Alberto A. Uribe

Pulse oximetry-derived respiratory rate in general care floor patients

Respiratory rate is recognized as a clinically important parameter for monitoring respiratory status on the general care floor (GCF). Currently, intermittent manual assessment of respiratory rate is the standard of care on the GCF. This technique has several clinically-relevant shortcomings, including the following: (1) it is not a continuous measurement, (2) it is prone to observer error, and (3) it is inefficient for the clinical staff. We report here on an algorithm designed to meet clinical needs by providing respiratory rate through a standard pulse oximeter. Finger photoplethysmograms were collected from a cohort of 63 GCF patients monitored during free breathing over a 25-min period. These were processed using a novel in-house algorithm based on continuous wavelet-transform technology within an infrastructure incorporating confidence-based averaging and logical decision-making processes. The computed oximeter respiratory rates (RRoxi) were compared to an end-tidal CO2 reference rate (RRETCO2). RRETCO2 ranged from a lowest recorded value of 4.7 breaths per minute (brpm) to a highest value of 32.0 brpm. The mean respiratory rate was 16.3 brpm with standard deviation of 4.7 brpm. Excellent agreement was found between RRoxi and RRETCO2, with a mean difference of −0.48 brpm and standard deviation of 1.77 brpm. These data demonstrate that our novel respiratory rate algorithm is a potentially viable method of monitoring respiratory rate in GCF patients. This technology provides the means to facilitate continuous monitoring of respiratory rate, coupled with arterial oxygen saturation and pulse rate, using a single non-invasive sensor in low acuity settings.

The effect of transdermal scopolamine for the prevention of postoperative nausea and vomiting.

Postoperative nausea and vomiting (PONV) is one of the most common and undesirable complaints recorded in as many as 70–80% of high-risk surgical patients. The current prophylactic therapy recommendations for PONV management stated in the Society of Ambulatory Anesthesia (SAMBA) guidelines should start with monotherapy and patients at moderate to high risk, a combination of antiemetic medication should be considered. Consequently, if rescue medication is required, the antiemetic drug chosen should be from a different therapeutic class and administration mode than the drug used for prophylaxis. The guidelines restrict the use of dexamethasone, transdermal scopolamine, aprepitant, and palonosetron as rescue medication 6 h after surgery. In an effort to find a safer and reliable therapy for PONV, new drugs with antiemetic properties and minimal side effects are needed, and scopolamine may be considered an effective alternative. Scopolamine is a belladonna alkaloid, α-(hydroxymethyl) benzene acetic acid 9-methyl-3-oxa-9-azatricyclo non-7-yl ester, acting as a non-selective muscarinic antagonist and producing both peripheral antimuscarinic and central sedative, antiemetic, and amnestic effects. The empirical formula is C17H21NO4 and its structural formula is a tertiary amine L-(2)-scopolamine (tropic acid ester with scopine; MW = 303.4). Scopolamine became the first drug commercially available as a transdermal therapeutic system used for extended continuous drug delivery during 72 h. Clinical trials with transdermal scopolamine have consistently demonstrated its safety and efficacy in PONV. Thus, scopolamine is a promising candidate for the management of PONV in adults as a first line monotherapy or in combination with other drugs. In addition, transdermal scopolamine might be helpful in preventing postoperative discharge nausea and vomiting owing to its long-lasting clinical effects.

Aprepitant versus ondansetron in preoperative triple-therapy treatment of nausea and vomiting in neurosurgery patients: study protocol for a randomized controlled trial.

BackgroundThe incidence of postoperative nausea and vomiting (PONV) is 50% to 80% after neurosurgery. The common prophylactic treatment for postoperative nausea and vomiting is a triple therapy of droperidol, promethazine and dexamethasone. Newer, more effectives methods of prophylaxis are being investigated. We designed this prospective, double-blind, single-center study to compare the efficacy of ondansetron, a neurokinin-1 antagonist, and aprepitant, as a substitute for droperidol, in the prophylactic treatment of postoperative nausea and vomiting after neurosurgery.MethodsAfter obtaining institutional review board approval; 176 patients, 18 to 85 years of age with American Society of Anesthesiologists (ASA) classifications I to III, who did not receive antiemetics 24 h before surgery and were expected to undergo general anesthesia for neurosurgery lasting longer than 2 h were included in this study. After meeting the inclusion and exclusion criteria and providing written informed consent, patients were randomly assigned in a 1:1 ratio to one of two treatment groups: aprepitant or ondansetron. The objective of this study was to conduct a randomized, double-blind, double-dummy, parallel-group and single-center trial to compare and evaluate the efficacies of aprepitant versus ondansetron. Patients received oral aprepitant 40 mg OR oral dummy pill within 2 h prior to induction. At induction, a combination of intravenous dexamethasone 10 mg, promethazine 25 mg, and ondansetron 4 mg OR dummy injection was administered. Therefore, all patients received one dummy treatment and three active PONV prophylactic medications: dexamethasone 10 mg, promethazine 25 mg, and either aprepitant 40 mg OR ondansetron 4 mg infusion. The primary outcome measures were the episodes and severity of nausea and vomiting; administration of rescue antiemetic; and opioid consumption for 120 h postoperatively. Standard safety assessments included adverse event reports, physical and laboratory data, awakening time and duration of recovery from anesthesia.DiscussionThe results of this comparative study could potentially identify an improved treatment regimen that may decrease the incidence and severity of postoperative nausea and vomiting in patients undergoing neurosurgery. Also, this will serve to enhance patient recovery and overall satisfaction of neurosurgical patients in the immediate postoperative period.Trial registrationRegistered at The Ohio State University Biomedical Sciences Institutional Review Board: Protocol Number: 2007 H0053

Alternative Therapies for the Prevention of Postoperative Nausea and Vomiting

Postoperative nausea and vomiting (PONV) is a complication affecting between 20 and 40% of all surgery patients, with high-risk patients experiencing rates of up to 80%. Recent studies and publications have shed light on the uses of alternative treatment for PONV through their modulation of endogenous opioid neuropeptides and neurokinin ligands. In addition to reducing PONV, hypnosis was reported to be useful in attenuating postoperative pain and anxiety, and contributing to hemodynamic stability. Music therapy has been utilized to deepen the sedation level and decrease patient anxiety, antiemetic and analgesic requirements, hospital length of stay, and fatigue. Isopropyl alcohol and peppermint oil aromatherapy have both been used to reduce postoperative nausea. With correct training in traditional Chinese healing techniques, acupuncture (APu) at the P6 acupoint has also been shown to be useful in preventing early PONV, postdischarge nausea and vomiting, and alleviating of pain. Electro-acupuncture (EAPu), as with APu, provided analgesic and antiemetic effects through release and modulation of opioid neuropeptides. These non-pharmacological modalities of treatment contribute to an overall patient wellbeing, assisting in physical and emotional healing.

Multicenter Study Validating Accuracy of a Continuous Respiratory Rate Measurement Derived From Pulse Oximetry: A Comparison With Capnography.

BACKGROUND: Intermittent measurement of respiratory rate via observation is routine in many patient care settings. This approach has several inherent limitations that diminish the clinical utility of these measurements because it is intermittent, susceptible to human error, and requires clinical resources. As an alternative, a software application that derives continuous respiratory rate measurement from a standard pulse oximeter has been developed. We sought to determine the performance characteristics of this new technology by comparison with clinician-reviewed capnography waveforms in both healthy subjects and hospitalized patients in a low-acuity care setting. METHODS: Two independent observational studies were conducted to validate the performance of the Medtronic NellcorTM Respiration Rate Software application. One study enrolled 26 healthy volunteer subjects in a clinical laboratory, and a second multicenter study enrolled 53 hospitalized patients. During a 30-minute study period taking place while participants were breathing spontaneously, pulse oximeter and nasal/oral capnography waveforms were collected. Pulse oximeter waveforms were processed to determine respiratory rate via the Medtronic Nellcor Respiration Rate Software. Capnography waveforms reviewed by a clinician were used to determine the reference respiratory rate. RESULTS: A total of 23,243 paired observations between the pulse oximeter-derived respiratory rate and the capnography reference method were collected and examined. The mean reference-based respiratory rate was 15.3 ± 4.3 breaths per minute with a range of 4 to 34 breaths per minute. The Pearson correlation coefficient between the Medtronic Nellcor Respiration Rate Software values and the capnography reference respiratory rate is reported as a linear correlation, R, as 0.92 ± 0.02 (P < .001), whereas Lin’s concordance correlation coefficient indicates an overall agreement of 0.85 ± 0.04 (95% confidence interval [CI] +0.76; +0.93) (healthy volunteers: 0.94 ± 0.02 [95% CI +0.91; +0.97]; hospitalized patients: 0.80 ± 0.06 [95% CI +0.68; +0.92]). The mean bias of the Medtronic Nellcor Respiration Rate Software was 0.18 breaths per minute with a precision (SD) of 1.65 breaths per minute (healthy volunteers: 0.37 ± 0.78 [95% limits of agreement: –1.16; +1.90] breaths per minute; hospitalized patients: 0.07 ± 1.99 [95% limits of agreement: –3.84; +3.97] breaths per minute). The root mean square deviation was 1.35 breaths per minute (healthy volunteers: 0.81; hospitalized patients: 1.60). CONCLUSIONS: These data demonstrate the performance of the Medtronic Nellcor Respiration Rate Software in healthy subjects and patients hospitalized in a low-acuity care setting when compared with clinician-reviewed capnography. The observed performance of this technology suggests that it may be a useful adjunct to continuous pulse oximetry monitoring by providing continuous respiratory rate measurements. The potential patient safety benefit of using combined continuous pulse oximetry and respiratory rate monitoring warrants assessment.

Calculation of the Respiratory Modulation of the Photoplethysmogram (DPOP) Incorporating a Correction for Low Perfusion

DPOP quantifies respiratory modulations in the photoplethysmogram. It has been proposed as a noninvasive surrogate for pulse pressure variation (PPV) used in the prediction of the response to volume expansion in hypovolemic patients. The correlation between DPOP and PPV may degrade due to low perfusion effects. We implemented an automated DPOP algorithm with an optional correction for low perfusion. These two algorithm variants (DPOPa and DPOPb) were tested on data from 20 mechanically ventilated OR patients split into a benign “stable region” subset and a whole record “global set.” Strong correlation was found between DPOP and PPV for both algorithms when applied to the stable data set: R = 0.83/0.85 for DPOPa/DPOPb. However, a marked improvement was found when applying the low perfusion correction to the global data set: R = 0.47/0.73 for DPOPa/DPOPb. Sensitivities, Specificities, and AUCs were 0.86, 0.70, and 0.88 for DPOPa/stable region; 0.89, 0.82, and 0.92 for DPOPb/stable region; 0.81, 0.61, and 0.73 for DPOPa/global region; 0.83, 0.76, and 0.86 for DPOPb/global region. An improvement was found in all results across both data sets when using the DPOPb algorithm. Further, DPOPb showed marked improvements, both in terms of its values, and correlation with PPV, for signals exhibiting low percent modulations.

Triple Therapy with Scopolamine, Ondansetron, and Dexamethasone for Prevention of Postoperative Nausea and Vomiting in Moderate to High-Risk Patients Undergoing Craniotomy Under General Anesthesia: A Pilot Study.

Introduction Postoperative nausea and vomiting (PONV) is one of the most common complaints from patients and clinicians after a surgical procedure. According to the current Society of Ambulatory Anesthesia Consensus Guidelines, the general incidence of vomiting and nausea is around 30 and 50%, respectively; and up to 80% in high-risk patients. In previous studies, the reported incidence of PONV at 24 h after craniotomy was 43–70%. The transdermal scopolamine (TDS) delivery system contains a 1.5-mg drug reservoir, which is designed to deliver a continuous slow release of scopolamine through intact skin during the first 72 h of patch application. Therefore, we designed this single arm, non-randomized, pilot study to assess the efficacy and safety of triple therapy with scopolamine, ondansetron, and dexamethasone to prevent PONV. Materials and methods In the preoperative area, subjects received an active TDS 1.5 mg that was applied to a hairless patch of skin in the mastoid area approximately 2 h prior to the operation. Immediately after anesthesia induction, all patients received a single 4 mg dose of ondansetron IV and a single 10 mg dose of dexamethasone IV. Patients who experienced nausea and/or vomiting received ondansetron 4 mg IV as the initial rescue medication. Postoperative nausea and vomiting assessments were performed for up to 120 h after surgery. Results A total of 36 subjects were analyzed. The overall incidence of PONV during the first 24 h after neurological surgery was 33% (n = 12). The incidence of nausea and emesis during the first 24 h after surgery was recorded as 33% (n = 12) and 16% (n = 6), respectively. Conclusion Our data showed that this triple therapy regimen may be an efficient alternative regimen for PONV prophylaxis in patients undergoing neurological surgery with general anesthesia. Further studies using regimens affecting different receptor pathways should be performed to better prove the efficacy and safety in the prevention or delay of PONV.

On Better Estimating and Normalizing the Relationship between Clinical Parameters: Comparing Respiratory Modulations in the Photoplethysmogram and Blood Pressure Signal (DPOP versus PPV)

DPOP (ΔPOP or Delta-POP) is a noninvasive parameter which measures the strength of respiratory modulations present in the pulse oximeter waveform. It has been proposed as a noninvasive alternative to pulse pressure variation (PPV) used in the prediction of the response to volume expansion in hypovolemic patients. We considered a number of simple techniques for better determining the underlying relationship between the two parameters. It was shown numerically that baseline-induced signal errors were asymmetric in nature, which corresponded to observation, and we proposed a method which combines a least-median-of-squares estimator with the requirement that the relationship passes through the origin (the LMSO method). We further developed a method of normalization of the parameters through rescaling DPOP using the inverse gradient of the linear fitted relationship. We propose that this normalization method (LMSO-N) is applicable to the matching of a wide range of clinical parameters. It is also generally applicable to the self-normalizing of parameters whose behaviour may change slightly due to algorithmic improvements.

Studying the Effectiveness of Triple Therapy with Palonosetron,Dexamethasone and Promethazine for Prevention of Post OperativeNausea and Vomiting in High Risk Patients Undergoing NeurologicalSurgery and General Anesthesia

Post operative nausea and vomiting (PONV) occurs in as many as 70%-80% of high risk surgical patients. The latest prophylactic treatment recommended in the Society of Ambulatory Anesthesia Guidelines for the management of Postoperative Nausea and Vomiting for high risk patients is a combination of 2 or more interventions (multimodal therapy). A combination of a 5-HT3 receptor antagonist with dexamethasone and/or droperidol, or a 5-HT3 receptor antagonist with droperidol alone, or dexamethasone with droperidol, have been the pharmacologic combination therapies suggested in these guidelines. Palonosetron is a fairly new 5-HT3 receptor antagonist recently approved by the FDA for PONV prophylaxis. The use of this novel drug in a triple therapy combination with Dexamethasone and/ or Droperidol could be an effective treatment for the prevention of PONV. However, since the FDA issued a warning stating that droperidol may cause life – threatening arrhythmias as well as a prolongation of the QTc interval, the need to discover new combination therapies for PONV prevention in high risk patients is still in demand. Therefore, we hypothesize that the use of this novel drug Palonosetron in a triple therapy combination with Dexamethasone and Promethazine will be an effective treatment for the prevention of PONV in patients at a high risk for developing PONV during the first 120 hours after neurosurgery.

Studying the Effectiveness of Triple Therapy with Scopolamine, Ondansetron and Dexamethasone for Prevention of Post Operative Nausea and Vomiting in High Risk Patients Undergoing Neurological Surgery and General Anesthesia

Post operative nausea and vomiting (PONV) are common complications and occurs in as many as 70%- 80% of high risk surgical patients. The latest prophylactic treatment recommended in the Society of Ambulatory Anesthesia Guidelines (SAMBA) for the management of Post operative Nausea and Vomiting for high risk patients is a combination of 2 or more interventions (multimodal therapy). A combination of a 5-HT3 receptor antagonist with Dexamethasone and/or Droperidol, or a 5-HT3 receptor antagonist with Droperidol alone, or Dexamethasone with Droperidol, have been the pharmacologic combination therapies suggested in these guidelines. Scopolamine “Transdermal Scop” is a belladonna alkaloid with anticholinergic properties. It acts as a nonselective muscarinic antagonist, approved by the FDA for PONV prophylaxis. The use of this novel drug in a triple therapy combination with Dexamethasone and/or Droperidol could be an effective treatment for the prevention of PONV. However, since the FDA issued a warning stating that Droperidol may cause life – threatening arrhythmias as well as a prolongation of the QTc interval, the need to discover new combination therapies for PONV prevention in high risk patients is still in demand. Therefore, we hypothesize that the use of a triple prophylactic therapy consisting of Scopolamine, Dexamethasone, and Ondansetron will be an effective treatment for the prevention of PONV in patients at a high risk for developing PONV during the first 120 hours after neurosurgery.