Higher Risk Of Hypotension Research Articles

Risk factors of hypotension during cesarean section with spinal anesthesia in parturients with COVID-19: a retrospective study in comparison with pregnant women without COVID-19.

The incidence of hypotension in parturients with coronavirus disease (COVID-19) undergoing regional anesthesia remains controversial. This study aimed to investigate the incidence of hypotension during spinal anesthesia in parturients infected with COVID-19, as well as to identify associated risk factors. This retrospective study compared COVID-19-positive parturients who underwent cesarean section under spinal anesthesia (COVID-19 group) with a control group between January 2017 and June 2022. We reviewed the medical records and collected the following information: basic patient characteristics, spinal anesthesia, and newborn-related data. Compared with the control group, the COVID-19 group did not show any significant differences in terms of hypotension occurrence and vasopressor usage. A positive correlation was noted in the COVID-19 group between heart rate and duration of hospital stay (P < 0.001, Spearman's rho = 0.422). In subgroup analysis of the COVID-19 group, group with a baseline heart rate ≥ 100 (group H) had lower Apgar scores at 1 min, longer hospital stays, and more severe COVID-19 symptoms than the with a baseline heart rate < 100 (group L). Moreover, in group H, there was a positive correlation between the heart rate and the lowest systolic blood pressure after spinal anesthesia (P = 0.012, Spearman's rho = 0.528). Parturients with COVID-19 do not appear to have a higher risk of hypotension during cesarean section under spinal anesthesia than those without COVID-19. Given the close association between preoperative heart rate and extent of hypotension in parturients with COVID-19 undergoing spinal anesthesia, vigilant monitoring of vital signs by anesthesiologists is crucial during the perioperative period.

Relationship between 2nd-generation angiotensin receptor blockers and the risk of hypotension in COVID-19 patients admitted to hospital.

It has not yet been established whether angiotensin II receptor blockers (ARB), statins, and multiple drugs affect the severity of COVID-19. Therefore, we herein performed an observational study on the effects of 1st- and 2nd-generation ARB, statins, and multiple drugs, on COVID-19 in patients admitted to 15 Japanese medical facilities. The results obtained showed that ARB, statins, and multiple drugs were not associated with the primary outcome (odds ratio: 1.040, 95% confidence interval: 0.688-0.571; 0.696, 0.439-1.103; 1.056, 0.941-1.185, respectively), each component of the primary outcome (in-hospital death, ventilator support, extracorporeal membrane oxygenation support, and admission to the intensive care unit), or the secondary outcomes (oxygen administration, disturbed consciousness, and hypotension, defined as systolic blood pressure ≤90 mmHg). ARB were divided into 1st- and 2nd-generations based on their approval for use (before 2000 and after 2001), with the former consisting of losartan, candesartan, and valsartan, and the latter of telmisartan, olmesartan, irbesartan, and azilsartan. The difference of ARB generation was not associated with the primary outcome (odds ratio with 2nd-generation ARB relative to 1st-generation ARB: 1.257, 95% confidence interval: 0.613-2.574). The odd ratio for a hypotension as one of the secondary outcomes with 2nd-generation ARB was 1.754 (95% confidence interval: 1.745-1.763) relative to 1st-generation ARB. These results suggest that patients taking 2nd-generation ARB may be at a higher risk of hypotension than those taking 1st-generation ARB and also that careful observations are needed. Further studies are continuously needed to support decisions to adjust medications for co-morbidities.

The Efficacy and Safety of Sacubitril/Valsartan Compared to Valsartan in Patients with Heart Failure and Mildly Reduced and Preserved Ejection Fractions: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

Background: Sacubitril/valsartan improves heart failure (HF) outcomes in patients with heart failure with reduced ejection fraction (HFrEF). However, randomized controlled trials (RCTs) in patients with heart failure and mildly reduced ejection fraction (HFmrEF) and heart failure with preserved ejection fraction (HFpEF) have shown inconsistent results. We conducted this meta-analysis to comprehensively evaluate the efficacy and safety of sacubitril/valsartan compared to valsartan within this specific patient population. Methods: We searched the MEDLINE database and ClinicalTrials.gov and identified four RCTs that could be included in our analysis, with 3375 patients in the sacubitril/valsartan group and 3362 in the valsartan group. Results: Our study shows that, in patients with HFmrEF and HFpEF, sacubitril/valsartan was superior to valsartan in some of the key HF outcomes, such as the Kansas City Cardiomyopathy Questionnaire Clinical Summary Score (KCCQ CSS), with a small but significant mean difference of 1.13 (95% confidence interval or CI of 0.15 to 2.11, p-value 0.024), an improvement in the New York Heart Association (NYHA) class (odds ratio or OR of 1.32, 95% CI 1.11 to 1.58, p-value 0.002), and the composite outcome of hospitalizations for HF and cardiovascular death, with a relative risk (RR) of 0.86 (95% CI 0.75 to 0.99, p-value 0.04). However, there was no additional benefit with sacubitril/valsartan compared to valsartan for the outcomes of cardiovascular death and all-cause mortality. In terms of side effects, sacubitril/valsartan was associated with a higher risk of hypotension when compared to valsartan (OR 1.67, 95% CI 1.27 to 2.19, p-value < 0.0001), but did not show an increased risk of hyperkalemia or worsening renal function. Conclusions: In individuals with HFmrEF or HFpEF, sacubitril/valsartan can result in improvements in the HF outcomes of the KCCQ CSS, the NYHA class, and the composite outcome of hospitalization for HF and cardiovascular death when compared to valsartan. While there was a higher risk of hypotension with sacubitril/valsartan compared to valsartan, there was no corresponding increase in the risk of hyperkalemia or worsening renal function.

Association between body mass and hypotension in dogs under general anaesthesia.

To investigate the association between body mass and hypotension during general anaesthesia in dogs undergoing surgical and diagnostic procedures within a referral hospital. Retrospective evaluation of the anaesthetic records of 1789 dogs was performed. Data on signalment, anaesthetic protocol and physiological variables, including mean arterial pressure, were collected. A multivariable generalised linear model was used to identify associations between explanatory variables, including body mass, and hypotension. In the population studied, increasing body mass (per 10 kg) was significantly associated with decreasing odds of hypotension (odds ratio 0.68; 95% confidence interval: 0.60 to 0.77). Additional variables associated with a decreased odds of hypotension were pre-anaesthetic medication with alpha-2 agonists (odds ratio 0.63; 95% confidence interval 0.48 to 0.82) and increasedbody temperature (per 1°C) during general anaesthesia (odds ratio 0.77; 95% confidence interval 0.67 to 0.88). Brachycephaly (odds ratio 1.72; 95% confidence interval 1.25 to 2.38), ASA physical status classification >3 (odds ratio 2.03; 95% confidence interval 1.16 to 3.56), undergoing a surgical procedure (versus diagnostic) (odds ratio 1.57; 95% confidence interval 1.10 to 2.23) and bradycardia (odds ratio 1.37; 95% confidence interval 1.05 to 1.80) were independently associated with increased odds of hypotension. Dogs of lower body mass and brachycephalic breeds may be at higher risk of hypotension during general anaesthesia or alternatively represent subpopulations in which accurate blood pressure measurement presents a greater challenge. Monitoring blood pressure accurately in these groups requires particular attention and provisions for treating hypotension should be readily accessible.

Prophylactic Administration with Methylene Blue Improves Hemodynamic Stabilization During Obstructive Jaundice–Related Diseases’ Operation: a Blinded Randomized Controlled Trial

ObjectivesPatients with obstruction jaundice are at a high risk of hypotension and need high volume of fluids and a high dose of catecholamine to maintain organ perfusion during operation procedure. All these likely contribute to high perioperative morbidity and mortality. The aim of the study is to evaluate the effects of methylene blue on the hemodynamics in patients undergoing surgeries associated with obstructive jaundice. DesignA prospective, randomized, and controlled clinical study. SettingThe enrolled patients randomly received 2 mg/kg of methylene blue in saline or saline (50 ml) before anesthesia induction. The primary outcome was the frequency and dose of noradrenaline administration to maintain mean arterial blood pressure over 65 mmHg or > 80% of baseline, and systemic vascular resistance (SVR) over 800 dyne/s/cm5 during operation. The secondary outcomes were liver and kidney functions, and ICU stay. PatientsSeventy patients were enrolled in the study and randomly assigned to receive either methylene blue or control (n = 35/group). ResultsFewer patients received noradrenaline in the methylene blue group when compared with the control group (13/35 vs 23/35, P = 0.017), and the noradrenaline dose administrated during operation was reduced in the methylene blue group when compared with the control group (0.32±0.57 mg vs 1.787±3.51 mg, P = 0.018). The blood level of creatinine, glutamic oxalacetic transaminase, and glutamic–pyruvic transaminase after the operation was reduced in the methylene blue group when compared with the control group. ConclusionsProphylactic administration of methylene blue before operation associated with obstructive jaundice improves hemodynamic stability and short-term prognosis. QuestionMethylene blue use prevented refractory hypotension during cardiac surgery, sepsis, or anaphylactic shock. It is still unknown that methylene blue on the vascular hypo-tone associated with obstructive jaundice. FindingsProphylactic administration with methylene blue improved peri-operative hemodynamic stability, and hepatic and kidney function on the patients with obstructive jaundice. MeaningsMethylene blue is a promising and recommended drug for the patients undergoing the surgeries of relief obstructive jaundice during peri-operation management.

Network Meta-Analysis Comparing Angiotensin Receptor-Neprilysin Inhibitors, Angiotensin Receptor Blockers, and Angiotensin-Converting Enzyme Inhibitors in Heart Failure With Reduced Ejection Fraction

The superiority of angiotensin receptor-neprilysin inhibitor (ARNI) over angiotensin-converting enzyme inhibitor (ACE-I) and angiotensin receptor blocker (ARB) has not been reassessed after the publication of recent trials that did not find clinical benefits. Therefore, we performed an updated network meta-analysis comparing the efficacy and safety of ARNI, ACE-I, ARB, and placebo in heart failure with reduced ejection fraction. We included randomized clinical trials that compared ARNI, ARB, ACE-I, and placebo in heart failure with reduced ejection fraction. We extracted prespecified efficacy end points and produced network estimates, p scores, and surface under the cumulative ranking curve scores using frequentist and Bayesian network meta-analysis approaches. A total of 28 randomized controlled trials including 47,407 patients were included. ARNI was associated with lower risk of all-cause mortality (relative risk [RR] 0.81, 95% confidence interval [CI] 0.68 to 0.96), cardiac death (RR 0.79, 95% CI 0.64 to 0.99), and major adverse cardiac events (MACEs; RR 0.83, 95% CI 0.72 to 0.97) but higher risk of hypotension (RR 1.46, 95% CI 1.02 to 2.10) than ARB. ARNI was associated with lower risk of MACE (RR 0.85, 95% CI 0.74 to 0.97), but higher risk of hypotension (RR 1.69, 95% CI 1.27 to 2.24) compared with ACE-I. P scores and surface under the cumulative ranking curve scores demonstrated superiority of ARNI over ARB and ACE-I in all-cause mortality, cardiac death, MACE, and hospitalization for heart failure. In conclusion, ARNI was associated with improved clinical outcomes, except for higher risk of hypotension, compared with ARB and ACE-I.

Peripheral Perfusion Index: A Predictor of Post-Spinal Hypotension in Caesarean Section.

BackgroundEarly prediction of hypotension helps to decide appropriate prophylactic measures and, hence, safe anaesthesia for mothers and improved neonatal outcomes. Perfusion index (PI) measured from a standard pulse oximeter has shown positive results in the prediction of hypotension. This study aims to determine if PI can equally predict hypotension in parturients after administration of spinal anaesthesia at different time points.MethodsParturients posted for elective caesarean section belonging to the American Society of Anesthesiology II (ASA II) were divided into two groups based on baseline PI as group A <3.5 and group B ≥3.5. Fifty-six parturients were enrolled in the study. PI and blood pressure were monitored at baseline, every two minutes for 12 minutes and every five minutes until the end of the surgery, after administration of spinal anaesthesia with hyperbaric bupivacaine 10 mg. Incidence of hypotension was compared between groups at all time points of observation. Spearman’s rank correlation coefficient was determined to check the correlation between baseline PI and the number of episodes of hypotension. Receiver operating characteristic (ROC) curve was plotted to determine the ideal cut-off at different time points.ResultsBaseline PI significantly correlated with the number of episodes of hypotension (r-0.525). The overall incidence of hypotension was significantly higher in parturients with baseline PI ≥3.5 (79.16%) as compared to those with PI <3.5 (33.33%). The incidence of hypotension at sixth, 10th and 37th minutes post-spinal anaesthesia administration was significantly higher in the group with PI ≥3.5. The sensitivity and specificity for the 3.5 cut-off of PI were 85.7% and 60%, respectively, at the 6th and 10th minute after spinal administration. A higher cut-off of 3.9 increases the specificity to 69% without much change in the sensitivity.Conclusion Parturients with PI >3.9 at baseline have a higher risk of hypotension in the initial 10-12 minutes following spinal anaesthesia during caesarean delivery.

Optimum dose of spinal ropivacaine with or without single intravenous bolus of S-ketamine during elective cesarean delivery: a randomized, double-blind, sequential dose-finding study

BackgroundMaternal hypotension after spinal anaesthesia occurs at a high rate during caesarean delivery and can lead to adverse maternal or foetal outcomes. The aim of this study was to determine the optimal dose of spinal ropivacaine for caesarean section with or without intravenous single bolus of S-ketamine and to observe the rates of hypotension associated with both methods.MethodsEighty women undergoing elective caesarean delivery were randomly allocated into either a ropivacaine only or ropivacaine with intravenous S-ketamine group. If the upper sensory level of the patient reached T6 and the visual analogue scale (VAS) scores remained below 3 points before delivery, the next patient had a 1/9th chance of receiving a lower dose or an 8/9th chance of receiving the same dose as the previous patient. If the patient had VAS scores of more than 2 points or needed an extra epidural rescue bolus before delivery, a higher dose was used for the next patient. The primary outcome was the successful use of spinal ropivacaine to maintain patient VAS score of < 3 points before delivery and the incidence of post-spinal hypotension in both groups. Secondary outcomes included the rates of hypotension-related symptoms and interventions, upper sensory level of anaesthesia, level of sedation, neonatal outcomes, Edinburgh Postnatal Depression Scale scores at admission and discharge, and post-operative analgesic effect. The 90% effective dose (ED90) and 95% confidence interval (95% CI) were estimated by isotonic regression.ResultsThe estimated ED90 of ropivacaine was 11.8 mg (95% CI: 11.7–12.7) with and 14.7 mg (95% CI: 14.6–16.0) without intravenous S-ketamine, using biased coin up-down sequential dose-finding method. The rates of hypotension and associated symptoms were significantly lower in S-ketamine group than in the ropivacaine only group.ConclusionsA spinal dose of ropivacaine 12 mg with a single intravenous 0.15 mg/kg bolus dose of S-ketamine may significantly reduce the risk of hypotension and induce sedation before delivery. This method may be used with appropriate caution for women undergoing elective caesarean delivery and at a high risk of hypotension or experiencing extreme nervousness.Trial registrationhttp://www.chictr.org.cn (ChiCTR2000040375; 28/11/2020).

Abstract P336: Efficacy and Safety of Vasodilator Beta-Blocker in Elderly Hypertensive Patients: Result From BEFIT-KOERA Study

Purpose: Beta-blockers are efficacious in young hypertensive patients with sympathetic activation. Elderly patients have been known to be at higher risk of hypotension, bradycardia, and other side-effects of beta-blockers when compared with younger patients. This study was to evaluate efficacy and safety of vasodilator beta-blocker in elderly hypertensive patients. Methods: BENEFIT-KOREA study (BEnefits after 24 weeks of NEbivolol administration For essential hypertensIon patients wiTh various co-morbidities and treatment environments in KOREA) was a open labeled non-controlled, prospective, multicenter observational study enrolled total 3,140 subjects [1,871 male(59.6%), mean age=63.5±12.9 years old]. We evaluated efficacy and safety of vasodilator beta-blocker in elderly patients. Results: Subjects of more than 65 years old [n=1,655, 839 male (49.3%), mean age=73.6±5.8] were analyzed. Table shows that vasodilator beta-blocker is effective in reduction of blood pressure, mean arterial pressure and pulse pressure in elderly patients regardless of add-on or switched to beta-blocker. Adverse drug reaction rate was not different between age group (n=19, 1.15% vs. n=17, 1.15%). Table shows lipid profile and body mass index were not aggravated after 24-week treatment of vasodilator beta-blocker. Conclusion: Vasodilator beta-blocker is efficacious and safe without metabolic derangement in elderly patients regardless of prescription patterns. These drug effects in elderly are comparable to in younger patients.

Effect of Dialysis Day on Intradialytic Hypotension Risk

Background/Aims: Intradialytic hypotension (IDH) is a serious and frequent complication of hemodialysis (HD). Thus far, data are scarcely available to assess the impact of first versus subsequent HD sessions of the week in IDH. Therefore, the purpose of this work was to evaluate IDH risk in patients on thrice-weekly HD. Methods: We conducted an analysis of all blood pressure (BP) measurements obtained during 492 HD treatments given to 41 prevalent adult patients over a one month period. A logistic regression model for repeated binary observations was used to determine the association between hypotension and patient and dialysis factors. Results: The incidence of IDH was 32.5%. First dialysis session of the week was associated with a 9% higher risk of hypotension relatively to the second one. The risk was even higher from the first to the third session of the week (60%) and from the second to the third (50%). A higher hypotension odds ratio was also associated with age (1.03, 90%CI: 1.01-1.06), higher predialysis BP (1.04, 90%CI: 1.03-1.05) and higher phosphorus level (1.38, 90%CI: 1.07-1.76). The risk decreased 24.4% for each additional antihypertensive drug taken by the patient. Conclusions: The odds of hypotension occurrence decrease throughout dialysis sessions of the week. Minimizing modifiable risk factors may decrease IDH episodes.

Non-invasive haemodynamic measurements with Nexfin predict the risk of hypotension following spinal anaesthesia.

Unfavourable circulatory system conditions have been observed in many patients with spinal anaesthesia. The most frequent symptoms include a decrease in blood pressure and, less frequently, bradycardia. The appearance of unfavourable consequences of spinal anaesthesia might be related to the initial status of the patient's circulatory system. The aim of this study was to establish the possibility of predicting unfavourable circulatory consequences (hypotension, bradycardia) following spinal anaesthesia, based on non-invasive haemodynamic assessment with a Nexfin device. This prospective study included 100 18-60-year-old ASA I or II planned spinal anaesthesia patients. The initial hemodynamic parameters were assessed with a Nexfin monitor. Anaesthesia was performed with 3-3.5 mL of a 0,5% hyperbaric bupivacaine solution. Within 20 min after the administration of anaesthesia, the arterial blood pressure values, heart rate, sensory blockade level, and motoric blockade level were recorded in 5-min intervals. Hypotension was classified by a decrease of SAP < 90 mm Hg and/or the decrease of the SAP ≥ 20% initial value. Logistic regression was used to determine the independent predictors of hypotension resulting from a spinal blockade. The development of hypotension and bradycardia was observed in 39 and 2%, respectively, of the patients. The patients who developed hypotension differed significantly from those who did not develop this symptom, with the main difference being the body mass and the assessment on the ASA scale. The patients who developed hypotension after spinal anaesthesia differed significantly in the initial hemodynamic parameters (SAP, MAP, SVRI). The following two independent risk factors for hypotension were isolated: the mean arterial pressure (OR 1.04; 95% CI: 1.005-1.076) and the systemic vascular resistance index (OR 1.109; 95% CI: 1.021-1.204). Nexfin-based non-invasive haemodynamic monitoring might be helpful in the identification of individuals with a high risk of hypotension following spinal blockade.

Moving away from benzodiazepine as a primary sedative in the intensive care unit; is clonidine a viable alternative?

Current pain, agitation, and delirium (PAD) guidelines endorse a benzodiazepine-sparing approach to aid in achieving optimal patient outcomes.[1] Several benzo-sparing strategies, including protocolized and frequent pain, sedation and delirium assessments, achieving the goal of awake and alert, utilization of bolus and symptom-triggered, patient-specific pharmacotherapy, interruption of sedatives, a pain-first approach or analagosedation, early mobilization, rotation of medications, and adjustment of ventilator settings are nonmedication specific principles shown to improve clinical outcomes in mechanically ventilated (MV), intensive care unit (ICU) patients. These techniques and strategies have been associated with some of the most relevant clinical outcomes including a decrease in discomfort, ventilator-associated pneumonia, length of MV, and ICU and hospital length of stay.[2,3] Interestingly, extremely few well-conducted sedative versus sedative trials show improvements in these hard clinical outcomes. Dexmedetomidine is an effective agent for PAD management and a viable alternative to benzodiazepine therapy. Dexmedetomidine maintains a light level of sedation, while minimizing the deep sedation commonly seen with benzodiazepines. In randomized, controlled trials, dexmedetomidine has been associated with shorter duration of delirium and MV compared to benzodiazepine infusion, specifically midazolam.[4] It should be noted, however, that these trials showing a reduction in MV duration are not without criticism. For example, the mean dose of midazolam in the SEDCOM trial was approximately 5 mg/h (based on the average patient weight of 88 kg); an extremely high dose by clinical standards when the goal is to keep a patient awake and alert.[5] Dexmedetomidine is relatively safe with fairly predictable cardiovascular (CV) effects (most frequently hypotension and bradycardia). These CV risks can often be mitigated by avoiding the use of bolus therapy and extending titration intervals to no more frequently than every 30 min.[6] The cost of dexmedetomidine is often a concern in many parts of the world. There are several strategies to address the cost of dexmedetomidine including use of alternative medication or by following restrictive institution specific guidelines. A recent publication on dexmedetomidine stewardship showed an institution's approach to managing the benefits of the drug versus the cost. The guideline followed in this analysis supports judicious use of dexmedetomidine in patients who fail traditional therapy.[7] Another important note in terms of cost is in certain parts of the world dexmedetomidine will lose its patent in the near future and is likely going to be price reduced. We commend the investigators for their fine analysis entitled “comparison of clonidine and dexmedetomidine for short term sedation of ICU patients” published in this month's journal.[8] This trial examined the efficacy and safety of clonidine as an alternative to dexmedetomidine in MV patients. The authors conclude both agents are effective, although clonidine is associated with a higher risk of hypotension. This paper adds to the literature suggesting clonidine may be a useful medication for PAD management although further investigation is needed to confirm these findings. We support the author's conclusion although we think there are some key critiques of this analysis. (1) The authors assessed and titrated to Ramsay Sedation Score (RSS) but pain and delirium assessment scores were not reported. Therefore, it is hard to tell if the pain-first approach was employed prior to the use of either sedative. (2) The goal RSS in this trial was 3-4 yet an RSS of 5, corresponding to awake and alert, may have been a more appropriate goal and these patients may have been more deeply sedated than would be desired in clinical practice. (3) Dexmedetomidine performed better statistically than clonidine, therefore lumping them both as effective may be slightly misleading. It is also important to note that the relatively high incidence of hypotension in the clonidine arm is concerning. A recent trial published on clonidine in noncardiac surgery patients highlights safety concerns with a troubling increase in clinically important hypotension and nonfatal cardiac arrest.[9] Although a different patient population than this study, when combined with the results of this analysis it raises concerns about the safety of this medication. The current analysis should be considered hypothesis generating and clonidine should be further investigated before it is systematically used for management of PAD.

Pediatric CT Sedation: Comparison of Dexmedetomidine and Pentobarbital

Our institution replaced pentobarbital with dexmedetomidine for pediatric CT sedation. The purpose of this study was to compare the efficacy, incidence of adverse events, and cardiovascular and respiratory profiles of these two sedatives. Quality assurance data were accessed for a review of demographics, outcome parameters, and adverse events among all children who received either pentobarbital or dexmedetomidine. From January 2004 through June 2009 there were 388 pentobarbital sedations and 1,274 dexmedetomidine sedations. Age, sex, weight, and duration of imaging study were similar in the two groups. Average time to achieve sedation was 12 ± 4 minutes with dexmedetomidine and 6 ± 3 minutes with pentobarbital (p < 0.001). Recovery time was 32 ± 18 minutes with dexmedetomidine and 95 ± 28 minutes with pentobarbital (p < 0.001). There were no differences between groups in incidence of oxygen desaturation and need for brief positive pressure ventilation. The odds of needing additional sedative agents to complete the study were significantly higher with pentobarbital than with dexmedetomidine (odds ratio, 4.0; 95% CI, 2.0-8.4; p < 0.001). There was a significantly lower incidence of agitation and rage with dexmedetomidine (p < 0.01) but higher risk of hypotension (p < 0.01). There was one failed sedation in each group (p = 0.99). Dexmedetomidine is a safe and effective alternative to pentobarbital for pediatric CT, being associated with a much shorter recovery time and less need for adjuvant sedatives.

Use of Dexmedetomidine for Primary Sedation in a General Intensive Care Unit

Use of Dexmedetomidine for Primary Sedation in a General Intensive Care Unit

Predicting hypotensive episodes during spinal anesthesia with the application of artificial neural networks

Hypotension is one of the most frequent adverse effects of spinal anesthesia. Several factors might be related to the occurrence of hypotension. Predictions of the hypotensive event, however, had been addressed by only a few authors using logistic regression (LR) models. Artificial neural networks (ANN) are pattern-recognition tools that can be used to detect complex patterns within data sets. The purpose of this study was to develop the ANN-based predictive model to identify patients with high risk of hypotension during spinal anesthesia. From September 2004 to December 2006, the anesthesia records of 1501 patients receiving surgery under spinal anesthesia were used to develop the ANN and LR models. By random selection 75% of data were used for training and the remaining 25% of data were used as test set for validating the predictive performance. Five senior anesthesiologists were asked to review the data of test set and to make predictions of hypotensive event during spinal anesthesia by clinical experience. The ANN model had a sensitivity of 75.9% and specificity of 76.0%. The LR model had a sensitivity of 68.1% and specificity of 73.5%. The area under receiver operating characteristic curves were 0.796 and 0.748. The ANN model performed significantly better than the LR model. The prediction of clinicians had the lowest sensitivity of 28.7%, 22.2%, 21.3%, 16.1%, and 36.1%, and specificity of 76.8%, 84.3%, 83.1%, 87.0%, and 64.0%. The computer-based predictive model should be useful in increasing vigilance in those patients most at risk for hypotension during spinal anesthesia, in allowing for patient-specific therapeutic intervention, or even in suggesting the use of alternative methods of anesthesia.

Influence of Stent Type on Hemodynamic Depression after Carotid Artery Stent Placement

To assess the effect of stent type on hypotension and bradycardia after carotid artery stent placement. A retrospective analysis on a prospectively maintained database was conducted in 256 patients (126 men; mean age, 71.8 years +/- 8.6; 194 de novo lesions) undergoing carotid artery stent placement between January 1996 and January 2007 by using self-expanding stents. Braided Elgiloy stents (Wallstents) were used in 44 of the 256 patients (17.2%) and slotted-tube nitinol stents were deployed in 212 (82.8%). Bivariate and multivariable logistic regression models were used to determine the influence of stent design on procedural and 24-hour hypotension and bradycardia. Procedural hemodynamic depression (HD) was encountered in 73 of the 256 patients (28.5%) due to hypotension in 24 (9.4%), bradycardia in 12 (4.7%), or both in 37 (14.5%) patients. Rates of procedural hypotension were 11.3% with nitinol stents and 0% with braided Elgiloy stents (P = .0188). Persistent postprocedural HD occurred in 91 of the 256 patients (35.5%) due to hypotension in 40 patients (15.6%), bradycardia in 23 (9.0%), or both in 28 (10.9%). Within a multivariable analysis adjusted for clinically relevant factors affecting rates of HD, the use of braided Elgiloy stents was associated with a decreased rate of procedural hypotension (odds ratio: 0.165; 95% confidence interval: 0.038, 0.721; P = .017). Procedural hypotension and bradycardia were not correlated to incidence of major adverse events but were associated with an increased duration of hospital stay (P = .0059 and P = .0335, respectively). Nitinol stents are associated with a higher risk of hypotension as compared to braided Elgiloy stents during carotid artery stent placement.

Can heart rate variability become a screening tool for anesthesia-related hypotension?

H EART rate variability (HRV) analysis as a diagnostic tool has been available for decades (1), and many have also learned about modern HRV analysis as a predictive or prognostic instrument for cardiological patients with diagnoses such as congestive heart failure or post-myocardial infarction (2). Numerous recent publications in the field of anesthesiology have presented findings concerning HRV as a potential tool for predicting acute circulatory disturbances, and particularly hypotension (3–11). As all in the field of anesthesiology and critical care medicine traditionally have in mind a central clinical theme to ‘avoid hypotension and hypoxia’ in all perioperative patients, it is relevant for the specialty to carefully study and try to establish validity for any diagnostic instruments which show promise in predicting circulatory disturbances, including hypotension. In this (12) and the previous issue (13) of Acta Anaesthesiologica Scandinavica, two studies are presented where HRV analysis is examined as a possible screening tool for anesthesia-related hypotension (12, 13). Both studies present findings where a preoperative HRV finding was associated with more hypotension during spinal anesthesia. The study by Hanss et al. (12) is a continuation in a series of studies in obstetrical patients, where they have systematically tested HRV parameters in relation to different parts of the peri-operative procedure in a highly selected patient group which is at high risk of hypotension. The study by Fujuwara et al. (13) includes use of a HRV analysis method which has different characteristics from the more commonly used fast Fourier transformation (FFT) method. Both studies provide information and experience which contribute to the process of evaluation and validation of HRV as a clinical tool for assessment of perioperative patients. The few studies published so far where HRV has been applied to predict hypotension can be regarded as preliminary studies within a new research area. Can hypotension during spinal anesthesia or other types of anesthesia be predicted from patterns in HRV? Moreover, is increased low frequency (LF) to high frequency HF power spectrum density ratio (LF/HF) a marker of an increased risk of hypotension, which is suggested by the findings in both studies in this issue? Is increased LF/HF caused by increased sympathetic activity, or is it mainly caused by reduced vagal outflow? Fujiwara et al. (13) also found that subjects with a low degree of randomness in their HRV seemed to be more susceptible to decreased blood pressure after spinal anesthesia. Although not specifically discussed in the paper, these subjects also had relatively low values of both LF and HF power, which was presented as absolute values. The latter finding could also indicate reduced vagal outflow in this subgroup. HRV results in this clinical anesthesia context are difficult to interpret because of several problems, some new, and some not so new (14). First, it is not clear exactly which phenomena in the body that HRV is measuring. Second, so far there are no findings to help to understand whether HRV is more useful in predicting hypotension then other already readily available (and much simpler) parameters. Including, for example, resting heart rate before spinal anesthesia. Third, some of the methodology is difficult to examine and understand. The first and perhaps most important issue concerns exactly which physiological or pathophysiological process HRV is assessing. Regulation of heart

Heart Rate Variability–guided Prophylactic Treatment of Severe Hypotension after Subarachnoid Block for Elective Cesarean Delivery

Baseline low-to-high frequency ratio (LF/HF) of heart rate variability predicted hypotension after subarachnoid block (SAB). LF/HF-guided treatment of hypotension with vasopressors or colloids was investigated. In 80 women scheduled to undergo cesarean delivery during SAB, LF/HF and systolic blood pressure (SBP) were analyzed. Patients were randomly assigned to a control group (n = 40) or a treatment group (n = 40). Control patients were assigned by their baseline LF/HF to one of two subgroups: LF/HF less than 2.5 or LF/HF greater than 2.5. Treatment patients with baseline LF/HF greater than 2.5 were treated with vasopressor infusion right after SAB (n = 20) or colloid prehydration until LF/HF decreased below 2.5 (n = 20). The incidences of hypotension (SBP < 80 mmHg) and hypertension (SBP > 140 mmHg) were investigated. LF/HF is presented as median and range, and SBP is presented as mean +/- SD. Three of 17 control patients with low baseline LF/HF (1.7 [1.3/1.8]) demonstrated hypotension, and mean SBP remained stable (lowest SBP = 105 +/- 14 mmHg). In contrast, 20 of 23 control patients with high baseline LF/HF (3.8 [3.3/4.8]; P < 0.0001 vs. low baseline LF/HF) demonstrated hypotension after SAB: lowest SBP = 78 +/- 15 mmHg (P < 0.0001 vs. lowest SBP of control group with low baseline LF/HF). LF/HF-guided vasopressor therapy prevented hypotension in 19 of 20 patients: baseline SBP = 123 +/- 15 mmHg, lowest SBP = 116 +/- 17 mmHg. Mean prophylactic colloid infusion of 1,275 +/- 250 ml reduced elevated baseline LF/HF from 5.4 (4.1/7.5) to 1.3 (0.8/1.59) (P < 0.0001). Hypotension was prevented in 17 of 20 patients: baseline SBP = 115 +/- 13 mmHg, lowest SBP = 104 +/- 19 mmHg. No hypertensive episode was recognized. LF/HF may be a tool to guide prophylactic therapy of patients at high risk for hypotension after SAB. Vasopressor therapy tended to be more effective compared with colloid prehydration.

Fast Fourier Transforms as Prophecy

Fast Fourier Transforms as Prophecy

A Regression Model for Identifying Patients at High Risk of Hypotension, Bradycardia and Nausea During Spinal Anesthesia

Tampere University and Departments of Clinical and Biomedical Science, Tampere University, Tampere, Finland