الفهرس 
Literature ReviewOnly 14 pages are availabe for public view
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Abstract
Background:
Shivering is one of the common problems after spinal anesthesia with an incidence of up to 56.7%. Shivering is defined as an involuntary, repetitive activity of skeletal muscles.
The mechanisms of shivering in patients undergoing surgery are mainly intraoperative heat loss, increased sympathetic tone, pain, and systemic release of pyrogens.
Perioperative shivering not only increases the psychological stress response, but also leads to an increase in oxygen consumption (up to 400%)
Additionally, increased production of carbon dioxide results in accumulation of hypoxia and lactic acid in tissue. This then
affects the process of anesthesia and surgery, causing severe consequences for patients with poor cardiopulmonary function reserve.
At present, there are many clinical treatments available for patients to control shivering after spinal anesthesia, including non-pharmacological methods and pharmacological methods. Nonpharmacological methods using equipment to maintain a normal temperature of the body are
effective, but expensive. However, pharmacological methods using drugs, such as ketamine, magnesium sulphate and pethidine, are easier to carry out. Ketamine and magnesium sulphate have been tried among other pharmacological agents to reduce shivering during anesthesia with good results. Ketamine; a competitive NMDA receptor antagonist
has a role in thermoregulation at various levels. NMDA receptor modulates noradrenergic and serotoninergic neurons in locus ceruleus. It is used as an antishivering agent in the dose of 0.5-
0.75mg/kg. Meanwhile trials showed that there is sufficient data to conclude that intravenous magnesium reduces shivering in perioperative patients. The drug not only exerts a central effect, but is also a mild muscle relaxant and may thus simultaneously reduce the gain of shivering (incremental shivering intensity) with progressing hypothermia.
So, the current study was conducted to evaluate and compare the relative efficacy and safety of
low dose ketamine (0.5mg/kg) and magnesium sulphate (30 mg/kg) in prevention of shivering during/post spinal anesthesia.
Methods:
This study is a randomized clinical trial. Conducted in Ain Shams university hospitals. Seventy five American Society of Anesthesiologist physical status II and III patients undergoing diabetic foot debridement surgeries under spinal anesthesia were included.
After intrathecal injection, the patients were randomly divided to one of the 3 groups of 25 each according to the agent; group K (ketamine) received ketamine 0,5 mg/ kg. diluted in a 100 ml of normal saline and given over 15 minutes, prophylactically.
group M (Magnesium sulphate) received Magnesium sulphate 30 mg/kg. diluted in a 100 ml of normal saline and given over 15 minutes prophylactically
group P received a 100 ml bolus of physiological solution given over 15 minutes
Shivering was graded using Grada scale described by Crossley & Mahajan every five minutes
All IV fluids were given at room temperature, patients were adequately warmed and covered with the exception of surgery site, operating room temperature was kept at 22 Celsius.
When shivering of grade II or higher happens, Pethidine (0.5mg/kg) was
given as rescue medication and repeated within 10 minutes for a maximum dose of 1mg/kg.
Vital data and temperature (Via the axilla) will be recorded every five minutes. Side effects i.e. hypotension, nausea and vomiting, sedation and hallucinations were also recorded.
Cumulative doses of pethidine were noted for each patient and group.
Results
Regarding the demographic data (Age, sex, height, weight) there was no statistically significant difference among the three groups. Also the pre operative vital signs and medical history showed no difference that is statistically significant.
Both Ketamine and Magnesium sulphate showed better results in the control of shivering than the control group (p = 0.035).
There was was a statistically significant decrease in the incidence of shivering (grade II or higher) in both K group (12%) and M group (24%) compared to the incidence of 44% in the P group (p-value 0.035). No statistically significant difference between the M and K groups though.
The requirement for a rescue pethidine dose was also significantly decreased and the incidence of persistence of shivering after giving the max dose of 1 mg/kg pethidine (0% compared to 16%).
Time elapsed to the onset of shivering was significantly altered as well. The mean value for the time to onset in the K group (31.00 ± 3.61) and M group (27.67 ± 4.50 ) was significantly longer than the P group (18.91 ± 4.59). (p value = 0.000).
There was no statistically significant discrepancy between the K and M group though regarding the onset of shivering (p-value 0.305).
These results suggest that both Ketamine and Magnsium sulphate significantly reduce the incidence of shivering compared to the control group. And Also both delay the onset of shivering (if it occurs) by a considerable amount, as well as reduce the need for pethidine to resolve the shivering.
Ketamine showed more effect than magnesium sulphate in reducing the incidence and delaying the onset of shivering but not by a large enough margin to be considered of statistical significance.
Regarding the body temperature changes and hypothermia: Despite the fall in body temperature observed in all groups, the incidence of hypothermia among all groups was less than what was expected from previous studies results. The incidence of Hypothermia was 20% in the Ketamine group, compared to 28% in the Magnesium sulphate and Placeo group which is not statistically signifiant. That can be due to the minimal exposure nature of surgery accompanied by the low level of sensory and autonomic block as well as the short duration of the procedure. There was also no statistically significant difference between the three groups when comparing intra-operative body temperature. However, there was a more profound DROP in body temperature in the P group compared to the K and M groups, enough to be statistically significant. The K group showed a slight elevation at the 10 mins marked followed by a gradual decrease of temperature.
Comparing mean arterial blood pressure between the three groups in the intra-operative period revealed lower pressures in each group at the 10 minutes reading compared to its baseline values. However the decline was more evident in the M and P groups compared with the K group patients.
There were no statistically significant differences observed while comparing the M and P study groups with each other. However, the mean MAP values were statistically significantly higher in the K group at both the 10 and 20 minutes mark. And again at the 50 and 60 minutes mark.
Regarding hypotension there was significant decrease in its incidence among the K group (20%) compared to the M and P groups (52%) (p-value 0.30)
Regarding heart rate, intra-operative comparison revealed that while the K and P groups tended to have increased heart rate compared to the pre operative period, with an early spike up at the 10 minutes mark before gradually returning to pre-operative values while the M group showed more tendency towards Bradycardia. The initial increase in heart rate was more evident in the Ketamine group, which is expected due to its sympathomimetic nature. However, there was no statistically significant changes in the heart rate all through the intra-operative period while comparing the three study groups with each other.
Regarding the incidence of side effects: All patients were monitored for at least an hour for the incidence of side effects of hypotension, heart rate changes, hypothermia, nausea, vomiting, sedation and hallucination.
There was no statistically significant difference between the three groups regarding the incidence of Nausea, vomiting and heart rate changes (Tachycardia or Bradycardia). It is noted though that the ketamine group showed an increase of incidence of nausea and vomiting (40% and 16%) compared to the other two groups (18% and 8%).
Conclusion:
Both ketamine and Magnesium sulphate are effective agents in controlling shivering after spinal anesthesia. Ketamine has a probable protective effect against hypotension after spinal anesthesia.