Ketamine sedation is not associated with clinically meaningful elevation of intraocular pressure

A Prospective Study of the Effects of General Anesthesia on Intraocular Pressure in Healthy Children

Purpose

To determine the effect of general anesthesia on intraocular pressure (IOP) in children with no intraocular pathology and determine which postanesthetic time point is most predictive of preinduction IOP.

Design

Prospective observational study.

Participants

Children with no intraocular pathology ≤ 18 years scheduled for general anesthesia as part of their routine care followed by a pediatric ophthalmologist at Nanjing Medical University.

Methods

Participants underwent a standardized general anesthetic protocol using a mask induction with sevoflurane and propofol maintenance. Intraocular pressure was measured at the following 7 time points: preinduction (taken in the preoperative area), postinduction minutes 1, 3, and 5, and postairway placement minutes 1, 3, and 5 for a total time period of 10 minutes after induction. A generalized estimating equation was used to evaluate the effect of anesthesia on IOP and the effect of patient factors (age, gender, vital signs, and airway type) on preanesthetic and postanesthetic IOP. An IOP prediction model was developed using the postanesthesia IOP measurements for predicting preinduction IOP.

Main Outcome Measures

Intraocular pressure and change in IOP at prespecified time points.

Results

Eighty-five children were enrolled with a mean ± standard deviation (SD) age of 7.5 ± 2.9 years. Mean ± SD preinduction IOP was 20.1 ± 3.7 mmHg. Overall, IOP was lowest at 3 minutes postinduction, decreased to a mean of 13.4 ± 3.7 mmHg (P < 0.001). After this, IOP rose 5 minutes postinduction to 16.5 ± 4.2 mmHg, which did not reach preinduction IOP levels (P < 0.001). The IOP prediction model showed that combining 1 minute postinduction and 3 minutes postairway was most predictive (R2 = 0.13), whereas 1 minute postairway was least predictive of preinduction IOP (R2 = 0.01).

Conclusions

After the induction of general anesthesia in children, IOP temporarily decreases with a trough at 3 minutes postinduction before increasing and remaining stable just below preinduction levels. Intraocular pressure measurements taken 1 minute after induction with 3 minutes after airway placement are most predictive of preinduction IOP, though predictive value is relatively low.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Investigation into the usefulness of cynomolgus monkeys with spontaneously elevated intraocular pressure as a model for glaucoma treatment research

Many glaucoma treatments focus on lowering intraocular pressure (IOP), with novel drugs continuing to be developed. One widely used model involves raising IOP by applying a laser to the trabecular iris angle (TIA) of cynomolgus monkeys to damage the trabecular meshwork. This model, however, presents challenges such as varying IOP values, potential trabecular meshwork damage, and risk of animal distress. This study investigated whether animals with naturally high IOP (>25 mmHg) could be used to effectively evaluate IOP-lowering drugs, thereby possibly replacing laser-induced models. Relationships between TIA size, IOP, and pupil diameter were also examined. Three representative IOP-lowering drugs (latanoprost, timolol, ripasudil) were administered, followed by multiple IOP measurements and assessment of corneal thickness, TIA, and pupil diameter via anterior segment optical coherence tomography (AS-OCT). There was a positive correlation was noted between IOP and corneal thickness before instillation, and a negative correlation between IOP and TIA before instillation. Our findings suggest animals with naturally high IOP could be beneficial for glaucoma research and development as a viable replacement for the laser-induced model and that measuring TIA using AS-OCT along with IOP yields a more detailed evaluation.

Pharmacotherapy optimization for rapid sequence intubation in the emergency department

PURPOSE

Rapid-sequence intubation (RSI) is the process of administering a sedative and neuromuscular blocking agent (NMBA) in rapid succession to facilitate endotracheal intubation. It is the most common and preferred method for intubation of patients presenting to the emergency department (ED). The selection and use of medications to facilitate RSI is critical for success. The purpose of this review is to describe pharmacotherapies used during the RSI process, discuss current clinical controversies in RSI medication selection, and review pharmacotherapy considerations for alternative intubation methods.

SUMMARY

There are several steps to the intubation process requiring medication considerations, including pretreatment, induction, paralysis, and post-intubation sedation and analgesia. Pretreatment medications include atropine, lidocaine, and fentanyl; but use of these agents in clinical practice has fallen out of favor as there is limited evidence for their use outside of select clinical scenarios. There are several options for induction agents, though etomidate and ketamine are the most used due to their more favorable hemodynamic profiles. Currently there is retrospective evidence that etomidate may produce less hypotension than ketamine in patients presenting with shock or sepsis. Succinylcholine and rocuronium are the preferred neuromuscular blocking agents, and the literature suggests minimal differences between succinylcholine and high dose rocuronium in first-pass success rates. Selection between the two is based on patient specific factors, half-life and adverse effect profiles. Finally, medication-assisted preoxygenation and awake intubation are less common methods for intubation in the ED but require different considerations for medication use.

AREAS FOR FUTURE RESEARCH

The optimal selection, dosing, and administration of RSI medications is complicated, and further research is needed in several areas. Additional prospective studies are needed to determine optimal induction agent selection and dosing in patients presenting with shock or sepsis. Controversy exists over optimal medication administration order (paralytic first vs induction first) and medication dosing in obese patients, but there is insufficient evidence to significantly alter current practices regarding medication dosing and administration. Further research examining awareness with paralysis during RSI is needed before definitive and widespread practice changes to medication use during RSI can be made.

Ketamine versus midazolam as an adjuvant to peribulbar block using a single inferonasal injection in patients undergoing vitreoretinal surgery: A randomized controlled trial

INTRODUCTION AND OBJECTIVES

This study aimed to assess the safety and efficacy of midazolam and ketamine as adjuvants to the peribulbar block in vitreoretinal surgeries.

PATIENTS AND METHODS

This randomized controlled trial included 93 adult patients undergoing vitreoretinal surgeries performed with peribulbar anaesthesia. Patients were randomly allocated to 3 groups (31 participants each): control (standard anaesthetic mixture), midazolam (standard mixture + midazolam), and ketamine (standard mixture + ketamine). The primary outcomes were onset of globe akinesia and duration of analgesia. Secondary outcomes were duration of motor blockade, onset of corneal anaesthesia and lid akinesia, and changes in vital data (blood pressure, oxygen saturation, and pulse rate).

RESULTS

The ketamine group vs. the control and midazolam groups showed the most rapid onset of lid and globe akinesia (p < 0.001) and corneal anaesthesia (0.7 ± 0.2 vs. 1.5 ± 0.5 and 1.2 ± 0.4, respectively; p < 0.001) and the longest duration of both analgesia (3.7 ± 0.6 vs. 2.3 ± 0.4 and 3.1 ± 0.6, respectively; p < 0.001) and akinesia (3.8 ± 0.5 vs. 3.0 ± 0.4, and 3.7 ± 0.5, respectively; p < 0.001). The midazolam group showed better outcomes than controls, but the drug was less effective than ketamine. There were no significant differences in vital data among groups (p > 0.05).

CONCLUSIONS

Ketamine is an effective adjuvant for peribulbar blockade. It enhances both motor and sensory blockade by hastening onset and prolonging duration. These effects are desirable in lengthier ophthalmic procedures such as vitreoretinal surgeries. The effects of ketamine were superior to those of midazolam.

Diurnal Variation and Effects of Dilation and Sedation on Intraocular Pressure in Infant Rhesus Monkeys

PURPOSE

Intraocular pressure (IOP) is an important factor in numerous ocular conditions and research areas, including eye growth and myopia. In infant monkeys, IOP is typically measured under anesthesia. This study aimed to establish a method for awake IOP measurement in infant rhesus monkeys, determine diurnal variation, and assess the effects of dilation and sedation.

METHODS

Awake IOP (iCare TonoVet) was measured every 2 h from 7:30 am to 5:30 pm to assess potential diurnal variations in infant rhesus monkeys (age 3 weeks, n = 11). The following day, and every 2 weeks to age 15 weeks, IOP was measured under three conditions: (1) awake, (2) awake and dilated (tropicamide 0.5%), and (3) sedated (ketamine and acepromazine) and dilated. Intraclass correlation coefficient (ICC) was used to determine intersession repeatability, and repeated measures. ANOVA was used to determine effects of age and condition.

RESULTS

At age 3 weeks, mean (±SEM) awake IOP was 15.4 ± 0.6 and 15.2 ± 0.7 mmHg for right and left eyes, respectively (p=.59). The ICC between sessions was 0.63[-0.5 to 0.9], with a mean difference of 2.2 ± 0.3 mmHg. Diurnal IOP from 7:30 am to 5:30 pm showed no significant variation (p=.65). From 3 to 15 weeks of age, there was a significant effect of age (p=.01) and condition (p<.001). Across ages, IOP was 17.8 ± 0.7 mmHg while awake and undilated, 18.4 ± 0.2 mmHg awake and dilated, and 11.0 ± 0.3 mmHg after sedation and dilation.

CONCLUSIONS

Awake IOP measurement was feasible in young rhesus monkeys. No significant diurnal variations in IOP were observed between 7:30 am and 5:30 pm at age 3 weeks. In awake monkeys, IOP was slightly higher after mydriasis and considerably lower after sedation. Findings show that IOP under ketamine/acepromazine anesthesia is significantly different than awake IOP in young rhesus monkeys.

Effect of anesthetic induction with propofol, alfaxalone or ketamine on intraocular pressure in cats: a randomized masked clinical investigation

OBJECTIVE

To compare the effect of propofol, alfaxalone and ketamine on intraocular pressure (IOP) in cats.

STUDY DESIGN

Prospective, masked, randomized clinical trial.

ANIMALS

A total of 43 ophthalmologically normal cats scheduled to undergo general anesthesia for various procedures.

METHODS

Following baseline IOP measurements using applanation tonometry, anesthesia was induced with propofol (n = 15), alfaxalone (n = 14) or ketamine (n = 14) administered intravenously to effect. Then, midazolam (0.3 mg kg^-1) was administered intravenously and endotracheal intubation was performed without application of topical anesthesia. The IOP was measured following each intervention. Data was analyzed using one-way anova and repeated-measures mixed design with post hoc analysis. A p-value <0.05 was considered significant.

RESULTS

Mean ± standard error IOP at baseline was not different among groups (propofol, 18 ± 0.6; alfaxalone, 18 ± 0.7; ketamine, 17 ± 0.5 mmHg). Following induction of anesthesia, IOP increased significantly compared with baseline in the propofol (20 ± 0.7 mmHg), but not in the alfaxalone (19 ± 0.8 mmHg) or ketamine (16 ± 0.7 mmHg) groups. Midazolam administration resulted in significant decrease from the previous measurement in the alfaxalone group (16 ± 0.7 mmHg), but not in the propofol group (19 ± 0.7 mmHg) or the ketamine (16 ± 0.8 mmHg) group. A further decrease was measured after intubation in the alfaxalone group (15 ± 0.9 mmHg).

CONCLUSIONS AND CLINICAL RELEVANCE

Propofol should be used with caution in cats predisposed to perforation or glaucoma, as any increase in IOP should be avoided.

Rapid sequence intubation and the role of the emergency medicine pharmacist: 2022 update

PURPOSE

The dosing, potential adverse effects, and clinical outcomes of the most commonly utilized pharmacologic agents for rapid sequence intubation (RSI) are reviewed for the practicing emergency medicine pharmacist (EMP).

SUMMARY

RSI is the process of establishing a safe, functional respiratory system in patients unable to effectively breathe on their own. Various medications are chosen to sedate and even paralyze the patient to facilitate an efficient endotracheal intubation. The mechanism of action and pharmacokinetic/pharmacodynamic profiles of these agents were described in a 2011 review. Since then, the role of the EMP as well as the published evidence regarding RSI agents, including dosing, adverse effects, and clinical outcomes, has grown. It is necessary for the practicing EMP to update previous practice patterns in order to continue to provide optimal patient care.

CONCLUSION

While the agents used in RSI have changed little, knowledge regarding optimal dosing, appropriate patient selection, and possible adverse effects continues to be gained. The EMP is a key member of the bedside care team and uniquely positioned to communicate this evolving data.

Ketamine and esketamine for crisis management in patients with depression: Why, whom, and how?

Currently, only a limited number of interventions can rapidly relieve depressive symptomatology in patients with major depressive disorder or bipolar disorder experiencing extreme distress. Such crises, especially when suicide attempt or ideation is involved, are a major risk factor of suicide. Ketamine, a N-methyl-d-aspartate glutamate receptor antagonist, and its enantiomer esketamine rapidly reduce depressive symptoms in depressed patients with current suicidal ideation. Recently, esketamine has been approved for use in patients with depression at risk of suicide and for psychiatric emergency by major medical agencies in the United States and Europe, whereas ketamine is increasingly used off-label. However, there is currently limited guidance on why, when, and how to use these drugs in patients with depression to treat a crisis. In this review article, we provide a succinct overview of the cellular and molecular mechanisms of action of ketamine and esketamine, and of the functional brain changes following their administration. We also summarize the major clinical studies on ketamine and esketamine efficacy in patients experiencing a crisis (generally, suicidal ideation), and propose a profile of patients who can benefit most from such drugs, on the basis of neurobiological and clinical observations. Finally, we describe the administration mode, the efficacy and tolerability profiles, the side effect management, possible concomitant treatments and the issue of deprescribing.

Prehospital Drug Assisted Airway Management: An NAEMSP Position Statement and Resource Document

Airway management is a critical intervention for patients with airway compromise, respiratory failure, and cardiac arrest. Many EMS agencies use drug-assisted airway management (DAAM) - the administration of sedatives alone or in combination with neuromuscular blockers - to facilitate advanced airway placement in patients with airway compromise or impending respiratory failure who also have altered mental status, agitation, or intact protective airway reflexes. While DAAM provides several benefits including improving laryngoscopy and making insertion of endotracheal tubes and supraglottic airways easier, DAAM also carries important risks. NAEMSP recommends:DAAM is an appropriate tool for EMS clinicians in systems with clear guidelines, sufficient training, and close EMS physician oversight. DAAM should not be used in settings without adequate resources.EMS physicians should develop clinical guidelines informed by evidence and oversee the training and credentialing for safe and effective DAAM.DAAM programs should include best practices of airway management including patient selection, assessmenct and positioning, preoxygenation strategies including apneic oxygenation, monitoring and management of physiologic abnormalities, selection of medications, post-intubation analgesia and sedation, equipment selection, airway confirmation and monitoring, and rescue airway techniques.Post-DAAM airway placement must be confirmed and continually monitored with waveform capnography.EMS clinicians must have the necessary equipment and training to manage patients with failed DAAM, including bag mask ventilation, supraglottic airway devices and surgical airway approaches.Continuous quality improvement for DAAM must include assessment of individual and aggregate performance metrics. Where available for review, continuous physiologic recordings (vital signs, pulse oximetry, and capnography), audio and video recordings, and assessment of patient outcomes should be part of DAAM continuous quality improvement.

Bilateral Acute Angle-Closure Glaucoma: A Case Report of an Unusual Cause of Acute Headache in a Child

Introduction

Acute angle-closure glaucoma (AACG) is typically considered a disease of adulthood. However, AACG may occasionally be seen in children. The clinical presentation is similar to adults, including headache, vomiting, and eye pain. However, the etiology of angle closure in children is different and most often associated with congenital anterior segment abnormalities. A precipitating factor of AACG in children with previous established, anterior segment abnormalities is eye dilation, which may occur during routine ophthalmological examination with topical mydriasis, or physiologic mydriasis upon entering a dark room.

Case Report

We describe a 5-year-old child with a history of severe prematurity and retinopathy of prematurity (ROP) presenting with bilateral AACG following a routine outpatient, dilated ophthalmological examination. While angle-closure glaucoma has previously been reported in cases of ROP, a bilateral acute attack of AACG following pupil dilation in regressed ROP has hitherto been unreported.

Conclusion

Given the association of ROP and AACG, it can be expected that as the survival rate of premature infants improves, the incidence of ROP and AACG may also increase. It is therefore prudent for the emergency physician to have AACG on the differential for pediatric patients with headache and eye pain.

Effects of acute stress, general anesthetics, tonometry, and temperature on intraocular pressure in rats

Intraocular pressure (IOP) is important for eye health as abnormal levels can led to ocular tissue damage. IOP is typically estimated by tonometry, which only provides snapshots of pressure history. Tonometry also requires subject cooperation and corneal contact that may influence IOP readings. The aim of this research was to investigate IOP dynamics of conscious animals in response to stressors, common anesthetics, tonometry, and temperature manipulations. An eye of male Brown-Norway rats was implanted with a fluid-filled cannula connected to a wireless telemetry system that records IOP continuously. Stress effects were examined by restricting animal movements. Anesthetic effects were examined by varying isoflurane concentration or injecting a bolus of ketamine. Tonometry effects were examined using applanation and rebound tonometers. Temperature effects were examined by exposing anesthetized and conscious animals to warm or cool surfaces. Telemetry recordings revealed that IOP fluctuates spontaneously by several mmHg, even in idle and anesthetized animals. Environmental disturbances also caused transient IOP fluctuations that were synchronous in recorded animals and could last over a half hour. Animal immobilization produced a rapid sustained elevation of IOP that was blocked by anesthetics, whereas little-to-no IOP change was detected in isoflurane- or ketamine-anesthetized animals if body temperature (BT) was maintained. IOP and BT decreased precipitously when heat support was not provided and were highly correlated during surface temperature manipulations. Surface temperature had no impact on IOP of conscious animals. IOP increased slightly during applanation tonometry but not rebound tonometry. The results show that IOP is dynamically modulated by internal and external factors that can activate rapidly and last long beyond the initiating event. Wireless telemetry indicates that animal interaction induces startle and stress responses that raise IOP. Anesthesia blocks these responses, which allows for better tonometry estimates of resting IOP provided that BT is controlled.

Orbital decompression

A trauma patient with orbital compartment syndrome may lose vision within hours of the injury. This article describes an approach to decompressing the orbit which may be sight-saving.

Pharmacological Profile and Ocular Hypotensive Effects of Cromakalim Prodrug 1, a Novel ATP-Sensitive Potassium Channel Opener, in Normotensive Dogs and Nonhuman Primates

Purpose: To evaluate pharmacokinetic parameters and ocular hypotensive effects of cromakalim prodrug 1 (CKLP1) in normotensive large animal models. Methods: Optimal CKLP1 concentration was determined by dose response and utilized in short- (5-8 days) and long-term (60 days) evaluation in hound dogs (n = 5) and African Green Monkeys (n = 5). Blood pressure was recorded 3-5 times per week with a tail cuff. Concentrations of CKLP1 and the parent compound levcromakalim were assessed in hound dog plasma and select tissues by LC-MS/MS after bilateral ocular treatment with CKLP1 for 8 days. Pharmacokinetic parameters were calculated from days 1, 4, and 8 data. After necropsy, histology was assessed in 43 tissue samples from each animal. Results: In hound dogs and African Green monkeys, 10 mM CKLP1 (optimal concentration) significantly lowered intraocular pressure (IOP) by 18.9% ± 1.1% and 16.7% ± 6.7%, respectively, compared with control eyes (P < 0.05). During treatment, no significant change in systolic or diastolic blood pressure was observed in either species (P > 0.1). Average values for half-life of CKLP1 was 295.3 ± 140.4 min, Cmax, 10.5 ± 1.6 ng/mL, and area under the concentration vs. time curve (AUClast) 5261.4 ± 918.9 ng·min/mL. For levcromakalim, average values of half-life were 96.2 ± 27 min, Cmax 1.2 ± 0.2 ng/mL, and AUClast 281.2 ± 110.8 ng·min/mL. No significant pathology was identified. Conclusions: CKLP1 lowered IOP in hound dogs and African green monkeys with no effect on systemic blood pressure. Ocular topical treatment of CKLP1 showed excellent tolerability even after extended treatment periods.

Comeback of ketamine: resurfacing facts and dispelling myths

Initially known as CI-581, ketamine was first synthesized in 1962 as a replacement from phencyclidine. It has since been used as an anesthetic and analgesic. In addition, it has bronchodilating, sedative, and amnestic properties, preserving airway reflexes and sympathetic nervous system tone. Since the discovery of ketamine, it has been a major topic of discussion due to controversies regarding its usage in particular sets of patients. In the past 50 years, despite its potential benefits, it is not commonly used because of concerns of "emergence phenomenon," its use as a substance of abuse, and its systemic side effects. Since 2012, three World Health Organization reviews on ketamine have addressed its international control. Researchers have been studying this wonder drug for a decade worldwide. Many myths of ketamine regarding emergence phenomenon and its use in traumatic brain injury and open eye injury have been disproved in recent times. It is becoming popular in pre-hospital settings, critical care, emergency medicine, low-dose acute pain services, and adjuvant in regional anesthesia techniques. This review highlights the current consensus on the various applications of ketamine in the literature.

Comparative Study of Retrobulbar Block versus Ketamine Infusion during Eye Enucleation/Evisceration (Randomized Controlled Trial)

Background

The aim of this study is to compare the safety and efficacy of retrobulbar block versus intraoperative ketamine infusion in eye enucleation or evisceration under general anesthesia.

Materials and Methods

Forty-five patients belonging to American Society of Anesthesiologists Physical Status I and II undergoing eye enucleation or evisceration were randomly allocated to three equal groups (15 patients each). General anesthesia was used as the standardized technique in all patients. Group R received a single retrobulbar injection, Group K received intravenous ketamine infusion, and Group C received normal saline with the same rate of ketamine infusion. Intraoperative heart rate and mean arterial pressure, recovery time, postoperative pain score, time to first rescue analgesic, number of patients who required rescue analgesia, and any adverse events were reported.

Results

Postoperative pain Visual Analog Scale was significantly lower in R and K groups in comparison to the C group and was significantly higher in K than R group at 3, 6, 12, and 24 h. In addition, the time to first rescue analgesic was significantly longer in R group (429 ± 54 min) than that in K group (272 ± 34 min), but compared to both groups, it was longer in C group (52 ± 7 min). In K group, the recovery time was longer with higher sedation score in comparison to the other two groups.

Conclusions

Single retrobulbar injection and low-dose ketamine infusion are safe and effective when used as adjuvants to general anesthesia, but retrobulbar block provides better control of postoperative pain with prolonged time to first rescue analgesic and reduced analgesic consumption.

Effect of general anaesthesia on intraocular pressure in paediatric patients: a systematic review

OBJECTIVES

Assessment of the impact of general anaesthetic agents on intraocular pressure (IOP) in children via systematic review.

METHODS

Pubmed, Embase, and CENTRAL databases were systematically searched to identify randomised controlled trials, prospective, and interventional studies. The search included all studies through October 5, 2018 with no date or language restrictions. A linear mixed-effects regression analysis was performed to study the change in IOP after general anaesthesia (GA).

RESULTS

The strategy identified 518 studies that met search criteria. Six studies (531 eyes) were included for quantitative synthesis. Seven categories of mixed and non-mixed induction and maintenance agents were compared. When assessing all agents utilising a model of mean IOP as a function of time, IOP decreased after induction phase at a rate of -0.59 ± 0.19 mmHg/min (P value = 0.006).

CONCLUSIONS

This systematic review showed that most anaesthetic agents significantly decrease IOP over time after the induction phase of general anaesthesia in children. An understanding of the effects of GA on IOP is critical for those performing paediatric ophthalmic examinations under anaesthesia.

Removal of an Impaled Intraocular Hair Comb Following Self-inflicted Trauma

Ocular trauma is one of the most common and vision-threatening ophthalmic presentations with a wide spectrum of complications, such as bleeding, infection, vision loss, and enucleation. A 64-year-old-male presented to the emergency department (ED) with a self-inflicted orbital penetrating injury with a hair comb. Computed tomography showed the comb traversed the medial orbit inferior to the medial rectus but did not damage the optic nerve; there were no globe or orbital wall fractures. His ocular exam was significant for a right eye afferent pupillary defect and decreased visual acuity 20/800, consistent with optic neuropathy. Primary concerns were stabilizing and removing the foreign body without causing further damage in the setting of an uncooperative patient. The comb was removed with the aid of local and systemic analgesia using gentle traction and normal saline irrigation. The patient was admitted for systemic and topical antibiotics and showed improvement in visual acuity and resolution of his optic neuropathy. This case illustrates the importance of rapid ED assessment and management of complex penetrating ocular trauma. Examination should specifically look for signs of globe rupture and optic nerve injury. Expedited foreign body removal should be managed together with an ophthalmologist with procedural sedation and broad-spectrum antibiotics to avoid further visual and infectious complications.

Effect of Anesthesia on Intraocular Pressure Measured With Continuous Wireless Telemetry in Nonhuman Primates

Purpose

To compare the effects of both injectable anesthesia (ketamine/dexmedetomidine versus ketamine/xylazine) and inhalant anesthesia (isoflurane) on IOP using continuous, bilateral IOP telemetry in nonhuman primates (NHP).

Methods

Bilateral IOP was recorded continuously using a proven implantable telemetry system in five different sessions at least 2 weeks apart in four male rhesus macaques under two conditions: ketamine (3 mg/kg) with dexmedetomidine (50 μg/kg) or ketamine with xylazine (0.5 mg/kg) for induction, both followed by isoflurane for maintenance. IOP transducers were calibrated via anterior chamber manometry. Bilateral IOP was averaged over 2 minutes after injectable anesthetic induction and again after isoflurane inhalant had stabilized the anesthetic plane, then compared to baseline IOP measurements acquired immediately prior to anesthesia (both before and after initial human contact).

Results

When compared to pre-contact baseline measurements, ketamine/dexmedetomidine injectable anesthesia lowers IOP by 1.5 mm Hg on average (P < 0.05), but IOP did not change with ketamine/xylazine anesthesia. IOP returned to baseline levels shortly after isoflurane gas anesthesia was initiated. However, injectable anesthesia lowered IOP by an average of 5.4 mm Hg when compared to that measured after initial human contact (P < 0.01).

Conclusions

Anesthetic effects on IOP are generally small when compared to precontact baseline but much larger when compared to IOP measures taken after human contact, indicating that IOP is temporarily elevated due to acute stress (similar to a "white coat effect") and then decreased with anesthetic relaxation. Anesthetic induction with ketamine/xylazine and maintenance with isoflurane gas should be used when IOP is measured postanesthesia.

Consensus Guidelines on the Use of Intravenous Ketamine Infusions for Acute Pain Management From the American Society of Regional Anesthesia and Pain Medicine, the American Academy of Pain Medicine, and the American Society of Anesthesiologists

BACKGROUND

Ketamine infusions have been used for decades to treat acute pain, but a recent surge in usage has made the infusions a mainstay of treatment in emergency departments, in the perioperative period in individuals with refractory pain, and in opioid-tolerant patients. The widespread variability in patient selection, treatment parameters, and monitoring indicates a need for the creation of consensus guidelines.

METHODS

The development of acute pain ketamine guidelines grew as a corollary from the genesis of chronic pain ketamine guidelines. The charge for the development of acute pain ketamine guidelines was provided by the Boards of Directors of both the American Society of Regional Anesthesia and Pain Medicine and the American Academy of Pain Medicine, who approved the document along with the American Society of Anesthesiologists' Committees on Pain Medicine and Standards and Practice Parameters. The committee chair developed questions based on input from the committee during conference calls, which the committee then refined. Groups of 3 to 5 panel members and the committee chair were responsible for answering individual questions. After preliminary consensus was achieved, the entire committee made further revisions via e-mail and conference calls.

RESULTS

Consensus guidelines were prepared in the following areas: indications, contraindications for acute pain and whether they differ from those for chronic pain, the evidence for the use of ketamine as an adjunct to opioid-based therapy, the evidence supporting patient-controlled ketamine analgesia, the use of nonparenteral forms of ketamine, and the subanesthetic dosage range and whether the evidence supports those dosages for acute pain. The group was able to reach consensus on the answers to all questions.

CONCLUSIONS

Evidence supports the use of ketamine for acute pain in a variety of contexts, including as a stand-alone treatment, as an adjunct to opioids, and, to a lesser extent, as an intranasal formulation. Contraindications for acute pain are similar to those for chronic pain, partly based on the observation that the dosage ranges are similar. Larger studies evaluating different acute pain conditions are needed to enhance patient selection, determine the effectiveness of nonparenteral ketamine alternatives, define optimal treatment parameters, and develop protocols optimizing safety and access to care.

Consensus Guidelines on the Use of Intravenous Ketamine Infusions for Chronic Pain From the American Society of Regional Anesthesia and Pain Medicine, the American Academy of Pain Medicine, and the American Society of Anesthesiologists

BACKGROUND

Over the past 2 decades, the use of intravenous ketamine infusions as a treatment for chronic pain has increased dramatically, with wide variation in patient selection, dosing, and monitoring. This has led to a chorus of calls from various sources for the development of consensus guidelines.

METHODS

In November 2016, the charge for developing consensus guidelines was approved by the boards of directors of the American Society of Regional Anesthesia and Pain Medicine and, shortly thereafter, the American Academy of Pain Medicine. In late 2017, the completed document was sent to the American Society of Anesthesiologists' Committees on Pain Medicine and Standards and Practice Parameters, after which additional modifications were made. Panel members were selected by the committee chair and both boards of directors based on their expertise in evaluating clinical trials, past research experience, and clinical experience in developing protocols and treating patients with ketamine. Questions were developed and refined by the committee, and the groups responsible for addressing each question consisted of modules composed of 3 to 5 panel members in addition to the committee chair. Once a preliminary consensus was achieved, sections were sent to the entire panel, and further revisions were made. In addition to consensus guidelines, a comprehensive narrative review was performed, which formed part of the basis for guidelines.

RESULTS

Guidelines were prepared for the following areas: indications; contraindications; whether there was evidence for a dose-response relationship, or a minimum or therapeutic dose range; whether oral ketamine or another N-methyl-D-aspartate receptor antagonist was a reasonable treatment option as a follow-up to infusions; preinfusion testing requirements; settings and personnel necessary to administer and monitor treatment; the use of preemptive and rescue medications to address adverse effects; and what constitutes a positive treatment response. The group was able to reach consensus on all questions.

CONCLUSIONS

Evidence supports the use of ketamine for chronic pain, but the level of evidence varies by condition and dose range. Most studies evaluating the efficacy of ketamine were small and uncontrolled and were either unblinded or ineffectively blinded. Adverse effects were few and the rate of serious adverse effects was similar to placebo in most studies, with higher dosages and more frequent infusions associated with greater risks. Larger studies, evaluating a wider variety of conditions, are needed to better quantify efficacy, improve patient selection, refine the therapeutic dose range, determine the effectiveness of nonintravenous ketamine alternatives, and develop a greater understanding of the long-term risks of repeated treatments.

Effects of propofol on intraocular pressure in premedicated and nonpremedicated dogs with and without glaucoma

OBJECTIVE To establish a study cutoff for evidence of glaucoma on the basis of IOP measurements from a large population of healthy dogs and to assess the effects of IV propofol administration on IOPs in premedicated and nonpremedicated dogs with and without glaucoma defined by this method. DESIGN Prospective, descriptive study. ANIMALS 234 client-owned dogs. PROCEDURES IOPs measured in 113 healthy dogs (226 eyes) were used to calculate an IOP value indicative of glaucoma. The IOPs were measured in an additional 121 dogs (237 eyes) undergoing ophthalmic surgery. Midazolam-butorphanol was administered IV as preanesthetic medication to 15 and 87 dogs with and without glaucoma, respectively. A placebo (lactated Ringer solution) was administered IV to 8 and 11 dogs with and without glaucoma, respectively. Anesthesia of surgical patients was induced with propofol IV to effect. The IOPs and physiologic variables of interest were recorded before (baseline) and after preanesthetic medication or placebo administration and after propofol administration. RESULTS An IOP > 25 mm Hg was deemed indicative of glaucoma. Compared with baseline measurements, mean IOP was increased after propofol administration in nonpremedicated dogs without glaucoma and unchanged in nonpremedicated dogs with glaucoma. Propofol-associated increases in IOP were blunted in premedicated dogs without glaucoma; IOP in affected eyes of premedicated dogs with glaucoma was decreased after preanesthetic medication and after propofol administration. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that preexisting IOP influences the response to anesthetic drugs, and administration of preanesthetic medication with muscle-relaxing properties may blunt or reduce propofol-induced increases in IOP. Further research with a larger number of dogs is needed to confirm our results in dogs with glaucoma.

Prevalence of primary open-angle glaucoma among patients with obstructive sleep apnea

OBJECTIVE

Our objective was to determine primary open-angle glaucoma (POAG) prevalence among obstructive sleep apnea (OSA) patients because the perioperative environment risks further damaging the optic nerve.

STUDY DESIGN

We analyzed a "convenience sample" referred by Sleep Medicine for oral appliances because of continuous positive airway pressure intolerance. We determined the aggregate prevalence of the 3 POAG subtypes-"classic" open-angle glaucoma (COAG), normal-tension glaucoma (NTG), and open-angle glaucoma suspect (OAGS)-among the index population and compared it with that of same hospital's general population. Similarly determined were associations between OSA severity levels (apnea-hypopnea index [AHI]) and POAG subtypes.

RESULTS

Among the study sample of 225 patients with OSA (96.4% male; mean age 58.5 ± 12.3 years), 47 (20.9%) had POAG, with a subtype distribution of COAG: 12 (25.5%), NTG: 8 (17.0%), and OAGS: 27 (57.4%). The POAG prevalence rate among medical center's general population was 2.5%, which was significantly less (P < .00001) than among those with comorbid OSA. Severity of the breathing disorder (AHI) failed to identify a significant correlation to any POAG subtype (P > .05).

CONCLUSION

The significant prevalence of POAG among OSA sufferers suggests need for preoperative consultations from an ophthalmologist to determine eye health and possibly an anesthesiologist to avoid potential vision loss.

Battlefield Analgesia in Tactical Combat Casualty Care

At the start of the Afghanistan conflict, battlefield analgesia for US military casualties was achieved primarily through the use of intramuscular (IM) morphine. This is a suboptimal choice, since IM morphine is slow-acting, leading to delays in effective pain relief and the risk of overdose and death when dosing is repeated in order to hasten the onset of analgesia. Advances in battlefield analgesia, pioneered initially by Tactical Combat Casualty Care (TCCC), and the Army's 75th Ranger Regiment, have now been incorporated into the Triple-Option Analgesia approach. This novel strategy has gained wide acceptance in the US military. It calls for battlefield analgesia to be achieved using 1 or more of 3 options depending on the casualty's status: 1) the meloxicam and acetaminophen in the combat wound medication pack (CWMP) for casualties with relatively minor pain that are still able to function effectively as combatants if their sensorium is not altered by analgesic medications; 2) oral transmucosal fentanyl citrate (OTFC) for casualties who have moderate to severe pain, but who are not in hemorrhagic shock or respiratory distress, and are not at significant risk for developing either condition; or 3) ketamine for casualties who have moderate to severe pain, but who are in hemorrhagic shock or respiratory distress or are at significant risk for developing either condition. Ketamine may also be used to increase analgesic effect for casualties who have previously been given opioid medication. The present paper outlines the evolution and evidence base for battlefield analgesia as currently recommended by TCCC. It is not intended to be a comprehensive review of all prehospital analgesic options.

How does sevoflurane induction, followed by a ketamine maintenance infusion, affect intraocular pressure? Establishment of an anaesthetic protocol for paediatric glaucoma examinations under anaesthesia

Accurate measurement of intraocular pressure (IOP) is essential in paediatric glaucoma management. Children require serial measurements and examination under anaesthesia (EUA). Most anaesthetic agents reduce IOP, and the ideal time to measure IOP under anaesthesia is questionable.

STUDY PURPOSE

To determine the effect of sevoflurane induction, followed by intravenous ketamine infusion on IOP, in children undergoing EUA for glaucoma or suspected glaucoma, and to establish the earliest time point at which reliable, repeatable IOP measurements can be obtained under anaesthesia.

METHOD

A prospective, descriptive study of IOP changes occurring in children requiring EUAs. A standardised anaesthetic protocol: sevoflurane induction, intravenous cannulation, 2 mg/kg intravenous ketamine bolus and 4 mg/kg/hour maintenance for 15 min. IOP measurements (taken supine with a Perkins applanation tonometer) and physiological variables were recorded.

RESULTS

IOPs were measured in 25 children (50 eyes). Twenty-six eyes (52%) were glaucomatous. Mean patient age was 29 months (2-88 months). Physiological variables returned to baseline at 8 min, correlating with recorded sevoflurane elimination. Mean IOP after sevoflurane induction was 3.68 mm Hg lower than with ketamine maintenance at 15 min (95% CI 1.35 to 6.02 mm Hg) (p=0.002). Contrastingly, the difference in IOP between ketamine anaesthesia at 15 min and near wakefulness was 0.28 mm Hg (95% CI -2.23 to 2.79 mm Hg) (p=0.826).

CONCLUSION

Sevoflurane's IOP-lowering effect is reversed 15 min after the discontinuation of the inhalational gas, if anaesthesia is maintained with an intravenous ketamine infusion. IOP measurements appear to stabilise at this time point until the point of near wakefulness and may reflect awake values.

A Novel Agent for Management of Agitated Delirium: A Case Series of Ketamine Utilization in the Pediatric Emergency Department

Control of the agitated patient in the emergency department is challenging. Many options exist for chemical sedation, but most have suboptimal pharmacodynamic action, and many have undesirable adverse effects. There are reports of ketamine administration for control of agitation prehospital and in traumatically injured patients. Ketamine is a noncompetitive N-methyl-D-aspartic acid receptor antagonist, making it an effective dissociative agent. We present 5 cases of ketamine administration to manage agitated adolescent patients with underlying psychiatric disease and/or drug intoxication. Ketamine, as a dissociative agent, may be an alternative pharmacological consideration for the control of agitation in patients with undifferentiated agitated delirium.

Effect of anesthesia on intraocular pressure measurement in children

Measurement of the intraocular pressure (IOP) is central to the diagnosis and management of pediatric glaucoma. An examination under anesthesia is often necessary in pediatric patients. Different agents used for sedation or general anesthesia have varied effects on IOP. Hemodynamic factors, methods of airway management, tonometry technique, and body positioning can all affect IOP measurements. The most accurate technique is one that reflects the awake IOP. We review factors affecting IOP measurements in the pediatric population and provide recommendations on the most accurate means to measure IOP under anesthesia based on the present literature.

Does general anesthesia have a clinical impact on intraocular pressure in children?

BACKGROUND

Reliable measurement of intraocular pressure (IOP) is crucial in pediatric patients with suspected glaucoma. General anesthesia (GA) is usually needed in infants to allow a thorough examination. However, anesthesia itself may influence IOP, depending on the type used and the depth of sedation. The purpose of this study was to evaluate the normal distribution of IOP during GA in healthy children and to analyze differences in IOP relative to the anesthetics used and the measurement time point.

METHODS

Approval for this observational study was received from the local institutional review boards and written informed consent was obtained from the children's parents. A total of 100 pediatric patients with no history of glaucoma scheduled for nonintraocular surgery underwent general anesthesia, induced with sevoflurane (s) or propofol (p) and maintained with either sevoflurane with remifentanil (S) or propofol with remifentanil (P). The patients were grouped to one of four subgroups (sS, sP, pP, pS) depending on the anesthetics used during induction and maintenance. Hemodynamic parameters and IOP were measured in both eyes at four defined time points: before anesthesia induction (M1); in apnea immediately after induction and before insertion of a laryngeal mask airway (M2); in deep anesthesia during mechanical ventilation (M3); and after extubation (M4), using a handheld Perkins applanation tonometer. Differences in IOP in both eyes during the measurement periods were analyzed using multivariate repeated-measures analysis of variance and Tukey-HSD as a posthoc test with statistical significance set at P < 0.05. Pearson correlation coefficient was used to investigate further relationships between heart rate, systolic blood pressure, and IOP.

RESULTS

General anesthesia reduced IOP significantly. The mean IOP was normally distributed, with a mean of 7.4 ± 2.89 mmHg at M1. It decreased significantly to a minimum of 5.6 ± 3.04 mmHg (P < 0.01) at M2 and increased significantly to 7.2 ± 2.51 mmHg (P < 0.01) at M3 and again to 8.4 ± 3.72 mmHg (P = 0.03) at M4. All four subgroups (sS, sP, pP, pS) showed comparable decreases in IOP between M1 and M2. During deep anesthesia (M3) and during reversal (M4), the IOP increased again in all groups. During reversal (M4), however, the sS group had a significantly lower IOP than the pP group (P = 0.001) and sP group (P = 0.02). There were no correlations between changes in IOP and gender, age, or type of surgery.

CONCLUSIONS

Sevoflurane and propofol, both in combination with remifentanil, significantly lower IOP in children. Individual IOP levels rise and fall during anesthesia, depending on the time point of measurement. The lowest IOP can be measured immediately after induction of anesthesia. This needs to be taken into account when measuring IOP in children.

Pain management in military trauma

The wounded warrior requires immediate care, and at times, evacuation from injury. Care may be self-regulated, or may require more advanced care under the direction of medics or advanced practitioners, including physicians and surgeons. While survivability is the immediate priority, pain management has become a military initiative, recognizing that poor management of acute pain may lead to the development of chronic pain and post-traumatic stress disorder. This article reviews current initiatives used in current conflict situations, as well as those in continued care following initial stabilization.

Effects of ketamine, propofol, or thiopental administration on intraocular pressure and qualities of induction of and recovery from anesthesia in horses

OBJECTIVE

To assess the effects of ketamine hydrochloride, propofol, or compounded thiopental sodium administration on intraocular pressure (IOP) and qualities of induction of and recovery from anesthesia in horses.

ANIMALS

6 healthy adult horses.

PROCEDURES

Horses were sedated with xylazine hydrochloride (0.5 mg/kg), and anesthesia was induced with guaifenesin followed by ketamine (2 mg/kg), propofol (3 mg/kg), or thiopental (4 mg/kg) in a crossover study with ≥ 1 week between treatments. For each horse, IOP in the right eye was measured with a handheld applanation tonometer before and after xylazine administration, at the time of recumbency, and every 3 minutes after induction of anesthesia until spontaneous movement was observed. Cardiorespiratory responses and venous blood measurements were recorded during anesthesia. Induction of and recovery from anesthesia were subjectively evaluated by investigators who were unaware of the anesthetic treatment of each horse. Data were analyzed via a repeated-measures ANOVA with Holm-Ŝidák post hoc comparisons.

RESULTS

Compared with findings after xylazine administration (mean ± SD, 17 ± 3 mm Hg), thiopental decreased IOP by 4 ± 23%, whereas propofol and ketamine increased IOP by 8 ± 11% and 37 ± 16%, respectively. Compared with the effects of ketamine, propofol and thiopental resulted in significantly lower IOP at the time of recumbency and higher heart rates at 3 minutes after induction of anesthesia. No other significant differences among treatments were found.

CONCLUSIONS AND CLINICAL RELEVANCE

These findings support the use of thiopental or propofol in preference to ketamine for horses in which increases in IOP should be minimized.

Pro-con debate: etomidate or ketamine for rapid sequence intubation in pediatric patients

When caring for critically ill children, airway management remains a primary determinant of the eventual outcome. Airway control with endotracheal intubation is frequently necessary. Rapid sequence intubation (RSI) is generally used in emergency airway management to protect the airway from passive regurgitation of gastric contents. Along with a rapid acting neuromuscular blocking agent, sedation is an essential element of RSI. A significant safety concern regarding sedatives is the risk of hypotension and cardiovascular collapse, especially in critically ill patients or those with pre-existing comorbid conditions. Ketamine and etomidate, both of which provide effective sedation with limited effects on hemodynamic function, have become increasingly popular as induction agents for RSI. However, experience and clinical investigations have raised safety concerns associated with both etomidate and ketamine. Using a pro-con debate style, the following manuscript discusses the use of ketamine versus etomidate in RSI.

The effect of ketamine on intraocular pressure in pediatric patients during procedural sedation

OBJECTIVES

Ketamine is one of the most commonly used procedural sedation and analgesia (PSA) agents in pediatric emergency departments (PEDs). It is considered a very safe and reliable agent, with limited respiratory suppression, hemodynamic effects, and adverse outcomes. However, physicians are often reluctant to use ketamine for patients with eye injuries due to a concern that ketamine might increase intraocular pressure (IOP). The objective was to measure IOP in previously healthy children receiving ketamine for PSA for a reason other than eye injury.

METHODS

This was a prospective noninferiority study of patients seen in an academic tertiary care children's hospital emergency department (ED) who required ketamine for PSA. The authors measured IOP in the right eye as soon as possible after ketamine had been administered and then at 2.5, 5, and 10 minutes after ketamine had been administered.

RESULTS

Eighty patients were enrolled (28 between 1 and 5 years of age, 26 between 6 and 10 years, 26 between 11 and 15 years); 49 (61%) were male. Procedures requiring PSA included fracture/dislocation reduction (63%), abscess incision and drainage (16%), laceration repair (11%), dental abscess incision and drainage (6%), and other (4%). The mean total ketamine dosage was 1.6 mg/kg (95% confidence interval [CI] = 1.4 to 1.7). The mean initial IOP was 17.5 mm Hg (95% CI = 16.4 to 18.6 mm Hg) and at 2.5 minutes was 18.9 mm Hg (95% CI = 17.9 to 19.9 mm Hg). The mean difference was 1.4 mm Hg (95% CI = 0.4 to 2.4 mm Hg). Using a noninferiority margin of 2.6 mm Hg (15%), noninferiority (no significant elevation in IOP) was demonstrated with 95% confidence between the first and second readings.

CONCLUSIONS

 Ketamine does not significantly increase IOP in pediatric patients without eye injuries receiving typical PSA dosages in the PED. Further study should assess its safety in patients with ocular injury.