Intraoperative Clonidine Administration to Neurosurgical Patients

Alpha-2 adrenergic agonists for the prevention of cardiac complications among adults undergoing surgery

BACKGROUND

The surgical stress response plays an important role on the pathogenesis of perioperative cardiac complications. Alpha-2 adrenergic agonists attenuate this response and may help prevent postoperative cardiac complications.

OBJECTIVES

To determine the efficacy and safety of α-2 adrenergic agonists for reducing mortality and cardiac complications in adults undergoing cardiac surgery and non-cardiac surgery.

SEARCH METHODS

We searched CENTRAL (2017, Issue 4), MEDLINE (1950 to April Week 4, 2017), Embase (1980 to May 2017), the Science Citation Index, clinical trial registries, and reference lists of included articles.

SELECTION CRITERIA

We included randomized controlled trials that compared α-2 adrenergic agonists (i.e. clonidine, dexmedetomidine or mivazerol) against placebo or non-α-2 adrenergic agonists. Included trials had to evaluate the efficacy and safety of α-2 adrenergic agonists for preventing perioperative mortality or cardiac complications (or both), or measure one or more relevant outcomes (i.e. death, myocardial infarction, heart failure, acute stroke, supraventricular tachyarrhythmia and myocardial ischaemia).

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality, extracted data and independently performed computer entry of abstracted data. We contacted study authors for additional information. Adverse event data were gathered from the trials. We evaluated included studies using the Cochrane 'Risk of bias' tool, and the quality of the evidence underlying pooled treatment effects using GRADE methodology. Given the clinical heterogeneity between cardiac and non-cardiac surgery, we analysed these subgroups separately. We expressed treatment effects as pooled risk ratios (RR) with 95% confidence intervals (CI).

MAIN RESULTS

We included 47 trials with 17,039 participants. Of these studies, 24 trials only included participants undergoing cardiac surgery, 23 only included participants undergoing non-cardiac surgery and eight only included participants undergoing vascular surgery. The α-2 adrenergic agonist studied was clonidine in 21 trials, dexmedetomidine in 24 trials and mivazerol in two trials.In non-cardiac surgery, there was high quality evidence that α-2 adrenergic agonists led to a similar risk of all-cause mortality compared with control groups (1.3% with α-2 adrenergic agonists versus 1.7% with control; RR 0.80, 95% CI 0.61 to 1.04; participants = 14,081; studies = 16). Additionally, the risk of cardiac mortality was similar between treatment groups (0.8% with α-2 adrenergic agonists versus 1.0% with control; RR 0.86, 95% CI 0.60 to 1.23; participants = 12,525; studies = 5, high quality evidence). The risk of myocardial infarction was probably similar between treatment groups (RR 0.94, 95% CI 0.69 to 1.27; participants = 13,907; studies = 12, moderate quality evidence). There was no associated effect on the risk of stroke (RR 0.93, 95% CI 0.55 to 1.56; participants = 11,542; studies = 7; high quality evidence). Conversely, α-2 adrenergic agonists probably increase the risks of clinically significant bradycardia (RR 1.59, 95% CI 1.18 to 2.13; participants = 14,035; studies = 16) and hypotension (RR 1.24, 95% CI 1.03 to 1.48; participants = 13,738; studies = 15), based on moderate quality evidence.There was insufficient evidence to determine the effect of α-2 adrenergic agonists on all-cause mortality in cardiac surgery (RR 0.52, 95% CI 0.26 to 1.04; participants = 1947; studies = 16) and myocardial infarction (RR 1.01, 95% CI 0.43 to 2.40; participants = 782; studies = 8), based on moderate quality evidence. There was one cardiac death in the clonidine arm of a study of 22 participants. Based on very limited data, α-2 adrenergic agonists may have reduced the risk of stroke (RR 0.37, 95% CI 0.15 to 0.93; participants = 1175; studies = 7; outcome events = 18; low quality evidence). Conversely, α-2 adrenergic agonists increased the risk of bradycardia from 6.4% to 12.0% (RR 1.88, 95% CI 1.35 to 2.62; participants = 1477; studies = 10; moderate quality evidence), but their effect on hypotension was uncertain (RR 1.19, 95% CI 0.87 to 1.64; participants = 1413; studies = 9; low quality evidence).These results were qualitatively unchanged in subgroup analyses and sensitivity analyses.

AUTHORS' CONCLUSIONS

Our review concludes that prophylactic α-2 adrenergic agonists generally do not prevent perioperative death or major cardiac complications. For non-cardiac surgery, there is moderate-to-high quality evidence that these agents do not prevent death, myocardial infarction or stroke. Conversely, there is moderate quality evidence that these agents have important adverse effects, namely increased risks of hypotension and bradycardia. For cardiac surgery, there is moderate quality evidence that α-2 adrenergic agonists have no effect on the risk of mortality or myocardial infarction, and that they increase the risk of bradycardia. The quality of evidence was inadequate to draw conclusions regarding the effects of alpha-2 agonists on stroke or hypotension during cardiac surgery.

Effect of dexmedetomidine on brain edema and neurological outcomes in surgical brain injury in rats

BACKGROUND

Surgical brain injury (SBI) is damage to functional brain tissue resulting from neurosurgical manipulations such as sharp dissection, electrocautery, retraction, and direct applied pressure. Brain edema is the major contributor to morbidity with inflammation, necrosis, oxidative stress, and apoptosis likely playing smaller roles. Effective therapies for SBI may improve neurological outcomes and postoperative morbidities associated with brain surgery. Previous studies show an adrenergic correlation to blood-brain barrier control. The α-2 receptor agonist dexmedetomidine (DEX) has been shown to improve neurological outcomes in stroke models. We hypothesized that DEX may reduce brain edema and improve neurological outcomes in a rat model of SBI.

METHODS

Male Sprague-Dawley rats (n = 63) weighing 280 to 350 g were randomly assigned to 1 of 4 IP treatment groups: sham IP, vehicle IP, DEX 10 mg/kg, and DEX 30 mg/kg. Treatments were given 30 min before SBI. These treatment groups were repeated to observe the physiologic impact of DEX on mean arterial blood pressure (MAP), heart rate (HR), and blood glucose on SBI naïve animals. Rats were also assigned to 4 postinjury IV treatment groups: sham IV, vehicle IV, DEX 10/5, and DEX 30/15 (DEX group doses were 10 and 30 mg/kg/hr, with 5 and 15 mg/kg initial loading doses, respectively). Initial loading doses began 20 min after SBI, followed by 2 h of infusion. SBI animals were subjected to neurological testing 24 h after brain injury by a blinded observer, promptly killed, and brain water content measured via the dry/wet weight method.

RESULTS

All treatment groups showed a significant difference in ipsilateral frontal brain water content and neurological scores when compared with sham animals. However, there was no difference between DEX-treated and vehicle animals. Physiologic monitoring showed treatment with low or high doses of DEX significantly decreased MAP and HR, and briefly increased blood glucose compared with naïve or vehicle-treated animals.

CONCLUSIONS

DEX administration did not reduce brain edema or improve neurological function after SBI in this study. The statistical difference in brain water content and neurological scores when comparing sham treatment to vehicle and DEX treatments shows consistent reproduction of this model. Significant changes in MAP, HR, and blood glucose after DEX as compared to vehicle and sham treatments suggest appropriate delivery of drug.

Comparative evaluation of atenolol and clonidine premedication on cardiovascular response to nasal speculum insertion during trans-sphenoid surgery for resection of pituitary adenoma: A prospective, randomised, double-blind, controlled study

Severe cardiovascular responses in the form of tachycardia and hypertension following nasal speculum insertion occur during sublabial rhinoseptal trans-sphenoid approach for resection of small pituitary tumours. We compare the effects of preoperative administration of clonidine (α-2 agonist) and atenolol (α-blocker) over haemodynamic response, caused by speculum insertion during trans-sphenoid pituitary resection. We enrolled 66 patients in age range 18-65 years, of ASA I–II, and of either sex undergoing elective sublabial rhinoseptal trans-sphenoidal hypophysectomy. Group I (control) received placebo, group II (clonidine) received tablet clonidine 5 µg/kg, and group III (atenolol) received tablet atenolol 0.5 mg/kg. The heart rate increased on speculum insertion and 5 and 10 minutes following speculum insertion as compared to the pre-speculum values in the control group, while no change in the heart rate was observed in other groups (P<0.05). There was a rise in the mean arterial pressure during and 5, 10, and 15 minutes after nasal speculum insertion in the control group, whereas it was not seen in other groups (P<0.05). We therefore suggest that oral clonidine and oral atenolol (given 2 hours prior to surgery) is an equally effective and safe method of attenuating haemodynamic response caused by nasal speculum insertion during trans-sphenoid pituitary resection.

Pharmacologic options for reducing the shivering response to therapeutic hypothermia

Recent literature has demonstrated significant improvements in neurologic outcomes in patients who have received induced hypothermia in the setting of out-of-hospital cardiac arrest. Through multiple metabolic mechanisms, the induction of hypothermia slows the progression and devastation of transient cerebral hypoxia. Despite these benefits, the desired reduction in core temperature is often a challenging venture as the body attempts to maintain homeostasis through the induction of thermoregulatory processes aimed at elevating body temperature. Shivering is an involuntary muscular activity that enhances heat production in an attempt to restore homeostasis. For successful induction and maintenance of induced hypothermia, shivering, as well as other thermoregulatory responses, must be overcome. Several pharmacologic options are available, either used alone or in combination, that safely and effectively prevent or treat shivering after the induction of hypothermia. We conducted a PubMed search (1966-March 2009) to identify all human investigations published in English that discussed pharmacologic mechanisms for the control of shivering. Among these options, clonidine, dexmedetomidine, and meperidine have demonstrated the greatest and most clinically relevant impact on depression of the shivering threshold. More research in this area is needed, however, and the role of the clinical pharmacist in the development and implementation of this therapy needs to be defined.

Oral clonidine attenuates the fall in mean arterial pressure due to scalp infiltration with epinephrine-lidocaine solution in patients undergoing craniotomy: a prospective, randomized, double-blind, and placebo controlled trial

BACKGROUND

Scalp infiltration with epinephrine-lidocaine solution in patients undergoing neurosurgery may result in transient but significant hypotension. We investigated whether premedication with alpha2-adrenoreceptor agonist clonidine, which also exhibits alpha1-adrenoreceptor mediated vasoconstriction, would prevent or attenuate this fall in mean arterial pressure (MAP).

METHODS

Sixty-six American Society of Anesthesiologists I and II adult patients, 18 to 50 years, undergoing elective tumor decompression were recruited into this prospective, randomized, double-blind, placebo controlled study, and scheduled to receive either oral pantoprazole 40 mg (placebo group) or oral clonidine 3 microg/kg (clonidine group), 90 minutes before induction of anesthesia. Primary end points studied were heart rate (HR) and MAP in both groups measured just before scalp infiltration (preinfiltration baseline) and then every 30 seconds for 5 minutes after initiation of scalp infiltration with 2.5 microg/mL epinephrine contained in 15 mL of 1% lidocaine solution.

RESULTS

There was no significant change in HR in the 2 groups during the study period compared with baseline values; however, patients in clonidine group had significantly lower HR compared with placebo (*P<0.05). In both groups, MAP fell significantly below baseline 1 minute after start of infiltration. It recovered in the clonidine group after 2.5 minutes but not in the placebo group where it continued to remain low even at 5 minutes. MAP in the placebo group was also significantly lower compared with the clonidine group from 2.5 minutes to 5 minutes.

CONCLUSION

In conclusion, oral clonidine 3 microg/kg administered 90 minutes before induction of anesthesia attenuates the fall in MAP due to scalp infiltration with a dilute concentration of epinephrine-lidocaine solution in patients undergoing craniotomy under isoflurane anesthesia.

Alpha-2 adrenergic agonists for the prevention of cardiac complications among patients undergoing surgery

BACKGROUND

The surgical stress response plays an important role on the pathogenesis of perioperative cardiac complications. Alpha-2 adrenergic agonists attenuate this response and may thereby prevent cardiac complications.

OBJECTIVES

This review assessed the efficacy and safety of preoperative (within 24 hours), intraoperative, and postoperative (first 48 hours) alpha-2 adrenergic agonists for preventing mortality and cardiac complications after surgery performed under either general or neuraxial anaesthesia, or both.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2008, Issue 3), MEDLINE (1950 to August week 4 2008), EMBASE (1980 to week 36 2008), the Science Citation Index, and reference lists of articles.

SELECTION CRITERIA

We included randomized controlled trials that compared alpha-2 adrenergic agonists (clonidine, dexmedetomidine, or mivazerol) against placebo or non-alpha-2 adrenergic agonists. Included studies had to report on mortality, myocardial infarction, myocardial ischaemia, or supraventricular tachyarrhythmia.

DATA COLLECTION AND ANALYSIS

Three authors independently assessed trial quality and extracted data. Two authors independently performed computer entry of abstracted data. We contacted study authors for additional information. Adverse event data were gathered from the trials.

MAIN RESULTS

We included 31 studies (4578 participants). Study quality was generally inadequate, with only six studies clearly reporting methods for blinding and allocation concealment. Overall, alpha-2 adrenergic agonists reduced mortality (relative risk (RR) 0.66; 95% CI 0.44 to 0.98; P = 0.04) and myocardial ischaemia (RR 0.68; 95% CI 0.57 to 0.81; P < 0.0001). However, their effects appeared to vary with the surgical procedure. The most encouraging data pertained to vascular surgery, where they reduced mortality (RR 0.47; 95% CI 0.25 to 0.90; P = 0.02), cardiac mortality (RR 0.36; 95% CI 0.16 to 0.79; P = 0.01), and myocardial infarction (RR 0.66; 95% CI 0.46 to 0.94; P = 0.02). With regard to adverse effects, alpha-2 adrenergic agonists significantly increased perioperative hypotension (RR 1.32; 95% CI 1.07 to 1.62; P = 0.009) and bradycardia (RR 1.66; 95% CI 1.14 to 2.41; P = 0.008).

AUTHORS' CONCLUSIONS

Our study provides encouraging evidence that alpha-2 adrenergic agonists may reduce cardiac risk, especially during vascular surgery. Nonetheless, these data remain insufficient to make firm conclusions about their efficacy and safety. A large randomized trial of alpha-2 adrenergic agonists is therefore warranted. Additionally, future research must determine which specific alpha-2 adrenergic agonist should be used, and whether it is safe to combine them with other perioperative interventions (for example beta-adrenergic blockade).

Advances in and limitations of up-and-down methodology: a précis of clinical use, study design, and dose estimation in anesthesia research

Sequential design methods for binary response variables exist for determination of the concentration or dose associated with the 50% point along the dose-response curve; the up-and-down method of Dixon and Mood is now commonly used in anesthesia research. There have been important developments in statistical methods that (1) allow the design of experiments for the measurement of the response at any point (quantile) along the dose-response curve, (2) demonstrate the risk of certain statistical methods commonly used in literature reports, (3) allow the estimation of the concentration or dose-the target dose-associated with the chosen quantile without the assumption of the symmetry of the tolerance distribution, and (4) set bounds on the probability of response at this target dose. This article details these developments, briefly surveys current use of the up-and-down method in anesthesia research, reanalyzes published reports using the up-and-down method for the study of the epidural relief of pain during labor, and discusses appropriate inferences from up-and-down method studies.

Clonidine and modification of perioperative outcome

PURPOSE OF REVIEW

Perioperative cardiac risk reduction using perioperative beta-blockade is being widely adopted. Recent research has identified a second-line agent, perioperative clonidine, that can be used to reduce the risk of perioperative cardiac mortality. Perioperative clonidine has some advantages over perioperative beta-blockers because it has less risk of bronchospasm in asthmatics and it comes in a transcutaneous form that can be used in patients who are not taking oral medications ('NPO').

RECENT FINDINGS

Clonidine has been used for many purposes, including reduction of blood pressure in hypertension, reduction in alcohol and drug withdrawal phenomena, reduction in nicotine withdrawal symptoms during smoking cessation, analgesia, reduction in stress response, and now as an anti-ischemic agent to reduce the risk of perioperative myocardial ischemia and perioperative mortality.

SUMMARY

Administration of perioperative clonidine can reduce the risk of perioperative myocardial ischemia and mortality in patients undergoing non-cardiac surgery. Perioperative clonidine comes in a patch form that can be used in patients who are not taking medications by mouth, and can be used when beta-blockers are contraindicated (for asthmatics or patients with high-grade atrioventricular block).

Postoperative pain, nausea and vomiting in neurosurgical patients

PURPOSE OF REVIEW

Postoperative pain and postoperative nausea and vomiting are significant problems for neurosurgical patients and their carers. The treatment of these problems is widely perceived to be inadequate, however, especially in patients undergoing craniotomy, and there are few large, randomized controlled trials. The main issue has been fear of side effects, especially those masking neurological signs. A review of the recent literature therefore is justified.

RECENT FINDINGS

Very little new information has been added to the literature about pain management in craniotomy patients, and postoperative nausea and vomiting management in neurosurgery patients as a whole. The main themes in the literature have been the introduction of multimodal analgesia for craniotomy patients, using simple analgesics as adjuvants to opioids, and innovative neuroaxial analgesia techniques in spinal surgery patients.

SUMMARY

There is still a lot of scope to research and refine pain and postoperative nausea and vomiting management in cranial and spinal neurosurgical patients. Large-scale studies are required to define the current state of practice, determine effective treatments and define the incidence of side-effects.