20.4%) patients developed AKI postoperatively. Hypertension (OR 2.64, p = 0.02), diabetes (OR 2.25, p = 0.04), proteinuria (OR 2.48, p = 0.02) and a lower baseline eGFR (OR 0.74, p = 0.002) were associated with AKI in univariate analysis. A multivariate logistic model with preoperative and surgical factors (age, gender, eGFR, proteinuria, hypertension, diabetes and type of cardiac surgery) demonstrated moderate discrimination for AKI (ROC AUC 0.76). The addition of IPOsCr improved model discrimination for AKI (AUC 0.82, p = 0.07 versus baseline AUC) and was independently associated with AKI (OR 7.17; 95% CI 1.27-40.32; p = 0.025). CONCLUSIONS: One in 5 patients developed AKI post cardiac surgery. These patients have significantly increased morbidity and mortality. IPOsCr is significantly associated with the development of AKI, providing a cheap readily available prognostic marker.

No ψ-epistemic model can fully explain the indistinguishability of quantum states.

According to a recent no-go theorem [M. Pusey, J. Barrett and T. Rudolph, Nat. Phys. 8, 475 (2012)], models in which quantum states correspond to probability distributions over the values of some underlying physical variables must have the following feature: the distributions corresponding to distinct quantum states do not overlap. In such a model, it cannot coherently be maintained that the quantum state merely encodes information about underlying physical variables. The theorem, however, considers only models in which the physical variables corresponding to independently prepared systems are independent, and this has been used to challenge the conclusions of that work. Here we consider models that are defined for a single quantum system of dimension d, such that the independence condition does not arise, and derive an upper bound on the extent to which the probability distributions can overlap. In particular, models in which the quantum overlap between pure states is equal to the classical overlap between the corresponding probability distributions cannot reproduce the quantum predictions in any dimension d ≥ 3. Thus any ontological model for quantum theory must postulate some extra principle, such as a limitation on the measurability of physical variables, to explain the indistinguishability of quantum states. Moreover, we show that as d→∞, the ratio of classical and quantum overlaps goes to zero for a class of states. The result is noise tolerant, and an experiment is motivated to distinguish the class of models ruled out from quantum theory.

Memory attacks on device-independent quantum cryptography.

Device-independent quantum cryptographic schemes aim to guarantee security to users based only on the output statistics of any components used, and without the need to verify their internal functionality. Since this would protect users against untrustworthy or incompetent manufacturers, sabotage, or device degradation, this idea has excited much interest, and many device-independent schemes have been proposed. Here we identify a critical weakness of device-independent protocols that rely on public communication between secure laboratories. Untrusted devices may record their inputs and outputs and reveal information about them via publicly discussed outputs during later runs. Reusing devices thus compromises the security of a protocol and risks leaking secret data. Possible defenses include securely destroying or isolating used devices. However, these are costly and often impractical. We propose other more practical partial defenses as well as a new protocol structure for device-independent quantum key distribution that aims to achieve composable security in the case of two parties using a small number of devices to repeatedly share keys with each other (and no other party).

Device-independent certification of indefinite causal order in the quantum switch.

Quantum theory is compatible with scenarios in which the order of operations is indefinite. Experimental investigations of such scenarios, all of which have been based on a process known as the quantum switch, have provided demonstrations of indefinite causal order conditioned on assumptions on the devices used in the laboratory. But is a device-independent certification possible, similar to the certification of Bell nonlocality through the violation of Bell inequalities? Previous results have shown that the answer is negative if the switch is considered in isolation. Here, however, we present an inequality that can be used to device-independently certify indefinite causal order in the quantum switch in the presence of an additional spacelike-separated observer under an assumption asserting the impossibility of superluminal and retrocausal influences.

Distinct quantum states can be compatible with a single state of reality.

Perhaps the quantum state represents information about reality, and not reality directly. Wave function collapse is then possibly no more mysterious than a Bayesian update of a probability distribution given new data. We consider models for quantum systems with measurement outcomes determined by an underlying physical state of the system but where several quantum states are consistent with a single underlying state-i.e., probability distributions for distinct quantum states overlap. Significantly, we demonstrate by example that additional assumptions are always necessary to rule out such a model.

Water nucleation: A comparison between some phenomenological theories and experiment.

The predictions of several homogeneous nucleation theories are compared with experimental results for water for a range of temperatures and vapor supersaturations, S. The theoretical models considered are: classical theory (including the 1/S correction factor), the Gibbs p-form, mean-field kinetic nucleation theory (MKNT), the extended modified liquid drop model-dynamical nucleation theory, and two forms of density functional theory, one without and one with a contribution due to association. The theoretical expressions for the logarithm of the nucleation rate are expanded in a series in powers of the logarithm of S. The residual dependence (once the classical dependence has been factored out) of the experimental results shows a stronger decrease with increasing temperature than all the theories except MKNT. The residual S-dependence of the experimental results decreases with increasing supersaturation whereas all the theories except the Gibbs p-form predict an increase. The first correction term to classical theory involves both the liquid compressibility and curvature correction to the surface tension (Tolman length) so the experimental results suggest that the Tolman length is zero (as assumed in the Gibbs p-form) or positive whereas the other theories predict a negative Tolman length. The effect of including a term proportional to ln(lnS) in the series expansion is also discussed.

How much measurement independence is needed to demonstrate nonlocality?

If nonlocality is to be inferred from a violation of Bell's inequality, an important assumption is that the measurement settings are freely chosen by the observers, or alternatively, that they are random and uncorrelated with the hypothetical local variables. We demonstrate a connection between models that weaken this assumption, allowing partial correlation, and (i) models that allow classical communication between the distant parties, (ii) models that exploit the detection loophole. Even if Bob's choices are completely independent, all correlations from projective measurements on a singlet can be reproduced, with mutual information between Alice's choice and local variables less than or equal to one bit.

Cyclic quantum causal models.

Causal reasoning is essential to science, yet quantum theory challenges it. Quantum correlations violating Bell inequalities defy satisfactory causal explanations within the framework of classical causal models. What is more, a theory encompassing quantum systems and gravity is expected to allow causally nonseparable processes featuring operations in indefinite causal order, defying that events be causally ordered at all. The first challenge has been addressed through the recent development of intrinsically quantum causal models, allowing causal explanations of quantum processes - provided they admit a definite causal order, i.e. have an acyclic causal structure. This work addresses causally nonseparable processes and offers a causal perspective on them through extending quantum causal models to cyclic causal structures. Among other applications of the approach, it is shown that all unitarily extendible bipartite processes are causally separable and that for unitary processes, causal nonseparability and cyclicity of their causal structure are equivalent.

The psychometric properties and minimal clinically important difference for disability assessment using WHODAS 2.0 in critically ill patients.

Objectives: The 12-item World Health Organization Disability Assessment Schedule 2.0 (WHODAS 2.0) provides a standardised method for measuring health and disability. This study aimed to determine its reliability, validity and responsiveness and to establish the minimum clinically important difference (MCID) in critically ill patients. Design: Prospective, multicentre cohort study. Setting: Intensive care units of six metropolitan hospitals. Participants: Adults mechanically ventilated for > 24 hours. Main outcome measures: Reliability was assessed by measuring internal consistency. Construct validity was assessed by comparing WHODAS 2.0 scores at 6 months with the EuroQoL visual analogue scale (EQ VAS) and Lawton Instrumental Activities of Daily Living (IADL) scale scores. Responsiveness was evaluated by assessing change over time, effect sizes, and percentage of patients showing no change. The MCID was calculated using both anchor and distribution-based methods with triangulation of results. Main results: A baseline and 6-month WHODAS 2.0 score were available for 448 patients. The WHODAS 2.0 demonstrated good correlation between items with no evidence of item redundancy. Cronbach α coefficient was 0.91 and average split-half coefficient was 0.91. There was a moderate correlation between the WHODAS 2.0 and the EQ VAS scores (r = -0.72; P < 0.001) and between the WHODAS 2.0 and the Lawton IADL scores (r = -0.66; P < 0.001) at 6 months. The effect sizes for change in the WHODAS 2.0 score from baseline to 3 months and from 3 to 6 months were low. Ceiling effects were not present and floor effects were present at baseline only. The final MCID estimate was 10%. Conclusion: The 12-item WHODAS 2.0 is a reliable, valid and responsive measure of disability in critically ill patients. A change in the total WHODAS 2.0 score of 10% represents the MCID.

On the thermodynamic expansion of the nucleation free-energy barrier.

Mean field density functional theory is used to calculate the nucleation free-energy barrier height, W( *), in vapor-liquid nucleation as a function of the excess chemical potential Deltamu. Calculations are performed for a range of temperatures and for both Lennard-Jones and Yukawa interactions, scaled to give the same bulk properties. The leading terms in the expansion of W( *) in powers of Deltamu depend on the planar surface tension and the planar limit of the Tolman length, which are obtained from density functional calculations for planar interfaces. The first correction term to the large cluster (classical) limit is proportional to (Deltamu)(-1) and is shown to be significant. For the Lennard-Jones interaction, W( *) also includes a term proportional to ln(Deltamu). Once the leading terms are subtracted from W( *), the residual is almost independent of Deltamu. For the Yukawa fluid, values for this residual are compared to values found using a new formula for the rigidity constants and satisfactory agreement is found.

Random phase approximation for the non-uniform Yukawa fluid.

Mean-field density functional theory can be used to estimate the free energy of non-uniform fluids. The second functional derivative with respect to density of the free energy is related to the direct correlation function of the fluid and, in principle, this can be inverted to find an improved approximation for the pair correlation function and hence the free energy, the so-called 'random phase approximation'. If the repulsive molecular interaction is approximated by the local density approximation and the attractive interaction is assumed to be of the Yukawa form, the problem reduces to that of finding the eigenvalues of Schrödinger-like equations, which, for certain models (such as the 'Φ4 model'), can be done analytically in the planar case. The relationship between this approach and field theoretical treatment of the vapour-liquid interface is discussed. The ultraviolet divergence of the expression can be eliminated by separating the first term in the expansion, although quantitative results still depend on the behaviour of the attractive potential in the repulsive core. In the case of a spherical droplet of radius R, correction terms to the free energy involving lnR appear due to (i) cluster translational invariance, (ii) the unstable mode corresponding to droplet growth, and (iii) capillary waves. The net effect of these terms is to modify the classical expression for the nucleation rate by a factor proportional to R 4/3.