Tables 4 and 5 show the results from the logistic regression analysis pertaining to overall and respiratory-specific morbidity. Preexisting
respiratory disease and anesthesia type (general) were significant predictors of morbidity (P < 0.05 for both). Unsurprisingly, preexisting respiratory disease was a significant risk factor for postoperative respiratory morbidity, as was general anesthesia (P < 0.05 for both, Table 5).
CHAPTER FOUR
DISCUSSION
4.1 Neuraxial versus general anaesthesia
When reviewing this question, any analysis , meta-analysis or systemic review is made difficult , by the heterogeneity of the patient population and of the treatment themselves. In some studies, neuraxial anaesthesia is used in conjunction with general anesthesia, in others not.
Sole neuraxial anaesthesia is commonly used for extremity, body surface surgery, and non-extensive intraabdominal and pelvic procedures,
whereas adjunctive neuraxial anaesthesia is more commonly used for major intraabdominal and intrathoracic procedures and for postoperative analgesia. The dense sympathetic blockade provided by intraoperative neuraxial anaesthesia results in improved lowere extremity blood flow, lesser incidence of hypercoagulability, and reduced cardiac work. Hence , the incidence of deep venous thrombosis, pulmonary embolism, and cardiac events may be reduced.
A meta-analysis published by Rodgers et al in 200016strongly supported a reduction in mortality associated with use of neuraxial
anaesthesia. Their overall conclusion was that neuraxial anaesthesia reduced postoperative mortality by about one third. The authors
recommended more widespread use of neuraxial anaesthesia. Yet they drew this conclusion from a meta-analysis that included various patients populations using different anaesthesia techniques and undergoing differents surgical procedures. They included studies of spinal and
epidural anaesthesia, thoracic or lumbar catheter placement, regardless of whether spinal or epidural anaesthesia was used in combination with general anesthesia or not. Their subgroup analysis show, that significant reduction in mortality occurred only in specific patient populations seemed to do better in older studies, with no difference shown by newer studies. Therefore , applying their overall conclusion to eery patients can be misleading. Benefit versus risk seeseement should always be
population and practice specific.
4.2 Mortality and morbidity of modern anesthesia
Several recent reports, with various end points, indicated that the method of anesthesia did not influence morbidity or mortality following surgery.2-6 In 2006, a systematic review12 comparing mortality and
morbidity after hip fracture surgery conducted under either regional or general anesthesia showed that regional anesthesia significantly reduced one-month mortality, deep venous thrombosis, blood loss, and postoperative confusion. However, when the oldest trial (with high mortality) was excluded, the difference in one-month mortality was no longer significant. In newer studies,10,11 after modern thromboprophylaxis was used, the protective effect of regional anesthesia against thromboembolic events become less obvious. Improvements in perioperative management have increased the safety of operative procedures to the extent that any benefit attributable to anesthetic intervention is no longer obvious.10,11 Therefore, even large trials may not have enough power to detect differences of outcome between regional and general anesthesia.4,6
4.3 The choice of anesthetic type in aged patients
In a large trial by O'Hara and colleagues(6206 patients), which found no difference in outcome between general and spinal anesthesia, the patient age was 60 years or older.6 The same result was seen by Koval,2 when the patient age was 65 years or older. In contrast, our study focused
on patients more than 80 years old. Such elderly patients typically have a higher incidence of existing medical problems and a reduced capacity for physiologic compensation.5 Hence, any influence—even a slight one—of anesthesia method on recovery would likely be exacerbated in such individuals. That likely explains why our results showed the difference of morbidity between two type of anesthesia techniques, where other studies could not.
4.4 Surgery duration and intraoperative blood loss
We found that surgery duration and intraoperative blood loss were significantly decreased in spinal anesthesia patients. These findings are consistent with those from other studies,12,15 and may in part explain the decreased morbidity in the spinal anesthesia group.
4.5 Difference of patients characters
In our series, the incidences of pre-existing hypertension and diabetes mellitus were higher in general anesthesia patients but the age was older in spinal anesthesia patients. Evidently, patient characteristics and
underlying disease may have influenced the method of anesthesia employed by the anesthesiologist.
4.6 Risk factors of morbidity
Logistic regression analysis revealed that anesthesia type and a history of respiratory disease were significant predictors of both overall and respiratory-specific postoperative morbidity. Preexisting respiratory disease obviously should predict postoperative respiratory complications;
however, it is interesting that anesthesia type also affected respiratory morbidity. The increased respiratory morbidity in general anesthesia patients, as opposed to spinal anesthesia patients, may be related to the endotracheal intubation required for general anesthesia. Indeed, it has been reported that a relatively high percentage of patients who receive intubation/mechanical ventilation suffer associated respiratory complications, namely pneumonia.13 Adverse pulmonary outcomes after anesthesia and surgery are often attributed to anesthesia care.
Perioperative pulmonary complications are a significant concern for anesthesia caregivers, because anesthesiology drugs and techniques can
temporarily decrease lung volume, impair airway reflexes, limit immune function, and depress secretion mobilization.14
4.7 Ventilator associated pneumonia
The pneumonia associated with general anesthesia can be aimed as a ventilator associated pneumonia. Intubation and mechanical ventilation is associated with 7- 21 fold increase in the incidence of pneumonia and up to 28% patients receiving mechanical ventilation develop pneumonia. Most case result from aspiration of pathogen colonies in oropharyngeal airway. In healthy adult , the normal cough reflex, the normal immune response may protect them from developing pneumonia. But in very old patients, any pathogen colonies aspirate into airway during general anesthesia may develop pneumonia due to poor cough reflex and immune response. This may partially explain why the respiratory-related morbidity greatly increased in general anesthesia patients in very old patients .
4.8 Limitation of this study
This study had several limitations. Firstly, the surgical complexity (type of fracture) was not evaluated. This may have impacted the operation duration and blood loss. A second limitation was the small sample size. Although we excluded some postoperative complications that theoretically should not be related to anesthesia, such as wound infection and urinary tract infections, several of the included complications may not have been directly related to the anesthesia method. Furthermore, this is a retrospective study; the patient characteristics could not be controlled, which may have impacted the outcome. Further studies with larger patient populations and more detailed analysis of postoperative complications are warranted.
4.9 Summary
Our findings suggest that general anesthesia during hip fracture repair increases the risk of overall and respiratory-specific postoperative complications in elderly patients. To our knowledge no definitive studies have yet indicated that general anesthesia confers benefits over spinal anesthesia in elderly patients undergoing hip fracture repair. Therefore,
taken together with our and other findings, it would appear that the use of spinal anesthesia in such elderly patients may be the safer option.
CHAPTER FIVE
REFERENCES
(1) Parker M, Johansen A. Hip fracture. BMJ 2006;333:27-30.
(2) Koval KJ, Aharonoff GB, Rosenberg AD, Schmigelski C, Bernstein RL, Zuckerman JD. Hip fracture in the elderly: the effect of anesthetic technique. Orthopedics 1999;22:31-34.
(3) Sutcliffe AJ, Parker M. Mortality after spinal and general anaesthesia for surgical fixation of hip fractures. Anaesthesia 1994;49:237-240.
(4) Gilbert TB, Hawkes WG, Hebel JR, et al. Spinal anesthesia versus general anesthesia for hip fracture repair: a longitudinal observation of 741 elderly patients during 2-year follow-up. Am J Orthop 2000;29:25-35.
(5) Covert CR, Fox GS. Anaesthesia for hip surgery in the elderly. Can J Anaesth 1989;36:311-319.
(6) O'Hara DA, Duff A, Berlin JA, et al. The effect of anesthetic technique on postoperative outcomes in hip fracture repair.
Anesthesiology 2000;92:947-957.
(7) Urwin SC, Parker MJ, Griffiths R. General versus regional anaesthesia for hip fracture surgery: a meta-analysis of randomized trials. Br J Anaesth 2000;84:450-455.
(8) Mauermann WJ, Shilling AM, Zuo Z. A comparison of neuraxial block versus general anesthesia for elective total hip replacement: a meta-analysis. Anesth Analg 2006;103:1018-1025.
(9) Rodgers A, Walker N, Schug S, et al. Reduction of postoperative mortality and morbidity with epidural or spinal anaesthesia: results from overview of randomised trials. BMJ 2000;321:1493-1497.
(10) Gulur P, Nishimori M, Ballantyne JC. Regional anaesthesia versus general anaesthesia, morbidity and mortality Best Prac Clin Anaesth 2006;20:249-263
(11) Bajaj, P. Regional anesthesia versus general anesthesia: Is there an impact on outcome after major surgery? Indian J Anaesth 2005;51:153-154
(12) Parker MJ, Hondoll HH, Griffiths R. Anaesthesia for hip fracture surgery in adults. Cochrane Database Syst Rev 2004;4:CD000521 (13) Hunter JD. Ventilator associated pneumonia. Postgrad Med J
2006;82:172-178.
(14) Watson CB. Respiratory complications associated with anesthesia Anesthesiology Clin N Am 2002;20:513-537
(15) Twyman R, Kirwan T, Fennelly M. Blood loss reduced during hip arthroplasty by lumbar plexus block. J Bone Joint Surg Br 1990;72:770-771.
(16) Rodgers A, Walker N, Schug S et al. Reduction of postoperative mrotality and morbidity with epidural or spinal anaesthesia :results from overview of randomised trials. Br Med J 2000 ; 321(7275):1493
Table 1. General and spinal anesthesia group preoperative
Age (years) 83.96±3.71 84.93±4.04 0.02*
Gender
ASA classifications: American Society of Anesthesiologists physical classification
Class 1 = Healthy patient, no medical problems; Class 2 = Mild systemic disease; Class 3 = Severe systemic disease, but not
incapacitating; Class 4 = Severe systemic disease that is a constant threat to life; Class 5 = Moribund, not expected to live 24 hours irrespective of operation
* Statistically significant, P < 0.05.
† Mann-Whitney-U test for continuous variable, and Chi-square test or Fisher’s exact test for categorical variables.
Table 2. Intraoperative and postoperative variables in the general and spinal anesthesia groups.
Variable
Operation duration (minutes) 172.89±51.47 154.70±35.25 <0.01*
Blood loss (ml) 307.99±260.76 240.18±195.72 0.01*
Morbidity 21 (12.6%) 9 (5.4%) 0.02*
Morbidity, respiratory 11 (6.6%) 3 (1.8%) 0.03*
Mortality 5 (3.0%) 2 (1.2%) 0.25
Morbidity: pneumonia, delirium, cerebrovascular accident (CVA), gastrointestinal bleeding, chronic obstructive pulmonary disease (COPD) exacerbation, acute renal failure, cardiac event, pleural effusion and renal failure.
* Statistically significant, P < 0.05.
† Mann-Whitney-U test for continuous variable, and Chi-square test or Fisher’s exact test for categorical variables.
Table 3. Case numbers of postoperative complications
Postoperative complication General Anesthesia Spinal Anesthesia Total*
Pneumonia 9 3 12
Delirium 6 1 7
Gastrointestinal bleeding 4 3 7
Acute renal failure 2 1 3
Cardiac event 0 2 2
CVA/stroke 1 0 1
COPD acute exacerbation 1 0 1
Respiratory failure 1 0 1
* Total does not equal the number of patients with a postoperative complication because some patients had more than one complication.
Table 4. Results from logistic regression analysis of morbidity risk factors.
Variable Odds Ratio 95%
confidence interval.
P value
Age 1.06 0.97–1.17 0.211
Operation time 1.01 1.00–1.01 0.195
Hypertension 1.71 0.71–4.16 0.234
Heart disease 1.69 0.75–3.79 0.203
Respiratory disease 3.38 1.48–7.71 0.004*
Anesthesia type
Spinal 1
General 2.39 1.00–5.67 0.049*
* Statistically significant, P < 0.05.
Table 5. Results from logistic regression analysis of respiratory morbidity risk factors.
Variable Odds Ratio 95%
confidence interval
P value
Gender (Male) 2.42 0.63–9.27 0.199
Age 1.03 0.90–1.19 0.694
Respiratory disease 4.93 1.60–15.23 0.006*
Anesthesia type
Spinal 1
General 4.75 1.25–18.03 0.022*
* Statistically significant, P < 0.05.