Clonidine decreases vasoconstriction and shivering thresholds, without affecting the sweating threshold

Temperature control after cardiac arrest

Managing temperature is an important part of post-cardiac arrest care. Fever or hyperthermia during the first few days after cardiac arrest is associated with worse outcomes in many studies. Clinical data have not determined any target temperature or duration of temperature management that clearly improves patient outcomes. Current guidelines and recent reviews recommend controlling temperature to prevent hyperthermia. Higher temperatures can lead to secondary brain injury by increasing seizures, brain edema and metabolic demand. Some data suggest that targeting temperature below normal could benefit select patients where this pathology is common. Clinical temperature management should address the physiology of heat balance. Core temperature reflects the heat content of the head and torso, and changes in core temperature result from changes in the balance of heat production and heat loss. Clinical management of patients after cardiac arrest should include measurement of core temperature at accurate sites and monitoring signs of heat production including shivering. Multiple methods can increase or decrease heat loss, including external and internal devices. Heat loss can trigger compensatory reflexes that increase stress and metabolic demand. Therefore, any active temperature management should include specific pharmacotherapy or other interventions to control thermogenesis, especially shivering. More research is required to determine whether individualized temperature management can improve outcomes.

Perioperative Hypothermia-A Narrative Review

Unintentional hypothermia (core temperature < 36 °C) is a common side effect in patients undergoing surgery. Several patient-centred and external factors, e.g., drugs, comorbidities, trauma, environmental temperature, type of anaesthesia, as well as extent and duration of surgery, influence core temperature. Perioperative hypothermia has negative effects on coagulation, blood loss and transfusion requirements, metabolization of drugs, surgical site infections, and discharge from the post-anaesthesia care unit. Therefore, active temperature management is required in the pre-, intra-, and postoperative period to diminish the risks of perioperative hypothermia. Temperature measurement should be done with accurate and continuous probes. Perioperative temperature management includes a bundle of warming tools adapted to individual needs and local circumstances. Warming blankets and mattresses as well as the administration of properly warmed infusions via dedicated devices are important for this purpose. Temperature management should follow checklists and be individualized to the patient's requirements and the local possibilities.

Premedication with clonidine versus fentanyl for intraoperative hemodynamic stability and recovery outcome during laparoscopic cholecystectomy under general anesthesia

BACKGROUND

Laparoscopic cholecystectomy under general anesthesia induced intraoperative hemodynamic responses which should be attenuated by appropriate premedication. The present study was aimed to compare the clinical efficacy of clonidine and fentanyl premedication during laparoscopic cholecystectomy for attenuation of hemodynamic responses with postoperative recovery outcome.

SUBJECTS AND METHODS

In this prospective randomized double blind study 64 adult consented patients of either sex with ASA I and II, scheduled for elective laparoscopic cholecystectomy under general anesthesia and met the inclusion criteria, were allocated into two groups of 32 patients. Group C patients have received intravenous clonidine 1μg kg(-1) and Group F patients have received intravenous fentanyl 2μg kg(-1) 5 min before induction. Anesthetic and surgical techniques were standardized. All patients were assessed for intraoperative hemodynamic changes at specific time and postoperative recovery outcome.

RESULTS

Premedication with clonidine or fentanyl has attenuated the hemodynamic responses of laryngoscopy and laparoscopy. Clonidine was superior to fentanyl for intraoperative hemodynamic stability. No significant differences in the postoperative recovery outcome were observed between the groups. Nausea, vomiting, shivering and respiratory depression were comparable between groups.

CONCLUSION

Premedication with clonidine or fentanyl has effectively attenuated the intraoperative hemodynamic responses of laparoscopic cholecystectomy.

Hemodynamic stress response during laparoscopic cholecystectomy: Effect of two different doses of intravenous clonidine premedication

Background:

Clonidine has emerged as an attractive premedication desirable in laparoscopic surgery wherein significant hemodynamic stress response is seen. The minimum safe and effective dose of intravenous clonidine to attenuate the hemodynamic stress response during laparoscopic surgery has however not yet been determined.

Materials and Methods:

This prospective, randomized, double-blind controlled study was conducted on 90 adults of ASA physical status I and II, scheduled for laparoscopic cholecystectomy under general anesthesia. Patients were randomized to one of the three groups (n= 30). Group I received 100 ml of normal saline, while groups II and III received 1 μg/ kg and 2 μg/ kg of clonidine respectively, intravenous, in 100 ml of normal saline along. All patients received glycopyrrolate 0.004 mg/kg and tramadol 1.5 mg/kg intravenously, 30 min before induction. Hemodynamic variables (heart rate, systolic, diastolic, mean arterial pressure), SpO2, and sedation score were recorded at specific timings. MAP above 20% from baseline was considered significant and treated with nitroglycerine.

Results:

In group I, there was a significant increase in hemodynamic variables during intubation pneumoperitoneum and extubation (P<0.001). Clonidine given 1 μg/kg intravenous attenuated hemodynamic stress response to pneumoperitoneum (P<0.05), but not that associated with intubation and extubation. Clonidine 2 μg/kg intravenous prevented hemodynamic stress response to pneumoperitoneum and that associated with intubation and extubation (P<0.05). As against 14 and 2 patients in groups I and II respectively, no patient required nitroglycerine infusion in group III.

Conclusions:

Clonidine, 2 μg/ kg intravenously, 30 min before induction is safe and effective in preventing the hemodynamic stress response during laparoscopic cholecystectomy.

Oral premedication with pregabalin or clonidine for hemodynamic stability during laryngoscopy and laparoscopic cholecystectomy: A comparative evaluation

BACKGROUND

Hemodynamic responses of laryngoscopy and laparoscopy should be attenuated by the appropriate premedication, smooth induction, and rapid intubation. The present study evaluated the clinical efficacy of oral premedication with pregabalin or clonidine for hemodynamic stability during laryngoscopy and laparoscopic cholecystectomy.

METHODS

A total of 180 healthy adult consented patients aged 35 to 52 years with American Society of Anesthesiologist (ASA) physical status I and II of both gender, who met the inclusion criteria for elective laparoscopic cholecystectomy, were randomized to receive placebo Group I, pregabalin (150 mg) Group II, or clonidine (200 μg) Group III, given 75 to 90 minutes before surgery as oral premedication. All groups were compared for preoperative sedation and anxiety level along with changes of heart rate and mean arterial pressure prior to premedication, before induction, after laryngoscopy, pneumoperitoneum, release of carbon dioxide, and extubation. Intraoperative analgesic drug requirement and any postoperative complications were also recorded.

RESULTS

Pregabalin and clonidine proved to have sedative and anxiolytic effects as oral premedicants and decreased the need of intraoperative analgesic drug requirement. Clonidine was superior to pregabalin for attenuation of the hemodynamic responses to laryngoscopy and laparoscopy, but it increased the incidence of intra-and postoperative bradycardia. No significant differences in the parameters of recovery were observed between the groups. None of the premedicated patient has suffered from any postoperative side effects.

CONCLUSION

Oral premedication with pregabalin 150 mg or clonidine 200 μg causes sedation and anxiolysis with hemodynamic stability during laryngoscopy and laparoscopic cholecystectomy, without prolongation of recovery time and side effects.

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.

The therapeutic effect of modified Yu Ping Feng San on idiopathic sweating in end-stage cancer patients during hospice care

End-stage cancer patients frequently suffer from idiopathic sweating of unknown cause. This study was to evaluate the effect (primary endpoint) of modified Yu Ping Feng San on idiopathic sweating and adverse reactions (secondary endpoint). Thirty two end-stage cancer patients receiving hospice care, with exclusion criteria including sweating due to known causes and taking drugs which may affect the sweating threshold were enrolled. Patients received modified Yu Ping Feng San for 10 consecutive days. The quantitative measurement of sweating showed 26 patients (81.3%) had complete remission of sweating, and the average time required to reach 50% reduction was 4.6 days. The visual analog scale (VAS) sweating score estimated by patients and care-givers showed that the mean reductions were 8.4 and 9.1 points, respectively. An increase in appetite was experienced by 65.6% of patients, after administration of modified Yu Ping Feng San. The most prevalent treatment-related complications were nausea (15.6%), diarrhea (9.3%) and allergy (3.1%) without severity greater than grade 2, and these were reversible after cessation of treatment. These results suggest that modified Yu Ping Feng San is a safe and effective treatment for idiopathic sweating of unknown cause in end-stage cancer patients.

Thermoregulatory management for mild therapeutic hypothermia

In recent years the use of mild therapeutic hypothermia as a means of neuroprotection has become an important concept for treatment after cerebral ischemic hypoxic injury. Mild therapeutic hypothermia has been shown to improve outcome after out-of-hospital cardiac arrest, and many studies suggest a beneficial effect of mild therapeutic hypothermia on patient outcome after traumatic brain injury, cerebrovascular damage and neonatal asphyxia. This review article explores the numerous possibilities and methods for the induction of mild therapeutic hypothermia, reviews thermoregulatory management during maintenance and discusses associated risks and complications.

Practical pharmacologic aspects of therapeutic hypothermia after cardiac arrest

Abstract Therapeutic hypothermia has emerged as an effective means of improving neurologic outcomes among cardiac arrest survivors. To achieve optimal results, clinicians must understand and anticipate potential adverse effects of cooling and provide rigorous monitoring and/or pharmacologic interventions as appropriate. Using pharmacotherapy to counter adverse effects of cooling or to treat an intrinsic process under hypothermic conditions requires understanding how hypothermia will influence the clinical effects of the drug, including the drug's pharmacokinetics and pharmacodynamics. The pharmacologic aspects of therapeutic hypothermia in relation to physiology and adverse effects are reviewed.

Progress in shivering control

Hypothermia is a potent neuroprotectant and induced hypothermia holds great promise as a therapy for acute neuronal injury. Thermoregulatory responses, most notably shivering, present major obstacles to therapeutic temperature management. A review of thermoregulatory physiology and strategies aimed at controlling physiologic responses to hypothermia is presented.

Intraoperative Clonidine Administration to Neurosurgical Patients

The goals of this two-part study were to determine the dose of clonidine to prevent postoperative shivering after mild hypothermia and to evaluate the effect of clonidine on recovery from anesthesia in patients undergoing surgery for intracranial lesions. We enrolled 48 patients undergoing elective supratentorial neurosurgical procedures into one of two studies. In study 1 (n=14) we determined the ED50 of clonidine to prevent postoperative shivering after mild hypothermia (35 degrees C) using Dixon's up-and-down method. Clonidine dose for the first study patient was 3 microg/kg. The dose was then adjusted in 1-microg/kg increments for the following patients. Shivering was assessed for 1 h postoperatively. Study 2 (n=34) was a prospective, randomized, double-blind, placebo controlled study to evaluate the effect of 3 microg/kg clonidine on recovery from anesthesia. At the beginning of dural closure, patients randomly received a 15-min infusion of either clonidine or normal saline. Recovery variables were studied for 2 h after the end of anesthesia. The ED50 of clonidine to prevent shivering was 1.1 +/- 1.5 microg/kg in neurosurgical patients whose target core temperature was 35 degrees C at the end of surgery. Compared with saline, 3 microg/kg of clonidine administered to neurosurgical patients 1 h before the end of anesthesia did not delay emergence from anesthesia nor did it have clinically significant sedative or hemodynamic effects. Our results imply that clonidine may be used in neurosurgical patients to prevent postoperative shivering after mild hypothermia.

The Effect of Meperidine on Thermoregulation in Mice: Involvement of ??2-Adrenoceptors

Meperidine has potent antishivering properties. The underlying mechanisms are not fully elucidated, but recent investigations suggest that alpha2-adrenoceptors are likely to be involved. We performed the current study to investigate the effects of meperidine on nonshivering thermogenesis in a model of thermoregulation in mice. After injection (0.1 mL/kg intraperitoneally) of saline, meperidine (20 mg/kg), the specific alpha2-adrenoceptor antagonist atipamezole (2 mg/kg), plus saline or atipamezole plus meperidine, respectively, mice were positioned in a Plexiglas chamber. Rectal temperature and mixed expired carbon dioxide were measured after provoking thermoregulatory effects by whole body cooling. Maximum response intensity of nonshivering thermogenesis and the thermoregulatory threshold for nonshivering thermogenesis, which was defined as the temperature at which a sustained increase in expiratory carbon dioxide can be measured, were investigated. Meperidine significantly decreased the threshold of nonshivering thermogenesis (36.6 degrees C +/- 0.7 degrees C) versus saline (37.9 degrees C +/- 0.6 degrees C) and versus atipamezole plus saline (37.8 degrees C +/- 0.4 degrees C; P <0.01). This effect was abolished after administration of meperidine combined with atipamezole (37.7 degrees C +/- 0.6 degrees C; P <0.05). Meperidine did not decrease the maximum intensity of nonshivering thermogenesis. The results suggest a major role of alpha2-adrenoceptors in the inhibition of thermoregulation by meperidine in mice.

Single-Dose Parenteral Pharmacological Interventions for the Prevention of Postoperative Shivering: A Quantitative Systematic Review of Randomized Controlled Trials

Shivering is a frequent complication in the postoperative period. The relative efficacy of pharmacological interventions to prevent this phenomenon is not well understood. We performed a systematic search for full reports of randomized comparisons of prophylactic, parenteral, single-dose antishivering interventions with inactive control (placebo or no treatment). Variable doses were converted to fixed doses. Dichotomous data on the absence of shivering were analyzed by using relative benefit (RB) and number needed to treat (NNT) with 95% confidence intervals (CI). Data from 27 trials (1348 adults received an antishivering intervention; 931 were controls) were analyzed. The average incidence of shivering in controls was extremely frequent (52%). Clonidine 65-300 microg (1078 patients), meperidine 12.5-35 mg (250 patients), tramadol 35-220 mg (250 patients), and nefopam 6.5-11 mg (204 patients) were tested in at least 3 trials each. All were more effective than control. For clonidine, meperidine, and nefopam, there was some weak evidence of dose responsiveness. For small-dose clonidine (65-110 microg), the RB compared with control was 1.32 (95% CI, 1.16-1.51); for medium-dose clonidine (140-150 microg), the RB was 1.83 (95% CI, 1.47-2.27); and for large-dose clonidine (220-300 microg), the RB was 1.52 (95% CI, 1.30-1.78). For all clonidine regimens combined, the RB was 1.58 (95% CI, 1.43-1.74), with an NNT of 3.7. For all meperidine regimens combined, the RB was 1.67 (95% CI, 1.37-2.03), with an NNT of 3. For all tramadol regimens combined, the RB was 1.93 (95% CI, 1.56-2.39), with an NNT of 2.2. For all nefopam regimens combined, the RB was 2.62 (95% CI, 2.02-3.40), with an NNT of 1.7. Methylphenidate, midazolam, dolasetron, ondansetron, physostigmine, urapidil, and flumazenil were tested in no more than 3 trials each, with a limited number of patients.

Nefopam, a nonsedative benzoxazocine analgesic, selectively reduces the shivering threshold in unanesthetized subjects

BACKGROUND

The analgesic nefopam does not compromise ventilation, is minimally sedating, and is effective as a treatment for postoperative shivering. The authors evaluated the effects of nefopam on the major thermoregulatory responses in humans: sweating, vasoconstriction, and shivering.

METHODS

Nine volunteers were studied on three randomly assigned days: (1) control (saline), (2) nefopam at a target plasma concentration of 35 ng/ml (low dose), and (3) nefopam at a target concentration of 70 ng/ml (high dose, approximately 20 mg total). Each day, skin and core temperatures were increased to provoke sweating and then reduced to elicit peripheral vasoconstriction and shivering. The authors determined the thresholds (triggering core temperature at a designated skin temperature of 34 degrees C) by mathematically compensating for changes in skin temperature using the established linear cutaneous contributions to control of each response.

RESULTS

Nefopam did not significantly modify the slopes for sweating (0.0 +/- 4.9 degrees C. microg-1. ml; r2 = 0.73 +/- 0.32) or vasoconstriction (-3.6 +/- 5.0 degrees C. microg-1. ml; r2 = -0.47 +/- 0.41). In contrast, nefopam significantly reduced the slope of shivering (-16.8 +/- 9.3 degrees C. microg-1. ml; r2 = 0.92 +/- 0.06). Therefore, high-dose nefopam reduced the shivering threshold by 0.9 +/- 0.4 degrees C (P < 0.001) without any discernible effect on the sweating or vasoconstriction thresholds.

CONCLUSIONS

Most drugs with thermoregulatory actions-including anesthetics, sedatives, and opioids-synchronously reduce the vasoconstriction and shivering thresholds. However, nefopam reduced only the shivering threshold. This pattern has not previously been reported for a centrally acting drug. That pharmacologic modulations of vasoconstriction and shivering can be separated is of clinical and physiologic interest.

Postanaesthetic shivering: epidemiology, pathophysiology, and approaches to prevention and management

Along with nausea and vomiting, postanaesthetic shivering is one of the leading causes of discomfort for patients recovering from general anaesthesia. The distinguishing factor during electromyogram recordings between patients with postanaesthetic shivering and shivering in fully awake patients is the existence of clonus similar to that recorded in patients with spinal cord transection. Clonus coexists with the classic waxing and waning signals associated with cutaneous vasoconstriction (thermoregulatory shivering). The primary cause of postanaesthetic shivering is peroperative hypothermia, which sets in because of anaesthetic-induced inhibition of thermoregulation. However, shivering associated with cutaneous vasodilatation (non-thermoregulatory shivering) also occurs, one of the origins of which is postoperative pain. Apart from causing discomfort and aggravation of pain, postanaesthetic shivering increases metabolic demand proportionally to the solicited muscle mass and the cardiac capacity of the patient. No link has been demonstrated between the occurrence of shivering and an increase in cardiac morbidity, but it is preferable to avoid postanaesthetic shivering because it is oxygen draining. Prevention mainly entails preventing peroperative hypothermia by actively rewarming the patient. Postoperative skin surface rewarming is a rapid way of obtaining the threshold shivering temperature while raising the skin temperature and improving the comfort of the patient. However, it is less efficient than certain drugs such as meperidine, clonidine or tramadol, which act by reducing the shivering threshold temperature.

Minimizing perioperative adverse events in the elderly

Elderly patients still have the highest postoperative mortality and morbidity rate in the adult surgical population. Preoperative clinical assessment to detect patients at high risk of postoperative events, and specific intraoperative and postoperative anaesthesia management are important to minimize postoperative adverse events in the elderly.

Inhibition of shivering increases core temperature afterdrop and attenuates rewarming in hypothermic humans

During severe hypothermia, shivering is absent. To simulate severe hypothermia, shivering in eight mildly hypothermic subjects was inhibited with meperidine (1.5 mg/kg). Subjects were cooled twice (meperidine and control trials) in 8 degrees C water to a core temperature of 35.9 +/- 0.5 (SD) degrees C, dried, and then placed in sleeping bags. Meperidine caused a 3.2-fold increase in core temperature afterdrop (1.1 +/- 0.6 vs. 0.4 +/- 0.2 degree C), a 4.3-fold increase in afterdrop duration (89.4 +/- 31.4 vs. 20.9 +/- 5.7 min), and a 37% decrease in rewarming rate (1.2 +/- 0.5 vs. 1.9 +/- 0.9 degrees C/h). Meperidine inhibited overt shivering. Oxygen consumption, minute ventilation, and heart rate decreased after meperidine injection but subsequently returned toward preinjection values after 45 min postimmersion. This was likely due to the increased thermoregulatory drive with the greater afterdrop and the short half-life of meperidine. These results demonstrate the effectiveness of shivering heat production in attenuating the postcooling afterdrop of core temperature and potentiating core rewarming. The meperidine protocol may be valuable for comparing the efficacy of various hypothermia rewarming methods in the absence of shivering.